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Sample records for extremely isolated globular

  1. Snapshot Survey of the Globular Cluster Populations of Isolated Early Type Galaxies

    Science.gov (United States)

    Gregg, Michael

    2017-08-01

    We propose WFC3/UVIS snapshot observations of a sample of 75 isolated early type galaxiesresiding in cosmic voids or extremely low density regions. The primary aim is to usetheir globular cluster populations to reconstruct their evolutionary history, revealingif, how, and why void ellipticals differ from cluster ellipticals. The galaxies span arange of luminosities, providing a varied sample for comparison with the well-documentedglobular cluster populations in denser environments. This proposed WFC3 study of isolatedearly type galaxies breaks new ground by targeting a sample which has thus far receivedlittle attention, and, significantly, this will be the first such study with HST.Characterizing early type galaxies in voids and their GC systems promises to increase ourunderstanding of galaxy formation and evolution of galaxies in general because isolatedobjects are the best approximation to a control sample that we have for understanding theinfluence of environment on formation and evolution. Whether these isolated objects turnout to be identical to or distinct from counterparts in other regions of the Universe,they will supply insight into the formation and evolution of all galaxies. Parallel ACSimaging will help to characterize the near field environments of the sample.

  2. THE PECULIAR CHEMICAL INVENTORY OF NGC 2419: AN EXTREME OUTER HALO 'GLOBULAR CLUSTER'

    International Nuclear Information System (INIS)

    Cohen, Judith G.; Kirby, Evan N.; Huang Wenjin

    2011-01-01

    NGC 2419 is a massive outer halo Galactic globular cluster (GC) whose stars have previously been shown to have somewhat peculiar abundance patterns. We have observed seven luminous giants that are members of NGC 2419 with Keck/HIRES at reasonable signal-to-noise ratio. One of these giants is very peculiar, with an extremely low [Mg/Fe] and high [K/Fe] but normal abundances of most other elements. The abundance pattern does not match the nucleosynthetic yields of any supernova model. The other six stars show abundance ratios typical of inner halo Galactic GCs, represented here by a sample of giants in the nearby GC M30. Although our measurements show that NGC 2419 is unusual in some respects, its bulk properties do not provide compelling evidence for a difference between inner and outer halo GCs.

  3. An Extremely Lithium-rich Bright Red Giant in the Globular Cluster M3

    Science.gov (United States)

    Kraft, Robert P.; Peterson, Ruth C.; Guhathakurta, Puragra; Sneden, Christopher; Fulbright, Jon P.; Langer, G. Edward

    1999-06-01

    We have serendipitously discovered an extremely lithium-rich star on the red giant branch of the globular cluster M3 (NGC 5272). An echelle spectrum obtained with the Keck I High-Resolution Echelle Spectrograph reveals a Li I λ6707 resonance doublet of 520 mÅ equivalent width, and our analysis places the star among the most Li-rich giants known: logε(Li)~=+3.0. We determine the elemental abundances of this star, IV-101, and three other cluster members of similar luminosity and color and conclude that IV-101 has abundance ratios typical of giants in M3 and M13 that have undergone significant mixing. We discuss mechanisms by which a low-mass star may be so enriched in Li, focusing on the mixing of material processed by the hydrogen-burning shell just below the convective envelope. While such enrichment could conceivably happen only rarely, it may in fact regularly occur during giant-branch evolution but be rarely detected because of rapid subsequent Li depletion. Based on observations obtained with the Keck I Telescope of the W. M. Keck Observatory, which is operated by the California Association for Research in Astronomy (CARA), Inc., on behalf of the University of California and the California Institute of Technology. This Letter is dedicated to the memory of our beloved colleague Ed Langer, who died after a brief illness on February 16, 1999. Ed brought a unique theoretical perspective to our globular cluster abundance studies. His career truly embodied the academic ideals of inspiration in both teaching and research. He made friends wherever he traveled, and was an inspiration to students. We will miss him greatly.

  4. The Peculiar Chemical Inventory of NGC 2419: An Extreme Outer Halo "Globular Cluster"

    Science.gov (United States)

    Cohen, Judith G.; Huang, Wenjin; Kirby, Evan N.

    2011-10-01

    NGC 2419 is a massive outer halo Galactic globular cluster (GC) whose stars have previously been shown to have somewhat peculiar abundance patterns. We have observed seven luminous giants that are members of NGC 2419 with Keck/HIRES at reasonable signal-to-noise ratio. One of these giants is very peculiar, with an extremely low [Mg/Fe] and high [K/Fe] but normal abundances of most other elements. The abundance pattern does not match the nucleosynthetic yields of any supernova model. The other six stars show abundance ratios typical of inner halo Galactic GCs, represented here by a sample of giants in the nearby GC M30. Although our measurements show that NGC 2419 is unusual in some respects, its bulk properties do not provide compelling evidence for a difference between inner and outer halo GCs. Based in part on observations obtained at the W. M. Keck Observatory, which is operated jointly by the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration.

  5. Isolation and characterization of extreme halophilic archaea

    International Nuclear Information System (INIS)

    Franze, Madlen; Cherkouk, Andrea

    2017-01-01

    Extreme halophilic archaea from the family Halobactereacea represent a dominant part of the microbial community present in saline soils as well as rock salts. By using a culture-dependent approach different Haloarchaea could be isolated and were phylogenetic analysed. Interestingly, isolates closely related to different Halobacterium spp. were found in both environments.

  6. Chromosomal rearrangements and protein globularity changes in Mycobacterium tuberculosis isolates from cerebrospinal fluid

    Directory of Open Access Journals (Sweden)

    Seow Hoon Saw

    2016-09-01

    Full Text Available Background Meningitis is a major cause of mortality in tuberculosis (TB. It is not clear what factors promote central nervous system invasion and pathology but it has been reported that certain strains of Mycobacterium tuberculosis (Mtb might have genetic traits associated with neurotropism. Methods In this study, we generated whole genome sequences of eight clinical strains of Mtb that were isolated from the cerebrospinal fluid (CSF of patients presenting with tuberculous meningitis (TBM in Malaysia, and compared them to the genomes of H37Rv and other respiratory Mtb genomes either downloaded from public databases or extracted from local sputum isolates. We aimed to find genomic features that might be distinctly different between CSF-derived and respiratory Mtb. Results Genome-wide comparisons revealed rearrangements (translocations, inversions, insertions and deletions and non-synonymous SNPs in our CSF-derived strains that were not observed in the respiratory Mtb genomes used for comparison. These rearranged segments were rich in genes for PE (proline-glutamate/PPE (proline-proline-glutamate, transcriptional and membrane proteins. Similarly, most of the ns SNPs common in CSF strains were noted in genes encoding PE/PPE proteins. Protein globularity differences were observed among mycobacteria from CSF and respiratory sources and in proteins previously reported to be associated with TB meningitis. Transcription factors and other transcription regulators featured prominently in these proteins. Homologs of proteins associated with Streptococcus pneumoniae meningitis and Neisseria meningitidis virulence were identified in neuropathogenic as well as respiratory mycobacterial spp. examined in this study. Discussion The occurrence of in silico genetic differences in CSF-derived but not respiratory Mtb suggests their possible involvement in the pathogenesis of TBM. However, overall findings in this comparative analysis support the postulation that TB

  7. Isolated ellipticals and their globular cluster systems. III. NGC 2271, NGC 2865, NGC 3962, NGC 4240, and IC 4889

    Science.gov (United States)

    Salinas, R.; Alabi, A.; Richtler, T.; Lane, R. R.

    2015-05-01

    As tracers of star formation, galaxy assembly, and mass distribution, globular clusters have provided important clues to our understanding of early-type galaxies. But their study has been mostly constrained to galaxy groups and clusters where early-type galaxies dominate, leaving the properties of the globular cluster systems (GCSs) of isolated ellipticals as a mostly uncharted territory. We present Gemini-South/GMOS g'i' observations of five isolated elliptical galaxies: NGC 3962, NGC 2865, IC 4889, NGC 2271, and NGC 4240. Photometry of their GCSs reveals clear color bimodality in three of them, but remains inconclusive for the other two. All the studied GCSs are rather poor with a mean specific frequency SN ~ 1.5, independently of the parent galaxy luminosity. Considering information from previous work as well, it is clear that bimodality and especially the presence of a significant, even dominant, population of blue clusters occurs at even the most isolated systems, which casts doubts on a possible accreted origin of metal-poor clusters, as suggested by some models. Additionally, we discuss the possible existence of ultra-compact dwarfs around the isolated elliptical NGC 3962. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).Globular cluster photometry is available in electronic form at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/577/A59Appendices are available in

  8. Extremely Isolated Galaxies I. Sample and Simulation Analysis

    OpenAIRE

    Spector, O.; Brosch, N.

    2016-01-01

    We have selected a sample of extremely isolated galaxies (EIGs) from the local Universe ($\\mbox{z} < 0.024$), using a simple isolation criterion: having no known neighbours closer than $300\\,{\\rm km\\,s}^{-1}$ ($3\\,h^{-1}\\,\\mbox{Mpc}$) in the three-dimensional redshift space $(\\alpha,\\delta,\\mbox{z})$. The sample is unique both in its level of isolation and in the fact that it utilizes HI redshifts from the Arecibo Legacy Fast ALFA survey (ALFALFA). We analysed the EIG sample using cosmologica...

  9. Extremely isolated galaxies - I. Sample and simulation analysis

    Science.gov (United States)

    Spector, O.; Brosch, N.

    2016-02-01

    We have selected a sample of extremely isolated galaxies (EIGs) from the local Universe (z ALFALFA) survey. We analysed the EIG sample using cosmological simulations and found that it contains EIGs with normal mass haloes which have evolved gradually with little or no `major events' (major mergers, or major mass-loss events) in the last 3 Gyr. The fraction of EIGs which deviate from this definition (false positives) is 5-10 per cent. For the general population of dark matter haloes, it was further found that the mass accretion (relative to the current halo mass) is affected by the halo environment mainly through strong interactions with its neighbours. As long as a halo does not experience major events, its mass accretion history does not depend significantly on its environment. `Major events' seem to be the main mechanism that creates low-mass subhaloes (Mhalo < 1010 h- 1 M⊙) that host galaxies (with Mg ≲ -14).

  10. Response of seismic isolated structures during extreme events

    International Nuclear Information System (INIS)

    Tajirian, F.F.; Abrahamson, N.A.

    1991-01-01

    In this paper the differences between the long period (T > 2 sec) and high frequency (f > 2 Hz) components of earthquakes are reviewed. Synthetic earthquake time histories are developed for a generic site in California close to major faults for two earthquake levels, SSE (Safe Shutdown Earthquake) and BDBE (Beyond Design Basis Earthquake). Dynamic analyses are performed to compute the response of the isolated PRISM (Power Reactor Innovative Small Module) Advanced Liquid Metal Reactor. (J.P.N.)

  11. Globular Clusters for Faint Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2017-07-01

    The origin of ultra-diffuse galaxies (UDGs) has posed a long-standing mystery for astronomers. New observations of several of these faint giants with the Hubble Space Telescope are now lending support to one theory.Faint-Galaxy MysteryHubble images of Dragonfly 44 (top) and DFX1 (bottom). The right panels show the data with greater contrast and extended objects masked. [van Dokkum et al. 2017]UDGs large, extremely faint spheroidal objects were first discovered in the Virgo galaxy cluster roughly three decades ago. Modern telescope capabilities have resulted in many more discoveries of similar faint galaxies in recent years, suggesting that they are a much more common phenomenon than we originally thought.Despite the many observations, UDGs still pose a number of unanswered questions. Chief among them: what are UDGs? Why are these objects the size of normal galaxies, yet so dim? There are two primary models that explain UDGs:UDGs were originally small galaxies, hence their low luminosity. Tidal interactions then puffed them up to the large size we observe today.UDGs are effectively failed galaxies. They formed the same way as normal galaxies of their large size, but something truncated their star formation early, preventing them from gaining the brightness that we would expect for galaxies of their size.Now a team of scientists led by Pieter van Dokkum (Yale University) has made some intriguing observations with Hubble that lend weight to one of these models.Globulars observed in 16 Coma-cluster UDGs by Hubble. The top right panel shows the galaxy identifications. The top left panel shows the derived number of globular clusters in each galaxy. [van Dokkum et al. 2017]Globulars GaloreVan Dokkum and collaborators imaged two UDGs with Hubble: Dragonfly 44 and DFX1, both located in the Coma galaxy cluster. These faint galaxies are both smooth and elongated, with no obvious irregular features, spiral arms, star-forming regions, or other indications of tidal interactions

  12. Effect of xylose and nutrients concentration on ethanol production by a newly isolated extreme thermophilic bacterium

    DEFF Research Database (Denmark)

    Tomás, Ana Faria; Karakashev, Dimitar Borisov; Angelidaki, Irini

    2011-01-01

    An extreme thermophilic ethanol-producing strain was isolated from an ethanol high-yielding mixed culture, originally isolated from a hydrogen producing reactor operated at 70 °C. Ethanol yields were assessed with increasing concentrations of xylose, up to 20 g/l. The ability of the strain to gro...... product under most of the conditions tested, including in media lacking vitamins, peptone and yeast extract. The results indicate that this new organism is a promising candidate for the development of a second generation bio-ethanol production process. © IWA Publishing 2011....

  13. Collisions between Globular Clusters

    Science.gov (United States)

    Belloni, D. T.; Rocha-Pinto, H. J.

    2014-10-01

    The study of globular clusters (GC) plays an important role in our understanding of the Universe since these systems are true laboratories for theories of stellar dynamics and evolution. We are interested in studying a globular cluster formed by a collision between two different GC with NBODY6 (Aarseth, 2003). Firstly, in order to understand this code, we analyse how tidal streams form from a globular cluster in a circular orbit (on the disk) around the center of the Milky Way. In the next stage of this work we will study that collision. The stellar escape or capture from globular cluster can be understood with the Restricted Three Body Problem. These stars escape in a chaotic orbit, and in some cases may return (again in a chaotic orbit) to the cluster due to the Galactic potential. In most cases, such stars quickly alter their escape chaotic orbits to orbits that are similar to the parent cluster's orbit. Our results show an agglomeration of stars in a normal direction related to the direction towards the center of the Milky Way, forming thus a stream. We can explain this considering that a circular orbit around the dominant potential is the most likely orbit, since it requires minimum energy. In this coordinate systems, the tidal tails (or streams) rotates around the cluster center with the same mean motion associated to cluster around the Milky Way center.

  14. Globular Clusters - Guides to Galaxies

    CERN Document Server

    Richtler, Tom; Joint ESO-FONDAP Workshop on Globular Clusters

    2009-01-01

    The principal question of whether and how globular clusters can contribute to a better understanding of galaxy formation and evolution is perhaps the main driving force behind the overall endeavour of studying globular cluster systems. Naturally, this splits up into many individual problems. The objective of the Joint ESO-FONDAP Workshop on Globular Clusters - Guides to Galaxies was to bring together researchers, both observational and theoretical, to present and discuss the most recent results. Topics covered in these proceedings are: internal dynamics of globular clusters and interaction with host galaxies (tidal tails, evolution of cluster masses), accretion of globular clusters, detailed descriptions of nearby cluster systems, ultracompact dwarfs, formations of massive clusters in mergers and elsewhere, the ACS Virgo survey, galaxy formation and globular clusters, dynamics and kinematics of globular cluster systems and dark matter-related problems. With its wide coverage of the topic, this book constitute...

  15. Characterization of an extremely halotolerant Staphylococcus arlettae HPSSN35C isolated from Dwarka Beach, India.

    Science.gov (United States)

    Nanjani, Sandhya G; Soni, Harsha P

    2014-08-01

    An extremely halotolerant bacterium designated as HPSSN35C was isolated from saline soil of Dwarka beach, India. It exhibited growth over a wide range of NaCl in medium varying from 0 to 6 M. The isolate produced peach-pink pigment above ∼1.3 M NaCl. The culture was characterized using biochemical tests, bioMerieux Staph identification kit, API ID32 Staph system, and Biolog. Due to slow growth and extreme salt tolerance no ID was obtained in Biolog. Antibiotic sensitivity to various antibiotics was tested. Phenotypic characterization showed that it belonged to the novobiocin resistant staphylococci group. Analysis of 16S rRNA gene sequence comparison of 1452 base pairs showed that isolate is closely related to Staphylococcus saprophyticus group with close relationship to Staphylococcus arlettae (99% similarity). The halotolerant S. arlettae described in literature till date have been reported to tolerate 4.5 M NaCl and produce white to yellow pigment. The present study reports for the first time extremely halotolerant S. arlettae exhibiting growth up to ∼6 M NaCl and producing peach-pink pigment above ∼1.3 M NaCl. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Extreme earthquake response of nuclear power plants isolated using sliding bearings

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Manish, E-mail: mkumar@iitgn.ac.in [Department of Civil Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar 382355 (India); Whittaker, Andrew S.; Constantinou, Michael C. [Department of Civil, Structural and Environmental Engineering, University at Buffalo, Buffalo, NY 14260 (United States)

    2017-05-15

    Highlights: • Response-history analysis of a nuclear power plant (NPP) isolated using sliding bearings. • Two models of the NPP, five friction models and four seismic hazard levels considered. • Isolation system displacement can be obtained using a macro NPP model subjected to only horizontal ground motions. • Temperature dependence of friction should be considered in isolation-system displacement calculations. • The effect of friction model on floor spectral ordinates is rather small, especially near the basemat. - Abstract: Horizontal seismic isolation is a viable approach to mitigate risk to structures, systems and components (SSCs) in nuclear power plants (NPPs) under extreme ground shaking. This paper presents a study on an NPP seismically isolated using single concave Friction Pendulum™ (FP) bearings subjected to ground motions representing seismic hazard at two US sites: Diablo Canyon and Vogtle. Two models of the NPP, five models to describe friction at the sliding surface of the FP bearings, and four levels of ground shaking are considered for response-history analysis, which provide insight into the influence of 1) the required level of detail of an NPP model, 2) the vertical component of ground motion on response of isolated NPPs, and 3) the pressure-, temperature- and/or velocity-dependencies of the coefficient of friction, on the response of an isolated NPP. The isolation-system displacement of an NPP can be estimated using a macro model subjected to only the two orthogonal horizontal components of ground motion. The variation of the coefficient of friction with temperature at the sliding surface during earthquake shaking should be accounted for in the calculation of isolation-system displacements, particularly when the shaking intensity is high; pressure and velocity dependencies are not important. In-structure floor spectra should be computed using a detailed three-dimensional model of an isolated NPP subjected to all three components of

  17. Effect of xylose and nutrients concentration on ethanol production by a newly isolated extreme thermophilic bacterium.

    Science.gov (United States)

    Tomas, Ana F; Karakashev, Dimitar; Angelidaki, Irini

    2011-01-01

    An extreme thermophilic ethanol-producing strain was isolated from an ethanol high-yielding mixed culture, originally isolated from a hydrogen producing reactor operated at 70 degrees C. Ethanol yields were assessed with increasing concentrations of xylose, up to 20 g/l. The ability of the strain to grow without nutrient addition (yeast extract, peptone and vitamins) was also assessed. The maximum ethanol yield achieved was 1.28 mol ethanol/mol xylose consumed (77% of the theoretical yield), at 2 g/l of initial xylose concentration. The isolate was able to grow and produce ethanol as the main fermentation product under most of the conditions tested, including in media lacking vitamins, peptone and yeast extract. The results indicate that this new organism is a promising candidate for the development of a second generation bio-ethanol production process.

  18. Study on bioremediation of Lead by exopolysaccharide producing metallophilic bacterium isolated from extreme habitat

    Directory of Open Access Journals (Sweden)

    Debajit Kalita

    2017-12-01

    Full Text Available Lead released from manufacturing factories, recycling plants, automobile company and landfill leachate is abundantly found in wastewater. An efficient bioremediating agent for lead removal from wastewater is expected to ease the ever increasing problem. The present study reports Pseudomonas sp. W6 isolated from extreme habitat of hot water spring of North–East India evaluated for its Lead biosorption property. The bacterium showed capacity to resist 1.0 mM lead in both solid and liquid minimal media. Epifluorescence microscopy reveal the viability of bacterial cells under metal stress condition. ICP-MS analysis revealed 65% and 61.2% removal of lead from the Synthetic Bangladesh Ground Water medium in batch culture and column study respectively which was higher when compared to biosorption capacity of P. aeruginosa MTCC2474, P. alcaligenes MJ7 from forest soil and P. ficuserectae PKRS11 from uranium rich soil. Exopolysaccharide released by the isolate which influenced biosorption revealed the presence of ligands assayed using microbial hydrophobicity and FTIR. The extremophilic isolate is proposed as a choice for efficient bioremediation of lead contaminated wastewater. Keywords: Extremophile, Pseudomonas, Lead bioremediation, Epifluorescence microscopy, ICP-MS, FTIR

  19. Study on bioremediation of Lead by exopolysaccharide producing metallophilic bacterium isolated from extreme habitat.

    Science.gov (United States)

    Kalita, Debajit; Joshi, S R

    2017-12-01

    Lead released from manufacturing factories, recycling plants, automobile company and landfill leachate is abundantly found in wastewater. An efficient bioremediating agent for lead removal from wastewater is expected to ease the ever increasing problem. The present study reports Pseudomonas sp. W6 isolated from extreme habitat of hot water spring of North-East India evaluated for its Lead biosorption property. The bacterium showed capacity to resist 1.0 mM lead in both solid and liquid minimal media. Epifluorescence microscopy reveal the viability of bacterial cells under metal stress condition. ICP-MS analysis revealed 65% and 61.2% removal of lead from the Synthetic Bangladesh Ground Water medium in batch culture and column study respectively which was higher when compared to biosorption capacity of P. aeruginosa MTCC 2474, P. alcaligenes MJ7 from forest soil and P. ficuserectae PKRS11 from uranium rich soil. Exopolysaccharide released by the isolate which influenced biosorption revealed the presence of ligands assayed using microbial hydrophobicity and FTIR. The extremophilic isolate is proposed as a choice for efficient bioremediation of lead contaminated wastewater.

  20. Mapping the spectral phase of isolated attosecond pulses by extreme-ultraviolet emission spectrum.

    Science.gov (United States)

    Liu, Candong; Zeng, Zhinan; Li, Ruxin; Xu, Zhizhan; Nisoli, Mauro

    2015-04-20

    An all-optical method is proposed for the measurement of the spectral phase of isolated attosecond pulses. The technique is based on the generation of extreme-ultraviolet (XUV) radiation in a gas by the combination of an attosecond pulse and a strong infrared (IR) pulse with controlled electric field. By using a full quantum simulation, we demonstrate that, for particular temporal delays between the two pulses, the IR field can drive back to the parent ions the photoelectrons generated by the attosecond pulse, thus leading to the generation of XUV photons. It is found that the generated XUV spectrum is notably sensitive to the chirp of the attosecond pulse, which can then be reliably retrieved. A classical quantum-path analysis is further used to quantitatively explain the main features exhibited in the XUV emission.

  1. Individual Traits, Personal Values, and Conflict Resolution in an Isolated, Confined, Extreme Environment.

    Science.gov (United States)

    Corneliussen, Jesper G; Leon, Gloria R; Kjærgaard, Anders; Fink, Birgit A; Venables, Noah C

    2017-06-01

    The study of personality traits, personal values, and the emergence of conflicts within groups performing in an isolated, confined, and extreme environment (ICE) may provide insights helpful for the composition and support of space crews for long duration missions. Studied pre/post and over the 2-yr period of the investigation were 10 Danish military personnel deployed to stations in Greenland on a 26-mo staggered rotation. Subjects completed the NEO PI-R, Triarchic Psychopathy Measure, and Portrait Values Questionnaire, and participated in structured interviews. During deployment, questionnaires were completed biweekly and a cognitive function test once a month. Personality findings indicated a generally well-adjusted group, above average in positive personality traits [Conscientiousness T-score = 59.4 (11.41); Agreeableness T-score = 54.4 (9.36)] and boldness. Personal values of benevolence and self-direction were highly rated. The decision when to "pick sides" and intervene during disagreements between group members was viewed as an important component of conflict resolution. There were no changes in positive/negative affect or cognitive function over the annual light/dark cycle. The personal values of group members appear highly compatible for living in a small group ICE environment for an extended period. Disagreements between group members impact the functioning of the entire group, particularly in regard to decisions whether to support one of the individuals or let the argument run its course. Extended training in strategies for conflict resolution are needed in planning for future long duration missions to avoid fault lines forming within the group.Corneliussen JG, Leon GR, Kjærgaard A, Fink BA, Venables NC. Individual traits, personal values, and conflict resolution in an isolated, confined, extreme environment. Aerosp Med Hum Perform. 2017; 88(6):535-543.

  2. Relative Ages of Globular Clusters

    Science.gov (United States)

    Puzia, Thomas H.

    Ages of extragalactic globular clusters can provide valuable insights into the formation and evolution of galaxies. In this contribution the photometric methods of age dating old globular cluster systems are summarised. The spectroscopic approach is reviewed with an emphasis of the fight choice of age diagnostics. We present a new method of quantifying the relatively best age-sensitive spectroscopic index given the quality of a data set and a certain theoretical stellar synthesis model. The relatively best diagnostic plot is constructed from the set of Lick indices and used to age date globular clusters in several early-type galaxies which are part of a large spectroscopic survey of extragalactic globular cluster systems. We find that, independently of host galaxy, metal-poor ([Fe/H] old (t > 8 Gyr) and coeval. Metal-rich clusters show a wide range of ages from ˜ 15 down to a few Gyr.

  3. Relativistic Binaries in Globular Clusters

    Directory of Open Access Journals (Sweden)

    Matthew J. Benacquista

    2013-03-01

    Full Text Available Galactic globular clusters are old, dense star systems typically containing 10^4 – 10^6 stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution that leads to relativistic binaries, and current and possible future observational evidence for this population. Our discussion of globular cluster evolution will focus on the processes that boost the production of tight binary systems and the subsequent interaction of these binaries that can alter the properties of both bodies and can lead to exotic objects. Direct N-body integrations and Fokker–Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.

  4. Lentibacillus kimchii sp. nov., an extremely halophilic bacterium isolated from kimchi, a Korean fermented vegetable.

    Science.gov (United States)

    Oh, Young Joon; Lee, Hae-Won; Lim, Seul Ki; Kwon, Min-Sung; Lee, Jieun; Jang, Ja-Young; Lee, Jong Hee; Park, Hae Woong; Nam, Young-Do; Seo, Myung-Ji; Roh, Seong Woon; Choi, Hak-Jong

    2016-06-01

    A Gram-positive, aerobic, non-motile and extremely halophilic bacterial strain, designated K9(T), was isolated from kimchi, a Korean fermented food. The strain was observed as endospore-forming rod-shaped cells showing oxidase and catalase activity. It was found to grow at 10.0-30.0 % (w/v) NaCl (optimum, 15.0-20.0 %), pH 7.0-8.0 (optimum, pH 7.5) and 15-40 °C (optimum, 30 °C). The polar lipids of strain K9(T) were identified as phosphatidylglycerol, three unidentified phospholipids and an unidentified glycolipid. The isoprenoid quinone was identified as menaquinone-7. The major cellular fatty acids (>20 % of the total) were found to be anteisio-C15:0 and anteisio-C17:0. The cell wall peptidoglycan composition was determined to contain meso-diaminopimelic acid. The G + C content of genomic DNA was determined to be 48.2 mol %. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the isolated strain is closely related to Lentibacillus salinarum AHS-1(T) (96.7 % sequence similarity). Based on its phenotypic, chemotaxonomic and phylogenetic data, strain K9(T) is considered to represent a novel species of the genus Lentibacillus, for which the name Lentibacillus kimchii sp. nov., is proposed. The type strain is K9(T) (=KACC 18490(T) = JCM 30234(T)).

  5. Four newly isolated fuselloviruses from extreme geothermal environments reveal unusual morphologies and a possible interviral recombination mechanism

    DEFF Research Database (Denmark)

    Redder, Peter; Peng, Xu; Brügger, Kim

    2009-01-01

    Spindle-shaped virus-like particles are abundant in extreme geothermal environments, from which five spindle-shaped viral species have been isolated to date. They infect members of the hyperthermophilic archaeal genus Sulfolobus, and constitute the Fuselloviridae, a family of double-stranded DNA...

  6. Isolation from soil and properties of the extreme thermophile Clostridium thermohydrosulfuricum.

    Science.gov (United States)

    Wiegel, J; Ljungdahl, L G; Rawson, J R

    1979-09-01

    Thirteen strains of a strict anaerobic, extreme thermophilic bacterium were isolated from soil samples of moderate temperature, from a sewage plant in Georgia, and from hot springs in Utah and Wyoming. They were identified as strains of Clostridium thermohydrosulfuricum. The guanosine + cytosine content (moles percent) was 37.6 (determined by buoyant density) and 34.1 (determined by melting temperature). All strains required a factor present in yeast extract or tryptone growth. Growth characteristics were as follows: a pH range of 5 to 9, with the optimum between 6.9 to 7.5, in a temperature range of 40 to 78 degrees C, with the optimum at 68 degrees C. The doubling time, when grown on glucose at temperature and pH optima, was 1.2 h. The main products of glucose fermentation were ethanol, lactate, acetate, CO2, and H2. The fermentation was inhibited by H2. Formation of spores occurred easily on glucose-agar medium or when cultures growing at temperatures above 65 degrees C were allowed to cool to temperature below 55 degrees C. C. thermohydrosulfuricum occurs widely distributed in the natural environment.

  7. Halopenitus malekzadehii sp. nov., an extremely halophilic archaeon isolated from a salt lake.

    Science.gov (United States)

    Amoozegar, Mohammad Ali; Makhdoumi-Kakhki, Ali; Mehrshad, Maliheh; Fazeli, Seyed Abolhassan Shahzadeh; Ventosa, Antonio

    2013-09-01

    Strain CC65(T), a novel extremely halophilic archaeon, was isolated from a brine sample of a salt lake in Iran. The novel strain was light yellow-pigmented, non-motile, pleomorphic and required at least 1.7 M NaCl and 0.02 M MgCl₂ for growth. Optimal growth was achieved at 3.5 M NaCl and 0.4 M MgCl₂. The optimum pH and temperature for growth were pH 7.5 and 40 °C, respectively, while it was able to grow over a pH and a temperature range of pH 6.5-9.0 and 30-50 °C, respectively. Analysis of 16S rRNA gene sequence revealed that strain CC65(T) clustered with the sole member of the genus Halopenitus, Halopenitus persicus DC30(T) with a sequence similarity of 98.0%. The polar lipid profile of strain CC65(T) consisted of phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester. An unidentified glycolipid and two minor phospholipids were also observed. The only quinone present was MK-8(II-H₂). The DNA G+C content of strain CC65(T) was 63.8 mol%. On the basis of the biochemical and physiological characteristics, as well as DNA-DNA hybridization (44% with Halopenitus persicus IBRC 10041(T)), strain CC65(T) is classified as a novel species of the genus Halopenitus, for which the name Halopenitus malekzadehii sp. nov. is proposed. The type strain is CC65(T) ( = IBRC-M 10418(T) =KCTC 4045(T)).

  8. Isolated psychosis during exposure to very high and extreme altitude - characterisation of a new medical entity.

    Science.gov (United States)

    Hüfner, Katharina; Brugger, Hermann; Kuster, Eva; Dünsser, Franziska; Stawinoga, Agnieszka E; Turner, Rachel; Tomazin, Iztok; Sperner-Unterweger, Barbara

    2017-12-05

    Psychotic episodes during exposure to very high or extreme altitude have been frequently reported in mountain literature, but not systematically analysed and acknowledged as a distinct clinical entity. Episodes reported above 3500 m altitude with possible psychosis were collected from the lay literature and provide the basis for this observational study. Dimensional criteria of the Diagnostic and Statistical Manual of Mental Disorders were used for psychosis, and the Lake Louise Scoring criteria for acute mountain sickness and high-altitude cerebral oedema (HACE). Eighty-three of the episodes collected underwent a cluster analysis to identify similar groups. Ratings were done by two independent, trained researchers (κ values 0.6-1). Findings Cluster 1 included 51% (42/83) episodes without psychosis; cluster 2 22% (18/83) cases with psychosis, plus symptoms of HACE or mental status change from other origins; and cluster 3 28% (23/83) episodes with isolated psychosis. Possible risk factors of psychosis and associated somatic symptoms were analysed between the three clusters and revealed differences regarding the factors 'starvation' (χ2 test, p = 0.002), 'frostbite' (p = 0.024) and 'supplemental oxygen' (p = 0.046). Episodes with psychosis were reversible but associated with near accidents and accidents (p = 0.007, odds ratio 4.44). Episodes of psychosis during exposure to high altitude are frequently reported, but have not been specifically examined or assigned to medical diagnoses. In addition to the risk of suffering from somatic mountain illnesses, climbers and workers at high altitude should be aware of the potential occurrence of psychotic episodes, the associated risks and respective coping strategies.

  9. Haloterrigena salina sp. nov., an extremely halophilic archaeon isolated from a salt lake.

    Science.gov (United States)

    Gutiérrez, M C; Castillo, A M; Kamekura, M; Ventosa, A

    2008-12-01

    A novel extremely halophilic strain, designated XH-65(T), isolated from the salt lake Xilinhot in Inner Mongolia, PR China, was subjected to a polyphasic taxonomic characterization. Strain XH-65(T) is neutrophilic, non-motile and requires at least 2.5 M NaCl for growth, with an optimum at 3.4 M NaCl, and grows at pH 6.0-9.0, with optimum growth at pH 7.5. Strain XH-65(T) grows at 25-50 degrees C, with optimal growth at 37 degrees C. Magnesium is not required for growth. On the basis of 16S rRNA gene sequence analysis, strain XH-65(T) was shown to belong to the genus Haloterrigena and was related to Haloterrigena turkmenica VKM B-1734(T) (98.1 % sequence similarity), Haloterrigena saccharevitans AB14(T) (96.9 %), Haloterrigena thermotolerans PR5(T) (96.3 %), Haloterrigena limicola AX-7(T) (95.8 %) and Haloterrigena hispanica FP1(T) (95.7 %). DNA-DNA hybridization revealed 37 % relatedness between strain XH-65(T) and Htg. turkmenica VKM B-1734(T). The polar lipid composition revealed the presence of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and mannose-2,6-disulfate (1-->2)-glucose glycerol diether (S(2)-DGD). The results of the DNA-DNA hybridization and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain XH-65(T) from the six Haloterrigena species with validly published names. Therefore, strain XH-65(T) represents a novel species, for which the name Haloterrigena salina sp. nov. is proposed, with the type strain XH-65(T) (=CGMCC 1.6203(T) =JCM 13891(T)).

  10. Draft Genome Sequence of the Extremely Halophilic Bacillus sp. Strain SB49, Isolated from a Salt Crystallizer Pond of the Little Rann of Kutch, India

    Science.gov (United States)

    Dey, Rinku; Thomas, Manesh; Sherathia, Dharmesh; Dalsania, Trupti; Patel, Ilaxi; Savsani, Kinjal; Ghorai, Sucheta; Vanpariya, Sejal; Sukhadiya, Bhoomika; Mandaliya, Mona; Rupapara, Rupal; Rawal, Priya

    2013-01-01

    Here we report the draft whole-genome sequence (3.72 Mbp) of Bacillus sp. strain SB49, an extremely halophilic bacterium isolated from a salt crystallizer pond of the Little Rann of Kutch in India. Unraveling the genome of this organism will facilitate understanding and isolation of the genes involved in imparting extreme osmotolerance. PMID:24136852

  11. Nonlinear dynamics of globular proteins

    Energy Technology Data Exchange (ETDEWEB)

    Lomdahl, P.S.

    1983-01-01

    Some ongoing work aimed at generalizing DAVYDOV's ideas to a real globular protein is described. So far, a computer code, GLOP, which calculates amide-I bond energy evolution on a globular protein has been developed and tested. The code is quite versatile and takes as input the coordinates of a protein. The full geometry of the molecule is then taken into account when the dipole-dipole interaction between peptide groups is calculated. The amide-I energy is coupled to one intramolecular excitation, but can without difficulty be extended to more or to include intermolecular excitations.

  12. Variability among strains of Aspergillus section Nigri with capacity to degrade tannic acid isolated from extreme environments.

    Science.gov (United States)

    Lara-Victoriano, F; Veana, F; Hernández-Castillo, F D; Aguilar, C N; Reyes-Valdés, M H; Rodríguez-Herrera, R

    2017-01-01

    Tannins are polyphenolic compounds that cause astringent flavor and turbidity in food. Tannase is an enzyme that catalyzes the hydrolysis of tannins and is used in food industry. This study was conducted to determine the genetic variability and the tannase alleles variation in fungal strains isolated from soil and plants at five extreme areas of Coahuila, México. Two screening assays under 1 and 20 % of tannic acid were performed, with the isolations. In these assays, it was possible to identify 756 and 128 fungal strains, respectively. The major fungal variability was observed in "Cuatro Ciénegas" with 26 strains. The microorganisms were distributed in 11 groups, which correspond to Aspergillus section Nigri. AN7 and AN1 groups showed the major number of isolates from "Paila" and "Cuatro Ciénegas" locations, respectively. In the last location, the major diversity and specific richness were found. But in "Ojo Caliente," tannase allele conservations were observed.

  13. Summary of presentation for research on social structure, agreement, and conflict in groups in extreme and isolated environments

    Science.gov (United States)

    1990-01-01

    Despite a vast amount of research, little is known concerning the effect of group structure, and individuals' understanding of that structure, on conflict in Antarctic groups. The overall objective of the research discussed is to determine the interrelationships of group structure, social cognition, and group function and conflict in isolated and extreme environments. In the two decades following WWII, a large body of research focused on the physiological, psychological, and social psychological factors affecting the functioning of individuals and groups in a variety of extreme and isolated environments in both the Arctic and Antarctic. There are two primary reasons for further research of this type. First, Antarctic polar stations are considered to be natural laboratories for the social and behavioral sciences and provide an opportunity to address certain theoretical and empirical questions concerned with agreement and conflict in social groups in general and group behavior in extreme, isolated environments in particular. Recent advances in the analysis of social networks and intracultural variation have improved the methods and have shifted the theoretical questions. The research is motivated by three classes of questions: (1) What are the characteristics of the social relations among individuals working and living together in extreme and isolated environments?; (2) What do individuals understand about their group, how does that understanding develop, and how is it socially distributed?; and (3) What is the relationship between that understanding and the functioning of the social group? Answers to these questions are important if we are to advance our knowledge of how individuals and groups adapt to extreme environments. Second, although Antarctic winter-over candidates may be evaluated as qualified on the basis of individual characteristics, they may fail to adapt because of certain characteristics of the social group. Consequently, the ability of winter

  14. Isolation and identification of a Candida digboiensis strain from an extreme acid mine drainage of the Lignite Mine, Gujarat.

    Science.gov (United States)

    Patel, Mitesh J; Tipre, Devayani R; Dave, Shailesh R

    2009-12-01

    An extremely acidic mine drainage (AMD) water sample was collected in 1998 and 2008 from Panandhro lignite mine, Gujarat, India. The yeast isolated from this sample was identified using mini API identification system, as a member of genus Candida. The major cellular fatty acids detected by FAME from the isolate are C(16:0) and C(18:2) (cis 9,12)/C(18:0alpha) as 25.23 and 19.5%, respectively. The isolate was identified as Candida digboiensis by 18S rRNA gene sequence analysis and designated as Candida digboiensis SRDyeast1. Phylogenetic analysis using D1/D2 variable domains showed that the closest relative of this strain is Candida blankii with 3% divergence. This organism has been reported for the first time from the lignite mine AMD sample, and for cellular fatty acid analysis. This yeast is able to survive in the AMD sample preserved at 10-42 degrees C temperature since last 10 years along with iron oxidizing microorganisms. It can grow in the presence of 40% glucose, 10% NaCl and in the pH range of 1 to 10. The isolate is capable of producing enzymes like protease and lipase. This isolate differs from the type strain Candida digboiensis in as many as six physiological and metabolic characteristics.

  15. Speckle imaging of globular clusters

    International Nuclear Information System (INIS)

    Sams, B.J. III

    1990-01-01

    Speckle imaging is a powerful tool for high resolution astronomy. Its application to the core regions of globular clusters produces high resolution stellar maps of the bright stars, but is unable to image the faint stars which are most reliable dynamical indicators. The limits on resolving these faint, extended objects are physical, not algorithmic, and cannot be overcome using speckle. High resolution maps may be useful for resolving multicomponent stellar systems in the cluster centers. 30 refs

  16. Women and Couples in Isolated Extreme Environments: Applications for Long-Duration Missions

    Science.gov (United States)

    Leon, G. R.; Sandal, G. M.

    four women from Greenland, Denmark, UK and Russia who traversed the Greenland ice by ski. The participants did not know each other prior to the expedition. Three were classified as "the right stuff' based on PCI findings. Diary and post-expedition reports indicated that incidents of interpersonal tension were often related to fatigue, homesickness, pain or cold. The participants also indicated that respect and tolerance for differences between them, as weIl as mutual emotional support were crucial factors for the successful completion of the expedition. Group 3 consisted of 3 married couples and the 2 1/2 year old child of the leader and his wife. Five of the crew sailed a small boat from Norway to the Canadian High Arctic; the leader's wife and child joined the team in Greenland. Over a 9 month period, the icelocked boat was ilie center of habitation, scientific, and other activities. Three of the group carried out a 6 week exploratory trek at the end of the winter-over. Participants completed the MPQ prior to the expedition, a WRF over the entire Arctic period, and a semi-structured personality interview at the close of the interval during which the entire group was together. AlI participants scored relatively highest on the Absorption scale, manifested in the salutory experience of enjoying and becoming engrossed in the beauty of the environment. WRF and interview findings indicated that team members consistently reported that the emotional support of and ability to confide in their partner were extremely important in alleviating interpersonal tensions with other team members, and contributed to the overall effective functioning of the group. Reported level of emotional response to stress and coping patterns used while in the stationary habitat were consistent with WRF responses during the later exploratory trek. The woman team member on the trek reported more discomfort regarding personal hygiene issues and fear of injury .In alI groups, the salience of the

  17. Halocin SH10 production by an extreme haloarchaeon Natrinema sp. BTSH10 isolated from salt pans of South India.

    Science.gov (United States)

    Karthikeyan, P; Bhat, Sarita G; Chandrasekaran, M

    2013-04-01

    Halobacteria, members of the domain Archaea that live under extremely halophilic conditions, are often considered as dependable source for deriving novel enzymes, novel genes, bioactive compounds and other industrially important molecules. Protein antibiotics have potential for application as preserving agents in food industry, leather industry and in control of infectious bacteria. Halocins are proteinaceous antibiotics synthesized and released into the environment by extreme halophiles, a universal characteristic of halophilic bacteria. Herein, we report the production of halocin (SH10) by an extremely halophilic archeon Natrinema sp. BTSH10 isolated from salt pan of Kanyakumari, Tamilnadu, India and optimization of medium for enhanced production of halocin. It was found that the optimal conditions for maximal halocin production were 42 °C, pH 8.0, and 104 h of incubation at 200 rpm with 2% (V/V) inoculum concentration in Zobell's medium containing 3 M NaCl, Galactose, beef extract, and calcium chloride as additional supplements. Results indicated scope for fermentation production of halocin for probable applications using halophilic archeon Natrinema sp. BTSH10.

  18. Polymer production by two newly isolated extremely halophilic archaea: application of a novel corrosion-resistant bioreactor.

    Science.gov (United States)

    Hezayen, F F; Rehm, B H; Eberhardt, R; Steinbüchel, A

    2000-09-01

    A novel corrosion-resistant bioreactor composed of polyetherether ketone (PEEK), tech glass and silicium nitrite ceramics was constructed and applied for the cultivation of two newly isolated, extremely halophilic archaea producing poly(gamma-glutamic acid) (PGA), or poly(beta-hydroxy butyric acid) (PHB), respectively. These bacteria were isolated from hypersaline soil close to Aswan (Egypt). The isolate strain 40, which is related to the genus Natrialba, produced large amounts of PGA when cultivated on solid medium. Culture conditions were optimised applying the corrosion-resistant bioreactor. PGA production was dependent on NaCl concentration and occurred about at 20% (w/v) NaCl in the medium. A maximum cell density of about 1.6 g cell dry matter/l was obtained when the bioreactor was stirred and aerated in a batch fermentation process using proteose-peptone medium. The supernatant was monitored with respect to PGA formation, and after 90 h a maximum of 470 mg/l culture volume was detected by HPLC analysis. Culture conditions were optimized for the isolate 56, which accumulated PHB as intracellular granules. Batch fermentations in the stirred and aerated bioreactor applying acetate and n-butyric acid as carbon sources led to cell density of 2.28 g cell dry matter/l and a maximum PHB accumulation contributing to about 53% of cellular dry weight. About 4.6 g PHB were isolated from 10.6 g dried cells of strain 56, which exhibited a weight average molar mass of 2.3 x 10(5) g mol(-1) and a polydispersity of about 1.4.

  19. Isolation and characterization of Caldicellulosiruptor lactoaceticus sp. nov., an extremely thermophilic, cellulolytic, anaerobic bacterium

    DEFF Research Database (Denmark)

    Mladenovska, Zuzana; Mathrani, Indra M.; Ahring, Birgitte Kiær

    1995-01-01

    and ethanol occurred as minor fermentation products. Only a restricted number of carbon sources (cellulose, xylan, starch, pectin, cellobiose, xylose, maltose and lactose) were used as substrates. During growth on Avicel, the bacterium produced free cellulases with carboxymethylcellulase and avicelase...... activity. The G + C content of the cellular DNA of strain 6A was 35.2 +/- 0.8 mol%. Complete 16S rDNA sequence analysis showed that strain 6A was phylogenetically related to Caldicellulosiruptor saccharolyticus. It is proposed that the isolated bacterium be named Caldicellulosiruptor lactoaceticus sp. nov....

  20. Social roles and the evolution of networks in extreme and isolated environments

    Science.gov (United States)

    Johnson, Jeffrey C.; Boster, James S.; Palinkas, Lawrence A.

    2003-01-01

    This article reports on the evolution of network structure as it relates to formal and informal social roles in well-bounded, isolated groups. Research was conducted at the Amundsen-Scott South Pole Station. Data were collected on crewmembers' networks of social interaction over each of three winter-over periods, when the station is completely isolated. In addition, data were collected on the informal roles played by crewmembers (e.g., instrumental leadership, expressive leadership). The study found that globally coherent networks in winter-over groups were associated with group consensus on the presence of critically important informal social roles (e.g., expressive leadership) where global coherence is the extent to which a network forms a single group composed of a unitary core and periphery as opposed to being factionalized into two or more subgroups. Conversely, the evolution of multiple subgroups was associated with the absence of consensus on critical informal social roles, above all the critically important role of instrumental leader.

  1. 3000 years of solitude: extreme differentiation in the island isolates of Dalmatia, Croatia.

    Science.gov (United States)

    Vitart, Veronique; Biloglav, Zrinka; Hayward, Caroline; Janicijevic, Branka; Smolej-Narancic, Nina; Barac, Lovorka; Pericic, Marijana; Klaric, Irena Martinovic; Skaric-Juric, Tatjana; Barbalic, Maja; Polasek, Ozren; Kolcic, Ivana; Carothers, Andrew; Rudan, Pavao; Hastie, Nick; Wright, Alan; Campbell, Harry; Rudan, Igor

    2006-04-01

    Communities with increased shared ancestry represent invaluable tools for genetic studies of complex traits. "1001 Dalmatians" research program collects biomedical information for genetic epidemiological research from multiple small isolated populations ('metapopulation') in the islands of Dalmatia, Croatia. Random samples of 100 individuals from 10 small island settlements (n<2000 inhabitants) were collected in 2002 and 2003. These island communities were carefully chosen to represent a wide range of distinct and well-documented demographic histories. Here, we analysed their genetic make-up using 26 short tandem repeat (STR) markers, at least 5 cM apart. We found a very high level of differentiation between most of these island communities based on Wright's fixation indexes, even within the same island. The model-based clustering algorithm, implemented in STRUCTURE, defined six clusters with very distinct genetic signatures, four of which corresponded to single villages. The extent of background LD, assessed with eight linked markers on Xq13-21, paralleled the extent of differentiation and was also very high in most of the populations under study. For each population, demographic history was characterised and 12 "demographic history" variables were tentatively defined. Following stepwise regression, the demographic history variable that most significantly predicted the extent of LD was the proportion of locally born grandparents. Strong isolation and endogamy are likely to be the main forces maintaining this highly structured overall population.

  2. Complete genome sequence of the extremely acidophilic methanotroph isolate V4, Methylacidiphilum infernorum, a representative of the bacterial phylum Verrucomicrobia

    Directory of Open Access Journals (Sweden)

    Stott Matthew B

    2008-07-01

    Full Text Available Abstract Background The phylum Verrucomicrobia is a widespread but poorly characterized bacterial clade. Although cultivation-independent approaches detect representatives of this phylum in a wide range of environments, including soils, seawater, hot springs and human gastrointestinal tract, only few have been isolated in pure culture. We have recently reported cultivation and initial characterization of an extremely acidophilic methanotrophic member of the Verrucomicrobia, strain V4, isolated from the Hell's Gate geothermal area in New Zealand. Similar organisms were independently isolated from geothermal systems in Italy and Russia. Results We report the complete genome sequence of strain V4, the first one from a representative of the Verrucomicrobia. Isolate V4, initially named "Methylokorus infernorum" (and recently renamed Methylacidiphilum infernorum is an autotrophic bacterium with a streamlined genome of ~2.3 Mbp that encodes simple signal transduction pathways and has a limited potential for regulation of gene expression. Central metabolism of M. infernorum was reconstructed almost completely and revealed highly interconnected pathways of autotrophic central metabolism and modifications of C1-utilization pathways compared to other known methylotrophs. The M. infernorum genome does not encode tubulin, which was previously discovered in bacteria of the genus Prosthecobacter, or close homologs of any other signature eukaryotic proteins. Phylogenetic analysis of ribosomal proteins and RNA polymerase subunits unequivocally supports grouping Planctomycetes, Verrucomicrobia and Chlamydiae into a single clade, the PVC superphylum, despite dramatically different gene content in members of these three groups. Comparative-genomic analysis suggests that evolution of the M. infernorum lineage involved extensive horizontal gene exchange with a variety of bacteria. The genome of M. infernorum shows apparent adaptations for existence under extremely

  3. Delignification and detoxification of peanut shell bio-waste using an extremely halophilic laccase from an Aquisalibacillus elongatus isolate.

    Science.gov (United States)

    Rezaie, Rezvan; Rezaei, Shahla; Jafari, Nasrin; Forootanfar, Hamid; Khoshayand, Mohammad Reza; Faramarzi, Mohammad Ali

    2017-11-01

    Lignocellulose bioconversion is a harsh process requiring the use of surfactants and organic solvents. Consequently, the incorporation of laccases in this bioconversion requires the bioprospecting of enzymes that can remain stable under extreme conditions. An extracellular, highly stable laccase was produced by the halophilic isolate Aquisalibacillus elongatus in submerged liquid culture fermentation. Statistical and non-statistical strategies gave the highest enzymatic activity (8.02 U mL -1 ) following addition of glucose (1.7 g L -1 ), copper sulfate (0.8 g L -1 ), urea (15 g L -1 ), and CaCl 2 (0.8 g L -1 ). The enzyme, after purification using a synthetic affinity support, delignified a peanut shell substrate by 45%. A pH of 8.0 and a temperature of 35 °C were optimal for delignification of this bio-waste material. Addition of [Bmim][PF 6 ], 1,4-dioxane, acetone, and HBT promoted this bio-waste delignification. Bio-treatment in the presence of 50% [Bmim][PF 6 ] gave a maximal lignin removal of 87%. The surfactants tested had no significant effects on the delignification yield. The laccase also detoxified the toxic phenols found in peanut shell waste. The high catalytic efficiency of this enzyme against a lignocellulosic sample under extreme conditions suggests the suitability of this laccase for industrial applications.

  4. Antagonistic interactions and production of halocin antimicrobial peptides among extremely halophilic prokaryotes isolated from the solar saltern of Sfax, Tunisia.

    Science.gov (United States)

    Ghanmi, Fadoua; Carré-Mlouka, Alyssa; Vandervennet, Manon; Boujelben, Ines; Frikha, Doniez; Ayadi, Habib; Peduzzi, Jean; Rebuffat, Sylvie; Maalej, Sami

    2016-05-01

    Thirty-five extremely halophilic microbial strains isolated from crystallizer (TS18) and non-crystallizer (M1) ponds in the Sfax solar saltern in Tunisia were examined for their ability to exert antimicrobial activity. Antagonistic assays resulted in the selection of eleven strains that displayed such antimicrobial activity and they were further characterized. Three cases of cross-domain inhibition (archaea/bacteria or bacteria/archaea) were observed. Four archaeal strains exerted antimicrobial activity against several other strains. Three strains, for which several lines of evidence suggested the antimicrobial activity was, at least in part, due to peptide/protein agents (Halobacterium salinarum ETD5, Hbt. salinarum ETD8, and Haloterrigena thermotolerans SS1R12), were studied further. Optimal culture conditions for growth and antimicrobial production were determined. Using DNA amplification with specific primers, sequencing and RT-PCR analysis, Hbt. salinarum ETD5 and Hbt. salinarum ETD8 were shown to encode and express halocin S8, a hydrophobic antimicrobial peptide targeting halophilic archaea. Although the gene encoding halocin H4 was amplified from the genome of Htg. thermotolerans SS1R12, no transcript could be detected and the antimicrobial activity was most likely due to multiple antimicrobial compounds. This is also the first report that points to four different strains isolated from different geographical locations with the capacity to produce identical halocin S8 proteins.

  5. Metallicity Spreads in M31 Globular Clusters

    Science.gov (United States)

    Bridges, Terry

    2003-07-01

    Our recent deep HST photometry of the M31 halo globular cluster {GC} Mayall II, also called G1, has revealed a red-giant branch with a clear spread that we attribute to an intrinsic metallicity dispersion of at least 0.4 dex in [Fe/H]. The only other GC exhibiting such a metallicity dispersion is Omega Centauri, the brightest and most massive Galactic GC, whose range in [Fe/H] is about 0.5 dex. These observations are obviously linked to the fact that both G1 and Omega Cen are bright and massive GC, with potential wells deep enough to keep part of their gas, which might have been recycled, producing a metallicity scatter among cluster stars. These observations dramatically challenge the notion of chemical homogeneity as a defining characteristic of GCs. It is critically important to find out how common this phenomenon is and how it can constrain scenarios/models of GC formation. The obvious targets are other bright and massive GCs, which exist in M31 but not in our Galaxy where Omega Cen is an isolated giant. We propose to acquire, with ACS/HRC, deep imaging of 3 of the brightest M31 GCs for which we have observed velocity dispersion values similar to those observed in G1 and Omega Cen. A sample of GCs with chemical abundance dispersions will provide essential information about their formation mechanism. This would represent a major step for the studies of the origin and evolution of stellar populations.

  6. Diffusion and Mixing in Globular Clusters

    Science.gov (United States)

    Meiron, Yohai; Kocsis, Bence

    2018-03-01

    Collisional relaxation describes the stochastic process with which a self-gravitating system near equilibrium evolves in phase-space due to the fluctuating gravitational field of the system. The characteristic timescale of this process is called the relaxation time. In this paper, we highlight the difference between two measures of the relaxation time in globular clusters: (1) the diffusion time with which the isolating integrals of motion (i.e., energy E and angular momentum magnitude L) of individual stars change stochastically and (2) the asymptotic timescale required for a family of orbits to mix in the cluster. More specifically, the former corresponds to the instantaneous rate of change of a star’s E or L, while the latter corresponds to the timescale for the stars to statistically forget their initial conditions. We show that the diffusion timescales of E and L vary systematically around the commonly used half-mass relaxation time in different regions of the cluster by a factor of ∼10 and ∼100, respectively, for more than 20% of the stars. We define the mixedness of an orbital family at any given time as the correlation coefficient between its E or L probability distribution functions and those of the whole cluster. Using Monte Carlo simulations, we find that mixedness converges asymptotically exponentially with a decay timescale that is ∼10 times the half-mass relaxation time.

  7. Extreme Tolerance to Elevated Pressure in a Thermococcus isolate from the Mid-Cayman Rise

    Science.gov (United States)

    Narasingarao, P.; Huber, J. A.; Schrenk, M. O.; Bartlett, D.

    2013-12-01

    Hydrothermal systems are windows into the deep biosphere. Venting fluids with temperatures up to 400°C containing gases such as H2, CO2, H2S and CH4 provide an oasis of life in the deep ocean primarily based on chemosynthesis. The Mid-Cayman Rise (MCR) includes the deepest hydrothermal vent system known thus far, and is characterized by two venting sites Piccard (4950m) and Von Damm (2350m). Here we demonstrate the remarkable high pressure tolerance limits of a Thermococcus sp. designated strain 175, isolated from samples collected from Piccard during an expedition in 2012. Diffuse venting fluids collected at the site resulted in the isolation of several Thermococcus strains capable of growth in basal salts medium supplemented with H2/CO2 and yeast extract, along with sulfur as an electron acceptor. Given the importance of pressure as an environmental parameter influencing evolution and adaptation of deep-sea life, the pressure tolerance of Thermococcus strain 175 was tested. High pressure incubations were originally conducted in serum vials filled completely with growth medium and therefore lacking all headspace gas. To test for growth with H2/CO2 , modified hungate tubes with a piston mechanism were used (Bowles et al. 2011) . The results indicate that strain 175 can grow at 90°C up to 120 megapascal (MPa). Growth rates are comparable when the strain is grown at atmospheric pressure or at 120 MPa pressure. Morphologically, the strain is irregular cocci and does not show any changes in its cellular structure when switched between atmospheric pressure and elevated pressure. This wide range of pressure tolerance has not been previously observed in other microorganisms, including Pyrococcus yayanosii CH1 (Zeng et al., 2009) which is also capable of growth at 120MPa but does not grow below 15 MPa. Thermococcus strain 175 represents an excellent model system to study high pressure adaptation due to its high growth rate and broad range of growth pressures. The

  8. Actinopolyspora lacussalsi sp. nov., an extremely halophilic actinomycete isolated from a salt lake.

    Science.gov (United States)

    Guan, Tong-Wei; Wei, Bei; Zhang, Yao; Xia, Zhan-Fen; Che, Zhen-Ming; Chen, Xiang-Gui; Zhang, Li-Li

    2013-08-01

    A novel halophilic, filamentous actinobacterium, designated strain TRM 40139(T), was isolated from a hypersaline habitat in Xinjiang Province, north-west China. Its taxonomic status was determined using a polyphasic approach. Phylogenetic analysis based on the almost-complete 16S rRNA gene sequence of the strain showed that it formed a well-separated sub-branch within the radiation of the genus Actinopolyspora and the organism was related most closely to the type strains of Actinopolyspora alba (97.6 % similarity), Actinopolyspora xinjiangensis (97.6 %) and Actinopolyspora erythraea (97.1 %). However, it had relatively lower mean DNA-DNA relatedness values with the above strains (36.4, 31.3 and 26.1 %, respectively). Optimal growth occurred at 35 °C, at pH 7.0 and in the presence of 12 % (w/v) NaCl. The whole-cell sugar pattern consisted of xylose, glucose, ribose and arabinose. The major fatty acids were iso-C16 : 0 (28.0 %) and anteiso-C17 : 0 (27.6 %). The diagnostic phospholipids detected were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylinositol and two unknown phospholipids. The predominant menaquinones were MK-9(H4) (49.8 %) and MK-10(H4) (24.2 %). The G+C content of the genomic DNA was 66.4 mol%. Strain TRM 40139(T) therefore represents a novel species of the genus Actinopolyspora, for which the name Actinopolyspora lacussalsi sp. nov. is proposed. The type strain is TRM 40139(T) (= KCTC 19657(T) = CCTCC AA 2012020(T)).

  9. Haloterrigena daqingensis sp. nov., an extremely haloalkaliphilic archaeon isolated from a saline-alkaline soil.

    Science.gov (United States)

    Wang, Shuang; Yang, Qian; Liu, Zhi-Hua; Sun, Lei; Wei, Dan; Zhang, Jun-Zheng; Song, Jin-Zhu; Yuan, Hai-Feng

    2010-10-01

    A haloalkaliphilic archaeon, strain JX313(T), was isolated from a saline-alkaline soil from Daqing, Heilongjiang Province, China. Its morphological, physiological and biochemical features and 16S rRNA gene sequence were determined. Colonies of the strain were orange-red and cells were non-motile cocci and Gram-stain-variable. The strain required at least 1.7 M NaCl for growth, with optimal growth occurring in 2.0-2.5 M NaCl. Growth was observed at 20-50°C and pH 8.0-10.5, with optimal growth at 35°C and pH 10.0. The G+C content of its genomic DNA was 59.3 mol%. Phylogenetic analysis of 16S rRNA gene sequences showed that strain JX313(T) is associated with the genera Haloterrigena and Natrinema and is most closely related to Haloterrigena salina XH-65(T) (96.2  % sequence similarity) and Haloterrigena hispanica FP1(T) (96.2 %). DNA-DNA hybridization experiments revealed that the relatedness of strain JX313(T) to type strains of related species of the genus Haloterrigena or Natrinema was less than 50 %. Furthermore, the cellular polar lipids of strain JX313(T), identified as phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and mannose-2,6-disulfate (1→2)-glucose glycerol diether (S₂-DGD), were consistent with the polar lipid characteristics of the genus Haloterrigena. Therefore, phylogenetic analysis, phenotypic assessment and chemotaxonomic data showed that JX313(T) represents a novel species within the genus Haloterrigena, for which the name Haloterrigena daqingensis sp. nov. is proposed. The type strain is JX313(T) (=CGMCC 1.8909(T) =NBRC 105739(T)).

  10. Spatial genetic diversity in the Cape mole-rat, Georychus capensis: Extreme isolation of populations in a subterranean environment.

    Science.gov (United States)

    Visser, Jacobus H; Bennett, Nigel C; Jansen van Vuuren, Bettine

    2018-01-01

    The subterranean niche harbours animals with extreme adaptations. These adaptations decrease the vagility of taxa and, along with other behavioural adaptations, often result in isolated populations characterized by small effective population sizes, high inbreeding, population bottlenecks, genetic drift and consequently, high spatial genetic structure. Although information is available for some species, estimates of genetic diversity and whether this variation is spatially structured, is lacking for the Cape mole-rat (Georychus capensis). By adopting a range-wide sampling regime and employing two variable mitochondrial markers (cytochrome b and control region), we report on the effects that life-history, population demography and geographic barriers had in shaping genetic variation and population genetic patterns in G. capensis. We also compare our results to information available for the sister taxon of the study species, Bathyergus suillus. Our results show that Georychus capensis exhibits low genetic diversity relative to the concomitantly distributed B. suillus, most likely due to differences in habitat specificity, habitat fragmentation and historical population declines. In addition, the isolated nature of G. capensis populations and low levels of population connectivity has led to small effective population sizes and genetic differentiation, possibly aided by genetic drift. Not surprisingly therefore, G. capensis exhibits pronounced spatial structure across its range in South Africa. Along with geographic distance and demography, other factors shaping the genetic structure of G. capensis include the historical and contemporary impacts of mountains, rivers, sea-level fluctuations and elevation. Given the isolation and differentiation among G. capensis populations, the monotypic genus Georychus may represent a species complex.

  11. Halobellus rufus sp. nov., an extremely halophilic archaeon isolated from non-purified solar salt.

    Science.gov (United States)

    Cha, In-Tae; Yim, Kyung June; Song, Hye Seon; Lee, Hae-Won; Hyun, Dong-Wook; Kim, Kil-Nam; Seo, Myung-Ji; Kim, Daekyung; Choi, Jong-Soon; Lee, Sung-Jae; Bae, Jin-Woo; Rhee, Sung-Keun; Choi, Hak-Jong; Rhee, Jin-Kyu; Nam, Young-Do; Roh, Seong Woon

    2014-05-01

    A halophilic archaeon, designed strain CBA1103(T), was isolated from non-purified solar salt. The cells of strain CBA1103(T) were observed to be Gram-stain negative and pleomorphic, and the colonies appear red. Strain CBA1103(T) was observed to grow between 20 and 55 °C (optimum 37 °C), and in NaCl concentrations of 10-30 % (w/v) (optimum 15 %) with 0-0.5 M MgSO4·7H2O (optimum 0.1 M) and at pH 6.0-9.0 (optimum pH 7.0). Additionally, the cells lyse in distilled water. The major polar lipids of strain CBA1103(T) are phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and two glycolipids chromatographically identical to sulfated mannosyl glucosyl diether and manosyl glucosyl diether. Strain CBA1103(T) is shown to belong to the Halobellus genus and exhibits similarity to related taxa; the 16S rRNA gene sequence similarity between strain CBA1103(T) and Halobellus rarus 18362(T), Hbs. limi 16811(T), Hbs. litoreus JCM 17118(T), Hbs. inordinatus YC20(T), Hbs. clavatus TNN18(T) and Hbs. salinus CSW2.24.4(T) is 97.3, 96.5, 96.5, 94.5, 94.5 and 93.7 %, respectively. The RNA polymerase subunit B gene sequence of strain CBA1103(T) shows 93.7 % similarity with the sequence of Hbs. litoreus JCM 17118(T); the similarity is lower with sequences from the type strains of other species of Halobellus. The genomic DNA G+C content of strain CBA1103(T) was determined to be 67.0 mol% a value which is in the range of the genomic DNA G+C content of members of the genus Halobellus (61.5-69.2 mol%). These results suggest that strain CBA1103(T) should be considered to represent a new taxon for which the name Halobellus rufus sp. nov. is proposed, with the type strain CBA1103(T) (=CECT 8423(T) =JCM 19434(T)).

  12. Binary Black Hole Mergers from Globular Clusters: Implications for Advanced LIGO.

    Science.gov (United States)

    Rodriguez, Carl L; Morscher, Meagan; Pattabiraman, Bharath; Chatterjee, Sourav; Haster, Carl-Johan; Rasio, Frederic A

    2015-07-31

    The predicted rate of binary black hole mergers from galactic fields can vary over several orders of magnitude and is extremely sensitive to the assumptions of stellar evolution. But in dense stellar environments such as globular clusters, binary black holes form by well-understood gravitational interactions. In this Letter, we study the formation of black hole binaries in an extensive collection of realistic globular cluster models. By comparing these models to observed Milky Way and extragalactic globular clusters, we find that the mergers of dynamically formed binaries could be detected at a rate of ∼100 per year, potentially dominating the binary black hole merger rate. We also find that a majority of cluster-formed binaries are more massive than their field-formed counterparts, suggesting that Advanced LIGO could identify certain binaries as originating from dense stellar environments.

  13. The evolution of extreme shell shape variation in the land snail Ainohelix editha: a phylogeny and hybrid zone analysis.

    Science.gov (United States)

    Teshima, Hiroaki; Davison, Angus; Kuwahara, Yasuhiro; Yokoyama, Jun; Chiba, Satoshi; Fukuda, Tatsuya; Ogimura, Hideo; Kawata, Masakado

    2003-07-01

    Ainohelix editha from Hokkaido, Japan, exhibit great geographical variation in their shell morphology. In particular, A. editha in two quite separate locations, Shimamaki and Samani, are striking because they are extremely flat and have a sharp keel, whereas at adjacent sites the shells are globular or depressed-globular. We used mitochondrial 16S rRNA and nuclear ITS-2 sequences to infer a phylogeny among 47 snails from 29 locations. Snails from the two keeled-flat populations clustered separately in the phylogeny, suggesting that this unusual shell form could have evolved independently. A morphological analysis of shells collected along a transect between keeled-flat and globular snail sites showed a cline for shell shape and the angle of the keel. Two different mtDNA lineages were found across the transect, with a cline for an ITS-2 single nucleotide polymorphism. Together, the results may suggest a lack of reproductive isolation between keeled-flat and globular snails, with possible introgression by hybridization.

  14. Gamma-ray Emission from Globular Clusters

    Directory of Open Access Journals (Sweden)

    Pak-Hin T. Tam

    2016-03-01

    Full Text Available Over the last few years, the data obtained using the Large Area Telescope (LAT aboard the Fermi Gamma-ray Space Telescope has provided new insights on high-energy processes in globular clusters, particularly those involving compact objects such as MilliSecond Pulsars (MSPs. Gamma-ray emission in the 100 MeV to 10 GeV range has been detected from more than a dozen globular clusters in our galaxy, including 47 Tucanae and Terzan 5. Based on a sample of known gammaray globular clusters, the empirical relations between gamma-ray luminosity and properties of globular clusters such as their stellar encounter rate, metallicity, and possible optical and infrared photon energy densities, have been derived. The measured gamma-ray spectra are generally described by a power law with a cut-off at a few gigaelectronvolts. Together with the detection of pulsed γ-rays from two MSPs in two different globular clusters, such spectral signature lends support to the hypothesis that γ-rays from globular clusters represent collective curvature emission from magnetospheres of MSPs in the clusters. Alternative models, involving Inverse-Compton (IC emission of relativistic electrons that are accelerated close to MSPs or pulsar wind nebula shocks, have also been suggested. Observations at >100 GeV by using Fermi/LAT and atmospheric Cherenkov telescopes such as H.E.S.S.-II, MAGIC-II, VERITAS, and CTA will help to settle some questions unanswered by current data.

  15. “Streptomyces massilialgeriensis” sp. nov., a new bacterial species isolated from an extremely saline soil collected from the dry lake of Ank el Djamel in Algeria

    Directory of Open Access Journals (Sweden)

    C.E. Djaballah

    2018-01-01

    Full Text Available We report here the main characteristics of “Streptomyces massilialgeriensis” strain S35T (CSUR = P3927, a new bacterial species within the Streptomyces genus, isolated from an extremely saline soil sample collected from the site of Garaet Ank Djemel in the Wilaya of Oum El Bouaghi, Algeria.

  16. A 48 kDa collagen-binding phosphoprotein isolated from bovine aortic endothelial cells interacts with the collagenous domain, but not the globular domain, of collagen type IV.

    Science.gov (United States)

    Yannariello-Brown, J; Madri, J A

    1990-01-15

    We have identified collagen-binding proteins in detergent extracts of metabolically labelled bovine aortic endothelial cells (BAEC) by collagen type IV-Sepharose affinity chromatography. The major collagen type IV-binding protein identified by SDS/PAGE had a molecular mass of 48 kDa, which we term the 'collagen-binding 48 kDa protein' (CB48). The pI of CB48 was 8.0-8.3 in a two-dimensional gel system, running non-equilibrium pH gel electrophoresis in the first dimension and SDS/PAGE in the second dimension. Under these conditions CB48 separated into two major (a and b) and one minor isoform (c); a was the most basic of the three isoforms. Two-dimensional chymotryptic peptide maps derived from each individual isoform were virtually identical. The charge differences between the isoforms were due in part to differential H3(32)PO4 incorporation by the protein. CB48 bound to intact collagen type IV and the collagenous region of collagen type IV, but not to the globular NC1 domain. Cell-surface labelling and indirect immunofluorescence experiments localized the bulk of CB48 intracellularly in the endoplasmic reticulum Golgi region, with a minor population of molecules on the cell surface. A specific rabbit polyclonal anti-CB48 serum did not inhibit the attachment or spreading of BAEC to collagen type IV in an 'in vitro' adhesion assay, suggesting that the cell-surface population of CB48 is not involved in BAEC adhesion. We conclude that CB48 is a collagen-binding phosphoprotein that interacts with the collagenous domain of collagen type IV and may be involved in intracellular transport of collagen molecules.

  17. The Most Massive Star Clusters: Supermassive Globular Clusters or Dwarf Galaxy Nuclei?

    Science.gov (United States)

    Harris, William

    2004-07-01

    Evidence is mounting that the most massive globular clusters, such as Omega Centauri and M31-G1, may be related to the recently discovered "Ultra-Compact Dwarfs" and the dense nuclei of dE, N galaxies. However, no systematic imaging investigation of these supermassive globular clusters - at the level of Omega Cen and beyond - has been done, and we do not know what fraction of them might bear the signatures {such as large effective radii or tidal tails} of having originated as dE nuclei. We propose to use the ACS/WFC to obtain deep images of 18 such clusters in NGC 5128 and M31, the two nearest rich globular cluster systems. These globulars are the richest star clusters that can be found in nature, the biggest of them reaching 10^7 Solar masses, and they are likely to represent the results of star formation under the densest and most extreme conditions known. Using the profiles of the clusters including their faint outer envelopes, we will carry out state-of-the-art dynamical modelling of their structures, and look for any clear evidence which would indicate that they are associated with stripped satellites. This study will build on our previous work with STIS and WFPC2 imaging designed to study the 'Fundamental Plane' of globular clusters. When our new work is combined with Archival WFPC2, STIS, and ACS material, we will also be able to construct the definitive mapping of the Fundamental Plane of globular clusters at its uppermost mass range, and confirm whether or not the UCD and dE, N objects occupy a different structural parameter space.

  18. Halorientalis persicus sp. nov., an extremely halophilic archaeon isolated from a salt lake and emended description of the genus Halorientalis.

    Science.gov (United States)

    Amoozegar, Mohammad Ali; Makhdoumi-Kakhki, Ali; Mehrshad, Maliheh; Fazeli, Seyed Abolhassan Shahzadeh; Spröer, Cathrin; Ventosa, Antonio

    2014-03-01

    An extremely halophilic archaeon, strain D108(T), was isolated from a brine sample of Aran-Bidgol salt lake in Iran. The novel strain was cream-pigmented, motile, pleomorphic rod-shaped and required at least 2.5 M NaCl but not MgCl2 for growth. Optimal growth was achieved with 4.3 M NaCl and 0.1 M MgCl2. The optimum pH and temperature for growth were pH 7.5 and 40 °C, respectively, and the strain was able to grow over a pH range of 6.5 to 9.0, and a temperature range of 30 to 50 °C. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strain D108(T) clustered with the type strain of the sole species of the genus Halorientalis, Halorientalis regularis TNN28(T), with a sequence similarity of 98.8 %. The polar lipid pattern of strain D108(T) consisted of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, one phosphoglycolipid and two glycolipids. The only quinone present was MK-8(II-H2). The DNA G+C content of strain D108(T) was 62.8 mol%. DNA-DNA hybridization studies (45 % with Halorientalis regularis IBRC-M 10760(T)), as well as biochemical and physiological characterization, allowed strain D108(T) to be differentiated from Halorientalis regularis. A novel species of the genus Halorientalis, Halorientalis persicus sp. nov., is therefore proposed to accommodate this strain. The type strain is D108(T) ( = IBRC-M 10043(T) = CECT 8375(T)). An emended description of the genus Halorientalis is also proposed.

  19. QUIESCENT ISOLATION: THE EXTREMELY EXTENDED H I HALO OF THE OPTICALLY COMPACT DWARF GALAXY ADBS 113845+2008

    International Nuclear Information System (INIS)

    Cannon, John M.; Salzer, John J.; Rosenberg, Jessica L.

    2009-01-01

    We present new optical imaging and spectroscopy and H I spectral line imaging of the dwarf galaxy ADBS 113845 + 2008 (hereafter ADBS 1138). This metal-poor (Z ∼ 30% Z sun ), 'post-starburst' system has one of the most compact stellar distributions known in any galaxy to date (B-band exponential scale length = 0.57 kpc). In stark contrast to the compact stellar component, the neutral gas is extremely extended; H I is detected to a radial distance of ∼25 kpc at the 10 19 cm -2 level (∼> 44 B-band scale lengths). Comparing to measurements of similar 'giant disk' dwarf galaxies in the literature, ADBS 1138 has the largest known H I-to-optical size ratio. The stellar component is located near the center of a broken ring of H I that is ∼15 kpc in diameter; column densities peak in this structure at the ∼3.5 x 10 20 cm -2 level. At the center of this ring, in a region of comparatively low H I column density, we find ongoing star formation traced by Hα emission. We sample the rotation curve to the point of turn over; this constrains the size of the dark matter halo of the galaxy, which outweighs the luminous component (stars + gas) by at least a factor of 15. To explain these enigmatic properties, we examine 'inside-out' and 'outside-in' evolutionary scenarios. Calculations of star formation energetics indicate that 'feedback' from concentrated star formation is not capable of producing the ring structure; we posit that this is a system where the large H I disk is evolving in quiescent isolation. In a global sense, this system is exceedingly inefficient at converting neutral gas into stars.

  20. Stellar black holes in globular clusters

    Science.gov (United States)

    Kulkarni, S. R.; Hut, Piet; Mcmillan, Steve

    1993-01-01

    The recent discovery of large populations of millisec pulsars associated with neutron stars in globular clusters indicates that several hundred stellar black holes of about 10 solar masses each can form within a typical cluster. While, in clusters of high central density, the rapid dynamical evolution of the black-hole population leads to an ejection of nearly all holes on a short timescale, systems of intermediate density may involve a normal star's capture by one of the surviving holes to form a low-mass X-ray binary. One or more such binaries may be found in the globular clusters surrounding our galaxy.

  1. Tidal evolution of globular clusters. I - Method

    Science.gov (United States)

    Oh, K. S.; Lin, D. N. C.; Aarseth, S. J.

    1992-01-01

    Tidal evolution of globular clusters is regulated by both Galactic tidal effects and internal relaxation processes. In order to investigate the tidal evolution of globular clusters, a numerical scheme which utilizes a Fokker-Planck approach as well as direct numerical integration of the restricted three-body problem is developed. In the inner regions of the cluster, stellar orbits are mapped with the cluster's gravitational potential and orbit-averaged diffusion coefficients. In the outer regions, the Galactic tidal field is explicitly included in the direct orbital integration. This method is presented here with some tests on King-Michie models.

  2. Shaping Globular Clusters with Black Holes

    Science.gov (United States)

    Kohler, Susanna

    2018-03-01

    How many black holes lurk within the dense environments of globular clusters, and how do these powerful objects shape the properties of the cluster around them? One such cluster, NGC 3201, is now helping us to answer these questions.Hunting Stellar-Mass Black HolesSince the detection of merging black-hole binaries by the Laser Interferometer Gravitational-Wave Observatory (LIGO), the dense environments of globular clusters have received increasing attention as potential birthplaces of these compact binary systems.The central region of the globular star cluster NGC 3201, as viewed by Hubble. The black hole is in orbit with the star marked by the blue circle. [NASA/ESA]In addition, more and more stellar-mass black-hole candidates have been observed within globular clusters, lurking in binary pairs with luminous, non-compact companions. The most recent of these detections, found in the globular cluster NGC 3201, stands alone as the first stellar-mass black hole candidate discovered via radial velocity observations: the black holes main-sequence companion gave away its presence via a telltale wobble.Now a team of scientists led by Kyle Kremer (CIERA and Northwestern University) is using models of this system to better understand the impact that black holes might have on their host clusters.A Model ClusterThe relationship between black holes and their host clusters is complicated. Though the cluster environment can determine the dynamical evolution of the black holes, the retention rate of black holes in a globular cluster (i.e., how many remain in the cluster when they are born as supernovae, rather than being kicked out during the explosion) influences how the host cluster evolves.Kremer and collaborators track this complex relationship by modeling the evolution of a cluster similar to NGC 3201 with a Monte Carlo code. The code incorporates physics relevant to the evolution of black holes and black-hole binaries in globular clusters, such as two-body relaxation

  3. Isolation of Novel Extreme-Tolerant Cyanobacteria from a Rock-Dwelling Microbial Community by Using Exposure to Low Earth Orbit▿ †

    Science.gov (United States)

    Olsson-Francis, Karen; de la Torre, Rosa; Cockell, Charles S.

    2010-01-01

    Many cyanobacteria are known to tolerate environmental extremes. Motivated by an interest in selecting cyanobacteria for applications in space, we launched rocks from a limestone cliff in Beer, Devon, United Kingdom, containing an epilithic and endolithic rock-dwelling community of cyanobacteria into low Earth orbit (LEO) at a height of approximately 300 kilometers. The community was exposed for 10 days to isolate cyanobacteria that can survive exposure to the extreme radiation and desiccating conditions associated with space. Culture-independent (16S rRNA) and culture-dependent methods showed that the cyanobacterial community was composed of Pleurocapsales, Oscillatoriales, and Chroococcales. A single cyanobacterium, a previously uncharacterized extremophile, was isolated after exposure to LEO. We were able to isolate the cyanobacterium from the limestone cliff after exposing the rock-dwelling community to desiccation and vacuum (0.7 × 10−3 kPa) in the laboratory. The ability of the organism to survive the conditions in space may be linked to the formation of dense colonies. These experiments show how extreme environmental conditions, including space, can be used to select for novel microorganisms. Furthermore, it improves our knowledge of environmental tolerances of extremophilic rock-dwelling cyanobacteria. PMID:20154120

  4. Occurrence of resistance to antibiotics, UV-B, and arsenic in bacteria isolated from extreme environments in high-altitude (above 4400 m) Andean wetlands.

    Science.gov (United States)

    Dib, Julián; Motok, Jessica; Zenoff, Verónica Fernández; Ordoñez, Omar; Farías, María Eugenia

    2008-05-01

    High-altitude Andean wetlands are pristine environments with extreme conditions such as high UV radiation, high heavy metal content (mainly arsenic), high salinity, and oligotrophy. In this paper, the UV-B resistance and tolerance to arsenic of phylogenetically characterized bacteria (Actinobacteria [six isolates], Firmicutes [four isolates], and gamma-Proteobacteria [three isolates]) isolated from Laguna Vilama (4400-m altitude) and Laguna Azul (4560 m) were determined. In addition, given that multiple antibiotic resistances were also determined, a relationship between antibiotic resistances as a consequence of mutagenic ability or in relation to metal resistance is proposed. High UV-B resistances were found, since after 30 min (0.7 KJ m(-2)) and 60 min (1.4 KJ m(-2)) of irradiation, most of the studied bacteria did not show a decreased survival; what is more, many of them had an improved survival with the increased doses. Augmentations in mutagenesis rates were observed after UV-B irradiation in only 4 of the 13 tested isolates. Arsenite tolerance was also established in 8 of the 13 tested strains: Staphylococcus saprophyticus A3 and Micrococcus sp. A7, which were able to grow in media containing up to 10 mM As(III). Finally, predominance of antibiotic resistances (azithromycin, erythromycin, clarithromycin, roxithromycin, streptomycin, chloramphenicol, gentamycin, kanamycin, tetracycline, and ampicillin) was found, in all the isolated strains from both wetlands, with unexpectedly high minimal inhibitory concentrations (MICs; >2 mg mL(-1)) for macrolides. These results demonstrate that in extreme environments like high-altitude wetlands there is a correlation of multiresistances to UV-B radiation and arsenic, and that antibiotic resistances are also widespread in these pristine environments, where antibiotic selective pressure is supposed to be absent.

  5. Chemical abundances in the old LMC globular cluster Hodge 11

    Science.gov (United States)

    Mateluna, R.; Geisler, D.; Villanova, S.; Carraro, G.; Grocholski, A.; Sarajedini, A.; Cole, A.; Smith, V.

    2012-12-01

    Context. The study of globular clusters is one of the most powerful ways to learn about a galaxy's chemical evolution and star formation history. They preserve a record of chemical abundances at the time of their formation and are relatively easy to age date. The most detailed knowledge of the chemistry of a star is given by high resolution spectroscopy, which provides accurate abundances for a wide variety of elements, yielding a wealth of information on the various processes involved in the cluster's chemical evolution. Aims: We studied red giant branch (RGB) stars in an old, metal-poor globular cluster of the Large Magellanic Cloud (LMC), Hodge 11 (H11), in order to measure as many elements as possible. The goal is to compare its chemical trends to those in the Milky Way halo and dwarf spheroidal galaxies in order to help understand the formation history of the LMC and our own Galaxy. Methods: We have obtained high resolution VLT/FLAMES spectra of eight RGB stars in H11. The spectral range allowed us to measure a variety of elements, including Fe, Mg, Ca, Ti, Si, Na, O, Ni, Cr, Sc, Mn, Co, Zn, Ba, La, Eu and Y. Results: We derived a mean [Fe/H] = -2.00 ± 0.04, in the middle of previous determinations. We found low [α/Fe] abundances for our targets, more comparable to values found in dwarf spheroidal galaxies than in the Galactic halo, suggesting that if H11 is representative of its ancient populations then the LMC does not represent a good halo building block. Our [Ca/Fe] value is about 0.3 dex less than that of halo stars used to calibrate the Ca IR triplet technique for deriving metallicity. A hint of a Na abundance spread is observed. Its stars lie at the extreme high O, low Na end of the Na:O anti-correlation displayed by Galactic and LMC globular clusters. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (proposal ID 082.B-0458).Table 4 is only available in electronic form at http://www.aanda.org

  6. Infrared dust emission from globular clusters

    International Nuclear Information System (INIS)

    Angeletti, L.; Capuzzo-Dolcetta, R.; Giannone, P.; Blanco, A.; Bussoletti, E.

    1982-01-01

    The implications of the presence of a central cloud in the cores of globular clusters were investigated recently. A possible mechanism of confinement of dust in the central region of our cluster models was also explored. The grain temperature and infrared emission have now been computed for rather realistic grain compositions. The grain components were assumed to be graphite and/or silicates. The central clouds turned out to be roughly isothermal. The wavelengths of maximum emission came out to be larger than 20 μm in all studied cases. An application of the theoretical results to five globular clusters showed that the predictable infrared emission for 47 Tuc, M4 and M22 should be detectable by means of present instrumentation aboard flying platforms. (author)

  7. Chemical Abundances of Giants in Globular Clusters

    Science.gov (United States)

    Gratton, Raffaele G.; Bragaglia, Angela; Carretta, Eugenio; D'Orazi, Valentina; Lucatello, Sara

    A large fraction of stars form in clusters. According to a widespread paradigma, stellar clusters are prototypes of single stellar populations. According to this concept, they formed on a very short time scale, and all their stars share the same chemical composition. Recently it has been understood that massive stellar clusters (the globular clusters) rather host various stellar populations, characterized by different chemical composition: these stellar populations have also slightly different ages, stars of the second generations being formed from the ejecta of part of those of an earlier one. Furthermore, it is becoming clear that the efficiency of the process is quite low: many more stars formed within this process than currently present in the clusters. This implies that a significant, perhaps even dominant fraction of the ancient population of galaxies formed within the episodes that lead to formation the globular clusters.

  8. VARIABLES IN GLOBULAR CLUSTER NGC 5024

    Energy Technology Data Exchange (ETDEWEB)

    Safonova, M.; Stalin, C. S., E-mail: rita@iiap.res.in, E-mail: stalin@iiap.res.in [Indian Institute of Astrophysics, Koramangala, Bangalore 560 034 (India)

    2011-12-15

    We present the results of a commissioning campaign to observe Galactic globular clusters for the search of microlensing events. The central 10' Multiplication-Sign 10' region of the globular cluster NGC 5024 was monitored using the 2 m Himalayan Chandra Telescope in R-band for a period of about 8 hr on 2010 March 24. Light curves were obtained for nearly 10,000 stars using a modified Differential Image Analysis technique. We identified all known variables within our field of view and revised the periods and status of some previously reported short-period variables. We report about 70 new variable sources and present their equatorial coordinates, periods, light curves, and possible types. Out of these, 15 are SX Phe stars, 10 are W UMa-type stars, and 14 are probable RR Lyrae stars. Nine of the newly discovered SX Phe stars and one eclipsing binary belong to the blue straggler star population.

  9. Globular Cluster Tidal Streams: An Observational Study

    Science.gov (United States)

    Powell, William L.; Lauchner, A.; Wilhelm, R.; McWilliam, A.

    2006-12-01

    Globular cluster tidal streams are of interest for what they can tell us of the dynamical evolution of the clusters and of our Galaxy. Recent studies have used photometric and statistical subtraction methods to attempt to separate potential streams from the field stars that contaminate the samples. We chose instead as our primary method to use photometry to select blue stars that match the horizontal branch of the clusters. We then make spectroscopic observations of these candidates to determine their metallicity and radial velocities. Combining these results with the photometric data offers a better picture of the structure and validity of tidal streams. We present photometric and spectroscopic results for several globular clusters and their surrounding fields. Data were obtained at McDonald Observatory, Kitt Peak, and Las Campanas Observatory. SDSS data were also used. WLP acknowledges the support of a Sigma Xi Grant-In-Aid of research. RW acknowledges the support of a AAS Small Research Grant.

  10. Radionuclide leakage monitoring during hyperthermic isolated limb perfusion for treatment of local melanoma metastasis in an extremity

    DEFF Research Database (Denmark)

    Paulsen, Ida F; Chakera, Annette Hougaard; Schmidt, Grethe

    2015-01-01

    perfusions performed in 115 consecutive patients (77 women and 38 men; median age 66 years) with recurrent and/or clinically apparent, cutaneous or subcutaneous melanoma metastases in an extremity. Radionuclide monitoring was performed with continuous, precordial count rate determinations of an intravascular...

  11. The Effects of Exhaustive Military Activities in Man. The Performance of Small Isolated Military Units in Extreme Environmental Conditions

    Science.gov (United States)

    2001-03-01

    functions Regular body functions are of importance for anybody in an extreme climate. Constipation is very often a problem at the beginning of any...groups problems may arise. One of the remedies is to let everybody do his share. If the total work load is low, any workload how small it is may be a

  12. Pyroelectricity in globular protein lysozyme films

    Science.gov (United States)

    Stapleton, A.; Noor, M. R.; Haq, E. U.; Silien, C.; Soulimane, T.; Tofail, S. A. M.

    2018-03-01

    Pyroelectricity is the ability of certain non-centrosymmetric materials to generate an electric charge in response to a change in temperature and finds use in a range of applications from burglar alarms to thermal imaging. Some biological materials also exhibit pyroelectricity but the examples of the effect are limited to fibrous proteins, polypeptides, and tissues and organs of animals and plants. Here, we report pyroelectricity in polycrystalline aggregate films of lysozyme, a globular protein.

  13. Statistical interior properties of globular proteins

    International Nuclear Information System (INIS)

    Zhou-Ting, Jiang; Tai-Quan, Wu; Lin-Xi, Zhang; Ting-Ting, Sun

    2009-01-01

    The character of forming long-range contacts affects the three-dimensional structure of globular proteins deeply. As the different ability to form long-range contacts between 20 types of amino acids and 4 categories of globular proteins, the statistical properties are thoroughly discussed in this paper. Two parameters N C and N D are defined to confine the valid residues in detail. The relationship between hydrophobicity scales and valid residue percentage of each amino acid is given in the present work and the linear functions are shown in our statistical results. It is concluded that the hydrophobicity scale defined by chemical derivatives of the amino acids and nonpolar phase of large unilamellar vesicle membranes is the most effective technique to characterise the hydrophobic behavior of amino acid residues. Meanwhile, residue percentage P i and sequential residue length L i of a certain protein i are calculated under different conditions. The statistical results show that the average value of P i as well as L i of all-α proteins has a minimum among these 4 classes of globular proteins, indicating that all-α proteins are hardly capable of forming long-range contacts one by one along their linear amino acid sequences. All-β proteins have a higher tendency to construct long-range contacts along their primary sequences related to the secondary configurations, i.e. parallel and anti-parallel configurations of β sheets. The investigation of the interior properties of globular proteins give us the connection between the three-dimensional structure and its primary sequence data or secondary configurations, and help us to understand the structure of protein and its folding process well. (cross-disciplinary physics and related areas of science and technology)

  14. Exploring the Internal Dynamics of Globular Clusters

    Science.gov (United States)

    Watkins, Laura L.; van der Marel, Roeland; Bellini, Andrea; Luetzgendorf, Nora; HSTPROMO Collaboration

    2018-01-01

    Exploring the Internal Dynamics of Globular ClustersThe formation histories and structural properties of globular clusters are imprinted on their internal dynamics. Energy equipartition results in velocity differences for stars of different mass, and leads to mass segregation, which results in different spatial distributions for stars of different mass. Intermediate-mass black holes significantly increase the velocity dispersions at the centres of clusters. By combining accurate measurements of their internal kinematics with state-of-the-art dynamical models, we can characterise both the velocity dispersion and mass profiles of clusters, tease apart the different effects, and understand how clusters may have formed and evolved.Using proper motions from the Hubble Space Telescope Proper Motion (HSTPROMO) Collaboration for a set of 22 Milky Way globular clusters, and our discrete dynamical modelling techniques designed to work with large, high-quality datasets, we are studying a variety of internal cluster properties. We will present the results of theoretical work on simulated clusters that demonstrates the efficacy of our approach, and preliminary results from application to real clusters.

  15. Isolation and characterization of biosurfactant production under extreme environmental conditions by alkali-halo-thermophilic bacteria from Saudi Arabia.

    Science.gov (United States)

    Elazzazy, Ahmed M; Abdelmoneim, T S; Almaghrabi, O A

    2015-07-01

    Twenty three morphologically distinct microbial colonies were isolated from soil and sea water samples, which were collected from Jeddah region, Saudi Arabia for screening of the most potent biosurfactant strains. The isolated bacteria were selected by using different methods as drop collapse test, oil displacement test, blue agar test, blood hemolysis test, emulsification activity and surface tension. The results showed that the ability of Virgibacillus salarius to grow and reduce surface tension under a wide range of pH, salinities and temperatures gives bacteria isolate an advantage in many applications such as pharmaceutical, cosmetics, food industries and bioremediation in marine environment. The biosurfactant production by V. salarius decreased surface tension and emulsifying activity (30 mN/m and 80%, respectively). In addition to reducing the production cost of biosurfactants by tested several plant-derived oils such as jatropha oil, castor oils, jojoba oil, canola oil and cottonseed oil. In this respect the feasibility to reusing old frying oil of sunflower for production rhamnolipids and sophorolipids, their use that lead to solve many ecological and industrial problems.

  16. Isolation and characterization of biosurfactant production under extreme environmental conditions by alkali-halo-thermophilic bacteria from Saudi Arabia

    Science.gov (United States)

    Elazzazy, Ahmed M.; Abdelmoneim, T.S.; Almaghrabi, O.A.

    2014-01-01

    Twenty three morphologically distinct microbial colonies were isolated from soil and sea water samples, which were collected from Jeddah region, Saudi Arabia for screening of the most potent biosurfactant strains. The isolated bacteria were selected by using different methods as drop collapse test, oil displacement test, blue agar test, blood hemolysis test, emulsification activity and surface tension. The results showed that the ability of Virgibacillus salarius to grow and reduce surface tension under a wide range of pH, salinities and temperatures gives bacteria isolate an advantage in many applications such as pharmaceutical, cosmetics, food industries and bioremediation in marine environment. The biosurfactant production by V. salarius decreased surface tension and emulsifying activity (30 mN/m and 80%, respectively). In addition to reducing the production cost of biosurfactants by tested several plant-derived oils such as jatropha oil, castor oils, jojoba oil, canola oil and cottonseed oil. In this respect the feasibility to reusing old frying oil of sunflower for production rhamnolipids and sophorolipids, their use that lead to solve many ecological and industrial problems. PMID:26150754

  17. Conservation genetics of extremely isolated urban populations of the northern dusky salamander (Desmognathus fuscus in New York City

    Directory of Open Access Journals (Sweden)

    Jason Munshi-South

    2013-04-01

    Full Text Available Urbanization is a major cause of amphibian decline. Stream-dwelling plethodontid salamanders are particularly susceptible to urbanization due to declining water quality and hydrological changes, but few studies have examined these taxa in cities. The northern dusky salamander (Desmognathus fuscus was once common in the New York City metropolitan area, but has substantially declined throughout the region in recent decades. We used five tetranucleotide microsatellite loci to examine population differentiation, genetic variation, and bottlenecks among five remnant urban populations of dusky salamanders in NYC. These genetic measures provide information on isolation, prevalence of inbreeding, long-term prospects for population persistence, and potential for evolutionary responses to future environmental change. All populations were genetically differentiated from each other, and the most isolated populations in Manhattan have maintained very little genetic variation (i.e. <20% heterozygosity. A majority of the populations also exhibited evidence of genetic bottlenecks. These findings contrast with published estimates of high genetic variation within and lack of structure between populations of other desmognathine salamanders sampled over similar or larger spatial scales. Declines in genetic variation likely resulted from population extirpations and the degradation of stream and terrestrial paths for dispersal in NYC. Loss of genetic variability in populations isolated by human development may be an underappreciated cause and/or consequence of the decline of this species in urbanized areas of the northeast USA.

  18. Extremely discrepant mutation spectrum of SLC26A4 between Chinese patients with isolated Mondini deformity and enlarged vestibular aqueduct.

    Science.gov (United States)

    Huang, Shasha; Han, Dongyi; Yuan, Yongyi; Wang, Guojian; Kang, Dongyang; Zhang, Xin; Yan, Xiaofei; Meng, Xiaoxiao; Dong, Min; Dai, Pu

    2011-09-30

    Mutations in SLC26A4 cause Pendred syndrome (hearing loss with goiter) or DFNB4 (non-syndromic hearing loss with inner ear malformation, such as enlarged vestibular aqueduct or Mondini deformity). The relationship between mutations in SLC26A4 and Mondini deformity without enlarged vestibular aqueduct has not been studied in any Chinese deaf population. The purpose of this study was to assess whether mutations in the SLC26A4 gene cause Mondini deformity without an enlarged vestibular aqueduct (isolated Mondini deformity) in a Chinese population. In total, 144 patients with sensorineural hearing loss were included and subjected to high-resolution temporal bone CT. Among them, 28 patients with isolated Mondini dysplasia (MD group), 50 patients with enlarged vestibular aqueduct with Mondini dysplasia (EVA with MD group), 50 patients with enlarged vestibular aqueduct without Mondini dysplasia (EVA group), and 16 patients with other types of inner ear malformations (IEM group) were identified. The coding exons of SLC26A4 were analyzed in all subjects. DNA sequence analysis of SLC26A4 was performed in all 144 patients. In the different groups, the detection rate of the SLC26A4 mutation differed. In the isolated MD group, only one single allelic mutation in SLC26A4 was found in one patient (1/28, 3.6%). In the EVA with MD group, biallelic and monoallelic SLC26A4 mutations were identified in 46 patients (46/50, 92.0%) and three patients (3/50, 6.0%), respectively. Also, in the EVA group, biallelic and monoallelic SLC26A4 mutations were identified in 46 patients (46/50, 92.0%) and three patients (3/50, 6.0%), respectively. These percentages were identical to those in the EVA plus MD group. Only two patients carried monoallelic mutations of the SLC26A4 gene in the IEM group (2/16, 12.5%). There were significant differences in the frequency of SLC26A4 mutation among the groups (P0.5). Although mutations in the SLC26A4 gene were frequently found in Chinese EVA patients with and

  19. [Astrophysics of binary stars, Seyfert galaxies, quasars, and globular clusters. Final technical report

    International Nuclear Information System (INIS)

    Press, W.H.

    1985-01-01

    Several problems were investigated. The time-steady accretion of gas irradiated by a self-consistently generated quasar-like continuum was studied. The observed x-ray sources near the core of the Orion molecular cloud were established to be sufficient to supply all the ionization that is needed to drive the molecular chemistry throughout that portion of the cloud in which the greatest density and diversity of molecular species is found. A new suggestion was put forth for a single pass, high gain, O 5+ ion laboratory laser at 1035 A. The only evidence for binaries in globular clusters was found to come from binaries in extreme states, cataclysmic variables, and x-ray sources. The various evolutionary paths possible for highly compact binaries in globular clusters where they come under the simultaneous influence of gravitational radiation and gravitational encounters with field stars were analyzed. The secular evolution of a highly compact binary stellar system, composed of a collapsed object and a low-mass secondary star, in the core of a globular cluster was calculated. The dynamics of the narrow line regions of Seyfert galaxies were investigated. New calculations of the soft x-ray opacity of gas having cosmic elemental abunances were developed for a variety of ionization states. Results were presented of the analysis of 28 Einstein SSS observations of 15 high x-ray luminosity quasars and Seyfert type I nuclei

  20. Testing modified gravity with globular clusters: the case of NGC 2419

    Science.gov (United States)

    Llinares, Claudio

    2018-02-01

    The dynamics of globular clusters has been studied in great detail in the context of general relativity as well as with modifications of gravity that strongly depart from the standard paradigm such as MOND. However, at present there are no studies that aim to test the impact that less extreme modifications of gravity (e.g. models constructed as alternatives to dark energy) have on the behaviour of globular clusters. This Letter presents fits to the velocity dispersion profile of the cluster NGC 2419 under the symmetron modified gravity model. The data shows an increase in the velocity dispersion towards the centre of the cluster which could be difficult to explain within general relativity. By finding the best fitting solution associated with the symmetron model, we show that this tension does not exist in modified gravity. However, the best fitting parameters give a model that is inconsistent with the dynamics of the Solar System. Exploration of different screening mechanisms should give us the chance to understand if it is possible to maintain the appealing properties of the symmetron model when it comes to globular clusters and at the same time recover the Solar System dynamics properly.

  1. Dynamics of the globular cluster NGC 362

    Science.gov (United States)

    Fischer, Philippe; Welch, Douglas L.; Mateo, Mario; Cote, Patrick

    1993-01-01

    A combination of V-band CCD images and echelle spectra of member red giants is presently used to examine the internal dynamics of the globular cluster NGC 362. A total of 285 stellar spectra were obtained of 215 stars for radial velocity determinations, and the true cluster binary fraction was determined from simulations to be 0.15 for circular orbits and 0.27 for orbits with an f(e) = e (eccentricity) distribution function. An overabundance of binaries is surmised for NGC 362 on this basis.

  2. Near infrared photometry of globular clusters

    International Nuclear Information System (INIS)

    Evans, T.L.; Menzies, J.W.

    1977-01-01

    Photographic photometry on the V, Isub(K) system has been obtained for giant stars in the metal-rich globular clusters NGC 5927, 6171, 6352, 6356, 6388, 6522, 6528, 6712 and 6723. Colour-magnitude diagrams are presented. These data, with earlier observations of NGC 104 (47 Tuc), yield new parameters to describe the giant branch. These are the colour of the red variables, represented by their mean colour (V - Isub(K)) 0 or by the colour (V - Isub(K))sub(BO) of the bluest red variable on the giant branch of a cluster, and ΔV' which is the magnitude difference between the horizontal branch and the highest point on the giant branch. The latter is independent of reddening, since the giant branch of the most metal-rich clusters passes through a maximum in the V, V - Isub(K) plane. These parameters are correlated with the metal content, deduced from integrated photometry: the red variables are redder and the giant branch fainter the higher the metal content. Comparison with theoretical evolutionary tracks suggests that the range in metal content of these clusters is at most a factor of 10, the most metal-rich clusters possibly approaching the solar value. The cluster giant branches and those of open clusters, groups and field stars of the old disk population are compared. The assumption that all the globular clusters have an absolute magnitude on the horizontal branch of Msub(v) = + 0.9, as found recently for 47 Tuc, gives good agreement between the magnitudes of giant stars in the most metal rich of the globular clusters and those of field stars deduced from statistical parallaxes and moving group parallaxes. The values of the parameters ΔV' and (V - Isub(k))sub(BO) also approach those in the moving groups. The globular clusters have a longer horizontal branch, however, and the subgiants are bluer even when the values of ) 7Fe/H{ appear to be the same. (author). )

  3. Extremely discrepant mutation spectrum of SLC26A4 between Chinese patients with isolated Mondini deformity and enlarged vestibular aqueduct

    Directory of Open Access Journals (Sweden)

    Yan Xiaofei

    2011-09-01

    Full Text Available Abstract Background Mutations in SLC26A4 cause Pendred syndrome (hearing loss with goiter or DFNB4 (non-syndromic hearing loss with inner ear malformation, such as enlarged vestibular aqueduct or Mondini deformity. The relationship between mutations in SLC26A4 and Mondini deformity without enlarged vestibular aqueduct has not been studied in any Chinese deaf population. The purpose of this study was to assess whether mutations in the SLC26A4 gene cause Mondini deformity without an enlarged vestibular aqueduct (isolated Mondini deformity in a Chinese population. Methods In total, 144 patients with sensorineural hearing loss were included and subjected to high-resolution temporal bone CT. Among them, 28 patients with isolated Mondini dysplasia (MD group, 50 patients with enlarged vestibular aqueduct with Mondini dysplasia (EVA with MD group, 50 patients with enlarged vestibular aqueduct without Mondini dysplasia (EVA group, and 16 patients with other types of inner ear malformations (IEM group were identified. The coding exons of SLC26A4 were analyzed in all subjects. Results DNA sequence analysis of SLC26A4 was performed in all 144 patients. In the different groups, the detection rate of the SLC26A4 mutation differed. In the isolated MD group, only one single allelic mutation in SLC26A4 was found in one patient (1/28, 3.6%. In the EVA with MD group, biallelic and monoallelic SLC26A4 mutations were identified in 46 patients (46/50, 92.0% and three patients (3/50, 6.0%, respectively. Also, in the EVA group, biallelic and monoallelic SLC26A4 mutations were identified in 46 patients (46/50, 92.0% and three patients (3/50, 6.0%, respectively. These percentages were identical to those in the EVA plus MD group. Only two patients carried monoallelic mutations of the SLC26A4 gene in the IEM group (2/16, 12.5%. There were significant differences in the frequency of SLC26A4 mutation among the groups (P SLC26A4 mutation in the isolated MD group was

  4. Biosynthesis and characterization of polyhydroxyalkanoates produced by an extreme halophilic bacterium, Halomonas nitroreducens, isolated from hypersaline ponds.

    Science.gov (United States)

    Cervantes-Uc, J M; Catzin, J; Vargas, I; Herrera-Kao, W; Moguel, F; Ramirez, E; Rincón-Arriaga, S; Lizama-Uc, G

    2014-10-01

    Morphological, biochemical and genotypic characterization of a halophilic bacterium isolated from hypersaline ponds located at Las Coloradas (Río Lagartos, Yucatán, Mexico). Characterization of polymer produced by this strain was also performed. Twenty strains were isolated from water samples of salt ponds and selected based on both morphological features and their PHA storage capacity, which were determined by SEM and staining methods with Nile red and Nile blue, respectively; strains were also analysed by the fluorescence imaging technique. Among them, JCCOL25.8 strain showed the highest production of PHA's reason why phenotypic and genotypic characterization was performed; this strain was identified as Halomonas nitroreducens. Polymer produced by this strain was characterized by FTIR, DSC, GPC and EDX spectroscopy. Results indicated that the biosynthesized polymer was polyhydroxybutyrate (PHB) which had a melting peak at 170°C and a crystallinity percentage of about 36%. Based on phenotypic and genotypic aspects, JCCOL25.8 strain was identified as H. nitroreducens and it was capable to accumulate PHB. To our knowledge, there is only one study published on the biosynthesis of PHA's by H. nitroreducens strains, although the characterization of the obtained polymer was not reported. © 2014 The Society for Applied Microbiology.

  5. Bacterial Survival under Extreme UV Radiation: A Comparative Proteomics Study of Rhodobacter sp., Isolated from High Altitude Wetlands in Chile

    Directory of Open Access Journals (Sweden)

    Vilma Pérez

    2017-06-01

    Full Text Available Salar de Huasco, defined as a polyextreme environment, is a high altitude saline wetland in the Chilean Altiplano (3800 m.a.s.l., permanently exposed to the highest solar radiation doses registered in the world. We present here the first comparative proteomics study of a photoheterotrophic bacterium, Rhodobacter sp., isolated from this remote and hostile habitat. We developed an innovative experimental approach using different sources of radiation (in situ sunlight and UVB lamps, cut-off filters (Mylar, Lee filters and a high-throughput, label-free quantitative proteomics method to comprehensively analyze the effect of seven spectral bands on protein regulation. A hierarchical cluster analysis of 40 common proteins revealed that all conditions containing the most damaging UVB radiation induced similar pattern of protein regulation compared with UVA and visible light spectral bands. Moreover, it appeared that the cellular adaptation of Rhodobacter sp. to osmotic stress encountered in the hypersaline environment from which it was originally isolated, might further a higher resistance to damaging UV radiation. Indeed, proteins involved in the synthesis and transport of key osmoprotectants, such as glycine betaine and inositol, were found in very high abundance under UV radiation compared to the dark control, suggesting the function of osmolytes as efficient reactive oxygen scavengers. Our study also revealed a RecA-independent response and a tightly regulated network of protein quality control involving proteases and chaperones to selectively degrade misfolded and/or damaged proteins.

  6. Edades relativas de cúmulos globulares

    Science.gov (United States)

    Miller Bertolami, M.; Forte, J. C.

    El trabajo de Rossemberg et al (1999), estudia las edades relativas de cúmulos globulares galácticos mediante el análisis de ciertos parámetros morfológicos de los diagramas color-magnitud de dichos cúmulos. Este trabajo se centra en tres puntos: analizar la consistencia de los resultados obtenidos por Rossemberg et al (1999) al emplear observaciones en el sistema fotométrico de Washington, más precisamente, las magnitudes C y T1 en lugar de las magnitudes V e I utilizadas por dichos autores. De la existencia de colores integrados, metalicidad y edad (relativa) para 21 de los cúmulos utilizados en dicho trabajo, se analiza la consistencia de estos resultados con las dependencias de color integrado como función de la edad y la metalicidad que se desprenden de los modelos teóricos de luz integrada por Worthey (1994), Schulz (2002) y Lee et al (2002). Por último se lleva a cabo una breve comparación de la morfología de los diagramas color-magnitud de los cúmulos globulares y de las isocronas utilizadas, a fin de intentar identificar algunas de las posibles causas de las diferencias observadas en los incisos anteriores.

  7. Thermoanaerobacter pentosaceus sp. nov., an anaerobic, extreme thermophilic, high ethanol-yielding bacterium isolated from household waste

    DEFF Research Database (Denmark)

    Tomás, Ana Faria; Karakashev, Dimitar Borisov; Angelidaki, Irini

    2013-01-01

    of approximately 0.5 µm. Optimal growth occurred at 70 °C and pH(25°C) 7, with a maximum growth rate of 0.1 h-1. DNA G+C content was 34.2 mol %. Strain DTU01(T) could ferment arabinose, cellobiose, fructose, galactose, glucose, inulin, lactose, mannose, melibiose, pectin, starch, sucrose, xylan, yeast extract...... and xylose, but not cellulose, Avicel®, mannitol, inositol, glycerol, acetate, lactate, ethanol, butanol or peptone. Ethanol was the major fermentation product and a maximum yield of 1.39 mol of ethanol per mol xylose was achieved when sulphite was added to the cultivation medium. Thiosulphite......, the physiological and phylogenetic differences (DNA G+C content, substrate utilization, electron acceptors, phylogenetic distance, isolation site) allow for the proposal of strain DTU01(T) as a new species within the genus Thermoanaerobacter, for which the name Thermoanaerobacter pentosaceus sp. nov. is proposed...

  8. ARE SOME MILKY WAY GLOBULAR CLUSTERS HOSTED BY UNDISCOVERED GALAXIES?

    Energy Technology Data Exchange (ETDEWEB)

    Zaritsky, Dennis [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Crnojević, Denija; Sand, David J., E-mail: dennis.zaritsky@gmail.com [Physics Department, Texas Tech University, Box 41051, Lubbock, TX 79409 (United States)

    2016-07-20

    The confirmation of a globular cluster (GC) in the recently discovered ultrafaint galaxy Eridanus II (Eri II) motivated us to examine the question posed in the title. After estimating the halo mass of Eri II using a published stellar mass—halo mass relation, the one GC in this galaxy supports extending the relationship between the number of GCs hosted by a galaxy and the galaxy’s total mass about two orders of magnitude in stellar mass below the previous limit. For this empirically determined specific frequency of between 0.06 and 0.39 GCs per 10{sup 9} M {sub ⊙} of total mass, the surviving Milky Way (MW) subhalos with masses smaller than 10{sup 10} M {sub ⊙} could host as many as 5–31 GCs, broadly consistent with the actual population of outer halo MW GCs, although matching the radial distribution in detail remains a challenge. Using a subhalo mass function from published high-resolution numerical simulations and a Poissonian model for populating those halos with the aforementioned empirically constrained frequency, we find that about 90% of these GCs lie in lower-mass subhalos than that of Eri II. From what we know about the stellar mass–halo mass function, the subhalo mass function, and the mass-normalized GC specific frequency, we conclude that some of the MW’s outer halo GCs are likely to be hosted by undetected subhalos with extremely modest stellar populations.

  9. The Velocity Field of the Globular Cluster System in NGC 5128 (Cen A)

    Science.gov (United States)

    Harris, William; Woodley, Kristin; Geisler, Doug; Gomez, Matias; Harris, Gretchen

    2007-02-01

    We propose to carry out a comprehensive new dynamical study of the globular cluster system of NGC 5128 (Centaurus A), the nearest giant E galaxy. A key component of our proposal is a completely new catalog of globular cluster candidates that we have generated from a wide-field (1.4 sq deg) R-band imaging survey of NGC 5128 taken April 2006 with Magellan/IMACS under remarkable 0.45" seeing. We have used this new imaging survey to isolate a list of GC candidates that is far more precise, complete, and contamination-free than in any previous work. As spectroscopic followup, we will use the CTIO 4m + Hydra to measure velocities for 800 new GC candidates, of which 400 or more should be bona fide clusters. Our new data will double the known NGC 5128 GC sample and will eliminate the spatial biases inherent in all previous studies of this unique system. More importantly, the large new velocity database will be the springboard for a superior dynamical analysis of the galaxy and the halo velocity field. This work will allow us to define later programs aimed at detailed abundance and age distribution profiles for the system, and systematic trends with metallicity, that will closely connect with galaxy formation models. In addition, our GC database will rank among the largest ever assembled for a single galaxy, not only enabling us to test galaxy formation models but also providing a benchmark dataset in globular cluster research.

  10. Improvement of the Uranium Sequestration Ability of a Chlamydomonas sp. (ChlSP Strain) Isolated From Extreme Uranium Mine Tailings Through Selection for Potential Bioremediation Application

    Science.gov (United States)

    Baselga-Cervera, Beatriz; Romero-López, Julia; García-Balboa, Camino; Costas, Eduardo; López-Rodas, Victoria

    2018-01-01

    The extraction and processing of uranium (U) have polluted large areas worldwide, rendering anthropogenic extreme environments inhospitable to most species. Noticeably, these sites are of great interest for taxonomical and applied bioprospection of extremotolerant species successfully adapted to U tailings contamination. As an example, in this work we have studied a microalgae species that inhabits extreme U tailings ponds at the Saelices mining site (Salamanca, Spain), characterized as acidic (pH between 3 and 4), radioactive (around 4 μSv h−1) and contaminated with metals, mainly U (from 25 to 48 mg L−1) and zinc (from 17 to 87 mg L−1). After isolation of the extremotolerant ChlSP strain, morphological characterization and internal transcribed spacer (ITS)-5.8S gene sequences placed it in the Chlamydomonadaceae, but BLAST analyses identity values, against the nucleotide datasets at the NCBI database, were very low (microalgae growth curve; ChlSG cells removed close to 4 mg L−1 of U in 24 days. These findings open up promising prospects for sustainable management of U tailings waters based on newly evolved extremotolerants and outline the potential of artificial selection in the improvement of desired features in microalgae by experimental adaptation and selection. PMID:29662476

  11. Extremely intense (SML ≤–2500 nT substorms: isolated events that are externally triggered?

    Directory of Open Access Journals (Sweden)

    B. T. Tsurutani

    2015-05-01

    Full Text Available We examine particularly intense substorms (SML ≤–2500 nT, hereafter called "supersubstorms" or SSS events, to identify their nature and their magnetic storm dependences. It is found that these intense substorms are typically isolated events and are only loosely related to magnetic storms. SSS events can occur during super (Dst ≤–250 nT and intense (−100 nT ≥ Dst >–250 magnetic storms. SSS events can also occur during nonstorm (Dst ≥–50 nT intervals. SSSs are important because the strongest ionospheric currents will flow during these events, potentially causing power outages on Earth. Several SSS examples are shown. SSS events appear to be externally triggered by small regions of very high density (~30 to 50 cm−3 solar wind plasma parcels (PPs impinging upon the magnetosphere. Precursor southward interplanetary magnetic fields are detected prior to the PPs hitting the magnetosphere. Our hypothesis is that these southward fields input energy into the magnetosphere/magnetotail and the PPs trigger the release of the stored energy.

  12. Extreme isolation of WN3/O3 stars and implications for their evolutionary origin as the elusive stripped binaries

    Science.gov (United States)

    Smith, Nathan; Götberg, Ylva; de Mink, Selma E.

    2018-03-01

    Recent surveys of the Magellanic Clouds have revealed a subtype of Wolf-Rayet (WR) star with peculiar properties. WN3/O3 spectra exhibit both WR-like emission and O3 V-like absorption - but at lower luminosity than O3 V or WN stars. We examine the projected spatial distribution of WN3/O3 stars in the Large Magellanic Cloud as compared to O-type stars. Surprisingly, WN3/O3 stars are among the most isolated of all classes of massive stars; they have a distribution similar to red supergiants dominated by initial masses of 10-15 M⊙, and are far more dispersed than classical WR stars or luminous blue variables. Their lack of association with clusters of O-type stars suggests strongly that WN3/O3 stars are not the descendants of single massive stars (30 M⊙ or above). Instead, they are likely products of interacting binaries at lower initial mass (10-18 M⊙). Comparison with binary models suggests a probable origin with primaries in this mass range that were stripped of their H envelopes through non-conservative mass transfer by a low-mass secondary. We show that model spectra and positions on the Hertzsprung-Russell diagram for binary-stripped stars are consistent with WN3/O3 stars. Monitoring radial velocities with high-resolution spectra can test for low-mass companions or runaway velocities. With lower initial mass and environments that avoid very massive stars, the WN3/O3 stars fit expectations for progenitors of Type Ib and possibly Type Ibn supernovae.

  13. Clinical outcomes of isolated lower extremity or foot burns in diabetic versus non-diabetic patients: a 10-year retrospective analysis.

    Science.gov (United States)

    Kimball, Zachary; Patil, Sachin; Mansour, Hani; Marano, Michael A; Petrone, Sylvia J; Chamberlain, Ronald S

    2013-03-01

    The incidence of diabetes mellitus (DM) in the United States is expected to increase from 8 per 1000 in 2008 to 15 per 1000 by 2050 [20]. As a result, DM patients will constitute a large proportion of Burn Center admissions, with burns typically due to contact burn or scalding. Peripheral vascular disease (PVD) and peripheral neuropathy (PN) are far more common in DM patients, particularly in those with poorly controlled disease, and are often associated with worse outcomes than non-diabetic (nDM) burn patients. This study sought to analyze whether the outcome of isolated leg and foot burns among DM and nDM individuals differed significantly. Retrospective data on 207 consecutive patients (>18 years old) admitted to a Burn Center with isolated leg or foot burns between 1999 and 2009 was collected and analyzed for this study. Age, gender, ethnicity, total body surface area (TBSA), degree of burn, etiology, hospital and burn intensive care unit (ICU), length of stay (LOS), and status at discharge were reviewed. Patients were grouped as diabetic (DM) or non-diabetic (nDM). Differences were analyzed using either the Student's t-test or Chi-square. 43 DM and 164 nDM patients with isolated lower extremity or foot burns were treated during the study period (1999-2009). The mean age of DM and nDM patients was 54.6 and 43.7 years, respectively (pburn etiology was scalding, flame, or contact burn. Percentage of total body surface area (TBSA) burn in DM patients averaged±standard deviation 1.8±1.3% compared to 1.8±1.6% in nDM (pthird degree burns and 14% (N=6) of patients had second degree burns compared to 76% (N=125) of patients and 24% (N=39) of patients among nDM patients, respectively (pburn ICU admission rates, 16.3% of patients versus 8.5% of patients (pburns to the feet or lower extremities have poorer clinical outcomes and more complicated and protracted hospital courses when compared to nDM patients with similar burns. Although diabetics in the current study did

  14. Efectos de mareas en cúmulos globulares

    Science.gov (United States)

    Ramos, F.; Coenda, V.; Muriel, H.; Abadi, M.

    Using an N-body numerical simulation in the framework of the CDM cosmological model we study the globular cluster population in a simulated galaxy cluster. We select particles that trace the bimodal (red and blue) globular cluster system of each individual dark matter halo prior to their incorporation to the cluster virial radius. We found that the blue population is more prone to be removed from the halo than the red one. This result suggests that globular clusters are tidally disrupted; being the blue (more extended) population easily removed. FULL TEXT IN SPANISH

  15. Extragalactic globular clusters. I. The metallicity calibration

    International Nuclear Information System (INIS)

    Brodie, J.P.; Huchra, J.P.

    1990-01-01

    The ability of absorption-line strength indices, measured from integrated globular cluster spectra, to predict mean cluster metallicity is explored. Statistical criteria, are used to identify the six best indices out of about 20 measured in a large sample of Galactic and M31 cluster spectra. Linear relations between index and metallicity have been derived along with new calibrations of infrared colors (V - K, J - K, and CO) versus Fe/H. Estimates of metallicity from the six spectroscopic index-metallicity relations have been combined in three different ways to identify the most efficient estimator and the minimum bias estimator of Fe/H - the weighted mean. This provides an estimate of Fe/H accurate to about 15 percent. 37 refs

  16. Detecting Globular Star Cluster Tidal Streams

    Science.gov (United States)

    Powell, William Lee, Jr.; Wilhelm, Ronald; Lauchner, Adam; McWilliam, Andrew

    2006-10-01

    Globular cluster tidal streams are of interest for what they can tell us of the dynamical evolution of the clusters and of our Galaxy. Recent studies have used photometric and statistical subtraction methods to attempt to separate potential streams from the field stars that contaminate the samples. As our primary method we choose instead to use photometry to select blue stars that match the horizontal branch of the clusters. We then make spectroscopic observations of these candidates to determine their metallicities and radial velocities, which further constrains whether the candidate stars really originated in the cluster. Combining these results with the photometric data offers a better picture of the structure of tidal streams, and allows comparison of detected stars to theoretical predictions. We present preliminary photometric and spectroscopic results. Data obtained at McDonald Observatory, Kitt Peak National Observatory, and Las Campanas Observatory.

  17. LITHIUM-RICH GIANTS IN GLOBULAR CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Kirby, Evan N.; Cohen, Judith G. [California Institute of Technology, 1200 E. California Boulevard, MC 249-17, Pasadena, CA 91125 (United States); Guhathakurta, Puragra [UCO/Lick Observatory and Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Zhang, Andrew J. [The Harker School, 500 Saratoga Avenue, San Jose, CA 95129 (United States); Hong, Jerry [Palo Alto High School, 50 Embarcadero Road, Palo Alto, CA, 94301 (United States); Guo, Michelle [Stanford University, 450 Serra Mall, Stanford, CA 94305 (United States); Guo, Rachel [Irvington High School, 41800 Blacow Road, Fremont, CA 94538 (United States); Cunha, Katia [Observatório Nacional, São Cristóvão Rio de Janeiro (Brazil)

    2016-03-10

    Although red giants deplete lithium on their surfaces, some giants are Li-rich. Intermediate-mass asymptotic giant branch (AGB) stars can generate Li through the Cameron–Fowler conveyor, but the existence of Li-rich, low-mass red giant branch (RGB) stars is puzzling. Globular clusters are the best sites to examine this phenomenon because it is straightforward to determine membership in the cluster and to identify the evolutionary state of each star. In 72 hours of Keck/DEIMOS exposures in 25 clusters, we found four Li-rich RGB and two Li-rich AGB stars. There were 1696 RGB and 125 AGB stars with measurements or upper limits consistent with normal abundances of Li. Hence, the frequency of Li-richness in globular clusters is (0.2 ± 0.1)% for the RGB, (1.6 ± 1.1)% for the AGB, and (0.3 ± 0.1)% for all giants. Because the Li-rich RGB stars are on the lower RGB, Li self-generation mechanisms proposed to occur at the luminosity function bump or He core flash cannot explain these four lower RGB stars. We propose the following origin for Li enrichment: (1) All luminous giants experience a brief phase of Li enrichment at the He core flash. (2) All post-RGB stars with binary companions on the lower RGB will engage in mass transfer. This scenario predicts that 0.1% of lower RGB stars will appear Li-rich due to mass transfer from a recently Li-enhanced companion. This frequency is at the lower end of our confidence interval.

  18. A DYING STAR IN GLOBULAR CLUSTER

    Science.gov (United States)

    2002-01-01

    A DYING STAR IN GLOBULAR CLUSTER M15 The globular cluster Messier 15 is shown in this color image obtained with the NASA Hubble Space Telescope's Wide Field Planetary Camera 2 (WFPC2). Lying some 40,000 light-years from Earth in the direction of the constellation Pegasus, M15 is one of nearly 150 known globular clusters that form a vast halo surrounding our Milky Way galaxy. Each of these clusters is a spherical association of hundreds of thousands of ancient stars. The image, prepared by the Hubble Heritage team, attempts to show the stars in M15 in their true colors. The brightest cluster stars are red giants, with an orange color due to surface temperatures lower than our Sun's. Most of the fainter stars are hotter, giving them a bluish-white color. If we lived in the core of M15, our sky would blaze with tens of thousands of brilliant stars both day and night! Nestled among the myriads of stars visible in the Hubble image is an astronomical oddity. The pinkish object to the upper left of the cluster's core is a gas cloud surrounding a dying star. Known as Kuestner 648, this was the first planetary nebula to be identified in a globular cluster. In 1928, F. G. Pease, working at the 100-inch telescope of California's Mount Wilson Observatory, photographed the spectrum of K 648 and discovered the telltale bright emission of a nebular gas cloud rather than a normal star. In the ensuing 70 years, only three more planetary nebulae have been discovered in globular clusters. The stars in M15 and other globular clusters are estimated to be about 12 billion years old. They were among the first generations of stars to form in the Milky Way. Our Sun, by comparison, is a youthful 4.6 billion years old. As a star like the Sun ages, it exhausts the hydrogen that fuels its nuclear fusion, and increases in size to become a red giant. Then it ejects its outer layers into space, producing a planetary nebula. The remnant star at the center of the nebula gradually dies away as a

  19. Most Massive Globular Cluster in Our Galaxy

    Science.gov (United States)

    1994-05-01

    Far down in the southern sky, in the constellation of Centaurus, a diffuse spot of light can be perceived with the unaided eye. It may be unimpressive, but when seen through a telescope, it turns out to be a beautiful, dense cluster of innumerable stars [1]. Omega Centauri, as this object is called, is the brightest of its type in the sky. We refer to it as a "globular cluster", due to its symmetric form. It belongs to our Milky Way galaxy and astrophysical investigations have shown that it is located at a distance of about 16,500 light-years (1 light-year = 9,460,000,000,000 km). Nobody knows for sure how many individual stars it contains, but recent estimates run into the millions. Most of these stars are more than 10,000 million years old and it is generally agreed that Omega Centauri has a similar age. Measurements of its motion indicate that Omega Centauri plows through the Milky Way in an elongated orbit. It is not easy to understand how it has managed to keep its stars together during such an extended period. MEASURING STELLAR VELOCITIES IN OMEGA CENTAURI A group of astronomers [2] have recently carried through a major investigation of Omega Centauri. After many nights of observations at the ESO La Silla observatory, they now conclude that not only is this globular cluster the brightest, it is indeed by far the most massive known in the Milky Way. The very time-consuming observations were made during numerous observing sessions over a period of no less than 13 years (1981-1993), with the photoelectric spectrometer CORAVEL mounted on the 1.5-m Danish telescope at La Silla. The CORAVEL instrument (COrelation RAdial VELocities) was built in a joint effort between the Geneva (Switzerland) and Marseilles (France) observatories. It functions according to the cross-correlation technique, by means of which the spectrum of the observed star is compared with a "standard stellar spectrum" [3]. HOW HEAVY IS OMEGA CENTAURI? In the present study, a total of 1701

  20. Analytical Solution for Stellar Density in Globular Clusters

    Indian Academy of Sciences (India)

    Abstract. In this paper, four parameters analytical solution will be established for the stellar density function in globular clusters. The solution could be used for any arbitrary order of outward decrease of the cluster's density.

  1. Milky Way Globular Clusters and the Astronomical Literature

    Science.gov (United States)

    Smith, Graeme H.

    2017-06-01

    Globular clusters of the Milky Way have been the subject of many publications in the astronomical literature. However, there is quite a large dispersion in the level of scrutiny that individual clusters have received from the astronomy research community. The goal of this paper is to address the question: what makes some clusters more popular than others? Several metrics are used to compare the numbers of papers written about each globular cluster of the galaxy prior to 2015. The extent to which the metrics correlate with various intrinsic and extrinsic cluster properties is explored. The metrics are used to highlight the ten most-studied globular clusters, as well as to delineate certain types of clusters that have been least covered by research to date. As a guide to objects that might potentially reward increased study, a list is given of the highest-mass globular clusters that have received relatively little attention to date.

  2. Evidence for Primordial Mass Segregation in Globular Clusters

    Science.gov (United States)

    Baumgardt, Holger; De Marchi, Guido; Kroupa, Pavel

    2008-09-01

    We have studied the dissolution of initially mass-segregated and unsegregated star clusters due to two-body relaxation in external tidal fields, using Aarseth's collisional N-body code NBODY4 on GRAPE6 special-purpose computers. When extrapolating results of initially non-mass-segregated models to globular clusters, we obtain a correlation between the time until destruction and the slope of the mass function, in the sense that globular clusters that are closer to dissolution are more strongly depleted in low-mass stars. This correlation fits observed mass functions of most globular clusters. The mass functions of several globular clusters are, however, more strongly depleted in low-mass stars than is suggested by these models. Such strongly depleted mass functions can be explained if globular clusters started initially mass segregated. Primordial mass segregation also explains the correlation between the slope of the stellar mass function and the cluster concentration that was recently discovered by De Marchi and coworkers. In this case, it is possible that all globular clusters started with a mass function similar to that seen in young open clusters in the present-day universe, at least for stars below m = 0.8 M⊙. This argues for a near universality of the mass function for different star formation environments and metallicities in the range -2 < [ Fe/H ] < 0. We finally describe a novel algorithm that can initialize stationary mass-segregated clusters with an arbitrary density profile and amount of mass segregation.

  3. Isolation of aquatic yeasts with the ability to neutralize acidic media, from an extremely acidic river near Japan's Kusatsu-Shirane Volcano.

    Science.gov (United States)

    Mitsuya, Daisuke; Hayashi, Takuya; Wang, Yu; Tanaka, Mami; Okai, Masahiko; Ishida, Masami; Urano, Naoto

    2017-07-01

    The Yukawa River is an extremely acidic river whose waters on the east foot of the Kusatu-Shirane Volcano (in Gunma Prefecture, Japan) contain sulfate ions. Here we isolated many acid-tolerant yeasts from the Yukawa River, and some of them neutralized an acidic R2A medium containing casamino acid. Candida fluviatilis strain CeA16 had the strongest acid tolerance and neutralizing activity against the acidic medium. To clarify these phenomena, we performed neutralization tests with strain CeA16 using casamino acid, a mixture of amino acids, and 17 single amino acid solutions adjusted to pH 3.0, respectively. Strain CeA16 neutralized not only acidic casamino acid and the mixture of amino acids but also some of the acidic single amino acid solutions. Seven amino acids were strongly decomposed by strain CeA16 and simultaneously released ammonium ions. These results suggest strain CeA16 is a potential yeast as a new tool to neutralize acidic environments. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  4. Spatial Substructure in the M87 Globular Cluster System

    Science.gov (United States)

    Feng, Yuting; Zhang, Yunhao; Guhathakurta, Puragra; Peng, Eric; Lim, Sungsoon

    2018-01-01

    Based on the observation of Next Generation Virgo Cluster Survey (NGVS) project, we obtained the u,g,r,i,z and Ks band photometric information of all the objects in the 2 degree × 2 degree area (Pilot Region) around M87, the major subcluster of Virgo. By adapting an Extreme Deconvolution method, which classifies objects into Globular Clusters (GCs), galaxies and foreground stars with their color and morphology data, we got a purer-than-ever GC distribution map with a depth to gmag=25 in Pilot Region. After masking galaxy GCs, smoothing with a 10arcmin Gaussian kernel and performing a flat field correction, we show the GC density map of M87, and got a good sersic fitting of GC radial distribution with a sersic index~2.2 in the central ellipse part (45arcmin semi major axis area of M87). We quantitatively compared our GC sample with a substructure-free mock data set, which was generated from the smoothed density map as well as the sersic fitting, by calculating the 2 point correlation function (TPCF) value in different parts of the map. After separately performing such comparison with mocks based on different galaxy masking radii which vary from 4 times g band effective radius to 10, we found signals of remarkable spatial enhancement in certain directions in the central ellipse of M87, as well as halo substructures shown as lumpiness and holes in the outer region. We present the estimated scales of these substructures from the TPCF results, and, managed to locate them with a statistical analysis of the pixelized GC map. Apart from all results listed above, we discuss the constant, extra-galactic substructure signal at a scale of ~3kpc, which does not diminish with masking sizes, as the evidence of merging and accretion history of M87.

  5. A Unified Picture of Mass Segregation in Globular Clusters

    Science.gov (United States)

    Watkins, Laura

    2017-08-01

    The sensitivity, stability and longevity of HST have opened up an exciting new parameter space: we now have velocity measurements, in the form of proper motions (PMs), for stars from the tip of the red giant branch to a few magnitudes below the main-sequence turn off for a large sample of globular clusters (GCs). For the very first time, we have the opportunity to measure both kinematic and spatial dependences on stellar mass in GCs.The formation and evolution histories of GCs are poorly understood, so too are their intermediate-mass black hole populations and binary fractions. However, the current structure and dynamical state of a GC is directly determined by its past history and its components, so by understanding the former we can gain insight into the latter. Quantifying variations in spatial structure for stars of different mass is extremely difficult with photometry alone as datasets are inhomogenous and incomplete. We require kinematic data for stars that span a range of stellar masses, combined with proper dynamical modelling. We now have the data in hand, but still lack the models needed to maximise the scientific potential of our HST datasets.Here, we propose to extend existing single-mass discrete dynamical-modelling tools to include kinematic and spatial variations with stellar mass, and verify the upgrades using mock data generated from N-body models. We will then apply the models to HST PM data and directly quantify energy equipartition and mass segregation in the GCs. The theoretical phase of the project is vital for the success of the subsequent data analysis, and will serve as a benchmark for future observational campaigns with HST, JWST and beyond.

  6. Macropolyhedral boron-containing cluster chemistry. Isolation and structure of the twenty-one-vertex globular cluster compound [(.eta..sup.5./sup.-C.sub.5./sub.Me.sub.5./sub.).sub.3./sub.Ir.sub.3./sub.B.sub.18./sub.H.sub.15./sub.(OH)].sup.1./sup..

    Czech Academy of Sciences Publication Activity Database

    Shea, S. L.; Jelínek, Tomáš; Štíbr, Bohumil; Thornton-Pett, M.; Kennedy, J. D.

    2000-01-01

    Roč. 3, č. 4 (2000), s. 169-172 ISSN 1387-7003 R&D Projects: GA AV ČR IAA4032701; GA ČR GA203/00/1042; GA AV ČR KSK2050602 Grant - others:EPSRC(GB) F/78323; EPSRC(GB) J/56929; EPSRC(GB) K/05818; EPSRC(GB) L/49505; EPSRC(GB) M/83360 Institutional research plan: CEZ:AV0Z4032918 Keywords : globular * cluster * borane Subject RIV: CA - Inorganic Chemistry Impact factor: 1.090, year: 2000

  7. sCD4-17b bifunctional protein: Extremely broad and potent neutralization of HIV-1 Env pseudotyped viruses from genetically diverse primary isolates

    Directory of Open Access Journals (Sweden)

    Dey Barna

    2010-02-01

    recombinant forms AE and AG. The neutralization breadth and potency were superior to what have been reported for the broadly neutralizing monoclonal antibodies IgG b12, 2G12, 2F5, and 4E10. The activity of sCD4-17b was found to be similar against isogenic virus particles from infectious molecular clones derived either directly from the transfected producer cell line or after a single passage through PBMCs; this contrasted with the monoclonal antibodies, which were less potent against the PMBC-passaged viruses. Conclusions The results highlight the extremely potent and broad neutralizing activity of sCD4-17b against genetically diverse HIV-1 primary isolates. The bifunctional protein has potential applications for antiviral approaches to combat HIV infection.

  8. Improvement of the Uranium Sequestration Ability of a Chlamydomonas sp. (ChlSP Strain Isolated From Extreme Uranium Mine Tailings Through Selection for Potential Bioremediation Application

    Directory of Open Access Journals (Sweden)

    Beatriz Baselga-Cervera

    2018-03-01

    Full Text Available The extraction and processing of uranium (U have polluted large areas worldwide, rendering anthropogenic extreme environments inhospitable to most species. Noticeably, these sites are of great interest for taxonomical and applied bioprospection of extremotolerant species successfully adapted to U tailings contamination. As an example, in this work we have studied a microalgae species that inhabits extreme U tailings ponds at the Saelices mining site (Salamanca, Spain, characterized as acidic (pH between 3 and 4, radioactive (around 4 μSv h−1 and contaminated with metals, mainly U (from 25 to 48 mg L−1 and zinc (from 17 to 87 mg L−1. After isolation of the extremotolerant ChlSP strain, morphological characterization and internal transcribed spacer (ITS-5.8S gene sequences placed it in the Chlamydomonadaceae, but BLAST analyses identity values, against the nucleotide datasets at the NCBI database, were very low (<92%. We subjected the ChlSP strain to an artificial selection protocol to increase the U uptake and investigated its response to selection. The ancestral strain ChlSP showed a U-uptake capacity of ≈4.30 mg U g−1 of dry biomass (DB. However, the artificially selected strain ChlSG was able to take up a total of ≈6.34 mg U g−1 DB, close to the theoretical maximum response (≈7.9 mg U g−1 DB. The selected ChlSG strain showed two possible U-uptake mechanisms: the greatest proportion by biosorption onto cell walls (ca. 90%, and only a very small quantity, ~0.46 mg g−1 DB, irreversibly bound by bioaccumulation. Additionally, the kinetics of the U-uptake process were characterized during a microalgae growth curve; ChlSG cells removed close to 4 mg L−1 of U in 24 days. These findings open up promising prospects for sustainable management of U tailings waters based on newly evolved extremotolerants and outline the potential of artificial selection in the improvement of desired features in microalgae by experimental adaptation

  9. Enrichment by supernovae in globular clusters with multiple populations.

    Science.gov (United States)

    Lee, Jae-Woo; Kang, Young-Woon; Lee, Jina; Lee, Young-Wook

    2009-11-26

    The most massive globular cluster in the Milky Way, omega Centauri, is thought to be the remaining core of a disrupted dwarf galaxy, as expected within the model of hierarchical merging. It contains several stellar populations having different heavy elemental abundances supplied by supernovae-a process known as metal enrichment. Although M 22 appears to be similar to omega Cen, other peculiar globular clusters do not. Therefore omega Cen and M 22 are viewed as exceptional, and the presence of chemical inhomogeneities in other clusters is seen as 'pollution' from the intermediate-mass asymptotic-giant-branch stars expected in normal globular clusters. Here we report Ca abundances for seven globular clusters and compare them to omega Cen. Calcium and other heavy elements can only be supplied through numerous supernovae explosions of massive stars in these stellar systems, but the gravitational potentials of the present-day clusters cannot preserve most of the ejecta from such explosions. We conclude that these globular clusters, like omega Cen, are most probably the relics of more massive primeval dwarf galaxies that merged and disrupted to form the proto-Galaxy.

  10. Bio-precipitation of uranium by two bacterial isolates recovered from extreme environments as estimated by potentiometric titration, TEM and X-ray absorption spectroscopic analyses

    Energy Technology Data Exchange (ETDEWEB)

    Merroun, Mohamed L., E-mail: merroun@ugr.es [Institute of Radiochemistry, Helmholtz Centre Dresden-Rossendorf, Dresden (Germany); Departamento de Microbiologia, Universidad de Granada, Campus Fuentenueva s/n 18071, Granada (Spain); Nedelkova, Marta [Institute of Radiochemistry, Helmholtz Centre Dresden-Rossendorf, Dresden (Germany); Ojeda, Jesus J. [Cell-Mineral Interface Research Programme, Kroto Research Institute, University of Sheffield, Broad Lane, Sheffield S3 7HQ (United Kingdom); Experimental Techniques Centre, Brunel University, Uxbridge, Middlesex UB8 3PH (United Kingdom); Reitz, Thomas [Institute of Radiochemistry, Helmholtz Centre Dresden-Rossendorf, Dresden (Germany); Fernandez, Margarita Lopez; Arias, Jose M. [Departamento de Microbiologia, Universidad de Granada, Campus Fuentenueva s/n 18071, Granada (Spain); Romero-Gonzalez, Maria [Cell-Mineral Interface Research Programme, Kroto Research Institute, University of Sheffield, Broad Lane, Sheffield S3 7HQ (United Kingdom); Selenska-Pobell, Sonja [Institute of Radiochemistry, Helmholtz Centre Dresden-Rossendorf, Dresden (Germany)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer Precipitation of uranium as U phosphates by natural bacterial isolates. Black-Right-Pointing-Pointer The uranium biomineralization involves the activity of acidic phosphatase. Black-Right-Pointing-Pointer Uranium bioremediation could be achieved via the biomineralization of U(VI) in phosphate minerals. - Abstract: This work describes the mechanisms of uranium biomineralization at acidic conditions by Bacillus sphaericus JG-7B and Sphingomonas sp. S15-S1 both recovered from extreme environments. The U-bacterial interaction experiments were performed at low pH values (2.0-4.5) where the uranium aqueous speciation is dominated by highly mobile uranyl ions. X-ray absorption spectroscopy (XAS) showed that the cells of the studied strains precipitated uranium at pH 3.0 and 4.5 as a uranium phosphate mineral phase belonging to the meta-autunite group. Transmission electron microscopic (TEM) analyses showed strain-specific localization of the uranium precipitates. In the case of B. sphaericus JG-7B, the U(VI) precipitate was bound to the cell wall. Whereas for Sphingomonas sp. S15-S1, the U(VI) precipitates were observed both on the cell surface and intracellularly. The observed U(VI) biomineralization was associated with the activity of indigenous acid phosphatase detected at these pH values in the absence of an organic phosphate substrate. The biomineralization of uranium was not observed at pH 2.0, and U(VI) formed complexes with organophosphate ligands from the cells. This study increases the number of bacterial strains that have been demonstrated to precipitate uranium phosphates at acidic conditions via the activity of acid phosphatase.

  11. THE TIMING OF NINE GLOBULAR CLUSTER PULSARS

    Energy Technology Data Exchange (ETDEWEB)

    Lynch, Ryan S. [Physics Department, McGill University, 3600 Rue University, Montreal, QC H3A 2T8 (Canada); Freire, Paulo C. C. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Ransom, Scott M. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-4325 (United States); Jacoby, Bryan A., E-mail: rlynch@physics.mcgill.ca, E-mail: pfreire@mpifr-bonn.mpg.de, E-mail: sransom@nrao.edu, E-mail: bryan.jacoby@gmail.com [Aerospace Corporation, 15049 Conference Center Drive, Chantilly, VA 20151-3824 (United States)

    2012-02-01

    We have used the Robert C. Byrd Green Bank Telescope to time nine previously known pulsars without published timing solutions in the globular clusters (GCs) M62, NGC 6544, and NGC 6624. We have full timing solutions that measure the spin, astrometric, and (where applicable) binary parameters for six of these pulsars. The remaining three pulsars (reported here for the first time) were not detected enough to establish solutions. We also report our timing solutions for five pulsars with previously published solutions, and find good agreement with other authors, except for PSR J1701-3006B in M62. Gas in this system is probably responsible for the discrepancy in orbital parameters, and we have been able to measure a change in the orbital period over the course of our observations. Among the pulsars with new solutions we find several binary pulsars with very low mass companions (members of the so-called 'black widow' class) and we are able to place constraints on the mass-to-light ratio in two clusters. We confirm that one of the pulsars in NGC 6624 is indeed a member of the rare class of non-recycled pulsars found in GCs. We have also measured the orbital precession and Shapiro delay for a relativistic binary in NGC 6544. If we assume that the orbital precession can be described entirely by general relativity, which is likely, we are able to measure the total system mass (2.57190(73) M{sub Sun }) and companion mass (1.2064(20) M{sub Sun }), from which we derive the orbital inclination (sin i = 0.9956(14)) and the pulsar mass (1.3655(21) M{sub Sun }), the most precise such measurement ever obtained for a millisecond pulsar. The companion is the most massive known around a fully recycled pulsar.

  12. NEAR-IR PHOTOMETRIC PROPERTIES OF HB, MSTO, AND SGB FOR METAL POOR GALACTIC GLOBULAR CLUSTERS

    Directory of Open Access Journals (Sweden)

    J.-W. Kim

    2007-03-01

    Full Text Available We report photometric features of the HB, MSTO, and SGB for a set of metal-poor Galactic globular clusters on the near-IR CMDs. The magnitude and color of the MSTO and SGB are measured on the fiducial normal points of the CMDs by applying a polynomial fit. The near-IR luminosity functions of horizontal branch stars in the classical second parameter pair M3 and M13 indicate that HB stars in M13 are dominated by hot stars that are rotatively faint in the infrared, whereas HB stars in M3 are brighter than those in M13. The luminosity functions of HB stars in the observed bulge clusters, except for NGC 6717, show a trend that the fainter hot HB stars are dominated in the relatively metal-poor clusters while the relatively metal-rich clusters contain the brighter HB stars. It is suggestive that NGC 6717 would be an extreme example of the second-parameter phenomenon for the bulge globular clusters.

  13. Looking for tidal streams around Galactic globular clusters

    Directory of Open Access Journals (Sweden)

    Martínez-Delgado D.

    2012-02-01

    Full Text Available The picture of building the Milky Way halo from merging protogalactic fragments is considered the local manifestation of the hierarchical galaxy formation process. In this scenario, some observational evidences have suggested that the outer young Galactic halo globular cluster population might be associated (or even the nuclei to tidal disrupted dwarf spheroidals, now extinct galaxies. If this hypothesis is true, these systems might be surrounded by a distinct and still detectable stellar population. We have carried out a systematic observation of Galactic globulars covering the galactocentric distance range 10 < RGC< 40 kpc in both hemispheres. We have used wide field instruments both in La Palma and in La Silla observatories to obtain deep photometry of wide areas around these globulars to unveil the possible remnants of their progenitor dwarf galaxies.

  14. Analytical Solution for Stellar Density in Globular Clusters MA Sharaf ...

    Indian Academy of Sciences (India)

    Caloi 2008). In contrast with galaxies, it was known since the last twenty years that globular clusters represent unique laboratories for learning about two-body relax- ation, mass segregation from equipartition of energy (Spitzer 1987), stellar collisions. (Binney & Tremaine 1987), stellar mergers, and core collapse. 371 ...

  15. A 500 PARSEC HALO SURROUNDING THE GALACTIC GLOBULAR NGC 1851

    NARCIS (Netherlands)

    Olszewski, Edward W.; Saha, Abhijit; Knezek, Patricia; Subramaniam, Annapurni; de Boer, Thomas; Seitzer, Patrick

    2009-01-01

    Using imaging that shows 4 mag of main-sequence stars, we have discovered that the Galactic globular cluster NGC 1851 is surrounded by a halo that is visible from the tidal radius of 700 arcsec (41 pc) to more than 4500 arcsec (> 250 pc). This halo is symmetric and falls in density as a power law of

  16. Dynamics of globular cluster systems in elliptical galaxies

    NARCIS (Netherlands)

    Romanowsky, AJ; Geisler, D; Grebel, EK; Minniti, D

    2002-01-01

    One of the most promising avenues for exploring the dynamics of the outer parts of elliptical galaxies involves using bright discrete objects as kinematical tracers: globular clusters and planetary nebulae. As large data sets are becoming available, rigorous dynamical analyses are needed to

  17. Dynamics of Stars and Globular Clusters in Galaxy Halos

    NARCIS (Netherlands)

    Romanowsky, Aaron J.; Douglas, Nigel G.; Kuijken, Konrad; Arnaboldi, Magda; Kissler-Patig, Markus; Sharples, Ray M.; Zepf, Stephen E.; Rhode, Katherine L.; Kissler-Patig, M.

    2003-01-01

    We have obtained kinematical data in the halos of the giant ellipticals M49 and M87. These include globular cluster velocities in M49 to 10 R_eff and planetary nebula velocities in M49 and M87 to 4 R_eff. We report initial results, including dynamical comparisons between the diffuse stellar

  18. BVRI CCD photometry of the globular cluster NGC 2808

    International Nuclear Information System (INIS)

    Alcaino, G.; Liller, W.; Alvarado, F.; Wenderoth, E.

    1990-01-01

    As a part of a continuing program, CCD color-magnitude diagrams are presented for the bright globular cluster NGC 2808 in the four colors comprising BVRI. From a comparison of four different CMDs with theoretical isochrones, an age of 16 + or - 2 Gyr is obtained, assuming a value for Fe/H near -1.3. 28 refs

  19. Supra-galactic colour patterns in globular cluster systems

    Science.gov (United States)

    Forte, Juan C.

    2017-07-01

    An analysis of globular cluster systems associated with galaxies included in the Virgo and Fornax Hubble Space Telescope-Advanced Camera Surveys reveals distinct (g - z) colour modulation patterns. These features appear on composite samples of globular clusters and, most evidently, in galaxies with absolute magnitudes Mg in the range from -20.2 to -19.2. These colour modulations are also detectable on some samples of globular clusters in the central galaxies NGC 1399 and NGC 4486 (and confirmed on data sets obtained with different instruments and photometric systems), as well as in other bright galaxies in these clusters. After discarding field contamination, photometric errors and statistical effects, we conclude that these supra-galactic colour patterns are real and reflect some previously unknown characteristic. These features suggest that the globular cluster formation process was not entirely stochastic but included a fraction of clusters that formed in a rather synchronized fashion over large spatial scales, and in a tentative time lapse of about 1.5 Gy at redshifts z between 2 and 4. We speculate that the putative mechanism leading to that synchronism may be associated with large scale feedback effects connected with violent star-forming events and/or with supermassive black holes.

  20. Effects of Dynamical Evolution on Globular Clusters’ Internal Kinematics

    Science.gov (United States)

    Tiongco, Maria; Vesperini, Enrico; Varri, Anna Lisa

    2018-01-01

    The synergy between recent photometric, spectroscopic, and astrometric studies is revealing that globular clusters deviate from the traditional picture of dynamically simple and single stellar population systems. Complex kinematical features such as velocity anisotropy and rotation, and the existence of multiple stellar populations are some of the key observational findings. My thesis work has aimed to build a theoretical framework to interpret these new observational results and to understand their link with a globular cluster’s dynamical history.I have focused on the study of the evolution of globular clusters' internal kinematics, as driven by two-body relaxation, and the interplay between internal angular momentum and the external Galactic tidal field. With a specifically-designed, large survey of direct N-body simulations, I have explored the three-dimensional structure of the velocity space of tidally-perturbed clusters, by characterizing their degree of anisotropy and their rotational properties. These studies have proved that a cluster's kinematical properties contain a distinct imprints of the cluster’s initial structural properties, dynamical history, and tidal environment. By relaxing a number of simplifying assumptions that are traditionally imposed, I have also showed how the interplay between a cluster's internal evolution and the interaction with the host galaxy can produce complex morphological and kinematical properties, such as a counter-rotating core and a twisting of the projected isodensity contours.Building on this fundamental understanding, I have then studied the dynamics of multiple stellar populations in globular clusters, with attention to the largely unexplored role of angular momentum. I have analyzed the evolution of clusters with stellar populations characterized by different initial structural and kinematical properties to determine how long these differences are preserved, and in what cases they could still be observable in

  1. Globular adiponectin controls insulin-mediated vasoreactivity in muscle through AMPKα2

    DEFF Research Database (Denmark)

    de Boer, Michiel P; Meijer, Rick I; Richter, Erik

    2016-01-01

    Decreased tissue perfusion increases the risk of developing insulin resistance and cardiovascular disease in obesity, and decreased levels of globular adiponectin (gAdn) have been proposed to contribute to this risk. We hypothesized that gAdn controls insulin's vasoactive effects through AMP......-activated protein kinase (AMPK), specifically its α2 subunit, and studied the mechanisms involved. In healthy volunteers, we found that decreased plasma gAdn levels in obese subjects associate with insulin resistance and reduced capillary perfusion during hyperinsulinemia. In cultured human microvascular...... endothelial cells (HMEC), gAdn increased AMPK activity. In isolated muscle resistance arteries gAdn uncovered insulin-induced vasodilation by selectively inhibiting insulin-induced activation of ERK1/2, and the AMPK inhibitor compound C as well as genetic deletion of AMPKα2 blunted insulin...

  2. The Gaia-ESO Survey. Mg-Al anti-correlation in iDR4 globular clusters

    Science.gov (United States)

    Pancino, E.; Romano, D.; Tang, B.; Tautvaišienė, G.; Casey, A. R.; Gruyters, P.; Geisler, D.; San Roman, I.; Randich, S.; Alfaro, E. J.; Bragaglia, A.; Flaccomio, E.; Korn, A. J.; Recio-Blanco, A.; Smiljanic, R.; Carraro, G.; Bayo, A.; Costado, M. T.; Damiani, F.; Jofré, P.; Lardo, C.; de Laverny, P.; Monaco, L.; Morbidelli, L.; Sbordone, L.; Sousa, S. G.; Villanova, S.

    2017-05-01

    We use Gaia-ESO (GES) Survey iDR4 data to explore the Mg-Al anti-correlation in globular clusters that were observed as calibrators, as a demonstration of the quality of Gaia-ESO Survey data and analysis. The results compare well with the available literature, within 0.1 dex or less, after a small (compared to the internal spreads) offset between the UVES and GIRAFFE data of 0.10-0.15 dex was taken into account. In particular, for the first time we present data for NGC 5927, which is one of the most metal-rich globular clusters studied in the literature so far with [ Fe / H ] = - 0.39 ± 0.04 dex; this cluster was included to connect with the open cluster regime in the Gaia-ESO Survey internal calibration. The extent and shape of the Mg-Al anti-correlation provide strong constraints on the multiple population phenomenon in globular clusters. In particular, we studied the dependency of the Mg-Al anti-correlation extension with metallicity, present-day mass,and age of the clusters, using GES data in combination with a large set of homogenized literature measurements.We find a dependency with both metallicity and mass, which is evident when fitting for the two parameters simultaneously, but we do not find significant dependency with age. We confirm that the Mg-Al anti-correlation is not seen in all clusters, but disappears for the less massive or most metal-rich clusters. We also use our data set to see whether a normal anti-correlation would explain the low [Mg/α] observed in some extragalactic globular clusters, but find that none of the clusters in our sample can reproduce it; a more extreme chemical composition, such as that of NGC 2419, would be required. We conclude that GES iDR4 data already meet the requirements set by the main survey goals and can be used to study globular clusters in detail, even if the analysis procedures were not specifically designed for them. Based on data products from observations made with ESO Telescopes at the La Silla Paranal

  3. Challenges and advances in systems biology analysis of Bacillus spore physiology; molecular differences between an extreme heat resistant spore forming Bacillus subtilis food isolate and a laboratory strain

    NARCIS (Netherlands)

    Brul, Stanley; van Beilen, Johan; Caspers, Martien P M; O'Brien, Andrea; de Koster, Chris; Oomes, Suus; Smelt, Jan; Kort, Remco; Ter Beek, Alex

    Bacterial spore formers are prime organisms of concern in the food industry. Spores from the genus Bacillus are extremely stress resistant, most notably exemplified by high thermotolerance. This sometimes allows surviving spores to germinate and grow out to vegetative cells causing food spoilage and

  4. Challenges and advances in systems biology analysis of Bacillus spore physiology; molecular differences between an extreme heat resistant spore forming Bacillus subtilis food isolate and a laboratory strain

    NARCIS (Netherlands)

    Brul, S.; van Beilen, J.; Caspers, M.; O'Brien, A.; de Koster, C.; Oomes, S.; Smelt, J.; Kort, R.; ter Beek, A.

    2011-01-01

    Bacterial spore formers are prime organisms of concern in the food industry. Spores from the genus Bacillus are extremely stress resistant, most notably exemplified by high thermotolerance. This sometimes allows surviving spores to germinate and grow out to vegetative cells causing food spoilage and

  5. On tidal radius determination for a globular cluster

    International Nuclear Information System (INIS)

    Ninkovic, S.

    1985-01-01

    A tidal radius determination for a globular cluster based on its density minimum, which is caused by the galactic tidal forces and derivable from a model of the Galaxy, is proposed. Results obtained on the basis of the Schmidt model for two clusters are in a satisfactory agreement with those obtained earlier by means of other methods. A mass determination for the clusters through the tidal radius, when the latter one is identified with the cluster perigalactic distance, yields unusually large mass values. Probably, the tidal radius should be identified with the instantaneous galactocentric distance. Use of models more recent than the Schmidt one indicates that a globular cluster may contain a significant portion of an invisible interstellar matter. (author)

  6. BVI photometry of globular clusters in M87

    International Nuclear Information System (INIS)

    Couture, J.; Harris, W.E.; Allwright, J.W.B.

    1990-01-01

    CCD photometry in B, V, and I is presented for a sample of globular clusters in the Virgo central giant elliptical galaxy M87. No detectable gradient of mean cluster color (metallicity) in (B - V) or (V - I) with radial distance is found. The cluster system does, however, display a large dispersion in color at any radius, corresponding to sigma (Fe/H) about 0.6 about a mean metallicity of about -1.1 according to the present color index scale. The difference in mean color between the globular clusters and the underlying halo light of the galaxy itself shows up strongly in all the color indices; virtually no clusters as red as the mean color of the halo stars is found at any radius. 43 refs

  7. Globular Cluster Candidates for Hosting a Central Black Hole

    Science.gov (United States)

    Noyola, Eva

    2009-07-01

    We are continuing our study of the dynamical properties of globular clusters and we propose to obtain surface brightness profiles for high concentration clusters. Our results to date show that the distribution of central surface brightness slopes do not conform to standard models. This has important implications for how they form and evolve, and suggest the possible presence of central intermediate-mass black holes. From our previous archival proposals {AR-9542 and AR-10315}, we find that many high concentration globular clusters do not have flat cores or steep central cusps, instead they show weak cusps. Numerical simulations suggest that clusters with weak cusps may harbor intermediate-mass black holes and we have one confirmation of this connection with omega Centauri. This cluster shows a shallow cusp in its surface brightness profile, while kinematical measurements suggest the presence of a black hole in its center. Our goal is to extend these studies to a sample containing 85% of the Galactic globular clusters with concentrations higher than 1.7 and look for objects departing from isothermal behavior. The ACS globular cluster survey {GO-10775} provides enough objects to have an excellent coverage of a wide range of galactic clusters, but it contains only a couple of the ones with high concentration. The proposed sample consists of clusters whose light profile can only be adequately measured from space-based imaging. This would take us close to completeness for the high concentration cases and therefore provide a more complete list of candidates for containing a central black hole. The dataset will also be combined with our existing kinematic measurements and enhanced with future kinematic studies to perform detailed dynamical modeling.

  8. Effects of cosmic string velocities and the origin of globular clusters

    Science.gov (United States)

    Lin, Ling; Yamanouchi, Shoma; Brandenberger, Robert

    2015-12-01

    With the hypothesis that cosmic string loops act as seeds for globular clusters in mind, we study the role that velocities of these strings will play in determining the mass distribution of globular clusters. Loops with high enough velocities will not form compact and roughly spherical objects and can hence not be the seeds for globular clusters. We compute the expected number density and mass function of globular clusters as a function of both the string tension and the peak loop velocity, and compare the results with the observational data on the mass distribution of globular clusters in our Milky Way. We determine the critical peak string loop velocity above which the agreement between the string loop model for the origin of globular clusters (neglecting loop velocities) and observational data is lost.

  9. THE HELIUM CONTENT OF GLOBULAR CLUSTERS: NGC 6121 (M4)

    International Nuclear Information System (INIS)

    Villanova, S.; Geisler, D.; Piotto, G.; Gratton, R. G.

    2012-01-01

    In the context of the multiple stellar population scenario in globular clusters, helium (He) has been proposed as a key element to interpret the observed multiple main sequences, subgiant branches, and red giant branches, as well as the complex horizontal branch (HB) morphology. In particular, second-generation stars belonging to the bluer part of the HB are thought to be more He-rich (ΔY = 0.03 or more) but also more Na-rich/O-poor than those located in the redder part that should have Y equal to the cosmological value. Up to now this hypothesis was only partially confirmed in NGC 6752, where stars of the redder zero-age HB showed an He content of Y = 0.25 ± 0.01, fully compatible with the primordial He content of the universe, and were all Na-poor/O-rich. Here we study hot blue horizontal branch (BHB) stars in the GC NGC 6121 (M4) to measure their He plus O/Na content. Our goal is to complete the partial results obtained for NGC 6752, focusing our attention on targets located on the bluer part of the HB of M4. We observed six BHB stars using the VLT2/UVES spectroscopic facility. Spectra of signal-to-noise ratio ∼ 150 were obtained and the very weak He line at 5875 Å measured for all our targets. We compared this feature with synthetic spectra to obtain He abundances. In addition O, Na, and Fe abundances were estimated. Stars turned out to be all Na-rich and O-poor and to have a homogeneous He content with a mean value of Y = 0.29 ± 0.01(random) ± 0.01(systematic), which is enhanced by ΔY ∼ 0.04 with respect to the most recent measurements of the primordial He content of the universe (Y ∼ 0.24/0.25). The high He content of blue HB stars in M4 is also confirmed by the fact that they are brighter than red HB stars (RHB). Theoretical models suggest the BHB stars are He-enhanced by Δ(Y) = 0.02/0.03 with respect to the RHB stars. The whole sample of stars has a metallicity of [Fe/H] = –1.06 ± 0.02 (internal error), in agreement with other studies

  10. The Helium Content of Globular Clusters: NGC 6121 (M4)

    Science.gov (United States)

    Villanova, S.; Geisler, D.; Piotto, G.; Gratton, R. G.

    2012-03-01

    In the context of the multiple stellar population scenario in globular clusters, helium (He) has been proposed as a key element to interpret the observed multiple main sequences, subgiant branches, and red giant branches, as well as the complex horizontal branch (HB) morphology. In particular, second-generation stars belonging to the bluer part of the HB are thought to be more He-rich (ΔY = 0.03 or more) but also more Na-rich/O-poor than those located in the redder part that should have Y equal to the cosmological value. Up to now this hypothesis was only partially confirmed in NGC 6752, where stars of the redder zero-age HB showed an He content of Y = 0.25 ± 0.01, fully compatible with the primordial He content of the universe, and were all Na-poor/O-rich. Here we study hot blue horizontal branch (BHB) stars in the GC NGC 6121 (M4) to measure their He plus O/Na content. Our goal is to complete the partial results obtained for NGC 6752, focusing our attention on targets located on the bluer part of the HB of M4. We observed six BHB stars using the VLT2/UVES spectroscopic facility. Spectra of signal-to-noise ratio ~ 150 were obtained and the very weak He line at 5875 Å measured for all our targets. We compared this feature with synthetic spectra to obtain He abundances. In addition O, Na, and Fe abundances were estimated. Stars turned out to be all Na-rich and O-poor and to have a homogeneous He content with a mean value of Y = 0.29 ± 0.01(random) ± 0.01(systematic), which is enhanced by ΔY ~ 0.04 with respect to the most recent measurements of the primordial He content of the universe (Y ~ 0.24/0.25). The high He content of blue HB stars in M4 is also confirmed by the fact that they are brighter than red HB stars (RHB). Theoretical models suggest the BHB stars are He-enhanced by Δ(Y) = 0.02/0.03 with respect to the RHB stars. The whole sample of stars has a metallicity of [Fe/H] = -1.06 ± 0.02 (internal error), in agreement with other studies available in

  11. Globular adiponectin ameliorates metabolic insulin resistance via AMPK-mediated restoration of microvascular insulin responses

    Science.gov (United States)

    Zhao, Lina; Fu, Zhuo; Wu, Jing; Aylor, Kevin W; Barrett, Eugene J; Cao, Wenhong; Liu, Zhenqi

    2015-01-01

    Abstract Hypoadiponectinaemia is closely associated with endothelial dysfunction and insulin resistance, and microvasculature plays a critical role in the regulation of insulin action in muscle. Here we tested whether adiponectin replenishment could improve metabolic insulin sensitivity in male rats fed a high-fat diet (HFD) via the modulation of microvascular insulin responses. Male Sprague–Dawley rats were fed either a HFD or low-fat diet (LFD) for 4 weeks. Small resistance artery myograph changes in tension, muscle microvascular recruitment and metabolic response to insulin were determined. Compared with rats fed a LFD, HFD feeding abolished the vasodilatory actions of globular adiponectin (gAd) and insulin on pre-constricted distal saphenous arteries. Pretreatment with gAd improved insulin responses in arterioles isolated from HFD rats, which was blocked by AMP-activated protein kinase (AMPK) inhibition. Similarly, HFD abolished microvascular responses to either gAd or insulin and decreased insulin-stimulated glucose disposal by ∼60%. However, supplementing gAd fully rescued insulin’s microvascular action and significantly improved the metabolic responses to insulin in HFD male rats and these actions were abolished by inhibition of either AMPK or nitric oxide production. We conclude that HFD induces vascular adiponectin and insulin resistance but gAd administration can restore vascular insulin responses and improve insulin’s metabolic action via an AMPK- and nitric oxide-dependent mechanism in male rats. Key points Adiponectin is an adipokine with anti-inflammatory and anti-diabetic properties. Hypoadiponectinaemia is closely associated with endothelial dysfunction and insulin resistance in obesity and diabetes. Insulin resistance is present in muscle microvasculature and this may contribute to decreased insulin delivery to, and action in, muscle. In this study we examined whether adiponectin ameliorates metabolic insulin resistance by affecting muscle

  12. Globular adiponectin ameliorates metabolic insulin resistance via AMPK-mediated restoration of microvascular insulin responses.

    Science.gov (United States)

    Zhao, Lina; Fu, Zhuo; Wu, Jing; Aylor, Kevin W; Barrett, Eugene J; Cao, Wenhong; Liu, Zhenqi

    2015-09-01

    Adiponectin is an adipokine with anti-inflammatory and anti-diabetic properties. Hypoadiponectinaemia is closely associated with endothelial dysfunction and insulin resistance in obesity and diabetes. Insulin resistance is present in muscle microvasculature and this may contribute to decreased insulin delivery to, and action in, muscle. In this study we examined whether adiponectin ameliorates metabolic insulin resistance by affecting muscle microvascular recruitment. We demonstrated that a high-fat diet induces vascular adiponectin and insulin resistance but globular adiponectin administration can restore vascular insulin responses and improve insulin's metabolic action via an AMPK- and nitric oxide-dependent mechanism. This suggests that globular adiponectin might have a therapeutic potential for improving insulin resistance and preventing cardiovascular complications in patients with diabetes via modulation of microvascular insulin responses. Hypoadiponectinaemia is closely associated with endothelial dysfunction and insulin resistance, and microvasculature plays a critical role in the regulation of insulin action in muscle. Here we tested whether adiponectin replenishment could improve metabolic insulin sensitivity in male rats fed a high-fat diet (HFD) via the modulation of microvascular insulin responses. Male Sprague-Dawley rats were fed either a HFD or low-fat diet (LFD) for 4 weeks. Small resistance artery myograph changes in tension, muscle microvascular recruitment and metabolic response to insulin were determined. Compared with rats fed a LFD, HFD feeding abolished the vasodilatory actions of globular adiponectin (gAd) and insulin on pre-constricted distal saphenous arteries. Pretreatment with gAd improved insulin responses in arterioles isolated from HFD rats, which was blocked by AMP-activated protein kinase (AMPK) inhibition. Similarly, HFD abolished microvascular responses to either gAd or insulin and decreased insulin-stimulated glucose disposal by

  13. The Blue Hook Populations of Massive Globular Clusters

    Science.gov (United States)

    Brown, Thomas

    2006-07-01

    Blue hook stars are a class of hot { 35,000 K} subluminous horizontal branch stars that have been recently discovered using HST ultraviolet images of the globular clusters omega Cen and NGC 2808. These stars occupy a region of the HR diagram that is unexplained by canonical stellar evolution theory. Using new theoretical evolutionary and atmospheric models, we have shown that the blue hook stars are very likely the progeny of stars that undergo extensive internal mixing during a late helium core flash on the white dwarf cooling curve. This "flash mixing" produces an enormous enhancement of the surface helium and carbon abundances, which suppresses the flux in the far ultraviolet. Although flash mixing is more likely to occur in stars that are born with high helium abundances, a high helium abundance, by itself, does not explain the presence of a blue hook population - flash mixing of the envelope is required. We propose ACS ultraviolet {SBC/F150LP and HRC/F250W} observations of the five additional globular clusters for which the presence of blue hook stars is suspected from longer wavelength observations. Like omega Cen and NGC 2808, these five targets are also among the most massive globular clusters, because less massive clusters show no evidence for blue hook stars. Because our targets span 1.5 dex in metallicity, we will be able to test our prediction that flash-mixing should be less drastic in metal-rich blue hook stars. In addition, our observations will test the hypothesis that blue hook stars only form in globular clusters massive enough to retain the helium-enriched ejecta from the first stellar generation. If this hypothesis is correct, then our observations will yield important constraints on the chemical evolution and early formation history in globular clusters, as well as the role of helium self-enrichment in producing blue horizontal branch morphologies and multiple main sequence turnoffs. Finally, our observations will provide new insight into the

  14. Extreme cosmos

    CERN Document Server

    Gaensler, Bryan

    2011-01-01

    The universe is all about extremes. Space has a temperature 270°C below freezing. Stars die in catastrophic supernova explosions a billion times brighter than the Sun. A black hole can generate 10 million trillion volts of electricity. And hypergiants are stars 2 billion kilometres across, larger than the orbit of Jupiter. Extreme Cosmos provides a stunning new view of the way the Universe works, seen through the lens of extremes: the fastest, hottest, heaviest, brightest, oldest, densest and even the loudest. This is an astronomy book that not only offers amazing facts and figures but also re

  15. An AO-assisted Variability Study of Four Globular Clusters

    Science.gov (United States)

    Salinas, R.; Contreras Ramos, R.; Strader, J.; Hakala, P.; Catelan, M.; Peacock, M. B.; Simunovic, M.

    2016-09-01

    The image-subtraction technique applied to study variable stars in globular clusters represented a leap in the number of new detections, with the drawback that many of these new light curves could not be transformed to magnitudes due to severe crowding. In this paper, we present observations of four Galactic globular clusters, M 2 (NGC 7089), M 10 (NGC 6254), M 80 (NGC 6093), and NGC 1261, taken with the ground-layer adaptive optics module at the SOAR Telescope, SAM. We show that the higher image quality provided by SAM allows for the calibration of the light curves of the great majority of the variables near the cores of these clusters as well as the detection of new variables, even in clusters where image-subtraction searches were already conducted. We report the discovery of 15 new variables in M 2 (12 RR Lyrae stars and 3 SX Phe stars), 12 new variables in M 10 (11 SX Phe and 1 long-period variable), and 1 new W UMa-type variable in NGC 1261. No new detections are found in M 80, but previous uncertain detections are confirmed and the corresponding light curves are calibrated into magnitudes. Additionally, based on the number of detected variables and new Hubble Space Telescope/UVIS photometry, we revisit a previous suggestion that M 80 may be the globular cluster with the richest population of blue stragglers in our Galaxy. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  16. Fatigue behaviour of cast iron with globular graphite

    Energy Technology Data Exchange (ETDEWEB)

    Huebner, P.; Pusch, G.; Krodel, L. [Institut fuer Werkstofftechnik, TU Bergakademie Freiberg, Gustav-Zeuner-Strasse 5, 09599 Freiberg (Germany)

    2004-07-01

    Cast iron with bainitic matrix and globular graphite, so called austempered ductile iron (ADI), allows the substitution of heat-treatable steels. The use of ADI in safety-relevant components requires knowledge of the fracture and fatigue behaviour. Cyclic stress strain behaviour and fatigue life at total strain control and random loading have been investigated at ADI (EN-GJS-1000-5) and pearlitic cast iron (EN-GJS-600-3). In addition fracture mechanic tests at cyclic loading at various stress ratios were carried out. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  17. The gravitational waveforms of white dwarf collisions in globular clusters

    International Nuclear Information System (INIS)

    Loren-Aguilar, P; Garcia-Berro, E; Lobo, J A; Isern, J

    2009-01-01

    In the dense central regions of globular clusters close encounters of two white dwarfs are relatively frequent. The estimated frequency is one or more strong encounters per star in the lifetime of the cluster. Such encounters should be then potential sources of gravitational wave radiation. Thus, it is foreseeable that these collisions could be either individually detected by LISA or they could contribute significantly to the background noise of the detector. We compute the pattern of gravitational wave emission from these encounters for a sufficiently broad range of system parameters, namely the masses, the relative velocities and the distances of the two white dwarfs involved in the encounter.

  18. The WAGGS project - I. The WiFeS Atlas of Galactic Globular cluster Spectra

    Science.gov (United States)

    Usher, Christopher; Pastorello, Nicola; Bellstedt, Sabine; Alabi, Adebusola; Cerulo, Pierluigi; Chevalier, Leonie; Fraser-McKelvie, Amelia; Penny, Samantha; Foster, Caroline; McDermid, Richard M.; Schiavon, Ricardo P.; Villaume, Alexa

    2017-07-01

    We present the WiFeS Atlas of Galactic Globular cluster Spectra, a library of integrated spectra of Milky Way and Local Group globular clusters. We used the WiFeS integral field spectrograph on the Australian National University 2.3 m telescope to observe the central regions of 64 Milky Way globular clusters and 22 globular clusters hosted by the Milky Way's low-mass satellite galaxies. The spectra have wider wavelength coverage (3300-9050 Å) and higher spectral resolution (R = 6800) than existing spectral libraries of Milky Way globular clusters. By including Large and Small Magellanic Cloud star clusters, we extend the coverage of parameter space of existing libraries towards young and intermediate ages. While testing stellar population synthesis models and analysis techniques is the main aim of this library, the observations may also further our understanding of the stellar populations of Local Group globular clusters and make possible the direct comparison of extragalactic globular cluster integrated light observations with well-understood globular clusters in the Milky Way. The integrated spectra are publicly available via the project website.

  19. Draft genome sequence of the extremely halophilic Halorubrum sp. SAH-A6 isolated from rock salts of the Danakil depression, Ethiopia

    Directory of Open Access Journals (Sweden)

    Ashagrie Gibtan

    2016-12-01

    Full Text Available The draft genome sequence of Halorubrum sp. SAH-A6, isolated from commercial rock salts of the Danakil depression, Ethiopia. The genome comprised 3,325,770 bp, with the G + C content of 68.0%. The strain has many genes which are responsible for secondary metabolites biosynthesis, transport and catabolism as compared to other Halorubrum archaea members. Abundant genes responsible for numerous transport systems, solute accumulation, and aromatic/sulfur decomposition were detected. The first genomic analysis encourages further research on comparative genomics, and biotechnological applications. The NCBI accession number for this genome is SAMN04278861 and ID: 4278861 and strain deposited with accession number KCTC 43215.

  20. New VVV Survey Globular Cluster Candidates in the Milky Way Bulge

    Energy Technology Data Exchange (ETDEWEB)

    Minniti, Dante; Gómez, Matías [Departamento de Física, Facultad de Ciencias Exactas, Universidad Andrés Bello, Av. Fernandez Concha 700, Las Condes, Santiago (Chile); Geisler, Douglas; Fernández-Trincado, Jose G. [Departamento de Astronomía, Casilla 160-C, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Alonso-García, Javier; Beamín, Juan Carlos; Borissova, Jura; Catelan, Marcio; Ramos, Rodrigo Contreras; Kurtev, Radostin; Pullen, Joyce [Instituto Milenio de Astrofísica, Santiago (Chile); Palma, Tali; Clariá, Juan J. [Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854, Córdoba (Argentina); Cohen, Roger E. [Space Telescope Science Institute, 2700 San Martin Drive, Baltimore (United States); Dias, Bruno [European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile); Hempel, Maren [Pontificia Universidad Católica de Chile, Instituto de Astrofísica, Av. Vicuña Mackenna 4860, Santiago (Chile); Ivanov, Valentin D. [European Southern Observatory, Karl-Schwarszchild-Str. 2, D-85748 Garching bei Muenchen (Germany); Lucas, Phillip W. [Dept. of Astronomy, University of Hertfordshire, Hertfordshire (United Kingdom); Moni-Bidin, Christian; Alegría, Sebastian Ramírez [Instituto de Astronomía, Universidad Católica del Norte, Antofagasta (Chile); and others

    2017-11-10

    It is likely that a number of Galactic globular clusters remain to be discovered, especially toward the Galactic bulge. High stellar density combined with high and differential interstellar reddening are the two major problems for finding globular clusters located toward the bulge. We use the deep near-IR photometry of the VISTA Variables in the Vía Láctea (VVV) Survey to search for globular clusters projected toward the Galactic bulge, and hereby report the discovery of 22 new candidate globular clusters. These objects, detected as high density regions in our maps of bulge red giants, are confirmed as globular cluster candidates by their color–magnitude diagrams. We provide their coordinates as well as their near-IR color–magnitude diagrams, from which some basic parameters are derived, such as reddenings and heliocentric distances. The color–magnitude diagrams reveal well defined red giant branches in all cases, often including a prominent red clump. The new globular cluster candidates exhibit a variety of extinctions (0.06 < A {sub Ks} < 2.77) and distances (5.3 < D < 9.5 kpc). We also classify the globular cluster candidates into 10 metal-poor and 12 metal-rich clusters, based on the comparison of their color–magnitude diagrams with those of known globular clusters also observed by the VVV Survey. Finally, we argue that the census for Galactic globular clusters still remains incomplete, and that many more candidate globular clusters (particularly the low luminosity ones) await to be found and studied in detail in the central regions of the Milky Way.

  1. Brain asymmetry in the white matter making and globularity

    Directory of Open Access Journals (Sweden)

    Constantina eTheofanopoulou

    2015-09-01

    Full Text Available Recent studies from the field of language genetics and evolutionary anthropology have put forward the hypothesis that the emergence of our species-specific brain is to be understood not in terms of size, but in light of developmental changes that gave rise to a more globular braincase configuration after the split from Neanderthals-Denisovans. On the grounds that (i white matter myelination is delayed relative to other brain structures and in humans is protracted compared with other primates and (ii neural connectivity is linked genetically to our brain/skull morphology and language-ready brain, I take it that one significant evolutionary change in Homo sapiens’ lineage is the interhemispheric connectivity mediated by the Corpus Callosum. The size, myelination and fiber caliber of the Corpus Callosum presents an anterior-to-posterior increase, in a way that inter-hemispheric connectivity is more prominent in the sensory motor areas, whereas high- order areas are more intra-hemispherically connected. Building on evidence from language-processing studies that account for this asymmetry (‘lateralization’ in terms of brain rhythms, I present an evo-devo hypothesis according to which the myelination of the Corpus Callosum, Brain Asymmetry and Globularity are conjectured to make up the angles of a co-evolutionary triangle that gave rise to our language-ready brain.

  2. Golden triangle for folding rates of globular proteins.

    Science.gov (United States)

    Garbuzynskiy, Sergiy O; Ivankov, Dmitry N; Bogatyreva, Natalya S; Finkelstein, Alexei V

    2013-01-02

    The ability of protein chains to spontaneously form their spatial structures is a long-standing puzzle in molecular biology. Experimentally measured rates of spontaneous folding of single-domain globular proteins range from microseconds to hours: the difference (11 orders of magnitude) is akin to the difference between the life span of a mosquito and the age of the universe. Here, we show that physical theory with biological constraints outlines a "golden triangle" limiting the possible range of folding rates for single-domain globular proteins of various size and stability, and that the experimentally measured folding rates fall within this narrow triangle built without any adjustable parameters, filling it almost completely. In addition, the golden triangle predicts the maximal size of protein domains that fold under solely thermodynamic (rather than kinetic) control. It also predicts the maximal allowed size of the "foldable" protein domains, and the size of domains found in known protein structures is in a good agreement with this limit.

  3. Comparing Chemical Compositions of Dwarf Elliptical Galaxies and Globular Clusters

    Science.gov (United States)

    Chu, Jason; Sparkman, Lea; Toloba, Elisa; Guhathakurta, Puragra

    2015-01-01

    Because of their abundance in cluster environments and fragility due to their low mass, dwarf elliptical galaxies (dEs) are excellent specimens for studying the physical processes that occur inside galaxy clusters. These studies can be used to expand our understanding of the process of galaxy (specifically dE) formation and the role of dark matter in the Universe. To move closer to better understanding these topics, we present a study of the relationship between dEs and globular clusters (GCs) by using the largest sample of dEs and GC satellites to date. We focus on comparing the ages and chemical compositions of dE nuclei with those of satellite GCs by analyzing absorption lines in their spectra. To better view the spectral features of these relatively dim objects, we employ a spectral co-addition process, where we add the fluxes of several objects to produce a single spectrum with high signal-to-noise ratio. Our finding that dE nuclei are younger and more metal rich than globular clusters establishes important benchmarks that future dE formation theories will consider. We also establish a means to identify GCs whose parent galaxies are uncertain, which allows us to make comparisons between this GC group and the satellite GCs.

  4. Color Gradients Within Globular Clusters: Restricted Numerical Simulation

    Directory of Open Access Journals (Sweden)

    Young-Jong Sohn

    1997-06-01

    Full Text Available The results of a restricted numerical simulation for the color gradients within globular clusters have been presented. The standard luminosity function of M3 and Salpeter's initial mass functions were used to generate model clusters as a fundamental population. Color gradients with the sample clusters for both King and power law cusp models of surface brightness distributions are discussed in the case of using the standard luminosity function. The dependence of color gradients on several parameters for the simulations with Salpeter's initial mass functions, such as slope of initial mass functions, cluster ages, metallicities, concentration parameters of King model, and slopes of power law, are also discussed. No significant radial color gradients are shown to the sample clusters which are regenerated by a random number generation technique with various parameters in both of King and power law cusp models of surface brightness distributions. Dynamical mass segregation and stellar evolution of horizontal branch stars and blue stragglers should be included for the general case of model simulations to show the observed radial color gradients within globular clusters.

  5. Self-Assembly of Globular Protein-Polymer Diblock Copolymers

    Science.gov (United States)

    Thomas, C. S.; Olsen, B. D.

    2011-03-01

    The self-assembly of globular protein-polymer diblock copolymers into nanostructured phases is demonstrated as an elegant and simple method for structural control in biocatalysis or bioelectronics. In order to fundamentally investigate self-assembly in these complex block copolymer systems, a red fluorescent protein was expressed in E. coli and site-specifically conjugated to a low polydispersity poly(N-isopropyl acrylamide) (PNIPAM) block using thiol-maleimide coupling to form a well-defined model globular protein-polymer diblock. Functional protein materials are obtained by solvent evaporation and solvent annealing above and below the lower critical solution temperature of PNIPAM in order to access different pathways toward self-assembly. Small angle x-ray scattering and microscopy are used to show that the diblock forms lamellar nanostructures and to explore dependence of nanostructure formation on processing conditions. Circular dichroism and UV-vis show that a large fraction of the protein remains in its folded state after conjugation, and wide angle x-ray scattering demonstrates that diblock copolymer self-assembly changes the protein packing symmetry.

  6. Theoretical stellar luminosity functions and globular cluster ages and compositions

    Science.gov (United States)

    Ratcliff, S. J.

    The ages and chemical compositions of the stars in globular clusters are of great interest, particularly because age estimates from the well known exercise of fitting observed color-magnitude diagrams to theoretical predictions tend to yield ages in excess of the Hubble time in standard cosmological models. Relatively little use was made of the stellar luminosity functions of the globular clusters to constrain the ages or compositions. The comparison of observed luminosity functions to theoretical ones allows the use of information not usually considered, and has the advantage of being relatively insensitive to lack of knowledge of the detailed structure of stellar envelopes and atmospheres. A computer program was developed to apply standard stellar evolutionary theory, using the most recently available input physics to the calculation of the evolution of low-mass Population II stars. A comparison of the computed theoretical luminosity functions to an observed, though still preliminary, luminosity function for the cluster M13 demonstrates the viability of this approach.

  7. SEARCH FOR RED DWARF STARS IN GLOBULAR CLUSTER NGC 6397

    Science.gov (United States)

    2002-01-01

    Left A NASA Hubble Space Telescope image of a small region (1.4 light-years across) in the globular star cluster NGC 6397. Simulated stars (diamonds) have been added to this view of the same region of the cluster to illustrate what astronomers would have expected to see if faint red dwarf stars were abundant in the Milky Way Galaxy. The field would then contain 500 stars, according to theoretical calculations. Right The unmodified HST image shows far fewer stars than would be expected, according to popular theories of star formation. HST resolves about 200 stars. The stellar density is so low that HST can literally see right through the cluster and resolve far more distant background galaxies. From this observation, scientists have identified the surprising cutoff point below which nature apparently doesn't make many stars smaller that 1/5 the mass of our Sun. These HST findings provide new insights into star formation in our Galaxy. Technical detail:The globular cluster NGC 6397, one of the nearest and densest agglomerations of stars, is located 7,200 light-years away in the southern constellation Ara. This visible-light picture was taken on March 3, 1994 with the Wide Field Planetary Camera 2, as part the HST parallel observing program. Credit: F. Paresce, ST ScI and ESA and NASA

  8. THE FIRST CONFIRMED MICROLENS IN A GLOBULAR CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Pietrukowicz, P.; Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Minniti, D.; Alonso-Garcia, J. [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Av. Vicuna MacKenna 4860, Casilla 306, Santiago 22 (Chile); Jetzer, Ph. [Institut fuer Theoretische Physik, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland)

    2012-01-10

    In 2000 July/August a microlensing event occurred at a distance of 2.'33 from the center of the globular cluster M22 (NGC 6656), observed against the dense stellar field of the Milky Way bulge. We have used the adaptive optics system NACO at the ESO Very Large Telescope to resolve the two objects that participated in the event: the lens and the source. The position of the objects measured in 2011 July is in agreement with the observed relative proper motion of M22 with respect to the background bulge stars. Based on the brightness of the microlens components we find that the source is a solar-type star located at a distance of 6.0 {+-} 1.5 kpc in the bulge, while the lens is a 0.18 {+-} 0.01 M{sub Sun} dwarf member of the globular cluster located at the known distance of 3.2 {+-} 0.2 kpc from the Sun.

  9. Long Period Variable Stars in Globular Cluster NGC 6553

    Science.gov (United States)

    Kager, Elisabeth

    2010-04-01

    Long period variable stars (LPVs) are red giants or supergiants that vary in brightness as they pulsate radially. Their periods range from months to several years, and amplitudes can be many magnitudes. Studying these pulsation properties of LPVs as a function of position on the giant branch helps to constrain models of stellar structure, evolution, and pulsation. Studying LPVs in environments with known metallicity, age, and distance allows us to control these variables; globular clusters are an excellent environment. This study targets the metal-rich ([Fe/H] = -0.2) bulge globular cluster NGC 6553 in which variables have not been studied very thoroughly. Over the past year, 49 nights worth of data have been taken with PROMPT 4, a motorized telescope positioned at Cerro Tololo, Chile. Images have been processed, combined, and photometered and the stars' (X,Y) positions and brightness values were determined. The variability indices of the magnitudes of the stars between nights were used to find LPVs and plot their brightness as a function of time. These light curves will be characterized for their amplitude, period, and regularity; these can be used to compare to LPVs in other clusters at the same/other metallicities. A color-magnitude diagram will be created onto which the LPVs' position can be plotted to understand how far they are up the red giant branch to get a better understanding of their evolutionary state.

  10. Combined Photometry and Spectroscopy of Globular Cluster Tidal Streams

    Science.gov (United States)

    Powell, W. L.; Wilhelm, R.; McWilliam, A.; Westfall, A.; Lauchner, A.

    2005-12-01

    Globular cluster tidal streams are of interest for what they can tell us of the dynamical evolution of the clusters and our Galaxy. Recent studies have used photometric and statistical subtraction methods to attempt to separate potential streams from the field stars that contaminate the samples. We chose instead to use photometry to select blue stars that match the horizontal branch of the clusters and make spectroscopic observations of these candidates to determine their metallicity and radial velocities. Combining these results with the photometric data offers a better picture of the structure and formation of tidal streams. We present preliminary photometric and spectroscopic results for the globular clusters and surrounding fields of NGC 6934, M 10, M 92 and Pal 13. Data obtained at McDonald Observatory, Kitt Peak, and Las Campanas Observatory. WLP acknowledges the support of a Sigma Xi Grant-In-Aid of research, and the Texas Space Grant Consortium Graduate Fellowship. RW acknowledges the support of a AAS Small Research Grant.

  11. A 'Rosetta Stone' to Interpret the UV-HST Photometry of Multiple Stellar Populations in Globular Clusters

    Science.gov (United States)

    Renzini, Alvio

    2011-10-01

    In this proposal we intend to firmly identify the chemical species responsible for the UV and UV-optical color differences exhibited by the multiple stellar populations harboured by two Galactic globular clusters: omega Centauri and 47 Tucanae, one with highly helium enriched sub-populations {omega Centauri}, the other not.We plan to collect ultraviolet STIS spectra for stars in the crowded cores of the clusters, where HST photometry is already available for thousands of stars in more than 10 filters, from F225W to F850LP. This WFC3+ACS photometric database has allowed us to show that UV colors are remarkably effective in separating the different cluster sub-populations, and with the proposed STIS spectroscopy we can quantify the chemical abundance differences among such sub-populations, most notably in Nitrogen and Oxygen. The resulting calibration of the UV colors in terms of CNO abundances will provide a new effective tool for the chemical characterization of large numbers of globular cluster stars belonging to the various sub-populations in each cluster, and to better isolate the specific role of the helium abundance.The plan is to observe at least one star for each of the main principal stellar sub-populations in each of the two clusters. These objects are selected on the basis of their accurate photometry and astrometry already in hand, based on existing UV-HST images.

  12. Ages of Globular Clusters from HIPPARCOS Parallaxes of Local Subdwarfs

    Science.gov (United States)

    Gratton, Raffaele G.; Fusi Pecci, Flavio; Carretta, Eugenio; Clementini, Gisella; Corsi, Carlo E.; Lattanzi, Mario

    1997-12-01

    We report here initial but strongly conclusive results for absolute ages of Galactic globular clusters (GGCs). This study is based on high-precision trigonometric parallaxes from the HIPPARCOS satellite coupled with accurate metal abundances ([Fe/H], [O/Fe], and [α/Fe]) from high-resolution spectroscopy for a sample of about thirty subdwarfs. Systematic effects due to star selection (Lutz-Kelker corrections to parallaxes) and the possible presence of undetected binaries in the sample of bona fide single stars are examined, and appropriate corrections are estimated. They are found to be small for our sample. The new data allow us to reliably define the absolute location of the main sequence (MS) as a function of metallicity. These results are then used to derive distances and ages for a carefully selected sample of nine globular clusters having metallicities determined from high-dispersion spectra of individual giants according to a procedure totally consistent with that used for the field subdwarfs. Very precise and homogeneous reddening values have also been independently determined for these clusters. Random errors for our distance moduli are +/-0.08 mag, and systematic errors are likely of the same order of magnitude. These very accurate distances allow us to derive ages with internal errors of ~12% (+/-1.5 Gyr). The main results are: 1. HIPPARCOS parallaxes are smaller than corresponding ground-based measurements, leading, in turn, to longer distance moduli (~0.2 mag) and younger ages (~2.8 Gyr). 2. The distance to NGC 6752 derived from our MS fitting is consistent with that determined using the white dwarf cooling sequence. 3. The relation between the zero-age HB (ZAHB) absolute magnitude and metallicity for the nine program clusters is MV(ZAHB)=(0.22+/-0.09)([Fe/H]+1.5)+(0.49+/-0.04) . This relation is fairly consistent with some of the most recent theoretical models. Within quoted errors, the slope is in agreement with that given by the Baade-Wesselink (BW

  13. Characterisation and outcomes of upper extremity amputations.

    Science.gov (United States)

    Tennent, David J; Wenke, Joseph C; Rivera, Jessica C; Krueger, Chad A

    2014-06-01

    The purpose of this study is to characterise the injuries, outcomes, and disabling conditions of the isolated, combat-related upper extremity amputees in comparison to the isolated lower extremity amputees and the general amputee population. A retrospective study of all major extremity amputations sustained by the US military service members from 1 October 2001 to 30 July 2011 was conducted. Data from the Department of Defense Trauma Registry, the Armed Forces Health Longitudinal Technology Application, and the Physical Evaluation Board Liaison Offices were queried in order to obtain injury characteristics, demographic information, treatment characteristics, and disability outcome data. A total of 1315 service members who sustained 1631 amputations were identified; of these, 173 service members were identified as sustaining an isolated upper extremity amputation. Isolated upper extremity and isolated lower extremity amputees had similar Injury Severity Scores (21 vs. 20). There were significantly more non-battle-related upper extremity amputees than the analysed general amputation population (39% vs. 14%). Isolated upper extremity amputees had significantly greater combined disability rating (82.9% vs. 62.3%) and were more likely to receive a disability rating >80% (69% vs. 53%). No upper extremity amputees were found fit for duty; only 12 (8.3%) were allowed continuation on active duty; and significantly more upper extremity amputees were permanently retired than lower extremity amputees (82% vs. 74%). The most common non-upper extremity amputation-related disabling condition was post-traumatic stress disorder (PTSD) (17%). Upper extremity amputees were significantly more likely to have disability from PTSD, 13% vs. 8%, and loss of nerve function, 11% vs. 6%, than the general amputee population. Upper extremity amputees account for 14% of all amputees during the Operation Enduring Freedom and Operation Iraqi Freedom conflicts. These amputees have significant

  14. Variability of rRNA Operon Copy Number and Growth Rate Dynamics of Bacillus Isolated from an Extremely Oligotrophic Aquatic Ecosystem

    Science.gov (United States)

    Valdivia-Anistro, Jorge A.; Eguiarte-Fruns, Luis E.; Delgado-Sapién, Gabriela; Márquez-Zacarías, Pedro; Gasca-Pineda, Jaime; Learned, Jennifer; Elser, James J.; Olmedo-Alvarez, Gabriela; Souza, Valeria

    2016-01-01

    physiology of this bacterial group under extreme oligotrophic conditions. PMID:26779143

  15. MASSIVE+: The Growth Histories of MASSIVE Survey Galaxies from their Globular Cluster Colors

    Science.gov (United States)

    Blakeslee, John

    2017-08-01

    The MASSIVE survey is targeting the 100 most massive galaxies within 108 Mpc that are visible in the northern sky. These most massive galaxies in the present-day universe reside in a surprisingly wide variety of environments, from rich clusters to fossil groups to near isolation. We propose to use WFC3/UVIS and ACS to carry out a deep imaging study of the globular cluster populations around a selected subset of the MASSIVE targets. Though much is known about GC systems of bright galaxies in rich clusters, we know surprisingly little about the effects of environment on these systems. The MASSIVE sample provides a golden opportunity to learn about the systematics of GC systems and what they can tell us about environmental drivers on the evolution of the highest mass galaxies. The most pressing questions to be addressed include: (1) Do isolated giants have the same constant mass fraction of GCs to total halo mass as BCGs of similar luminosity? (2) Do their GC systems show the same color (metallicity) distribution, which is an outcome of the mass spectrum of gas-rich halos during hierarchical growth? (3) Do the GCs in isolated high-mass galaxies follow the same radial distribution versus metallicity as in rich environments (a test of the relative importance of growth by accretion)? (4) Do the GCs of galaxies in sparse environments follow the same mass function? Our proposed second-band imaging will enable us to secure answers to these questions and add enormously to the legacy value of existing HST imaging of the highest mass galaxies in the universe.

  16. Detection of a large-scale structure of intracluster globular clusters in the Virgo cluster.

    Science.gov (United States)

    Lee, Myung Gyoon; Park, Hong Soo; Hwang, Ho Seong

    2010-04-16

    Globular clusters are usually found in galaxies, and they are excellent tracers of dark matter. Long ago it was suggested that intracluster globular clusters (IGCs) may exist that are bound to a galaxy cluster rather than to any single galaxy. Here we present a map showing the large-scale distribution of globular clusters over the entire Virgo cluster. It shows that IGCs are found out to 5 million light years from the Virgo center and that they are concentrated in several substructures that are much larger than galaxies. These objects might have been mostly stripped off from low-mass dwarf galaxies.

  17. Self-assembly dynamics for the transition of a globular aggregate to a fibril network of lysozyme proteins via a coarse-grained Monte Carlo simulation

    Directory of Open Access Journals (Sweden)

    R. B. Pandey

    2015-09-01

    Full Text Available The self-organizing dynamics of lysozymes (an amyloid protein with 148 residues with different numbers of protein chains, Nc = 1,5,10, and 15 (concentration 0.004 – 0.063 is studied by a coarse-grained Monte Carlo simulation with knowledge-based residue-residue interactions. The dynamics of an isolated lysozyme (Nc = 1 is ultra-slow (quasi-static at low temperatures and becomes diffusive asymptotically on raising the temperature. In contrast, the presence of interacting proteins leads to concentration induced protein diffusion at low temperatures and concentration-tempering sub-diffusion at high temperatures. Variation of the radius of gyration of the protein with temperature shows a systematic transition from a globular structure (at low T to a random coil (high T conformation when the proteins are isolated. The crossover from globular to random coil becomes sharper upon increasing the protein concentration (i.e. with Nc = 5,10, with larger Rg at higher temperatures and concentration; Rg becomes smaller on adding more protein chains (e.g. Nc = 15 a non-monotonic response to protein concentration. Analysis of the structure factor (S(q provides an estimate of the effective dimension (D ≥ 3, globular conformation at low temperature, and D ∼ 1.7, random coil, at high temperatures of the isolated protein. With many interacting proteins, the morphology of the self-assembly varies with scale, i.e. at the low temperature (T = 0.015, D ∼ 2.9 on the scale comparable to the radius of gyration of the protein, and D ∼ 2.3 at the large scale over the entire sample. The global network of fibrils appears at high temperature (T = 0.021 with D ∼ 1.7 (i.e. a random coil morphology at large scale involving tenuous distribution of micro-globules (at small scales.

  18. The Composition of the Bulge Globular Cluster NGC 6273

    Science.gov (United States)

    Pilachowski, C. A.; Johnson, C. I.; Rich, R. M.; Caldwell, N.; Mateo, M.; Bailey, J. I.; Crane, J. D.

    2017-03-01

    Observations of red giants in the Bulge globular cluster NGC 6273 with the Michigan/Magellan Fiber System (M2FS) mounted on the Nasmuth-East port of the Magellan-Clay 6.5-m telescope at the Las Campanas Observatory reveal a spread in metallicity. Members have been confirmed with radial velocity. NGC 6273 has at least two populations separated by 0.2-0.3 dex in [Fe/H]. The sodium and aluminum abundances are correlated while the magnesium and aluminum abundances are anti-correlated. The cluster also shows a rise in the abundance of the s-process element lanthanum with [Fe/H] similar to other massive clusters. The cluster contains a possible third population depleted in most elements by 0.3 dex.

  19. Anomalous globular clusters: insights from neutron capture elements abundances.

    Science.gov (United States)

    Marino, A. F.

    Thanks to the large amount of spectroscopic and photometric data assembled in the last couple of decades, the assumption that all globular clusters (GCs) contain a simple mono-metallic stellar population has been modified. Besides the common variations in the elements created/destroyed in the H-burning processes, spreads and/or multi-modalities in heavier elements have been detected in a few objects. Among the most remarkable chemical inhomogeneity in these anomalous objects is the internal variation in the neutron-capture (n-capture) elements, that can provide some information about the material from which stars were born. I report a summary of the chemical pattern observed in GCs where variations in n-capture have been detected, and the connection between these chemical features and the distribution of stars along the color-magnitude diagrams in the context of the lively debate on multiple stellar populations.

  20. How Black Holes Shape Globular Clusters: Modeling NGC 3201

    Science.gov (United States)

    Kremer, Kyle; Ye, Claire S.; Chatterjee, Sourav; Rodriguez, Carl L.; Rasio, Frederic A.

    2018-03-01

    Numerical simulations have shown that black holes (BHs) can strongly influence the evolution and present-day observational properties of globular clusters (GCs). Using a Monte Carlo code, we construct GC models that match the Milky Way cluster NGC 3201, the first cluster in which a stellar-mass BH was identified through radial velocity measurements. We predict that NGC 3201 contains ≳200 stellar-mass BHs. Furthermore, we explore the dynamical formation of main-sequence–BH binaries and demonstrate that systems similar to the observed BH binary in NGC 3201 are produced naturally. Additionally, our models predict the existence of bright blue straggler–BH binaries that are unique to core-collapsed clusters, which otherwise retain few BHs.

  1. Variable Stars in the LMC Globular Cluster NGC 1754

    Science.gov (United States)

    Kuehn, Charles A., III; Taylor, L.; Smith, H. A.; Catelan, M.; Pritzl, B. J.; De Lee, N.

    2006-12-01

    We have used BVI observations taken with the SMARTS 1.3m telescope and with the SOAR telescope to identify variable stars in the vicinity of the old LMC cluster NGC 1754. We present light curves and periods for the variables and classify the variables according to type. The probability that the RR Lyrae stars found in the neighborhood of NGC 1754 actually belong to the cluster is discussed. Unlike most globular clusters of the Milky Way halo, many of the old star clusters of the LMC have Oosterhoff intermediate properties. The Oosterhoff classification of field and cluster RR Lyrae stars near NGC 1754 is considered. We thank the NSF for partial support of this research.

  2. AGB subpopulations in the nearby globular cluster NGC 6397

    Science.gov (United States)

    MacLean, B. T.; Campbell, S. W.; De Silva, G. M.; Lattanzio, J.; D'Orazi, V.; Cottrell, P. L.; Momany, Y.; Casagrande, L.

    2018-03-01

    It has been well established that Galactic Globular clusters (GCs) harbour more than one stellar population, distinguishable by the anticorrelations of light-element abundances (C-N, Na-O, and Mg-Al). These studies have been extended recently to the asymptotic giant branch (AGB). Here, we investigate the AGB of NGC 6397 for the first time. We have performed an abundance analysis of high-resolution spectra of 47 red giant branch (RGB) and eight AGB stars, deriving Fe, Na, O, Mg, and Al abundances. We find that NGC 6397 shows no evidence of a deficit in Na-rich AGB stars, as reported for some other GCs - the subpopulation ratios of the AGB and RGB in NGC 6397 are identical, within uncertainties. This agrees with expectations from stellar theory. This GC acts as a control for our earlier work on the AGB of M4 (with contrasting results), since the same tools and methods were used.

  3. Kinematic fingerprint of core-collapsed globular clusters

    Science.gov (United States)

    Bianchini, P.; Webb, J. J.; Sills, A.; Vesperini, E.

    2018-03-01

    Dynamical evolution drives globular clusters towards core collapse, which strongly shapes their internal properties. Diagnostics of core collapse have so far been based on photometry only, namely on the study of the concentration of the density profiles. Here, we present a new method to robustly identify core-collapsed clusters based on the study of their stellar kinematics. We introduce the kinematic concentration parameter, ck, the ratio between the global and local degree of energy equipartition reached by a cluster, and show through extensive direct N-body simulations that clusters approaching core collapse and in the post-core collapse phase are strictly characterized by ck > 1. The kinematic concentration provides a suitable diagnostic to identify core-collapsed clusters, independent from any other previous methods based on photometry. We also explore the effects of incomplete radial and stellar mass coverage on the calculation of ck and find that our method can be applied to state-of-art kinematic data sets.

  4. Kinematic fingerprint of core-collapsed globular clusters

    Science.gov (United States)

    Bianchini, P.; Webb, J. J.; Sills, A.; Vesperini, E.

    2018-01-01

    Dynamical evolution drives globular clusters toward core collapse, which strongly shapes their internal properties. Diagnostics of core collapse have so far been based on photometry only, namely on the study of the concentration of the density profiles. Here we present a new method to robustly identify core-collapsed clusters based on the study of their stellar kinematics. We introduce the kinematic concentration parameter, ck, the ratio between the global and local degree of energy equipartition reached by a cluster, and show through extensive direct N-body simulations that clusters approaching core collapse and in the post-core collapse phase are strictly characterized by ck > 1. The kinematic concentration provides a suitable diagnostic to identify core-collapsed clusters, independent from any other previous methods based on photometry. We also explore the effects of incomplete radial and stellar mass coverage on the calculation of ck and find that our method can be applied to state-of-art kinematic datasets.

  5. Globular conformation of some ribosomal proteins in solution

    International Nuclear Information System (INIS)

    Serdyuk, I.N.; Spirin, A.S.

    1978-01-01

    The possibility that such RNA-binding proteins of the 30 S subparticle as S4, S7, S8 and S16 exist in the form of compact globules in solution has been explored experimentally. These proteins have been studied in D 2 O solution by neutron scattering to measure their radii of gyration. This type of radiation using D 2 O as a solvent provides the maximum 'contrast', that is the maximum difference between the scattering of the protein and the solvent. It allowed measurements to be made using protein at <= 1.5 mg/ml. The radii of gyration for the ribosomal proteins S4, S7, S8 and S16 were found to be relatively small corresponding to the radii of gyration of compact globular proteins of the same molecular weights. (Auth.)

  6. SHRINKING THE BRANEWORLD: BLACK HOLE IN A GLOBULAR CLUSTER

    International Nuclear Information System (INIS)

    Gnedin, Oleg Y.; Maccarone, Thomas J.; Psaltis, Dimitrios; Zepf, Stephen E.

    2009-01-01

    Large extra dimensions have been proposed as a possible solution to the hierarchy problem in physics. In one of the suggested models, the RS2 braneworld model, black holes may evaporate by Hawking radiation faster than in general relativity, on a timescale that depends on the black hole mass and on the asymptotic radius of curvature of the extra dimensions. Thus the size of the extra dimensions can be constrained by astrophysical observations. Here we point out that the black hole, recently discovered in an extragalactic globular cluster, places the strongest upper limit on the size of the extra dimensions in the RS2 model, L ∼< 0.003 mm. This black hole has the virtues of old age and relatively small mass. The derived upper limit is within an order of magnitude of the absolute limit afforded by astrophysical observations of black holes.

  7. The direct piezoelectric effect in the globular protein lysozyme

    Science.gov (United States)

    Stapleton, A.; Noor, M. R.; Sweeney, J.; Casey, V.; Kholkin, A. L.; Silien, C.; Gandhi, A. A.; Soulimane, T.; Tofail, S. A. M.

    2017-10-01

    Here, we present experimental evidence of the direct piezoelectric effect in the globular protein, lysozyme. Piezoelectric materials are employed in many actuating and sensing applications because they can convert mechanical energy into electrical energy and vice versa. Although originally studied in inorganic materials, several biological materials including amino acids and bone, also exhibit piezoelectricity. The exact mechanisms supporting biological piezoelectricity are not known, nor is it known whether biological piezoelectricity conforms strictly to the criteria of classical piezoelectricity. The observation of piezoelectricity in protein crystals presented here links biological piezoelectricity with the classical theory of piezoelectricity. We quantify the direct piezoelectric effect in monoclinic and tetragonal aggregate films of lysozyme using conventional techniques based on the Berlincourt Method. The largest piezoelectric effect measured in a crystalline aggregate film of lysozyme was approximately 6.5 pC N-1. These findings raise fundamental questions as to the possible physiological significance of piezoelectricity in lysozyme and the potential for technical applications.

  8. Interactions between globular proteins and procyanidins of different degrees of polymerization

    NARCIS (Netherlands)

    Prigent, S.V.E.; Voragen, A.G.J.; Koningsveld, van G.A.; Baron, A.; Renard, C.M.; Gruppen, H.

    2009-01-01

    Interactions of proteins with phenolic compounds occur in food products containing vegetable sources, such as cocoa, cereals, or yogurts containing fruit. Such interactions can modify protein digestion and protein industrial properties. Noncovalent interactions between globular proteins (proteins

  9. Engineering Globular Protein Vesicles through Tunable Self-Assembly of Recombinant Fusion Proteins.

    Science.gov (United States)

    Jang, Yeongseon; Choi, Won Tae; Heller, William T; Ke, Zunlong; Wright, Elizabeth R; Champion, Julie A

    2017-09-01

    Vesicles assembled from folded, globular proteins have potential for functions different from traditional lipid or polymeric vesicles. However, they also present challenges in understanding the assembly process and controlling vesicle properties. From detailed investigation of the assembly behavior of recombinant fusion proteins, this work reports a simple strategy to engineer protein vesicles containing functional, globular domains. This is achieved through tunable self-assembly of recombinant globular fusion proteins containing leucine zippers and elastin-like polypeptides. The fusion proteins form complexes in solution via high affinity binding of the zippers, and transition through dynamic coacervates to stable hollow vesicles upon warming. The thermal driving force, which can be tuned by protein concentration or temperature, controls both vesicle size and whether vesicles are single or bi-layered. These results provide critical information to engineer globular protein vesicles via self-assembly with desired size and membrane structure. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Marasmioid and gymnopoid fungi of the Republic of Korea. 2. Marasmius sect. Globulares.

    Science.gov (United States)

    Antonín, V; Ryoo, R; Shin, H-D

    2010-06-01

    Seven species of Marasmius sect. Globulares with smooth pileipellis cells (sect. Globulares s. Singer) have been collected in the Republic of Korea (South Korea) to date, viz. M. aurantioferrugineus, M. brunneospermus, M. maximus, M. nivicola, M. purpureostriatus, M. wynneae and M. fusicystidiosus. Descriptions of their macro- and microscopic features with a discussion of similar taxa are given. Their taxonomic position was confirmed using DNA data. Marasmius fusicystidiosus is described as a new species. A key to aid in their identification is also provided.

  11. Identification of α-amylase by random and specific mutagenesis of Texcoconibacillus texcoconensis 13CCT strain isolated from extreme alkaline-saline soil of the former Lake Texcoco (Mexico).

    Science.gov (United States)

    Bello-López, Juan Manuel; Navarro-Noya, Yendi E; Gómez-Acata, Selene; Hernández-Montañez, Zahuiti; Dendooven, Luc

    2014-05-01

    The alkaline α-amylase produced by Texcoconibacillus texcoconensis 13CC(T) strain was identified by random mutagenesis and confirmed by directed mutagenesis. A transposon mutagenesis approach was taken to identify the gene responsible for the degradation of starch in T. texcoconensis 13CC(T) strain. The deduced amino acids of the amy gene had a 99% similarity with those of Bacillus selenitireducens MLS10 and 97% with those of Paenibacillus curdlanolyticus YK9. The enzyme showed a maximum activity of 131.1 U/mL at 37 °C and pH 9.5 to 10.5. In situ activity of the enzyme determined by polyacrylamide gel electrophoresis showed only one band with amylolytic activity. This is the first report of a bacterium isolated from the extreme alkaline-saline soil of the former Lake Texcoco (Mexico) with amylolytic activity in alkaline conditions while its potential as a source of amylases for the industry is discussed.

  12. On the determination of the He abundance distribution in globular clusters from the width of the main sequence

    Science.gov (United States)

    Cassisi, Santi; Salaris, Maurizio; Pietrinferni, Adriano; Hyder, David

    2017-01-01

    One crucial piece of information to study the origin of multiple stellar populations in globular clusters is the range of initial helium abundances ΔY amongst the sub-populations hosted by each cluster. These estimates are commonly obtained by measuring the width in colour of the unevolved main sequence in an optical colour-magnitude diagram (CMD). The measured colour spread is then compared with predictions from theoretical stellar isochrones with varying initial He abundances to determine ΔY. The availability of UV/optical magnitudes, thanks to the Hubble Space Telescope UV Legacy Survey of Galactic GCs project, will allow the homogeneous determination of ΔY for a large Galactic globular cluster sample. From a theoretical point of view, accurate UV CMDs can efficiently disentangle the various sub-populations, and main sequence colour differences in the ACS F606W - (F606W - F814W) diagram allow an estimate of ΔY. We demonstrate that from a theoretical perspective, the (F606W - F814W) colour is an extremely reliable He-abundance indicator. The derivative dY/d(F606W - F814W), computed at a fixed luminosity along the unevolved main sequence, is largely insensitive to the physical assumptions made in stellar model computations, being more sensitive to the choice of the bolometric correction scale, and is only slightly dependent on the adopted set of stellar models. From a theoretical point of view, the (F606W - F814W) colour width of the cluster main sequence is therefore a robust diagnostic of the ΔY range.

  13. Sulphur in the metal poor globular cluster NGC 6397

    Science.gov (United States)

    Koch, A.; Caffau, E.

    2011-10-01

    Sulphur (S) is a non-refractory α-element that is not locked into dust grains in the interstellar medium. Thus no correction to the measured, interstellar sulphur abundance is needed and it can be readily compared to the S content in stellar photospheres. Here we present the first measurement of sulphur in the metal poor globular cluster (GC) NGC 6397, as detected in a MIKE/Magellan high signal-to-noise, high-resolution spectrum of one red giant star. While abundance ratios of sulphur are available for a larger number of Galactic stars down to an [Fe/H] of ~ -3.5 dex, no measurements in globular clusters more metal poor than -1.5 dex have been reported so far. We find aNLTE, 3-D abundance ratio of [S/Fe] = +0.52 ± 0.20 (stat.) ± 0.08 (sys.), based on theS I, Multiplet 1 line at 9212.8 Å. This value is consistent with a Galactic halo plateau as typical of other α-elements in GCs and field stars, but we cannot rule out its membership with a second branch of increasing [S/Fe] with decreasing [Fe/H], claimed in the literature, which leads to a large scatter at metallicities around - 2 dex. The [S/Mg] and [S/Ca] ratios in this star are compatible with a Solar value to within the (large) uncertainties. Despite the very large scatter in these ratios across Galactic stars between literature samples, this indicates that sulphur traces the chemical imprints of the other α-elements in metal poor GCs. Combined with its moderate sodium abundance ([S/Na]NLTE = 0.48), the [S/Fe] ratio in this GC extends a global, positive S-Na correlation that is not seen in field stars and might indicate that proton-capture reactions contributed to the production of sulphur in the (metal poor) early GC environments. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  14. Dynamics, Chemical Abundances, and ages of Globular Clusters in the Virgo Cluster of Galaxies

    Science.gov (United States)

    Guhathakurta, Puragra; NGVS Collaboration

    2018-01-01

    We present a study of the dynamics, metallicities, and ages of globular clusters (GCs) in the Next Generation Virgo cluster Survey (NGVS), a deep, multi-band (u, g, r, i, z, and Ks), wide-field (104 deg2) imaging survey carried out using the 3.6-m Canada-France-Hawaii Telescope and MegaCam imager. GC candidates were selected from the NGVS survey using photometric and image morphology criteria and these were followed up with deep, medium-resolution, multi-object spectroscopy using the Keck II 10-m telescope and DEIMOS spectrograph. The primary spectroscopic targets were candidate GC satellites of dwarf elliptical (dE) and ultra-diffuse galaxies (UDGs) in the Virgo cluster. While many objects were confirmed as GC satellites of Virgo dEs and UDGs, many turned out to be non-satellites based on their radial velocity and/or positional mismatch any identifiable Virgo cluster galaxy. We have used a combination of spectral characteristics (e.g., presence of absorption vs. emission lines), new Gaussian mixture modeling of radial velocity and sky position data, and a new extreme deconvolution analysis of ugrizKs photometry and image morphology, to classify all the objects in our sample into: (1) GC satellites of dE galaxies, (2) GC satellites of UDGs, (3) intra-cluster GCs (ICGCs) in the Virgo cluster, (4) GCs in the outer halo of the central cluster galaxy M87, (5) foreground Milky Way stars, and (6) distant background galaxies. We use these data to study the dynamics and dark matter content of dE and UDGs in the Virgo cluster, place important constraints on the nature of dE nuclei, and study the origin of ICGCs versus GCs in the remote M87 halo.We are grateful for financial support from the NSF and NASA/STScI.

  15. The Cluster AgeS Experiment (CASE). Variable Stars in the Field of the Globular Cluster M22

    Science.gov (United States)

    Rozyczka, M.; Thompson, I. B.; Pych, W.; Narloch, W.; Poleski, R.; Schwarzenberg-Czerny, A.

    2017-09-01

    The field of the globular cluster M22 (NGC 6656) was monitored between 2000 and 2008 in a search for variable stars. BV light curves were obtained for 359 periodic, likely periodic, and long-term variables, 238 of which are new detections. 39 newly detected variables, and 63 previously known ones are members or likely members of the cluster, including 20 SX Phe, 10 RRab and 16 RRc type pulsators, one BL Her type pulsator, 21 contact binaries, and 9 detached or semi-detached eclipsing binaries. The most interesting among the identified objects are V112 - a bright multimode SX Phe pulsator, V125 - a β Lyr type binary on the blue horizontal branch, V129 - a blue/yellow straggler with a W UMa-like light curve, located halfway between the extreme horizontal branch and red giant branch, and V134 - an extreme horizontal branch object with P=2.33 d and a nearly sinusoidal light curve. All four of them are proper motion members of the cluster. Among nonmembers, a P=2.83 d detached eclipsing binary hosting a δ Sct type pulsator was found, and a peculiar P=0.93 d binary with ellipsoidal modulation and narrow minimum in the middle of one of the descending shoulders of the sinusoid. We also collected substantial new data for previously known variables. In particular we revise the statistics of the occurrence of the Blazhko effect in RR Lyr type variables of M22.

  16. Cortactin Adopts a Globular Conformation and Bundles Actin into Sheets

    Energy Technology Data Exchange (ETDEWEB)

    Cowieson, Nathan P.; King, Gordon; Cookson, David; Ross, Ian; Huber, Thomas; Hume, David A.; Kobe, Bostjan; Martin, Jennifer L. (Queensland); (Aust. Synch.)

    2008-08-21

    Cortactin is a filamentous actin-binding protein that plays a pivotal role in translating environmental signals into coordinated rearrangement of the cytoskeleton. The dynamic reorganization of actin in the cytoskeleton drives processes including changes in cell morphology, cell migration, and phagocytosis. In general, structural proteins of the cytoskeleton bind in the N-terminal region of cortactin and regulatory proteins in the C-terminal region. Previous structural studies have reported an extended conformation for cortactin. It is therefore unclear how cortactin facilitates cross-talk between structural proteins and their regulators. In the study presented here, circular dichroism, chemical cross-linking, and small angle x-ray scattering are used to demonstrate that cortactin adopts a globular conformation, thereby bringing distant parts of the molecule into close proximity. In addition, the actin bundling activity of cortactin is characterized, showing that fully polymerized actin filaments are bundled into sheet-like structures. We present a low resolution structure that suggests how the various domains of cortactin interact to coordinate its array of binding partners at sites of actin branching.

  17. The X-ray globular cluster NGC 1851

    CERN Document Server

    Alcaino, G

    1976-01-01

    A BV photometric investigation of the Southern Globular Cluster NGC 1851, was carried out using the 1 m telescope of Cerro La Silla (ESO) for the photoelectric work and the 1 m telescope of Cerro Las Campanas (CARSO) for the photographic work. Nineteen stars were observed photoelectrically, the limiting magnitude being V=16.18. Using this sequence, 156 stars were measured photographically. The derived apparent distance modulus is (m-M)/sub app/=15/sup m/.50. The reddening is E(B-V)=0/sup m/.10. The true distance modulus is (m-M) /sub 0/=15/sup m/.20. The distance is 11 kpc from the sun, 6 kpc from the galactic plane and 17 kpc from the galactic centre. The main features of the colour-magnitude diagram are: a well defined horizontal branch abundant in red stars and deficient in blue stars, a rich subgiant and asymptotic branch and a moderately populated red giant branch of medium steepness rising to Delta V=2/sup m/.5 at (B-V) /sub 0/=1.4. At the distance of 11 kpc the maximum observed luminosity of the X-ray ...

  18. Helium enhancements in globular cluster stars from AGB star pollution .

    Science.gov (United States)

    Karakas, A.; Fenner, Y.; Sills, Alison; Campbell, S. W.; Lattanzio, J. C.

    Using a chemical evolution model we investigate the intriguing suggestion that there are populations of stars in some globular clusters (e.g. NGC 2808, omega Centauri) with enhanced levels of helium (Y ˜ 0.28 to 0.40) compared to the majority of the population that presumably have a primordial helium abundance. We assume that a previous generation of massive low-metallicity Asymptotic Giant Branch (AGB) stars has polluted the cluster gas via a slow stellar wind. We use two independent sets of AGB yields computed from detailed models to follow the evolution of helium, carbon, nitrogen and oxygen in the cluster gas using a Salpeter initial mass function (IMF) and a number of top-heavy IMFs. In no case were we able to fit the observational constraints, Y > 0.30 and C+N+O ≈ constant. Depending on the shape of the IMF and the yields, we either obtained Y gtrsim 0.30 and large increases in C+N+O or Y responsible for the large helium enrichment or that any dredge-up from this generation of stars was less than predicted by standard models.

  19. Study of Remote Globular Cluster Satellites of M87

    Science.gov (United States)

    Sahai, Arushi; Shao, Andrew; Toloba, Elisa; Guhathakurta, Puragra; Peng, Eric W.; Zhang, Hao

    2017-01-01

    We present a sample of “orphan” globular clusters (GCs) with previously unknown parent galaxies, which we determine to be remote satellites of M87, a massive elliptical galaxy at the center of the Virgo Cluster of Galaxies. Because GCs were formed in the early universe along with their original parent galaxies, which were cannibalized by massive galaxies such as M87, they share similar age and chemical properties. In this study, we first confirm that M87 is the adoptive parent galaxy of our orphan GCs using photometric and spectroscopic data to analyze spatial and velocity distributions. Next, we increase the signal-to-noise ratio of our samples’ spectra through a process known as coaddition. We utilize spectroscopic absorption lines to determine the age and metallicity of our orphan GCs through comparison to stellar population synthesis models, which we then relate to the GCs’ original parent galaxies using a mass-metallicity relation. Our finding that remote GCs of M87 likely developed in galaxies with ~1010 solar masses implies that M87’s outer halo is formed of relatively massive galaxies, serving as important parameters for developing theories about the formation and evolution of massive galaxies.This research was funded in part by NASA/STScI and the National Science Foundation. Most of this work was carried out by high school students working under the auspices of the Science Internship Program at UC Santa Cruz.

  20. KINEMATICS OF OUTER HALO GLOBULAR CLUSTERS IN M31

    International Nuclear Information System (INIS)

    Veljanoski, J.; Ferguson, A. M. N.; Bernard, E. J.; Peñarrubia, J.; Mackey, A. D.; Huxor, A. P.; Irwin, M. J.; Chapman, S. C.; Côté, P.; Tanvir, N. R.; McConnachie, A.; Ibata, R. A.; Martin, N. F.; Fardal, M.; Lewis, G. F.

    2013-01-01

    We present the first kinematic analysis of the far outer halo globular cluster (GC) population in the Local Group galaxy M31. Our sample contains 53 objects with projected radii of ∼20-130 kpc, 44 of which have no previous spectroscopic information. GCs with projected radii ∼> 30 kpc are found to exhibit net rotation around the minor axis of M31, in the same sense as the inner GCs, albeit with a smaller amplitude of 79 ± 19 km s –1 . The rotation-corrected velocity dispersion of the full halo GC sample is 106 ± 12 km s –1 , which we observe to decrease with increasing projected radius. We find compelling evidence for kinematic coherence among GCs that project on top of halo substructure, including a clear signature of infall for GCs lying along the northwest stream. Using the tracer mass estimator, we estimate the dynamical mass of M31 within 200 kpc to be M M31 = (1.2-1.5) ± 0.2 × 10 12 M ☉ . This value is highly dependent on the chosen model and assumptions within.

  1. THE DISCOVERY OF REMOTE GLOBULAR CLUSTERS IN M33

    International Nuclear Information System (INIS)

    Huxor, A.; Ferguson, A. M. N.; Barker, M. K.; Tanvir, N. R.; Irwin, M. J.; Chapman, S. C.; Ibata, R.; Lewis, G.

    2009-01-01

    We present the discovery of four remote star clusters in M33, one of which is of an extended nature. Three of the clusters were discovered using survey data from the Isaac Newton Telescope Wide-Field Camera while one was discovered serendipitously in a deep image taken with the Hubble Space Telescope's Advanced Camera for Surveys. With projected radii of 38-113 arcmin (9.6-28.5 kpc for an assumed M33 distance of 870 kpc), these clusters lie significantly beyond all but one of the currently confirmed clusters in M33. The clusters have magnitudes and colors consistent with their being old to intermediate-age globular clusters (GCs). Indeed, they bear a strong resemblance to the outer halo GC population of the Milky Way and M31 in terms (V - I) 0 color. The three outermost clusters are projected on the far side of M33 with respect to M31, an asymmetry that could suggest tidal interactions have affected M33's GC distribution at large radii.

  2. Color Gradient in the King Type Globular Cluster NGC 7089

    Directory of Open Access Journals (Sweden)

    Young-Jong Sohn

    1999-12-01

    Full Text Available We use BV CCD images to investigate the reality of the color gradient within a King type globular cluster NGC 7089. Surface photometry shows that there is a strong radial color gradient in the central region of the cluster in the sense of bluer center with the amplitude of -0.39 +/- 0.07 mag/arcsec2 in (B - V. In the outer region of the cluster, however, the radial color gradient shows a reverse case, i.e., redder toward the center. (B - V color profile which was derived from resolved stars in VGC 7089 field also shows a significant color gradient in the central region of the clusters, indicating that lights from the combination of red giant stars and blue horizontal branch stars cause the radial color gradient. Color gradient of the outer region of NGC 7089 may be due to the unresolved background of the cluster. Similar color gradients in the central area of clusters have been previously observed exserved exclusively in highly concentrated systems classified as post core collapse clusters. We caution, however, to confirm the reality of the color gradient from resolved stars, we need more accurate imaging data of the cluster with exceptional seeing condition because the effect of completeness correlates with local density of stars.

  3. Dynamics of gravitational systems: Globular clusters and dark matter halos

    International Nuclear Information System (INIS)

    Oh, K.

    1989-01-01

    The evolution of globular clusters is investigated using a combination of the modified Fokker-Plank equation and numerical integrations of N-body systems. The orbit-averaged diffusion coefficients in the inner region of the cluster and integrated orbits of the stars in the outer region are used. The King-Michie distribution is adopted as an initial model. Both isotropic and anisotropic cases are examined. The following was found. There is no orbital phase dependence of tidal radius of clusters in eccentric orbits. The number of stars with retrograde orbits is similar to the number with prograde orbits inside the tidal radius for the isotropic case. Escape rates are similar to those found in previous work for the isotropic case but considerably smaller in the anisotropic case. Disk shocking is very efficient isotropizing the orbits of stars in the outer region of the cluster in the anisotropic case. The response of dark matter galactic halos during the dissipational collapse of the baryonic matter are investigated. N-body simulations are used with the total mass and z-component of angular momentum conserved. Then the baryonic matter is forced to contract, forming the final luminous components of the galaxy. Both slow and fast growth of the luminous components are considered. Relatively flat rotation curves are easily obtained for reasonable values of the free parameters. There is no significant difference between slow collapse and fast collapse for all these results

  4. The variable star population in the globular cluster NGC 6934

    Science.gov (United States)

    Yepez, M. A.; Arellano Ferro, A.; Muneer, S.; Giridhar, Sunetra

    2018-04-01

    We report an analysis of new V and I CCD time-series photometry of the globular cluster NGC 6934. Through the Fourier decomposition of the RR Lyrae light curves the mean values of [Fe/H] and the distance of the cluster were estimated; we found: [Fe/H]UVES = - 1.48 ± 0.14 and d = 16.03 ± 0.42 kpc, and [Fe/H]UVES = - 1.43 ± 0.11 and d = 15.91 ± 0.39 kpc, from the calibrations of RRab and RRc stars respectively. Independent distance estimations from SX Phe and SR stars are also discussed. Individual absolute magnitudes, radii and masses are also reported for RR Lyrae stars. We found 12 new variables: 4 RRab, 3 SX Phe, 2 W Virginis (CW) and 3 semi-regular (SR). The inter-mode or "either-or" region in the instability strip is shared by the RRab and RRc stars. This characteristic, observed only in some OoI clusters and never seen in an OoII, is discussed in terms of mass distribution in the ZAHB.

  5. A study of rotating globular clusters. The case of the old, metal-poor globular cluster NGC 4372

    Science.gov (United States)

    Kacharov, N.; Bianchini, P.; Koch, A.; Frank, M. J.; Martin, N. F.; van de Ven, G.; Puzia, T. H.; McDonald, I.; Johnson, C. I.; Zijlstra, A. A.

    2014-07-01

    Context. NGC 4372 is a poorly studied old, very metal-poor globular cluster (GC) located in the inner Milky Way halo. Aims: We present the first in-depth study of the kinematic properties and derive the structural parameters of NGC 4372 based on the fit of a Plummer profile and a rotating, physical model. We explore the link between internal rotation to different cluster properties and together with similar studies of more GCs, we put these in the context of globular cluster formation and evolution. Methods: We present radial velocities for 131 cluster member stars measured from high-resolution FLAMES/GIRAFFE observations. Their membership to the GC is additionally confirmed from precise metallicity estimates. We build a velocity dispersion profile and a systemic rotation curve using this kinematic data set. Additionally, we obtain an elliptical number density profile of NGC 4372 based on optical images using a Markov chain Monte Carlo fitting algorithm. From this, we derive the cluster's half-light radius and ellipticity as rh = 3.44' ± 0.04' and ɛ = 0.08 ± 0.01. Finally, we give a physical interpretation of the observed morphological and kinematic properties of this GC by fitting an axisymmetric, differentially rotating, dynamical model. Results: Our results show that NGC 4372 has an unusually high ratio of rotation amplitude to velocity dispersion (1.2 vs. 4.5 km s-1) for its metallicity. This puts it in line, however, with two other exceptional, very metal-poor GCs: M 15 and NGC 4590. We also find a mild flattening of NGC 4372 in the direction of its rotation. Given its old age, this suggests that the flattening is indeed caused by the systemic rotation rather than tidal interactions with the Galaxy. Additionally, we estimate the dynamical mass of the GC Mdyn = 2.0 ± 0.5 × 105M⊙ based on the dynamical model, which constrains the mass-to-light ratio of NGC 4372 between 1.4 and 2.3 M⊙/L⊙, representative of an old, purely stellar population. Based on

  6. Galactic globular cluster NGC 6752 and its stellar population as inferred from multicolor photometry

    Energy Technology Data Exchange (ETDEWEB)

    Kravtsov, Valery [Instituto de Astronomía, Universidad Católica del Norte, Avenida Angamos 0610, Casilla 1280, Antofagasta (Chile); Alcaíno, Gonzalo [Isaac Newton Institute of Chile, Ministerio de Educación de Chile, Casilla 8-9, Correo 9, Santiago (Chile); Marconi, Gianni; Alvarado, Franklin, E-mail: vkravtsov@ucn.cl, E-mail: inewton@terra.cl, E-mail: falvarad@eso.org, E-mail: gmarconi@eso.org [ESO-European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile)

    2014-03-01

    This paper is devoted to photometric study of the Galactic globular cluster (GGC) NGC 6752 in UBVI, focusing on the multiplicity of its stellar population. We emphasize that our U passband is (1) narrower than the standard one due to its smaller extension blueward and (2) redshifted by ∼300 Å relative to its counterparts, such as the HST F336W filter. Accordingly, both the spectral features encompassed by it and photometric effects of the multiplicity revealed in our study are somewhat different than in recent studies of NGC 6752. Main sequence stars bluer in U – B are less centrally concentrated, as red giants are. We find a statistically significant increasing luminosity of the red giant branch (RGB) bump of ΔU ≈ 0.2 mag toward the cluster outskirts with no so obvious effect in V. The photometric results are correlated with spectroscopic data: the bluer RGB stars in U – B have lower nitrogen abundances. We draw attention to a larger width of the RGB than the blue horizontal branch (BHB) in U – B. This seems to agree with the effects predicted to be caused by molecular bands produced by nitrogen-containing molecules. We find that brighter BHB stars, especially the brightest ones, are more centrally concentrated. This implies that red giants that are redder in U – B, i.e., more nitrogen enriched and centrally concentrated, are the main progenitors of the brighter BHB stars. However, such a progenitor-progeny relationship disagrees with theoretical predictions and with the results on the elemental abundances in horizontal branch stars. We isolated the asymptotic giant branch clump and estimated the parameter ΔV{sub ZAHB}{sup clump} = 0.98 ± 0.12.

  7. Salt-bridge networks within globular and disordered proteins: characterizing trends for designable interactions.

    Science.gov (United States)

    Basu, Sankar; Mukharjee, Debasish

    2017-07-01

    There has been considerable debate about the contribution of salt bridges to the stabilization of protein folds, in spite of their participation in crucial protein functions. Salt bridges appear to contribute to the activity-stability trade-off within proteins by bringing high-entropy charged amino acids into close contacts during the course of their functions. The current study analyzes the modes of association of salt bridges (in terms of networks) within globular proteins and at protein-protein interfaces. While the most common and trivial type of salt bridge is the isolated salt bridge, bifurcated salt bridge appears to be a distinct salt-bridge motif having a special topology and geometry. Bifurcated salt bridges are found ubiquitously in proteins and interprotein complexes. Interesting and attractive examples presenting different modes of interaction are highlighted. Bifurcated salt bridges appear to function as molecular clips that are used to stitch together large surface contours at interacting protein interfaces. The present work also emphasizes the key role of salt-bridge-mediated interactions in the partial folding of proteins containing long stretches of disordered regions. Salt-bridge-mediated interactions seem to be pivotal to the promotion of "disorder-to-order" transitions in small disordered protein fragments and their stabilization upon binding. The results obtained in this work should help to guide efforts to elucidate the modus operandi of these partially disordered proteins, and to conceptualize how these proteins manage to maintain the required amount of disorder even in their bound forms. This work could also potentially facilitate explorations of geometrically specific designable salt bridges through the characterization of composite salt-bridge networks. Graphical abstract ᅟ.

  8. The Globular Cluster NGC 2419: A Crucible for Theories of Gravity

    Science.gov (United States)

    Ibata, R.; Sollima, A.; Nipoti, C.; Bellazzini, M.; Chapman, S. C.; Dalessandro, E.

    2011-09-01

    We present the analysis of a kinematic data set of stars in the globular cluster NGC 2419, taken with the DEep Imaging Multi-Object Spectrograph at the Keck II telescope. Combined with a reanalysis of deep Hubble Space Telescope and Subaru Telescope imaging data, which provide an accurate luminosity profile of the cluster, we investigate the validity of a large set of dynamical models of the system, which are checked for stability via N-body simulations. We find that isotropic models in either Newtonian or Modified Newtonian Dynamics (MOND) are ruled out with extremely high confidence. However, a simple Michie model in Newtonian gravity with anisotropic velocity dispersion provides an excellent representation of the luminosity profile and kinematics of the cluster. The anisotropy profiles of these models ensure an isotropic center to the cluster, which progresses to extreme radial anisotropy toward the outskirts. In contrast, with MOND we find that Michie models that reproduce the luminosity profile either overpredict the velocity dispersion on the outskirts of the cluster if the mass-to-light ratio (M/L) is kept at astrophysically motivated values or else they underpredict the central velocity dispersion if the M/L is taken to be very small. We find that the best Michie model in MOND is a factor of ~104 less likely than the Newtonian model that best fits the system. A likelihood ratio of 350 is found when we investigate more general models by solving the Jeans equation with a Markov Chain Monte Carlo scheme. We verified with N-body simulations that these results are not significantly different when the MOND external field effect is accounted for. If the assumptions that the cluster is in dynamical equilibrium, spherical, not on a peculiar orbit, and possesses a single dynamical tracer population of constant M/L are correct, we conclude that the present observations provide a very severe challenge for MOND. Some of the data presented herein were obtained at the W

  9. Globular clusters as tracers of stellar bimodality in elliptical galaxies: the case of NGC 1399

    Science.gov (United States)

    Forte, Juan C.; Faifer, Favio; Geisler, Doug

    2005-02-01

    Globular cluster systems (GCSs) frequently show a bimodal distribution of cluster integrated colours. This work explores the arguments to support the idea that the same feature is shared by the diffuse stellar population of the galaxy they are associated with. The particular case of NGC 1399, one of the dominant central galaxies in the Fornax cluster, for which a new B surface brightness profile and (B-RKC) colours are presented, is discussed taking advantage of a recently published wide-field study of its GCS. The results show that the galaxy brightness profile and colour gradient, as well as the behaviour of the cumulative globular cluster specific frequency, are compatible with the presence of two dominant stellar populations, associated with the so-called `blue' and `red' globular cluster families. These globular families are characterized by different intrinsic specific frequencies (defined in terms of each stellar population): Sn= 3.3 +/- 0.3 in the case of the red globulars and Sn= 14.3 +/- 2.5 for the blue ones. We stress that this result does not necessarily conflict with recent works that point out a clear difference between the metallicity distribution of (resolved) halo stars and globulars when comparing their number statistics. The region within 0.5arcmin of the centre shows a deviation from the model profile (in both surface brightness and colour) that may be explained in terms of the presence of a bulge-like high-metallicity component. Otherwise, the model gives an excellent fit up to 12arcmin (or 66.5Kpc) from the centre, the galactocentric limit of our blue brightness profile. The inferred specific frequencies imply that, in terms of their associated stellar populations, the formation of the blue globulars took place with an efficiency about six times higher than that corresponding to their red counterparts. The similarity of the spatial distribution of the blue globulars with that inferred for dark matter, as well as with that of the X

  10. Spectroscopic confirmation of the first symbiotic star in a globular cluster

    Science.gov (United States)

    Zurek, David

    2013-10-01

    We have recently discovered an 18-minute period in the ultraviolet of a star in the globular cluster NGC 1851. In the redder optical bands, this star is red and bright, while it shows a clear UV excess relative to other stars at similar positions in the HR diagram. The system is most likely a symbiotic binary, composed of a cool evolved star and a white dwarf, with an 18 minute spin period, accreting the cool star's wind. The binary would be the first such object ever found in a globular cluster, and only the third in the Galaxy where the white dwarf spin period is measured. The only viable alternatives are that the two components are a chance superposition - something with a nontrivial chance of happening in a globular cluster core. In such a case, the 18 minute period would most likely be the spin period of a magnetic white dwarf in an intermediate polar cataclysmic variable {this would be the first confirmed magnetic CV in a globular cluster}, or the orbital period of a double-degenerate AM CVn binary. Each of these three possibilities show unique {and very different} emission line spectra in the blue wavelength range. Two orbits of HST with STIS/G430L will produce a spectrum of sufficient signal-to-noise to distinguish between these 3 scenarios. The result will be an important constraint on N-body models of globular clusters.

  11. Two stellar-mass black holes in the globular cluster M22.

    Science.gov (United States)

    Strader, Jay; Chomiuk, Laura; Maccarone, Thomas J; Miller-Jones, James C A; Seth, Anil C

    2012-10-04

    Hundreds of stellar-mass black holes probably form in a typical globular star cluster, with all but one predicted to be ejected through dynamical interactions. Some observational support for this idea is provided by the lack of X-ray-emitting binary stars comprising one black hole and one other star ('black-hole/X-ray binaries') in Milky Way globular clusters, even though many neutron-star/X-ray binaries are known. Although a few black holes have been seen in globular clusters around other galaxies, the masses of these cannot be determined, and some may be intermediate-mass black holes that form through exotic mechanisms. Here we report the presence of two flat-spectrum radio sources in the Milky Way globular cluster M22, and we argue that these objects are black holes of stellar mass (each ∼10-20 times more massive than the Sun) that are accreting matter. We find a high ratio of radio-to-X-ray flux for these black holes, consistent with the larger predicted masses of black holes in globular clusters compared to those outside. The identification of two black holes in one cluster shows that ejection of black holes is not as efficient as predicted by most models, and we argue that M22 may contain a total population of ∼5-100 black holes. The large core radius of M22 could arise from heating produced by the black holes.

  12. Images in the rocket ultraviolet - UV fluxes of M31 globular clusters

    International Nuclear Information System (INIS)

    Bohlin, R.C.; Cornett, R.H.; Hill, J.K.; Hill, R.S.; Stecher, T.P.

    1988-01-01

    Images obtained by a rocket-borne UV imaging telescope are used here to determine near-UV fluxes for 17 sources in M31 that are optical globular-cluster candidates and for the bright open cluster vdB0 in M31. Far-UV fluxes or flux limits are determined for the same clusters. The m(NUV)-V colors for M31 clusters are similar to those of Galactic clusters, except for the high-metallicity M31 cluster Bo 171. Four of the detected clusters have optical, m(NUV) - V, and m(FUV) - V colors indicating ages of about 100 million years. These four clusters are probably similar to the so-called 'blue globular' clusters of the LMC. The existence of young LMC-type blue globulars and the possible existence of middle-aged metal-rich globulars may indicate that M31 has continued to form globular clusters throughout its life. 39 references

  13. Mass evaporation rate of globular clusters in a strong tidal field

    Science.gov (United States)

    Madrid, Juan P.; Leigh, Nathan W. C.; Hurley, Jarrod R.; Giersz, Mirek

    2017-09-01

    The mass evaporation rate of globular clusters evolving in a strong Galactic tidal field is derived through the analysis of large, multimass N-body simulations. For comparison, we also study the same evaporation rates using mocca Monte Carlo models for globular cluster evolution. Our results show that the mass evaporation rate is a dynamical value, that is, far from a constant single number found in earlier analytical work and commonly used in the literature. Moreover, the evaporation rate derived with these simulations is higher than values previously published. These models also show that the value of the mass evaporation rate depends on the strength of the tidal field. We give an analytical estimate of the mass evaporation rate as a function of time and galactocentric distance ξ(RGC, t). Upon extrapolating this formula to smaller RGC values, our results provide tentative evidence for a very high ξ value at small RGC. Our results suggest that the corresponding mass-loss in the inner Galactic potential could be high and it should be accounted for when star clusters pass within it. This has direct relevance to nuclear cluster formation/growth via the infall of globular clusters through dynamical friction. As an illustrative example, we estimate how the evaporation rate increases for an ˜105 M⊙ globular cluster that decays through dynamical friction into the Galactic Centre. We discuss the findings of this work in relation to the formation of nuclear star clusters by inspiralling globular clusters.

  14. VizieR Online Data Catalog: Revised Bologna Catalog of M31 globular clusters (Galleti+, 2004)

    Science.gov (United States)

    Galleti, S.; Federici, L.; Bellazzini, M.; Fusi Pecci, F.; Macrina, S.

    2003-11-01

    We have identified in the 2MASS database 693 known and candidate globular clusters in M31. The 2MASS J,H,K magnitudes of these objects have been transformed to the same homogeneous photometric system of existing near infrared photometry of M31 globulars, finally yielding J,H,K integrated photometry for 279 confirmed M31 clusters, 406 unconfirmed candidates and 8 objects with controversial classification. Of these objects 529 lacked any previous estimate of their near infrared magnitudes. The newly assembled near infrared dataset has been implemented into a revised version of the Bologna Catalogue of M31 globulars, with updated optical (UBVRI) photometry taken, when possible, from the most recent sources of CCD photometry available in the literature and transformed to a common photometric system. The final Revised Bologna Catalogue (table 2) most comprehensive list presently available of confirmed and candidate M31 globular clusters, with a total of 1164 entries. In particular, it includes 337 confirmed GCs, 688 GC candidates, 10 objects with controversial classification, 70 confirmed galaxies, 55 confirmed stars, and 4 HII regions. Using the newly assembled database we show that the V-K color provides a powerful tool to discriminate between M31 clusters and background galaxies, and we identify a sample of 83 globular cluster candidates, which is not likely to be contaminated by misclassified galaxies. (4 data files).

  15. Human diploid fibroblasts have receptors for the globular domain of C1Q

    International Nuclear Information System (INIS)

    Bordin, S.; Page, R.C.

    1986-01-01

    The authors showed that mass cultures of fibroblasts grown from gingival explants in DB medium with 10% human serum are enriched in a phenotype that binds C1q with an affinity much higher than the rest of the population. Because of potential biologic importance of C1q receptors, the authors studied whether the interaction between C1q and this phenotype was mediated by the globular or collagenous domains of the molecule. Globular fragments were prepared by digesting C1q with collagenase, and collagenous fragments obtained after pepsin treatment. C1q binding on cells in suspension was determined by reaction with 125 I-C1q as reported. Competition experiments were performed under conditions in which intact 125 I-C1q binding saturated all available receptors. The results showed that collagenous fragments inhibited 20% of the 125 I-C1q binding to high affinity receptors, whereas inhibition by globular fragments was 70%. Unlabeled intact C1q and collagen type 1 were used as controls, and inhibited 92% and 17% of C1q binding, respectively. These studies show that C1q interacts with the fibroblast phenotype expressing high affinity receptors through its globular domain. The authors suggest that at sites of trauma, native C1 may bind to the surface of these cells via the globular domain of C1q, and that this unique phenotype may play an important role in tissue repair

  16. An Enigmatic Population of Luminous Globular Clusters in a Galaxy Lacking Dark Matter

    Science.gov (United States)

    van Dokkum, Pieter; Cohen, Yotam; Danieli, Shany; Kruijssen, J. M. Diederik; Romanowsky, Aaron J.; Merritt, Allison; Abraham, Roberto; Brodie, Jean; Conroy, Charlie; Lokhorst, Deborah; Mowla, Lamiya; O’Sullivan, Ewan; Zhang, Jielai

    2018-04-01

    We recently found an ultra diffuse galaxy (UDG) with a half-light radius of R e = 2.2 kpc and little or no dark matter. The total mass of NGC1052–DF2 was measured from the radial velocities of bright compact objects that are associated with the galaxy. Here, we analyze these objects using a combination of Hubble Space Telescope (HST) imaging and Keck spectroscopy. Their average size is =6.2+/- 0.5 pc and their average ellipticity is =0.18+/- 0.02. From a stacked Keck spectrum we derive an age of ≳9 Gyr and a metallicity of [Fe/H] = ‑1.35 ± 0.12. Their properties are similar to ω Centauri, the brightest and largest globular cluster in the Milky Way, and our results demonstrate that the luminosity function of metal-poor globular clusters is not universal. The fraction of the total stellar mass that is in the globular cluster system is similar to that in other UDGs, and consistent with “failed galaxy” scenarios, where star formation terminated shortly after the clusters were formed. However, the galaxy is a factor of ∼1000 removed from the relation between globular cluster mass and total galaxy mass that has been found for other galaxies, including other UDGs. We infer that a dark matter halo is not a prerequisite for the formation of metal-poor globular cluster-like objects in high-redshift galaxies.

  17. The DRAGON simulations: globular cluster evolution with a million stars

    Science.gov (United States)

    Wang, Long; Spurzem, Rainer; Aarseth, Sverre; Giersz, Mirek; Askar, Abbas; Berczik, Peter; Naab, Thorsten; Schadow, Riko; Kouwenhoven, M. B. N.

    2016-05-01

    Introducing the DRAGON simulation project, we present direct N-body simulations of four massive globular clusters (GCs) with 106 stars and 5 per cent primordial binaries at a high level of accuracy and realism. The GC evolution is computed with NBODY6++GPU and follows the dynamical and stellar evolution of individual stars and binaries, kicks of neutron stars and black holes (BHs), and the effect of a tidal field. We investigate the evolution of the luminous (stellar) and dark (faint stars and stellar remnants) GC components and create mock observations of the simulations (I.e. photometry, colour-magnitude diagrams, surface brightness and velocity dispersion profiles). By connecting internal processes to observable features, we highlight the formation of a long-lived `dark' nuclear subsystem made of BHs, which results in a two-component structure. The inner core is dominated by the BH subsystem and experiences a core-collapse phase within the first Gyr. It can be detected in the stellar (luminous) line-of-sight velocity dispersion profiles. The outer extended core - commonly observed in the (luminous) surface brightness profiles - shows no collapse features and is continuously expanding. We demonstrate how a King model fit to observed clusters might help identify the presence of post core-collapse BH subsystems. For global observables like core and half-mass radii, the direct simulations agree well with Monte Carlo models. Variations in the initial mass function can result in significantly different GC properties (e.g. density distributions) driven by varying amounts of early mass-loss and the number of forming BHs.

  18. The nature of folded states of globular proteins.

    Science.gov (United States)

    Honeycutt, J D; Thirumalai, D

    1992-06-01

    We suggest, using dynamical simulations of a simple heteropolymer modelling the alpha-carbon sequence in a protein, that generically the folded states of globular proteins correspond to statistically well-defined metastable states. This hypothesis, called the metastability hypothesis, states that there are several free energy minima separated by barriers of various heights such that the folded conformations of a polypeptide chain in each of the minima have similar structural characteristics but have different energies from one another. The calculated structural characteristics, such as bond angle and dihedral angle distribution functions, are assumed to arise from only those configurations belonging to a given minimum. The validity of this hypothesis is illustrated by simulations of a continuum model of a heteropolymer whose low temperature state is a well-defined beta-barrel structure. The simulations were done using a molecular dynamics algorithm (referred to as the "noisy" molecular dynamics method) containing both friction and noise terms. It is shown that for this model there are several distinct metastable minima in which the structural features are similar. Several new methods of analyzing fluctuations in structures belonging to two distinct minima are introduced. The most notable one is a dynamic measure of compactness that can in principle provide the time required for maximal compactness to be achieved. The analysis shows that for a given metastable state in which the protein has a well-defined folded structure the transition to a state of higher compactness occurs very slowly, lending credence to the notion that the system encounters a late barrier in the process of folding to the most compact structure. The examination of the fluctuations in the structures near the unfolding----folding transition temperature indicates that the transition state for the unfolding to folding process occurs closer to the folded state.

  19. GLOBULAR CLUSTERS INDICATE THAT ULTRA-DIFFUSE GALAXIES ARE DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Beasley, Michael A.; Trujillo, Ignacio, E-mail: beasley@iac.es [Instituto de Astrofisica de Canarias, Calle Via Láctea, La Laguna, Tenerife (Spain)

    2016-10-10

    We present an analysis of archival HST /ACS imaging in the F475W ( g {sub 475}), F606W ( V {sub 606}), and F814W ( I {sub 814}) bands of the globular cluster (GC) system of a large (3.4 kpc effective radius) ultra-diffuse galaxy (DF17) believed to be located in the Coma Cluster of galaxies. We detect 11 GCs down to the 5 σ completeness limit of the imaging ( I {sub 814} = 27 mag). Correcting for background and our detection limits yields a total population of GCs in this galaxy of 27 ± 5 and a V -band specific frequency S {sub N} = 28 ± 5. Based on comparisons to the GC systems of local galaxies, we show that both the absolute number and the colors of the GC system of DF17 are consistent with the GC system of a dark-matter-dominated dwarf galaxy with virial mass ∼9.0 × 10{sup 10} M {sub ⊙} and a dark-to-stellar mass ratio M {sub vir}/ M {sub star} ∼ 1000. Based on the stellar mass growth of the Milky Way, we show that DF17 cannot be understood as a failed Milky-Way-like system, but is more similar to quenched Large-Magellanic-Cloud-like systems. We find that the mean color of the GC population, g {sub 475}– I {sub 814} = 0.91 ± 0.05 mag, coincides with the peak of the color distribution of intracluster GCs and is also similar to those of the blue GCs in the outer regions of massive galaxies. We suggest that both the intracluster GC population in Coma and the blue peak in the GC populations of massive galaxies may be fed—at least in part—by the disrupted equivalents of systems such as DF17.

  20. The Globular Cluster System of the Spiral Galaxy NGC 7814

    Science.gov (United States)

    Rhode, Katherine L.; Zepf, Stephen E.

    2003-11-01

    We present the results of a wide-field photometric study of the globular cluster (GC) system of the edge-on Sab spiral NGC 7814. This is the first spiral to be fully analyzed from our survey of the GC systems of a large sample of galaxies beyond the Local Group. NGC 7814 is of particular interest because a previous study estimated that it has 500-1000 GCs, giving it the largest specific frequency (SN) known for a spiral. Understanding this galaxy's GC system is important in terms of our understanding of the GC populations of spirals in general and has implications for the formation of massive galaxies. We observed the galaxy in BVR filters with the WIYN 3.5 m telescope and used image classification and three-color photometry to select GC candidates. We also analyzed archival Hubble Space Telescope (HST) Wide Field Planetary Camera 2 images of NGC 7814, both to help quantify the contamination level of the WIYN GC candidate list and to detect GCs in the inner part of the galaxy halo. Combining HST data with high-quality ground-based images allows us to trace the entire radial extent of this galaxy's GC system and determine the total number of GCs directly through observation. We find that rather than being an especially high-SN spiral, NGC 7814 has <~200 GCs and SN~1, making it comparable to the two most well-studied spiral galaxies, the Milky Way and M31. We explore the implications of these results for models of the formation of galaxies and their GC systems. The initial results from our survey suggest that the GC systems of typical elliptical galaxies can be accounted for by the merger of two or more spirals, but that for highly luminous elliptical galaxies, additional physical processes may be needed.

  1. The Globular Cluster NGC 6402 (M14). II. Variable Stars

    Science.gov (United States)

    Contreras Peña, C.; Catelan, M.; Grundahl, F.; Stephens, A. W.; Smith, H. A.

    2018-03-01

    We present time-series BVI photometry for the Galactic globular cluster NGC 6402 (M14). The data consist of ∼137 images per filter, obtained using the 0.9 and 1.0 m SMARTS telescopes at the Cerro Tololo Inter-American Observatory. The images were obtained during two observing runs in 2006–2007. The image-subtraction package ISIS, along with DAOPHOT II/ALLFRAME, was used to perform crowded-field photometry and search for variable stars. We identified 130 variables, eight of which are new discoveries. The variable star population is comprised of 56 ab-type RR Lyrae stars, 54 c-type RR Lyrae, 6 type II Cepheids, 1 W UMa star, 1 detached eclipsing binary, and 12 long-period variables. We provide Fourier decomposition parameters for the RR Lyrae, and discuss the physical parameters and photometric metallicity derived therefrom. The M14 distance modulus is also discussed, based on different approaches for the calibration of the absolute magnitudes of RR Lyrae stars. The possible presence of second-overtone RR Lyrae in M14 is critically addressed, with our results arguing against this possibility. By considering all of the RR Lyrae stars as members of the cluster, we derive =0.589 {{d}}{{a}}{{y}}{{s}}. This, together with the position of the RR Lyrae stars of both Bailey types in the period–amplitude diagram, suggests an Oosterhoff-intermediate classification for the cluster. Such an intermediate Oosterhoff type is much more commonly found in nearby extragalactic systems, and we critically discuss several other possible indications that may point to an extragalactic origin for this cluster. Based on observations obtained with the 0.9 m and 1 m telescopes at the Cerro Tololo Inter-American Observatory, Chile, operated by the SMARTS consortium.

  2. Globular Clusters Indicate That Ultra-diffuse Galaxies Are Dwarfs

    Science.gov (United States)

    Beasley, Michael A.; Trujillo, Ignacio

    2016-10-01

    We present an analysis of archival HST/ACS imaging in the F475W (g 475), F606W (V 606), and F814W (I 814) bands of the globular cluster (GC) system of a large (3.4 kpc effective radius) ultra-diffuse galaxy (DF17) believed to be located in the Coma Cluster of galaxies. We detect 11 GCs down to the 5σ completeness limit of the imaging (I 814 = 27 mag). Correcting for background and our detection limits yields a total population of GCs in this galaxy of 27 ± 5 and a V-band specific frequency S N = 28 ± 5. Based on comparisons to the GC systems of local galaxies, we show that both the absolute number and the colors of the GC system of DF17 are consistent with the GC system of a dark-matter-dominated dwarf galaxy with virial mass ˜9.0 × 1010 M ⊙ and a dark-to-stellar mass ratio M vir/M star ˜ 1000. Based on the stellar mass growth of the Milky Way, we show that DF17 cannot be understood as a failed Milky-Way-like system, but is more similar to quenched Large-Magellanic-Cloud-like systems. We find that the mean color of the GC population, g 475-I 814 = 0.91 ± 0.05 mag, coincides with the peak of the color distribution of intracluster GCs and is also similar to those of the blue GCs in the outer regions of massive galaxies. We suggest that both the intracluster GC population in Coma and the blue peak in the GC populations of massive galaxies may be fed—at least in part—by the disrupted equivalents of systems such as DF17.

  3. The ellipticities of a sample of globular clusters in M31

    International Nuclear Information System (INIS)

    Lupton, R.H.

    1989-01-01

    Images for a sample of 18 globular clusters in M31 have been obtained. The mean ellipticity on the sky in the range 7-14 pc (2-4 arcsec) is 0.08 + or - 0.02 and 0.12 + or - 0.01 in the range 14-21 pc (4-6 arcsec), with corresponding true ellipticities of 0.12 and 0.18. The difference between the inner and outer parts is significant at a 99 percent level. The flattening of the inner parts is statistically indistinguishable from that of the Galactic globular clusters, while the outer parts are flatter than the Galactic clusters at a 99.8 percent confidence level. There is a significant anticorrelation of ellipticity with line strength; such a correlation may in retrospect also be seen in the Galactic globular cluster system. For the M31 data, this anticorrelation is stronger in the inner parts of the galaxy. 30 refs

  4. NO EVIDENCE FOR INTERMEDIATE-MASS BLACK HOLES IN GLOBULAR CLUSTERS: STRONG CONSTRAINTS FROM THE JVLA

    International Nuclear Information System (INIS)

    Strader, Jay; Chomiuk, Laura; Maccarone, Thomas J.; Miller-Jones, James C. A.; Seth, Anil C.; Heinke, Craig O.; Sivakoff, Gregory R.

    2012-01-01

    With a goal of searching for accreting intermediate-mass black holes (IMBHs), we report the results of ultra-deep Jansky Very Large Array radio continuum observations of the cores of three Galactic globular clusters: M15, M19, and M22. We reach rms noise levels of 1.5-2.1 μJy beam –1 at an average frequency of 6 GHz. No sources are observed at the center of any of the clusters. For a conservative set of assumptions about the properties of the accretion, we set 3σ upper limits on IMBHs from 360 to 980 M ☉ . These limits are among the most stringent obtained for any globular cluster. They add to a growing body of work that suggests either (1) IMBHs ∼> 1000 M ☉ are rare in globular clusters or (2) when present, IMBHs accrete in an extraordinarily inefficient manner.

  5. No Evidence for Intermediate-mass Black Holes in Globular Clusters: Strong Constraints from the JVLA

    Science.gov (United States)

    Strader, Jay; Chomiuk, Laura; Maccarone, Thomas J.; Miller-Jones, James C. A.; Seth, Anil C.; Heinke, Craig O.; Sivakoff, Gregory R.

    2012-05-01

    With a goal of searching for accreting intermediate-mass black holes (IMBHs), we report the results of ultra-deep Jansky Very Large Array radio continuum observations of the cores of three Galactic globular clusters: M15, M19, and M22. We reach rms noise levels of 1.5-2.1 μJy beam-1 at an average frequency of 6 GHz. No sources are observed at the center of any of the clusters. For a conservative set of assumptions about the properties of the accretion, we set 3σ upper limits on IMBHs from 360 to 980 M ⊙. These limits are among the most stringent obtained for any globular cluster. They add to a growing body of work that suggests either (1) IMBHs >~ 1000 M ⊙ are rare in globular clusters or (2) when present, IMBHs accrete in an extraordinarily inefficient manner.

  6. RR Lyrae in LMC Globular Clusters: Insights into the Oosterhoff Phenomenon and Milky Way Formation

    Science.gov (United States)

    Kuehn, Charles A., III; Smith, H. A.; Catelan, M.; Taylor, L.; McClellan, R. E.; Looper, K.; DeLee, N.; Pritzl, B. J.

    2011-01-01

    We present results from a study of RR Lyrae stars in five globular clusters located in the Large Magellanic Cloud. The goal of this study was to look at the behavior and properties of RR Lyrae stars in Oosterhoff-intermediate globular clusters and compare them to RR Lyrae in Oosterhoff I and II clusters. New BVI photometric observations of these clusters were obtained with the SMARTS consortium telescopes and with the SOAR 4-meter telescope. We present light curves and Fourier properties for the RR Lyrae stars in our study as well as physical properties for these stars derived from their Fourier parameters. We compare these physical properties to those of RR Lyrae in Milky Way halo globular clusters and discuss implications for Milky Way halo formation.

  7. A NEW DISTANT MILKY WAY GLOBULAR CLUSTER IN THE PAN-STARRS1 3π SURVEY

    International Nuclear Information System (INIS)

    Laevens, Benjamin P. M.; Martin, Nicolas F.; Sesar, Branimir; Rix, Hans-Walter; Schlafly, Edward F.; Bernard, Edouard J.; Ferguson, Annette M. N.; Slater, Colin T.; Bell, Eric F.; Burgett, William S.; Chambers, Kenneth C.; Denneau, Larry; Kaiser, Nicholas; Kudritzki, Rolf-Peter; Magnier, Eugene A.; Morgan, Jeffrey S.; Sweeney, William E.; Draper, Peter W.; Metcalfe, Nigel; Price, Paul A.

    2014-01-01

    We present a new satellite in the outer halo of the Galaxy, the first Milky Way satellite found in the stacked photometric catalog of the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1) Survey. From follow-up photometry obtained with WFI on the MPG/ESO 2.2 m telescope, we argue that the object, located at a heliocentric distance of 145 ± 17 kpc, is the most distant Milky Way globular cluster yet known. With a total magnitude of M V = –4.3 ± 0.2 and a half-light radius of 20 ± 2 pc, it shares the properties of extended globular clusters found in the outer halo of our Galaxy and the Andromeda galaxy. The discovery of this distant cluster shows that the full spatial extent of the Milky Way globular cluster system has not yet been fully explored

  8. GLOBULAR RESISTANCE MODIFICATION ON RATS CONSECUTIVELY TO Al2(SO43 ADDITION FOR TWO GENERATION

    Directory of Open Access Journals (Sweden)

    LOREDANA GABRIELA STANA

    2007-05-01

    Full Text Available Some of the major modifications on membranes produced by the oxygen reactivespecies are membranal structure and functions modifications, lipids peroxydation,membranal protein alterations and transportation disturbances thru membranes. Aseries of xenobotics like oxidant pollutants, lead, aluminium and others directly orindirectly are producing thru metabolization free radicals which interact with cellscomponents and alterate their functions. The purpose of this paper was to relieve theimpact of aluminium cumulative addition onto globular resistance on rats. Has beenadministrated three levels of aluminium (200ppb, 400 ppb şi 1000 ppb as Al2(SO43ad libidum in water. Was followed their toxicity impact on the globular resistancefor two generations. The results indicate a decrease of globular resistance directlycorrelated with the aluminium addition.

  9. The Luminosity Functions of Old and Intermediate-Age Globular Clusters in NGC 3610

    OpenAIRE

    Whitmore, B. C.; Schweizer, F.; Kundu, A.; Miller, B. W.

    2002-01-01

    The WFPC2 Camera on board HST has been used to obtain high-resolution images of NGC 3610, a dynamically young elliptical galaxy. These observations supersede shorter, undithered HST observations where an intermediate-age population of globular clusters was first discovered. The new observations show the bimodal color distribution of globular clusters more clearly, with peaks at (V-I)o = 0.95 and 1.17. The luminosity function (LF) of the blue, metal-poor population of clusters in NGC 3610 turn...

  10. Keck Spectroscopy of Globular Clusters in the Elliptical Galaxy NGC 3610

    OpenAIRE

    Strader, Jay; Brodie, Jean P.; Schweizer, Francois; Larsen, Soeren S.; Seitzer, Patrick

    2002-01-01

    We present moderate-resolution Keck spectra of nine candidate globular clusters in the possible merger-remnant elliptical galaxy NGC 3610. Eight of the objects appear to be bona fide globular clusters of NGC 3610. We find that two of the clusters belong to an old metal-poor population, five to an old metal-rich population, and only one to an intermediate-age metal-rich population. The estimated age of the intermediate-age cluster is 1-5 Gyr, which is in agreement with earlier estimates of the...

  11. A Search for Millisecond Pulsars in Fermi LAT-Detected Globular Clusters

    OpenAIRE

    DeCesar, Megan E.; Ransom, Scott M.; Ray, Paul S.

    2011-01-01

    We have searched for millisecond pulsars (MSPs) in two globular clusters detected by the Fermi Large Area Telescope. These clusters contained no known MSPs prior to their detections in gamma rays. The discovery of gamma ray emission from many MSPs and the prevalence of MSPs in globular clusters points to a population of MSPs as the likely source of the detected GeV emission, directing our search for new cluster MSPs. We observed NGC 6652 and NGC 6388 at 2 GHz with the Green Bank Ultimate Puls...

  12. Integrated-light Two Micron All Sky Survey infrared photometry of Galactic globular clusters

    OpenAIRE

    Cohen, Judith G.; Hsieh, Scott; Metchev, Stanimir; Djorgovski, S. G.; Malkan, M.

    2007-01-01

    We have mosaicked Two Micron All Sky Survey (2MASS) images to derive surface brightness profiles in J, H, and K_s for 104 Galactic globular clusters. We fit these with King profiles and show that the core radii are identical to within the errors for each of these IR colors and are identical to the core radii at V in essentially all cases. We derive integrated-light colors V-J, V-H, V-K_s, J-H, and J-Ks for these globular clusters. Each color shows a reasonably tight relation between the dered...

  13. Analysis of extreme events

    CSIR Research Space (South Africa)

    Khuluse, S

    2009-04-01

    Full Text Available the stability of the parameter estimates. 9 / 27 Background Overview of the Theory of Extremes Case Studies Concluding Remarks Analysis of Extreme Rainfall Events Analysis of Extreme Wave Heights Figure: Map of South Africa with the study areas... highlighted 10 / 27 Background Overview of the Theory of Extremes Case Studies Concluding Remarks Analysis of Extreme Rainfall Events Analysis of Extreme Wave Heights Western Cape Climatologically diverse: Influence of the varied topography and it’s...

  14. Galactic evolution of sulphur as traced by globular clusters

    Science.gov (United States)

    Kacharov, N.; Koch, A.; Caffau, E.; Sbordone, L.

    2015-05-01

    Context. Sulphur is an important volatile α element, but its role in the Galactic chemical evolution is still uncertain, and more observations constraining the sulphur abundance in stellar photospheres are required. Aims: We derive the sulphur abundances in red giant branch (RGB) stars in three Galactic halo globular clusters (GC) that cover a wide metallicity range (-2.3 noise (S/N ~ 200 per px) spectra in the region of the S I multiplet 3 at 1045 nm for 15 GC stars selected from the literature (six stars in M 4,six stars in M 22, and three stars in M 30). Multiplet 3 is better suited for S abundance derivation than the more commonly used lines of multiplet 1 at 920 nm, since its lines are not blended by telluric absorption or other stellar features at low metallicity. Results: We used spectral synthesis to derive the [S/Fe] ratio of the stars assuming local thermodynamic equilibrium (LTE). We find mean [S/Fe]LTE = 0.58 ± 0.01 ± 0.20 dex (statistical and systematic error) for M 4, [S/Fe]LTE = 0.57 ± 0.01 ± 0.19 dex for M 22, and [S/Fe]LTE = 0.55 ± 0.02 ± 0.16 dex for M 30. The negative NLTE corrections are estimated to be in the order of the systematic uncertainties. We do not detect star-to-star variations of the S abundance in any of the observed GCs, with the possible exception of two individual stars, one in M 22 and one in M 30, which appear to be highly enriched in S. Conclusions: With the tentative exception of two stars with measured high S abundances, we conclude that sulphur behaves like a typical α element in the studied Galactic GCs, showing enhanced abundances with respect to the solar value at metallicities below [Fe/H]-1.0 dex without a considerable spread. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programmes ID 091.B-0171(A).The reduced spectra and the best fit synthetic models are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc

  15. Globular adiponectin enhances invasion in human breast cancer cells

    Science.gov (United States)

    FALK LIBBY, EMILY; LIU, JIANZHONG; LI, YI; LEWIS, MONICA J.; DEMARK-WAHNEFRIED, WENDY; HURST, DOUGLAS R.

    2016-01-01

    Every year, a large number of women succumb to metastatic breast cancer due to a lack of curative approaches for this disease. Adiponectin (AdipoQ) is the most abundant of the adipocyte-secreted adipokines. In recent years, there has been an interest in the use of AdipoQ and AdipoQ receptor agonists as therapeutic agents for the treatment of breast cancer. However, while multiple epidemiological studies have previously indicated that low levels of circulating plasma AdipoQ portend poor prognosis in patients with breast cancer, recent studies have reported that elevated expression levels of AdipoQ in breast tissue are correlated with advanced stages of the disease. Thus, the aim of the present study was to clarify the mechanism by which AdipoQ in breast tissue acts directly on tumor cells to regulate the early steps of breast cancer metastasis. In the present study, the effects of different AdipoQ isoforms on the metastatic potential of human breast cancer cells were investigated. The results revealed that globular adiponectin (gAd) promoted invasive cell morphology and significantly increased the migration and invasion abilities of breast cancer cells, whereas full-length adiponectin (fAd) had no effect on these cells. Additionally, gAd, but not fAd, increased the expression levels of microtubule-associated protein 1 light chain 3 beta (LC3B)-II and intracellular LC3B puncta, which are indicators of autophagosome formation, thus suggesting autophagic induction by gAd. Furthermore, the inhibition of autophagic function by autophagy-related protein 7 knockdown attenuated the gAd-induced increase in invasiveness in breast cancer cells. Therefore, the results of the present study suggested that a specific AdipoQ isoform may enhance breast cancer invasion, possibly via autophagic induction. Understanding the roles of the different AdipoQ isoforms as microenvironmental regulatory molecules may aid the development of effective AdipoQ-based treatments for breast cancer

  16. The onset of gravothermal oscillations in globular cluster evolution

    Science.gov (United States)

    Breeden, Joseph L.; Cohn, Haldan N.; Hut, Piet

    1994-01-01

    We have carried out an extensive set of Fokker-Planck simulations of the evolution of globular clusters on very long timescales, up to 600 times the initial core collapse time tcc. We consider an idealized equal mass star cluster, with a wide range of values for the total number of stars, 7000 less than N less than 2 x 106. Our models include the heating effect of compact binaries formed in three-body encounters, which halts the initial core collapse and drives a core reexpansion. Postcollapse gravothermal oscillations of the cluster core are found to occur for all N approximately greater than or equal to 8000. For 8000 approximately less than or equal to N approximately less than or equal to 11,000, the oscillation has a simple, regular waveform with a single, well-defined period. For N approximately equals 12,000, the oscillations become nonlinear in a process resembling a period doubling. For N approximately greater than or equal to 14,000, the waveform of the oscillations becomes increasingly more irregular with increasing N, resembling chaotic behavior for N approximately greater than or equal to 15,000. During the oscillations, the core radius and core mass vary dramatically: by more than a factor of 10 for N greater than 15,000, by more than a factor of 100 for N greater than 5 x 104, and by more than a factor of 1000 for N greater than 5 x 105. However, even during the times of maximum expansion, the core contains only a small fraction of the cluster mass. For most N values, the maximum core mass at any time after core collapse is less than 1% of the cluster mass. The exceptions lie in the range 5 x 104 approximately less than or equal to N approximately equal to or less than 2 x 105, where the maximum post-collapse core mass reaches approximately 2% of the cluster mass. We discuss the observational implications of these predictions.

  17. Surface Compositions of Red Giant Stars in Globular Clusters

    Science.gov (United States)

    Cheng, Eric; Lau, Marie; Smith, Graeme; Chen, Brian

    2018-01-01

    Globular clusters (GCs) are excellent “laboratories” to study the formation and evolution of our galaxy. In order to understand, more specifically, the chemical compositions and stellar evolution of the stars in GCs, we ask whether or not deep internal mixing occurs in red giants or if in fact the compositions come from the primordial interstellar medium or previous generations of stars. It has been discovered that as a star evolves up the red giant branch, the surface carbon abundance decreases, which is evidence of deep internal mixing. We questioned whether these processes also affect O or Na abundance as a star evolves. We collected measurement data of red giants from GCs out of academic journals and sorted the data into catalogs. Then, we plotted the catalogs into figures, comparing surface O and Na each with stellar luminosity. Statistical tests were ran to quantify the amount of correlation between the variables. Out of 27 GCs, we concluded that eight show a positive correlation between Na and luminosity, and two show a negative correlation between O and luminosity. Properties of GCs were compared to determine if chemical distribution in stars depends on GCs as the self-enrichment scenario suggests. We created histograms of sodium distribution to test for bimodality to examine if there are separate trends in each GC. In six GCs, two different sequences of red giants appear for Na versus luminosity, suggesting evidence that the depth of mixing may differ among each red giant in a GC. This study has provided new evidence that the changing chemical abundances on the surfaces of red giants can be due to stellar evolutionary effects and deep internal mixing, which may not necessarily depend on the GC and may differ in depth among each red giant. Through this study, we learn more about stellar evolution which will eventually help us understand the origins of our universe. Most of this work was carried out by high school students working under the auspices of

  18. A globular cluster toward M87 with a radial velocity < – 1000 km s{sup –1}: the first hypervelocity cluster

    Energy Technology Data Exchange (ETDEWEB)

    Caldwell, Nelson [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Strader, Jay [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Romanowsky, Aaron J. [Department of Physics and Astronomy, San José State University, San Jose, CA 95192 (United States); Brodie, Jean P. [University of California Observatories, Santa Cruz, CA 95064 (United States); Moore, Ben; Diemand, Jurg [Institute for Theoretical Physics, University of Zurich, CH-8057 Zurich (Switzerland); Martizzi, Davide, E-mail: caldwell@cfa.harvard.edu [Department of Astronomy, University of California, Berkeley, CA 94720 (United States)

    2014-05-20

    We report the discovery of an object near M87 in the Virgo Cluster with an extraordinary blueshift of –1025 km s{sup –1}, offset from the systemic velocity by >2300 km s{sup –1}. Evaluation of photometric and spectroscopic data provides strong evidence that this object is a distant massive globular cluster, which we call HVGC-1 in analogy to Galactic hypervelocity stars. We consider but disfavor more exotic interpretations, such as a system of stars bound to a recoiling black hole. The odds of observing an outlier as extreme as HVGC-1 in a virialized distribution of intracluster objects are small; it appears more likely that the cluster was (or is being) ejected from Virgo following a three-body interaction. The nature of the interaction is unclear, and could involve either a subhalo or a binary supermassive black hole at the center of M87.

  19. BtcA, A class IA type III chaperone, interacts with the BteA N-terminal domain through a globular/non-globular mechanism.

    Directory of Open Access Journals (Sweden)

    Chen Guttman

    Full Text Available Bordetella pertussis, the etiological agent of "whooping cough" disease, utilizes the type III secretion system (T3SS to deliver a 69 kDa cytotoxic effector protein, BteA, directly into the host cells. As with other T3SS effectors, prior to its secretion BteA binds BtcA, a 13.9 kDa protein predicted to act as a T3SS class IA chaperone. While this interaction had been characterized for such effector-chaperone pairs in other pathogens, it has yet to be fully investigated in Bordetella. Here we provide the first biochemical proof that BtcA is indeed a class IA chaperone, responsible for the binding of BteA's N-terminal domain. We bring forth extensive evidence that BtcA binds its substrate effector through a dual-interface binding mechanism comprising of non-globular and bi-globular interactions at a moderate micromolar level binding affinity. We demonstrate that the non-globular interactions involve the first 31 N-terminal residues of BteA287 and their removal leads to destabilization of the effector-chaperone complex and lower binding affinities to BtcA. These findings represent an important first step towards a molecular understanding of BteA secretion and cell entry.

  20. EVIDENCE OF AGB POLLUTION IN GALACTIC GLOBULAR CLUSTERS FROM THE Mg–Al ANTICORRELATIONS OBSERVED BY THE APOGEE SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Ventura, P.; Dell’Agli, F.; D’Antona, F.; Di Criscienzo, M.; Tailo, M. [INAF–Osservatorio Astronomico di Roma, via Frascati 33, I-00077 Monteporzio (Italy); García-Hernández, D. A.; Zamora, O. [Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, Tenerife (Spain); Mészáros, Sz. [ELTE Gothard Astrophysical Observatory, H-9704 Szombat-hely, Szent Imre Herceg st. 112 (Hungary); Lucatello, S. [INAF–Osservatorio Astronomico di Padova, vicolo dell’Osservatorio 5, I-35122 Padova (Italy); Shetrone, M. [University of Texas at Austin, McDonald Observatory, Austin, TX (United States); Tang, Baitian [Departamento de Astronomía, Casilla, 160-C, Universidad de Concepción, Concepción (Chile)

    2016-11-10

    We study the formation of multiple populations in globular clusters (GCs), under the hypothesis that stars in the second generation formed from the winds of intermediate-mass stars, ejected during the asymptotic giant branch (AGB) phase, possibly diluted with pristine gas, sharing the same chemical composition of first-generation stars. To this aim, we use the recent Apache Point Observatory Galactic Evolution Experiment (APOGEE) data, which provide the surface chemistry of a large sample of giant stars, belonging to clusters that span a wide metallicity range. The APOGEE data set is particularly suitable to discriminate among the various pollution scenarios proposed so far, as it provides the surface abundances of Mg and Al, the two elements involved in a nuclear channel extremely sensitive to the temperature, hence to the metallicity of the polluters. The present analysis shows a remarkable agreement between the observations and the theoretical yields from massive AGB stars. In particular, the observed extension of the depletion of Mg and O and the increase in Al is well reproduced by the models and the trend with the metallicity is also fully accounted for. This study further supports the idea that AGB stars were the key players in the pollution of the intra-cluster medium, from which additional generations of stars formed in GCs.

  1. The Next Generation Virgo Cluster Survey (NGVS). XXVI. The Issues of Photometric Age and Metallicity Estimates for Globular Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Powalka, Mathieu; Lançon, Ariane; Duc, Pierre-Alain [Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l’Université, F-67000 Strasbourg (France); Puzia, Thomas H.; Muñoz, Roberto P.; Zhang, Hongxin [Institute of Astrophysics, Pontificia Universidad Católica de Chile, 7820436 Macul, Santiago (Chile); Peng, Eric W. [Department of Astronomy, Peking University, Beijing 100871 (China); Liu, Chengze [Center for Astronomy and Astrophysics, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Blakeslee, John P.; Côté, Patrick; Ferrarese, Laura; Roediger, Joel; Gwyn, S. D. J. [National Research Council of Canada, Herzberg Astronomy and Astrophysics Program, Victoria, BC V9E 2E7 (Canada); Sánchez-Janssen, Rúben [UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Durrell, Patrick R. [Department of Physics and Astronomy, Youngstown State University, Youngstown, OH (United States); Cuillandre, Jean-Charles [AIM Paris Saclay, CNRS/INSU, CEA/Irfu,Université Paris Diderot, Orme des Merisiers, F-91191 Gif sur Yvette cedex (France); Guhathakurta, Puragra [UCO/Lick Observatory, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Hudelot, Patrick, E-mail: mathieu.powalka@astro.unistra.fr [Institut d’Astrophysique de Paris, UMR 7095 CNRS and UPMC, 98bis Bd Arago, F-75014 Paris (France); and others

    2017-08-01

    Large samples of globular clusters (GC) with precise multi-wavelength photometry are becoming increasingly available and can be used to constrain the formation history of galaxies. We present the results of an analysis of Milky Way (MW) and Virgo core GCs based on 5 optical-near-infrared colors and 10 synthetic stellar population models. For the MW GCs, the models tend to agree on photometric ages and metallicities, with values similar to those obtained with previous studies. When used with Virgo core GCs, for which photometry is provided by the Next Generation Virgo cluster Survey (NGVS), the same models generically return younger ages. This is a consequence of the systematic differences observed between the locus occupied by Virgo core GCs and models in panchromatic color space. Only extreme fine-tuning of the adjustable parameters available to us can make the majority of the best-fit ages old. Although we cannot exclude that the formation history of the Virgo core may lead to more conspicuous populations of relatively young GCs than in other environments, we emphasize that the intrinsic properties of the Virgo GCs are likely to differ systematically from those assumed in the models. Thus, the large wavelength coverage and photometric quality of modern GC samples, such as those used here, is not by itself sufficient to better constrain the GC formation histories. Models matching the environment-dependent characteristics of GCs in multi-dimensional color space are needed to improve the situation.

  2. Using Blue Stragglers to Predict Retained Black Hole Population in Globular Clusters

    Science.gov (United States)

    Hermanek, Keith; Chatterjee, Sourav; Rasio, Frederic

    2018-01-01

    Large numbers of black holes (BHs) are expected to form in massive star clusters typical of the globular clusters (GCs). Sophisticated theoretical models suggest that many of these BHs can be retained in present-day GCs. Observations have also identified several BH candidates in Galactic and extragalactic GCs (e.g., Macarone et al. 2007; Irwin et al. 2010; Strader et al. 2012; Chomiuk et al. 2013; Miller-Jones et al. 2014). It has also been shown that high-mass and high-density clusters such as GCs are efficient factories of merging binary BHs similar to those observed by the LIGO observatories (Abbott et al. 2016a,b,c,d,e; Rodriguez et al. 2016). Understanding the formation rate and properties of binary BHs are dependent on a detailed understanding of how the BHs dynamically evolve within GCs. Nevertheless, directly detecting BHs in GCs is extremely challenging; BHs only in binaries with limited configurations can be directly detected by the detection of gravitational wave, X-ray, or radio emissions. We propose an indirect of inferring the number of undetected retained BHs in a GC by investigating the dynamical effects of a large number of BHs on the production of other tracer populations such as Blue Straggler Stars (BSS). Using a large grid of detailed GC models we show that there is a clear anti-correlation between the number of BSS in a cluster and the number of retained BHs. Being the most massive species, large numbers of retained BHs will dominate the core of the cluster as a result of mass-segregation driving away other low-mass species such as main-sequence stars from central high-density regions. BSS are expected to form from physical collisions between main-sequence (MS) stars mediated by binary encounters (e.g., Chatterjee et al. 2013) in cores of GCs. Production of BSS by collisions or mass transfer channels are suppressed if a large number of retained BHs in a cluster restrict the number of MS stars in the core. Extensive observational data exist on

  3. Star Counts in the Globular Cluster ω Centauri. I. Bright Stellar Components

    Science.gov (United States)

    Castellani, V.; Calamida, A.; Bono, G.; Stetson, P. B.; Freyhammer, L. M.; Degl'Innocenti, S.; Moroni, P. Prada; Monelli, M.; Corsi, C. E.; Nonino, M.; Buonanno, R.; Caputo, F.; Castellani, M.; Dall'Ora, M.; Del Principe, M.; Ferraro, I.; Iannicola, G.; Piersimoni, A. M.; Pulone, L.; Vuerli, C.

    2007-07-01

    We present a photometric investigation on HB, RGB, and MSTO stars in ω Cen=NGC 5139. The center of the cluster was covered with a mosaic of F435W, F625W, and F658N band data collected with HST ACS. The outer reaches were covered with a mosaic of U-, B-, V-, and I-band data collected with the 2.2 m ESO/MPI telescope. The final catalog includes ~1.7 million stars. We identified more than 3200 likely HB stars, the largest sample ever collected in a globular cluster. We found that the HB morphology changes with the radial distance from the cluster center. The relative number of extreme HB stars decreases from ~30% to ~21% when moving from the center toward the outer reaches of the cluster, while the fraction of less hot HB stars increases from ~62% to ~72%. The comparison between theory and observations indicates that the empirical star counts of HB stars are on average larger (30%-40%) than predicted by canonical evolutionary models. Moreover, the rate of HB stars is ~43% larger than the MSTO rate. We also compared theory and observations by assuming a mix of stellar populations made with 70% of canonical He (Y=0.23) stars and 30% of He-enhanced (Y=0.33, 0.42) stars. We found that the observed RG/MSTO ratio agrees with the predicted lifetimes of He-mixed stellar populations. The discrepancy between theory and observations decreases by a factor of 2 when compared with rates predicted by canonical He content models, but still 15%-25% (Y=0.42) and 15%-20% (Y=0.33) higher than observed. Furthermore, the ratios between HB and MSTO star counts are ~24% (Y=0.42) and 30% (Y=0.33) larger than predicted lifetime ratios. During the revision of this manuscript, Vittorio Castellani passed away on 2006 May 19. His suggestions, ideas, and personality will be greatly missed. Based on data obtained from the ESO Science Archive Facility and the Hubble Space Telescope Archive Facility.

  4. Comparison of Intra-cluster and M87 Halo Orphan Globular Clusters in the Virgo Cluster

    Science.gov (United States)

    Louie, Tiffany Kaye; Tuan, Jin Zong; Martellini, Adhara; Guhathakurta, Puragra; Toloba, Elisa; Peng, Eric; Longobardi, Alessia; Lim, Sungsoon

    2018-01-01

    We present a study of “orphan” globular clusters (GCs) — GCs with no identifiable nearby host galaxy — discovered in NGVS, a 104 deg2 CFHT/MegaCam imaging survey. At the distance of the Virgo cluster, GCs are bright enough to make good spectroscopic targets and many are barely resolved in good ground-based seeing. Our orphan GC sample is derived from a subset of NGVS-selected GC candidates that were followed up with Keck/DEIMOS spectroscopy. While our primary spectroscopic targets were candidate GC satellites of Virgo dwarf elliptical and ultra-diffuse galaxies, many objects turned out to be non-satellites based on a radial velocity mismatch with the Virgo galaxy they are projected close to. Using a combination of spectral characteristics (e.g., absorption vs. emission), Gaussian mixture modeling of radial velocity and positions, and extreme deconvolution analysis of ugrizk photometry and image morphology, these non-satellites were classified into: (1) intra-cluster GCs (ICGCs) in the Virgo cluster, (2) GCs in the outer halo of M87, (3) foreground Milky Way stars, and (4) background galaxies. The statistical distinction between ICGCs and M87 halo GCs is based on velocity distributions (mean of 1100 vs. 1300 km/s and dispersions of 700 vs. 400 km/s, respectively) and radial distribution (diffuse vs. centrally concentrated, respectively). We used coaddition to increase the spectral SNR for the two classes of orphan GCs and measured the equivalent widths (EWs) of the Mg b and H-beta absorption lines. These EWs were compared to single stellar population models to obtain mean age and metallicity estimates. The ICGCs and M87 halo GCs have = –0.6+/–0.3 and –0.4+/–0.3 dex, respectively, and mean ages of >~ 5 and >~ 10 Gyr, respectively. This suggests the M87 halo GCs formed in relatively high-mass galaxies that avoided being tidally disrupted by M87 until they were close to the cluster center, while IGCCs formed in relatively low-mass galaxies that were

  5. The Case of the Missing Cyanogen-rich AGB Stars in Galactic Globular Clusters

    DEFF Research Database (Denmark)

    Campbell, S. W.; Yong, D.; Wylie-de Boer, E. C.

    2012-01-01

    The handful of available observations of AGB stars in Galactic Globular Clusters suggest that the GC AGB populations are dominated by cyanogen-weak stars (eg. Norris et al. 1981; Sneden et al. 2000). This contrasts strongly with the distributions on the RGB (and other) populations, which generall...

  6. Search for continuous gravitational waves from neutron stars in globular cluster NGC 6544

    NARCIS (Netherlands)

    Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Phythian-Adams, A.T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.T.; Aguiar, O. D.; Aiello, L.; Ain, A.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, R.D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Bejger, M.; Bell, A. S.; Berger, B. K.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, M.J.; Birney, R.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, A.L.S.; Bock, O.; Boer, M.; Bogaert, J.G.; Bogan, C.; Bohe, A.; Bond, T.C; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Broida, J. E.; Brooks, A. F.; Brown, A.D.; Brown, D.; Brown, N. M.; Brunett, S.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Bustillo, J. Calderon; Callister, T. A.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Diaz, J. Casanueva; Casentini, C.; Caudill, S.; Cavaglia, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Baiardi, L. Cerboni; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.; Chan, M.; Chao, D. S.; Charlton, P.; Chassande-Mottin, E.; Cheeseboro, B. D.; Chen, H. Y.; Chen, Y; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Qian; Chua, S. S. Y.; Chung, E.S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P. -F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M., Jr.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, A.C.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J. -P.; Countryman, S. T.; Couvares, P.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, Laura; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dasgupta, A.; Costa, C. F. Da Silva; Dattilo, V.; Dave, I.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; De, S.; Debra, D.; Debreczeni, G.; Degallaix, J.; De laurentis, M.; Deleglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dergachev, V.A.; Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Devine, R. C.; Dhurandhar, S.; Diaz, M. C.; Di Fiore, L.; Giovanni, M. Di; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H. -B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel, T.; Evans, T. M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fan, X.M.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Fenyvesi, E.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M; Fournier, J. -D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gaur, G.; Gehrels, N.; Gemme, G.; Geng, P.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.P.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; Gonzalez, Idelmis G.; Castro, J. M. Gonzalez; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Lee-Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.M.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Buffoni-Hall, R.; Hall, E. D.; Hammond, G.L.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hanson, P.J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C. -J.; Haughian, K.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Henry, J.A.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hofman, D.; Holt, K.; Holz, D. E.; Hopkins, P.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J. -M.; Isi, M.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, D.H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jian, L.; Jimenez-Forteza, F.; Johnson, W.; Jones, I.D.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, K.; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.H.; Kanner, J. B.; Kapadia, S. J.; Karki, S.; Karvinen, K. S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kefelian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.E.; Key, J. S.; Khalili, F. Y.; Khan, I.; Khan., S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, Chi-Woong; Kim, Chunglee; Kim, J.; Kim, K.; Kim, Namjun; Kim, W.; Kim, Y.M.; Kimbrell, S. J.; King, E. J.; King, P. J.; Kissel, J. S.; Klein, B.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Krolak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kumar, R.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Laxen, M.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C.H.; Lee, K.H.; Lee, M.H.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Lewis, J. B.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Lombardi, A. L.; London, L. T.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lueck, H.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magana-Sandoval, F.; Zertuche, L. Magana; Magee, R. M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marka, S.; Marka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McRae, T.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, A. L.; Miller, B.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B.C.; Moore, J.C.; Moraru, D.; Gutierrez Moreno, M.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, S.D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P.G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Nedkova, K.; Nelemans, G.; Nelson, T. J. N.; Gutierrez-Neri, M.; Neunzert, A.; Newton-Howes, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J.; Oh, S. H.; Ohme, F.; Oliver, M. B.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.S; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca, A.; Perri, L. M.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poe, M.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L. G.; Puncken, O.; Punturo, M.; Puppo, P.; Puerrer, M.; Qi, H.; Qin, J.; Qiu, S.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rajan, C.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Ricci, F.; Riles, K.; Rizzo, D.M.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, R.; Romanov, G.; Romie, J. H.; Rosinska, D.; Rowan, S.; Ruediger, A.; Ruggi, P.; Ryan, K.A.; Sachdev, Perminder S; Sadecki, T.; Sadeghian, L.; Sakellariadou, M.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Sassolas, B.; Saulson, P. R.; Sauter, O. E. S.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J; Schmidt, P.; Schnabel, R.B.; Schofield, R. M. S.; Schoebeck, A.; Schreiber, K.E.C.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, M.S.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Setyawati, Y.; Shaddock, D. A.; Shaffer, T. J.; Shahriar, M. S.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, António Dias da; Singer, A; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, R. J. E.; Smith, N.D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stone, J.R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S. E.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.; Sutton, P. J.; Swinkels, B. L.; Szczepanczyk, M. J.; Tacca, M.D.; Talukder, D.; Tanner, D. B.; Tapai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, W.R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Toland, K.; Tomlinson, C.; Tonelli, M.; Tornasi, Z.; Torres, C. V.; Torrie, C. I.; Toyra, D.; Travasso, F.; Traylor, G.; Trifiro, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; Van Beuzekom, Martin; van den Brand, J. F. J.; Van Den Broeck, C.F.F.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasuth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P.J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Vicere, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J. -Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D. V.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, MT; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L. -W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.M.; Wessels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whiting, B. F.; Williams, D.R.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.; Worden, J.; Wright, J.L.; Wu, D.S.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yu, H.; Yvert, M.; Zadrozny, A.; Zangrando, L.; Zanolin, M.; Zendri, J. -P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; Sigurdsson, S.

    2017-01-01

    We describe a directed search for continuous gravitational waves in data from the sixth initial LIGO science run. The target was the nearby globular cluster NGC 6544 at a distance of approximate to 2.7 kpc. The search covered a broad band of frequencies along with first and second frequency

  7. THE SIZE DIFFERENCE BETWEEN RED AND BLUE GLOBULAR CLUSTERS IS NOT DUE TO PROJECTION EFFECTS

    International Nuclear Information System (INIS)

    Webb, Jeremy J.; Harris, William E.; Sills, Alison

    2012-01-01

    Metal-rich (red) globular clusters in massive galaxies are, on average, smaller than metal-poor (blue) globular clusters. One of the possible explanations for this phenomenon is that the two populations of clusters have different spatial distributions. We test this idea by comparing clusters observed in unusually deep, high signal-to-noise images of M87 with a simulated globular cluster population in which the red and blue clusters have different spatial distributions, matching the observations. We compare the overall distribution of cluster effective radii as well as the relationship between effective radius and galactocentric distance for both the observed and simulated red and blue sub-populations. We find that the different spatial distributions does not produce a significant size difference between the red and blue sub-populations as a whole or at a given galactocentric distance. These results suggest that the size difference between red and blue globular clusters is likely due to differences during formation or later evolution.

  8. The SLUGGS survey: globular cluster stellar population trends from weak absorption lines in stacked spectra

    Science.gov (United States)

    Usher, Christopher; Forbes, Duncan A.; Brodie, Jean P.; Romanowsky, Aaron J.; Strader, Jay; Conroy, Charlie; Foster, Caroline; Pastorello, Nicola; Pota, Vincenzo; Arnold, Jacob A.

    2015-01-01

    As part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey, we stack 1137 Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) spectra of globular clusters from 10 galaxies to study their stellar populations in detail. The stacked spectra have median signal-to-noise ratios of ˜90 Å-1. Besides the calcium triplet, we study weaker sodium, magnesium, titanium and iron lines as well as the Hα and higher order Paschen hydrogen lines. In general, the stacked spectra are consistent with old ages and a Milky Way-like initial mass function. However, we see different metal line index strengths at fixed colour and magnitude, and differences in the calcium triplet-colour relation from galaxy to galaxy. We interpret this as strong evidence for variations in the globular cluster colour-metallicity relation between galaxies. Two possible explanations for the colour-metallicity relation variations are that the average ages of globular clusters vary from galaxy to galaxy or that the average abundances of light elements (i.e. He, C, N and O) differ between galaxies. Stacking spectra by magnitude, we see that the colours become redder and metal line indices stronger with brighter magnitudes. These trends are consistent with the previously reported `blue tilts' being mass-metallicity relations.

  9. The Size Difference between Red and Blue Globular Clusters is not due to Projection Effects

    Science.gov (United States)

    Webb, Jeremy J.; Harris, William E.; Sills, Alison

    2012-11-01

    Metal-rich (red) globular clusters in massive galaxies are, on average, smaller than metal-poor (blue) globular clusters. One of the possible explanations for this phenomenon is that the two populations of clusters have different spatial distributions. We test this idea by comparing clusters observed in unusually deep, high signal-to-noise images of M87 with a simulated globular cluster population in which the red and blue clusters have different spatial distributions, matching the observations. We compare the overall distribution of cluster effective radii as well as the relationship between effective radius and galactocentric distance for both the observed and simulated red and blue sub-populations. We find that the different spatial distributions does not produce a significant size difference between the red and blue sub-populations as a whole or at a given galactocentric distance. These results suggest that the size difference between red and blue globular clusters is likely due to differences during formation or later evolution.

  10. The Observational and Theoretical Tidal Radii of Globular Clusters in M87

    Science.gov (United States)

    Webb, Jeremy J.; Sills, Alison; Harris, William E.

    2012-02-01

    Globular clusters have linear sizes (tidal radii) which theory tells us are determined by their masses and by the gravitational potential of their host galaxy. To explore the relationship between observed and expected radii, we utilize the globular cluster population of the Virgo giant M87. Unusually deep, high signal-to-noise images of M87 are used to measure the effective and limiting radii of approximately 2000 globular clusters. To compare with these observations, we simulate a globular cluster population that has the same characteristics as the observed M87 cluster population. Placing these simulated clusters in the well-studied tidal field of M87, the orbit of each cluster is solved and the theoretical tidal radius of each cluster is determined. We compare the predicted relationship between cluster size and projected galactocentric distance to observations. We find that for an isotropic distribution of cluster velocities, theoretical tidal radii are approximately equal to observed limiting radii for R gc < 10 kpc. However, the isotropic simulation predicts a steep increase in cluster size at larger radii, which is not observed in large galaxies beyond the Milky Way. To minimize the discrepancy between theory and observations, we explore the effects of orbital anisotropy on cluster sizes, and suggest a possible orbital anisotropy profile for M87 which yields a better match between theory and observations. Finally, we suggest future studies which will establish a stronger link between theoretical tidal radii and observed radii.

  11. THE OBSERVATIONAL AND THEORETICAL TIDAL RADII OF GLOBULAR CLUSTERS IN M87

    International Nuclear Information System (INIS)

    Webb, Jeremy J.; Sills, Alison; Harris, William E.

    2012-01-01

    Globular clusters have linear sizes (tidal radii) which theory tells us are determined by their masses and by the gravitational potential of their host galaxy. To explore the relationship between observed and expected radii, we utilize the globular cluster population of the Virgo giant M87. Unusually deep, high signal-to-noise images of M87 are used to measure the effective and limiting radii of approximately 2000 globular clusters. To compare with these observations, we simulate a globular cluster population that has the same characteristics as the observed M87 cluster population. Placing these simulated clusters in the well-studied tidal field of M87, the orbit of each cluster is solved and the theoretical tidal radius of each cluster is determined. We compare the predicted relationship between cluster size and projected galactocentric distance to observations. We find that for an isotropic distribution of cluster velocities, theoretical tidal radii are approximately equal to observed limiting radii for R gc < 10 kpc. However, the isotropic simulation predicts a steep increase in cluster size at larger radii, which is not observed in large galaxies beyond the Milky Way. To minimize the discrepancy between theory and observations, we explore the effects of orbital anisotropy on cluster sizes, and suggest a possible orbital anisotropy profile for M87 which yields a better match between theory and observations. Finally, we suggest future studies which will establish a stronger link between theoretical tidal radii and observed radii.

  12. A Fossil Bulge Globular Cluster Revealed by very Large Telescope Multi-conjugate Adaptive Optics

    Czech Academy of Sciences Publication Activity Database

    Ortolani, S.; Barbuy, B.; Momany, Y.; Saviane, I.; Bica, E.; Jílková, L.; Salerno, G.M.; Jungwiert, Bruno

    2011-01-01

    Roč. 737, č. 1 (2011), 31/1-31/9 ISSN 0004-637X Institutional research plan: CEZ:AV0Z10030501 Keywords : galaxy * globular clusters Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 6.024, year: 2011

  13. Multiple populations along the asymptotic giant branch of the globular cluster M 4

    NARCIS (Netherlands)

    Lardo, C.; Salaris, M.; Savino, A.; Donati, P.; Stetson, P. B.; Cassisi, S.

    2016-01-01

    Nearly all Galactic globular clusters host stars that display characteristic abundance anti-correlations, like the O-rich/Na-poor pattern typical of field halo stars, together with O-poor/Na-rich additional components. A recent spectroscopic investigation questioned the presence of O-poor/Na-rich

  14. NGC 6362: The Least Massive Globular Cluster with Chemically Distinct Multiple Populations

    NARCIS (Netherlands)

    Mucciarelli, Alessio; Dalessandro, Emanuele; Massari, Davide; Bellazzini, Michele; Ferraro, Francesco R.; Lanzoni, Barbara; Lardo, Carmela; Salaris, Maurizio; Cassisi, Santi

    2016-01-01

    We present the first measure of Fe and Na abundances in NGC 6362, a low-mass globular cluster (GC) where first- and second-generation stars are fully spatially mixed. A total of 160 member stars (along the red giant branch (RGB) and the red horizontal branch (RHB)) were observed with the

  15. VizieR Online Data Catalog: Radial velocities in seven globular clusters (Lardo+, 2015)

    Science.gov (United States)

    Lardo, C.; Pancino, E.; Bellazzini, M.; Bragaglia, A.; Donati, P.; Gilmore, G.; Randich, S.; Feltzing, S.; Jeffries, R. D.; Vallenari, A.; Alfaro, E. J.; Allende Prieto, C.; Flaccomio, E.; Koposov, S. E.; Recio-Blanco, A.; Bergemann, M.; Carraro, G.; Costado, M. T.; Damiani, F.; Hourihane, A.; Jofree, P.; de Laverny, P.; Marconi, G.; Masseron, T.; Morbidelli, L.; Sacco, G. G.; Worley, C. C.

    2014-11-01

    Velocities are given for 1826 stars in the field of the globular clusters NGC 1851, NGC 2808, NGC 4372, NGC 4833, NGC 5927, NGC 6752, and NGC 7078 observed with FLAMES/GIRAFFE@VLT. The table provides the individual identifications, coordinates, V magnitudes, velocities and their associated uncertainties for each star. (2 data files).

  16. Hubble Space Telescope ACS wide-field photometry of the sombrero galaxy globular cluster system

    NARCIS (Netherlands)

    Spitler, L.; Larsen, S.S.; Strader, J.; Brodie, J.P.; Forbes, D.A.; Beasley, M.A.

    2006-01-01

    A detailed imaging analysis of the globular cluster (GC) system of the Sombrero galaxy (NGC 4594) has been accomplished using a six-image mosaic from the Hubble Space Telescope Advanced Camera for Surveys. The quality of the data is such that contamination by foreground stars and background galaxies

  17. Photoelectric UBVRI sequences in the Galactic globular clusters NGC 6752 and NGC 6864

    International Nuclear Information System (INIS)

    Alvarado, F.; Wenderoth, E.; Alcaino, G.; Liller, W.

    1990-01-01

    UBVRI photoelectric sequences for the Galactic globular clusters NGC 6752 and NGC 6864 are presented. Both of them include fields suitable for CCD exposures. From five UBV sequences in NGC 6572, only five stars are in common with the previous works. 15 refs

  18. The ACS Virgo Cluster Survey XVI. Selection Procedure and Catalogs of Globular Cluster Candidates

    Science.gov (United States)

    Jordán, Andrés; Peng, Eric W.; Blakeslee, John P.; Côté, Patrick; Eyheramendy, Susana; Ferrarese, Laura; Mei, Simona; Tonry, John L.; West, Michael J.

    2009-01-01

    We present catalogs of globular cluster candidates for the 100 galaxies of the Advanced Camera for Surveys Virgo Cluster Survey, a large program to carry out imaging of early-type members of the Virgo Cluster using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. We describe the procedure used to select bona fide globular cluster candidates out of the full list of detections based on model-based clustering methods with the use of expected contamination catalogs constructed using blank field observations and which are customized for each galaxy. We also present the catalogs of expected contaminants for each of our target galaxies. For each detected source we measure its position, magnitudes in the F475W (≈ Sloan g) and F850LP (≈ Sloan z) bandpasses, and half-light radii by fitting point-spread function convolved King models to the observed light distribution. These measurements are presented for 20,375 sources, of which 12,763 are likely to be globular clusters. Finally, we detail the calculation of the aperture corrections adopted for the globular cluster photometry. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  19. Disrupted globular clusters and the gamma-ray excess in the Galactic Centre

    Science.gov (United States)

    Fragione, Giacomo; Antonini, Fabio; Gnedin, Oleg Y.

    2018-04-01

    The Fermi Large Area Telescope has provided the most detailed view towards the Galactic Centre (GC) in high-energy gamma-rays. Besides the interstellar emission and point source contributions, the data suggest a residual diffuse gamma-ray excess. The similarity of its spatial distribution with the expected profile of dark matter has led to claims that this may be evidence for dark matter particle annihilation. Here, we investigate an alternative explanation that the signal originates from millisecond pulsars (MSPs) formed in dense globular clusters and deposited at the GC as a consequence of cluster inspiral and tidal disruption. We use a semi-analytical model to calculate the formation, migration, and disruption of globular clusters in the Galaxy. Our model reproduces the mass of the nuclear star cluster and the present-day radial and mass distribution of globular clusters. For the first time, we calculate the evolution of MSPs from disrupted globular clusters throughout the age of the Galaxy and consistently include the effect of the MSP spin-down due to magnetic-dipole braking. The final gamma-ray amplitude and spatial distribution are in good agreement with the Fermi observations and provide a natural astrophysical explanation for the GC excess.

  20. The chemical composition of the low-mass Galactic globular cluster NGC 6362

    NARCIS (Netherlands)

    Massari, D.; Mucciarelli, A.; Dalessandro, E.; Bellazzini, M.; Cassisi, S.; Fiorentino, G.; Ibata, R. A.; Lardo, C.; Salaris, M.

    We present chemical abundances for 17 elements in a sample of 11 red giant branch stars in NGC 6362 from UVES spectra. NGC 6362 is one of the least massive globulars where multiple populations have been detected, yet its detailed chemical composition has not been investigated so far. NGC 6362 turns

  1. A comparison of two mass distributions applicable to globular clusters and dwarf galaxies

    Directory of Open Access Journals (Sweden)

    Ninković Slobodan D.

    2004-01-01

    Full Text Available A particular case of mass distribution in stellar systems, already described in the literature, is compared to the King model of mass distribution. For the cases which would correspond to the description of real stellar systems such as the globular clusters and dwarf galaxies, one finds a satisfactory agreement between these two mass distributions.

  2. Three Ancient Halo Subgiants: Precise Parallaxes, Compositions, Ages, and Implications for Globular Clusters

    DEFF Research Database (Denmark)

    VandenBerg, Don A.; Bond, Howard E.; Nelan, Edmund P.

    2014-01-01

    very soon after the Big Bang. (Stellar models that neglect diffusive processes seem to be ruled out as they would predict that HD 140283 is ~1.5 Gyr older than the universe.) The field halo subgiants appear to be older than globular clusters of similar metallicities: if distances close to those implied...

  3. GeMS MCAO observations of the Galactic globular cluster NGC 2808: the absolute age

    NARCIS (Netherlands)

    Massari, D.; Fiorentino, G.; McConnachie, A.; Bono, G.; Dall'Ora, M.; Ferraro, I.; Iannicola, G.; Stetson, P. B.; Turri, P.; Tolstoy, E.

    2016-01-01

    Context. Globular clusters are the oldest stellar systems in the Milky Way, and they probe the early epoch of the Galaxy formation. However, the uncertainties on their absolute age are still too large to soundly constrain how the Galactic structures have assembled. Aims: The aim of this work is to

  4. Electrorheological properties of suspensions of hollow globular titanium oxide/polypyrrole particles

    Czech Academy of Sciences Publication Activity Database

    Sedlačík, M.; Mrlík, M.; Pavlínek, V.; Sáha, P.; Quadrat, Otakar

    2012-01-01

    Roč. 290, č. 1 (2012), s. 41-48 ISSN 0303-402X R&D Projects: GA ČR GA202/09/1626 Institutional research plan: CEZ:AV0Z40500505 Keywords : electrorheology * titanium oxide * hollow globular clusters Subject RIV: JI - Composite Materials Impact factor: 2.161, year: 2012

  5. The deposition of globular polypyrrole and polypyrrole nanotubes on cotton textile

    Czech Academy of Sciences Publication Activity Database

    Bober, Patrycja; Stejskal, Jaroslav; Šeděnková, Ivana; Trchová, Miroslava; Martinková, L.; Marek, J.

    2015-01-01

    Roč. 356, 30 November (2015), s. 737-741 ISSN 0169-4332 R&D Projects: GA TA ČR(CZ) TE01020022 Institutional support: RVO:61389013 Keywords : conducting textile * cotton * globular polypyrrole Subject RIV: CG - Electrochemistry Impact factor: 3.150, year: 2015

  6. VLT/UVES abundances of individual stars in the Fornax dwarf spheroidal globular clusters

    NARCIS (Netherlands)

    Letarte, B.; Hill, V.; Jablonka, P.; Tolstoy, E.; Randich, S; Pasquini, L

    2006-01-01

    We present high resolution abundance analysis of nine stars belonging to three of the five globular clusters (GCs) of the Fornax dwarf galaxy. The spectra were taken with UVES at a resolution of 43 000. We find them to be slightly more metal-poor than what was previously calculated with other

  7. Massive binaries as the source of abundance anomalies in globular clusters

    NARCIS (Netherlands)

    de Mink, S.E.|info:eu-repo/dai/nl/304833231; Pols, O.R.|info:eu-repo/dai/nl/111811155; Langer, N.|info:eu-repo/dai/nl/304829498; Izzard, R.G.|info:eu-repo/dai/nl/304836052

    2009-01-01

    Abundance anomalies observed in globular cluster stars indicate pollution with material processed by hydrogen burning. Two main sources have been suggested: asymptotic giant branch (AGB) stars and massive stars rotating near the break-up limit (spin stars). We propose massive binaries as an

  8. On the blind use of statistical tools in the analysis of globular cluster stars

    Science.gov (United States)

    D'Antona, Francesca; Caloi, Vittoria; Tailo, Marco

    2018-04-01

    As with most data analysis methods, the Bayesian method must be handled with care. We show that its application to determine stellar evolution parameters within globular clusters can lead to paradoxical results if used without the necessary precautions. This is a cautionary tale on the use of statistical tools for big data analysis.

  9. Modular organization of proteins containing C1q-like globular domain.

    Science.gov (United States)

    Kishore, U; Reid, K B

    1999-05-01

    The first step in the activation of the classical pathway of complement cascade by immune complexes involves the binding of the six globular heads of C1q to the Fc regions of immunoglobulin G (IgG) or immunoglobulin M (IgM). The globular heads of C1q are located C-terminal to the six triple-helical stalks present in the molecule, each head is considered to be composed of the C-terminal halves (3 x 135 residues) of one A-, one B- and one C-chain. It is not known if the C-terminal globular regions, present in each of the three types of chains, are independently folded modules (with each chain having distinct binding properties towards immunoglobulins) or whether the different binding functions of C1q are dependent upon a globular structure which relies on contributions from all three chains. Recent reports of recombinant production and characterisation of soluble globular head regions of all the three chains indicate that the globular regions of C1q may adopt a modular organization, i.e., each globular head of C1q may be composed of three, structurally and functionally, independent domains, thus retaining multivalency in the form of a heterotrimer. Modules of the same type as the C1q C-terminal module are also found in a variety of noncomplement proteins that include the C-terminal regions of the human type VIII and type X collagens, precerebellin, the chipmunk hibernation proteins, the human endothelial cell protein, multimerin, the serum protein, Acrp-30 which is secreted from mouse adipocytes, and the sunfish inner-ear specific structural protein. The C1q molecule is the only one of these proteins for which, to date, a function has been ascribed to the module. The existence of a shared structural region between C1q and certain collagens may suggest an evolutionarily common ancestral precursor. Various structural and biochemical data suggest that these modules may be responsible for multimerisation through patches of aromatic residues within them.

  10. Upper Extremity Length Equalization

    OpenAIRE

    DeCoster, Thomas A.; Ritterbusch, John; Crawford, Mark

    1992-01-01

    Significant upper extremity length inequality is uncommon but can cause major functional problems. The ability to position and use the hand may be impaired by shortness of any of the long bones of the upper extremity. In many respects upper and lower extremity length problems are similar. They most commonly occur after injury to a growing bone and the treatment modalities utilized in the lower extremity may be applied to the upper extremity. These treatment options include epiphysiodesis, sho...

  11. LUMINOSITY FUNCTIONS OF LMXBs IN CENTAURUS A: GLOBULAR CLUSTERS VERSUS THE FIELD

    International Nuclear Information System (INIS)

    Voss, Rasmus; Gilfanov, Marat; Sivakoff, Gregory R.; Sarazin, Craig L.; Kraft, Ralph P.; Jordan, Andres; Brassington, Nicola J.; Evans, Daniel A.; Murray, Stephen S.; Raychaudhury, Somak; Birkinshaw, Mark; Worrall, Diana M.; Croston, Judith H.; Hardcastle, Martin J.; Forman, William R.; Jones, Christine; Harris, William E.; Woodley, Kristin A.; Juett, Adrienne M.

    2009-01-01

    We study the X-ray luminosity function (XLF) of low-mass X-ray binaries (LMXB) in the nearby early-type galaxy Centaurus A, concentrating primarily on two aspects of binary populations: the XLF behavior at the low-luminosity limit and the comparison between globular cluster and field sources. The 800 ksec exposure of the deep Chandra VLP program allows us to reach a limiting luminosity of ∼8 x 10 35 erg s -1 , about ∼2-3 times deeper than previous investigations. We confirm the presence of the low-luminosity break of the overall LMXB XLF at log(L X ) ∼ 37.2-37.6, below which the luminosity distribution follows a dN/d(ln L) ∼ const law. Separating globular cluster and field sources, we find a statistically significant difference between the two luminosity distributions with a relative underabundance of faint sources in the globular cluster population. This demonstrates that the samples are drawn from distinct parent populations and may disprove the hypothesis that the entire LMXB population in early-type galaxies is created dynamically in globular clusters. As a plausible explanation for this difference in the XLFs, we suggest an enhanced fraction of helium-accreting systems in globular clusters, which are created in collisions between red giants and neutron stars. Due to the four times higher ionization temperature of He, such systems are subject to accretion disk instabilities at ∼20 times higher mass accretion rate and, therefore, are not observed as persistent sources at low luminosities.

  12. The Frequency of Binary Stars in the Globular Cluster M71

    Science.gov (United States)

    Barden, S. C.; Armandroff, T. E.; Pryor, C. P.

    1994-12-01

    The frequency of binary stars is a fundamental property of a stellar population. A comparison of the frequency of binaries in globular clusters with those in the field halo and disk populations tests the similarity of star formation in those environments. Binary stars in globular clusters also act as an energy source which ``heats" the cluster through super-elastic encounters with other stars and binaries. Such encounters can not only profoundly affect the dynamical evolution of the cluster, they can disrupt the widely separated binaries and catalyze the formation of exotic objects such as blue stragglers, x-ray binaries, and milli-second pulsars. We have used the KPNO 4-m and the multi-fiber instruments Nessie and Hydra to measure radial velocities at 4 epochs over two years for a sample of 126 stars in the globular cluster M71. Velocity errors are under 1 km s(-1) for the brighter stars and under 2 km s(-1) for the majority of our data set. These velocities will be valuable for studying the kinematics of M71, but here we focus on searching for binaries. The faintest stars are at V=17, or just above the main sequence turnoff. Our sample is thus deeper than any published globular cluster binary search utilizing spectroscopic techniques. By observing smaller stars, we double the number of decades of binary periods sampled compared to previous studies and come within a factor of 4 of the shortest possible periods for turnoff stars. This wider period window has produced the largest known sample of binaries in a globular cluster. Four stars show velocity ranges larger than 20 km s(-1) , nine have ranges larger than 10 km s(-1) , and others are clearly variable. We will compare the radial distribution of these stars to that predicted by theory and derive the main-sequence binary fraction.

  13. The Primordial Binary Fractions for a Sample of 35 Galactic Globular Clusters with HST Observations

    Science.gov (United States)

    Ji, Jun; Bregman, J. N.

    2011-01-01

    Binaries are thought to be the primary heating energy source in globular clusters, since they can convert their binding energy to kinetic energy of the encounter stars through dynamical interactions. Even a small fraction of binaries are sufficient to prevent globular clusters from core collapse for many relaxation times. But the observed global binary fractions in globular clusters are still uncertain. Here we present our preliminary results for the binary fractions of 35 Galactic globular clusters with the HST archival data in the F606W and F814W bands. We use the secondary sequence method on the color-magnitude diagram to statistically account for the main-sequence-main-sequence binaries (primordial binaries). The binary fraction is obtained by fitting the residual color distribution after subtracting the color of the main-sequence ridge line, with properly modeling the photometric errors, field stars, and blending stars. We estimate the binary fractions with 3 different assumed binary mass-ratio distribution functions, and the current data sets are still not good to constrain the binary mass-ratio distributions. In our sample, we obtain a mean binary fraction of (9.1±4.1)% within their half-mass radii assuming a flat binary mass-ratio distribution. There is no clear trend for the binary fractions against the dynamical ages and [Fe/H], but binary fractions tend to increase with the absolute magnitudes of clusters. This is probably because less massive globular clusters consume fewer binaries through dynamical interactions due to their lower stellar density.

  14. Short-term X-ray variability of the globular cluster source 4U 1820 - 30 (NGC 6624)

    Science.gov (United States)

    Stella, L.; Kahn, S. M.; Grindlay, J. E.

    1984-01-01

    Analytical techniques for improved identification of the temporal and spectral variability properties of globular cluster and galactic bulge X-ray sources are described in terms of their application to a large set of observations of the source 4U 1820 - 30 in the globular cluster NGC 6624. The autocorrelation function, cross-correlations, time skewness function, erratic periodicities, and pulse trains are examined. The results are discussed in terms of current models with particular emphasis on recent accretion disk models. It is concluded that the analyzed observations provide the first evidence for shot-noise variability in a globular cluster X-ray source.

  15. Evidence for a chemical enrichment coupling of globular clusters and field stars in the Fornax dSph

    Science.gov (United States)

    Hendricks, Benjamin; Boeche, Corrado; Johnson, Christian I.; Frank, Matthias J.; Koch, Andreas; Mateo, Mario; Bailey, John I.

    2016-01-01

    The globular cluster H4, located in the center of the Fornax dwarf spheroidal galaxy, is crucial for understanding the formation and chemical evolution of star clusters in low-mass galactic environments. H4 is peculiar because the cluster is significantly more metal-rich than the galaxy's other clusters, is located near the galaxy center, and may also be the youngest cluster in the galaxy. In this study, we present detailed chemical abundances derived from high-resolution (R ~ 28 000) spectroscopy of an isolated H4 member star for comparison with a sample of 22 nearby Fornax field stars. We find the H4 member to be depleted in the alpha-elements Si, Ca, and Ti with [Si/Fe] = -0.35 ± 0.34, [Ca/Fe] = + 0.05 ± 0.08, and [Ti/Fe] = -0.27 ± 0.23, resulting in an average [α/Fe] = -0.19 ± 0.14. If this result is representative of the average cluster properties, H4 is the only known system with a low [α/Fe] ratio and a moderately low metallicity embedded in an intact birth environment. For the field stars we find a clear sequence, seen as an early depletion in [α/Fe] at low metallicities, in good agreement with previous measurements. H4 falls on top of the observed field star [α/Fe] sequence and clearly disagrees with the properties of Milky Way halo stars. We therefore conclude that within a galaxy, the chemical enrichment of globular clusters may be closely linked to the enrichment pattern of the field star population. The low [α/Fe] ratios of H4 and similar metallicity field stars in Fornax give evidence that slow chemical enrichment environments, such as dwarf galaxies, may be the original hosts of alpha-depleted clusters in the halos of the Milky Way and M31. This article includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  16. Weather and Climate Extremes

    National Research Council Canada - National Science Library

    Krause, Paul

    1997-01-01

    .... All extremes are presented in terms of their location and date and, where supportive information is available in the professional literature, detailed discussions of the extreme event are provided...

  17. AN EXTREMELY CARBON-RICH, EXTREMELY METAL-POOR STAR IN THE SEGUE 1 SYSTEM

    International Nuclear Information System (INIS)

    Norris, John E.; Yong, David; Gilmore, Gerard; Wyse, Rosemary F. G.; Frebel, Anna

    2010-01-01

    We report the analysis of high-resolution, high signal-to-noise ratio, spectra of an extremely metal-poor, extremely C-rich red giant, Seg 1-7, in Segue 1-described in the literature alternatively as an unusually extended globular cluster or an ultra-faint dwarf galaxy. The radial velocity of Seg 1-7 coincides precisely with the systemic velocity of Segue 1, and its chemical abundance signature of [Fe/H] = -3.52, [C/Fe] = +2.3, [N/Fe] = +0.8, [Na/Fe] = +0.53, [Mg/Fe] = +0.94, [Al/Fe] = +0.23, and [Ba/Fe] < -1.0 is similar to that of the rare and enigmatic class of Galactic halo objects designated CEMP-no (carbon-rich, extremely metal-poor with no enhancement (over solar ratios) of heavy neutron-capture elements). This is the first star in a Milky Way 'satellite' that unambiguously lies on the metal-poor, C-rich branch of the Aoki et al. bimodal distribution of field halo stars in the ([C/Fe], [Fe/H])-plane. Available data permit us only to identify Seg 1-7 as a member of an ultra-faint dwarf galaxy or as debris from the Sgr dwarf spheroidal galaxy. In either case, this demonstrates that at extremely low abundance, [Fe/H ] <-3.0, star formation and associated chemical evolution proceeded similarly in the progenitors of both the field halo and satellite systems. By extension, this is consistent with other recent suggestions that the most metal-poor dwarf spheroidal and ultra-faint dwarf satellites were the building blocks of the Galaxy's outer halo.

  18. Extreme environment electronics

    CERN Document Server

    Cressler, John D

    2012-01-01

    Unfriendly to conventional electronic devices, circuits, and systems, extreme environments represent a serious challenge to designers and mission architects. The first truly comprehensive guide to this specialized field, Extreme Environment Electronics explains the essential aspects of designing and using devices, circuits, and electronic systems intended to operate in extreme environments, including across wide temperature ranges and in radiation-intense scenarios such as space. The Definitive Guide to Extreme Environment Electronics Featuring contributions by some of the world's foremost exp

  19. Bio systematics of two species of the genus globular ia L. in Jordan and Tuns ia (Research Note)

    International Nuclear Information System (INIS)

    Oran, A. S.; Kochkar, N.; Raies, A.

    1999-01-01

    The status of the genus Globular ia L. in Jordan and Tunisia is presented. Bio systematic data related to morphology, habitats, geographical distribution, pollen and seed morphology as revealed by both light and scanning electron microscopy were studied based on material collected from both countries. Based on the collected bio systematic information on, this study has confirmed that only one species Globular ia arabica ac curs in Jordan and one species, G. alypum occurs in Tunisia. (authors). 12 refs., 1 table. 1 fig

  20. A period-luminosity relation for Mira variables in globular clusters and its impact on the distance scale

    International Nuclear Information System (INIS)

    Menzies, J.W.; Whitelock, P.A.

    1985-01-01

    JHKL photometry is presented for 31 red variables in 15 galactic globular clusters. The photometry of the Mira variables is used to find absolute bolometric magnitudes and an Msub(bol)-log P relation which differs from the one found for LMC Miras. This can be understood only if there is some systematic error in the globular cluster and/or LMC distance scales or if there is some fundamental difference between the cluster Miras and those in the LMC. (author)

  1. Extreme value distributions

    CERN Document Server

    Ahsanullah, Mohammad

    2016-01-01

    The aim of the book is to give a through account of the basic theory of extreme value distributions. The book cover a wide range of materials available to date. The central ideas and results of extreme value distributions are presented. The book rwill be useful o applied statisticians as well statisticians interrested to work in the area of extreme value distributions.vmonograph presents the central ideas and results of extreme value distributions.The monograph gives self-contained of theory and applications of extreme value distributions.

  2. Another non-segregated Blue Straggler population in a globular cluster: the case of NGC 2419.

    Science.gov (United States)

    Dalessandro, E.; Lanzoni, B.; Ferraro, F. R.; Vespe, F.; Bellazzini, M.; Rood, R. T.

    We have used a combination of ACS-HST high-resolution and wide-field SUBARU data in order to study the Blue Straggler Star (BSS) population over the entire extension of the remote Galactic globular cluster NGC 2419. The radial distribution of the selected BSS is the same as that of the other cluster stars. In this sense the BSS radial distribution is like that of omega Centauri and unlike that of all Galactic globular clusters studied to date, which have highly centrally segregated distributions and in most cases a pronounced upturn in the external regions. As in the case of omega Centauri, this evidence indicates that NGC 2419 is not yet relaxed even in the central regions. This observational fact is in agreement with estimated half-mass relaxation time, which is of the order of the cluster age.

  3. Globular cluster neutron stars and the determination of the dense matter equation of state

    Science.gov (United States)

    Guillot, Sebastien

    2016-09-01

    Combining measurements of the mass and radius of multiple neutron stars (NSs) represents the most promising way to determine the equation of state of dense NS matter. NSs in quiescent low-mass x-ray binaries (qLMXB) located in globular clusters have placed useful constraints on the equation of state. The statistical approaches combining measurements from multiple NSs can be further improved by the addition of more NS observations. We propose here to obtain a high signal to noise spectrum of the qLMXB in M30, the only low-absorption globular cluster qLMXBs that does not have deep X-ray observations, and which requires Chandra unmatched angular resolution. The 300 ks proposed observation will permit measurement of the NS radius with 12-15% uncertainties.

  4. A detached stellar-mass black hole candidate in the globular cluster NGC 3201

    Science.gov (United States)

    Giesers, Benjamin; Dreizler, Stefan; Husser, Tim-Oliver; Kamann, Sebastian; Anglada Escudé, Guillem; Brinchmann, Jarle; Carollo, C. Marcella; Roth, Martin M.; Weilbacher, Peter M.; Wisotzki, Lutz

    2018-03-01

    As part of our massive spectroscopic survey of 25 Galactic globular clusters with MUSE, we performed multiple epoch observations of NGC 3201 with the aim of constraining the binary fraction. In this cluster, we found one curious star at the main-sequence turn-off with radial velocity variations of the order of 100 km s- 1, indicating the membership to a binary system with an unseen component since no other variations appear in the spectra. Using an adapted variant of the generalized Lomb-Scargle periodogram, we could calculate the orbital parameters and found the companion to be a detached stellar-mass black hole with a minimum mass of 4.36 ± 0.41 M⊙. The result is an important constraint for binary and black hole evolution models in globular clusters as well as in the context of gravitational wave sources.

  5. Intrachromosomal exchange aberrations predicted on the basis of globular interphase chromosome model

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, S.G.; Eidelman, Yu.A

    2002-07-01

    One of the key questions in understanding mechanisms of chromosome aberration production is how does interphase chromosome structure affect aberration formation. To explore this a modelling approach is presented which combines Monte Carlo simulation of both a particle track and interphase chromosome structure. The structural state of interphase chromosome influences a dose-effect relationship for intrachromosomal exchange aberrations (intrachanges). It is shown that intrachanges are induced frequently by both X rays and a particles if the chromosome is in the condensed globular but not in the decondensed coiled state. Truly simple intra-arm intrachanges induced by X rays are dose squared in coiled chromosomes, but exhibit linear dose dependence in globular chromosomes. Experimental data on interarm intrachanges obtained by dual arm chromosome painting are analysed by means of the technique presented. Results of analysis support the conclusion about the arms proximity of chromosome 1 in human lymphocytes. (author)

  6. THE INFLUENCE OF POTASSIUM DICHROMATE Cr (VI ADMINISTRATION DURATION ON GLOBULAR RESISTANCE IN FEMALE RATS

    Directory of Open Access Journals (Sweden)

    LETIŢIA STANA

    2009-05-01

    Full Text Available The „in vivo” experiment has had as aim the study of different Cr(VI doses administration on globular resistance in female rats related to administration duration. Study was carried out on 56 female rats divided in 8 groups, 6 experimental and 2 control that received potassium dichromate in drinking water in doses of 25 ppm, 50 ppm and 75ppm Cr(VI, for 3 months, respectively, 6 months. Decrease of globular resistance (in terms of haemolysis degree in hypotonic solutions at increasing dose (up to 0.8% NaCl at 75 ppm dose in all experimental groups, in direct relation with the duration of administration was registered. Control groups were in physiological limits. The results of the present study revealed the affecting of erythrocyte membrane in function of administration duration and chromium intake level, because of oxidative lesions produced by it.

  7. Wide-Field Washington Photometry of the NGC 5128 Globular Cluster System

    Science.gov (United States)

    Geisler, D.; Harris, G. L. H.; Reid, M.; Milne, M.; Hulme, S. C.; Kidd, T. T.; Harris, W. E.; Schmidt, B. P.; Hesser, J. E.

    2004-05-01

    We have obtained deep imaging in the Washington CMT1 filters for an area of almost 2 square degrees centered on NGC 5128 in order to investigate its globular cluster system. Our data suffers from severe foreground and background contamination problems. Nonetheless, we can examine some of the global statistical properties of the cluster system. We find that NGC 5128 has a smaller cluster population than previously thought, with a steep projected radial distribution. We find the metallicity distribution for some 211 known globular clusters to be strongly bimodal with nearly equal numbers of clusters in each mode. We also present a list of 327 new cluster candidates not previously identified. D.G. gratefully acknowledges support from the Chilean Centro de Astrofisica FONDAP grant No. 15010003 and from NASA contract No. 1228235.

  8. CONSTRAINTS ON HELIUM ENHANCEMENT IN THE GLOBULAR CLUSTER M3 (NGC 5272): THE HORIZONTAL BRANCH TEST

    International Nuclear Information System (INIS)

    Catelan, M.; Valcarce, A. A. R.; Cortes, C.; Grundahl, F.; Sweigart, A. V.

    2009-01-01

    It has recently been suggested that the presence of multiple populations showing various amounts of helium enhancement is the rule, rather than the exception, among globular star clusters. An important prediction of this helium enhancement scenario is that the helium-enhanced blue horizontal branch (HB) stars should be brighter than the red HB stars which are not helium enhanced. In this Letter, we test this prediction in the case of the Galactic globular cluster M3 (NGC 5272), for which the helium-enhancement scenario predicts helium enhancements of ∼>0.02 in virtually all blue HB stars. Using high-precision Stroemgren photometry and spectroscopic gravities for blue HB stars, we find that any helium enhancement among most of the cluster's blue HB stars is very likely less than 0.01, thus ruling out the much higher helium enhancements that have been proposed in the literature.

  9. Antibody mapping and tissue localization of globular and cysteine-rich regions of perlecan domain III

    DEFF Research Database (Denmark)

    Couchman, J R; Ljubimov, A V; Sthanam, M

    1995-01-01

    Perlecan is the best-characterized basement membrane heparan sulfate proteoglycan. It has a large (approximately 400 KD) core protein consisting of five distinct domains. Domain III, a centrally located domain, contains three globular domains separated by cysteine-rich epidermal growth factor (EGF......)-like repeats. Domain III has overall homology with the N-terminus of the laminin alpha 1-chain. The aim of this study was to map a library of nine rat monoclonal antibodies (MAbs) against murine perlecan core protein, using recombinant whole Domain III and defined subdomains of Domain III. ELISA and Western...... blotting showed that six of the nine MAbs recognized Domain III of perlecan, three of them mapping to globular Subdomain IIIc, and the other three recognized epitopes within the cysteine-rich regions. All six MAbs stained every basement membrane of several mouse organs as well as some connective tissues...

  10. A simple model for electrical charge in globular macromolecules and linear polyelectrolytes in solution

    OpenAIRE

    Krishnan, M.

    2017-01-01

    We present a model for calculating the net and effective electrical charge of globular macromolecules and linear polyelectrolytes such as proteins and DNA, given the concentration of monovalent salt and pH in solution. The calculation is based on a numerical solution of the non-linear Poisson-Boltzmann equation using a finite element discretized continuum approach. The model simultaneously addresses the phenomena of charge regulation and renormalization, both of which underpin the electrostat...

  11. NGC 6273: Towards Defining A New Class of Galactic Globular Clusters?

    Science.gov (United States)

    Johnson, Christian I.; Rich, Robert Michael; Pilachowski, Catherine A.; Caldwell, Nelson; Mateo, Mario L.; Ira Bailey, John; Crane, Jeffrey D.

    2016-01-01

    A growing number of observations have found that several Galactic globular clusters exhibit abundance dispersions beyond the well-known light element (anti-)correlations. These clusters tend to be very massive, have >0.1 dex intrinsic metallicity dispersions, have complex sub-giant branch morphologies, and have correlated [Fe/H] and s-process element enhancements. Interestingly, nearly all of these clusters discovered so far have [Fe/H]~-1.7. In this context, we have examined the chemical composition of 18 red giant branch (RGB) stars in the massive, metal-poor Galactic bulge globular cluster NGC 6273 using high signal-to-noise, high resolution (R~27,000) spectra obtained with the Michigan/Magellan Fiber System (M2FS) and MSpec spectrograph mounted on the Magellan-Clay 6.5m telescope at Las Campanas Observatory. We find that the cluster exhibits a metallicity range from [Fe/H]=-1.80 to -1.30 and is composed of two dominant populations separated in [Fe/H] and [La/Fe] abundance. The increase in [La/Eu] as a function of [La/H] suggests that the increase in [La/Fe] with [Fe/H] is due to almost pure s-process enrichment. The most metal-rich star in our sample is not strongly La-enhanced, but is α-poor and may belong to a third "anomalous" stellar population. The two dominant populations exhibit the same [Na/Fe]-[Al/Fe] correlation found in other "normal" globular clusters. Therefore, NGC 6273 joins ω Centauri, M 22, M 2, and NGC 5286 as a possible new class of Galactic globular clusters.

  12. The SUMO project I. A survey of multiple populations in globular clusters

    Science.gov (United States)

    Monelli, M.; Milone, A. P.; Stetson, P. B.; Marino, A. F.; Cassisi, S.; del Pino Molina, A.; Salaris, M.; Aparicio, A.; Asplund, M.; Grundahl, F.; Piotto, G.; Weiss, A.; Carrera, R.; Cebrián, M.; Murabito, S.; Pietrinferni, A.; Sbordone, L.

    2013-05-01

    We present a general overview and the first results of the SUMO project (a SUrvey of Multiple pOpulations in Globular Clusters). The objective of this survey is the study of multiple stellar populations in the largest sample of globular clusters homogeneously analysed to date. To this aim we obtained high signal-to-noise (S/N > 50) photometry for main sequence stars with mass down to ˜0.5 M⊙ in a large sample of clusters using both archival and proprietary U, B, V and I data from ground-based telescopes. In this paper, we focus on the occurrence of multiple stellar populations in 23 clusters. We define a new photometric index, cU, B, I = (U - B) - (B - I), which turns out to be very effective for identifying multiple sequences along the red giant branch (RGB). We found that in the V-cU, B, I diagram all clusters presented in this paper show broadened or multimodal RGBs, with the presence of two or more components. We found a direct connection with the chemical properties of different sequences, which display different abundances of light elements (O, Na, C, N and Al). The cU, B, I index is also a powerful tool for identifying distinct sequences of stars along the horizontal branch and, for the first time in the case of NGC 104 (47 Tuc), along the asymptotic giant branch. Our results demonstrate that (i) the presence of more than two stellar populations is a common feature amongst globular clusters, as already highlighted in previous work; (ii) multiple sequences with different chemical contents can be easily identified by using standard Johnson photometry obtained with ground-based facilities; (iii) in the study of globular cluster multiple stellar populations the cU, B, I index is an alternative to spectroscopy, and has the advantage of larger statistics.

  13. AS1411 Aptamer-Anionic Linear Globular Dendrimer G2-Iohexol Selective Nano-Theranostics

    OpenAIRE

    Mohammadzadeh, Pardis; Cohan, Reza Ahangari; Ghoreishi, Seyedeh Masoumeh; Bitarafan-Rajabi, Ahmad; Ardestani, Mehdi Shafiee

    2017-01-01

    Molecular theranostics is of the utmost interest for diagnosis as well as treatment of different malignancies. In the present study, anionic linear globular dendrimer G2 is employed as a suitable carrier for delivery and AS1411 aptamer is exploited as the targeting agent to carry Iohexol specifically to the human breast cancer cells (MCF-7). Dendrimer G2 was prepared and conjugation of dendrimer and aptamer was carried out thereafter. Based on the data yielded by AFM, morphology of smooth and...

  14. BVRI CCD photometry of the metal-poor globular cluster M68 (NGC 4590)

    International Nuclear Information System (INIS)

    Alcaino, G.; Liller, W.; Alvarado, F.; Wenderoth, E.

    1990-01-01

    BVRI photometry of the low metallicity globular cluster M68 (NGC 4590) was obtained with a CCD camera and the 2.2-m ESO telescope. The resulting BV color-magnitude diagrams are compared with the observations of McClure et al. (1987). The observations are also compared with theoretical isochrones, yielding a cluster age of 13 Gyr with a likely external uncertainty of 2 or 3 Gyr. 25 refs

  15. Globular hepatic amyloid is highly sensitive and specific for LECT2 amyloidosis.

    Science.gov (United States)

    Chandan, Vishal S; Shah, Sejal S; Lam-Himlin, Dora M; Petris, Giovanni De; Mereuta, Oana M; Dogan, Ahmet; Torbenson, Michael S; Wu, Tsung-Teh

    2015-04-01

    Globular hepatic amyloid (GHA) is rare, and its clinical significance remains unclear. Recently, leukocyte chemotactic factor-associated amyloidosis (ALECT2) has been reported to involve the liver, showing a globular pattern. We reviewed 70 consecutive cases of hepatic amyloidosis to determine the prevalence and morphology of hepatic amyloid subtypes, especially ALECT2 and its association with GHA. Each case was reviewed for amyloid subtype (immunohistochemistry and/or mass spectrometry), its pattern (linear or globular), and distribution (vascular, perisinusoidal, or stromal). In addition, 24 cases of confirmed hepatic ALECT2 on mass spectrometry from our consultation files were also reviewed. LECT2 immunostaining was performed in 49 cases. Of the 70 cases, immunoglobulin light chain (AL) type was most common with 41 cases (59%), followed by transthyretin (ATTR) 15 cases (22%), 3 cases each of fibrinogen A (AFib) (4%), serum amyloid A (AA) (4%), and ALECT2 (4%), 2 cases of apolipoproteins (AApoA1) (3%), and 3 cases (4%) were unclassified. Three of our 70 cases (4%), with ALECT2, and all 24 cases (100%) of mass spectrometry-confirmed hepatic ALECT2 showed only GHA deposits in the hepatic sinusoids and portal tracts. Three (4%) other cases of AL type showed a focal globular pattern admixed with prominent linear amyloid. None of the other amyloid subtypes showed GHA. LECT2 immunostain was positive in all 27 cases (100%) of ALECT2 and negative in the other 22 non-ALECT2 cases (100%) (14 AL, 5 ATTR, 1 AA, 1 AFib, 1 AApoA1). Pure GHA is uncommon (4%) but is highly specific for ALECT2, and LECT2 immunostain is helpful in confirming this amyloid type.

  16. Detecting the effect of Globular Cluster impacts on the disk of the Milky Way

    OpenAIRE

    Putte, D. Vande; Cropper, Mark

    2008-01-01

    The crossing of the Galactic disk by a Globular Cluster could produce star formation due to gravitational focussing or compression of disk material. We report on simulations of the effect on disk material which reveal that the crossing can sometimes cause local gravitational focussing of disk material. We also present the salient points of a little-known paper by Levy (2000), that shows that strong compression can result from the shock wave generated by GC disk crossing. The main thrust of ou...

  17. Distribución en gran escala de los cúmulos globulares en Fornax

    Science.gov (United States)

    Ostrov, P. G.

    Para analizar los cúmulos globulares azules y rojos de NGC 1399 asociados con NGC 1399 en particular, o si los cúmulos azules representaban un sistema asociado con el cúmulo de Fornax en general, se obtuvieron imágenes CCD de gran formato con el telescopio de 4m del CTIO, en las bandas C y T1. Se describe el método empleado y lo encontrado.

  18. The pulsation mode and period-luminosity relationship of cool variables in globular clusters

    International Nuclear Information System (INIS)

    Whitelock, P.A.

    1986-01-01

    The period-luminosity-temperature relationship for globular cluster red and yellow variables is examined. The results suggest that the higher temperature, more metal-deficient cluster variables pulsate in the fundamental mode, while the lower temperature more metal-rich variables pulsate in the first overtone. On the assumption that this is correct, a relationship between fundamental period and bolometric magnitude is derived for cluster variables with observed periods of between 1 and 300 days. (author)

  19. Unified understanding of folding and binding mechanisms of globular and intrinsically disordered proteins.

    Science.gov (United States)

    Arai, Munehito

    2018-01-06

    Extensive experimental and theoretical studies have advanced our understanding of the mechanisms of folding and binding of globular proteins, and coupled folding and binding of intrinsically disordered proteins (IDPs). The forces responsible for conformational changes and binding are common in both proteins; however, these mechanisms have been separately discussed. Here, we attempt to integrate the mechanisms of coupled folding and binding of IDPs, folding of small and multi-subdomain proteins, folding of multimeric proteins, and ligand binding of globular proteins in terms of conformational selection and induced-fit mechanisms as well as the nucleation-condensation mechanism that is intermediate between them. Accumulating evidence has shown that both the rate of conformational change and apparent rate of binding between interacting elements can determine reaction mechanisms. Coupled folding and binding of IDPs occurs mainly by induced-fit because of the slow folding in the free form, while ligand binding of globular proteins occurs mainly by conformational selection because of rapid conformational change. Protein folding can be regarded as the binding of intramolecular segments accompanied by secondary structure formation. Multi-subdomain proteins fold mainly by the induced-fit (hydrophobic collapse) mechanism, as the connection of interacting segments enhances the binding (compaction) rate. Fewer hydrophobic residues in small proteins reduce the intramolecular binding rate, resulting in the nucleation-condensation mechanism. Thus, the folding and binding of globular proteins and IDPs obey the same general principle, suggesting that the coarse-grained, statistical mechanical model of protein folding is promising for a unified theoretical description of all mechanisms.

  20. Gravitational microlensing by low-mass objects in the globular cluster M22.

    Science.gov (United States)

    Sahu, K C; Casertano, S; Livio, M; Gilliland, R L; Panagia, N; Albrow, M D; Potter, M

    2001-06-28

    Gravitational microlensing offers a means of determining directly the masses of objects ranging from planets to stars, provided that the distances and motions of the lenses and sources can be determined. A globular cluster observed against the dense stellar field of the Galactic bulge presents ideal conditions for such observations because the probability of lensing is high and the distances and kinematics of the lenses and sources are well constrained. The abundance of low-mass objects in a globular cluster is of particular interest, because it may be representative of the very early stages of star formation in the Universe, and therefore indicative of the amount of dark baryonic matter in such clusters. Here we report a microlensing event associated with the globular cluster M22. We determine the mass of the lens to be 0.13(+0.03)(-0.02) solar masses. We have also detected six events that are unresolved in time. If these are also microlensing events, they imply that a non-negligible fraction of the cluster mass resides in the form of free-floating planetary-mass objects.

  1. Chemical Abundances of Red Giant Branch Stars in the Globular Clusters NGC 6333 and NGC 6366

    Science.gov (United States)

    Johnson, Christian I.; Rich, R. M.; Pilachowski, C. A.; Kunder, A. M.

    2013-01-01

    We present chemical abundances and radial velocities for >20 red giant branch (RGB) stars in the Galactic globular clusters NGC 6333 ([Fe/H]≈-1.8) and NGC 6366 ([Fe/H]≈-0.6). The results are based on moderate resolution (R=18,000), high signal-to-noise ratio (>100) spectra obtained with the Hydra multifiber positioner and bench spectrograph on the WIYN 3.5m telescope at Kitt Peak National Observatory. Both objects are likely associated with the Galactic bulge globular cluster system, and we therefore compare the cluster abundance patterns with those of nearby bulge field stars. Additionally, we investigate differences in the O-Na anticorrelation and neutron-capture element dispersion between the two clusters, and compare their abundance patterns with those of similar metallicity halo globular clusters. This material is based upon work supported by the National Science Foundation under award No. AST-1003201 to C.I.J. C.A.P. gratefully acknowledges support from the Daniel Kirkwood Research Fund at Indiana University. R.M.R. acknowledges support from NSF grant AST-0709479 and AST-121120995.

  2. Globular Cluster Variable Stars—Atlas and Coordinate Improvement using AAVSOnet Telescopes (Abstract)

    Science.gov (United States)

    Welch, D.; Henden, A.; Bell, T.; Suen, C.; Fare, I.; Sills, A.

    2015-12-01

    (Abstract only) The variable stars of globular clusters have played and continue to play a significant role in our understanding of certain classes of variable stars. Since all stars associated with a cluster have the same age, metallicity, distance and usually very similar (if not identical reddenings), such variables can produce uniquely powerful constraints on where certain types of pulsation behaviors are excited. Advanced amateur astronomers are increasingly well-positioned to provide long-term CCD monitoring of globular cluster variable star but are hampered by a long history of poor or inaccessible finder charts and coordinates. Many of variable-rich clusters have published photographic finder charts taken in relatively poor seeing with blue-sensitive photographic plates. While useful signal-to-noise ratios are relatively straightforward to achieve for RR Lyrae, Type 2 Cepheids, and red giant variables, correct identification remains a difficult issue—particularly when images are taken at V or longer wavelengths. We describe the project and report its progress using the OC61, TMO61, and SRO telescopes of AAVSOnet after the first year of image acquisition and demonstrate several of the data products being developed for globular cluster variables.

  3. No Evidence for Multiple Stellar Populations in the Low-mass Galactic Globular Cluster E 3

    Science.gov (United States)

    Salinas, Ricardo; Strader, Jay

    2015-08-01

    Multiple stellar populations are a widespread phenomenon among Galactic globular clusters. Even though the origin of the enriched material from which new generations of stars are produced remains unclear, it is likely that self-enrichment will be feasible only in clusters massive enough to retain this enriched material. We searched for multiple populations in the low mass (M˜ 1.4× {10}4 {M}⊙ ) globular cluster E3, analyzing SOAR/Goodman multi-object spectroscopy centered on the blue cyanogen (CN) absorption features of 23 red giant branch stars. We find that the CN abundance does not present the typical bimodal behavior seen in clusters hosting multistellar populations, but rather a unimodal distribution that indicates the presence of a genuine single stellar population, or a level of enrichment much lower than in clusters that show evidence for two populations from high-resolution spectroscopy. E3 would be the first bona fide Galactic old globular cluster where no sign of self-enrichment is found. Based on observations obtained at the Southern Astrophysical Research (SOAR) Telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the US National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  4. VARIABLE STARS IN LARGE MAGELLANIC CLOUD GLOBULAR CLUSTERS. II. NGC 1786

    Energy Technology Data Exchange (ETDEWEB)

    Kuehn, Charles A.; Smith, Horace A.; De Lee, Nathan [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Catelan, Marcio [Facultad de Fisica, Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Santiago (Chile); Pritzl, Barton J. [Department of Physics and Astronomy, University of Wisconsin Oskosh, Oshkosh, WI 54901 (United States); Borissova, Jura, E-mail: kuehn@physics.usyd.edu.au, E-mail: smith@pa.msu.edu, E-mail: nathan.delee@vanderbilt.edu, E-mail: mcatelan@astro.puc.cl, E-mail: pritzlb@uwosh.edu, E-mail: jura.borissova@uv.cl [Departamento de Fisica y Astronomia, Falcultad de Ciencias, Universidad de Valparaiso, Valparaiso (Chile)

    2012-12-01

    This is the second in a series of papers studying the variable stars in Large Magellanic Cloud globular clusters. The primary goal of this series is to study how RR Lyrae stars in Oosterhoff-intermediate systems compare to their counterparts in Oosterhoff I/II systems. In this paper, we present the results of our new time-series B-V photometric study of the globular cluster NGC 1786. A total of 65 variable stars were identified in our field of view. These variables include 53 RR Lyraes (27 RRab, 18 RRc, and 8 RRd), 3 classical Cepheids, 1 Type II Cepheid, 1 Anomalous Cepheid, 2 eclipsing binaries, 3 Delta Scuti/SX Phoenicis variables, and 2 variables of undetermined type. Photometric parameters for these variables are presented. We present physical properties for some of the RR Lyrae stars, derived from Fourier analysis of their light curves. We discuss several different indicators of Oosterhoff type which indicate that the Oosterhoff classification of NGC 1786 is not as clear cut as what is seen in most globular clusters.

  5. Evidence from stellar abundances for a large age difference between two globular clusters

    International Nuclear Information System (INIS)

    Dickens, R.J.; Croke, B.F.W.; Cannon, R.D.; Bell, R.A.

    1991-01-01

    The globular clusters NGC288 and NGC362 are central to recent claims of large age differences (∼3 Gyr) between globular clusters associated with our Galaxy. According to standard models for the formation of the Galaxy, the system of globular clusters formed during the dynamical collapse of the protogalactic cloud, a process which should have lasted no more than 1 Gyr. But the claimed age differences are derived from stellar evolution models using assumed CNO abundances, and uncertainty in the actual CNO abundances of about a factor of three could account for an apparent 2-Gyr age difference. We have accurately measured abundances in red giants in NGC288 and NGC362, and find that the Fe abundance and the sum of the C, N and O abundances are essentially the same in every star studied. By eliminating compositional differences and thus confirming the reality of the age difference, these results imply a cluster formation period that is hard to reconcile with the standard collapse model. (author)

  6. The correlation between the sizes of globular cluster systems and their host dark matter haloes

    Science.gov (United States)

    Hudson, Michael J.; Robison, Bailey

    2018-04-01

    The sizes of entire systems of globular clusters (GCs) depend on the formation and destruction histories of the GCs themselves, but also on the assembly, merger and accretion history of the dark matter (DM) haloes that they inhabit. Recent work has shown a linear relation between total mass of globular clusters in the globular cluster system and the mass of its host dark matter halo, calibrated from weak lensing. Here we extend this to GC system sizes, by studying the radial density profiles of GCs around galaxies in nearby galaxy groups. We find that radial density profiles of the GC systems are well fit with a de Vaucouleurs profile. Combining our results with those from the literature, we find tight relationship (˜0.2 dex scatter) between the effective radius of the GC system and the virial radius (or mass) of its host DM halo, for halos with masses greater than ˜1012M⊙. The steep non-linear dependence of this relationship (R_{{e, GCS}} ∝ R_{200}^{2.5 - 3} ∝ M_{200}^{0.8 - 1}) is currently not well understood, but is an important clue regarding the assembly history of DM haloes and of the GC systems that they host.

  7. Chemical analysis of eight giant stars of the globular cluster NGC 6366

    Science.gov (United States)

    Puls, Arthur A.; Brito, Alan Alves; Campos, Fabíola; Dias, Bruno; Barbuy, Beatriz

    2018-02-01

    The metal-rich Galactic globular cluster NGC 6366 is the fifth closest to the Sun. Despite its interest, it has received scarce attention, and little is known about its internal structure. Its kinematics suggests a link to the halo, but its metallicity indicates otherwise. We present a detailed chemical analysis of eight giant stars of NGC 6366, using high resolution and high quality spectra (R > 40 000, S/N > 60) obtained at the VLT (8.2 m) and CFHT (3.6 m) telescopes. We attempted to characterize its chemistry and to search for evidence of multiple stellar populations. The atmospheric parameters were derived using the method of excitation and ionization equilibrium of Fe I and Fe II lines and from those atmospheric parameters we calculated the abundances for other elements and found that none of the elements measured presents star-to-star variation greater than the uncertainties. We compared the derived abundances with those of other globular clusters and field stars available in the literature. We determined a mean [Fe/H] = -0.60 ± 0.03 for NGC 6366 and found some similarity of this object with M 71, another inner halo globular cluster. The Na-O anticorrelation extension is short and no star-to-star variation in Al is found. The presence of second generation stars is not evident in NGC 6366.

  8. The expected very-high-energy flux from a population of globular clusters

    Science.gov (United States)

    Venter, C.; Kopp, A.

    Given their old ages, globular clusters are expected to harbour many evolved stellar objects. Their high core densities enhance stellar encounter rates, also facilitating the formation of stellar end products. In particular, many millisecond pulsars are found in these clusters. Such a population of millisecond pulsars is expected to radiate several spectral components in the radio through gamma -ray waveband. We present ongoing work involving a refined spectral model that assumes millisecond pulsars as sources of relativistic particles to model the multi-wavelength emission properties of globular clusters. We apply the model to a population of globular clusters that have been observed by H.E.S.S. and use upper limits derived from stacking analyses to test the viability of this ``millisecond pulsar scenario''. We derive general expressions for the ensemble-averaged flux and its error stemming from the uncertainty in free model parameters. The errors exceed this calculated average flux value so that there are regions in parameter space for which the model predictions satisfy the H.E.S.S. upper limits. Improved constraints on single-cluster parameters are therefore needed to aid in discriminating between competing spectral models.

  9. VARIABLE STARS IN LARGE MAGELLANIC CLOUD GLOBULAR CLUSTERS. II. NGC 1786

    International Nuclear Information System (INIS)

    Kuehn, Charles A.; Smith, Horace A.; De Lee, Nathan; Catelan, Márcio; Pritzl, Barton J.; Borissova, Jura

    2012-01-01

    This is the second in a series of papers studying the variable stars in Large Magellanic Cloud globular clusters. The primary goal of this series is to study how RR Lyrae stars in Oosterhoff-intermediate systems compare to their counterparts in Oosterhoff I/II systems. In this paper, we present the results of our new time-series B–V photometric study of the globular cluster NGC 1786. A total of 65 variable stars were identified in our field of view. These variables include 53 RR Lyraes (27 RRab, 18 RRc, and 8 RRd), 3 classical Cepheids, 1 Type II Cepheid, 1 Anomalous Cepheid, 2 eclipsing binaries, 3 Delta Scuti/SX Phoenicis variables, and 2 variables of undetermined type. Photometric parameters for these variables are presented. We present physical properties for some of the RR Lyrae stars, derived from Fourier analysis of their light curves. We discuss several different indicators of Oosterhoff type which indicate that the Oosterhoff classification of NGC 1786 is not as clear cut as what is seen in most globular clusters.

  10. Study of the spray to globular transition in gas metal arc welding: a spectroscopic investigation

    International Nuclear Information System (INIS)

    Valensi, F; Pellerin, S; Castillon, Q; Zielinska, S; Boutaghane, A; Dzierzega, K; Pellerin, N; Briand, F

    2013-01-01

    The gas metal arc welding (GMAW) process is strongly influenced by the composition of the shielding gas. In particular, addition of CO 2 increases the threshold current for the transition from unstable globular to more stable spray transfer mode. We report on the diagnostics—using optical emission spectroscopy—of a GMAW plasma in pure argon and in mixtures of argon, CO 2 and N 2 while operated in spray and globular transfer modes. The spatially resolved plasma parameters are obtained by applying the Abel transformation to laterally integrated emission data. The Stark widths of some iron lines are used to determine both electron density and temperature, and line intensities yield relative contents of neutral and ionized iron to argon. Our experimental results indicate a temperature drop on the arc axis in the case of spray arc transfer. This drop reduces with addition of N 2 and disappears in globular transfer mode when CO 2 is added. Despite the temperature increase, the electron density decreases with CO 2 concentration. The highest concentration of iron is observed in the plasma column upper part (close to the anode) and for GMAW with CO 2 . Our results are compared with recently published works where the effect of non-homogeneous metal vapour concentration has been taken into account. (paper)

  11. Hydrophobicity diversity in globular and nonglobular proteins measured with the Gini index.

    Science.gov (United States)

    Carugo, Oliviero

    2017-12-01

    Amino acids and their properties are variably distributed in proteins and different compositions determine all protein features, ranging from solubility to stability and functionality. Gini index, a tool to estimate distribution uniformity, is widely used in macroeconomics and has numerous statistical applications. Here, Gini index is used to analyze the distribution of hydrophobicity in proteins and to compare hydrophobicity distribution in globular and intrinsically disordered proteins. Based on the analysis of carefully selected high-quality data sets of proteins extracted from the Protein Data Bank (http://www.rcsb.org) and from the DisProt database (http://www.disprot.org/), it is observed that hydrophobicity is distributed in a more diverse way in intrinsically disordered proteins than in folded and soluble globular proteins. This correlates with the observation that the amino acid composition deviates from the uniformity (estimate with the Shannon and the Gini-Simpson indices) more in intrinsically disordered proteins than in globular and soluble proteins. Although statistical tools tike the Gini index have received little attention in molecular biology, these results show that they allow one to estimate sequence diversity and that they are useful to delineate trends that can hardly be described, otherwise, in simple and concise ways. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  12. Chemical analysis of eight giant stars of the globular cluster NGC 6366

    Science.gov (United States)

    Puls, Arthur A.; Alves-Brito, Alan; Campos, Fabíola; Dias, Bruno; Barbuy, Beatriz

    2018-05-01

    The metal-rich Galactic globular cluster NGC 6366 is the fifth closest to the Sun. Despite its interest, it has received scarce attention, and little is known about its internal structure. Its kinematics suggests a link to the halo, but its metallicity indicates otherwise. We present a detailed chemical analysis of eight giant stars of NGC 6366, using high-resolution and high-quality spectra (R > 40 000, S/N > 60) obtained at the VLT (8.2 m) and CFHT (3.6 m) telescopes. We attempted to characterize its chemistry and to search for evidence of multiple stellar populations. The atmospheric parameters were derived using the method of excitation and ionization equilibrium of Fe I and Fe II lines and from those atmospheric parameters we calculated the abundances for other elements and found that none of the elements measured presents star-to-star variation greater than the uncertainties. We compared the derived abundances with those of other globular clusters and field stars available in the literature. We determined a mean [Fe/H] = -0.60 ± 0.03 for NGC 6366 and found some similarity of this object with M 71, another inner halo globular cluster. The Na-O anticorrelation extension is short and no star-to-star variation in Al is found. The presence of second generation stars is not evident in NGC 6366.

  13. Individual globular domains and domain unfolding visualized in overstretched titin molecules with atomic force microscopy.

    Directory of Open Access Journals (Sweden)

    Zsolt Mártonfalvi

    Full Text Available Titin is a giant elastomeric protein responsible for the generation of passive muscle force. Mechanical force unfolds titin's globular domains, but the exact structure of the overstretched titin molecule is not known. Here we analyzed, by using high-resolution atomic force microscopy, the structure of titin molecules overstretched with receding meniscus. The axial contour of the molecules was interrupted by topographical gaps with a mean width of 27.7 nm that corresponds well to the length of an unfolded globular (immunoglobulin and fibronectin domain. The wide gap-width distribution suggests, however, that additional mechanisms such as partial domain unfolding and the unfolding of neighboring domain multimers may also be present. In the folded regions we resolved globules with an average spacing of 5.9 nm, which is consistent with a titin chain composed globular domains with extended interdomain linker regions. Topographical analysis allowed us to allocate the most distal unfolded titin region to the kinase domain, suggesting that this domain systematically unfolds when the molecule is exposed to overstretching forces. The observations support the prediction that upon the action of stretching forces the N-terminal ß-sheet of the titin kinase unfolds, thus exposing the enzyme's ATP-binding site and hence contributing to the molecule's mechanosensory function.

  14. Classifying Returns as Extreme

    DEFF Research Database (Denmark)

    Christiansen, Charlotte

    2014-01-01

    I consider extreme returns for the stock and bond markets of 14 EU countries using two classification schemes: One, the univariate classification scheme from the previous literature that classifies extreme returns for each market separately, and two, a novel multivariate classification scheme...... that classifies extreme returns for several markets jointly. The new classification scheme holds about the same information as the old one, while demanding a shorter sample period. The new classification scheme is useful....

  15. Carbon and nitrogen abundances of stellar populations in the globular cluster M 2

    Science.gov (United States)

    Lardo, C.; Pancino, E.; Mucciarelli, A.; Milone, A. P.

    2012-12-01

    We present CH and CN index analysis and C and N abundance calculations based on the low-resolution blue spectra of red giant branch (RGB) stars in the Galactic globular cluster NGC 7089 (M 2). Our main goal is to investigate the C-N anticorrelation for this intermediate metallicity cluster. The data were collected with DOLORES, the multiobject, low-resolution facility at the Telescopio Nazionale Galileo. We first looked for CH and CN band strength variations and bimodalities in a sample of RGB stars with 17.5 ≤ V ≤ 14.5. Thus we derived C and N abundances under LTE assumption by comparing observed spectra with synthetic models from the spectral features at 4300 Å (G-band) and at ~3883 Å (CN). Spectroscopic data were coupled with UV photometry obtained during the spectroscopic run. We found a considerable star-to-star variation in both A(C) and A(N) at all luminosities for our sample of 35 targets. These abundances appear to be anticorrelated, with a hint of bimodality in the C content for stars with luminosities below the RBG bump (V ~ 15.7), while the range of variations in N abundances is very large and spans almost ~2 dex. We find additional C depletion as the stars evolve off the RGB bump, in fairly good agreement with theoretical predictions for metal-poor stars in the course of normal stellar evolution. We isolated two groups with N-rich and N-poor stars and found that N abundance variations correlate with the (U - V) color in the DOLORES color-magnitude diagram (CMD). The V, (U - V) CMD for this cluster shows an additional RGB sequence, located at the red of the main RGB and amounting to a small fraction of the total giant population. We identified two CH stars detected in previous studies in our U,V images. These stars, which are both cluster members, fall on this redder sequence, suggesting that the anomalous RGB should have a peculiar chemical pattern. Unfortunately, no additional spectra were obtained for stars in this previously unknown RGB branch

  16. Acute lower extremity ischaemia

    African Journals Online (AJOL)

    often defined as a sudden loss of perfusion to the lower extremity/extremities of less than 14 days' duration, ... Femoral arteries palpated Soft, tender. Hard, calcified. Dystrophic limb features Absent. Present. Cardiac abnormalities Present. Generally absent. Iliac/femoral bruits Absent. May be present. History of claudication ...

  17. Extreme summer temperatures in Western Europe

    Science.gov (United States)

    Simolo, C.; Brunetti, M.; Maugeri, M.; Nanni, T.

    2012-02-01

    We discuss the evolution of summer temperature extremes over Western Europe during 1961-2004 in the context of current climate warming. Using a parametric approach, we investigate the role of properties and changes in probability density functions of daily temperatures in modifying the frequency of severe, isolated events. In this perspective, the recent intensification of extremely warm events over Europe turns out to be well consistent with a pure, nonuniform shift of mean values, with no room for conjectures about increasing temperature variability.

  18. New cataclysmic variables and other exotic binaries in the globular cluster 47 Tucanae*

    Science.gov (United States)

    Rivera Sandoval, L. E.; van den Berg, M.; Heinke, C. O.; Cohn, H. N.; Lugger, P. M.; Anderson, J.; Cool, A. M.; Edmonds, P. D.; Wijnands, R.; Ivanova, N.; Grindlay, J. E.

    2018-04-01

    We present 22 new (+3 confirmed) cataclysmic variables (CVs) in the non-core-collapsed globular cluster 47 Tucanae (47 Tuc). The total number of CVs in the cluster is now 43, the largest sample in any globular cluster so far. For the identifications we used near-ultraviolet (NUV) and optical images from the Hubble Space Telescope, in combination with X-ray results from the Chandra X-ray Observatory. This allowed us to build the deepest NUV CV luminosity function of the cluster to date. We found that the CVs in 47 Tuc are more concentrated towards the cluster centre than the main-sequence turn-off stars. We compared our results to the CV populations of the core-collapsed globular clusters NGC 6397 and NGC 6752. We found that 47 Tuc has fewer bright CVs per unit mass than those two other clusters. That suggests that dynamical interactions in core-collapsed clusters play a major role creating new CVs. In 47 Tuc, the CV population is probably dominated by primordial and old dynamically formed systems. We estimated that the CVs in 47 Tuc have total masses of ˜1.4 M⊙. We also found that the X-ray luminosity function of the CVs in the three clusters is bimodal. Additionally, we discuss a possible double degenerate system and an intriguing/unclassified object. Finally, we present four systems that could be millisecond pulsar companions given their X-ray and NUV/optical colours. For one of them we present very strong evidence for being an ablated companion. The other three could be CO or He white dwarfs.

  19. The globular cluster systems of 54 Coma ultra-diffuse galaxies: statistical constraints from HST data

    Science.gov (United States)

    Amorisco, N. C.; Monachesi, A.; Agnello, A.; White, S. D. M.

    2018-04-01

    We use data from the HST Coma Cluster Treasury program to assess the richness of the globular cluster systems (GCSs) of 54 Coma ultra-diffuse galaxies (UDGs), 18 of which have a half-light radius exceeding 1.5 kpc. We use a hierarchical Bayesian method tested on a large number of mock data sets to account consistently for the high and spatially varying background counts in Coma. These include both background galaxies and intra-cluster globular clusters (ICGCs), which are disentangled from the population of member globular clusters (GCs) in a probabilistic fashion. We find no candidate for a GCS as rich as that of the Milky Way, our sample has GCSs typical of dwarf galaxies. For the standard relation between GCS richness and halo mass, 33 galaxies have a virial mass Mvir ≤ 1011 M⊙ at 90 per cent probability. Only three have Mvir > 1011 M⊙ with the same confidence. The mean colour and spread in colour of the UDG GCs are indistinguishable from those of the abundant population of ICGCs. The majority of UDGs in our sample are consistent with the relation between stellar mass and GC richness of `normal' dwarf galaxies. Nine systems, however, display GCSs that are richer by a factor of 3 or more (at 90 per cent probability). Six of these have sizes ≲1.4 kpc. Our results imply that the physical mechanisms responsible for the extended size of the UDGs and for the enhanced GC richness of some cluster dwarfs are at most weakly correlated.

  20. Moving in extreme environments

    DEFF Research Database (Denmark)

    Lucas, Samuel J E; Helge, Jørn W; Schütz, Uwe H W

    2016-01-01

    This review addresses human capacity for movement in the context of extreme loading and with it the combined effects of metabolic, biomechanical and gravitational stress on the human body. This topic encompasses extreme duration, as occurs in ultra-endurance competitions (e.g. adventure racing...... and transcontinental races) and expeditions (e.g. polar crossings), to the more gravitationally limited load carriage (e.g. in the military context). Juxtaposed to these circumstances is the extreme metabolic and mechanical unloading associated with space travel, prolonged bedrest and sedentary lifestyle, which may...

  1. Upper-extremity venography

    International Nuclear Information System (INIS)

    Yao, J.S.T.; Neiman, H.L.

    1985-01-01

    Symptomatically, patients often present with pain, swelling, and occasionally discoloration of the hand. In the presence of chronic swelling, it may be difficult to differentiate thrombosis from lymphedema, especially in patients who have undergone mastectomy. Noninvasive testing is helpful in differentiating between these two conditions, but venography offers definitive diagnosis. More importantly, venography demonstrates the site as well as the extent of the thrombotic process. Venography of the upper extremity was first introduced in 1931. Unlike the lower extremity, the use of this simple radiographic technique to evaluate venous problems of the upper extremity has received little attention

  2. [Preservation of crushed extremities].

    Science.gov (United States)

    Gonda, A; Tácsik, I; Juhász, J; Hepp, F

    1976-01-01

    For the conservation of crushed extremities all achievements of up-to-date traumatology are to be used. The impairement of the seriously crushed extremity displays a certain similarity to the polytraumatism involving the whole organism. This is to be taken into consideration in the surgical treatment. Conserving the vitality of the extremity deferred treatment and reconstructive operations at a later date become possible. As absolute rule must be in view that all cases are to be examined with the greatest care and individually, as regards the surgical treatment.

  3. Deep and accurate near-infrared photometry of the Galactic globular cluster omega Cen .

    Science.gov (United States)

    Calamida, A.; Bono, G.; Corsi, C. E.; Stetson, P. B.; Prada Moroni, P. G.; Degl'Innocenti, S.; Marchetti, E.; Amico, P.; Ferraro, I.; Iannicola, G.; Monelli, M.; Buonanno, R.; Caputo, F.; Dall'Ora, M.; Freyhammer, L. M.; Koester, D.; Nonino, M.; Piersimoni, A. M.; Pulone, L.; Romaniello, M.

    We present deep and accurate Near-Infrared (NIR) photometry of the Galactic Globular Cluster omega Cen . Data were collected using the Multi-Conjugate Adaptive Optics Demonstrator (MAD) mounted on the VLT (ESO). We combined the NIR photometry with optical space data collected with the Advanced Camera for Surveys (ACS) for the same region of the cluster. Our deep optical-NIR CMD indicates that the spread in age among the different stellar populations in omega Cen is at most of the order of 2 Gyr.

  4. On the radial distribution of white dwarfs in the Galactic globular cluster omega Cen

    Science.gov (United States)

    Calamida, A.; Corsi, C. E.; Bono, G.; Stetson, P. B.; Prada Moroni, P. G.; Degl'Innocenti, S.; Ferraro, I.; Iannicola, G.; Koester, D.; Pulone, L.; Monelli, M.; Amico, P.; Buonanno, R.; Freyhammer, L. M.; Marchetti, E.; Nonino, M.; Romaniello, M.

    We present deep and accurate photometry (F435W, F625W, F658N) of the Galactic Globular Cluster omega Cen collected with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST). We identified ≈ 6,500 white dwarf (WD) candidates and compared their radial distribution with that of Main Sequence (MS) stars. We found a mild evidence that young WDs ( 0.1 ≲ t ≲ 0.6 Gyr) are less centrally concentrated when compared to MS stars in the magnitude range 25 < F435W < 26.5.

  5. Globular star cluster systems around galaxies. II. The cases of spiral and dwarf galaxies

    International Nuclear Information System (INIS)

    Tadjibaev, I.U.; Nuritdinov, S.N.; Ganiev, J.M.

    2015-01-01

    Our compiled catalogue of globular cluster systems (GCS) which had studied in pervious part [1] is replenished now essentially as it are not sufficient the data to search for some empirical relationships between physical GCS parameters of the spiral and dwarf galaxies with a glance host galaxy characteristics. A number of empirical relationships for GCS of spiral and dwarf galaxies is first found. These results are differing essentially from analogous relationships for GCS of elliptical and lenticular galaxies which were found in [1]. It is also offered a possible new approach to the origin theory of the poor GCS which occupy a significant portion in our list of dwarf and spiral galaxies

  6. The gravitational wave emission from white dwarf interactions in globular clusters

    International Nuclear Information System (INIS)

    Loren-Aguilar, P; Garcia-Berro, E; Lobo, J A; Isern, J

    2009-01-01

    In the dense central regions of globular clusters close encounters of two white dwarfs are relatively frequent. The estimated frequency is one or more strong encounters per star in the lifetime of the cluster. Such encounters should be then potential sources of gravitational wave radiation. Thus, it is foreseeable that these collisions could be either individually detected by LISA or they could contribute significantly to the background noise of the detector. We compute the pattern of gravitational wave emission from these encounters for a sufficiently broad range of system parameters, namely the masses, the relative velocities and the distances of the two white dwarfs involved in the encounter.

  7. On the Variability of Blue Straggler Stars in the Globular Cluster M53

    Directory of Open Access Journals (Sweden)

    Soo-Chang Rey

    1998-06-01

    Full Text Available We present the results of a search for photometric variable blue straggler stars (BSSs in the globular cluster M53. Six of the 151 probable BSSs are identified as variable candidates based on the robust variable star detection technique of Welch & Stetson (1993. Most variable BSS candidates appear to occupy the instability strip in the color-magnitude diagram, and they appear to have visual light amplitudes of 0.2 mag - 0.3 mag. Further observations are required, however, to resolve the nature of variability between pulsating stars and eclipsing binaries for these variable BSS candidates.

  8. The Correlations between the Intrinsic Colors and Spectroscopic Metallicities of M31 Globular Clusters

    OpenAIRE

    Fan, Zhou; Ma, Jun; Zhou, Xu; Jiang, Zhaoji

    2010-01-01

    We present the correlations between the spectroscopic metallicities and ninety-three different intrinsic colors of M31 globular clusters, including seventy-eight BATC colors and fifteen SDSS and near infrared ugrizK colors. The BATC colors were derived from the archival images of thirteen filters (from c to p), which were taken by Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey with a 60/90 cm f/3 Schmidt telescope. The spectroscopic metallicities adopted in our work were from...

  9. Fermi Detection of a Luminous γ-Ray Pulsar in a Globular Cluster

    OpenAIRE

    Freire, C. C.P.; A. Abdo, A.; Ajello, Marco; Allafort, A.; Ballet, J.; Barbiellini, Guido; Bastieri, D.; Bechtol, K.; Bellazzini, R.; D. Blandford, R.; D. Bloom, E.; Bonamente, E.; W. Borgland, A.; Brigida, M.; Bruel, P.

    2011-01-01

    We report the Fermi Large Area Telescope detection of gamma-ray (>100 megaelectronvolts) pulsations from pulsar J1823-3021A in the globular cluster NGC 6624 with high significance (~7 sigma). Its gamma-ray luminosity L_gamma = (8.4 +/- 1.6) x10^34 ergs per second, is the highest observed for any millisecond pulsar (MSP) to date, and it accounts for most of the cluster emission. The non-detection of the cluster in the off-pulse phase implies that its contains < 32 gamma-ray MSPs, not ~100 as p...

  10. High Cadence Photometric Survey of Four Southern Hemisphere Milky Way Globular Clusters

    Science.gov (United States)

    Walker, Douglas Kyle; Albrow, Michael

    2015-08-01

    The Milky Way galaxy is surrounded by some 200 compact Globular Cluster (GCs) of stars, containing up to a million stars each. At 13 billion years of age, these globular clusters are almost as old as the universe itself and were born when the first generations of stars and galaxies formed. GCs are dynamical test beds for investigating and proving theories of stellar evolution. A key parameter to understanding the evolution of GCs is the binary fraction of stars contained within a GC. Binary stars are thought to be a controlling factor in globular cluster evolution and provide a unique tool to determine crucial information about a variety of stellar characteristics such as mass, radius and luminosity. In addition to containing binary stars, GCs also harbor a wide variety of variable stars such as RR Lyrae stars and other stellar exotica, such as blue stragglers, cataclysmic variables, and low-mass X-ray binaries. Recently, a potential new class of rapidly pulsating star, hydrogen-rich subdwarf (sdO) pulsators, has been discovered in the Omega Centauri GC. At present, these Hydrogen sdO pulsators have not been detected in any other GC or among the general field star population.This talk will discuss the use of Difference Imaging Algorithms (DIAs) applied to time-series photometry data from the 10m Southern African Large Telescope (SALT) to investigate short period low amplitude variable stars in the GCs: NGC 1904, NGC 2808, NGC 4833 and NGC 5139. We will present results of• Searching for new discoveries in pulsating stars, cataclysmic variables (a white dwarf star accreting material from its companion), BY Draconis stars (rapidly rotating dwarf stars spun up by a binary companion) and contact binary stars (rapidly rotating binaries that are beginning to coalesce)• Comparison analysis of variables across clusters in relation to cluster Main Sequence regions• Determining the fraction of binary stars in the identified GCsSpecific scientific questions that are

  11. ALMA reveals sunburn: CO dissociation around AGB stars in the globular cluster 47 Tucanae

    OpenAIRE

    McDonald, Iain; Zijlstra, Albert A.; Lagadec, Eric; Sloan, Gregory C.; Boyer, Martha L.; Matsuura, Mikako; Smith, Rowan J.; Smith, Christina L.; Yates, Jeremy A.; van Loon, Jacco Th.; Jones, Olivia C.; Ramstedt, Sofia; Avison, Adam; Justtanont, Kay; Olofsson, Hans

    2015-01-01

    Atacama Large Millimetre Array observations show a non-detection of carbon monoxide around the four most luminous asymptotic giant branch (AGB) stars in the globular cluster 47 Tucanae. Stellar evolution models and star counts show that the mass-loss rates from these stars should be similar to 1.2-3.5x10(-7) M-circle dot yr(-1). We would naively expect such stars to be detectable at this distance (4.5 kpc). By modelling the ultraviolet radiation field from post-AGB stars and white dwarfs in 4...

  12. Predictions of Gamma-ray Emission from Globular Cluster Millisecond Pulsars Above 100 MeV

    Science.gov (United States)

    Venter, C.; de Jaker, O.C.; Clapson, A.C.

    2009-01-01

    The recent Fermi detection of the globular cluster (GC) 47 Tucanae highlighted the importance of modeling collective gamma-ray emission of millisecond pulsars (MSPs) in GCs. Steady flux from such populations is also expected in the very high energy (VHE) domain covered by ground-based Cherenkov telescopes. We present pulsed curvature radiation (CR) as well as unpulsed inverse Compton (IC) calculations for an ensemble of MSPs in the GCs 47 Tucanae and Terzan 5. We demonstrate that the CR from these GCs should be easily detectable for Fermi, while constraints on the total number of MSps and the nebular B-field may be derived using the IC flux components.

  13. The "Globularization Hypothesis" of the Language-ready Brain as a Developmental Frame for Prosodic Bootstrapping Theories of Language Acquisition.

    Science.gov (United States)

    Irurtzun, Aritz

    2015-01-01

    In recent research (Boeckx and Benítez-Burraco, 2014a,b) have advanced the hypothesis that our species-specific language-ready brain should be understood as the outcome of developmental changes that occurred in our species after the split from Neanderthals-Denisovans, which resulted in a more globular braincase configuration in comparison to our closest relatives, who had elongated endocasts. According to these authors, the development of a globular brain is an essential ingredient for the language faculty and in particular, it is the centrality occupied by the thalamus in a globular brain that allows its modulatory or regulatory role, essential for syntactico-semantic computations. Their hypothesis is that the syntactico-semantic capacities arise in humans as a consequence of a process of globularization, which significantly takes place postnatally (cf. Neubauer et al., 2010). In this paper, I show that Boeckx and Benítez-Burraco's hypothesis makes an interesting developmental prediction regarding the path of language acquisition: it teases apart the onset of phonological acquisition and the onset of syntactic acquisition (the latter starting significantly later, after globularization). I argue that this hypothesis provides a developmental rationale for the prosodic bootstrapping hypothesis of language acquisition (cf. i.a. Gleitman and Wanner, 1982; Mehler et al., 1988, et seq.; Gervain and Werker, 2013), which claim that prosodic cues are employed for syntactic parsing. The literature converges in the observation that a large amount of such prosodic cues (in particular, rhythmic cues) are already acquired before the completion of the globularization phase, which paves the way for the premises of the prosodic bootstrapping hypothesis, allowing babies to have a rich knowledge of the prosody of their target language before they can start parsing the primary linguistic data syntactically.

  14. The globularization hypothesis of the language-ready brain as a developmental frame for prosodic bootstrapping theories of language acquisition

    Directory of Open Access Journals (Sweden)

    Aritz eIrurtzun

    2015-12-01

    Full Text Available In recent research Boeckx & Benítez-Burraco (2014a,b have advanced the hypothesis that our species-specific language-ready brain should be understood as the outcome of developmental changes that occurred in our species after the split from Neanderthals-Denisovans, which resulted in a more globular braincase configuration in comparison to our closest relatives, who had elongated endocasts. According to these authors, the development of a globular brain is an essential ingredient for the language faculty and in particular, it is the centrality occupied by the thalamus in a globular brain that allows its modulatory or regulatory role, essential for syntactico-semantic computations. Their hypothesis is that the syntactico-semantic capacities arise in humans as a consequence of a process of globularization, which significantly takes place postnatally (cf. Neubauer et al. (2010. In this paper, I show that Boeckx & Benítez-Burraco’s hypothesis makes an interesting developmental prediction regarding the path of language acquisition: it teases apart the onset of phonological acquisition and the onset of syntactic acquisition (the latter starting significantly later, after globularization. I argue that this hypothesis provides a developmental rationale for the prosodic bootstrapping hypothesis of language acquisition (cf. i.a. Gleitman & Wanner (1982; Mehler et al. (1988, et seq.; Gervain & Werker (2013, which claim that prosodic cues are employed for syntactic parsing. The literature converges in the observation that a large amount of such prosodic cues (in particular, rhythmic cues are already acquired before the completion of the globularization phase, which paves the way for the premises of prosodic bootstrapping hypothesis, allowing babies to have a rich knowledge of the prosody of their target language before they can start parsing the primary linguistic data syntactically.

  15. Ciliates in extreme environments.

    Science.gov (United States)

    Hu, Xiaozhong

    2014-01-01

    As eukaryotic microbial life, ciliated protozoan may be found actively growing in some extreme condition where there is a sufficient energy source to sustain it because they are exceedingly adaptable and not notably less adaptable than the prokaryotes. However, a crucial problem in the study of ciliates in extreme environments is the lack of reliable cultivation techniques. To our knowledge, only a tiny fraction of ciliates can be cultured in the laboratory, even for a very limited period, which can partly explain the paucity of our understanding about ciliates diversity in various extremes although the interest in the biodiversity of extremophiles increased significantly during the past three decades. This mini-review aims to compile the knowledge of several groups of free-living ciliates that can be microscopically observed in extreme environmental samples, although most habitats have not been sufficiently well explored for sound generalizations. © 2014 The Author(s) Journal of Eukaryotic Microbiology © 2014 International Society of Protistologists.

  16. Synthetic horizontal branch models for globular clusters - the luminosity of the horizontal branch and the Oosterhoff effect

    International Nuclear Information System (INIS)

    Lee, Y.W.; Demarque, P.; Zinn, R.

    1987-01-01

    The variation of horizontal-branch (HB) luminosities with metal abundances is analyzed on the basis of HB models synthesized from theoretical HB evolutionary tracks. The focus is on the Oosterhoff effect, as related to period shifts in globular-cluster RR Lyr variables. The construction of the models and the Oosterhoff period groups is explained in detail, and the implications for globular-cluster ages are considered. The ratio of Delta M(bol) (RR) to Delta Fe/H for the HB is calculated as 0.24, slightly steeper than that found by Sandage (1981 and 1982). 35 references

  17. Effects of main-sequence mass loss on the turnoff ages of globular clusters

    International Nuclear Information System (INIS)

    Guzik, J.A.

    1989-01-01

    Willson, Bowen, and Struck-Marcell have proposed that globular cluster main-sequence turnoff ages can be reconciled with the lower ages of the Galaxy and universe deduced from other methods by incorporating an epoch of early main-sequence mass-loss by stars of spectral types A through early-F. The proposed mass loss is pulsation-driven, and facilitated by rapid rotation. This paper presents stellar evolution calculations of Pop. II (Z = 0.001) mass-losing stars of initial mass 0.8 to 1.6 M circle dot , with exponentially-decreasing mass loss rates of e-folding times 0.5 to 2.0 Gyr, evolving to a final mass of 0.7 M circle dot . The calculations indicate that a globular cluster with apparent turnoff age 18 Gyr could have an actual age as low as ∼12 Gyr. Observational implications that may help to verify the hypothesis, e.g. low C/N abundance ratios among red giants following first dredge-up, blue stragglers, red giant deficiencies, and signatures in cluster mass/luminosity functions, are also discussed.25 refs., 4 figs., 3 tabs

  18. The Hot Stellar Content and HB morphology of the massive globular cluster G1

    Science.gov (United States)

    Rich, R.

    2010-09-01

    We propose to obtain deep WFC3 imagery of the Local Group's most luminous globular cluster, G1. Our primary aim is to define the hot stellar content and the extent of what appears to be a multimodal horizontal branch, analogous to those known in Omega Cen and NGC 2808. G1 is 40 kpc distant in the M31, and it would have been highly unlikely that collision with a giant molecular clould would be responsible for the complex populations which must therefore be the result of self-enrichment. We will obtain data very similar to those obtained for the known Galactic multimodal globular clusters NGC 6388 and 6441, and compare the stellar distribution on the horizontal branch with models. We can constrain the fraction of helium-enriched stars, if present, and search for supra-horizontal branch and other anomalous hot, evolved, stars. Parallel ACS observations will be the deepest ever obtained in the adjacnt field to G1, and will help to constrain whether G1 was the nucleus of a now disrupted galaxy.

  19. Chemical Abundances of Red Giant Branch Stars in the Globular Cluster NGC 288

    Science.gov (United States)

    Hsyu, Tiffany; Johnson, C. I.; Pilachowski, C. A.; Lee, Y.; Rich, R. M.

    2013-01-01

    We present chemical abundances and radial velocities for ~30 red giant branch (RGB) stars in the globular cluster NGC 288. The results are based on moderate resolution (R≈18,000) and moderate signal-to-noise ratio 50-75) obtained with the Hydra multi-object spectrograph on the Blanco 4m telescope. NGC 288 has been shown to exhibit two separate RGBs and we investigate possible differences in metallicity and/or light element abundances between stars on each branch. We present a new filter tracing for the CTIO Calcium HK narrow band filter and explore its effects on previous globular cluster color-magnitude diagrams. We also compare the light element abundance patterns of NGC 288 to those of other similar metallicity halo clusters. This material is based upon work supported by the National Science Foundation under award No.AST-1003201 to C.I.J. C.A.P. gratefully acknowledges support from the Daniel Kirkwood Research Fund at Indiana University. R.M.R. acknowledges support from NSF grants AST-0709479 and AST-121120995.

  20. Comparison of experimental and theoretical data on hydrogen-deuterium exchange for ten globular proteins.

    Science.gov (United States)

    Suvorina, M Yu; Surin, A K; Dovidchenko, N V; Lobanov, M Yu; Galzitskaya, O V

    2012-06-01

    The number of protons available for hydrogen-deuterium exchange was predicted for ten globular proteins using a method described elsewhere by the authors. The average number of protons replaced by deuterium was also determined by mass spectrometry of the intact proteins in their native conformations. Based on these data, we find that two models proposed earlier agree with each other in estimation of the number of protons replaced by deuterium. Using a model with a probability scale for hydrogen bond formation, we estimated a number of protons replaced by deuterium that is close to the experimental data for long-term incubation in D(2)O (24 h). Using a model based on estimations with a scale of the expected number of contacts in globular proteins there is better agreement with the experimental data obtained for a short period of incubation in D(2)O (15 min). Therefore, the former model determines weakly fluctuating parts of a protein that are in contact with solvent only for a small fraction of the time. The latter model (based on the scale of expected number of contacts) predicts either flexible parts of a protein chain exposed to interactions with solvent or disordered parts of the protein.

  1. Effects of main-sequence mass loss on the turnoff ages of globular clusters

    Energy Technology Data Exchange (ETDEWEB)

    Guzik, J.A.

    1989-01-01

    Willson, Bowen, and Struck-Marcell have proposed that globular cluster main-sequence turnoff ages can be reconciled with the lower ages of the Galaxy and universe deduced from other methods by incorporating an epoch of early main-sequence mass-loss by stars of spectral types A through early-F. The proposed mass loss is pulsation-driven, and facilitated by rapid rotation. This paper presents stellar evolution calculations of Pop. II (Z = 0.001) mass-losing stars of initial mass 0.8 to 1.6 M/sub /circle dot//, with exponentially-decreasing mass loss rates of e-folding times 0.5 to 2.0 Gyr, evolving to a final mass of 0.7 M/sub /circle dot//. The calculations indicate that a globular cluster with apparent turnoff age 18 Gyr could have an actual age as low as /approximately/12 Gyr. Observational implications that may help to verify the hypothesis, e.g. low C/N abundance ratios among red giants following first dredge-up, blue stragglers, red giant deficiencies, and signatures in cluster mass/luminosity functions, are also discussed.25 refs., 4 figs., 3 tabs.

  2. Constraints on helium enhancement in the globular cluster M4 (NGC 6121): The horizontal branch test

    International Nuclear Information System (INIS)

    Valcarce, A. A. R.; De Medeiros, J. R.; Catelan, M.; Alonso-García, J.; Cortés, C.

    2014-01-01

    Recent pieces of evidence have revealed that most, and possibly all, globular star clusters are composed of groups of stars that formed in multiple episodes with different chemical compositions. In this sense, it has also been argued that variations in the initial helium abundance (Y) from one population to the next are also the rule, rather than the exception. In the case of the metal-intermediate globular cluster M4 (NGC 6121), recent high-resolution spectroscopic observations of blue horizontal branch (HB) stars (i.e., HB stars hotter than the RR Lyrae instability strip) suggest that a large fraction of blue HB stars are second-generation stars formed with high helium abundances. In this paper, we test this scenario by using recent photometric and spectroscopic data together with theoretical evolutionary computations for different Y values. Comparing the photometric data with the theoretically derived color-magnitude diagrams, we find that the bulk of the blue HB stars in M4 have ΔY ≲ 0.01 with respect to the cluster's red HB stars (i.e., HB stars cooler than the RR Lyrae strip)—a result which is corroborated by comparison with spectroscopically derived gravities and temperatures, which also favor little He enhancement. However, the possible existence of a minority population on the blue HB of the cluster with a significant He enhancement level is also discussed.

  3. The globular cluster NGC 7492 and the Sagittarius tidal stream: together but unmixed

    Science.gov (United States)

    Carballo-Bello, J. A.; Corral-Santana, J. M.; Catelan, M.; Martínez-Delgado, D.; Muñoz, R. R.; Sollima, A.; Navarrete, C.; Duffau, S.; Côté, P.; Mora, M. D.

    2018-03-01

    We have derived from VIMOS spectroscopy the radial velocities for a sample of 71 stars selected from CFHT/Megacam photometry around the Galactic globular cluster NGC 7492. In the resulting velocity distribution, it is possible to distinguish two relevant non-Galactic kinematic components along the same line of sight: a group of stars at 〈vr〉 ˜ 125 km s-1 which is compatible with the velocity of the old leading arm of the Sagittarius tidal stream, and a larger number of objects at 〈vr〉 ˜ -110 km s-1 that might be identified as members of the trailing wrap of the same stream. The systemic velocity of NGC 7492 set at vr ˜ -177 km s-1 differs significantly from that of both components, thus our results confirm that this cluster is not one of the globular clusters deposited by the Sagittarius dwarf spheroidal in the Galactic halo, even if it is immersed in the stream. A group of stars with 〈vr〉 ˜ - 180 km s-1 might be comprised of cluster members along one of the tidal tails of NGC 7492.

  4. GLOBULAR CLUSTER SYSTEMS IN BRIGHTEST CLUSTER GALAXIES: A NEAR-UNIVERSAL LUMINOSITY FUNCTION?

    Energy Technology Data Exchange (ETDEWEB)

    Harris, William E.; O' Halloran, Heather; Cockcroft, Robert, E-mail: harris@physics.mcmaster.ca, E-mail: ohallohm@mcmaster.ca, E-mail: cockcroft@physics.mcmaster.ca [Department of Physics and Astronomy, McMaster University, Hamilton, ON (Canada); and others

    2014-12-20

    We present the first results from our Hubble Space Telescope brightest cluster galaxy (BCG) survey of seven central supergiant cluster galaxies and their globular cluster (GC) systems. We measure a total of 48,000 GCs in all seven galaxies, representing the largest single GC database. We find that a log-normal shape accurately matches the observed the luminosity function (LF) of the GCs down to the globular cluster luminosity function turnover point, which is near our photometric limit. In addition, the LF has a virtually identical shape in all seven galaxies. Our data underscore the similarity in the formation mechanism of massive star clusters in diverse galactic environments. At the highest luminosities (L ≳ 10{sup 7} L {sub ☉}), we find small numbers of ''superluminous'' objects in five of the galaxies; their luminosity and color ranges are at least partly consistent with those of ultra-compact dwarfs. Last, we find preliminary evidence that in the outer halo (R ≳ 20 kpc), the LF turnover point shows a weak dependence on projected distance, scaling as L {sub 0} ∼ R {sup –0.2}, while the LF dispersion remains nearly constant.

  5. Movimiento regular y caótico en cúmulos globulares

    Science.gov (United States)

    Carpintero, D. D.; Muzzio, J. C.; Wachlin, F. C.

    Los cúmulos globulares exhiben diferentes grados de elipticidad y se mueven en el campo gravitatorio de la galaxia a la que pertenecen. Las órbitas de sus estrellas no necesitan, por ello, conservar la energía ni el momento angular, y resulta probable la presencia de movimientos caóticos. Como paso preliminar de una investigación más extensa, presentamos aquí los resultados de un estudio de órbitas estelares en un cúmulo globular levemente triaxial que describe una órbita circular dentro de una galaxia. Las órbitas se investigan utilizando dos métodos: 1) La clasificación por frecuencias de D.D. Carpintero y L.A. Aguilar (1998, MNRAS, en prensa), y 2) Los exponentes de Lyapunov (subrutina LIAMAG, gentilmente suministrada por D. Pfenniger). Utilizando diversos espacios de condiciones iniciales, investigamos las familias de órbitas de las estrellas del cúmulo. Confirmamos la presencia de órbitas caóticas, particularmente en las zonas externas del cúmulo, y discutimos su importancia para la estructura del cúmulo.

  6. Constraints on helium enhancement in the globular cluster M4 (NGC 6121): The horizontal branch test

    Energy Technology Data Exchange (ETDEWEB)

    Valcarce, A. A. R.; De Medeiros, J. R. [Universidade Federal do Rio Grande do Norte, Departamento de Física, 59072-970 Natal, RN (Brazil); Catelan, M. [Pontificia Universidad Católica de Chile, Centro de Astroingeniería, Av. Vicuña Mackena 4860, 782-0436 Macul, Santiago (Chile); Alonso-García, J. [Pontificia Universidad Católica de Chile, Instituto de Astrofísica, Facultad de Física, Av. Vicuña Mackena 4860, 782-0436 Macul, Santiago (Chile); Cortés, C. [Universidad Metropolitana de Ciencias de la Educación, Facultad de Ciencias Básicas, Departamento de Física, Av. José Pedro Alessandri 774, Santiago (Chile)

    2014-02-20

    Recent pieces of evidence have revealed that most, and possibly all, globular star clusters are composed of groups of stars that formed in multiple episodes with different chemical compositions. In this sense, it has also been argued that variations in the initial helium abundance (Y) from one population to the next are also the rule, rather than the exception. In the case of the metal-intermediate globular cluster M4 (NGC 6121), recent high-resolution spectroscopic observations of blue horizontal branch (HB) stars (i.e., HB stars hotter than the RR Lyrae instability strip) suggest that a large fraction of blue HB stars are second-generation stars formed with high helium abundances. In this paper, we test this scenario by using recent photometric and spectroscopic data together with theoretical evolutionary computations for different Y values. Comparing the photometric data with the theoretically derived color-magnitude diagrams, we find that the bulk of the blue HB stars in M4 have ΔY ≲ 0.01 with respect to the cluster's red HB stars (i.e., HB stars cooler than the RR Lyrae strip)—a result which is corroborated by comparison with spectroscopically derived gravities and temperatures, which also favor little He enhancement. However, the possible existence of a minority population on the blue HB of the cluster with a significant He enhancement level is also discussed.

  7. Extreme Programming: Maestro Style

    Science.gov (United States)

    Norris, Jeffrey; Fox, Jason; Rabe, Kenneth; Shu, I-Hsiang; Powell, Mark

    2009-01-01

    "Extreme Programming: Maestro Style" is the name of a computer programming methodology that has evolved as a custom version of a methodology, called extreme programming that has been practiced in the software industry since the late 1990s. The name of this version reflects its origin in the work of the Maestro team at NASA's Jet Propulsion Laboratory that develops software for Mars exploration missions. Extreme programming is oriented toward agile development of software resting on values of simplicity, communication, testing, and aggressiveness. Extreme programming involves use of methods of rapidly building and disseminating institutional knowledge among members of a computer-programming team to give all the members a shared view that matches the view of the customers for whom the software system is to be developed. Extreme programming includes frequent planning by programmers in collaboration with customers, continually examining and rewriting code in striving for the simplest workable software designs, a system metaphor (basically, an abstraction of the system that provides easy-to-remember software-naming conventions and insight into the architecture of the system), programmers working in pairs, adherence to a set of coding standards, collaboration of customers and programmers, frequent verbal communication, frequent releases of software in small increments of development, repeated testing of the developmental software by both programmers and customers, and continuous interaction between the team and the customers. The environment in which the Maestro team works requires the team to quickly adapt to changing needs of its customers. In addition, the team cannot afford to accept unnecessary development risk. Extreme programming enables the Maestro team to remain agile and provide high-quality software and service to its customers. However, several factors in the Maestro environment have made it necessary to modify some of the conventional extreme

  8. Isolated Coccygeal Tuberculosis

    OpenAIRE

    Kim, Do Un; Kim, Seok Won; Ju, Chang IL

    2012-01-01

    Isolated tuberculosis of the coccyx is extremely rare. A 35-year-old man presented with a 3-month history of coccygeal and gluteal pain. Computed tomography and magnetic resonance imaging revealed osseous destruction and a large enhancing mass involving the coccyx with anterior and posterior extension. Pathologic examination of the surgical specimen revealed necrosis, chronic granulomatous inflammation, and multinucleated giant cells consistent with tuberculosis. This case highlights the impo...

  9. Gene adaptation to extreme environments

    International Nuclear Information System (INIS)

    Marlaire, P.; Rodriguez, V.; Kerner, N.

    2005-01-01

    Full text: This work is oriented to the study of gene adaptation to extreme conditions, such as the hydrothermal system located in Copahue, Neuquen, Argentina. The organisms living there develop under two pressure selection conditions: the high temperature of thermal water and the strong impact of ultraviolet (UV) radiation. Several microorganisms found in this region were isolated and different colonies resistant to UV radiation were selected, a Geobacillus thermoleovorans strain identified through 16S RNA sequence, being the most remarkable. A gene library was prepared out of this strain with UV sensitive bacteria BH200 (uvrA::Tn10). A number of clones were isolated by means of UV selection, the most outstanding being a gene carrier able to codify for the guanosine monophosphate synthetase enzyme (GMPs). The suitability of said enzyme was proved by means of additional assays performed on ght 1 bacteria (guaA26::Tn 10) which lacked the enzyme. A transcript of 1100 pb was detected through Northern Blot. The result was consistent with that obtained for the mapping of the starting transcription site. The cloned GMPs produces an increase in growth speed and a greater biomass in BH200 bacteria. (author)

  10. THE ACS SURVEY OF GALACTIC GLOBULAR CLUSTERS. XI. THE THREE-DIMENSIONAL ORIENTATION OF THE SAGITTARIUS DWARF SPHEROIDAL GALAXY AND ITS GLOBULAR CLUSTERS

    International Nuclear Information System (INIS)

    Siegel, Michael H.; Majewski, Steven R.; Law, David R.

    2011-01-01

    We use observations from the Hubble Space Telescope Advanced Camera for Surveys (HST/ACS) study of Galactic globular clusters to investigate the spatial distribution of the inner regions of the disrupting Sagittarius dwarf spheroidal galaxy (Sgr). We combine previously published analyses of four Sgr member clusters located near or in the Sgr core (M54, Arp 2, Terzan 7, and Terzan 8) with a new analysis of diffuse Sgr material identified in the background of five low-latitude Galactic bulge clusters (NGC 6624, 6637, 6652, 6681, and 6809) observed as part of the ACS survey. By comparing the bulge cluster color-magnitude diagrams to our previous analysis of the M54/Sgr core, we estimate distances to these background features. The combined data from four Sgr member clusters and five Sgr background features provide nine independent measures of the Sgr distance and, as a group, provide uniformly measured and calibrated probes of different parts of the inner regions of Sgr spanning 20° over the face of the disrupting dwarf. This allows us, for the first time, to constrain the three-dimensional orientation of Sgr's disrupting core and globular cluster system and compare that orientation to the predictions of an N-body model of tidal disruption. The density and distance of Sgr debris are consistent with models that favor a relatively high Sgr core mass and a slightly greater distance (28-30 kpc, with a mean of 29.4 kpc). Our analysis also suggests that M54 is in the foreground of Sgr by ∼2 kpc, projected on the center of the Sgr dSph. While this would imply a remarkable alignment of the cluster and the Sgr nucleus along the line of sight, we cannot identify any systematic effect in our analysis that would falsely create the measured 2 kpc separation. Finally, we find that the cluster Terzan 7 has the most discrepant distance (25 kpc) among the four Sgr core clusters, which may suggest a different dynamical history than the other Sgr core clusters.

  11. Extreme meteorological conditions

    International Nuclear Information System (INIS)

    Altinger de Schwarzkopf, M.L.

    1983-01-01

    Different meteorological variables which may reach significant extreme values, such as the windspeed and, in particular, its occurrence through tornadoes and hurricanes that necesarily incide and wich must be taken into account at the time of nuclear power plants' installation, are analyzed. For this kind of study, it is necessary to determine the basic phenomenum of design. Two criteria are applied to define the basic values of design for extreme meteorological variables. The first one determines the expected extreme value: it is obtained from analyzing the recurence of the phenomenum in a convened period of time, wich may be generally of 50 years. The second one determines the extreme value of low probability, taking into account the nuclear power plant's operating life -f.ex. 25 years- and considering, during said lapse, the occurrence probabilities of extreme meteorological phenomena. The values may be determined either by the deterministic method, which is based on the acknowledgement of the fundamental physical characteristics of the phenomena or by the probabilistic method, that aims to the analysis of historical statistical data. Brief comments are made on the subject in relation to the Argentine Republic area. (R.J.S.) [es

  12. Statistics of Extremes

    KAUST Repository

    Davison, Anthony C.

    2015-04-10

    Statistics of extremes concerns inference for rare events. Often the events have never yet been observed, and their probabilities must therefore be estimated by extrapolation of tail models fitted to available data. Because data concerning the event of interest may be very limited, efficient methods of inference play an important role. This article reviews this domain, emphasizing current research topics. We first sketch the classical theory of extremes for maxima and threshold exceedances of stationary series. We then review multivariate theory, distinguishing asymptotic independence and dependence models, followed by a description of models for spatial and spatiotemporal extreme events. Finally, we discuss inference and describe two applications. Animations illustrate some of the main ideas. © 2015 by Annual Reviews. All rights reserved.

  13. Extremely deformable structures

    CERN Document Server

    2015-01-01

    Recently, a new research stimulus has derived from the observation that soft structures, such as biological systems, but also rubber and gel, may work in a post critical regime, where elastic elements are subject to extreme deformations, though still exhibiting excellent mechanical performances. This is the realm of ‘extreme mechanics’, to which this book is addressed. The possibility of exploiting highly deformable structures opens new and unexpected technological possibilities. In particular, the challenge is the design of deformable and bi-stable mechanisms which can reach superior mechanical performances and can have a strong impact on several high-tech applications, including stretchable electronics, nanotube serpentines, deployable structures for aerospace engineering, cable deployment in the ocean, but also sensors and flexible actuators and vibration absorbers. Readers are introduced to a variety of interrelated topics involving the mechanics of extremely deformable structures, with emphasis on ...

  14. Acclimatization to extreme heat

    Science.gov (United States)

    Warner, M. E.; Ganguly, A. R.; Bhatia, U.

    2017-12-01

    Heat extremes throughout the globe, as well as in the United States, are expected to increase. These heat extremes have been shown to impact human health, resulting in some of the highest levels of lives lost as compared with similar natural disasters. But in order to inform decision makers and best understand future mortality and morbidity, adaptation and mitigation must be considered. Defined as the ability for individuals or society to change behavior and/or adapt physiologically, acclimatization encompasses the gradual adaptation that occurs over time. Therefore, this research aims to account for acclimatization to extreme heat by using a hybrid methodology that incorporates future air conditioning use and installation patterns with future temperature-related time series data. While previous studies have not accounted for energy usage patterns and market saturation scenarios, we integrate such factors to compare the impact of air conditioning as a tool for acclimatization, with a particular emphasis on mortality within vulnerable communities.

  15. Extremal graph theory

    CERN Document Server

    Bollobas, Bela

    2004-01-01

    The ever-expanding field of extremal graph theory encompasses a diverse array of problem-solving methods, including applications to economics, computer science, and optimization theory. This volume, based on a series of lectures delivered to graduate students at the University of Cambridge, presents a concise yet comprehensive treatment of extremal graph theory.Unlike most graph theory treatises, this text features complete proofs for almost all of its results. Further insights into theory are provided by the numerous exercises of varying degrees of difficulty that accompany each chapter. A

  16. Adventure and Extreme Sports.

    Science.gov (United States)

    Gomez, Andrew Thomas; Rao, Ashwin

    2016-03-01

    Adventure and extreme sports often involve unpredictable and inhospitable environments, high velocities, and stunts. These activities vary widely and include sports like BASE jumping, snowboarding, kayaking, and surfing. Increasing interest and participation in adventure and extreme sports warrants understanding by clinicians to facilitate prevention, identification, and treatment of injuries unique to each sport. This article covers alpine skiing and snowboarding, skateboarding, surfing, bungee jumping, BASE jumping, and whitewater sports with emphasis on epidemiology, demographics, general injury mechanisms, specific injuries, chronic injuries, fatality data, and prevention. Overall, most injuries are related to overuse, trauma, and environmental or microbial exposure. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. Lost and Found: Evidence of Second-generation Stars Along the Asymptotic Giant Branch of the Globular Cluster NGC 6752

    NARCIS (Netherlands)

    Lapenna, E.; Lardo, C.; Mucciarelli, A.; Salaris, M.; Ferraro, F. R.; Lanzoni, B.; Massari, D.; Stetson, P. B.; Cassisi, S.; Savino, A.

    2016-01-01

    We derived chemical abundances for C, N, O, Na, Mg, and Al in 20 asymptotic giant branch (AGB) stars in the globular cluster (GC) NGC 6752. All these elements (but Mg) show intrinsic star-to-star variations and statistically significant correlations or anticorrelations analogous to those commonly

  18. Multiple stellar populations in the globular cluster M3 (NGC 5272) : a Strömgren perspective

    NARCIS (Netherlands)

    Massari, Davide; Lapenna, Emilio; Bragaglia, Angela; Dalessandro, Emanuele; Contreras Ramos, Rodrigo; Amigo, Pía

    2016-01-01

    We present Strömgren photometry of the Galactic Globular Cluster M3 to study its multiple generations phenomenon. The use of different colour-magnitude diagrams (CMDs) and especially of the notoriously efficient cy index allowed us to detect a double red giant branch in the cluster CMD. After

  19. The first two transient supersoft X-ray sources in M 31 globular clusters and the connection to classical novae

    Czech Academy of Sciences Publication Activity Database

    Henze, M.; Pietsch, W.; Haberl, F.; Sala, G.; Quimby, R.; Hernanz, M.; Della Valle, M.; Milne, P.; Williams, G.G.; Burwitz, V.; Greiner, J.; Stiele, H.; Hartmann, D. H.; Kong, A. K. H.; Hornoch, Kamil

    2009-01-01

    Roč. 500, č. 2 (2009), s. 769-779 ISSN 0004-6361 Institutional research plan: CEZ:AV0Z10030501 Keywords : M 31 * novae * globular clusters Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.179, year: 2009

  20. X-Ray and optical study of low core density globular clusters NGC6144 and E3

    NARCIS (Netherlands)

    Lan, S.-H.; Kong, A.K.H.; Verbunt, F.W.M.; Lewin, W.H.G.; Bassa, C.G.; Anderson, S.F.; Pooley, D.

    2010-01-01

    We report on the Chandra X-ray Observatory and Hubble Space Telescope (HST) observations of two low coredensity globular clusters, NGC6144 and E3. By comparing the number of X-ray sources inside the half-mass radius to those outside, we found six X-ray sources within the half-mass radius of NGC6144,

  1. The Absolute Age of the Globular Cluster M15 Using Near-infrared Adaptive Optics Images from PISCES/LBT.

    NARCIS (Netherlands)

    Monelli, M.; Testa, V.; Bono, G.; Ferraro, I.; Iannicola, G.; Fiorentino, G.; Arcidiacono, C.; Massari, D.; Boutsia, K.; Briguglio, R.; Busoni, L.; Carini, R.; Close, L.; Cresci, G.; Esposito, S.; Fini, L.; Fumana, M.; Guerra, J. C.; Hill, J.; Kulesa, C.; Mannucci, F.; McCarthy, D.; Pinna, E.; Puglisi, A.; Quiros-Pacheco, F.; Ragazzoni, R.; Riccardi, A.; Skemer, A.; Xompero, M.

    2015-01-01

    We present deep near-infrared J, {K}{{s}} photometry of the old, metal-poor Galactic globular cluster M15 obtained with images collected with the LUCI1 and PISCES cameras available at the Large Binocular Telescope (LBT). We show how the use of First Light Adaptive Optics (FLAO) system coupled with

  2. Statistics of Local Extremes

    DEFF Research Database (Denmark)

    Larsen, Gunner Chr.; Bierbooms, W.; Hansen, Kurt Schaldemose

    2003-01-01

    . A theoretical expression for the probability density function associated with local extremes of a stochasticprocess is presented. The expression is basically based on the lower four statistical moments and a bandwidth parameter. The theoretical expression is subsequently verified by comparison with simulated...

  3. Lower Extremity Paralysis.

    Science.gov (United States)

    Glancy, D Luke; Subramaniam, Pramilla N; Rodriguez, Juan F

    2016-11-15

    Severe hypokalemia in the absence of other electrolyte abnormalities, the result of diarrhea, caused striking electrocardiographic changes, generalized weakness, flaccid paralysis of the lower extremities, and biochemical evidence of mild skeletal and cardiac rhabdomyolysis in a 33-year-old man. Repletion of potassium reversed all abnormalities in 24 hours. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Hydrological extremes and security

    Directory of Open Access Journals (Sweden)

    Z. W. Kundzewicz

    2015-04-01

    Full Text Available Economic losses caused by hydrological extremes – floods and droughts – have been on the rise. Hydrological extremes jeopardize human security and impact on societal livelihood and welfare. Security can be generally understood as freedom from threat and the ability of societies to maintain their independent identity and their functional integrity against forces of change. Several dimensions of security are reviewed in the context of hydrological extremes. The traditional interpretation of security, focused on the state military capabilities, has been replaced by a wider understanding, including economic, societal and environmental aspects that get increasing attention. Floods and droughts pose a burden and serious challenges to the state that is responsible for sustaining economic development, and societal and environmental security. The latter can be regarded as the maintenance of ecosystem services, on which a society depends. An important part of it is water security, which can be defined as the availability of an adequate quantity and quality of water for health, livelihoods, ecosystems and production, coupled with an acceptable level of water-related risks to people, environments and economies. Security concerns arise because, over large areas, hydrological extremes − floods and droughts − are becoming more frequent and more severe. In terms of dealing with water-related risks, climate change can increase uncertainties, which makes the state’s task to deliver security more difficult and more expensive. However, changes in population size and development, and level of protection, drive exposure to hydrological hazards.

  5. Extremely Preterm Birth

    Science.gov (United States)

    ... Search FAQs Extremely Preterm Birth Page Navigation ▼ ACOG Pregnancy Book Patient Education FAQs Patient Education Pamphlets - Spanish FAQ173, June 2016 ... Labor and Birth (FAQ087) Tobacco, Alcohol, Drugs, and Pregnancy (FAQ170) Patient Education ... Committee Opinions Practice Bulletins Patient ...

  6. Extremity x-ray

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/003461.htm Extremity x-ray To use the sharing features on this page, ... in the body Risks There is low-level radiation exposure. X-rays are monitored and regulated to provide the ...

  7. Injuries in extreme sports.

    Science.gov (United States)

    Laver, Lior; Pengas, Ioannis P; Mei-Dan, Omer

    2017-04-18

    Extreme sports (ES) are usually pursued in remote locations with little or no access to medical care with the athlete competing against oneself or the forces of nature. They involve high speed, height, real or perceived danger, a high level of physical exertion, spectacular stunts, and heightened risk element or death.Popularity for such sports has increased exponentially over the past two decades with dedicated TV channels, Internet sites, high-rating competitions, and high-profile sponsors drawing more participants.Recent data suggest that the risk and severity of injury in some ES is unexpectedly high. Medical personnel treating the ES athlete need to be aware there are numerous differences which must be appreciated between the common traditional sports and this newly developing area. These relate to the temperament of the athletes themselves, the particular epidemiology of injury, the initial management following injury, treatment decisions, and rehabilitation.The management of the injured extreme sports athlete is a challenge to surgeons and sports physicians. Appropriate safety gear is essential for protection from severe or fatal injuries as the margins for error in these sports are small.The purpose of this review is to provide an epidemiologic overview of common injuries affecting the extreme athletes through a focus on a few of the most popular and exciting extreme sports.

  8. Extremism and Disability Chic

    Science.gov (United States)

    Kauffman, James M.; Badar, Jeanmarie

    2018-01-01

    The word chic refers to something fashionable or stylish. Chic varies for individuals and groups and with time and place. Something chic may have desirable or undesirable long-term consequences. Disability and extremism are also changeable concepts, depending on comparison to social norms. People with disabilities should have the option of being…

  9. World Weather Extremes. Revision,

    Science.gov (United States)

    1985-12-01

    very high latitudes where there is less moisture. 174J.p. Verdou, Extremes climatiques mondiales" [World Climatic- - E~tremes], France. Meteorologie...air pressure less than 92 kilopascals (27.17 inches) and winds over 249 kilometers per hour (155 miles per hour), and they cause " catastrophic " damage

  10. Extremity perfusion for sarcoma

    NARCIS (Netherlands)

    Hoekstra, Harald Joan

    2008-01-01

    For more than 50 years, the technique of extremity perfusion has been explored in the limb salvage treatment of local, recurrent, and multifocal sarcomas. The "discovery" of tumor necrosis factor-or. in combination with melphalan was a real breakthrough in the treatment of primarily irresectable

  11. 2MASS NIR photometry for 693 candidate globular clusters in M 31 and the Revised Bologna Catalogue

    Science.gov (United States)

    Galleti, S.; Federici, L.; Bellazzini, M.; Fusi Pecci, F.; Macrina, S.

    2004-03-01

    We have identified in the 2MASS database 693 known and candidate globular clusters in M 31. The 2MASS J, H, K magnitudes of these objects have been transformed to the same homogeneous photometric system of existing near infrared photometry of M 31 globulars, finally yielding J, H, K integrated photometry for 279 confirmed M 31 clusters, 406 unconfirmed candidates and 8 objects with controversial classification. Of these objects 529 lacked any previous estimate of their near infrared magnitudes. The newly assembled near infrared dataset has been implemented into a revised version of the Bologna Catalogue of M 31 globulars, with updated optical (UBVRI) photometry taken, when possible, from the most recent sources of CCD photometry available in the literature and transformed to a common photometric system. The final Revised Bologna Catalogue (available in electronic form) is the most comprehensive list presently available of confirmed and candidate M 31 globular clusters, with a total of 1164 entries. In particular, it includes 337 confirmed GCs, 688 GC candidates, 10 objects with controversial classification, 70 confirmed galaxies, 55 confirmed stars, and 4 H II regions lying within ˜3° from the center of the M 31 galaxy. Using the newly assembled database we show that the V-K color provides a powerful tool to discriminate between M 31 clusters and background galaxies, and we identify a sample of 83 globular cluster candidates, which is not likely to be contaminated by misclassified galaxies. Tables 2-4 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/917

  12. Isolated splenic peliosis in an immunocompromised patient

    African Journals Online (AJOL)

    cited by Gushiken1). Isolated splenic peliosis is extremely rare, and most cases are associated with peliosis hepatis. Establishing the incidence of splenic peliosis is difficult, since the condition usually remains asymptomatic or is discovered ...

  13. New Discoveries in the Search for Iron-Complex Globular Clusters

    Science.gov (United States)

    Johnson, Christian; Caldwell, Nelson; Rich, R. Michael; Mateo, Mario; Bailey, Jeb; Walker, Matthew G.; M2FS Team

    2018-01-01

    A growing number of Galactic globular clusters have been discovered that possess large intrinsic [Fe/H] and heavy element abundance variations. These "iron-complex" clusters are among the most massive in the Galaxy, and frequently exhibit extended blue horizontal branches and low metallicities. Additionally, a handful of clusters with [Fe/H] > -1 may also have large metallicity spreads (e.g., Terzan 5), but are instead characterized by having bimodal red horizontal brances. We present chemical composition analyses of several potential iron-complex clusters spanning [Fe/H] = -1.8 to -0.8, and discover that horizontal branch morphology alone is insufficient to identify clusters with heavy element abundance variations. However, we find that several of these clusters contain 4-5 chemically distinct populations, and the outer halo cluster NGC 6229 is added to the growing list of iron-complex clusters that may be the remnant cores of former dwarf spheroidal galaxies.

  14. The Globular Clusters of the Galactic Bulge: Results from Multiwavelength Follow-up Imaging

    Science.gov (United States)

    Cohen, Roger; Geisler, Doug; Mauro, Francesco; Alonso Garcia, Javier; Hempel, Maren; Sarajedini, Ata

    2018-01-01

    The Galactic globular clusters (GGCs) located towards the bulge of the Milky Way suffer from severe total and differential extinction and high field star densities. They have therefore been systematically excluded from deep, large-scale homogenous GGC surveys, and will present a challenge for Gaia. Meanwhile, existing observations of bulge GGCs have revealed tantalizing hints that they hold clues to Galactic formation and evolution not found elsewhere. Therefore, in order to better characterize these poorly studied stellar systems and place them in the context of their optically well-studied counterparts, we have undertaken imaging programs at optical and near-infrared wavelengths. We describe these programs and present a variety of results, including self-consistent measurement of bulge GGC ages and structural parameters. The limitations imposed by spatially variable extinction and extinction law are highlighted, along with the complimentary nature of forthcoming facilities, allowing us to finally complete our picture of the Milky Way GGC system.

  15. Stellar envelopes of globular clusters embedded in dark mini-haloes

    Science.gov (United States)

    Peñarrubia, Jorge; Varri, Anna Lisa; Breen, Philip G.; Ferguson, Annette M. N.; Sánchez-Janssen, Rubén

    2017-10-01

    We show that hard encounters in the central regions of globular clusters (GCs) embedded in dark matter (DM) haloes necessarily lead to the formation of gravitationally bound stellar envelopes that extend far beyond the nominal tidal radius of the system. Using statistical arguments and numerical techniques, we derive the equilibrium distribution function of stars ejected from the centre of a non-divergent spherical potential. Independently of the velocity distribution with which stars are ejected, GC envelopes have density profiles that approach asymptotically ρ ∼ r-4 at large distances and become isothermal towards the centre. Adding a DM halo component leaves two clear-cut observational signatures: (i) a flattening, or slightly increase of the projected velocity dispersion profile at large distances, and (ii) an outer surface density profile that is systematically shallower than in models with no DM.

  16. Ghosts of Milky Way's past: the globular cluster ESO 37-1 (E 3)

    Science.gov (United States)

    de la Fuente Marcos, R.; de la Fuente Marcos, C.; Moni Bidin, C.; Ortolani, S.; Carraro, G.

    2015-09-01

    Context. In the Milky Way, most globular clusters are highly conspicuous objects that were found centuries ago. However, a few dozen of them are faint, sparsely populated systems that were identified largely during the second half of the past century. One of the faintest is ESO 37-1 (E 3) and as such it remains poorly studied, with no spectroscopic observations published so far although it was discovered in 1976. Aims: We investigate the globular cluster E 3 in an attempt to better constrain its fundamental parameters. Spectroscopy of stars in the field of E 3 is shown here for the first time. Methods: Deep, precise VI CCD photometry of E 3 down to V ~ 26 mag is presented and analysed. Low-resolution, medium signal-to-noise ratio spectra of nine candidate members are studied to derive radial velocity and metallicity. Proper motions from the UCAC4 catalogue are used to explore the kinematics of the bright members of E 3. Results: Isochrone fitting indicates that E 3 is probably very old, with an age of about 13 Gyr; its distance from the Sun is nearly 10 kpc. It is also somewhat metal rich with [Fe/H] = -0.7. Regarding its kinematics, our tentative estimate for the proper motions is (μα cosδ,μδ) = (-7.0 ± 0.8, 3.5 ± 0.3) mas yr-1 (or a tangential velocity of 382 ± 79 km s-1) and for the radial velocity 45 ± 5 km s-1 in the solar rest frame. Conclusions: E 3 is one of the most intriguing globular clusters in the Galaxy. Having an old age and being metal rich is clearly a peculiar combination, only seen in a handful of objects like the far more conspicuous NGC 104 (47 Tucanae). In addition, its low luminosity and sparse population make it a unique template for the study of the final evolutionary phases in the life of a star cluster. Unfortunately, E 3 is among the most elusive and challenging known globular clusters because field contamination severely hampers spectroscopic studies. This research note is based on observations made with the ESO VLT at the

  17. Neutron-Capture Element Abundances in the Globular Cluster M15.

    Science.gov (United States)

    Sneden; Johnson; Kraft; Smith; Cowan; Bolte

    2000-06-20

    High-resolution, high signal-to-noise ratio, blue-violet spectra of three red giant branch tip stars in M15 have been obtained with the Keck I High-Resolution Echelle Spectrograph. These spectra have been analyzed to determine the abundances of several neutron-capture elements, including the radioactive chronometer element thorium. There are two principal results of this study. First, the abundances of the heavier (Z>/=56) elements for each of the three stars is well matched by a scaled solar system r-process abundance distribution. Second, a weighted mean-observed Th/Eu ratio for the stars implies an age for the neutron-capture material in M15 stars of 14+/-3 Gyr, in reasonable agreement with other recent age estimates for Galactic globular clusters.

  18. Image processing of globular clusters - Simulation for deconvolution tests (GlencoeSim)

    Science.gov (United States)

    Blazek, Martin; Pata, Petr

    2016-10-01

    This paper presents an algorithmic approach for efficiency tests of deconvolution algorithms in astronomic image processing. Due to the existence of noise in astronomical data there is no certainty that a mathematically exact result of stellar deconvolution exists and iterative or other methods such as aperture or PSF fitting photometry are commonly used. Iterative methods are important namely in the case of crowded fields (e.g., globular clusters). For tests of the efficiency of these iterative methods on various stellar fields, information about the real fluxes of the sources is essential. For this purpose a simulator of artificial images with crowded stellar fields provides initial information on source fluxes for a robust statistical comparison of various deconvolution methods. The "GlencoeSim" simulator and the algorithms presented in this paper consider various settings of Point-Spread Functions, noise types and spatial distributions, with the aim of producing as realistic an astronomical optical stellar image as possible.

  19. MAXI/GSC detection of X-ray enhancement toward the globular cluster Tarzan 1

    Science.gov (United States)

    Negoro, H.; Shidatsu, M.; Ueno, S.; Tomida, H.; Nakahira, S.; Kimura, M.; Ishikawa, M.; Nakagawa, Y.; Mihara, T.; Sugizaki, M.; Serino, M.; Morii, M.; Yamamoto, T.; Sugimoto, J.; Takagi, T.; Matsuoka, M.; Kawai, N.; Usui, R.; Ishikawa, K.; Yoshii, T.; Yoshida, A.; Sakamoto, T.; Nakano, Y.; Kawakubo, Y.; Tsunemi, H.; Sasaki, M.; Nakajima, M.; Fukushima, K.; Onodera, T.; Suzuki, K.; Ueda, Y.; Kawamuro, T.; Tsuboi, Y.; Higa, M.; Yamauchi, M.; Yoshidome, K.; Ogawa, Y.; Yamada, H.; Yamaoka, K.

    2013-06-01

    At 23:18 UT on May 24th, 2013, the MAXI/GSC auto-detection system triggered X-ray enhancement at the position consistent with the globular cluster Terzan 1. We have confirmed that the X-ray flux has gradually increased from around May 19th, 2013 (MJD 56431), and still remains stable on timescale of days at the 4-10 keV flux of about 8 mCrab. The central position of the enhanced region in the smoothed 2-20 keV image, obtained from May 19th to May 30th, is (R.A., Dec) = (263.84, -30.48) with a typical uncertainty of 0.3 deg.

  20. A spectroscopic study of chemical abundances in the globular cluster Omega Centauri

    International Nuclear Information System (INIS)

    Caldwell, S.P.

    1987-10-01

    Blue spectra at a resolution of 0.5 A of red giants in the globular clusters Omega Centauri and NGCs 288, 362, 6397 and 6809 (M55) have been obtained with the Anglo-Australian Telescope. The observations were made to test Sweigart and Mengel's [Astrophy S. J. 229, 624] theory of mixing of nuclearly-processed material to the star's surface, and to elucidate the relationship between primordial and evolutionary origins for the range in abundance within Omega Cen. The Omega Cen stars were chosen in two groups either side of the giant branch, covering the luminosity range where the onset of mixing was predicted to occur. Abundances of C, N, Fe and other heavy elements have been determined by fitting synthetic spectra, calculated from model atmospheres, to the observational data. (author)

  1. Searching for IMBHs in Galactic globular clusters through radial velocities of individual stars

    Science.gov (United States)

    Lanzoni, Barbara

    2016-02-01

    I present an overview of our ongoing project aimed at building a new generation of velocity dispersion profiles ad rotation curves for a representative sample of Galactic globular clusters, from the the radial velocity of hundreds of individual stars distributed at different distances from the cluster center. The innermost portion of the profiles will be used to constrain the possible presence of intermediate-mass black holes. The adopted methodology consists of combining spectroscopic observations acquired with three different instruments at the ESO-VLT: the adaptive-optics assisted, integral field unit (IFU) spectrograph SINFONI for the innermost and highly crowded cluster cores, the multi-IFU spectrograph KMOS for the intermediate regions, and the multi-fiber instrument FLAMES/GIRAFFE-MEDUSA for the outskirts. The case of NGC 6388, representing the pilot project that motivated the entire program, is described in some details.

  2. Carbon and nitrogen abundances in giant stars of the metal-poor globular cluster M92

    International Nuclear Information System (INIS)

    Carbon, D.F.; Langer, G.E.; Butler, D.; Kraft, R.P.; Suntzeff, N.B.; Kemper, E.; Trefzger, C.F.; Romanishin, W.

    1982-01-01

    Zinn in 1973 and 1977 and Norris and Zinn in 1977 showed that in M92 and several other metal-poor globular clusters the G bands (mostly due to CH) in the spectra of asymptotic giant branch (AGB) stars are systematically weaker than those found in the less highly evolved subgiant branch (SGB) stars. If carbon is depleted in the atmospheres of evolved stars because material at the base of the envelope, processed through the CN cycle, has been mixed with the material above, then the atmospheric nitrogen abundance should be correspondingly increased. In this paper we test the hypothesis that C and N abundances in M92 giants are negatively correlated as the evolutionary state becomes more advanced. We find that this simple hypothesis is not adequate to describe the complex behavior of C and N in the cluster giants

  3. Application of CCD uvby photometry to the globular cluster NGC 6397

    Energy Technology Data Exchange (ETDEWEB)

    Anthony-twarog, B.J.

    1987-06-01

    The CTIO 4-m prime-focus CCD has been used with Stromgren uvby filters to study the turnoff of the globular cluster NGC 6397. A well-defined CM diagram to V about 18 has been achieved. A previously noted correlation between delta m1 and delta c1 for turnoff stars appears to be confirmed by the observations. This correlation is not predicted by model atmosphere synthesis of Stromgren colors, and has not been confirmed by recent observations of metal-poor dwarfs bluer than b-y = 0.40 by Schuster and Nissen (1987). An age of 16.6 + or - 0.7 x 10 to the 9th yr is indicated for a color excess of E(b-y) = 0.13 and (Fe/H) = -2.2. 43 references.

  4. The puzzling assembly of the Milky Way halo – contributions from dwarf Spheroidals and globular clusters

    Directory of Open Access Journals (Sweden)

    Lépine S.

    2012-02-01

    Full Text Available While recent sky surveys have uncovered large numbers of ever fainter Milky Way satellites, their classification as star clusters, low-luminosity galaxies, or tidal overdensities remains often unclear. Likewise, their contributions to the build-up of the halo is yet debated. In this contribution we will discuss the current knowledge of the stellar populations and chemo-dynamics in these puzzling satellites, with a particular focus on dwarf spheroidal galaxies and the globular clusters in the outer Galactic halo. Also the question of whether some of the outermost halo objects are dynamically associated with the (Milky Way halo at all is addressed in terms of proper measurements in the remote Leo I and II dwarf galaxies.

  5. Suppression of globular cluster formation in metal-poor gas clouds by Lyman α radiation feedback

    Science.gov (United States)

    Abe, Makito; Yajima, Hidenobu

    2018-03-01

    We study the impact of Ly α radiation feedback on globular cluster (GC) formation. In this Letter, we analytically derive the relation between star formation efficiency (SFE) and metallicity in spherical clouds with the Ly α radiation feedback. Our models show that the SFE becomes small as the metallicity decreases. In metal-poor gas clouds, Ly α photons are trapped for a long time and exert strong radiation force to the gas, resulting in the suppression of star formation. We find that bound star clusters (SFE ≳ 0.5) form only for the metallicity higher than ˜ 10- 2.5 Z⊙ in the case with the initial cloud mass 105 M⊙ and the radius 5 pc. Our models successfully reproduce the lower bound of observed metallicity of GCs. Thus, we suggest that the Ly α radiation feedback can be essential in understanding the formation of GCs.

  6. SANS study of understanding mechanism of cold gelation of globular proteins

    International Nuclear Information System (INIS)

    Chinchalikar, A. J.; Kumar, Sugam; Aswal, V. K.; Wagh, A. G.; Kohlbrecher, J.

    2014-01-01

    Small-angle neutron scattering (SANS) has been used to probe the evolution of interaction and the resultant structures in the cold gelation of globular proteins. The cold gelation involves two steps consisting of irreversible protein deformation by heating followed by some means (e.g. increasing ionic strength) to bring them together at room temperature. We have examined the role of different salts in cold gelation of preheated aqueous Bovine Serum Albumin (BSA) protein solutions. The interactions have been modeled by two Yukawa potential combining short-range attraction and long-range repulsion. We show that in step 1 (preheated temperature effect) the deformation of protein increases the magnitude of attractive interaction but not sufficient to induce gel. The attractive interaction is further enhanced in step 2 (salt effect) to result in gel formation. The salt effect is found to be strongly depending on the valency of the counterions. The gel structure has been characterized by the mass fractals

  7. Immunochemical and autoantigenic properties of the globular domain of basement membrane collagen (type IV).

    Science.gov (United States)

    von der Mark, H; Oberbäumer, I; Timpl, R; Kemler, R; Wick, G

    1985-02-01

    Polyclonal rabbit antibodies raised against the globular domain NC1 of collagen IV from human placenta and a mouse tumor react with conformational antigenic determinants present on the NC1 hexamers and also with the three major subunits obtained after dissociation. The antibodies recognized unique structures within basement membranes and showed a broad tissue reactivity but only limited species cross-reactivity. Using these antibodies, it was possible to detect small amounts of collagen IV antigens from cell cultures and in serum. Monoclonal rat antibodies against mouse NC1 revealed a similar reaction potential. Autoantibodies could be produced in mice against mouse NC1 which react with kidney and lung basement membranes in a pathological manner, mimicking Goodpasture syndrome.

  8. Abundance inhomogeneities and atmospheric structure in CN-bimodal globular cluster giants

    Science.gov (United States)

    Drake, Jeremy J.; Plez, Bertrand; Smith, Verne V.

    1993-01-01

    It has been suggested by several authors that the sodium and aluminum abundance variations correlating with CN-band strength, frequently observed in CN-bimodal globular cluster giants, could be spurious manifestations of different temperature structures in the 'CN-strong' and 'CN-weak' stars, caused by different molecular line blanketing related to the C, N, and O trio. For stellar parameters generally appropriate to giants in the intermediate metallicity CN-bimodal cluster M4, we demonstrate through new model atmosphere calculations, employing opacity sampling and spherical geometry, that the observed abundance anomalies cannot be the result of atmospheric temperature structure. Our results using spherical geometry are compared to identical calculations performed with plane-parallel geometry: the effects of atmospheric extension on derived abundances for all lines considered amount to less than 0.1 dex.

  9. Characterization of dry globular proteins and protein fibrils by synchrotron radiation vacuum UV circular dichroism

    DEFF Research Database (Denmark)

    Nesgaard, Lise W.; Hoffmann, Søren Vrønning; Andersen, Christian Beyschau

    2008-01-01

    different types of protein fibrils, highlighting that bona fide fibrils formed by lysozyme are structurally more similar to the nonclassical fibrillar aggregates formed by the SerADan peptide than with the amyloid formed by alpha-synuclein. Thus, despite the lack of direct structural conclusions......Circular dichroism using synchrotron radiation (SRCD) can extend the spectral range down to approximately 130 nm for dry proteins, potentially providing new structural information. Using a selection of dried model proteins, including alpha-helical, beta-sheet, and mixed-structure proteins, we...... observe a low-wavelength band in the range 130-160 nm, whose intensity and peak position is sensitive to the secondary structure of the protein and may also reflect changes in super-secondary structure. This band has previously been observed for peptides but not for globular proteins, and is compatible...

  10. GLOBULAR RESISTANCE MODIFICATION ON RATS CONSECUTIVELY TO Al2(SO43 ADDITION FOR TWO GENERATION

    Directory of Open Access Journals (Sweden)

    STANA LOREDANA GABRIELA

    2007-01-01

    Full Text Available Some of the major modifications on membranes produced by the oxygen reactivespecies are membranal structure and functions modifications, lipids peroxydation,membranal protein alterations and transportation disturbances thru membranes.A series of xenobotics like oxidant pollutants, lead, aluminium and others directlyor indirectly are producing thru metabolization free radicals which interact withcells components and alterate their functions. The purpose of this paper was torelieve the impact of aluminium cumulative addition onto globular resistance onrats. Has been administrated three levels of aluminium (200ppb, 400 ppb şi 1000ppb as Al2(SO43 ad libidum in water. Was followed their toxicity impact on theglobular resistance for two generations. The results indicate a decrease ofglobular resistance directly correlated with the aluminium addition.

  11. Isolated galaxies

    International Nuclear Information System (INIS)

    Einasto, Maret

    1990-01-01

    To test for the possible presence of really isolated galaxies, which form a randomly distributed population in voids, we compare the distribution of most isolated galaxies in an observed sample with distributions of the same number of random points using the nearest neighbour test. The results show that the random population of really isolated galaxies does not exist - even the most isolated galaxies are connected with systems of galaxies, forming their outlying parts. (author)

  12. A Spectroscopic Analysis of the Galactic Globular Cluster NGC 6273 (M19)

    Science.gov (United States)

    Johnson, Christian I.; Rich, R. Michael; Pilachowski, Catherine A.; Caldwell, Nelson; Mateo, Mario; Bailey, John I., III; Crane, Jeffrey D.

    2015-08-01

    A combined effort utilizing spectroscopy and photometry has revealed the existence of a new globular cluster class. These “anomalous” clusters, which we refer to as “iron-complex” clusters, are differentiated from normal clusters by exhibiting large (≳0.10 dex) intrinsic metallicity dispersions, complex sub-giant branches, and correlated [Fe/H] and s-process enhancements. In order to further investigate this phenomenon, we have measured radial velocities and chemical abundances for red giant branch stars in the massive, but scarcely studied, globular cluster NGC 6273. The velocities and abundances were determined using high resolution (R ˜ 27,000) spectra obtained with the Michigan/Magellan Fiber System (M2FS) and MSpec spectrograph on the Magellan-Clay 6.5 m telescope at Las Campanas Observatory. We find that NGC 6273 has an average heliocentric radial velocity of +144.49 km s-1 (σ = 9.64 km s-1) and an extended metallicity distribution ([Fe/H] = -1.80 to -1.30) composed of at least two distinct stellar populations. Although the two dominant populations have similar [Na/Fe], [Al/Fe], and [α/Fe] abundance patterns, the more metal-rich stars exhibit significant [La/Fe] enhancements. The [La/Eu] data indicate that the increase in [La/Fe] is due to almost pure s-process enrichment. A third more metal-rich population with low [X/Fe] ratios may also be present. Therefore, NGC 6273 joins clusters such as ω Centauri, M2, M22, and NGC 5286 as a new class of iron-complex clusters exhibiting complicated star formation histories. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  13. An intermediate-mass black hole in the centre of the globular cluster 47 Tucanae.

    Science.gov (United States)

    Kızıltan, Bülent; Baumgardt, Holger; Loeb, Abraham

    2017-02-08

    Intermediate-mass black holes should help us to understand the evolutionary connection between stellar-mass and super-massive black holes. However, the existence of intermediate-mass black holes is still uncertain, and their formation process is therefore unknown. It has long been suspected that black holes with masses 100 to 10,000 times that of the Sun should form and reside in dense stellar systems. Therefore, dedicated observational campaigns have targeted globular clusters for many decades, searching for signatures of these elusive objects. All candidate signatures appear radio-dim and do not have the X-ray to radio flux ratios required for accreting black holes. Based on the lack of an electromagnetic counterpart, upper limits of 2,060 and 470 solar masses have been placed on the mass of a putative black hole in 47 Tucanae (NGC 104) from radio and X-ray observations, respectively. Here we show there is evidence for a central black hole in 47 Tucanae with a mass of solar masses when the dynamical state of the globular cluster is probed with pulsars. The existence of an intermediate-mass black hole in the centre of one of the densest clusters with no detectable electromagnetic counterpart suggests that the black hole is not accreting at a sufficient rate to make it electromagnetically bright and therefore, contrary to expectations, is gas-starved. This intermediate-mass black hole might be a member of an electromagnetically invisible population of black holes that grow into supermassive black holes in galaxies.

  14. THE HUBBLE SPACE TELESCOPE UV LEGACY SURVEY OF GALACTIC GLOBULAR CLUSTERS. VIII. PRELIMINARY PUBLIC CATALOG RELEASE

    Energy Technology Data Exchange (ETDEWEB)

    Soto, M.; Bellini, A.; Anderson, J.; Van der Marel, R. P.; Brown, T. M. [Space Telescope Science Institute, San Martin Drive 3700, Baltimore, MD 21218 (United States); Piotto, G.; Granata, V.; Ortolani, S.; Nardiello, D. [Dipartimento di Fisica e Astronomia Galileo Galilei, Università di Padova, Vicolo dell’Osservatorio 3, I-35122 Padova (Italy); Bedin, L. R. [INAF-Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova (Italy); Milone, A. P. [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT, 2611 (Australia); Cool, A. M. [Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132 (United States); King, I. R. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Sarajedini, A. [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States); Cassisi, S. [Osservatorio Astronomico di Teramo, Via Mentore Maggini s.n.c., I-64100 Teramo (Italy); Aparicio, A.; Hidalgo, S., E-mail: mario.soto@uda.cl [Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Canary Islands (Spain)

    2017-01-01

    The Hubble Space Telescope (HST) UV Legacy Survey of Galactic Globular Clusters (GO-13297) has been specifically designed to complement the existing F606W and F814W observations of the Advanced Camera for Surveys (ACS) Globular Cluster Survey (GO-10775) by observing the most accessible 47 of the previous survey’s 65 clusters in three WFC3/UVIS filters F275W, F336W, and F438W. The new survey also adds super-solar metallicity open cluster NGC 6791 to increase the metallicity diversity. The combined survey provides a homogeneous 5-band data set that can be used to pursue a broad range of scientific investigations. In particular, the chosen UV filters allow the identification of multiple stellar populations by targeting the regions of the spectrum that are sensitive to abundance variations in C, N, and O. In order to provide the community with uniform preliminary catalogs, we have devised an automated procedure that performs high-quality photometry on the new UV observations (along with similar observations of seven other programs in the archive). This procedure finds and measures the potential sources on each individual exposure using library point-spread functions and cross-correlates these observations with the original ACS-Survey catalog. The catalog of 57 clusters we publish here will be useful to identify stars in the different stellar populations, in particular for spectroscopic follow-up. Eventually, we will construct a more sophisticated catalog and artificial-star tests based on an optimal reduction of the UV survey data, but the catalogs presented here give the community the chance to make early use of this HST Treasury survey.

  15. A Deep X-ray Survey of the Globular Cluster Omega Centauri

    Science.gov (United States)

    Henleywillis, Simon; Cool, Adrienne M.; Haggard, Daryl; Heinke, Craig; Callanan, Paul; Zhao, Yue

    2018-03-01

    We identify 233 X-ray sources, of which 95 are new, in a 222 ks exposure of Omega Centauri with the Chandra X-ray Observatory's ACIS-I detector. The limiting unabsorbed flux in the core is fX(0.5-6.0 keV) ≃ 3×10-16 erg s-1 cm-2 (Lx ≃ 1×1030 erg s-1 at 5.2 kpc). We estimate that ˜60 ± 20 of these are cluster members, of which ˜30 lie within the core (rc = 155 arcsec), and another ˜30 between 1-2 core radii. We identify four new optical counterparts, for a total of 45 likely identifications. Probable cluster members include 18 cataclysmic variables (CVs) and CV candidates, one quiescent low-mass X-ray binary, four variable stars, and five stars that are either associated with ω Cen's anomalous red giant branch, or are sub-subgiants. We estimate that the cluster contains 40 ± 10 CVs with Lx > 1031 erg s-1, confirming that CVs are underabundant in ω Cen relative to the field. Intrinsic absorption is required to fit X-ray spectra of six of the nine brightest CVs, suggesting magnetic CVs, or high-inclination systems. Though no radio millisecond pulsars (MSPs) are currently known in ω Cen, more than 30 unidentified sources have luminosities and X-ray colours like those of MSPs found in other globular clusters; these could be responsible for the Fermi-detected gamma-ray emission from the cluster. Finally, we identify a CH star as the counterpart to the second-brightest X-ray source in the cluster and argue that it is a symbiotic star. This is the first such giant/white dwarf binary to be identified in a globular cluster.

  16. Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5

    Science.gov (United States)

    Kupper, Andreas Hans Wilhelm; Balbinot, Eduardo; Bonaca, Ana; Johnston, Kathryn V.; Hogg, David W.; Kroupa, Pavel; Santiago, Basilio

    2015-01-01

    We model the tidal stream of the Milky Way globular cluster Palomar 5 (Pal 5), and show that the unique geometry of the problem yields powerful constraints on the model parameters characterizing the Local Standard of Rest (LSR), the Milky Way and Pal 5 itself. Using only SDSS data and a few radial velocities from the literature, we find that the distance of the Sun from the Galactic Center is 8.30+/-0.25 kpc, and the LSR transverse velocity is 242+/-16 km/s. Assuming that the dark halo of the Galaxy follows a NFW density profile, we fit it with a virial mass of (1.6+/-0.4) 1012Msun, a virial radius of 195+/-19 kpc, and hence a rather low concentration of 5+/-2. Moreover, we find it with a flattening of qz = 0.95(+0.16)(-0.12) to be essentially spherical - at least within the inner 25 kpc, which are effectively probed by Pal 5. We also determine Pal 5's mass, distance and proper motions independently from other methods, which enables us to perform vital cross-checks for these methods. We conclude that finding more globular cluster streams is essential for mapping out the structure of the halo of our Galaxy to high precision. Finally, we point out that all our best-fit models yield similar substructure patterns as the ones observed in the Pal 5 stream within about 5 kpc of the cluster. The origin of these substructures is epicylic motion of stars along the stream. Such epicylic substructures have to be taken into account when searching tidal streams for signs of past encounters with dark-matter subhalos

  17. Chemical Abundances of Red Giant Stars in the Globular Cluster M107 (NGC 6171)

    Science.gov (United States)

    O'Connell, Julia E.; Johnson, Christian I.; Pilachowski, Catherine A.; Burks, Geoffrey

    2011-10-01

    We present chemical abundances of Al and several Fe-Peak and neutron-capture elements for 13 red giant branch stars in the Galactic globular cluster NGC 6171 (M107). The abundances were determined using equivalent width and spectrum synthesis analyses of moderate-resolution ( R ˜ 15,000), moderate signal-to-noise ratio ( ˜ 80) spectra obtained with the WIYN telescope and Hydra multifiber spectrograph. A comparison between photometric and spectroscopic effective temperature estimates seems to indicate that a reddening value of E(B - V) = 0.46 may be more appropriate for this cluster than the more commonly used value of E(B - V) = 0.33. Similarly, we found that a distance modulus of (m - M)V ≈ 13.7 provided reasonable surface gravity estimates for the stars in our sample. Our spectroscopic analysis finds M107 to be moderately metal-poor with = -0.93 and also exhibits a small star-to-star metallicity dispersion (σ = 0.04). These results are consistent with previous photometric and spectroscopic studies. Aluminum appears to be moderately enhanced in all program stars ( = +0.39, σ = 0.11). The relatively small star-to-star scatter in [Al/Fe] differs from the trend found in more metal-poor globular clusters, and is more similar to what is found in clusters with [Fe/H] ≳ -1. The cluster also appears to be moderately r-process-enriched with = +0.32 (σ = 0.17).

  18. Globular adiponectin induces a pro-inflammatory response in human astrocytic cells

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Zhongxiao; Mah, Dorrian; Simtchouk, Svetlana [School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC (Canada); Klegeris, Andis [Department of Biology, University of British Columbia Okanagan, Kelowna, BC (Canada); Little, Jonathan P., E-mail: jonathan.little@ubc.ca [School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC (Canada)

    2014-03-28

    Highlights: • Adiponectin receptors are expressed in human astrocytes. • Globular adiponectin induces secretion of IL-6 and MCP-1 from cultured astrocytes. • Adiponectin may play a pro-inflammatory role in astrocytes. - Abstract: Neuroinflammation, mediated in part by activated brain astrocytes, plays a critical role in the development of neurodegenerative disorders, including Alzheimer’s disease (AD). Adiponectin is the most abundant adipokine secreted from adipose tissue and has been reported to exert both anti- and pro-inflammatory effects in peripheral tissues; however, the effects of adiponectin on astrocytes remain unknown. Shifts in peripheral concentrations of adipokines, including adiponectin, could contribute to the observed link between midlife adiposity and increased AD risk. The aim of the present study was to characterize the effects of globular adiponectin (gAd) on pro-inflammatory cytokine mRNA expression and secretion in human U373 MG astrocytic cells and to explore the potential involvement of nuclear factor (NF)-κB, p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK) and phosphatidylinositide 3-kinases (PI3 K) signaling pathways in these processes. We demonstrated expression of adiponectin receptor 1 (adipoR1) and adipoR2 in U373 MG cells and primary human astrocytes. gAd induced secretion of interleukin (IL)-6 and monocyte chemoattractant protein (MCP)-1, and gene expression of IL-6, MCP-1, IL-1β and IL-8 in U373 MG cells. Using specific inhibitors, we found that NF-κB, p38MAPK and ERK1/2 pathways are involved in gAd-induced induction of cytokines with ERK1/2 contributing the most. These findings provide evidence that gAd may induce a pro-inflammatory phenotype in human astrocytes.

  19. Strömgren photometry in globular clusters: M55 & M22

    Science.gov (United States)

    Richter, P.; Hilker, M.; Richtler, T.

    1999-10-01

    We present Strömgren CCD photometry for the two galactic globular clusters M55 (NGC 6809) and M22 (NGC 6656). We find average Strömgren metallicities of -1.71+/- 0.04 dex for M55 and -1.62+/- 0.08 dex for M22. The determination of metal abundances in cluster giants with the Strömgren m_1 index in comparison with spectroscopic data from Briley et al. (1993) and Norris & Freeman (1982, 1983) shows that M55 and M22 have different distributions of cyanogen strengths. In M55, no CN abundance variations are visible among the giant-branch stars. In striking contrast, a large dispersion of cyanogen strengths is seen in M22. For M22 we find patchily distributed variations in the foreground reddening of Delta E(B-V) ~ 0.07, which explain the colour dispersion among the giant-branch stars. There is no evidence for a spread in iron within M22 since the variations in m_1 are dominated by the large range in CN abundances, as already found by Anthony-Twarog et al. (1995). The difference between M55 and M22 may resemble the difference in integral CN band strength between M31 globular clusters and the galactic system. The colour-magnitude diagram of M55 shows the presence of a population of 56 blue-straggler stars that are more centrally concentrated than the red giant-branch stars. Based on data collected at the European Southern Observatory, La Silla, Chile

  20. The SAGES Legacy Unifying Globulars and Galaxies survey (SLUGGS): sample definition, methods, and initial results

    Energy Technology Data Exchange (ETDEWEB)

    Brodie, Jean P.; Romanowsky, Aaron J.; Jennings, Zachary G.; Pota, Vincenzo; Kader, Justin; Roediger, Joel C.; Villaume, Alexa; Arnold, Jacob A.; Woodley, Kristin A. [University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States); Strader, Jay [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Forbes, Duncan A.; Pastorello, Nicola; Usher, Christopher; Blom, Christina; Kartha, Sreeja S. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Foster, Caroline; Spitler, Lee R., E-mail: jbrodie@ucsc.edu [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia)

    2014-11-20

    We introduce and provide the scientific motivation for a wide-field photometric and spectroscopic chemodynamical survey of nearby early-type galaxies (ETGs) and their globular cluster (GC) systems. The SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey is being carried out primarily with Subaru/Suprime-Cam and Keck/DEIMOS. The former provides deep gri imaging over a 900 arcmin{sup 2} field-of-view to characterize GC and host galaxy colors and spatial distributions, and to identify spectroscopic targets. The NIR Ca II triplet provides GC line-of-sight velocities and metallicities out to typically ∼8 R {sub e}, and to ∼15 R {sub e} in some cases. New techniques to extract integrated stellar kinematics and metallicities to large radii (∼2-3 R {sub e}) are used in concert with GC data to create two-dimensional (2D) velocity and metallicity maps for comparison with simulations of galaxy formation. The advantages of SLUGGS compared with other, complementary, 2D-chemodynamical surveys are its superior velocity resolution, radial extent, and multiple halo tracers. We describe the sample of 25 nearby ETGs, the selection criteria for galaxies and GCs, the observing strategies, the data reduction techniques, and modeling methods. The survey observations are nearly complete and more than 30 papers have so far been published using SLUGGS data. Here we summarize some initial results, including signatures of two-phase galaxy assembly, evidence for GC metallicity bimodality, and a novel framework for the formation of extended star clusters and ultracompact dwarfs. An integrated overview of current chemodynamical constraints on GC systems points to separate, in situ formation modes at high redshifts for metal-poor and metal-rich GCs.

  1. Photometric study of the eclipsing blue straggler V205 in the globular cluster NGC 5139

    Science.gov (United States)

    Li, K.

    2018-02-01

    B and V light curves of an EA-type binary V205 in the globular cluster NGC 5139 are analyzed by the W-D program. We found that V205 is possibly a detached binary and the mass ratio is 0.1596. The secondary component is touching or nearly touching its inner Roche Lobe. By studying the O - C diagram of V205, we discovered that the orbital period is continuously decrease at a rate of dp / dt = - 1.89(± 0.01) ×10-7 d yr-1 and should be caused by angular momentum and mass loss. The angular momentum loss will drive it evolve into a contact binary. Since V205 is a proper motion member of NGC 5139, we estimated its absolute parameters based on the distance modulus of the cluster and determined that: a = 2.50R⊙ , M1 = 0.76M⊙ , R1 = 1.14R⊙ , L1 = 5.46L⊙ , M2 = 0.12M⊙ , R2 = 0.52R⊙ , and L2 = 0.70L⊙ . V205 occupied the blue straggler stars on the color-magnitude diagram of NGC 5139. It is an eclipsing blue straggler and is most possibly formed by mass transfer between the two components. Since original short-period systems similar to V205 should be evolved in such a long life time of the globular cluster, the short-period binary should undergo special evolutionary stages. High accuracy photometric and high resolution spectral observations are essential for this unusual system.

  2. A photometric study of globular clusters observed by the APOGEE survey

    Science.gov (United States)

    Mészáros, Szabolcs; García-Hernández, D. A.; Cassisi, Santi; Monelli, Matteo; Szigeti, László; Dell'Agli, Flavia; Derekas, Alíz; Masseron, Thomas; Shetrone, Matthew; Stetson, Peter; Zamora, Olga

    2018-04-01

    In this paper, we describe the photometric and spectroscopic properties of multiple populations in seven northern globular clusters. In this study, we employ precise ground-based photometry from the private collection of Stetson, space photometry from the Hubble Space Telescope (HST), literature abundances of Na and O, and Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey abundances for Mg, Al, C, and N. Multiple populations are identified by their position in the CU, B, I -Vpseudo colour-magnitude diagram (pseudo-CMD) and confirmed with their chemical composition determined using abundances. We confirm the expectation from previous studies that the red giant branches (RGBs) in all seven clusters are split and the different branches have different chemical compositions. The Mg-Al anticorrelations were well explored by the APOGEE and Gaia-ESO surveys for most globular clusters, some clusters showing bimodal distributions, while others continuous distributions. Even though the structure (i.e. bimodal versus continuous) of Mg-Al can greatly vary, the Al-rich and Al-poor populations do not seem to have very different photometric properties, agreeing with theoretical calculations. There is no one-to-one correspondence between the Mg-Al anticorrelation shape (bimodal versus continuous) and the structure of the RGB seen in the HST pseudo-CMDs, with the HST photometric information usually implying more complex formation/evolution histories than the spectroscopic ones. We report on finding two second-generation horizontal branch (HB) stars in M5, and five second-generation asymptotic giant branch (AGB) stars in M92, which is the most metal-poor cluster to date in which second-generation AGB stars have been observed.

  3. A simple model for electrical charge in globular macromolecules and linear polyelectrolytes in solution

    Science.gov (United States)

    Krishnan, M.

    2017-05-01

    We present a model for calculating the net and effective electrical charge of globular macromolecules and linear polyelectrolytes such as proteins and DNA, given the concentration of monovalent salt and pH in solution. The calculation is based on a numerical solution of the non-linear Poisson-Boltzmann equation using a finite element discretized continuum approach. The model simultaneously addresses the phenomena of charge regulation and renormalization, both of which underpin the electrostatics of biomolecules in solution. We show that while charge regulation addresses the true electrical charge of a molecule arising from the acid-base equilibria of its ionizable groups, charge renormalization finds relevance in the context of a molecule's interaction with another charged entity. Writing this electrostatic interaction free energy in terms of a local electrical potential, we obtain an "interaction charge" for the molecule which we demonstrate agrees closely with the "effective charge" discussed in charge renormalization and counterion-condensation theories. The predictions of this model agree well with direct high-precision measurements of effective electrical charge of polyelectrolytes such as nucleic acids and disordered proteins in solution, without tunable parameters. Including the effective interior dielectric constant for compactly folded molecules as a tunable parameter, the model captures measurements of effective charge as well as published trends of pKa shifts in globular proteins. Our results suggest a straightforward general framework to model electrostatics in biomolecules in solution. In offering a platform that directly links theory and experiment, these calculations could foster a systematic understanding of the interrelationship between molecular 3D structure and conformation, electrical charge and electrostatic interactions in solution. The model could find particular relevance in situations where molecular crystal structures are not available or

  4. FURTHER DEFINITION OF THE MASS-METALLICITY RELATION IN GLOBULAR CLUSTER SYSTEMS AROUND BRIGHTEST CLUSTER GALAXIES

    International Nuclear Information System (INIS)

    Cockcroft, Robert; Harris, William E.; Wehner, Elizabeth M. H.; Whitmore, Bradley C.; Rothberg, Barry

    2009-01-01

    We combine the globular cluster (GC) data for 15 brightest cluster galaxies and use this material to trace the mass-metallicity relations (MMRs) in their globular cluster systems (GCSs). This work extends previous studies which correlate the properties of the MMR with those of the host galaxy. Our combined data sets show a mean trend for the metal-poor subpopulation that corresponds to a scaling of heavy-element abundance with cluster mass Z ∼ M 0.30±0.05 . No trend is seen for the metal-rich subpopulation which has a scaling relation that is consistent with zero. We also find that the scaling exponent is independent of the GCS specific frequency and host galaxy luminosity, except perhaps for dwarf galaxies. We present new photometry in (g',i') obtained with Gemini/GMOS for the GC populations around the southern giant ellipticals NGC 5193 and IC 4329. Both galaxies have rich cluster populations which show up as normal, bimodal sequences in the color-magnitude diagram. We test the observed MMRs and argue that they are statistically real, and not an artifact caused by the method we used. We also argue against asymmetric contamination causing the observed MMR as our mean results are no different from other contamination-free studies. Finally, we compare our method to the standard bimodal fitting method (KMM or RMIX) and find our results are consistent. Interpretation of these results is consistent with recent models for GC formation in which the MMR is determined by GC self-enrichment during their brief formation period.

  5. A single population of red globular clusters around the massive compact galaxy NGC 1277

    Science.gov (United States)

    Beasley, Michael A.; Trujillo, Ignacio; Leaman, Ryan; Montes, Mireia

    2018-03-01

    Massive galaxies are thought to form in two phases: an initial collapse of gas and giant burst of central star formation, followed by the later accretion of material that builds up their stellar and dark-matter haloes. The systems of globular clusters within such galaxies are believed to form in a similar manner. The initial central burst forms metal-rich (spectrally red) clusters, whereas more metal-poor (spectrally blue) clusters are brought in by the later accretion of less-massive satellites. This formation process is thought to result in the multimodal optical colour distributions that are seen in the globular cluster systems of massive galaxies. Here we report optical observations of the massive relic-galaxy candidate NGC 1277—a nearby, un-evolved example of a high-redshift ‘red nugget’ galaxy. We find that the optical colour distribution of the cluster system of NGC 1277 is unimodal and entirely red. This finding is in strong contrast to other galaxies of similar and larger stellar mass, the cluster systems of which always exhibit (and are generally dominated by) blue clusters. We argue that the colour distribution of the cluster system of NGC 1277 indicates that the galaxy has undergone little (if any) mass accretion after its initial collapse, and use simulations of possible merger histories to show that the stellar mass due to accretion is probably at most ten per cent of the total stellar mass of the galaxy. These results confirm that NGC 1277 is a genuine relic galaxy and demonstrate that blue clusters constitute an accreted population in present-day massive galaxies.

  6. Therapeutic effects of globular adiponectin in diabetic rats with nonalcoholic fatty liver disease.

    Science.gov (United States)

    Ma, Hong; Cui, Fan; Dong, Jing-Jing; You, Guo-Ping; Yang, Xiang-Jiu; Lu, Hua-Dong; Huang, Yan-Ling

    2014-10-28

    To explore the therapeutic role of globular adiponectin (gAd) in high-fat diet/streptozotocin (STZ)-induced type 2 diabetic rats with nonalcoholic fatty liver disease (NAFLD). Seven rats were fed a basic diet (normal control group; NC) during the experiment. Experimental rats (14 rats) were given a high-fat diet for 4 wk and were then injected with STZ to induce type 2 diabetes mellitus (T2DM) and NAFLD. Half of the T2DM/NAFLD rats were randomly injected intraperitoneally with gAd for 7 d (gAd-treated group), while the other 7 rats (T2DM/NAFLD group) received 0.9% saline. Plasma biochemical parameters and insulin concentrations were measured. Liver histopathology was examined by hematoxylin-eosin staining. Insulin receptor expression in the liver was analyzed by immunohistochemical staining, Western blot and quantitative real-time reverse transcription polymerase chain reaction analysis. Compared to the control group, the T2DM/NAFLD group had increased levels of glucolipid and decreased levels of insulin. Plasma glucose and lipid levels were decreased in the gAd-treated group, while serum insulin levels increased. The expression of insulin receptor in the T2DM/NAFLD group increased compared with the NC group, and gAd downregulated insulin receptor expression in the livers of T2DM/NAFLD rats. Steatosis of the liver was alleviated in the gAd-treated group compared to the T2DM/NAFLD group (NAS 1.39 ± 0.51 vs 1.92 ± 0.51, P Globular adiponectin exerts beneficial effects in T2DM rats with NAFLD by promoting insulin secretion, mediating glucolipid metabolism, regulating insulin receptor expression and alleviating hepatic steatosis.

  7. ON THE RR LYRAE STARS IN GLOBULARS. IV. ω CENTAURI OPTICAL UBVRI PHOTOMETRY

    Energy Technology Data Exchange (ETDEWEB)

    Braga, V. F.; Bono, G.; Buonanno, R. [Department of Physics, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, I-00133 Roma (Italy); Stetson, P. B. [NRC-Herzberg, Dominion Astrophysical Observatory, 5071 West Saanich Road, Victoria BC V9E 2E7 (Canada); Dall’Ora, M. [INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy); Ferraro, I.; Iannicola, G.; Castellani, M. [INAF-Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monte Porzio Catone (Italy); Fiorentino, G. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Freyhammer, L. M. [Jeremiah Horrocks Institute of Astrophysics, University of Central Lancashire, Preston PR1 2HE (United Kingdom); Marengo, M.; Neeley, J. [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Valenti, E. [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei Munchen (Germany); Calamida, A. [National Optical Astronomy Observatory, 950 N Cherry Avenue, Tucson, AZ 85719 (United States); Da Silva, R.; Fabrizio, M.; Giuffrida, G. [ASDC, via del Politecnico snc, I-00133 Roma (Italy); Degl’Innocenti, S. [INFN, Sezione di Pisa, Largo Pontecorvo 3, I-56127, Pisa (Italy); Di Cecco, A. [INAF-Osservatorio Astronomico di Teramo, Via Mentore Maggini snc, Loc. Collurania, I-64100 Teramo (Italy); Freedman, W. L. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); and others

    2016-12-01

    New accurate and homogeneous optical UBVRI photometry has been obtained for variable stars in the Galactic globular cluster ω Cen (NGC 5139). We secured 8202 CCD images covering a time interval of 24 years and a sky area of 84 × 48 arcmin. The current data were complemented with data available in the literature and provided new, homogeneous pulsation parameters (mean magnitudes, luminosity amplitudes, periods) for 187 candidate ω Cen RR Lyrae (RRLs). Among them we have 101 RRc (first overtone) and 85 RRab (fundamental) variables, and a single candidate RRd (double-mode) variable. Candidate Blazhko RRLs show periods and colors that are intermediate between the RRc and RRab variables, suggesting that they are transitional objects. A comparison of the period distribution and the Bailey diagram indicates that RRLs in ω Cen show a long-period tail not present in typical Oosterhoff II (OoII) globulars. The RRLs in dwarf spheroidals and in ultra-faint dwarfs have properties between Oosterhoff intermediate and OoII clusters. Metallicity plays a key role in shaping the above evidence. These findings do not support the hypothesis that ω Cen is the core remnant of a spoiled dwarf galaxy. Using optical period–Wesenheit relations that are reddening-free and minimally dependent on metallicity we find a mean distance to ω Cen of 13.71 ± 0.08 ± 0.01 mag (semi-empirical and theoretical calibrations). Finally, we invert the I -band period–luminosity–metallicity relation to estimate individual RRLs’ metal abundances. The metallicity distribution agrees quite well with spectroscopic and photometric metallicity estimates available in the literature.

  8. Globular adiponectin induces a pro-inflammatory response in human astrocytic cells

    International Nuclear Information System (INIS)

    Wan, Zhongxiao; Mah, Dorrian; Simtchouk, Svetlana; Klegeris, Andis; Little, Jonathan P.

    2014-01-01

    Highlights: • Adiponectin receptors are expressed in human astrocytes. • Globular adiponectin induces secretion of IL-6 and MCP-1 from cultured astrocytes. • Adiponectin may play a pro-inflammatory role in astrocytes. - Abstract: Neuroinflammation, mediated in part by activated brain astrocytes, plays a critical role in the development of neurodegenerative disorders, including Alzheimer’s disease (AD). Adiponectin is the most abundant adipokine secreted from adipose tissue and has been reported to exert both anti- and pro-inflammatory effects in peripheral tissues; however, the effects of adiponectin on astrocytes remain unknown. Shifts in peripheral concentrations of adipokines, including adiponectin, could contribute to the observed link between midlife adiposity and increased AD risk. The aim of the present study was to characterize the effects of globular adiponectin (gAd) on pro-inflammatory cytokine mRNA expression and secretion in human U373 MG astrocytic cells and to explore the potential involvement of nuclear factor (NF)-κB, p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK) and phosphatidylinositide 3-kinases (PI3 K) signaling pathways in these processes. We demonstrated expression of adiponectin receptor 1 (adipoR1) and adipoR2 in U373 MG cells and primary human astrocytes. gAd induced secretion of interleukin (IL)-6 and monocyte chemoattractant protein (MCP)-1, and gene expression of IL-6, MCP-1, IL-1β and IL-8 in U373 MG cells. Using specific inhibitors, we found that NF-κB, p38MAPK and ERK1/2 pathways are involved in gAd-induced induction of cytokines with ERK1/2 contributing the most. These findings provide evidence that gAd may induce a pro-inflammatory phenotype in human astrocytes

  9. Limits on [O III] 5007 Emission from NGC 4472's Globular Clusters: Constraints on Planetary Nebulae and Ultraluminous Black Hole X-Ray Binaries in Globular Clusters

    Science.gov (United States)

    Peacock, Mark B.; Zepf, Stephen E.; Maccarone, Thomas J.

    2012-06-01

    We have searched for [O III] 5007 emission in high-resolution spectroscopic data from FLAMES/GIRAFFE Very Large Telescope observations of 174 massive globular clusters (GCs) in NGC 4472. No planetary nebulae (PNe) are observed in these clusters, constraining the number of PNe per bolometric luminosity, α evolution, if all stars produce PNe. Comparing our results to populations of PNe in galaxies, we find most galaxies have a higher α than these GCs (more PNe per bolometric luminosity—though some massive early-type galaxies do have similarly low α). The low α required in these GCs suggests that the number of PNe per bolometric luminosity does not increase strongly with decreasing mass or metallicity of the stellar population. We find no evidence for correlations between the presence of known GC PNe and either the presence of low-mass X-ray binaries (LMXBs) or the stellar interaction rates in the GCs. This, and the low α observed, suggests that the formation of PNe may not be enhanced in tight binary systems. These data do identify one [O III] emission feature, this is the (previously published) broad [O III] emission from the cluster RZ 2109. This emission is thought to originate from the LMXB in this cluster, which is accreting at super-Eddington rates. The absence of any similar [O III] emission from the other clusters favors the hypothesis that this source is a black hole LMXB, rather than a neutron star LMXB with significant geometric beaming of its X-ray emission.

  10. Deficiently extremal Gorenstein algebras

    Indian Academy of Sciences (India)

    Thus, R/I is a Cohen–. Macaulay algebra of Type 1, and hence R/I is Gorenstein. In view of Theorem 2.1, R/I is a nearly (or 1-deficient) extremal Gorenstein algebra. We now shall describe a result of Bruns and Hibi [1] which characterizes the Stanley–. Reisner rings having 2-pure but not 2-linear resolutions. Theorem 2.3.

  11. Religious Extremism in Pakistan

    Science.gov (United States)

    2014-12-01

    boarding and lodging in madrasas (religious schools).9 Some ROs also organize weddings and arrange for burials for the poor.10 Moreover, a few ROs...this will explain why 28 Sandler, “New Frontiers of Terrorism.” 29 Stephen Sharot, “Beyond Christianity : A Critique of the Rational Choice Theory...Religion and Terrorism: Christian Fundamentalism and Extremism,” Terrorism and Political Violence 22, no.3 (2010): 438‒456, http://dx.doi.org

  12. Imaging Under Extreme Conditions

    Science.gov (United States)

    2015-07-28

    have successfully reported, using direct imaging, the atomic-scale of molecular nanocrystals , the phase transition in metal-insulator transitions...the embryonic crystallization following extreme melting, the discovery of nanogating in quasi-1D materials, and the nature of interface electric ...are numerous, and we have successfully reported, using direct imaging, the atomic-scale of molecular nanocrystals , the phase transition in metal

  13. Extremes in nature

    CERN Document Server

    Salvadori, Gianfausto; Kottegoda, Nathabandu T

    2007-01-01

    This book is about the theoretical and practical aspects of the statistics of Extreme Events in Nature. Most importantly, this is the first text in which Copulas are introduced and used in Geophysics. Several topics are fully original, and show how standard models and calculations can be improved by exploiting the opportunities offered by Copulas. In addition, new quantities useful for design and risk assessment are introduced.

  14. USACE Extreme Sea levels

    Science.gov (United States)

    2014-03-14

    Pattiaratchi, C., Jensen, J., 2013. Estimating extreme water level probabilities: a comparison of the direct methods and recommendations for best practise ...will discuss with Jason Engle and determine the best way to proceed. • Kate will provide a copy of the storm climate analysis report that Andy Garcia...Gouldby, HR Wallingford) 12:50 to 2:00: Lunch 2:00 to 2:25: Best Practices and Analysis Methodologies (Jeff Melby, USACE) 2:25 to 3:10

  15. On extreme geomagnetic storms

    Directory of Open Access Journals (Sweden)

    Cid Consuelo

    2014-01-01

    Full Text Available Extreme geomagnetic storms are considered as one of the major natural hazards for technology-dependent society. Geomagnetic field disturbances can disrupt the operation of critical infrastructures relying on space-based assets, and can also result in terrestrial effects, such as the Quebec electrical disruption in 1989. Forecasting potential hazards is a matter of high priority, but considering large flares as the only criterion for early-warning systems has demonstrated to release a large amount of false alarms and misses. Moreover, the quantification of the severity of the geomagnetic disturbance at the terrestrial surface using indices as Dst cannot be considered as the best approach to give account of the damage in utilities. High temporal resolution local indices come out as a possible solution to this issue, as disturbances recorded at the terrestrial surface differ largely both in latitude and longitude. The recovery phase of extreme storms presents also some peculiar features which make it different from other less intense storms. This paper goes through all these issues related to extreme storms by analysing a few events, highlighting the March 1989 storm, related to the Quebec blackout, and the October 2003 event, when several transformers burnt out in South Africa.

  16. Noncommunicating Isolated Enteric Duplication Cyst in the ...

    African Journals Online (AJOL)

    Noncommunicating isolated enteric duplications in the abdomen are an extremely rare variant of enteric duplications with their own blood supply. We report a case of a noncommunicating isolated ileal duplication in a 10-month-old boy. He was admitted because of severe abdominal distension and developed irritability ...

  17. Extreme Programming Pocket Guide

    CERN Document Server

    Chromatic

    2003-01-01

    Extreme Programming (XP) is a radical new approach to software development that has been accepted quickly because its core practices--the need for constant testing, programming in pairs, inviting customer input, and the communal ownership of code--resonate with developers everywhere. Although many developers feel that XP is rooted in commonsense, its vastly different approach can bring challenges, frustrations, and constant demands on your patience. Unless you've got unlimited time (and who does these days?), you can't always stop to thumb through hundreds of pages to find the piece of info

  18. Metagenomics of extreme environments.

    Science.gov (United States)

    Cowan, D A; Ramond, J-B; Makhalanyane, T P; De Maayer, P

    2015-06-01

    Whether they are exposed to extremes of heat or cold, or buried deep beneath the Earth's surface, microorganisms have an uncanny ability to survive under these conditions. This ability to survive has fascinated scientists for nearly a century, but the recent development of metagenomics and 'omics' tools has allowed us to make huge leaps in understanding the remarkable complexity and versatility of extremophile communities. Here, in the context of the recently developed metagenomic tools, we discuss recent research on the community composition, adaptive strategies and biological functions of extremophiles. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Structural insights into the globular tails of the human type v myosins Myo5a, Myo5b, And Myo5c.

    Directory of Open Access Journals (Sweden)

    Hana Velvarska

    Full Text Available Vertebrate type V myosins (MyoV Myo5a, Myo5b, and Myo5c mediate transport of several different cargoes. All MyoV paralogs bind to cargo complexes mainly by their C-terminal globular domains. In absence of cargo, the globular domain of Myo5a inhibits its motor domain. Here, we report low-resolution SAXS models for the globular domains from human Myo5a, Myo5b, and Myo5c, which suggest very similar overall shapes of all three paralogs. We determined the crystal structures of globular domains from Myo5a and Myo5b, and provide a homology model for human Myo5c. When we docked the Myo5a crystal structure into a previously published electron microscopy density of the autoinhibited full-length Myo5a, only one domain orientation resulted in a good fit. This structural arrangement suggests the participation of additional region of the globular domain in autoinhibition. Quantification of the interaction of the Myo5a globular domain with its motor complex revealed a tight binding with dissociation half-life in the order of minutes, suggesting a rather slow transition between the active and inactive states.

  20. Training Simulator for Extreme Environments

    OpenAIRE

    Nazir, Salman; Manca, Davide; Komulainen, Tiina M.; Øvergård, Kjell Ivar

    2015-01-01

    - Current technological advancements have enabled the achievement of excellence in design of training simulators. This work highlights the challenges faced by operators in extreme environments and harsh conditions in an attempt to underpin the necessary features of extreme training simulators.

  1. Training Simulator for Extreme Environments

    OpenAIRE

    Nazir, Salman; Manca, Davide; Komulainen, Tiina M.; Øvergård, Kjell Ivar

    2015-01-01

    Current technological advancements have enabled the achievement of excellence in design of training simulators. This work highlights the challenges faced by operators in extreme environments and harsh conditions in an attempt to underpin the necessary features of extreme training simulators.

  2. VizieR Online Data Catalog: Globular and open clusters observed by SDSS/SEGUE (Morrison+, 2016)

    Science.gov (United States)

    Morrison, H. L.; Ma, Z.; Clem, J. L.; An, D.; Connor, T.; Schechtman-Rook, A.; Casagrande, L.; Rockosi, C.; Yanny, B.; Harding, P.; Beers, T. C.; Johnson, J. A.; Schneider, D. P.

    2018-03-01

    The SEGUE project observed a number of globular and open clusters for calibration purposes. For calibration of the red giants, we selected the globular clusters M92, M13 and M71 (spanning metallicities from -2.4 to -0.8) and the open clusters Be 29, NGC 7789 and NGC 6791, whose [Fe/H] values range from -0.4 to +0.4. In all but one case, the clusters are within the SDSS footprint and so ugriz photometry is available for the cluster stars. The SDSS cluster images were analyzed using DAOPHOT (Stetson 1987PASP...99..191S) by An et al. (2008ApJS..179..326A) because the SDSS photometric pipeline was not designed to handle crowded fields. (8 data files).

  3. High-resolution abundance analysis of red giants in the globular cluster NGC 6522

    Science.gov (United States)

    Barbuy, B.; Chiappini, C.; Cantelli, E.; Depagne, E.; Pignatari, M.; Hirschi, R.; Cescutti, G.; Ortolani, S.; Hill, V.; Zoccali, M.; Minniti, D.; Trevisan, M.; Bica, E.; Gómez, A.

    2014-10-01

    Context. The [Sr/Ba] and [Y/Ba] scatter observed in some galactic halo stars that are very metal-poor and in a few individual stars of the oldest known Milky Way globular cluster NGC 6522 have been interpreted as evidence of early enrichment by massive fast-rotating stars (spinstars). Because NGC 6522 is a bulge globular cluster, the suggestion was that not only the very-metal poor halo stars, but also bulge stars at [Fe/H] ~ -1 could be used as probes of the stellar nucleosynthesis signatures from the earlier generations of massive stars, but at much higher metallicity. For the bulge the suggestions were based on early spectra available for stars in NGC 6522, with a medium resolution of R ~ 22 000 and a moderate signal-to-noise ratio. Aims: The main purpose of this study is to re-analyse the NGC 6522 stars reported previously by using new high-resolution (R ~ 45 000) and high signal-to-noise spectra (S/N > 100). We aim at re-deriving their stellar parameters and elemental ratios, in particular the abundances of the neutron-capture s-process-dominated elements such as Sr, Y, Zr, La, and Ba, and of the r-element Eu. Methods: High-resolution spectra of four giants belonging to the bulge globular cluster NGC 6522 were obtained at the 8m VLT UT2-Kueyen telescope with the UVES spectrograph in FLAMES-UVES configuration. The spectroscopic parameters were derived based on the excitation and ionization equilibrium of Fe i and Fe ii. Results: Our analysis confirms a metallicity [Fe/H] = -0.95 ± 0.15 for NGC 6522 and the overabundance of the studied stars in Eu (with +0.2 < [Eu/Fe] < + 0.4) and alpha-elements O and Mg. The neutron-capture s-element-dominated Sr, Y, Zr, Ba, and La now show less pronounced variations from star to star. Enhancements are in the range 0.0 < [Sr/Fe] < +0.4, +0.23 < [Y/Fe] < +0.43, 0.0 < [Zr/Fe] < +0.4, 0.0 < [La/Fe] < +0.35, and 0.05 < [Ba/Fe] < +0.55. Conclusions: The very high overabundances of [Y/Fe] previously reported for the four studied

  4. VizieR Online Data Catalog: HST photometry of M31 globular clusters (Federici+, 2012)

    Science.gov (United States)

    Federici, L.; Cacciari, C.; Bellazzini, M.; Fusi Pecci, F.; Galleti, S.; Perina, S.

    2013-01-01

    Tables g58.dat, g108.dat, g105.dat, g219.dat, b468.dat, g1.dat, g64.dat, g87.dat, g119.dat, g287.dat, g302.dat, g11.dat, g33.dat, g76.dat, g312.dat, g319.dat, g322.dat present the photometry of the individual stars of 17 M31 globular clusters observed with the WFPC2 on board of the HST, employing the F555W/F814W filters (Fusi Pecci et al. 1996AJ....112.1461F (FFP96), Rich et al. 2005AJ....129.2670R (R05)). The data reduction has been performed using ROMAFOT (Buonanno et al. 1983A&A...126..278B), a multicomponent fitting package purposely adapted to handle HST data, that provides as output the magnitudes and the pixel positions of the detected sources. The CTE-corrected photometric data were converted to the Johnson-Cousins V,I magnitudes according to Holtzman et al (1995PASP..107..156H). Table g351.dat presents the photometry of the individual stars of the M31 globular cluster B405-G351 observed with the HST/COSTAR-corrected FOC + the F430W/F480LP filters. The data reduction has been performed using ROMAFOT; the photometric data were converted to the Johnson-Cousins system B,V magnitudes (see FFP96). Tables gc1.dat, gc2.dat, gc3.dat, gc5.dat, gc6.dat, gc7.dat, gc8.dat, gc9.dat, gc10.dat, gc4.dat, ec1.dat, ec2.dat, ec3.dat, ec4.dat present the photometry of the individual stars of 14 M31 globular clusters observed with the WFC/ACS on board of the HST + F435W/F606W filters (see Galleti et al., 2006ApJ...650L.107G; Mackey et al., 2007ApJ...655L..85M; Mackey et al., 2006ApJ...653L.105M). The data reduction has been performed using the ACS module of DOLPHOT, a point spread function-fitting package specifically devoted to the photometry of HST data, that provides as output the magnitudes and the pixel positions of the detected sources, and a number of quality parameters for a suitable sample selection. The tables present, for the ACS chip holding the cluster, all the stars with valid measurements in both passbands, global quality flag=1, crowding parameter 23.5,and noise

  5. VEGAS-SSS. II. Comparing the globular cluster systems in NGC 3115 and NGC 1399 using VEGAS and FDS survey data. The quest for a common genetic heritage of globular cluster systems

    Science.gov (United States)

    Cantiello, Michele; D'Abrusco, Raffaele; Spavone, Marilena; Paolillo, Maurizio; Capaccioli, Massimo; Limatola, Luca; Grado, Aniello; Iodice, Enrica; Raimondo, Gabriella; Napolitano, Nicola; Blakeslee, John P.; Brocato, Enzo; Forbes, Duncan A.; Hilker, Michael; Mieske, Steffen; Peletier, Reynier; van de Ven, Glenn; Schipani, Pietro

    2018-04-01

    We analyze the globular cluster (GC) systems in two very different galaxies, NGC 3115 and NGC 1399. With the papers of this series, we aim at highlighting common and different properties in the GC systems in galaxies covering a wide range of parameter space. We compare the GCs in NGC 3115 and NGC 1399 as derived from the analysis of one square degree u-, g-, and i-band images taken with the VST telescope as part of the VST early-type galaxy survey (VEGAS) and Fornax deep survey (FDS). We selected GC candidates using as reference the morpho-photometric and color properties of confirmed GCs. The surface density maps of GCs in NGC 3115 reveal a morphology similar to the light profile of field stars; the same is true when blue and red GCs are taken separately. The GC maps for NGC 1399 are richer in structure and confirm the existence of an intra-cluster GC component. We confirm the presence of a spatial offset in the NGC 1399 GC centroid and find that the centroid of the GCs for NGC 3115 coincides well with the galaxy center. Both GC systems show unambiguous color bimodality in (g - i) and (u - i); the color-color relations of the two GC systems are slightly different with NGC 3115 appearing more linear than NGC 1399. The azimuthal average of the radial density profiles in both galaxies reveals a larger spatial extent for the total GCs population with respect to the galaxy surface brightness profile. For both galaxies, the red GCs have radial density profiles compatible with the galaxy light profile, while the radial profiles for blue GCs are shallower. As for the specific frequency of GCs, SN, we find it is a factor of two higher in NGC 1399 than for NGC 3115; this is mainly the result of extra blue GCs. By inspecting the radial behavior of the specific frequency, SN(extremely different host environments, the red GCs in both cases appear

  6. Chemical Compositions of Stars in the Globular Cluster NGC 3201: Tracers of Multi-Epoch Star Formation

    Science.gov (United States)

    Simmerer, Jennifer A.; Ivans, I. I.; Filler, D.

    2012-01-01

    The retrograde halo globular cluster NGC 3201 contains stars of substantially different iron abundance ([Fe/H]), a property that puts it at odds with the vast majority of the Galactic cluster system. Though its unusual orbit prompted speculation that NGC 3201 was the remnant of a captured object, much like the multi-metallicity globular cluster Omega Centauri, NGC 3201 is much less massive than Omega Centauri and all of the other halo globular clusters that have internal metallicity variations. We present the abundances of 21 elements in 24 red giant branch stars in NGC 3201 based on high-resolution (R 40,000), high signal-to-noise (S/N 70) spectra. We find that the detailed abundance pattern of NGC 3201 is unique amongst multi-metallicity halo clusters. Unlike M22, Omega Centauri, and NGC 1851, neither metal-poor nor metal-rich stars show any evidence of s-process enrichment (a product of the advanced evolution of low- and intermediate-mass stars). We find that while Na, O, and Al vary from star to star as is typical in globular clusters, there is no systematic difference between the abundance pattern in the metal-poor cluster stars and that of the metal-rich cluster stars. Furthermore, we find that the metallicity variations in NGC 3201 are independent of the well-known Na-O anticorrelation, which separates it from every other multi-metallicity cluster. In the context of a multi-episode star formation model, this implies that NGC 3201 began life with the [Fe/H] variations we measure now.

  7. Hydra Observations of Aluminum Abundances in the Red Giants of the Globular Clusters M80 and NGC 6752

    OpenAIRE

    Cavallo, Robert M.; Suntzeff, Nicholas B.; Pilachowski, Catherine A.

    2004-01-01

    Aluminum and other metal abundances were determined in 21 red giants in the globular clusters NGC 6752 and M80 as part of a larger study to determine whether the aluminum distribution on the red giant branch is related to the second parameter effect that causes clusters of similar metallicity to display different horizontal branch morphologies. The observations were obtained of the Al I lines near 6700 Angstroms with the CTIO Blanco 4-m telescope and Hydra multi-object spectrograph. The spect...

  8. THE HST/ACS COMA CLUSTER SURVEY. IV. INTERGALACTIC GLOBULAR CLUSTERS AND THE MASSIVE GLOBULAR CLUSTER SYSTEM AT THE CORE OF THE COMA GALAXY CLUSTER

    International Nuclear Information System (INIS)

    Peng, Eric W.; Ferguson, Henry C.; Goudfrooij, Paul; Hammer, Derek; Lucey, John R.; Marzke, Ronald O.; Puzia, Thomas H.; Carter, David; Balcells, Marc; Bridges, Terry; Chiboucas, Kristin; Del Burgo, Carlos; Graham, Alister W.; Guzman, Rafael; Hudson, Michael J.; Matkovic, Ana

    2011-01-01

    Intracluster stellar populations are a natural result of tidal interactions in galaxy clusters. Measuring these populations is difficult, but important for understanding the assembly of the most massive galaxies. The Coma cluster of galaxies is one of the nearest truly massive galaxy clusters and is host to a correspondingly large system of globular clusters (GCs). We use imaging from the HST/ACS Coma Cluster Survey to present the first definitive detection of a large population of intracluster GCs (IGCs) that fills the Coma cluster core and is not associated with individual galaxies. The GC surface density profile around the central massive elliptical galaxy, NGC 4874, is dominated at large radii by a population of IGCs that extend to the limit of our data (R +4000 -5000 (systematic) IGCs out to this radius, and that they make up ∼70% of the central GC system, making this the largest GC system in the nearby universe. Even including the GC systems of other cluster galaxies, the IGCs still make up ∼30%-45% of the GCs in the cluster core. Observational limits from previous studies of the intracluster light (ICL) suggest that the IGC population has a high specific frequency. If the IGC population has a specific frequency similar to high-S N dwarf galaxies, then the ICL has a mean surface brightness of μ V ∼ 27 mag arcsec -2 and a total stellar mass of roughly 10 12 M sun within the cluster core. The ICL makes up approximately half of the stellar luminosity and one-third of the stellar mass of the central (NGC 4874+ICL) system. The color distribution of the IGC population is bimodal, with blue, metal-poor GCs outnumbering red, metal-rich GCs by a ratio of 4:1. The inner GCs associated with NGC 4874 also have a bimodal distribution in color, but with a redder metal-poor population. The fraction of red IGCs (20%), and the red color of those GCs, implies that IGCs can originate from the halos of relatively massive, L* galaxies, and not solely from the disruption of

  9. Solar extreme events

    Science.gov (United States)

    Hudson, Hugh S.

    2015-08-01

    Solar flares and CMEs have a broad range of magnitudes. This review discusses the possibility of “extreme events,” defined as those with magnitudes greater than have been seen in the existing historical record. For most quantitative measures, this direct information does not extend more than a century and a half into the recent past. The magnitude distributions (occurrence frequencies) of solar events (flares/CMEs) typically decrease with the parameter measured or inferred (peak flux, mass, energy etc. Flare radiation fluxes tend to follow a power law slightly flatter than S-2, where S represents a peak flux; solar particle events (SPEs) follow a still flatter power law up to a limiting magnitude, and then appear to roll over to a steeper distribution, which may take an exponential form or follow a broken power law. This inference comes from the terrestrial 14C record and from the depth dependence of various radioisotope proxies in the lunar regolith and in meteorites. Recently major new observational results have impacted our use of the relatively limited historical record in new ways: the detection of actual events in the 14C tree-ring records, and the systematic observations of flares and “superflares” by the Kepler spacecraft. I discuss how these new findings may affect our understanding of the distribution function expected for extreme solar events.

  10. Chemical Complexity in the Eu-enhanced Monometallic Globular NGC 5986

    Science.gov (United States)

    Johnson, Christian I.; Caldwell, Nelson; Rich, R. Michael; Mateo, Mario; Bailey, John I., III; Olszewski, Edward W.; Walker, Matthew G.

    2017-06-01

    NGC 5986 is a poorly studied but relatively massive Galactic globular cluster that shares several physical and morphological characteristics with “iron-complex” clusters known to exhibit significant metallicity and heavy-element dispersions. In order to determine whether NGC 5986 joins the iron-complex cluster class, we investigated the chemical composition of 25 red giant branch and asymptotic giant branch cluster stars using high-resolution spectra obtained with the Magellan-M2FS instrument. Cluster membership was verified using a combination of radial velocity and [Fe/H] measurements, and we found the cluster to have a mean heliocentric radial velocity of +99.76 km s-1 (σ = 7.44 km s-1). We derived a mean metallicity of [Fe/H] = -1.54 dex (σ = 0.08 dex), but the cluster’s small dispersion in [Fe/H] and low [La/Eu] abundance preclude it from being an iron-complex cluster. NGC 5986 has =+0.76 {dex} (σ = 0.08 dex), which is among the highest ratios detected in a Galactic cluster, but the small [Eu/Fe] dispersion is puzzling because such high values near [Fe/H] ˜ -1.5 are typically only found in dwarf galaxies exhibiting large [Eu/Fe] variations. NGC 5986 exhibits classical globular cluster characteristics, such as uniformly enhanced [α/Fe] ratios, a small dispersion in Fe-peak abundances, and (anti)correlated light-element variations. Similar to NGC 2808, we find evidence that NGC 5986 may host at least four to five populations with distinct light-element compositions, and the presence of a clear Mg-Al anticorrelation along with an Al-Si correlation suggests that the cluster gas experienced processing at temperatures ≳65-70 MK. However, the current data do not support burning temperatures exceeding ˜100 MK. We find some evidence that the first- and second-generation stars in NGC 5986 may be fully spatially mixed, which could indicate that the cluster has lost a significant fraction of its original mass. This paper includes data gathered with the 6.5 m

  11. Primordial main equence binary stars in the globular cluster M71

    Science.gov (United States)

    Yan, Lin; Mateo, Mario

    1994-01-01

    We report the identification of five short-period variables near the center of the metal-rich globular cluster M71. Our observations consist of multiepoch VI charge coupled device (CCD) images centered on the cluster and covering a 6.3 min x 6.3 min field. Four of these variables are contact eclipsing binaries with periods between 0.35 and 0.41 days; one is a detached or semidetached eclipsing binary with a period of 0.56 days. Two of the variables were first identified as possible eclipsing binaries in an earlier survey by Hodder et al. (1992). We have used a variety of arguments to conclude that all five binary stars are probable members of M71, a result that is consistent with the low number (0.15) of short-period field binaries expected along this line of sight. Based on a simple model of how contact binaries evolve from initially detached binaries, we have determined a lower limit of 1.3% on the frequency of primordial binaries in M71 with initial orbital periods in the range 2.5 - 5 days. This implies that the overall primordial binary frequency, f, is 22(sup +26)(sub -12)% assuming df/d log P = const ( the 'flat' distribution), or f = 57(sup +15)(sub -8)% for df/d log P = 0.032 log P + const as observed for G-dwarf binaries in the solar neighborhood (the 'sloped' distribution). Both estimates of f correspond to binaries with initial periods shorter than 800 yr since any longer-period binaries would have been disrupted over the lifetime of the cluster. Our short-period binary frequency is in excellent agreement with the observed frequency of red-giant binaries observed in globulars if we adopt the flat distribution. For the sloped distribution, our results significantly overestimate the number of red-giant binaries. All of the short-period M71 binaries lie within 1 mag of the luminosity of the cluster turnoff in the color-magnitude diagram despite the fact we should have easily detected similar eclipsing binaries 2 - 2.5 mag fainter than this. We discuss the

  12. Peculiarities of dynamic evaluation of globular formation outlines of the lungs with multislice computed tomography

    Directory of Open Access Journals (Sweden)

    Vladimir G. Kolmogorov

    2017-01-01

    Full Text Available Background. Visualization of infiltration in lung tissue surrounding the globular formation of the lungs (GFL determined by X-ray is one of the important points in the differential diagnosis of primary lung cancer, specific and non-specific inflammatory processes. At CT gauge body phantoms test facilities are widely used for evaluating the performance of scanners that allow the evaluation of scanner characteristics : noise, contrast sensitivity, positioning accuracy, stiffness of the radiation beam, the layer thickness, spatial resolution, etc.Aim. To develop a methodology for assessing the GFL outlines of the dynamics of multislice computed tomography (MSCT by selecting the optimal image processing algorithms.Materials and methods. The visual analysis of two- component physical model images of the electronic window level (WL and electronic window width (WW was installed on the basis of the best conditions for studying a specific group of tissues. In the case of indistinct, poorly defined outlines of globular formations, visual assessment is operator-dependent and requires development and application of quantitative methods of analysis. For a quantitative description of the outlines of the image of the GFL model, a vector in a polar coordinate system coming from the center of the figure mass bounded by the outline was used. The following outline complexity measures were adopted: modified Shannon information entropy H(S(k for k harmonics of the normalized spectral power density S(k of the length of oscillation of loop radius vector R(n; the number of local maxima L of signature radius vector R(n; the maximum value of the normalized power spectral density S(k; product (multiplicity of the entropy H(S and the number of local maxima L.Results. “Multiplicity”, “the number of local maxima” of the outline depend on the GFL geometric dimensions and cannot be used for diagnosis without first normalizing for GFL outline length. The parameters

  13. SPACE VELOCITIES OF SOUTHERN GLOBULAR CLUSTERS. VII. NGC 6397, NGC 6626 (M28), AND NGC 6656 (M22)

    Energy Technology Data Exchange (ETDEWEB)

    Casetti-Dinescu, Dana I.; Girard, Terrence M.; Van Altena, William F. [Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Jilkova, Lucie [Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotlarska 2, CZ-61137 Brno (Czech Republic); Podesta, Federico; Lopez, Carlos E., E-mail: dana.casetti@yale.edu, E-mail: terry.girard@yale.edu, E-mail: william.vanaltena@yale.edu, E-mail: jilkoval@physics.muni.cz [Universidad National de San Juan, Observatorio Astronomico ' ' Felix Aguilar' ' and Yale Southern Observatory, Chimbas, 5413 San Juan (Argentina)

    2013-08-01

    We have measured the absolute proper motions of globular clusters NGC 6397, NGC 6626 (M22), and NGC 6656 (M28) as part of our ongoing Southern Proper-Motion Program. The reference system is the ICRS via Hipparcos stars for these three low-Galactic-latitude clusters. Formal errors range between {approx}0.3 and 0.7 mas yr{sup -1}. Notable is the result for NGC 6397, which differs by 2.5 mas yr{sup -1} from two Hubble Space Telescope determinations while agreeing with previous ground-based ones. We determine orbits for all three clusters in an axisymmetric and barred model of the Galaxy and discuss these in the context of globular-cluster formation. M22 is a well-known cluster with an iron abundance spread; such clusters are now believed to have formed in massive parent systems that can retain ejecta of core-collapsed supernovae. We find that the five currently accepted globular clusters with iron/calcium abundance spread show orbits unrelated to each other, thus suggesting at least five independent, massive progenitors that have contributed to the build-up of the Milky-Way halo.

  14. The most metal-poor Galactic globular cluster: the first spectroscopic observations of ESO280-SC06

    Science.gov (United States)

    Simpson, Jeffrey D.

    2018-04-01

    We present the first spectroscopic observations of the very metal-poor Milky Way globular cluster ESO280-SC06. Using spectra acquired with the 2dF/AAOmega spectrograph on the Anglo-Australian Telescope, we have identified 13 members of the cluster, and estimate from their infrared calcium triplet lines that the cluster has a metallicity of [Fe/H]={-2.48}^{+0.06}_{-0.11}. This would make it the most metal-poor globular cluster known in the Milky Way. This result was verified with comparisons to three other metal-poor globular clusters that had been observed and analyzed in the same manner. We also present new photometry of the cluster from EFOSC2 and SkyMapper and confirm that the cluster is located 22.9 ± 2.1 kpc from the Sun and 15.2 ± 2.1 kpc from the Galactic centre, and has a radial velocity of 92.5 + 2.4-1.6 km s-1. These new data finds the cluster to have a radius about half that previously estimated, and we find that the cluster has a dynamical mass of the cluster of (12 ± 2) × 103 M⊙. Unfortunately, we lack reliable proper motions to fully characterize its orbit about the Galaxy. Intriguingly, the photometry suggests that the cluster lacks a well-populated horizontal branch, something that has not been observed in a cluster so ancient or metal-poor.

  15. Core-multishell globular oxidation in a new TiAlNbCr alloy at high temperatures.

    Science.gov (United States)

    Tang, S Q; Qu, S J; Feng, A H; Feng, C; Shen, J; Chen, D L

    2017-06-14

    Oxidation resistance is one of key properties of titanium aluminide (TiAl) based alloys for high-temperature applications such as in advanced aero-engines and gas turbines. A new TiAlNbCr alloy with micro-addition of yttrium has been developed, but its oxidation behavior is unknown. To provide some fundamental insights, high-temperature oxidation characteristics of this alloy are examined via scanning electron microscopy, transmission electron microscopy, electron probe microanalysis, and X-ray diffraction. We show that distinctive core-multishell globular oxidation and "daisy" flower-like oxidation occur exclusively around Y 2 O 3 particles. Globular oxides exhibit multi-layered Y 2 O 3 /TiO 2 /Al 2 O 3 -rich/TiO 2 -rich shell structures from the inside to outside. Flower-like inner oxides consist of core Y 2 O 3 particles surrounded by divergent Al 2 O 3 and oxygen-rich α 2 -Ti 3 Al in the near-scale substrate. As the scale-substrate interface moves inward, the inner oxide structures suffer deeper oxidation and transform into the globular oxide structures. Our results demonstrate that the unique oxidation characteristics and the understanding of formation mechanisms pave the way for the exploration and development of advanced oxidation-resistant TiAl-based materials.

  16. Oligotrophic bacteria isolated from clinical materials.

    OpenAIRE

    Tada, Y; Ihmori, M; Yamaguchi, J

    1995-01-01

    Oligotrophic bacteria (oligotrophs) are microorganisms that grow in extremely nutritionally deficient conditions in which the concentrations of organic substances are low. Many oligotrophic bacteria were isolated from clinical materials including urine, sputum, swabbings of the throat, vaginal discharges, and others. Seventy-seven strains of oligotrophic bacteria from 871 samples of clinical material were isolated. A relatively higher frequency of isolation of oligotrophic bacteria was shown ...

  17. Isolated trochlear nerve palsy with midbrain hemorrhage

    Directory of Open Access Journals (Sweden)

    Raghavendra S

    2010-01-01

    Full Text Available Midbrain hemorrhage causing isolated fourth nerve palsy is extremely rare. Idiopathic, traumatic and congenital abnormalities are the most common causes of fourth nerve palsy. We report acute isolated fourth nerve palsy in an 18-year-old lady due to a midbrain hemorrhage probably due to a midbrain cavernoma. The case highlights the need for neuroimaging in selected cases of isolated trochlear nerve palsy.

  18. Formation of Black Hole X-Ray Binaries with Non-degenerate Donors in Globular Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Ivanova, Natalia; Rocha, Cassio A. da; Van, Kenny X.; Nandez, Jose L. A., E-mail: nata.ivanova@ualberta.ca [Department of Physics, University of Alberta, Edmonton, AB T6G 2E7 (Canada)

    2017-07-10

    In this Letter, we propose a formation channel for low-mass X-ray binaries with black hole accretors and non-degenerate donors via grazing tidal encounters with subgiants. We estimate that in a typically dense globular cluster with a core density of 10{sup 5} stars pc{sup −3}, the formation rates are about one binary per Gyr per 50–100 retained black holes. The donors—stripped subgiants—will be strongly underluminous when compared to subgiant or giant branch stars of the same colors. The products of tidal stripping are underluminous by at least one magnitude for several hundred million years when compared to normal stars of the same color, and differ from underluminous red stars that could be produced by non-catastrophic mass transfer in an ordinary binary. The dynamically formed binaries become quiescent LMXBs, with lifetimes of about a Gyr. The expected number of X-ray binaries is one per 50–200 retained black holes, while the expected number of strongly underluminous subsubgiant is about half this. The presence of strongly underluminous stars in a GC may be indicative of the presence of black holes.

  19. Multiple Populations in the Old and Massive Small Magellanic Cloud Globular Cluster NGC 121

    Science.gov (United States)

    Dalessandro, E.; Lapenna, E.; Mucciarelli, A.; Origlia, L.; Ferraro, F. R.; Lanzoni, B.

    2016-10-01

    We used a combination of optical and near-UV Hubble Space Telescope photometry and FLAMES/ESO-VLT high-resolution spectroscopy to characterize the stellar content of the old and massive globular cluster (GC) NGC 121 in the Small Magellanic Cloud (SMC). We report on the detection of multiple stellar populations, the first case in the SMC stellar cluster system. This result enforces the emerging scenario in which the presence of multiple stellar populations is a distinctive-feature of old and massive GCs regardless of the environment, as far as the light-element distribution is concerned. We find that second-generation (SG) stars are more centrally concentrated than first-generation (FG) ones. More interestingly, at odds with what is typically observed in Galactic GCs, we find that NGC 121 is the only cluster so far to be dominated by FG stars that account for more than 65% of the total cluster mass. In the framework where GCs were born with 90%-95% of FG stars, this observational finding would suggest that either NGC 121 experienced a milder stellar mass-loss with respect to Galactic GCs or it formed a smaller fraction of SG stars. Based on observations collected with NASA/ESA HST, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555 and collected at the ESO-VLT under the program 086.D-0665.

  20. On the physical nature of globular cluster candidates in the Milky Way bulge

    Science.gov (United States)

    Piatti, A. E.

    2018-03-01

    We present results from 2MASS JKs photometry on the physical reality of recently reported globular cluster (GC) candidates in the Milky Way (MW) bulge. We relied our analysis on photometric membership probabilities that allowed us to distinguish real stellar aggregates from the composite field star population. When building colour-magnitude diagrams and stellar density maps for stars at different membership probability levels, the genuine GC candidate populations are clearly highlighted. We then used the tip of the red giant branch (RGB) as distance estimator, resulting heliocentric distances that place many of the objects in regions near of the MW bulge where no GC had been previously recognised. Some few GC candidates resulted to be MW halo/disc objects. Metallicities estimated from the standard RGB method are in agreement with the values expected according to the position of the GC candidates in the Galaxy. Finally, we derived from the first time their structural parameters. We found that the studied objects have core, half-light and tidal radii in the ranges spanned by the population of known MW GCs. Their internal dynamical evolutionary stages will be described properly when their masses are estimated.

  1. On the kinematic separation of field and cluster stars across the bulge globular NGC 6528

    Energy Technology Data Exchange (ETDEWEB)

    Lagioia, E. P.; Bono, G.; Buonanno, R. [Dipartimento di Fisica, Università degli Studi di Roma-Tor Vergata, via della Ricerca Scientifica 1, I-00133 Roma (Italy); Milone, A. P. [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT 2611 (Australia); Stetson, P. B. [Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Prada Moroni, P. G. [Dipartimento di Fisica, Università di Pisa, I-56127 Pisa (Italy); Dall' Ora, M. [INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy); Aparicio, A.; Monelli, M. [Instituto de Astrofìsica de Canarias, E-38200 La Laguna, Tenerife, Canary Islands (Spain); Calamida, A.; Ferraro, I.; Iannicola, G. [INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00044 Monte Porzio Catone (Italy); Gilmozzi, R. [European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching (Germany); Matsunaga, N. [Kiso Observatory, Institute of Astronomy, School of Science, The University of Tokyo, 10762-30, Mitake, Kiso-machi, Kiso-gun, 3 Nagano 97-0101 (Japan); Walker, A., E-mail: eplagioia@roma2.infn.it [Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena (Chile)

    2014-02-10

    We present deep and precise multi-band photometry of the Galactic bulge globular cluster NGC 6528. The current data set includes optical and near-infrared images collected with ACS/WFC, WFC3/UVIS, and WFC3/IR on board the Hubble Space Telescope. The images cover a time interval of almost 10 yr, and we have been able to carry out a proper-motion separation between cluster and field stars. We performed a detailed comparison in the m {sub F814W}, m {sub F606W} – m {sub F814W} color-magnitude diagram with two empirical calibrators observed in the same bands. We found that NGC 6528 is coeval with and more metal-rich than 47 Tuc. Moreover, it appears older and more metal-poor than the super-metal-rich open cluster NGC 6791. The current evidence is supported by several diagnostics (red horizontal branch, red giant branch bump, shape of the sub-giant branch, slope of the main sequence) that are minimally affected by uncertainties in reddening and distance. We fit the optical observations with theoretical isochrones based on a scaled-solar chemical mixture and found an age of 11 ± 1 Gyr and an iron abundance slightly above solar ([Fe/H] = +0.20). The iron abundance and the old cluster age further support the recent spectroscopic findings suggesting a rapid chemical enrichment of the Galactic bulge.

  2. Magnesium isotopes: a tool to understand self-enrichment in Globular Clusters

    Science.gov (United States)

    Ventura, P.; D'Antona, F.; Imbriani, G.; Di Criscienzo, M.; Dell'Agli, F.; Tailo, M.

    2018-03-01

    A critical issue in the asymptotic giant branch (AGB) self-enrichment scenario for the formation of multiple populations in Globular Clusters (GCs) is the inability to reproduce the magnesium isotopic ratios, despite the model in principle can account for the depletion of magnesium. In this work we analyze how the uncertainties on the various p-capture cross sections affect the results related to the magnesium content of the ejecta of AGB stars. The observed distribution of the magnesium isotopes and of the overall Mg-Al trend in M13 and NGC 6752 are successfully reproduced when the proton-capture rate by 25Mg at the temperatures ˜100 MK, in particular the 25Mg(p, γ)26Alm channel, is enhanced by a factor ˜3 with respect to the most recent experimental determinations. This assumption also allows to reproduce the full extent of the Mg spread and the Mg-Si anticorrelation observed in NGC 2419. The uncertainties in the rate of the 25Mg(p, γ)26Alm reaction at the temperatures of interest here leave space for our assumption and we suggest that new experimental measurements are needed to settle this problem. We also discuss the competitive model based on the super massive star nucleosynthesis.

  3. Spatially Resolved Spectroscopy of the Globular Cluster RZ 2109 and the Nature of its Black Hole

    Science.gov (United States)

    Peacock, Mark B.; Zepf, Stephen E.; Kundu, Arunav; Maccarone, Thomas J.; Rhode, Katherine L.; Salzer, John J.; Waters, Christopher Z.; Ciardullo, Robin; Gronwall, Caryl; Stern, Daniel

    2012-11-01

    We present optical Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) spectroscopy of RZ 2109, a globular cluster (GC) in the elliptical galaxy NGC 4472. This GC is notable for hosting an ultraluminous X-ray source as well as associated strong and broad [O III] λλ4959, 5007 emission. We show that the HST/STIS spectroscopy spatially resolves the [O III] emission in RZ 2109. While we are unable to make a precise determination of the morphology of the emission-line nebula, the best-fitting models all require that the [O III] λ5007 emission has a half-light radius in the range 3-7 pc. The extended nature of the [O III] λ5007 emission is inconsistent with published models that invoke an intermediate-mass black hole origin. It is also inconsistent with the ionization of ejecta from a nova in the cluster. The spatial scale of the nebula could be produced via the photoionization of a strong wind driven from a stellar mass black hole accreting at roughly its Eddington rate. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

  4. SPATIALLY RESOLVED SPECTROSCOPY OF THE GLOBULAR CLUSTER RZ 2109 AND THE NATURE OF ITS BLACK HOLE

    Energy Technology Data Exchange (ETDEWEB)

    Peacock, Mark B.; Zepf, Stephen E. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Kundu, Arunav [Eureka Scientific, Inc., 2452 Delmer Street, Suite 100 Oakland, CA 94602 (United States); Maccarone, Thomas J. [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Rhode, Katherine L.; Salzer, John J. [Department of Astronomy, Indiana University, Bloomington, IN 47405 (United States); Waters, Christopher Z. [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Ciardullo, Robin; Gronwall, Caryl [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Stern, Daniel, E-mail: mpeacock@msu.edu [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2012-11-10

    We present optical Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) spectroscopy of RZ 2109, a globular cluster (GC) in the elliptical galaxy NGC 4472. This GC is notable for hosting an ultraluminous X-ray source as well as associated strong and broad [O III] {lambda}{lambda}4959, 5007 emission. We show that the HST/STIS spectroscopy spatially resolves the [O III] emission in RZ 2109. While we are unable to make a precise determination of the morphology of the emission-line nebula, the best-fitting models all require that the [O III] {lambda}5007 emission has a half-light radius in the range 3-7 pc. The extended nature of the [O III] {lambda}5007 emission is inconsistent with published models that invoke an intermediate-mass black hole origin. It is also inconsistent with the ionization of ejecta from a nova in the cluster. The spatial scale of the nebula could be produced via the photoionization of a strong wind driven from a stellar mass black hole accreting at roughly its Eddington rate.

  5. Globular cluster formation and evolution in the context of cosmological galaxy assembly: open questions

    Science.gov (United States)

    Forbes, Duncan A.; Bastian, Nate; Gieles, Mark; Crain, Robert A.; Kruijssen, J. M. Diederik; Larsen, Søren S.; Ploeckinger, Sylvia; Agertz, Oscar; Trenti, Michele; Ferguson, Annette M. N.; Pfeffer, Joel; Gnedin, Oleg Y.

    2018-02-01

    We discuss some of the key open questions regarding the formation and evolution of globular clusters (GCs) during galaxy formation and assembly within a cosmological framework. The current state of the art for both observations and simulations is described, and we briefly mention directions for future research. The oldest GCs have ages greater than or equal to 12.5 Gyr and formed around the time of reionization. Resolved colour-magnitude diagrams of Milky Way GCs and direct imaging of lensed proto-GCs at z˜6 with the James Webb Space Telescope (JWST) promise further insight. GCs are known to host multiple populations of stars with variations in their chemical abundances. Recently, such multiple populations have been detected in ˜2 Gyr old compact, massive star clusters. This suggests a common, single pathway for the formation of GCs at high and low redshift. The shape of the initial mass function for GCs remains unknown; however, for massive galaxies a power-law mass function is favoured. Significant progress has been made recently modelling GC formation in the context of galaxy formation, with success in reproducing many of the observed GC-galaxy scaling relations.

  6. Na-O abundances in M53: A Mostly First Generation Globular Cluster

    Science.gov (United States)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

    2016-01-01

    We present the Fe, Ca, Ti, Ni, Ba, Na, and O abundances for a sample of 53 red giant branch (RGB) stars in the globular cluster (GC) NGC 5024 (M53). The abundances were measured from high signal-to-noise medium resolution spectra collected with the Hydra multi-object spectrograph on the WIYN 3.5- meter telescope. M53 is of interest because previous studies based on the morphology of the cluster's horizontal branch suggested that it might be composed primarily of first generation (FG) stars and differ from the majority of other GCs withmultiple populations, which have been found to be dominated by second generation (SG) stars. Our sample has an average [Fe/H] = -2.07 with a standard deviation of 0.07 dex. This value is consistent with previouslypublished results. The alpha-element abundances in our sample are also consistent with the trends seen in Milky Way halo stars at similar metallicities, with enhanced [Ca/Fe] and [Ti/Fe] relative to solar. We find thatthe Na-O anti-correlation is not as extended as other GCs with similarly high masses. The fraction of SG to FG stars in our sample is approximately 1:3 and the SG is more centrally concentrated. These findings further support that M53 might be a mostly FG cluster and could give further insight into how GCs formed the light element abundance patterns we observe in them today.

  7. Spectra of globular clusters in the Sombrero galaxy: evidence for spectroscopic metallicity bimodality

    Science.gov (United States)

    Alves-Brito, Alan; Hau, George K. T.; Forbes, Duncan A.; Spitler, Lee R.; Strader, Jay; Brodie, Jean P.; Rhode, Katherine L.

    2011-11-01

    We present a large sample of over 200 integrated-light spectra of confirmed globular clusters (GCs) associated with the Sombrero (M104) galaxy taken with the Deep Imaging Multi-Object Spectrograph (DEIMOS) instrument on the Keck telescope. A significant fraction of the spectra have signal-to-noise ratio levels high enough to allow measurements of GC metallicities using the method of Brodie & Huchra. We find a distribution of spectroscopic metallicities in the range -2.2 < [Fe/H] < +0.1 that is bimodal, with peaks at [Fe/H]˜-1.4 and -0.6. Thus, the GC system of the Sombrero galaxy, like a few other galaxies now studied in detail, reveals a bimodal spectroscopic metallicity distribution supporting the long-held belief that colour bimodality reflects two metallicity subpopulations. This further suggests that the transformation from optical colour to metallicity for old stellar populations, such as GCs, is not strongly non-linear. We also explore the radial and magnitude distribution with metallicity for GC subpopulations but small number statistics prevent any clear trends in these distributions. Based on observations obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration.

  8. SOLAR-LIKE OSCILLATIONS IN A METAL-POOR GLOBULAR CLUSTER WITH THE HUBBLE SPACE TELESCOPE

    International Nuclear Information System (INIS)

    Stello, Dennis; Gilliland, Ronald L.

    2009-01-01

    We present analyses of variability in the red giant stars in the metal-poor globular cluster NGC 6397, based on data obtained with the Hubble Space Telescope. We use a nonstandard data reduction approach to turn a 23 day observing run originally aimed at imaging the white dwarf population, into time-series photometry of the cluster's highly saturated red giant stars. With this technique we obtain noise levels in the final power spectra down to 50 parts per million, which allows us to search for low-amplitude solar-like oscillations. We compare the observed excess power seen in the power spectra with estimates of the typical frequency range, frequency spacing, and amplitude from scaling the solar oscillations. We see evidence that the detected variability is consistent with solar-like oscillations in at least one and perhaps up to four stars. With metallicities 2 orders of magnitude lower than those of the Sun, these stars present so far the best evidence of solar-like oscillations in such a low-metallicity environment.

  9. The Mystery of Globular Clusters: Uncovering the Complexities of Their Evolution

    Science.gov (United States)

    O'Malley, Erin Marie

    In recent years, evidence has grown for the existence of multiple stellar populations in globular clusters (GCs). However, questions remain regarding the nature of these populations. Photometric observations clearly show discrete populations while spectroscopic observations seem to show a continuous spread. This dissertation provides steps to better understanding GCs and the complexities associated with their evolution. Calibration of stellar evolution models at low metallicity is necessary for comparison to GCs. Accurate abundances of metal-poor subdwarfs are determined and used in this calibration. A Monte Carlo analysis is then performed in order to determine accurate distances, absolute ages, and integrated orbital trajectories for 24 GCs. These results are of critical importance as they not only incorporate the observational uncertainty, but also the uncertainty incurred by the models themselves. Lastly, high resolution spectra of three GCs (NGC 6681, NGC 6584 and NGC 7099) are obtained for a detailed abundance analysis of red giant branch stars. The high resolution and signal-to-noise achieved in these observations allows for the discovery of a statistically significant Na-O anticorrelation in all three clusters, the populations of which agree with those from photometric observations. Although we cannot determine precisely the nature of the polluters that were the predecessors to the enhanced populations, we do know that both s-process and r-process mechanisms contributed to the evolution and these results can be used to help constrain future models of GC polluter candidates.

  10. A stochastic finite element model for the dynamics of globular macromolecules

    Science.gov (United States)

    Oliver, Robin C.; Read, Daniel J.; Harlen, Oliver G.; Harris, Sarah A.

    2013-04-01

    We describe a novel coarse-grained simulation method for modelling the dynamics of globular macromolecules, such as proteins. The macromolecule is treated as a continuum that is subject to thermal fluctuations. The model includes a non-linear treatment of elasticity and viscosity with thermal noise that is solved using finite element analysis. We have validated the method by demonstrating that the model provides average kinetic and potential energies that are in agreement with the classical equipartition theorem and that the nodal velocities have the correct Gaussian distribution. In addition, we have performed Fourier analysis on the simulation trajectories obtained for a series of linear beams to confirm that the correct average energies are present in the first two Fourier bending modes and that the probability distribution of the amplitudes of the first two Fourier modes match the theoretical results. We demonstrate spatial convergence of the model by showing that the anisotropy of the inertia tensor for a cubic mesh converges as a function of the mesh resolution. We have then used the new modelling method to simulate the thermal fluctuations of a representative protein over 500 ns timescales. Using reasonable parameters for the material properties, we have demonstrated that the overall deformation of the biomolecule is consistent with the results obtained for proteins in general from atomistic molecular dynamics simulations.

  11. Proper Motions and Structural Parameters of the Galactic Globular Cluster M71

    Energy Technology Data Exchange (ETDEWEB)

    Cadelano, M.; Dalessandro, E.; Ferraro, F. R.; Miocchi, P.; Lanzoni, B.; Pallanca, C. [Dipartimento di Fisica e Astronomia, Università di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy); Massari, D. [INAF—Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)

    2017-02-20

    By exploiting two ACS/ HST data sets separated by a temporal baseline of ∼7 years, we have determined the relative stellar proper motions (PMs; providing membership) and the absolute PM of the Galactic globular cluster M71. The absolute PM has been used to reconstruct the cluster orbit within a Galactic, three-component, axisymmetric potential. M71 turns out to be in a low-latitude disk-like orbit inside the Galactic disk, further supporting the scenario in which it lost a significant fraction of its initial mass. Since large differential reddening is known to affect this system, we took advantage of near-infrared, ground-based observations to re-determine the cluster center and density profile from direct star counts. The new structural parameters turn out to be significantly different from the ones quoted in the literature. In particular, M71 has a core and a half-mass radii almost 50% larger than previously thought. Finally, we estimate that the initial mass of M71 was likely one order of magnitude larger than its current value, thus helping to solve the discrepancy with the observed number of X-ray sources.

  12. Synthesis of giant globular multivalent glycofullerenes as potent inhibitors in a model of Ebola virus infection

    Science.gov (United States)

    Muñoz, Antonio; Sigwalt, David; Illescas, Beatriz M.; Luczkowiak, Joanna; Rodríguez-Pérez, Laura; Nierengarten, Iwona; Holler, Michel; Remy, Jean-Serge; Buffet, Kevin; Vincent, Stéphane P.; Rojo, Javier; Delgado, Rafael; Nierengarten, Jean-François; Martín, Nazario

    2016-01-01

    The use of multivalent carbohydrate compounds to block cell-surface lectin receptors is a promising strategy to inhibit the entry of pathogens into cells and could lead to the discovery of novel antiviral agents. One of the main problems with this approach, however, is that it is difficult to make compounds of an adequate size and multivalency to mimic natural systems such as viruses. Hexakis adducts of [60]fullerene are useful building blocks in this regard because they maintain a globular shape at the same time as allowing control over the size and multivalency. Here we report water-soluble tridecafullerenes decorated with 120 peripheral carbohydrate subunits, so-called ‘superballs’, that can be synthesized efficiently from hexakis adducts of [60]fullerene in one step by using copper-catalysed azide-alkyne cycloaddition click chemistry. Infection assays show that these superballs are potent inhibitors of cell infection by an artificial Ebola virus with half-maximum inhibitory concentrations in the subnanomolar range.

  13. Interaction of Small Zinc Complexes with Globular Proteins and Free Tryptophan

    Directory of Open Access Journals (Sweden)

    Joann M. Butkus

    2016-01-01

    Full Text Available A series of eight water soluble anionic, cationic, and neutral zinc(II complexes were synthesized and characterized. The interaction of these complexes with bovine serum albumin (BSA, human serum albumin (HSA, lysozyme, and free tryptophan (Trp was investigated using steady-state fluorescence spectroscopy. Static and dynamic fluorescence quenching analysis based on Stern-Volmer kinetics was conducted, and the decrease in fluorescence intensity of the Trp residue(s can be ascribed predominantly to static quenching that occurs when the Zn complex binds to the protein and forms a nonfluorescent complex. The role played by the nature of the ligand, the metal, and complex charge in quenching Trp fluorescence was investigated. The binding association constants (Ka ranged from 104 to 1010 M−1 and indicate that complexes with planar aromatic features have the strongest affinity for globular proteins and free Trp. Complexes with nonaromatic features failed to interact with these proteins at or in the vicinity of the Trp residues. These interactions were studied over a range of temperatures, and binding was found to weaken with the increase in temperature and was exothermic with a negative change in entropy. The thermodynamic parameters suggest that binding of Zn complexes to the proteins is a highly spontaneous and favorable process.

  14. A High-precision Trigonometric Parallax to an Ancient Metal-poor Globular Cluster

    Science.gov (United States)

    Brown, T. M.; Casertano, S.; Strader, J.; Riess, A.; VandenBerg, D. A.; Soderblom, D. R.; Kalirai, J.; Salinas, R.

    2018-03-01

    Using the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST), we have obtained a direct trigonometric parallax for the nearest metal-poor globular cluster, NGC 6397. Although trigonometric parallaxes have been previously measured for many nearby open clusters, this is the first parallax for an ancient metal-poor population—one that is used as a fundamental template in many stellar population studies. This high-precision measurement was enabled by the HST/WFC3 spatial-scanning mode, providing hundreds of astrometric measurements for dozens of stars in the cluster and also for Galactic field stars along the same sightline. We find a parallax of 0.418 ± 0.013 ± 0.018 mas (statistical, systematic), corresponding to a true distance modulus of 11.89 ± 0.07 ± 0.09 mag (2.39 ± 0.07 ± 0.10 kpc). The V luminosity at the stellar main-sequence turnoff implies an absolute cluster age of 13.4 ± 0.7 ± 1.2 Gyr. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO-13817, GO-14336, and GO-14773.

  15. Chemical characterisation of the globular cluster NGC 5634 associated to the Sagittarius dwarf spheroidal galaxy

    Science.gov (United States)

    Carretta, E.; Bragaglia, A.; Lucatello, S.; D'Orazi, V.; Gratton, R. G.; Donati, P.; Sollima, A.; Sneden, C.

    2017-04-01

    As part of our on-going project on the homogeneous chemical characterisation of multiple stellar populations in globular clusters (GCs), we studied NGC 5634, associated to the Sagittarius dwarf spheroidal galaxy, using high-resolution spectroscopy of red giant stars collected with VLT/FLAMES. We present here the radial velocity distribution of the 45 observed stars, 43 of which are cluster members, the detailed chemical abundance of 22 species for the seven stars observed with UVES-FLAMES, and the abundance of six elements for stars observed with GIRAFFE. On our homogeneous UVES metallicity scale, we derived a low-metallicity [Fe/H] =-1.867 ± 0.019 ± 0.065 dex (±statistical ±systematic error) with σ = 0.050 dex (7 stars). We found the normal anticorrelations between light elements (Na and O, Mg and Al), a signature of multiple populations typical of massive and old GCs. We confirm the associations of NGC 5634 to the Sgr dSph, from which the cluster was lost a few Gyr ago, on the basis of its velocity and position, and the abundance ratios of α and neutron capture elements. Based on observations collected at ESO telescopes under programme 093.B-0583.Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/600/A118

  16. Testing lowered isothermal models with direct N-body simulations of globular clusters - II. Multimass models

    Science.gov (United States)

    Peuten, M.; Zocchi, A.; Gieles, M.; Hénault-Brunet, V.

    2017-09-01

    Lowered isothermal models, such as the multimass Michie-King models, have been successful in describing observational data of globular clusters. In this study, we assess whether such models are able to describe the phase space properties of evolutionary N-body models. We compare the multimass models as implemented in limepy (Gieles & Zocchi) to N-body models of star clusters with different retention fractions for the black holes and neutron stars evolving in a tidal field. We find that multimass models successfully reproduce the density and velocity dispersion profiles of the different mass components in all evolutionary phases and for different remnants retention. We further use these results to study the evolution of global model parameters. We find that over the lifetime of clusters, radial anisotropy gradually evolves from the low- to the high-mass components and we identify features in the properties of observable stars that are indicative of the presence of stellar-mass black holes. We find that the model velocity scale depends on mass as m-δ, with δ ≃ 0.5 for almost all models, but the dependence of central velocity dispersion on m can be shallower, depending on the dark remnant content, and agrees well with that of the N-body models. The reported model parameters, and correlations amongst them, can be used as theoretical priors when fitting these types of mass models to observational data.

  17. THE SLUGGS SURVEY: NGC 3115, A CRITICAL TEST CASE FOR METALLICITY BIMODALITY IN GLOBULAR CLUSTER SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Brodie, Jean P.; Conroy, Charlie; Arnold, Jacob A.; Romanowsky, Aaron J. [University of California Observatories and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Usher, Christopher; Forbes, Duncan A. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Strader, Jay, E-mail: brodie@ucolick.org [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

    2012-11-10

    Due to its proximity (9 Mpc) and the strongly bimodal color distribution of its spectroscopically well-sampled globular cluster (GC) system, the early-type galaxy NGC 3115 provides one of the best available tests of whether the color bimodality widely observed in GC systems generally reflects a true metallicity bimodality. Color bimodality has alternatively been attributed to a strongly nonlinear color-metallicity relation reflecting the influence of hot horizontal-branch stars. Here, we couple Subaru Suprime-Cam gi photometry with Keck/DEIMOS spectroscopy to accurately measure GC colors and a CaT index that measures the Ca II triplet. We find the NGC 3115 GC system to be unambiguously bimodal in both color and the CaT index. Using simple stellar population models, we show that the CaT index is essentially unaffected by variations in horizontal-branch morphology over the range of metallicities relevant to GC systems (and is thus a robust indicator of metallicity) and confirm bimodality in the metallicity distribution. We assess the existing evidence for and against multiple metallicity subpopulations in early- and late-type galaxies and conclude that metallicity bi/multimodality is common. We briefly discuss how this fundamental characteristic links directly to the star formation and assembly histories of galaxies.

  18. ULTRA-DEEP GEMINI NEAR-INFRARED OBSERVATIONS OF THE BULGE GLOBULAR CLUSTER NGC 6624

    Energy Technology Data Exchange (ETDEWEB)

    Saracino, S.; Dalessandro, E.; Ferraro, F. R.; Lanzoni, B.; Miocchi, P. [Dipartimento di Fisica e Astronomia, Università di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy); Geisler, D.; Mauro, F.; Cohen, R. E.; Villanova, S. [Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Origlia, L. [INAF—Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Bidin, C. Moni, E-mail: sara.saracino@unibo.it [Instituto de Astronomía, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta (Chile)

    2016-11-20

    We used ultra-deep J and K {sub s} images secured with the near-infrared (NIR) GSAOI camera assisted by the multi-conjugate adaptive optics system GeMS at the GEMINI South Telescope in Chile, to obtain a ( K {sub s} , J - K {sub s} ) color–magnitude diagram (CMD) for the bulge globular cluster NGC 6624. We obtained the deepest and most accurate NIR CMD from the ground for this cluster, by reaching K {sub s} ∼ 21.5, approximately 8 mag below the horizontal branch level. The entire extension of the Main Sequence (MS) is nicely sampled and at K {sub s} ∼ 20 we detected the so-called MS “knee” in a purely NIR CMD. By taking advantage of the exquisite quality of the data, we estimated the absolute age of NGC 6624 ( t {sub age} = 12.0 ± 0.5 Gyr), which turns out to be in good agreement with previous studies in the literature. We also analyzed the luminosity and mass functions of MS stars down to M ∼ 0.45 M{sub ⊙}, finding evidence of a significant increase of low-mass stars at increasing distances from the cluster center. This is a clear signature of mass segregation, confirming that NGC 6624 is in an advanced stage of dynamical evolution.

  19. Eight Hundred New Candidates for Globular Clusters in NGC 5128 (Centaurus A)

    Science.gov (United States)

    Harris, Gretchen L. H.; Gómez, Matías; Harris, William E.; Johnston, Kyle; Kazemzadeh, Farnoud; Kerzendorf, Wolfgang; Geisler, Doug; Woodley, Kristin A.

    2012-04-01

    We have used new wide-field imaging with the Magellan IMACS camera to search for globular cluster (GC) candidates around NGC 5128, the nearest giant E galaxy. The imaging data are in the B and R broadband filters and cover a 1.55 deg2 field centered on the galaxy, corresponding to an area about 90 × 90 kpc2 at the distance of NGC 5128. All the fields were taken under exceptionally high-quality seeing conditions (FWHM = 0farcs4-0farcs5 in R). Using this material we are able, for the first time in the literature, to construct a homogeneous list of GC candidates covering a wide span of the NGC 5128 halo and unusually free of field contaminants (foreground stars and faint background galaxies). Selecting the measured objects by color, magnitude, ellipticity, and profile size gives us a final catalog of 833 new high-quality GC candidates brighter than R = 21 (0.8 mag fainter than the standard GC luminosity function turnover point). The measured positions have better than 0farcs2 precision in both coordinates. This list can be used as the basis for spectroscopic follow-up, leading to a more comprehensive kinematic and dynamic study of the halo. This Paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  20. Identifying the adaptive mechanism in globular proteins: Fluctuations in densely packed regions manipulate flexible parts

    Science.gov (United States)

    Yilmaz, Lutfu Safak; Atilgan, Ali Rana

    2000-09-01

    A low-resolution structural model based on the packing geometry of α-carbons is utilized to establish a connection between the flexible and rigid parts of a folded protein. The former commonly recognizes a complementing molecule for making a complex, while the latter manipulates the necessary conformational change for binding. We attempt analytically to distinguish this control architecture that intrinsically exists in globular proteins. First with two-dimensional simple models, then for a native protein, bovine pancreatic trypsin inhibitor, we explicitly demonstrate that inserting fluctuations in tertiary contacts supported by the stable core, one can regulate the displacement of residues on loop regions. The positional fluctuations of the flexible regions are annihilated by the rest of the protein in conformity with the Le Chatelier-Braun principle. The results indicate that the distortion of the principal nonbonded contacts between highly packed residues is accompanied by that of the slavery fluctuations that are widely distributed over the native structure. These positional arrangements do not appear in a reciprocal relation between a perturbation and the associated response; the effect of a movement of residue i on residue j is not equal to that of the same movement of residue j on residue i.

  1. Constraining the origin of multiple stellar populations in globular clusters with N-body simulations

    Science.gov (United States)

    Mastrobuono-Battisti, A.; Perets, H. B.

    2017-12-01

    Globular Clusters (GCs) are composed by multiple stellar populations whose origin is still unknown. Second population (SP) stars are currently thought to arise from gas ejected by first population (FP) stars, which is then accreted into the primordial GC core. Such gas forms a stellar disk whose long-term evolution and effects on the embedding cluster can be followed by means of N-body simulations. Here, we find that as the SP disk relaxes, the old, first stellar population flattens and develops a significant radial anisotropy, making the GC structure become more elliptical. The second stellar population is characterized by a lower velocity dispersion, and a higher rotational velocity, compared with the primordial population. The strength of these signatures increases with the relaxation time of the cluster and with the mass ratio between the SP and FP mass stars. We conclude that GC ellipticities and rotation constitute fossil records that can be used as observational proxies to unveil the origin of multiple stellar populations.

  2. Galaxy structure from multiple tracers - I. A census of M87's globular cluster populations

    Science.gov (United States)

    Oldham, L. J.; Auger, M. W.

    2016-01-01

    We present a new photometric catalogue of the rich globular cluster (GC) system around M87, the brightest cluster galaxy in Virgo. Using archival Next Generation Virgo Cluster Survey images in the ugriz bands, observed with Canada-France-Hawaii Telescope/MegaPrime, we perform a careful subtraction of the galaxy's halo light in order to detect objects at small galactocentric radii as well as in the wider field, and find 17 620 GC candidates over a radius range from 1.3 to 445 kpc with g < 24 mag. By inferring their colour, radial and magnitude distributions in a Bayesian way, we find that they are well described as a mixture of two GC populations and two distinct contaminant populations, but confirm earlier findings of radius-dependent colour gradients in both GC populations. This is consistent with a picture in which the more enriched GCs reside deeper in the galaxy's potential well, indicating a role for dissipative collapse in the formation of both the red and the blue GCs.

  3. Globular adiponectin activates motility and regenerative traits of muscle satellite cells.

    Directory of Open Access Journals (Sweden)

    Tania Fiaschi

    Full Text Available Regeneration of adult injured skeletal muscle is due to activation of satellite cells, a population of stem cells resident beneath the basal lamina. Thus, information on soluble factors affecting satellite cell activation, as well as migration towards injury and fusion into new myofibers are essential. Here, we show that globular adiponectin (gAd, positively affects several features of muscle satellite cells. gAd activates satellite cells to exit quiescence and increases their recruitment towards myotubes. gAd elicits in satellite cells a specific motility program, involving activation of the small GTPase Rac1, as well as expression of Snail and Twist transcription factors driving a proteolytic motility, useful to reach the site of injury. We show that satellite cells produce autocrine full length adiponectin (fAd, which is converted to gAd by activated macrophages. In turns, gAd concurs to attract to the site of injury both satellite cells and macrophages and induces myogenesis in muscle satellite cells. Thus, these findings add a further role for gAd in skeletal muscle, including the hormone among factors participating in muscle regeneration.

  4. The radius of the quiescent neutron star in the globular cluster M13

    Science.gov (United States)

    Shaw, A. W.; Heinke, C. O.; Steiner, A. W.; Campana, S.; Cohn, H. N.; Ho, W. C. G.; Lugger, P. M.; Servillat, M.

    2018-03-01

    X-ray spectra of quiescent low-mass X-ray binaries containing neutron stars can be fit with atmosphere models to constrain the mass and the radius. Mass-radius constraints can be used to place limits on the equation of state of dense matter. We perform fits to the X-ray spectrum of a quiescent neutron star in the globular cluster M13, utilizing data from ROSAT, Chandra and XMM-Newton, and constrain the mass-radius relation. Assuming an atmosphere composed of hydrogen and a 1.4M⊙ neutron star, we find the radius to be R_NS=12.2^{+1.5}_{-1.1} km, a significant improvement in precision over previous measurements. Incorporating an uncertainty on the distance to M13 relaxes the radius constraints slightly and we find R_NS=12.3^{+1.9}_{-1.7} km (for a 1.4M⊙ neutron star with a hydrogen atmosphere), which is still an improvement in precision over previous measurements, some of which do not consider distance uncertainty. We also discuss how the composition of the atmosphere affects the derived radius, finding that a helium atmosphere implies a significantly larger radius.

  5. Fermi Detection of a Luminous gamma-ray Pulsar in a Globular Cluster

    Science.gov (United States)

    Freire, P. C. C.; Abdo, A. A.; Ajello, M.; Allafort, A.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Blandford, R. D.; hide

    2011-01-01

    We report the Fermi Large Area Telescope detection of gamma -ray (>100 mega-electron volts) pulsations from pulsar J1823--3021A in the globular cluster NGC 6624 with high significance (approx 7 sigma). Its gamma-ray luminosity L (sub 3) = (8:4 +/- 1:6) X 10(exp 34) ergs per second, is the highest observed for any millisecond pulsar (MSP) to date, and it accounts for most of the cluster emission. The non-detection of the cluster in the off-pulse phase implies that its contains < 32 gamma-ray MSPs, not approx 100 as previously estimated. The gamma -ray luminosity indicates that the unusually large rate of change of its period is caused by its intrinsic spin-down. This implies that J1823--3021A has the largest magnetic field and is the youngest MSP ever detected, and that such anomalous objects might be forming at rates comparable to those of the more normal MSPs.

  6. Multi-wavelength modeling of globular clusters–the millisecond pulsar scenario

    Energy Technology Data Exchange (ETDEWEB)

    Kopp, A.; Venter, C.; Büsching, I.; De Jager, O. C. [Centre for Space Research, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520 (South Africa)

    2013-12-20

    The potentially large number of millisecond pulsars (MSPs) in globular cluster (GC) cores makes these parent objects ideal laboratories for studying the collective properties of an ensemble of MSPs. Such a population is expected to radiate several spectral components in the radio through γ-ray waveband. First, pulsed emission is expected via curvature and synchrotron radiation (CR and SR) and possibly even via inverse Compton (IC) scattering inside the pulsar magnetospheres. Second, unpulsed emission should transpire through the continuous injection of relativistic leptons by the MSPs into the ambient region, which in turn produce SR and IC emission when they encounter the cluster magnetic field, as well as several background photon components. In this paper we continue to develop the MSP scenario for explaining the multi-wavelength properties of GCs by considering the entire modeling chain, including the full transport equation, refined emissivities of stellar and Galactic background photons, integration of the flux along the line of sight, and comparison with observations. As an illustration, we apply the model to Terzan 5, where we can reasonably fit both the (line-of-sight-integrated) X-ray surface flux and spectral energy density data, using the first to constrain the leptonic diffusion coefficient within the GC. We lastly discuss possible future extensions to and applications of this maturing model.

  7. The VMC survey. XI. Radial stellar population gradients in the galactic globular cluster 47 Tucanae

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chengyuan; De Grijs, Richard [Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Hai Dian District, Beijing 100871 (China); Deng, Licai [Key Laboratory for Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012 (China); Rubele, Stefano; Girardi, Leo; Gullieuszik, Marco [INAF-Osservatorio Astronomico di Padova, vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Wang, Chuchu [Department of Astronomy, Peking University, Yi He Yuan Lu 5, Hai Dian District, Beijing 100871 (China); Bekki, Kenji; For, Bi-Qing [ICRAR M468, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); Cioni, Maria-Rosa L. [Department of Physics, Astronomy, and Mathematics, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Clementini, Gisella [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Emerson, Jim [Astronomy Unit, School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Groenewegen, Martin A. T. [Royal Observatory of Belgium, Ringlaan 3, 1180 Ukkel (Belgium); Guandalini, Roald [Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D 2401, 3001 Leuven (Belgium); Marconi, Marcella; Ripepi, Vincenzo [INAF-Osservatorio Astronomico di Capodimonte, via Moiariello 16, I-80131 Naples (Italy); Piatti, Andrés E. [Observatorio Astrońomico, Universidad Nacional de Córdoba, Laprida 854, 5000 Córdoba (Argentina); Van Loon, Jacco Th., E-mail: joshuali@pku.edu.cn, E-mail: grijs@pku.edu.cn [Astrophysics Group, Lennard-Jones Laboratories, Keele University, Staffordshire ST5 5BG (United Kingdom)

    2014-07-20

    We present a deep near-infrared color-magnitude diagram of the Galactic globular cluster 47 Tucanae, obtained with the Visible and Infrared Survey Telescope for Astronomy (VISTA) as part of the VISTA near-infrared Y, J, K{sub s} survey of the Magellanic System (VMC). The cluster stars comprising both the subgiant and red giant branches exhibit apparent, continuous variations in color-magnitude space as a function of radius. Subgiant branch stars at larger radii are systematically brighter than their counterparts closer to the cluster core; similarly, red-giant-branch stars in the cluster's periphery are bluer than their more centrally located cousins. The observations can very well be described by adopting an age spread of ∼0.5 Gyr as well as radial gradients in both the cluster's helium abundance (Y) and metallicity (Z), which change gradually from (Y = 0.28, Z = 0.005) in the cluster core to (Y = 0.25, Z = 0.003) in its periphery. We conclude that the cluster's inner regions host a significant fraction of second-generation stars, which decreases with increasing radius; the stellar population in the 47 Tuc periphery is well approximated by a simple stellar population.

  8. Immunization with influenza virus hemagglutinin globular region containing the receptor-binding pocket.

    Science.gov (United States)

    Jeon, Sung Ho; Arnon, Ruth

    2002-01-01

    The globular region of hemagglutinin (residues 91-261) membrane glycoprotein of influenza virus that encompasses the binding zone to the oligosaccharide receptor of target cells has been cloned by reverse transcriptase-polymerase chain reaction (RT-PCR). This protein segment (denoted HA91-261 peptide) induced significant immune response in mice. The serum antibodies and lung homogenates from the immunized mice cross-reacted with native virus particles. The cellular immunity was manifested by proliferative splenocyte responses and cytokine release indicating T helper type 1 activity. The plasmid DNA containing this segment (denoted pHA91-261) provoked, in addition, a significant cytotoxic T lymphocyte (CTL) response, whereas the HA91-261 protein fragment led to no such response. Both the DNA and the protein fragment of HA91-261 induced significant protection against viral challenge, although the immune response they induce might be along different pathways. Interestingly, the combined DNA priming-protein boosting immunization regimen did not induce protection against viral challenges even though it led to significant humoral immune responses similar to that induced by the peptide vaccine.

  9. Spatial structure of the interstellar gas toward the globular cluster M22

    International Nuclear Information System (INIS)

    Bates, B.; Catney, M.G.

    1991-01-01

    High-resolution spectra of Na I interstellar lines are presented for 14 stars in the globular cluster M22. The interstellar gas foreground to the cluster at distance about 2.6 kpc occurs essentially in two velocity ranges. There is a low-velocity component which is quite uniform across the cluster. This gas feature is likely to be a part of the extensive and nearby H I cloud first mapped in the radio region. There is also gas at higher velocities detected between +25 and 60 km/s which is observed with both a single- and a multi-component structure. Significant profile variations for this gas occur on a scale less than 1 arcmin. The location of this gas is not known but it may be associated with the Sagittarius arm. Spectra of the K I interstellar line for a nearby star roughly 1.3 deg from the cluster and for two cluster members provide useful estimates for the column densities of the gas components. 20 refs

  10. The CN–CH Positive Correlation in the Globular Cluster NGC 5286

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Dongwook; Hong, Seungsoo; Lee, Young-Wook, E-mail: dwlim@yonsei.ac.kr, E-mail: ywlee2@yonsei.ac.kr [Center for Galaxy Evolution Research and Department of Astronomy, Yonsei University, Seoul 03722 (Korea, Republic of)

    2017-07-20

    We performed low-resolution spectroscopy of the red giant stars in the Galactic globular cluster (GC) NGC 5286, which is known to show intrinsic heavy element abundance variations. We found that the observed stars in this GC are clearly divided into three subpopulations by CN index (CN-weak, CN-intermediate, and CN-strong). The CN-strong stars are also enhanced in the calcium HK′ (7.4 σ ) and CH (5.1 σ ) indices, while the CN-intermediate stars show no significant difference in the strength of the HK′ index from the CN-weak stars. From the comparison with high-resolution spectroscopic data, we found that the CN- and HK′-strong stars are also enhanced in the abundances of Fe and s -process elements. It appears, therefore, that these stars are later-generation stars affected by some supernova enrichment in addition to the asymptotic giant branch ejecta. In addition, unlike normal GCs, sample stars in NGC 5286 show the CN–CH positive correlation, strengthening our previous suggestion that this positive correlation is only discovered in GCs with heavy element abundance variations, such as M22 and NGC 6273.

  11. Chemical study of the metal-rich globular cluster NGC 5927

    Science.gov (United States)

    Mura-Guzmán, A.; Villanova, S.; Muñoz, C.; Tang, B.

    2018-03-01

    Globular clusters (GCs) are natural laboratories where stellar and chemical evolution can be studied in detail. In addition, their chemical patterns and kinematics can tell us to which Galactic structure (disc, bulge, halo or extragalactic) the cluster belongs to. NGC 5927 is one of most metal-rich GCs in the Galaxy and its kinematics links it to the thick disc. We present abundance analysis based on high-resolution spectra of seven giant stars. The data were obtained using Fibre Large Array Multi Element Spectrograph/Ultraviolet Echelle Spectrograph (UVES) spectrograph mounted on UT2 telescope of the European Southern Observatory. The principal objective of this work is to perform a wide and detailed chemical abundance analysis of the cluster and look for possible Multiple Populations (MPs). We determined stellar parameters and measured 22 elements corresponding to light (Na, Al), alpha (O, Mg, Si, Ca, Ti), iron-peak (Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and heavy elements (Y, Zr, Ba, Ce, Nd, Eu). We found a mean iron content of [Fe/H] = -0.47 ± 0.02 (error on the mean). We confirm the existence of MPs in this GC with an O-Na anti-correlation, and moderate spread in Al abundances. We estimate a mean [α/Fe] = 0.25 ± 0.08. Iron-peak elements show no significant spread. The [Ba/Eu] ratios indicate a predominant contribution from SNeII for the formation of the cluster.

  12. Low-mass X-ray binaries from black-hole retaining globular clusters

    Science.gov (United States)

    Giesler, Matthew; Clausen, Drew; Ott, Christian D.

    2018-03-01

    Recent studies suggest that globular clusters (GCs) may retain a substantial population of stellar-mass black holes (BHs), in contrast to the long-held belief of a few to zero BHs. We model the population of BH low-mass X-ray binaries (BH-LMXBs), an ideal observable proxy for elusive single BHs, produced from a representative group of Milky Way GCs with variable BH populations. We simulate the formation of BH-binaries in GCs through exchange interactions between binary and single stars in the company of tens to hundreds of BHs. Additionally, we consider the impact of the BH population on the rate of compact binaries undergoing gravitational wave driven mergers. The characteristics of the BH-LMXB population and binary properties are sensitive to the GCs structural parameters as well as its unobservable BH population. We find that GCs retaining ˜1000 BHs produce a galactic population of ˜150 ejected BH-LMXBs whereas GCs retaining only ˜20 BHs produce zero ejected BH-LMXBs. Moreover, we explore the possibility that some of the presently known BH-LMXBs might have originated in GCs and identify five candidate systems.

  13. Modelling the observed stellar mass function and its radial variation in galactic globular clusters

    Science.gov (United States)

    Webb, Jeremy J.; Vesperini, Enrico; Dalessandro, Emanuele; Beccari, Giacomo; Ferraro, Francesco R.; Lanzoni, Barbara

    2017-11-01

    We measure how the slope α of the stellar mass function (MF) changes as a function of clustercentric distance r in five Galactic globular clusters and compare α(r) to predictions from direct N-body star cluster simulations. Theoretical studies predict that α(r) (which traces the degree of mass segregation in a cluster) should steepen with time as a cluster undergoes two-body relaxation and that the amount by which the global MF can evolve from its initial state due to stellar escape is directly linked to α(r). We find that the amount of mass segregation in M10, NGC 6218, and NGC 6981 is consistent with their dynamical ages, but only the global MF of M10 is consistent with its degree of mass segregation as well. NGC 5466 and NGC 6101 on the other hand appear to be less segregated than their dynamical ages would indicate. Furthermore, despite the fact that the escape rate of stars in non-segregated clusters is independent of stellar mass, both NGC 5466 and NGC 6101 have near-flat MFs. We discuss various mechanisms which could produce non-segregated clusters with near-flat MFs, including higher mass-loss rates and black hole retention, but argue that for some clusters (NGC 5466 and NGC 6101) explaining the present-day properties might require either a non-universal initial mass function or a much more complex dynamical history.

  14. INFRARED HIGH-RESOLUTION INTEGRATED LIGHT SPECTRAL ANALYSES OF M31 GLOBULAR CLUSTERS FROM APOGEE

    Energy Technology Data Exchange (ETDEWEB)

    Sakari, Charli M. [Department of Astronomy, University of Washington, Seattle WA 98195-1580 (United States); Shetrone, Matthew D. [McDonald Observatory, University of Texas at Austin, HC75 Box 1337-MCD, Fort Davis, TX 79734 (United States); Schiavon, Ricardo P. [Gemini Observatory, 670 N. A’Ohoku Place, Hilo, HI 96720 (United States); Bizyaev, Dmitry; Pan, Kaike [Apache Point Observatory and New Mexico State University, P.O. Box 59, Sunspot, NM, 88349-0059 (United States); Prieto, Carlos Allende; García-Hernández, Domingo Aníbal [Instituto de Astrofísica de Canarias (IAC), Va Lactea s/n, E-38205 La Laguna, Tenerife (Spain); Beers, Timothy C. [Department of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame, Notre Dame, IN 46556 (United States); Caldwell, Nelson [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Lucatello, Sara [INAF Osservatorio Astronomico di Padova, Vicolo dellOsservatorio 5, I-35122 Padova (Italy); Majewski, Steven; O’Connell, Robert W. [Dept. of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States); Strader, Jay, E-mail: sakaricm@u.washington.edu [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

    2016-10-01

    Chemical abundances are presented for 25 M31 globular clusters (GCs), based on moderately high resolution ( R = 22,500) H -band integrated light (IL) spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Infrared (IR) spectra offer lines from new elements, lines of different strengths, and lines at higher excitation potentials compared to the optical. Integrated abundances of C, N, and O are derived from CO, CN, and OH molecular features, while Fe, Na, Mg, Al, Si, K, Ca, and Ti abundances are derived from atomic features. These abundances are compared to previous results from the optical, demonstrating the validity and value of IR IL analyses. The CNO abundances are consistent with typical tip of the red giant branch stellar abundances but are systematically offset from optical Lick index abundances. With a few exceptions, the other abundances agree between the optical and the IR within the 1 σ uncertainties. The first integrated K abundances are also presented and demonstrate that K tracks the α elements. The combination of IR and optical abundances allows better determinations of GC properties and enables probes of the multiple populations in extragalactic GCs. In particular, the integrated effects of the Na/O anticorrelation can be directly examined for the first time.

  15. How round is a protein? Exploring protein structures for globularity using conformal mapping.

    Directory of Open Access Journals (Sweden)

    Joel eHass

    2014-12-01

    Full Text Available We present a new algorithm that automatically computes a measure of the geometric difference between the surface of a protein and a round sphere. The algorithm takes as input two triangulated genus zero surfaces representing the protein and the round sphere, respectively, and constructs a discrete conformal map between these surfaces. The conformal map is chosen to minimize a symmetric elastic energy that measures the distance of the constructed conformal map from an isometry. We illustrate our approach on a set of basic sample problems and then on a dataset of diverse protein structures. We show first that the symmetric elastic energy is able to quantify the roundness of the Platonic solids and that for these surfaces it replicates well traditional measures of roundness such as the sphericity. We then demonstrate that the symmetric elastic energy captures both global and local differences between two surfaces, showing that our method identifies the presence of protruding regions in protein structures and quantifies how these regions make the shape of a protein deviate from globularity. Based on these results, we show that the symmetric elastic energy serves as a probe of the limits of the application of conformal mappings to parametrize protein shapes. We identify limitations of the method and discuss its extension to achieving automatic registration of protein structures based on their surface geometry.

  16. Stellar streams as gravitational experiments. II. Asymmetric tails of globular cluster streams

    Science.gov (United States)

    Thomas, G. F.; Famaey, B.; Ibata, R.; Renaud, F.; Martin, N. F.; Kroupa, P.

    2018-01-01

    Kinematically cold tidal streams of globular clusters (GC) are excellent tracers of the Galactic gravitational potential at moderate Galactocentric distances, and can also be used as probes of the law of gravity on Galactic scales. Here, we compare for the first time the generation of such streams in Newtonian and Milgromian gravity (MOND). We first computed analytical results to investigate the expected shape of the GC gravitational potential in both frameworks, and we then ran N-body simulations with the Phantom of Ramses code. We find that the GCs tend to become lopsided in MOND. This is a consequence of the external field effect which breaks the strong equivalence principle. When the GC is filling its tidal radius the lopsidedness generates a strongly asymmetric tidal stream. In Newtonian dynamics, such markedly asymmetric streams can in general only be the consequence of interactions with dark matter subhalos, giant molecular clouds, or interaction with the Galactic bar. In these Newtonian cases, the asymmetry is the consequence of a very large gap in the stream, whilst in MOND it is a true asymmetry. This should thus allow us in the future to distinguish these different scenarios by making deep observations of the environment of the asymmetric stellar stream of Palomar 5. Moreover, our simulations indicate that the high internal velocity dispersion of Palomar 5 for its small stellar mass would be natural in MOND. The movie is available in electronic form at http://www.aanda.org

  17. JD3 - Neutron Stars: Timing in Extreme Environments

    NARCIS (Netherlands)

    Belloni, Tomaso M.; Méndez, Mariano; Zhang, Chengmin

    2009-01-01

    The space-time around Neutron Stars is indeed an extreme environment. Whether they are in accreting binary systems, isolated or in non-accreting binaries (perhaps with another Neutron Star), Neutron Stars provide a window onto physical processes not accessible by other means. In particular, the

  18. Isolated left carotid artery in CHARGE association: diagnosis and repair.

    Science.gov (United States)

    Ghalili, K; Issenberg, H J; Freeman, N J; Brodman, R F

    1990-07-01

    Isolation of the left carotid artery is extremely rare. We report a case of isolation of the left carotid artery with CHARGE association. Aortic arch abnormalities should be looked for in all children with CHARGE association. The technique of repair involved implantation of the isolated left carotid artery to the ascending aorta.

  19. Overview of extremity arterial trauma in Jordan.

    Science.gov (United States)

    Heis, H A; Bani-Hani, K E; Elheis, M A

    2008-12-01

    The objectives of this study were to review etiologies of trauma, associated injuries, diagnosis, management, and outcomes of patients with vascular injuries in the extremities and relate factors in their treatment to the outcome of the injured extremity. Data were collected retrospectively on 73 patients diagnosed to have upper and lower limbs arterial injuries at King Abdullah University Hospital, Jordan, between 2001 and 2006. Factors evaluated included demographic data, location of vessels injured, mechanism of injury, associated injuries, treatment, and outcome. Patients were predominantly males (54 patients). Isolated vascular trauma was present in 36 patients, while in the remaining 37 patients vascular trauma was aggravated by concomitant injuries. The most common etiology of vascular injuries in the upper and lower extremities was a penetrating injury found in 38 patients (52%). The vessels most commonly involved were the femoral and brachial arteries. Various associated injuries were identified mainly orthopedic in 21 patients (29%) and nerve injuries in 18 patients (25%). Autogenous vein graft interposition was mostly performed in 32 patients (44%). Permanent disability was seen in 8 patients (11%), limb amputation was performed in 5 patients (7%). Five patients died due to associated intraabdominal, thoracic, and head injuries giving a mortality rate of 7%. Delay in surgery, blunt trauma and extensive soft tissue defect in combined orthopedic and vascular injuries were associated with increased risk of amputation, while associated nerve injuries and bone injuries with extensive soft tissue damage are risk factors of poor quality outcome.

  20. Are BALQSOs extreme accretors?

    Science.gov (United States)

    Yuan, M. J.; Wills, B. J.

    2002-12-01

    Broad Absorption Line (BAL) QSOs are QSOs with massive absorbing outflows up to 0.2c. Two hypothesis have been suggested in the past about the nature of BALQSOs: Every QSO might have BAL outflow with some covering factor. BALQSOs are those which happen to have outflow along our line of sight. BALQSOs have intrinsically different physical properties than non-BALQSOs. Based on BALQSO's optical emission properties and a large set of correlations linking many general QSO emission line and continuum properties, it has been suggested that BALQSOs might accrete at near Eddington limit with abundant of fuel supplies. With new BALQSO Hβ region spectroscopic observation conducted at UKIRT and re-analysis of literature data for low and high redshift non-BALQSOs, We confirm that BALQSOs have extreme Fe II and [O III] emission line properties. Using results derived from the latest QSO Hβ region reverberation mapping, we calculated Eddington ratios (˙ {M}/˙ {M}Edd) for our BAL and non-BALQSOs. The Fe II and [O III] strengths are strongly correlated with Eddington ratios. Those correlations link Eddington ratio to a large set of general QSO properties through the Boroson & Green Eigenvector 1. We find that BALQSOs have Eddington ratios close to 1. However, all high redshift, high luminosity QSOs have rather high Eddington ratios. We argue that this is a side effect from selecting the brightest objects. In fact, our high redshift sample might constitute BALQSO's high Eddington ratio orientation parent population.

  1. Likelihood estimators for multivariate extremes

    KAUST Repository

    Huser, Raphaël

    2015-11-17

    The main approach to inference for multivariate extremes consists in approximating the joint upper tail of the observations by a parametric family arising in the limit for extreme events. The latter may be expressed in terms of componentwise maxima, high threshold exceedances or point processes, yielding different but related asymptotic characterizations and estimators. The present paper clarifies the connections between the main likelihood estimators, and assesses their practical performance. We investigate their ability to estimate the extremal dependence structure and to predict future extremes, using exact calculations and simulation, in the case of the logistic model.

  2. Neutron-Capture Nucleosynthesis and the Chemical Evolution of Globular Clusters

    Science.gov (United States)

    Shingles, Luke J.

    2015-09-01

    Elements heavier than iron are almost entirely produced in stars through neutron captures and radioactive decays. Of these heavy elements, roughly half are produced by the slow neutron-capture process (s-process), which takes place under extended exposure to low neutron densities. Most of the s-process production occurs in stars with initial masses between roughly 0.8 and 8 solar masses (Msun), which evolve through the Asymptotic Giant Branch (AGB) phase. This thesis explores several topics related to AGB stars and the s-process, with a focus on comparing theoretical models to observations in the literature on planetary nebulae, post-AGB stars, and globular cluster stars. A recurring theme is the uncertainty of carbon-13-pocket formation, which is crucial for building accurate models of s-process nucleosynthesis. We first investigated whether neutron-capture reactions in AGB stars are the cause of the low sulphur abundances in planetary nebulae and post-AGB stars relative to the interstellar medium. Accounting for uncertainties in the size of the partial mixing zone that forms carbon-13 pockets and the rates of neutron-capture and neutron-producing reactions, our models failed to reproduce the observed levels of sulphur destruction. From this, we concluded that AGB nucleosynthesis is not the cause of the sulphur anomaly. We also discovered a new method to constrain the extent of the partial mixing zone using neon abundances in planetary nebulae. We next aimed to discover the stellar sites of the s-process enrichment in globular clusters that have inter- and intra-cluster variation, with the examples of M4 (relative to M5) and M22, respectively. Using a new chemical evolution code developed by the candidate, we tested models with stellar yields from rotating massive stars and AGB stars. We compared our model predictions for the production of s-process elements with abundances from s-poor and s-rich populations. We found that rotating massive stars alone do not

  3. Strömgren uvby photometry of the peculiar globular cluster NGC 2419

    Science.gov (United States)

    Frank, Matthias J.; Koch, Andreas; Feltzing, Sofia; Kacharov, Nikolay; Wilkinson, Mark I.; Irwin, Mike

    2015-09-01

    NGC 2419 is a peculiar Galactic globular cluster offset from the others in the size-luminosity diagram, and showing several chemical abundance anomalies. Here, we present Strömgren uvby photometry of the cluster. Using the gravity- and metallicity-sensitive c1 and m1 indices, we identify a sample of likely cluster members extending well beyond the formal tidal radius. The estimated contamination by cluster non-members is only one per cent, making our catalogue ideally suited for spectroscopic follow-up. We derive photometric [Fe/H] of red giants, and depending on which metallicity calibration from the literature we use, we find reasonable to excellent agreement with spectroscopic [Fe/H], both for the cluster mean metallicity and for individual stars. We demonstrate explicitly that the photometric uncertainties are not Gaussian and this must be accounted for in any analysis of the metallicity distribution function. Using a realistic, non-Gaussian model for the photometric uncertainties, we find a formal internal [Fe/H] spread of σ=0.11+0.02-0.01 dex. This is an upper limit to the cluster's true [Fe/H] spread and may partially, and possibly entirely, reflect the limited precision of the photometric metallicity estimation and systematic effects. The lack of correlation between spectroscopic and photometric [Fe/H] of individual stars is further evidence against a [Fe/H] spread on the 0.1 dex level. Finally, the CN-sensitive δ4, among other colour indices, anti-correlates strongly with magnesium abundance, indicating that the second-generation stars are nitrogen enriched. The absence of similar correlations in some other CN-sensitive indices supports the second generation being enriched in He, which in these indices approximately compensates the shift due to CN. Compared to a single continuous distribution with finite dispersion, the observed δ4 distribution of red giants is slightly better fit by two distinct populations with no internal spread, with the nitrogen

  4. Habitability in Extreme Conditions

    Science.gov (United States)

    de Lobkowicz, Ysaline; de Crombrugghe, Guerric; Le Maire, Victor; Jago, Alban; Denies, Jonathan; van Vynckt, Delphine; Reydams, Marc; Mertens, Alexandre

    A manned space mission could be perfectly prepared in terms of sciences and technologies, but without a good habitat, a place where the needs of the crew are respected, this isolation and confinement can turn into a nightmare. There is the limitation of engineering: it is more than important to take care about architecture, when human lives are part of the experiment. The goal of the research is the analysis of the hard life of isolation and confinement in Mars' hostile environment and how architecture is a way to improve it. The objective is to place the human in the middle of the analysis. What does a person really need? Therefore Maslow's idea, the pyramid of primary needs, gives us the hierarchy to follow: first survival, food and beverage, then sleep, and only then protection, social activities and work. [1] No more luxury. If all these aspects are respected, a human is able to survive, like it did since so many years. The idea is that each of these main activities has to be related to a different type of space, to provide variability in this close environment. For example, work and relaxing areas have to be separated; a human being needs time for himself, without concentration. A workspace and a relaxing area have a different typology, different colours and lighting, dimensions, furniture. This has also to be respected in a spacecraft. For this research, different sources are used, mainly in the psychological aspect, which is the most important. [2] Therefore questionnaires, interviews, diaries of past expeditions are full of treasures. We do not have to search too far: on earth; polar expeditions, submarines, military camps, etc., give a lot of information. Some very realistic simulations, as on the Mars Desert Research Station (MDRS), will also be used as material: a good analysis of the defaults and well-organized part of the station can conduct to important conclusions. [3] A found analysis and a well-designed habitat are considerable keys for the success

  5. Gravitational Waves and Intermediate-mass Black Hole Retention in Globular Clusters

    Science.gov (United States)

    Fragione, Giacomo; Ginsburg, Idan; Kocsis, Bence

    2018-04-01

    The recent discovery of gravitational waves (GWs) has opened new horizons for physics. Current and upcoming missions, such as LIGO, VIRGO, KAGRA, and LISA, promise to shed light on black holes of every size from stellar mass (SBH) sizes up to supermassive black holes. The intermediate-mass black hole (IMBH) family has not been detected beyond any reasonable doubt. Recent analyses suggest observational evidence for the presence of IMBHs in the centers of two Galactic globular clusters (GCs). In this paper, we investigate the possibility that GCs were born with a central IMBH, which undergoes repeated merger events with SBHs in the cluster core. By means of a semi-analytical method, we follow the evolution of the primordial cluster population in the galactic potential and the mergers of the binary IMBH-SBH systems. Our models predict ≈1000 IMBHs within 1 kpc from the galactic center and show that the IMBH-SBH merger rate density changes from { \\mathcal R }≈ 1000 Gpc‑3 yr‑1 beyond z ≈ 2 to { \\mathcal R }≈ 1{--}10 Gpc‑3 yr‑1 at z ≈ 0. The rates at low redshifts may be significantly higher if young massive star clusters host IMBHs. The merger rates are dominated by IMBHs with masses between 103 and 104 M ⊙. Currently, there are no LIGO/VIRGO upper limits for GW sources in this mass range, but our results show that at design sensitivity, these instruments will detect IMBH-SBH mergers in the coming years. LISA and the Einstein Telescope will be best suited to detect these events. The inspirals of IMBH-SBH systems may also generate an unresolved GW background.

  6. THE ROLE OF THERMOHALINE MIXING IN INTERMEDIATE- AND LOW-METALLICITY GLOBULAR CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Angelou, George C.; Stancliffe, Richard J.; Church, Ross P.; Lattanzio, John C. [Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Melbourne, VIC 3800 (Australia); Smith, Graeme H., E-mail: George.Angelou@monash.edu [Department of Astronomy and Astrophysics, University of California Observatories/Lick Observatory, UC Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2012-04-20

    It is now widely accepted that globular cluster red giant branch (RGB) stars owe their strange abundance patterns to a combination of pollution from progenitor stars and in situ extra mixing. In this hybrid theory a first generation of stars imprints abundance patterns into the gas from which a second generation forms. The hybrid theory suggests that extra mixing is operating in both populations and we use the variation of [C/Fe] with luminosity to examine how efficient this mixing is. We investigate the observed RGBs of M3, M13, M92, M15, and NGC 5466 as a means to test a theory of thermohaline mixing. The second parameter pair M3 and M13 are of intermediate metallicity and our models are able to account for the evolution of carbon along the RGB in both clusters, although in order to fit the most carbon-depleted main-sequence stars in M13 we require a model whose initial [C/Fe] abundance leads to a carbon abundance lower than is observed. Furthermore, our results suggest that stars in M13 formed with some primary nitrogen (higher C+N+O than stars in M3). In the metal-poor regime only NGC 5466 can be tentatively explained by thermohaline mixing operating in multiple populations. We find thermohaline mixing unable to model the depletion of [C/Fe] with magnitude in M92 and M15. It appears as if extra mixing is occurring before the luminosity function bump in these clusters. To reconcile the data with the models would require first dredge-up to be deeper than found in extant models.

  7. Tycho- Gaia Astrometric Solution Parallaxes and Proper Motions for Five Galactic Globular Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Watkins, Laura L.; Van der Marel, Roeland P., E-mail: lwatkins@stsci.edu [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218 (United States)

    2017-04-20

    We present a pilot study of Galactic globular cluster (GC) proper motion (PM) determinations using Gaia data. We search for GC stars in the Tycho- Gaia Astrometric Solution (TGAS) catalog from Gaia Data Release 1 (DR1), and identify five members of NGC 104 (47 Tucanae), one member of NGC 5272 (M3), five members of NGC 6121 (M4), seven members of NGC 6397, and two members of NGC 6656 (M22). By taking a weighted average of member stars, fully accounting for the correlations between parameters, we estimate the parallax (and, hence, distance) and PM of the GCs. This provides a homogeneous PM study of multiple GCs based on an astrometric catalog with small and well-controlled systematic errors and yields random PM errors similar to existing measurements. Detailed comparison to the available Hubble Space Telescope ( HST ) measurements generally shows excellent agreement, validating the astrometric quality of both TGAS and HST . By contrast, comparison to ground-based measurements shows that some of those must have systematic errors exceeding the random errors. Our parallax estimates have uncertainties an order of magnitude larger than previous studies, but nevertheless imply distances consistent with previous estimates. By combining our PM measurements with literature positions, distances, and radial velocities, we measure Galactocentric space motions for the clusters and find that these also agree well with previous analyses. Our analysis provides a framework for determining more accurate distances and PMs of Galactic GCs using future Gaia data releases. This will provide crucial constraints on the near end of the cosmic distance ladder and provide accurate GC orbital histories.

  8. Discovery of a new accreting millisecond X-ray pulsar in the globular cluster NGC 2808

    Science.gov (United States)

    Sanna, A.; Papitto, A.; Burderi, L.; Bozzo, E.; Riggio, A.; Di Salvo, T.; Ferrigno, C.; Rea, N.; Iaria, R.

    2017-02-01

    We report on the discovery of coherent pulsations at a period of 2.9 ms from the X-ray transient MAXI J0911-655 in the globular cluster NGC 2808. We observed X-ray pulsations at a frequency of 339.97 Hz in three different observations of the source performed with XMM-Newton and NuSTAR during the source outburst. This newly discovered accreting millisecond pulsar is part of an ultra-compact binary system characterised by an orbital period of 44.3 min and a projected semi-major axis of 17.6 lt-ms. Based on the mass function, we estimate a minimum companion mass of 0.024 M⊙, which assumes a neutron star mass of 1.4 M⊙ and a maximum inclination angle of 75° (derived from the lack of eclipses and dips in the light-curve of the source). We find that the Roche-lobe of the companion star could either be filled by a hot (5 × 106 K) pure helium white dwarf with a 0.028 M⊙ mass (implying I ≃ 58°) or an old (>5 Gyr) brown dwarf with metallicity abundances between solar/sub-solar and mass ranging in the interval 0.065 to 0.085 (16 < I < 21). During the outburst, the broad-band energy spectra are well described by a superposition of a weak black-body component (kT 0.5 keV) and a hard cut-off power-law with photon index Γ 1.7 and cut-off at a temperature kTe 130 keV. Up until the latest Swift-XRT observation performed on 19th July, 2016, the source had been observed in outburst for almost 150 days, which makes MAXI J0911-655 the second accreting millisecond X-ray pulsar with outburst duration longer than 100 days.

  9. Double blue straggler sequences in globular clusters: The case of NGC 362

    International Nuclear Information System (INIS)

    Dalessandro, E.; Ferraro, F. R.; Massari, D.; Lanzoni, B.; Miocchi, P.; Mucciarelli, A.; Lovisi, L.; Beccari, G.; Bellini, A.; Sills, A.; Sigurdsson, S.

    2013-01-01

    We used high-quality images acquired with the Wide Field Camera 3 on board the Hubble Space Telescope to probe the blue straggler star (BSS) population of the galactic globular cluster NGC 362. We have found two distinct sequences of BSSs: this is the second case, after M30, where such a feature has been observed. Indeed, the BSS location, their extension in magnitude and color, and their radial distribution within the cluster nicely resemble those observed in M30, thus suggesting that the same interpretative scenario can be applied: the red BSS sub-population is generated by mass-transfer binaries, the blue one by collisions. The discovery of four new W UMa stars, three of which lie along the red BSS sequence, further supports this scenario. We also found that the inner portion of the density profile deviates from a King model and is well reproduced by either a mild power law (α ∼ –0.2) or a double King profile. This feature supports the hypothesis that the cluster is currently undergoing the core-collapse phase. Moreover, the BSS radial distribution shows a central peak and monotonically decreases outward without any evidence of an external rising branch. This evidence is a further indication of the advanced dynamical age of NGC 362; in fact, together with M30, NGC 362 belongs to the family of dynamically old clusters (Family III) in the 'dynamical clock' classification proposed by Ferraro et al. The observational evidence presented here strengthens the possible connection between the existence of a double BSS sequence and a quite advanced dynamical status of the parent cluster.

  10. Globular cluster formation with multiple stellar populations: self-enrichment in fractal massive molecular clouds

    Science.gov (United States)

    Bekki, Kenji

    2017-08-01

    Internal chemical abundance spreads are one of fundamental properties of globular clusters (GCs) in the Galaxy. In order to understand the origin of such abundance spreads, we numerically investigate GC formation from massive molecular clouds (MCs) with fractal structures using our new hydrodynamical simulations with star formation and feedback effects of core-collapse supernovae (SNe) and asymptotic giant branch (AGB) stars. We particularly investigate star formation from gas chemically contaminated by SNe and AGB stars ('self-enrichment') in forming GCs within MCs with different initial conditions and environments. The principal results are as follows. GCs with multiple generations of stars can be formed from merging of hierarchical star cluster complexes that are developed from high-density regions of fractal MCs. Feedback effects of SNe and AGB stars can control the formation efficiencies of stars formed from original gas of MCs and from gas ejected from AGB stars. The simulated GCs have strong radial gradients of helium abundances within the central 3 pc. The original MC masses need to be as large as 107 M⊙ for a canonical initial stellar mass function (IMF) so that the final masses of stars formed from AGB ejecta can be ˜105 M⊙. Since star formation from AGB ejecta is rather prolonged (˜108 yr), their formation can be strongly suppressed by SNe of the stars themselves. This result implies that the so-called mass budget problem is much more severe than ever thought in the self-enrichment scenario of GC formation and thus that IMF for the second generation of stars should be 'top-light'.

  11. Therapeutic effects of globular adiponectin in diabetic rats with nonalcoholic fatty liver disease

    Science.gov (United States)

    Ma, Hong; Cui, Fan; Dong, Jing-Jing; You, Guo-Ping; Yang, Xiang-Jiu; Lu, Hua-Dong; Huang, Yan-Ling

    2014-01-01

    AIM: To explore the therapeutic role of globular adiponectin (gAd) in high-fat diet/streptozotocin (STZ)-induced type 2 diabetic rats with nonalcoholic fatty liver disease (NAFLD). METHODS: Seven rats were fed a basic diet (normal control group; NC) during the experiment. Experimental rats (14 rats) were given a high-fat diet for 4 wk and were then injected with STZ to induce type 2 diabetes mellitus (T2DM) and NAFLD. Half of the T2DM/NAFLD rats were randomly injected intraperitoneally with gAd for 7 d (gAd-treated group), while the other 7 rats (T2DM/NAFLD group) received 0.9% saline. Plasma biochemical parameters and insulin concentrations were measured. Liver histopathology was examined by hematoxylin-eosin staining. Insulin receptor expression in the liver was analyzed by immunohistochemical staining, Western blot and quantitative real-time reverse transcription polymerase chain reaction analysis. RESULTS: Compared to the control group, the T2DM/NAFLD group had increased levels of glucolipid and decreased levels of insulin. Plasma glucose and lipid levels were decreased in the gAd-treated group, while serum insulin levels increased. The expression of insulin receptor in the T2DM/NAFLD group increased compared with the NC group, and gAd downregulated insulin receptor expression in the livers of T2DM/NAFLD rats. Steatosis of the liver was alleviated in the gAd-treated group compared to the T2DM/NAFLD group (NAS 1.39 ± 0.51 vs 1.92 ± 0.51, P T2DM rats with NAFLD by promoting insulin secretion, mediating glucolipid metabolism, regulating insulin receptor expression and alleviating hepatic steatosis. PMID:25356056

  12. The Dynamics of the Globular Star Cluster 47 TUC (NGC 104)

    Science.gov (United States)

    Murphy, B. W.; Moore, C. A.; Trotter, T. E.; Cohn, H. N.; Lugger, P. M.

    1998-12-01

    We have fit dynamically evolving Fokker-Planck models to the globular star cluster 47 Tuc (Ngc 104). Using mass-function and star-count data from the Hubble Space Telescope, we have determined the global stellar mass function down to 0.1 Msun. In addition to the mass function and star-count data, the velocity-dispersion profile and millisecond pulsar acceleration are well fit by the model. The best-fitting model is a pre-core-collapse model that mimics the behavior of a cluster with a sizable population of primordial binaries. These Fokker-Planck models are far more successful than are King-Mitchie model for fitting the full set of observational data. The best-fitting model has a mass function with power-law indices of 1.35, -1.0, 0.5, and -1.0 (where 1.35 is the Salpeter index) over the mass intervals of 60 to 1.0 Msun, 1.0 to 0.55 Msun, 0.55 to 0.25 Msun, and 0.35 to 0.1 Msun, respectively. The total mass of the cluster is 1.1x 10(6) Msun, the half-mass radius is 7 parsecs, and the core radius is 0.2 parsecs. The model contains a large number (4.6% of the total cluster mass) in nonluminous objects of 1.4 Msun. If most of these objects are neutron stars, the large inferred number suggest that either the upper main sequence mass function was flatter that the Salpeter mass function or that the progenitor stellar mass range for neutron star formation may extend to lower masses in low-metallicity systems than in high metallicity systems.

  13. Concurrent formation of supermassive stars and globular clusters: implications for early self-enrichment

    Science.gov (United States)

    Gieles, Mark; Charbonnel, Corinne; Krause, Martin G. H.; Hénault-Brunet, Vincent; Agertz, Oscar; Lamers, Henny J. G. L. M.; Bastian, Nathan; Gualandris, Alessia; Zocchi, Alice; Petts, James A.

    2018-04-01

    We present a model for the concurrent formation of globular clusters (GCs) and supermassive stars (SMSs, ≳ 103 M⊙) to address the origin of the HeCNONaMgAl abundance anomalies in GCs. GCs form in converging gas flows and accumulate low-angular momentum gas, which accretes onto protostars. This leads to an adiabatic contraction of the cluster and an increase of the stellar collision rate. A SMS can form via runaway collisions if the cluster reaches sufficiently high density before two-body relaxation halts the contraction. This condition is met if the number of stars ≳ 106 and the gas accretion rate ≳ 105 M⊙/Myr, reminiscent of GC formation in high gas-density environments, such as - but not restricted to - the early Universe. The strong SMS wind mixes with the inflowing pristine gas, such that the protostars accrete diluted hot-hydrogen burning yields of the SMS. Because of continuous rejuvenation, the amount of processed material liberated by the SMS can be an order of magnitude higher than its maximum mass. This `conveyor-belt' production of hot-hydrogen burning products provides a solution to the mass budget problem that plagues other scenarios. Additionally, the liberated material is mildly enriched in helium and relatively rich in other hot-hydrogen burning products, in agreement with abundances of GCs today. Finally, we find a super-linear scaling between the amount of processed material and cluster mass, providing an explanation for the observed increase of the fraction of processed material with GC mass. We discuss open questions of this new GC enrichment scenario and propose observational tests.

  14. Atmospheric Parameters and Metallicities for 2191 Stars in the Globular Cluster M4

    Science.gov (United States)

    Malavolta, Luca; Sneden, Christopher; Piotto, Giampaolo; Milone, Antonino P.; Bedin, Luigi R.; Nascimbeni, Valerio

    2014-02-01

    We report new metallicities for stars of Galactic globular cluster M4 using the largest number of stars ever observed at high spectral resolution in any cluster. We analyzed 7250 spectra for 2771 cluster stars gathered with the Very Large Telescope (VLT) FLAMES+GIRAFFE spectrograph at VLT. These medium-resolution spectra cover a small wavelength range, and often have very low signal-to-noise ratios. We approached this data set by reconsidering the whole method of abundance analysis of large stellar samples from beginning to end. We developed a new algorithm that automatically determines the atmospheric parameters of a star. Nearly all of the data preparation steps for spectroscopic analyses are processed on the syntheses, not the observed spectra. For 322 red giant branch (RGB) stars with V 14.7, we obtain lang[Fe/H]rang = -1.16 (σ = 0.09) after fixing the microturbulent velocity. These values are consistent with previous studies that have performed detailed analyses of brighter RGB stars at higher spectroscopic resolution and wavelength coverage. It is not clear if the small mean metallicity difference between brighter and fainter M4 members is real or is the result of the low signal-to-noise characteristics of the fainter stars. The strength of our approach is shown by recovering a metallicity close to a single value for more than 2000 stars, using a data set that is non-optimal for atmospheric analyses. This technique is particularly suitable for noisy data taken in difficult observing conditions.

  15. Atmospheric parameters and metallicities for 2191 stars in the globular cluster M4

    International Nuclear Information System (INIS)

    Malavolta, Luca; Piotto, Giampaolo; Nascimbeni, Valerio; Sneden, Christopher; Milone, Antonino P.; Bedin, Luigi R.

    2014-01-01

    We report new metallicities for stars of Galactic globular cluster M4 using the largest number of stars ever observed at high spectral resolution in any cluster. We analyzed 7250 spectra for 2771 cluster stars gathered with the Very Large Telescope (VLT) FLAMES+GIRAFFE spectrograph at VLT. These medium-resolution spectra cover a small wavelength range, and often have very low signal-to-noise ratios. We approached this data set by reconsidering the whole method of abundance analysis of large stellar samples from beginning to end. We developed a new algorithm that automatically determines the atmospheric parameters of a star. Nearly all of the data preparation steps for spectroscopic analyses are processed on the syntheses, not the observed spectra. For 322 red giant branch (RGB) stars with V ≤ 14.7, we obtain a nearly constant metallicity, ([Fe/H]) = –1.07 (σ = 0.02). No difference in the metallicity at the level of 0.01 dex is observed between the two RGB sequences identified by Monelli et al. For 1869 subgiant and main-sequence stars with V > 14.7, we obtain ([Fe/H]) = –1.16 (σ = 0.09) after fixing the microturbulent velocity. These values are consistent with previous studies that have performed detailed analyses of brighter RGB stars at higher spectroscopic resolution and wavelength coverage. It is not clear if the small mean metallicity difference between brighter and fainter M4 members is real or is the result of the low signal-to-noise characteristics of the fainter stars. The strength of our approach is shown by recovering a metallicity close to a single value for more than 2000 stars, using a data set that is non-optimal for atmospheric analyses. This technique is particularly suitable for noisy data taken in difficult observing conditions

  16. CHEMICAL ABUNDANCES IN NGC 5024 (M53): A MOSTLY FIRST GENERATION GLOBULAR CLUSTER

    International Nuclear Information System (INIS)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

    2016-01-01

    We present the Fe, Ca, Ti, Ni, Ba, Na, and O abundances for a sample of 53 red giant branch stars in the globular cluster (GC) NGC 5024 (M53). The abundances were measured from high signal-to-noise medium resolution spectra collected with the Hydra multi-object spectrograph on the Wisconsin–Indiana–Yale–NOAO 3.5 m telescope. M53 is of interest because previous studies based on the morphology of the cluster’s horizontal branch suggested that it might be composed primarily of first generation (FG) stars and differ from the majority of other GCs with multiple populations, which have been found to be dominated by the second generation (SG) stars. Our sample has an average [Fe/H] = −2.07 with a standard deviation of 0.07 dex. This value is consistent with previously published results. The alpha-element abundances in our sample are also consistent with the trends seen in Milky Way halo stars at similar metallicities, with enhanced [Ca/Fe] and [Ti/Fe] relative to solar. We find that the Na–O anti-correlation in M53 is not as extended as other GCs with similar masses and metallicities. The ratio of SG to the total number of stars in our sample is approximately 0.27 and the SG generation is more centrally concentrated. These findings further support that M53 might be a mostly FG cluster and could give further insight into how GCs formed the light element abundance patterns we observe in them today.

  17. CHEMICAL ABUNDANCES IN NGC 5053: A VERY METAL-POOR AND DYNAMICALLY COMPLEX GLOBULAR CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico [Astronomy Department, Indiana University, Bloomington, IN 47405 (United States)

    2015-05-10

    NGC 5053 provides a rich environment to test our understanding of the complex evolution of globular clusters (GCs). Recent studies have found that this cluster has interesting morphological features beyond the typical spherical distribution of GCs, suggesting that external tidal effects have played an important role in its evolution and current properties. Additionally, simulations have shown that NGC 5053 could be a likely candidate to belong to the Sagittarius dwarf galaxy (Sgr dSph) stream. Using the Wisconsin–Indiana–Yale–NOAO–Hydra multi-object spectrograph, we have collected high quality (signal-to-noise ratio ∼ 75–90), medium-resolution spectra for red giant branch stars in NGC 5053. Using these spectra we have measured the Fe, Ca, Ti, Ni, Ba, Na, and O abundances in the cluster. We measure an average cluster [Fe/H] abundance of −2.45 with a standard deviation of 0.04 dex, making NGC 5053 one of the most metal-poor GCs in the Milky Way (MW). The [Ca/Fe], [Ti/Fe], and [Ba/Fe] we measure are consistent with the abundances of MW halo stars at a similar metallicity, with alpha-enhanced ratios and slightly depleted [Ba/Fe]. The Na and O abundances show the Na–O anti-correlation found in most GCs. From our abundance analysis it appears that NGC 5053 is at least chemically similar to other GCs found in the MW. This does not, however, rule out NGC 5053 being associated with the Sgr dSph stream.

  18. Chemical Abundances in NGC 5053: A Very Metal-poor and Dynamically Complex Globular Cluster

    Science.gov (United States)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

    2015-05-01

    NGC 5053 provides a rich environment to test our understanding of the complex evolution of globular clusters (GCs). Recent studies have found that this cluster has interesting morphological features beyond the typical spherical distribution of GCs, suggesting that external tidal effects have played an important role in its evolution and current properties. Additionally, simulations have shown that NGC 5053 could be a likely candidate to belong to the Sagittarius dwarf galaxy (Sgr dSph) stream. Using the Wisconsin-Indiana-Yale-NOAO-Hydra multi-object spectrograph, we have collected high quality (signal-to-noise ratio ˜ 75-90), medium-resolution spectra for red giant branch stars in NGC 5053. Using these spectra we have measured the Fe, Ca, Ti, Ni, Ba, Na, and O abundances in the cluster. We measure an average cluster [Fe/H] abundance of -2.45 with a standard deviation of 0.04 dex, making NGC 5053 one of the most metal-poor GCs in the Milky Way (MW). The [Ca/Fe], [Ti/Fe], and [Ba/Fe] we measure are consistent with the abundances of MW halo stars at a similar metallicity, with alpha-enhanced ratios and slightly depleted [Ba/Fe]. The Na and O abundances show the Na-O anti-correlation found in most GCs. From our abundance analysis it appears that NGC 5053 is at least chemically similar to other GCs found in the MW. This does not, however, rule out NGC 5053 being associated with the Sgr dSph stream.

  19. Chemical Abundances in NGC 5024 (M53): A Mostly First Generation Globular Cluster

    Science.gov (United States)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

    2016-06-01

    We present the Fe, Ca, Ti, Ni, Ba, Na, and O abundances for a sample of 53 red giant branch stars in the globular cluster (GC) NGC 5024 (M53). The abundances were measured from high signal-to-noise medium resolution spectra collected with the Hydra multi-object spectrograph on the Wisconsin-Indiana-Yale-NOAO 3.5 m telescope. M53 is of interest because previous studies based on the morphology of the cluster’s horizontal branch suggested that it might be composed primarily of first generation (FG) stars and differ from the majority of other GCs with multiple populations, which have been found to be dominated by the second generation (SG) stars. Our sample has an average [Fe/H] = -2.07 with a standard deviation of 0.07 dex. This value is consistent with previously published results. The alpha-element abundances in our sample are also consistent with the trends seen in Milky Way halo stars at similar metallicities, with enhanced [Ca/Fe] and [Ti/Fe] relative to solar. We find that the Na-O anti-correlation in M53 is not as extended as other GCs with similar masses and metallicities. The ratio of SG to the total number of stars in our sample is approximately 0.27 and the SG generation is more centrally concentrated. These findings further support that M53 might be a mostly FG cluster and could give further insight into how GCs formed the light element abundance patterns we observe in them today.

  20. Galactic Pal-eontology: abundance analysis of the disrupting globular cluster Palomar 5

    Science.gov (United States)

    Koch, Andreas; Côté, Patrick

    2017-05-01

    We present a chemical abundance analysis of the tidally disrupted globular cluster (GC) Palomar 5. By co-adding high-resolution spectra of 15 member stars from the cluster's main body, taken at low signal-to-noise with the Keck/HIRES spectrograph, we were able to measure integrated abundance ratios of 24 species of 20 elements including all major nucleosynthetic channels (namely the light element Na; α-elements Mg, Si, Ca, Ti; Fe-peak and heavy elements Sc, V, Cr, Mn, Co, Ni, Cu, Zn; and the neutron-capture elements Y, Zr, Ba, La, Nd, Sm, Eu). The mean metallicity of -1.56 ± 0.02 ± 0.06 dex (statistical and systematic errors) agrees well with the values from individual, low-resolution measurements of individual stars, but it is lower than previous high-resolution results of a small number of stars in the literature. Comparison with Galactic halo stars and other disrupted and unperturbed GCs renders Pal 5 a typical representative of the Milky Way halo population, as has been noted before, emphasizing that the early chemical evolution of such clusters is decoupled from their later dynamical history. We also performed a test as to the detectability of light element variations in this co-added abundance analysis technique and found that this approach is not sensitive even in the presence of a broad range in sodium of 0.6 dex, a value typically found in the old halo GCs. Thus, while methods of determining the global abundance patterns of such objects are well suited to study their overall enrichment histories, chemical distinctions of their multiple stellar populations is still best obtained from measurements of individual stars. Full Table 3 is is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A41

  1. Atmospheric parameters and metallicities for 2191 stars in the globular cluster M4

    Energy Technology Data Exchange (ETDEWEB)

    Malavolta, Luca; Piotto, Giampaolo; Nascimbeni, Valerio [Dipartimento di Fisica e Astronomia, Vicolo dell' Osservatorio 3, I-35122 Padova (Italy); Sneden, Christopher [Department of Astronomy and McDonald Observatory, The University of Texas, Austin, TX 78712 (United States); Milone, Antonino P. [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT 2611 (Australia); Bedin, Luigi R., E-mail: luca.malavolta@unipd.it, E-mail: giampaolo.piotto@unipd.it, E-mail: valerio.nascimbeni@unipd.it, E-mail: luigi.bedin@oapd.inaf.it, E-mail: chris@verdi.as.utexas.edu, E-mail: milone@mso.anu.edu.au [INAF-Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy)

    2014-02-01

    We report new metallicities for stars of Galactic globular cluster M4 using the largest number of stars ever observed at high spectral resolution in any cluster. We analyzed 7250 spectra for 2771 cluster stars gathered with the Very Large Telescope (VLT) FLAMES+GIRAFFE spectrograph at VLT. These medium-resolution spectra cover a small wavelength range, and often have very low signal-to-noise ratios. We approached this data set by reconsidering the whole method of abundance analysis of large stellar samples from beginning to end. We developed a new algorithm that automatically determines the atmospheric parameters of a star. Nearly all of the data preparation steps for spectroscopic analyses are processed on the syntheses, not the observed spectra. For 322 red giant branch (RGB) stars with V ≤ 14.7, we obtain a nearly constant metallicity, ([Fe/H]) = –1.07 (σ = 0.02). No difference in the metallicity at the level of 0.01 dex is observed between the two RGB sequences identified by Monelli et al. For 1869 subgiant and main-sequence stars with V > 14.7, we obtain ([Fe/H]) = –1.16 (σ = 0.09) after fixing the microturbulent velocity. These values are consistent with previous studies that have performed detailed analyses of brighter RGB stars at higher spectroscopic resolution and wavelength coverage. It is not clear if the small mean metallicity difference between brighter and fainter M4 members is real or is the result of the low signal-to-noise characteristics of the fainter stars. The strength of our approach is shown by recovering a metallicity close to a single value for more than 2000 stars, using a data set that is non-optimal for atmospheric analyses. This technique is particularly suitable for noisy data taken in difficult observing conditions.

  2. CHEMICAL ABUNDANCES IN NGC 5024 (M53): A MOSTLY FIRST GENERATION GLOBULAR CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico [Astronomy Department, Indiana University, Bloomington, IN 47405 (United States)

    2016-06-10

    We present the Fe, Ca, Ti, Ni, Ba, Na, and O abundances for a sample of 53 red giant branch stars in the globular cluster (GC) NGC 5024 (M53). The abundances were measured from high signal-to-noise medium resolution spectra collected with the Hydra multi-object spectrograph on the Wisconsin–Indiana–Yale–NOAO 3.5 m telescope. M53 is of interest because previous studies based on the morphology of the cluster’s horizontal branch suggested that it might be composed primarily of first generation (FG) stars and differ from the majority of other GCs with multiple populations, which have been found to be dominated by the second generation (SG) stars. Our sample has an average [Fe/H] = −2.07 with a standard deviation of 0.07 dex. This value is consistent with previously published results. The alpha-element abundances in our sample are also consistent with the trends seen in Milky Way halo stars at similar metallicities, with enhanced [Ca/Fe] and [Ti/Fe] relative to solar. We find that the Na–O anti-correlation in M53 is not as extended as other GCs with similar masses and metallicities. The ratio of SG to the total number of stars in our sample is approximately 0.27 and the SG generation is more centrally concentrated. These findings further support that M53 might be a mostly FG cluster and could give further insight into how GCs formed the light element abundance patterns we observe in them today.

  3. Tracing the assembly history of NGC 1395 through its Globular Cluster System

    Science.gov (United States)

    Escudero, Carlos G.; Faifer, Favio R.; Smith Castelli, Analía V.; Forte, Juan C.; Sesto, Leandro A.; González, Nélida M.; Scalia, María C.

    2018-03-01

    We used deep Gemini-South/GMOS g΄r΄i΄z΄ images to study the globular cluster (GC) system of the massive elliptical galaxy NGC 1395, located in the Eridanus supergroup. The photometric analysis of the GC candidates reveals a clear colour bimodality distribution, indicating the presence of `blue' and `red' GC subpopulations. While a negative radial colour gradient is detected in the projected spatial distribution of the red GCs, the blue GCs display a shallow colour gradient. The blue GCs also display a remarkable shallow and extended surface density profile, suggesting a significant accretion of low-mass satellites in the outer halo of the galaxy. In addition, the slope of the projected spatial distribution of the blue GCs in the outer regions of the galaxy, is similar to that of the X-ray halo emission. Integrating up to 165 kpc the profile of the projected spatial distribution of the GCs, we estimated a total GC population and specific frequency of 6000 ± 1100 and SN = 7.4 ± 1.4, respectively. Regarding NGC 1395 itself, the analysis of the deep Gemini/GMOS images shows a low surface brightness umbrella-like structure indicating, at least, one recent merger event. Through relations recently published in the literature, we obtained global parameters, such as Mstellar = 9.32 × 1011 M⊙ and Mh = 6.46 × 1013 M⊙. Using public spectroscopic data, we derive stellar population parameters of the central region of the galaxy by the full spectral fitting technique. We have found that this region seems to be dominated for an old stellar population, in contrast to findings of young stellar populations from the literature.

  4. Ultra-deep GEMINI Near-infrared Observations of the Bulge Globular Cluster NGC 6624.

    Science.gov (United States)

    Saracino, S.; Dalessandro, E.; Ferraro, F. R.; Geisler, D.; Mauro, F.; Lanzoni, B.; Origlia, L.; Miocchi, P.; Cohen, R. E.; Villanova, S.; Moni Bidin, C.

    2016-11-01

    We used ultra-deep J and K s images secured with the near-infrared (NIR) GSAOI camera assisted by the multi-conjugate adaptive optics system GeMS at the GEMINI South Telescope in Chile, to obtain a (K s , J - K s ) color-magnitude diagram (CMD) for the bulge globular cluster NGC 6624. We obtained the deepest and most accurate NIR CMD from the ground for this cluster, by reaching K s ˜ 21.5, approximately 8 mag below the horizontal branch level. The entire extension of the Main Sequence (MS) is nicely sampled and at K s ˜ 20 we detected the so-called MS “knee” in a purely NIR CMD. By taking advantage of the exquisite quality of the data, we estimated the absolute age of NGC 6624 (t age = 12.0 ± 0.5 Gyr), which turns out to be in good agreement with previous studies in the literature. We also analyzed the luminosity and mass functions of MS stars down to M ˜ 0.45 M⊙, finding evidence of a significant increase of low-mass stars at increasing distances from the cluster center. This is a clear signature of mass segregation, confirming that NGC 6624 is in an advanced stage of dynamical evolution. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). Based on observations gathered with ESO-VISTA telescope (program ID 179.B-2002).

  5. Five Groups of Red Giants with Distinct Chemical Composition in the Globular Cluster NGC 2808

    Science.gov (United States)

    Carretta, Eugenio

    2015-09-01

    The chemical composition of multiple populations in the massive globular cluster (GC) NGC 2808 is addressed with the homogeneous abundance reanalysis of 140 red giant branch stars. UVES spectra for 31 stars and GIRAFFE spectra for the other giants were analyzed with the same procedures used for about 2500 giants in 23 GCs in our FLAMES survey, deriving abundances of Fe, O, Na, Mg, Si, Ca, Ti, Sc, Cr, Mn, and Ni. Iron, elements from α capture, and those in the Fe group do not show intrinsic scatter. On our UVES scale, the metallicity of NGC 2808 is [Fe/H] =\\-1.129+/- 0.005+/- 0.034 (± statistical ± systematic error) with σ = 0.030 (31 stars). The main features related to proton-capture elements are retrieved, but the improved statistics and the smaller associated internal errors allow us to uncover five distinct groups of stars along the Na-O anticorrelation. We observe large depletions in Mg, anticorrelated with enhancements of Na and also Si, suggestive of unusually high temperatures for proton captures. About 14% of our sample is formed by giants with solar or subsolar [Mg/Fe] ratios. Using the [Na/Mg] ratios, we confirm the presence of five populations with different chemical compositions that we call P1, P2, I1, I2, and E in order of decreasing Mg and increasing Na abundances. Statistical tests show that the mean ratios in any pair of groups cannot be extracted from the same parent distribution. The overlap with the five populations recently detected from UV photometry is good but not perfect, confirming that more distinct components probably exist in this complex GC. Based on data collected at the ESO telescopes under program 072.D-0507 and during the FLAMES Science Verification program.

  6. Evolution of the stellar mass function in multiple-population globular clusters

    Science.gov (United States)

    Vesperini, Enrico; Hong, Jongsuk; Webb, Jeremy J.; D'Antona, Franca; D'Ercole, Annibale

    2018-05-01

    We present the results of a survey of N-body simulations aimed at studying the effects of the long-term dynamical evolution on the stellar mass function (MF) of multiple stellar populations in globular clusters. Our simulations show that if first-(1G) and second-generation (2G) stars have the same initial MF (IMF), the global MFs of the two populations are affected similarly by dynamical evolution and no significant differences between the 1G and 2G MFs arise during the cluster's evolution. If the two populations have different IMFs, dynamical effects do not completely erase memory of the initial differences. Should observations find differences between the global 1G and 2G MFs, these would reveal the fingerprints of differences in their IMFs. Irrespective of whether the 1G and 2G populations have the same global IMF or not, dynamical effects can produce differences between the local (measured at various distances from the cluster centre) 1G and 2G MFs; these differences are a manifestation of the process of mass segregation in populations with different initial structural properties. In dynamically old and spatially mixed clusters, however, differences between the local 1G and 2G MFs can reveal differences between the 1G and 2G global MFs. In general, for clusters with any dynamical age, large differences between the local 1G and 2G MFs are more likely to be associated with differences in the global MF. Our study also reveals a dependence of the spatial mixing rate on the stellar mass, another dynamical consequence of the multiscale nature of multiple-population clusters.

  7. THE GLOBULAR CLUSTER NGC 6402 (M14). I. A NEW BV COLOR-MAGNITUDE DIAGRAM

    Energy Technology Data Exchange (ETDEWEB)

    Contreras Pena, C.; Catelan, M. [Pontificia Universidad Catolica de Chile, Departamento de Astronomia y Astrofisica, Av. Vicuna Mackenna 4860, 782-0436 Macul, Santiago (Chile); Grundahl, F. [Danish AsteroSeismology Centre (DASC), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Stephens, A. W. [Gemini Observatory, 670 North A' ohoku Place, Hilo, HI 96720 (United States); Smith, H. A., E-mail: mcatelan@astro.puc.cl, E-mail: c.contreras@herts.ac.uk [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

    2013-09-15

    We present BV photometry of the Galactic globular cluster NGC 6402 (M14), based on 65 V frames and 67 B frames, reaching two magnitudes below the turnoff level. This represents, to the best of our knowledge, the deepest color-magnitude diagram (CMD) of NGC 6402 available in the literature. Statistical decontamination of field stars as well as differential reddening corrections are performed in order to derive a precise ridgeline and hence physical parameters of the cluster. We discuss previous attempts at deriving a reddening value for the cluster, and argue in favor of a value E(B - V) = 0.57 {+-} 0.02, which is significantly higher than indicated by either the Burstein and Heiles or Schlegel et al. (corrected according to Bonifacio et al.) interstellar dust maps. Differential reddening across the face of the cluster, which we find to be present at the level of {Delta}E(B - V) Almost-Equal-To 0.17 mag, is taken into account in our analysis. We measure several metallicity indicators based on the position of the red giant branch (RGB) in the cluster CMD. These give a metallicity of [Fe/H] = -1.38 {+-} 0.07 on the Zinn and West scale and [Fe/H] = -1.28 {+-} 0.08 on the new Carretta et al. (UVES) scale. We also provide measurements of other important photometric parameters for this cluster, including the position of the RGB luminosity function ''bump'' and the horizontal branch morphology. We compare the NGC 6402 ridgeline with that of NGC 5904 (M5) derived by Sandquist et al., and find evidence that NGC 6402 and M5 have approximately the same age to within the uncertainties, although the possibility that M14 may be slightly older cannot be ruled out.

  8. METALLICITY EFFECT ON LOW-MASS X-RAY BINARY FORMATION IN GLOBULAR CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D.-W.; Fabbiano, G.; Fragos, T. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Ivanova, N.; Sivakoff, G. R. [Department of Physics, University of Alberta, Edmonton, AB (Canada); Jordan, A. [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Santiago (Chile); Voss, R. [Department of Astrophysics/IMAPP, Radboud University, Nijmegen (Netherlands)

    2013-02-10

    We present comprehensive observational results of the metallicity effect on the fraction of globular clusters (GCs) that contain low-mass X-ray binaries (LMXB), by utilizing all available data obtained with Chandra for LMXBs and Hubble Space Telescope Advanced Camera for Surveys (ACS) for GCs. Our primary sample consists of old elliptical galaxies selected from the ACS Virgo and Fornax surveys. To improve statistics at both the lowest and highest X-ray luminosity, we also use previously reported results from other galaxies. It is well known that the fraction of GCs hosting LMXBs is considerably higher in red, metal-rich, GCs than in blue, metal-poor GCs. In this paper, we test whether this metallicity effect is X-ray luminosity-dependent and find that the effect holds uniformly in a wide luminosity range. This result is statistically significant (at {>=}3{sigma}) in LMXBs with luminosities in the range L {sub X} = 2 Multiplication-Sign 10{sup 37} to 5 Multiplication-Sign 10{sup 38} erg s{sup -1}, where the ratio of GC-LMXB fractions in metal-rich to metal-poor GCs is R = 3.4 {+-} 0.5. A similar ratio is also found at lower (down to 10{sup 36} erg s{sup -1}) and higher luminosities (up to the ULX regime), but with less significance ({approx}2{sigma} confidence). Because different types of LMXBs dominate in different luminosities, our finding requires a new explanation for the metallicity effect in dynamically-formed LMXBs. We confirm that the metallicity effect is not affected by other factors such as stellar age, GC mass, stellar encounter rate, and galacto-centric distance.

  9. Modeling the formation of globular cluster systems in the Virgo cluster

    International Nuclear Information System (INIS)

    Li, Hui; Gnedin, Oleg Y.

    2014-01-01

    The mass distribution and chemical composition of globular cluster (GC) systems preserve fossil record of the early stages of galaxy formation. The observed distribution of GC colors within massive early-type galaxies in the ACS Virgo Cluster Survey (ACSVCS) reveals a multi-modal shape, which likely corresponds to a multi-modal metallicity distribution. We present a simple model for the formation and disruption of GCs that aims to match the ACSVCS data. This model tests the hypothesis that GCs are formed during major mergers of gas-rich galaxies and inherit the metallicity of their hosts. To trace merger events, we use halo merger trees extracted from a large cosmological N-body simulation. We select 20 halos in the mass range of 2 × 10 12 to 7 × 10 13 M ☉ and match them to 19 Virgo galaxies with K-band luminosity between 3 × 10 10 and 3 × 10 11 L ☉ . To set the [Fe/H] abundances, we use an empirical galaxy mass-metallicity relation. We find that a minimal merger ratio of 1:3 best matches the observed cluster metallicity distribution. A characteristic bimodal shape appears because metal-rich GCs are produced by late mergers between massive halos, while metal-poor GCs are produced by collective merger activities of less massive hosts at early times. The model outcome is robust to alternative prescriptions for cluster formation rate throughout cosmic time, but a gradual evolution of the mass-metallicity relation with redshift appears to be necessary to match the observed cluster metallicities. We also affirm the age-metallicity relation, predicted by an earlier model, in which metal-rich clusters are systematically several billion younger than their metal-poor counterparts.

  10. WIDE-FIELD PRECISION KINEMATICS OF THE M87 GLOBULAR CLUSTER SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Strader, Jay [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Romanowsky, Aaron J.; Brodie, Jean P.; Beasley, Michael A.; Arnold, Jacob A. [UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States); Spitler, Lee R. [Center for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Tamura, Naoyuki [Subaru Telescope, National Astronomical Observatory of Japan, Hilo, HI 96720 (United States); Sharples, Ray M. [Department of Physics, University of Durham, South Road, Durham (United Kingdom); Arimoto, Nobuo, E-mail: jstrader@cfa.harvard.edu [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)

    2011-12-01

    We present the most extensive combined photometric and spectroscopic study to date of the enormous globular cluster (GC) system around M87, the central giant elliptical galaxy in the nearby Virgo Cluster. Using observations from DEIMOS and the Low Resolution Imaging Spectrometer at Keck, and Hectospec on the Multiple Mirror Telescope, we derive new, precise radial velocities for 451 GCs around M87, with projected radii from {approx}5 to 185 kpc. We combine these measurements with literature data for a total sample of 737 objects, which we use for a re-examination of the kinematics of the GC system of M87. The velocities are analyzed in the context of archival wide-field photometry and a novel Hubble Space Telescope catalog of half-light radii, which includes sizes for 344 spectroscopically confirmed clusters. We use this unique catalog to identify 18 new candidate ultracompact dwarfs and to help clarify the relationship between these objects and true GCs. We find much lower values for the outer velocity dispersion and rotation of the GC system than in earlier papers and also differ from previous work in seeing no evidence for a transition in the inner halo to a potential dominated by the Virgo Cluster, nor for a truncation of the stellar halo. We find little kinematical evidence for an intergalactic GC population. Aided by the precision of the new velocity measurements, we see significant evidence for kinematical substructure over a wide range of radii, indicating that M87 is in active assembly. A simple, scale-free analysis finds less dark matter within {approx}85 kpc than in other recent work, reducing the tension between X-ray and optical results. In general, out to a projected radius of {approx}150 kpc, our data are consistent with the notion that M87 is not dynamically coupled to the Virgo Cluster; the core of Virgo may be in the earliest stages of assembly.

  11. Gemini/GMOS spectra of globular clusters in the Leo group elliptical NGC 3379

    Science.gov (United States)

    Pierce, Michael; Beasley, Michael A.; Forbes, Duncan A.; Bridges, Terry; Gebhardt, Karl; Faifer, Favio Raul; Forte, Juan Carlos; Zepf, Stephen E.; Sharples, Ray; Hanes, David A.; Proctor, Robert

    2006-03-01

    The Leo group elliptical NGC 3379 is one of the few normal elliptical galaxies close enough to make possible observations of resolved stellar populations, deep globular cluster (GC) photometry and high signal-to-noise ratio GC spectra. We have obtained Gemini/GMOS spectra for 22 GCs associated with NGC 3379. We derive ages, metallicities and α-element abundance ratios from simple stellar population models using the recent multi-index χ2 minimization method of Proctor & Sansom. All of these GCs are found to be consistent with old ages, i.e. >~10Gyr, with a wide range of metallicities. This is comparable to the ages and metallicities that Gregg et al. found a couple of years ago for resolved stellar populations in the outer regions of this elliptical. A trend of decreasing α-element abundance ratio with increasing metallicity is indicated. The projected velocity dispersion of the GC system is consistent with being constant with radius. Non-parametric, isotropic models require a significant increase in the mass-to-light ratio at large radii. This result is in contrast to that of Romanowsky et al., who recently found a decrease in the velocity dispersion profile as determined from planetary nebulae (PN). Our constant dispersion requires a normal-sized dark halo, although without anisotropic models we cannot rigorously determine the dark halo mass. A two-sided χ2 test over all radii gives a 2σ difference between the mass profile derived from our GCs compared to the PN-derived mass model of Romanowsky et al. However, if we restrict our analysis to radii beyond one effective radius and test if the GC velocity dispersion is consistently higher, we determine a > 3σ difference between the mass models, and hence we favour the conclusion that NGC 3379 does indeed have dark matter at large radii in its halo.

  12. Three ancient halo subgiants: precise parallaxes, compositions, ages, and implications for globular clusters , ,

    Energy Technology Data Exchange (ETDEWEB)

    VandenBerg, Don A. [Department of Physics and Astronomy, University of Victoria, P.O. Box 1700 STN CSC, Victoria, B.C., V8W 2Y2 (Canada); Bond, Howard E. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Nelan, Edmund P. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Nissen, P. E. [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Schaefer, Gail H. [The CHARA Array of Georgia State University, Mount Wilson Observatory, Mount Wilson, CA 91023 (United States); Harmer, Dianne, E-mail: vandenbe@uvic.ca, E-mail: heb11@psu.edu, E-mail: nelan@stsci.edu, E-mail: pen@phys.au.dk, E-mail: schaefer@chara-array.org, E-mail: diharmer@noao.edu [National Optical Astronomy Observatories, 950 North Cherry Avenue, Tucson, AZ 85726 (United States)

    2014-09-10

    The most accurate ages for the oldest stars are those obtained for nearby halo subgiants because they depend almost entirely on just the measured parallaxes and absolute oxygen abundances. In this study, we have used the Fine Guidance Sensors on the Hubble Space Telescope to determine trigonometric parallaxes, with precisions of 2.1% or better, for the Population II subgiants HD 84937, HD 132475, and HD 140283. High quality spectra have been used to derive their surface abundances of O, Fe, Mg, Si, and Ca, which are assumed to be 0.1-0.15 dex less than their initial abundances due to the effects of diffusion. Comparisons of isochrones with the three subgiants on the (log T {sub eff}, M{sub V} ) diagram yielded ages of 12.08 ± 0.14, 12.56 ± 0.46, and 14.27 ± 0.38 Gyr for HD 84937, HD 132475, and HD 140283, in turn, where each error bar includes only the parallax uncertainty. The total uncertainty is estimated to be ∼ ± 0.8 Gyr (larger in the case of the near-turnoff star HD 84937). Although the age of HD 140283 is greater than the age of the universe as inferred from the cosmic microwave background by ∼0.4-0.5 Gyr, this discrepancy is at a level of <1σ. Nevertheless, the first Population II stars apparently formed very soon after the Big Bang. (Stellar models that neglect diffusive processes seem to be ruled out as they would predict that HD 140283 is ∼1.5 Gyr older than the universe.) The field halo subgiants appear to be older than globular clusters of similar metallicities: if distances close to those implied by the RR Lyrae standard candle are assumed, M 92 and M 5 are younger than HD 140283 and HD 132475 by ∼1.5 and ∼1.0 Gyr, respectively.

  13. Gemini/GMOS imaging of globular clusters in the Virgo galaxy NGC 4649 (M60)

    Science.gov (United States)

    Forbes, Duncan A.; Faifer, Favio Raúl; Forte, Juan Carlos; Bridges, Terry; Beasley, Michael A.; Gebhardt, Karl; Hanes, David A.; Sharples, Ray; Zepf, Stephen E.

    2004-12-01

    We present Sloan g and i imaging from the Gemini Multi-object Spectrograph (GMOS) instrument on the Gemini North telescope for the globular cluster (GC) system around the Virgo galaxy NGC 4649 (M60). Our three pointings, taken in good seeing conditions, cover an area of about 90 square arcmin. We detect 2151 unresolved sources. Applying colour and magnitude selection criteria to this source list gives 995 candidate GCs. Our source list is greater than 90 per cent complete to a magnitude of i= 23.6, and has little contamination from background galaxies. We find fewer than half a dozen potential ultracompact dwarf galaxies around NGC 4649. Foreground extinction from the nearby spiral NGC 4647 is limited to be AV < 0.1. We confirm the bimodality in the GC colour distribution found by earlier work using Hubble Space Telescope/WFPC2 imaging. As is commonly seen in other galaxies, the red GCs are concentrated towards the centre of the galaxy, having a steeper number density profile than the blue GC subpopulation. The varying ratio of red-to-blue GCs with radius can largely explain the overall GC system colour gradient. The underlying galaxy starlight has a similar density profile slope and colour to the red GCs. This suggests a direct connection between the galaxy field stars and the red GC subpopulation. We estimate a total GC population of 3700 +/- 900, with the uncertainty dominated by the extrapolation to larger radii than observed. This total number corresponds to a specific frequency SN= 4.1 +/- 1.0. Future work will present properties derived from GMOS spectra of the NGC 4649 GCs.

  14. NEW CONSTRAINTS ON A COMPLEX RELATION BETWEEN GLOBULAR CLUSTER COLORS AND ENVIRONMENT

    International Nuclear Information System (INIS)

    Powalka, Mathieu; Lançon, Ariane; Puzia, Thomas H.; Alamo-Martínez, Karla; Ángel, Simón; Peng, Eric W.; Lim, Sungsoon; Schönebeck, Frederik; Grebel, Eva K.; Blakeslee, John P.; Côté, Patrick; Ferrarese, Laura; Gwyn, S. D. J.; Cuillandre, Jean-Charles; Duc, Pierre-Alain; Durrell, Patrick; Guhathakurta, Puragra; Kuntschner, Harald

    2016-01-01

    We present an analysis of high-quality photometry for globular clusters (GCs) in the Virgo cluster core region, based on data from the Next Generation Virgo Cluster Survey (NGVS) pilot field, and in the Milky Way (MW), based on Very Large Telescope/X-Shooter spectrophotometry. We find significant discrepancies in color–color diagrams between sub-samples from different environments, confirming that the environment has a strong influence on the integrated colors of GCs. GC color distributions along a single color are not sufficient to capture the differences we observe in color–color space. While the average photometric colors become bluer with increasing radial distance to the cD galaxy M87, we also find a relation between the environment and the slope and intercept of the color–color relations. A denser environment seems to produce a larger dynamic range in certain color indices. We argue that these results are not due solely to differential extinction, Initial Mass Function variations, calibration uncertainties, or overall age/metallicity variations. We therefore suggest that the relation between the environment and GC colors is, at least in part, due to chemical abundance variations, which affect stellar spectra and stellar evolution tracks. Our results demonstrate that stellar population diagnostics derived from model predictions which are calibrated on one particular sample of GCs may not be appropriate for all extragalactic GCs. These results advocate a more complex model of the assembly history of GC systems in massive galaxies that goes beyond the simple bimodality found in previous decades.

  15. Global and nonglobal parameters of horizontal-branch morphology of globular clusters

    International Nuclear Information System (INIS)

    Milone, A. P.; Marino, A. F.; Dotter, A.; Norris, J. E.; Jerjen, H.; Asplund, M.

    2014-01-01

    The horizontal-branch (HB) morphology of globular clusters (GCs) is mainly determined by metallicity. However, the fact that GCs with almost the same metallicity exhibit different HB morphologies demonstrates that at least one more parameter is needed to explain the HB morphology. It has been suggested that one of these should be a global parameter that varies from GC to GC and the other a nonglobal parameter that varies within the GC. In this study we provide empirical evidence corroborating this idea. We used the photometric catalogs obtained with the Advanced Camera for Surveys of the Hubble Space Telescope and analyze the color-magnitude diagrams of 74 GCs. The HB morphology of our sample of GCs has been investigated on the basis of the two new parameters L1 and L2 that measure the distance between the red giant branch and the coolest part of the HB and the color extension of the HB, respectively. We find that L1 correlates with both metallicity and age, whereas L2 most strongly correlates with the mass of the hosting GC. The range of helium abundance among the stars in a GC, characterized by ΔY and associated with the presence of multiple stellar populations, has been estimated in a few GCs to date. In these GCs we find a close relationship among ΔY, GC mass, and L2. We conclude that age and metallicity are the main global parameters, while the range of helium abundance within a GC is the main nonglobal parameter defining the HB morphology of Galactic GCs.

  16. NEW CONSTRAINTS ON A COMPLEX RELATION BETWEEN GLOBULAR CLUSTER COLORS AND ENVIRONMENT

    Energy Technology Data Exchange (ETDEWEB)

    Powalka, Mathieu; Lançon, Ariane [Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l’Université, F-67000 Strasbourg (France); Puzia, Thomas H.; Alamo-Martínez, Karla; Ángel, Simón [Institute of Astrophysics, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago (Chile); Peng, Eric W.; Lim, Sungsoon [Department of Astronomy, Peking University, Beijing 100871 (China); Schönebeck, Frederik; Grebel, Eva K. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg (Germany); Blakeslee, John P.; Côté, Patrick; Ferrarese, Laura; Gwyn, S. D. J. [Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, BC V9E 2E7 (Canada); Cuillandre, Jean-Charles; Duc, Pierre-Alain [AIM Paris Saclay, CNRS/INSU, CEA/Irfu, Université Paris Diderot, Orme des Merisiers, F-91191 Gif-sur-Yvette Cedex (France); Durrell, Patrick [Department of Physics and Astronomy, Youngstown State University, One University Plaza, Youngstown, OH 44555 (United States); Guhathakurta, Puragra [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Kuntschner, Harald, E-mail: mathieu.powalka@astro.unistra.fr [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching (Germany); and others

    2016-09-20

    We present an analysis of high-quality photometry for globular clusters (GCs) in the Virgo cluster core region, based on data from the Next Generation Virgo Cluster Survey (NGVS) pilot field, and in the Milky Way (MW), based on Very Large Telescope/X-Shooter spectrophotometry. We find significant discrepancies in color–color diagrams between sub-samples from different environments, confirming that the environment has a strong influence on the integrated colors of GCs. GC color distributions along a single color are not sufficient to capture the differences we observe in color–color space. While the average photometric colors become bluer with increasing radial distance to the cD galaxy M87, we also find a relation between the environment and the slope and intercept of the color–color relations. A denser environment seems to produce a larger dynamic range in certain color indices. We argue that these results are not due solely to differential extinction, Initial Mass Function variations, calibration uncertainties, or overall age/metallicity variations. We therefore suggest that the relation between the environment and GC colors is, at least in part, due to chemical abundance variations, which affect stellar spectra and stellar evolution tracks. Our results demonstrate that stellar population diagnostics derived from model predictions which are calibrated on one particular sample of GCs may not be appropriate for all extragalactic GCs. These results advocate a more complex model of the assembly history of GC systems in massive galaxies that goes beyond the simple bimodality found in previous decades.

  17. The outer envelopes of globular clusters. II. NGC 1851, NGC 5824 and NGC 1261*

    Science.gov (United States)

    Kuzma, P. B.; Da Costa, G. S.; Mackey, A. D.

    2018-01-01

    We present a second set of results from a wide-field photometric survey of the environs of Milky Way globular clusters. The clusters studied are NGC 1261, NGC 1851 and NGC 5824: all have data from the Dark Energy Camera on the Blanco 4 m telescope. NGC 5824 also has data from the Magellan Clay telescope with MegaCam. We confirm the existence of a large diffuse stellar envelope surrounding NGC 1851 of size at least 240 pc in radius. The radial density profile of the envelope follows a power-law decline with index γ = -1.5 ± 0.2 and the projected shape is slightly elliptical. For NGC 5824, there is no strong detection of a diffuse stellar envelope, but we find the cluster is remarkably extended and is similar in size (at least 230 pc in radius) to the envelope of NGC 1851. A stellar envelope is also revealed around NGC 1261. However, it is notably smaller in size with radius ∼105 pc. The radial density profile of the envelope is also much steeper with γ = -3.8 ± 0.2. We discuss the possible nature of the diffuse stellar envelopes, but are unable to draw definitive conclusions based on the current data. NGC 1851, and potentially NGC 5824, could be stripped dwarf galaxy nuclei, akin to the cases of ω Cen, M54 and M2. On the other hand, the different characteristics of the NGC 1261 envelope suggest that it may be the product of dynamical evolution of the cluster.

  18. Intraperitoneal administration of the globular adiponectin gene ameliorates diabetic nephropathy in Wistar rats.

    Science.gov (United States)

    Yuan, Fang; Liu, Ying-Hong; Liu, Fu-You; Peng, You-Ming; Tian, Jun-Wei

    2014-06-01

    The present study investigated the potential effects of the long-term expression of exogenous adiponectin (ADPN) on normal and diabetic kidneys. Type 2 diabetes mellitus models were induced by high-lipid and high-sucrose feeding plus intraperitoneal injection of streptozotocin. The recombinant plasmid pIRES2-EGFP-gAd, which is able to co-express globular ADPN (gAd) and enhanced green fluorescent protein (EGFP), was intraperitoneally injected into rat models mediated by Lipofectamine. In total, 32 Wistar rats were randomly assigned into four groups: the normal control group, the diabetes group, the diabetes group treated with pIRES2-EGFP-gAd and the diabetes group treated with pIRES2-EGFP. After 12 weeks, serum biochemistry and urine albumin levels were measured. The kidneys were collected to assess the generation of reactive oxygen species (ROS) and the renal pathological changes were observed by light microcopy. The protein expression of endothelial nitric oxide synthase (eNOS), transforming growth factor-β1 (TGF-β1) and phosphorylated adenosine monophosphate-activated protein kinase (p-AMPK) were determined by an immunohistochemical staining method and western blot analysis. Intraperitoneal injection of the human gAd gene via Lipofectamine resulted in abundant ADPN protein in the kidney. In the diabetic rats, the delivery of the exogenous gAd gene ameliorated the progression of diabetic nephropathy (DN). ADPN attenuated urine albumin excretion in the diabetic rats. ADPN also mitigated glomerular mesangial expansion, reduced the generation of ROS and prevented interstitial fibrosis. In addition, the expression of gAd inhibited the renal expression of TGF-β1, promoted the protein expression of eNOS and activated the opening of the AMPK signaling pathway in the renal tissues of the diabetic rats. Despite the effects of ADPN on DN being controversial, these observations indicate that the supplementation of ADPN is beneficial in ameliorating DN in rats.

  19. A Chemical Composition Survey of the Iron-complex Globular Cluster NGC 6273 (M19)

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Christian I.; Caldwell, Nelson [Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, MS-15, Cambridge, MA 02138 (United States); Rich, R. Michael [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States); Mateo, Mario [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Bailey, John I. III [Leiden Observatory, Leiden University, P.O. Box 9513, 2300RA Leiden (Netherlands); Clarkson, William I. [Department of Natural Sciences, University of Michigan–Dearborn, 4901 Evergreen Road, Dearborn, MI 48128 (United States); Olszewski, Edward W. [Steward Observatory, The University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Walker, Matthew G., E-mail: cjohnson@cfa.harvard.edu, E-mail: ncaldwell@cfa.harvard.edu, E-mail: rmr@astro.ucla.edu, E-mail: mmateo@umich.edu, E-mail: baileyji@strw.leidenuniv.nl, E-mail: wiclarks@umich.edu, E-mail: eolszewski@as.arizona.edu, E-mail: mgwalker@andrew.cmu.edu [McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States)

    2017-02-20

    Recent observations have shown that a growing number of the most massive Galactic globular clusters contain multiple populations of stars with different [Fe/H] and neutron-capture element abundances. NGC 6273 has only recently been recognized as a member of this “iron-complex” cluster class, and we provide here a chemical and kinematic analysis of >300 red giant branch and asymptotic giant branch member stars using high-resolution spectra obtained with the Magellan –M2FS and VLT–FLAMES instruments. Multiple lines of evidence indicate that NGC 6273 possesses an intrinsic metallicity spread that ranges from about [Fe/H] = −2 to −1 dex, and may include at least three populations with different [Fe/H] values. The three populations identified here contain separate first (Na/Al-poor) and second (Na/Al-rich) generation stars, but a Mg–Al anti-correlation may only be present in stars with [Fe/H] ≳ −1.65. The strong correlation between [La/Eu] and [Fe/H] suggests that the s-process must have dominated the heavy element enrichment at higher metallicities. A small group of stars with low [ α /Fe] is identified and may have been accreted from a former surrounding field star population. The cluster’s large abundance variations are coupled with a complex, extended, and multimodal blue horizontal branch (HB). The HB morphology and chemical abundances suggest that NGC 6273 may have an origin that is similar to ω Cen and M54.

  20. Little Blue Dots in the Hubble Space Telescope Frontier Fields: Precursors to Globular Clusters?

    Science.gov (United States)

    Elmegreen, Debra Meloy; Elmegreen, Bruce G.

    2017-12-01

    Galaxies with stellar masses {10}-7.4 yr‑1 were examined on images of the Hubble Space Telescope Frontier Field Parallels for Abell 2744 and MACS J0416.1-02403. They appear as unresolved “Little Blue Dots” (LBDs). They are less massive and have higher specific star formation rates (sSFRs) than “blueberries” studied by Yang et al. and higher sSFRs than “Blue Nuggets” studied by Tacchella et al. We divided the LBDs into three redshift bins and, for each, stacked the B435, V606, and I814 images convolved to the same stellar point-spread function (PSF). Their radii were determined from PSF deconvolution to be ∼80 to ∼180 pc. The high sSFRs suggest that their entire stellar mass has formed in only 1% of the local age of the universe. The sSFRs at similar epochs in local dwarf galaxies are lower by a factor of ∼100. Assuming that the star formation rate is {ε }{ff}{M}{gas}/{t}{ff} for efficiency {ε }{ff}, gas mass M gas, and free-fall time, t ff, the gas mass and gas-to-star mass ratio are determined. This ratio exceeds 1 for reasonable efficiencies, and is likely to be ∼5 even with a high {ε }{ff} of 0.1. We consider whether these regions are forming today’s globular clusters. With their observed stellar masses, the maximum likely cluster mass is ∼ {10}5 {M}ȯ , but if star formation continues at the current rate for ∼ 10{t}{ff}∼ 50 {Myr} before feedback and gas exhaustion stop it, then the maximum cluster mass could become ∼ {10}6 {M}ȯ .