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Sample records for largest relaxed galaxy

  1. New Constraints on Dark Energy from Chandra X-rayObservations of the Largest Relaxed Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Allen, S.W.; Rapetti, D.A.; /KIPAC, Menlo Park; Schmidt, R.W.; /Heidelberg, Astron. Rechen Inst.; Ebeling, H.; /Inst. Astron., Honolulu; Morris, G.; /KIPAC, Menlo Park; Fabian, A.C.; /Cambridge U., Inst. of Astron.

    2007-06-06

    We present constraints on the mean matter density, {Omega}{sub m}, dark energy density, {Omega}{sub DE}, and the dark energy equation of state parameter, w, using Chandra measurements of the X-ray gas mass fraction (fgas) in 42 hot (kT > 5keV), X-ray luminous, dynamically relaxed galaxy clusters spanning the redshift range 0.05 < z < 1.1. Using only the fgas data for the 6 lowest redshift clusters at z < 0.15, for which dark energy has a negligible effect on the measurements, we measure {Omega}{sub m}=0.28{+-}0.06 (68% confidence, using standard priors on the Hubble Constant, H{sub 0}, and mean baryon density, {Omega}{sub b}h{sup 2}). Analyzing the data for all 42 clusters, employing only weak priors on H{sub 0} and {Omega}{sub b}h{sup 2}, we obtain a similar result on {Omega}{sub m} and detect the effects of dark energy on the distances to the clusters at {approx}99.99% confidence, with {Omega}{sub DE}=0.86{+-}0.21 for a non-flat LCDM model. The detection of dark energy is comparable in significance to recent SNIa studies and represents strong, independent evidence for cosmic acceleration. Systematic scatter remains undetected in the f{sub gas} data, despite a weighted mean statistical scatter in the distance measurements of only {approx}5%. For a flat cosmology with constant w, we measure {Omega}{sub m}=0.28{+-}0.06 and w=-1.14{+-}0.31. Combining the fgas data with independent constraints from CMB and SNIa studies removes the need for priors on {Omega}{sub b}h{sup 2} and H{sub 0} and leads to tighter constraints: {Omega}{sub m}=0.253{+-}0.021 and w=-0.98{+-}0.07 for the same constant-w model. More general analyses in which we relax the assumption of flatness and/or allow evolution in w remain consistent with the cosmological constant paradigm. Our analysis includes conservative allowances for systematic uncertainties. The small systematic scatter and tight constraints bode well for future dark energy studies using the f{sub gas} method.

  2. STAR FORMATION AND RELAXATION IN 379 NEARBY GALAXY CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, Seth A.; Hickox, Ryan C.; Wegner, Gary A. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States)

    2015-06-10

    We investigate the relationship between star formation (SF) and level of relaxation in a sample of 379 galaxy clusters at z < 0.2. We use data from the Sloan Digital Sky Survey to measure cluster membership and level of relaxation, and to select star-forming galaxies based on mid-infrared emission detected with the Wide-Field Infrared Survey Explorer. For galaxies with absolute magnitudes M{sub r} < −19.5, we find an inverse correlation between SF fraction and cluster relaxation: as a cluster becomes less relaxed, its SF fraction increases. Furthermore, in general, the subtracted SF fraction in all unrelaxed clusters (0.117 ± 0.003) is higher than that in all relaxed clusters (0.097 ± 0.005). We verify the validity of our SF calculation methods and membership criteria through analysis of previous work. Our results agree with previous findings that a weak correlation exists between cluster SF and dynamical state, possibly because unrelaxed clusters are less evolved relative to relaxed clusters.

  3. Galaxy Transformation Under Extreme Conditions: The Evolution of Galaxies in the Largest Structures in the High Redshift Universe

    Science.gov (United States)

    Lemaux, Brian Clark

    a process in the early universe known as reionization, which is the subject of much debate amongst astronomers. The second and third of these studies are investigations using near-infrared spectroscopy of X-ray bright and red galaxies that exhibit optical spectra with prominent emission features. These studies are the first systematic investigations of both galaxy populations in the middle-aged universe using near-infrared spectroscopy. In both studies I conclude the dominant mechanism giving rise to optical emission line features are processes associated with the presence of an Active Galactic Nuclei (AGN) rather than normal star formation. This result has important consequences for galaxy evolutionary scenarios, as the two processes are typically difficult to separate observationally and are thought to be related. The final study in this presentation is a full investigation of the processes driving galaxy evolution in one of the ORELSE fields, the Cl1604 supercluster. In this study I present the wealth of astronomical observations available to the ORELSE survey on the member galaxies of this supercluster. Several transitional populations of galaxies are detected in the supercluster environment, and their properties are analyzed in the context of galaxy evolution. Processing of the galaxy population is found to be significant in both the densest environments in the supercluster and the lower-density regions. One of the major conclusions of this work relates to the efficiency of these transformative processes and the global environment in which a galaxy resides. I present evidence for a process termed "dynamical downsizing", in which efficient transforming of galaxies occurs earliest in structures of galaxies that are observed to be relaxed (i.e., virialized) in their dynamics.

  4. Cosmology and Astrophysics from Relaxed Galaxy Clusters I: Sample Selection

    CERN Document Server

    Mantz, Adam B; Morris, R Glenn; Schmidt, Robert W; von der Linden, Anja; Urban, Ondrej

    2015-01-01

    This is the first in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Here we present a new, automated method for identifying relaxed clusters based on their morphologies in X-ray imaging data. While broadly similar to others in the literature, the morphological quantities that we measure are specifically designed to provide a fair basis for comparison across a range of data quality and cluster redshifts, to be robust against missing data due to point-source masks and gaps between detectors, and to avoid strong assumptions about the cosmological background and cluster masses. Based on three morphological indicators - Symmetry, Peakiness and Alignment - we develop the SPA criterion for relaxation. This analysis was applied to a large sample of cluster observations from the Chandra and ROSAT archives. Of the 361 clusters which received the SPA treatment, 57 (16 per cent) were subsequently found to be relaxed according to our criterion. We compare our me...

  5. Unveiling the formation route of the largest galaxies in the Universe

    Science.gov (United States)

    Perea, Jaime D.; Solanes, José M.

    2016-09-01

    Observational evidence indicates that the role of gas is secondary to that of gravity in the formation of the most luminous spheroids inhabiting the centres of galaxy associations, as originally conjectured in the late 80s/early 90s. However, attempts to explain the origin of the Fundamental Plane (FP) of massive early-type galaxies (ETGs) - a tilted version of the scaling relation connecting the size, velocity dispersion and mass of virialized homologous systems - based on sequences of pairwise mergers, have systematically concluded that dissipation cannot be ignored. We use controlled simulations of the pre-virialization stage of galaxy groups to show that multiple collisionless merging is capable of creating realistic first-ranked galaxies. Our mock remnants define a thin FP that perfectly fits data from all kinds of giant ETGs in the local volume, showing the existence of a unified relationship for these systems. High-ranked galaxies occupy in the FP different areas than standard objects, a segregation which is viewed essentially as zero-point offsets in the 2D correlations arising from standard projections of this plane. Our findings make a strong case for considering hierarchical dissipationless merging a viable route for the formation of the largest galaxies in the Universe.

  6. The Quest for the Largest Depleted Galaxy Core: Supermassive Black Hole Binaries and Stalled Infalling Satellites

    Science.gov (United States)

    Bonfini, Paolo; Graham, Alister W.

    2016-10-01

    Partially depleted cores are practically ubiquitous in luminous early-type galaxies (M B ≲ -20.5 mag) and are typically smaller than 1 kpc. In one popular scenario, supermassive black hole (SMBH) binaries—established during dry (i.e., gas-poor) galaxy mergers—kick out the stars from a galaxy’s central region via three-body interactions. Here, this “binary black hole scouring scenario” is probed at its extremes by investigating the two galaxies reported to have the largest partially depleted cores found to date: 2MASX J09194427+5622012 and 2MASX J17222717+3207571 (the brightest galaxy in Abell 2261). We have fit these galaxy’s two-dimensional light distribution using the core-Sérsic model and found that the former galaxy has a core-Sérsic break radius {R}b,{cS}=0.55 {{kpc}}, which is three times smaller than the published value. We use this galaxy to caution that other reportedly large break radii may too have been overestimated if they were derived using the “sharp-transition” (inner core)-to-(outer Sérsic) model. In the case of 2MASX J17222717+3207571, we obtain R b,cS = 3.6 kpc. While we confirm that this is the biggest known partially depleted core of any galaxy, we stress that it is larger than expected from the evolution of SMBH binaries—unless one invokes substantial gravitational-wave-induced (black hole-)recoil events. Given the presence of multiple nuclei located (in projection) within the core radius of this galaxy, we explored and found support for the alternative “stalled infalling perturber” core-formation scenario, in which this galaxy’s core could have been excavated by the action of an infalling massive perturber.

  7. Oscillatory relaxation of a merging galaxy cluster

    CERN Document Server

    Faltenbacher, A; Mathews, W G

    2006-01-01

    Within the cosmic framework clusters of galaxies are relatively young objects. Many of them have recently experienced major mergers. Here we investigate an equal mass merging event at z = ~0.6 resulting in a dark matter haloe of ~2.2 times 10^{14} Msol/h at z=0. The merging process is covered by 270 outputs of a high resolution cosmological N-body simulation performed with the ART (adaptive refinement tree) code. Some 2 Gyrs elapse between the first peri-centre passage of the progenitor cores and their final coalescence. During that phase the cores experience six peri-centre passages with minimal distances declining from ~30 to ~2 kpc/h. The time intervals between the peri-centre passages continuously decrease from 9 to 1 times 10^8 yrs. We follow the mean density, the velocity dispersion and the entropy of the two progenitors within a set of fixed proper radii (25, 50, 100, 250, 500, 1000 kpc/h). During the peri-centre passages we find sharp peaks of the mean densities within these radii, which exceed the su...

  8. Constraining gravity at the largest scales through CMB lensing and galaxy velocities

    Science.gov (United States)

    Pullen, Anthony R.; Alam, Shadab; He, Siyu; Ho, Shirley

    2016-08-01

    We demonstrate a new method to constrain gravity on the largest cosmological scales by combining measurements of cosmic microwave background (CMB) lensing and the galaxy velocity field. EG is a statistic, constructed from a gravitational lensing tracer and a measure of velocities such as redshift-space distortions (RSD), that can discriminate between gravity models while being independent of clustering bias and σ8. While traditionally, the lensing field for EG has been probed through galaxy lensing, CMB lensing has been proposed as a more robust tracer of the lensing field for EG at higher redshifts while avoiding intrinsic alignments. We perform the largest-scale measurement of EG ever, up to 150 Mpc h-1, by cross-correlating the Planck CMB lensing map with the Sloan Digital Sky Survey III (SDSS-III) CMASS galaxy sample and combining this with our measurement of the CMASS auto-power spectrum and the RSD parameter β. We report EG(z = 0.57) = 0.243 ± 0.060 (stat) ± 0.013 (sys), a measurement in tension with the general relativity (GR) prediction at a level of 2.6σ. Note that our EG measurement deviates from GR only at scales greater than 80 Mpc h-1, scales which have not been probed by previous EG tests. Upcoming surveys, which will provide an order-of-magnitude reduction in statistical errors, can significantly constrain alternative gravity models when combined with better control of systematics.

  9. Constraining Gravity at the Largest Scales through CMB Lensing and Galaxy Velocities

    CERN Document Server

    Pullen, Anthony R; He, Siyu; Ho, Shirley

    2015-01-01

    We demonstrate a new method to constrain gravity on the largest cosmological scales by combining measurements of cosmic microwave background (CMB) lensing and the galaxy velocity field. $E_G$ is a statistic, constructed from a gravitational lensing tracer and a measure of velocities such as redshift-space distortions (RSD), that can discriminate between gravity models while being independent of clustering bias and $\\sigma_8$. While traditionally, the lensing field for $E_G$ has been probed through galaxy lensing, CMB lensing has been proposed as a more robust tracer of the lensing field for $E_G$ at higher redshifts while avoiding intrinsic alignments. We perform the largest-scale measurement of $E_G$ ever, up to 150 Mpc/$h$, by cross-correlating the Planck CMB lensing map with the Sloan Digital Sky Survey III (SDSS-III) CMASS galaxy sample and combining this with our measurement of the CMASS auto-power spectrum and the RSD parameter $\\beta$. We report $E_G(z=0.57)=0.243\\pm0.060$ (stat) $\\pm0.013$ (sys), a me...

  10. THE BRIGHTEST CLUSTER GALAXY IN A85: THE LARGEST CORE KNOWN SO FAR

    Energy Technology Data Exchange (ETDEWEB)

    López-Cruz, O.; Añorve, C.; Ibarra-Medel, H. J. [Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), Astrofísica, Luis Enrique Erro No.1, Tonantzintla, Pue., C.P. 72840 (Mexico); Birkinshaw, M.; Worrall, D. M. [HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL (United Kingdom); Barkhouse, W. A. [Department of Physics and Astrophysics, University of North Dakota, Grand Forks, ND 58202 (United States); Torres-Papaqui, J. P. [Departamento de Astronomía, Universidad de Guanajuato (DAUG), Callejón Jalisco S/N Col. Valenciana, C.P. 36240 Guanajuato, Gto. (Mexico); Motta, V., E-mail: omarlx@inaoep.mx [Instituto de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretaña 1111 Varaíso (Chile)

    2014-11-10

    We have found that the brightest cluster galaxy (BCG) in A85, Holm 15A, displays the largest core known so far. Its cusp radius, r {sub γ} = 4.57 ± 0.06 kpc (4.''26 ± 0.''06), is more than 18 times larger than the mean for BCGs and ≳ 1 kpc larger than A2261-BCG, hitherto the largest-cored BCG. Holm 15A hosts the luminous amorphous radio source 0039-095B and has the optical signature of a LINER. Scaling laws indicate that this core could host a supermassive black hole (SMBH) of mass M {sub •} ∼ (10{sup 9}-10{sup 11}) M {sub ☉}. We suggest that cores this large represent a relatively short phase in the evolution of BCGs, whereas the masses of their associated SBMH might be set by initial conditions.

  11. Hot plasma in clusters of galaxies, the largest objects in the universe

    CERN Document Server

    Sarazin, C L

    2003-01-01

    Clusters of galaxies are the largest organized structures in the Universe. They are important cosmological probes, since they are large enough to contain a fair sample of the materials in the Universe, but small enough to have achieved dynamical equilibrium. Clusters were first discovered as concentrations of hundreds of bright galaxies in a region about 3 megaparsecs (10 million light years) across. However, the dominant observed form of matter in clusters is hot, diffuse intergalactic gas. This intracluster plasma has typical temperatures of T ~ 7e7 K, and typical electron densities of n_e ~ 10^{-3} cm^{-3}. This intracluster plasma mainly emits X-rays, and typical cluster X-ray luminosities are L_X ~ 10^{43} - 10^{45} erg/s. The basic properties of and physical processes in the intracluster plasma will be reviewed. Important observational constraints on plasma processes in these systems will be discussed. Recent X-ray observations of clusters of galaxies with the orbiting Chandra X-ray Observatory will be ...

  12. Violent Relaxation, Dynamical Instabilities and the Formation of Elliptical Galaxies

    Science.gov (United States)

    Aguilar, L. A.

    1990-11-01

    RESUMEN: El problema de la formaci6n de galaxias elfpticas por medjo de colapso gravitacional sin disipaci6n de energfa es estudiado usando un gran numero de simulaciones numericas. Se muestra que este tipo de colapsos, partiendo de condiciones iniciales frfas donde la energfa cinetica inicial representa s6lo un 5%, 0 , de a potencial inicial, produce sistemas relajados de forma triaxial muy similares a las galaxias elfpticas reales en sus formas y perfiles de densidad en proyecci6i . La forina triaxial resulta de la acci6n de una inestabilidad dinamica que aparece en sistemas 'inicos dominados por movimientos radiales, mientras que el perfil de densidad final Cs debido al llamado relajamiento violento que tiende a producir una distribuci6n en espacio fase unica. Estos dos fen6menos tienden a borrar los detalles particulares sobre las condiciones iniciales y dan lugar a una evoluci6n convergente hacia sistemas realistas, esto innecesario el uso de condiciones iniciales especiales (excepto por Ia condici6i de que estas deben ser frfas). Las condiciones iniciales frfas producen los movimientos radiales y fluctuaciones de la energfa potencial requeridos por ambos fen6menos. ABSTRACT: The problem of formation of elliptical galaxies via dissipationless collapse is studied using a large set of numerical simulations. It is shown that dissipationless collapses from cold initial conditions, where the total initial kinetic energy is less than 5% ofthe initial potential energy, lead to relaxed triaxial systems ery similar to real elliptical galaxies ii projected shape and density profiles. The triaxial shape is due to the of a dynamical instability that appears on systems dominated by radial orbits, while final density profile is due to violent relaxation that tends to produce a unique distribution iii space. These two phenomena erase memory of the initial prodtice a convergent evolution toward realistic systems, thus making unnecessary use o[special initial conditions (other

  13. Cosmology and astrophysics from relaxed galaxy clusters - II. Cosmological constraints

    Science.gov (United States)

    Mantz, A. B.; Allen, S. W.; Morris, R. G.; Rapetti, D. A.; Applegate, D. E.; Kelly, P. L.; von der Linden, A.; Schmidt, R. W.

    2014-05-01

    This is the second in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. The data set employed here consists of Chandra observations of 40 such clusters, identified in a comprehensive search of the Chandra archive for hot (kT ≳ 5 keV), massive, morphologically relaxed systems, as well as high-quality weak gravitational lensing data for a subset of these clusters. Here we present cosmological constraints from measurements of the gas mass fraction, fgas, for this cluster sample. By incorporating a robust gravitational lensing calibration of the X-ray mass estimates, and restricting our measurements to the most self-similar and accurately measured regions of clusters, we significantly reduce systematic uncertainties compared to previous work. Our data for the first time constrain the intrinsic scatter in fgas, 7.4 ± 2.3 per cent in a spherical shell at radii 0.8-1.2 r2500 (˜1/4 of the virial radius), consistent with the expected level of variation in gas depletion and non-thermal pressure for relaxed clusters. From the lowest redshift data in our sample, five clusters at z 1, we obtain consistent results for Ωm and interesting constraints on dark energy: Ω _{{Λ }}=0.65^{+0.17}_{-0.22}> for non-flat ΛCDM (cosmological constant) models, and w = -0.98 ± 0.26 for flat models with a constant dark energy equation of state. Our results are both competitive and consistent with those from recent cosmic microwave background, Type Ia supernova and baryon acoustic oscillation data. We present constraints on more complex models of evolving dark energy from the combination of fgas data with these external data sets, and comment on the possibilities for improved fgas constraints using current and next-generation X-ray observatories and lensing data.

  14. The quest for the largest depleted galaxy core: supermassive black hole binaries and stalled in-falling satellites

    CERN Document Server

    Bonfini, Paolo

    2016-01-01

    Partially-depleted cores are practically ubiquitous in luminous early-type galaxies (M$_{B}\\lesssim-$20.5 mag), and typically smaller than 1 kpc. In one popular scenario, supermassive black hole binaries --- established during dry (i.e. gas-poor) galaxy mergers --- kick out the stars from a galaxy's central region via three-body interactions. Here, this "binary black hole scouring scenario" is probed at its extremes by investigating the two galaxies reported to have the largest partially-depleted cores found to date: 2MASX~J09194427+5622012 and 2MASX~J17222717+3207571 (the brightest galaxy in Abell~2261). We have fit these galaxy's two-dimensional light distribution using the core-S\\'{e}rsic model, and found that the former galaxy has a core-S\\'{e}rsic break radius $R_{b,cS}=0.55$~kpc, three times smaller than the published value. We use this galaxy to caution that other reportedly large break radii may too have been over-estimated if they were derived using the "sharp-transition" (inner core)-to-(outer S\\'{e...

  15. Astronomer's new guide to the galaxy: largest map of cold dust revealed

    Science.gov (United States)

    2009-07-01

    Astronomers have unveiled an unprecedented new atlas of the inner regions of the Milky Way, our home galaxy, peppered with thousands of previously undiscovered dense knots of cold cosmic dust -- the potential birthplaces of new stars. Made using observations from the APEX telescope in Chile, this survey is the largest map of cold dust so far, and will prove an invaluable map for observations made with the forthcoming ALMA telescope, as well as the recently launched ESA Herschel space telescope. ESO PR Photo 24a/09 View of the Galactic Plane from the ATLASGAL survey (annotated and in five sections) ESO PR Photo 24b/09 View of the Galactic Plane from the ATLASGAL survey (annotated) ESO PR Photo 24c/09 View of the Galactic Plane from the ATLASGAL survey (in five sections) ESO PR Photo 24d/09 View of the Galactic Plane from the ATLASGAL survey ESO PR Photo 24e/09 The Galactic Centre and Sagittarius B2 ESO PR Photo 24f/09 The NGC 6357 and NGC 6334 nebulae ESO PR Photo 24g/09 The RCW120 nebula ESO PR Video 24a/09 Annotated pan as seen by the ATLASGAL survey This new guide for astronomers, known as the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) shows the Milky Way in submillimetre-wavelength light (between infrared light and radio waves [1]). Images of the cosmos at these wavelengths are vital for studying the birthplaces of new stars and the structure of the crowded galactic core. "ATLASGAL gives us a new look at the Milky Way. Not only will it help us investigate how massive stars form, but it will also give us an overview of the larger-scale structure of our galaxy", said Frederic Schuller from the Max Planck Institute for Radio Astronomy, leader of the ATLASGAL team. The area of the new submillimetre map is approximately 95 square degrees, covering a very long and narrow strip along the galactic plane two degrees wide (four times the width of the full Moon) and over 40 degrees long. The 16 000 pixel-long map was made with the LABOCA submillimetre

  16. A large Hα survey of star formation in relaxed and merging galaxy cluster environments at z ∼ 0.15-0.3

    Science.gov (United States)

    Stroe, Andra; Sobral, David; Paulino-Afonso, Ana; Alegre, Lara; Calhau, João; Santos, Sergio; van Weeren, Reinout

    2017-03-01

    We present the first results from the largest Hα survey of star formation and active galactic nucleus activity in galaxy clusters. Using nine different narrow-band filters, we select >3000 Hα emitters within 19 clusters and their larger scale environment over a total volume of 1.3 × 105 Mpc3. The sample includes both relaxed and merging clusters, covering the 0.15-0.31 redshift range and spanning from 5 × 1014 to 30 × 1014 M⊙. We find that the Hα luminosity function for merging clusters has a higher characteristic density ϕ* compared to relaxed clusters. ϕ* drops from cluster core to cluster outskirts for both merging and relaxed clusters, with the merging cluster values ∼0.3 dex higher at each projected radius. The characteristic luminosity L* drops over the 0.5-2.0 Mpc distance from the cluster centre for merging clusters and increases for relaxed objects. Among disturbed objects, clusters hosting large-scale shock waves (traced by radio relics) are overdense in Hα emitters compared to those with turbulence in their intracluster medium (traced by radio haloes). We speculate that the increase in star formation activity in disturbed, young, massive galaxy clusters can be triggered by interactions between gas-rich galaxies, shocks and/or the intracluster medium, as well as accretion of filaments and galaxy groups. Our results indicate that disturbed clusters represent vastly different environments for galaxy evolution compared to relaxed clusters or average field environments.

  17. Intensity mapping cross-correlations: connecting the largest scales to galaxy evolution

    Science.gov (United States)

    Wolz, L.; Tonini, C.; Blake, C.; Wyithe, J. S. B.

    2016-05-01

    Intensity mapping of the neutral hydrogen (H I) is a new observational tool to efficiently map the large-scale structure over wide redshift ranges. The cross-correlation of intensity maps with galaxy surveys is a robust measure of the cosmological power spectrum and the H I content of galaxies which diminishes systematics caused by instrumental effects and foreground removal. We examine the cross-correlation signature at redshift 0.9 using a semi-analytical galaxy formation model in order to model the H I gas of galaxies as well as their optical magnitudes. We determine the scale-dependent clustering of the cross-correlation power for different types of galaxies determined by their colours, which act as a proxy for their star formation activity. We find that the cross-correlation coefficient with H I density for red quiescent galaxies falls off more quickly on smaller scales k > 0.2 h Mpc-1 than for blue star-forming galaxies. Additionally, we create a mock catalogue of highly star-forming galaxies to mimic the WiggleZ Dark Energy Survey, and use this to predict existing and future measurements using data from the Green Bank telescope and Parkes telescope. We find that the cross-power of highly star-forming galaxies shows a higher clustering on small scales than any other galaxy type and that this significantly alters the power spectrum shape on scales k > 0.2 h Mpc-1. We show that the cross-correlation coefficient is not negligible when interpreting the cosmological cross-power spectrum and additionally contains information about the H I content of the optically selected galaxies.

  18. Unveiling the formation route of the largest galaxies in the universe

    CERN Document Server

    Perea, Jaime D

    2016-01-01

    Observational evidence indicates that the role of gas is secondary to that of gravity in the formation of the most luminous spheroids inhabiting the centres of galaxy associations, as originally conjectured in the late 80's/early 90's. However, attempts to explain the origin of the Fundamental Plane (FP) of massive early-type galaxies (ETGs) -- a tilted version of the scaling relation connecting the size, velocity dispersion and mass of virialized homologous systems -- based on sequences of pairwise mergers, have systematically concluded that dissipation cannot be ignored. We use controlled simulations of the previrialization stage of galaxy groups to show that multiple collisionless merging is capable of creating realistic first-ranked galaxies. Our mock remnants define a thin FP that perfectly fits data from all kinds of giant ETGs in the local volume, showing the existence of a unified relationship for these systems. High-ranked galaxies occupy in the FP different areas than standard objects, a segregation...

  19. Star Formation Histories Across the Interacting Galaxy NGC 6872, the Largest-Known Spiral

    CERN Document Server

    Eufrasio, Rafael T; Arendt, Richard G; de Mello, Duilia F; Gadotti, Dimitri; Urrutia-Viscarra, Fernanda; de Oliveira, Claudia Mendes; Benford, Dominic

    2014-01-01

    NGC 6872, hereafter the Condor, is a large spiral galaxy that is interacting with its closest companion, the S0 galaxy IC 4970. The extent of the Condor provides an opportunity for detailed investigation of the impact of the interaction on the current star formation rate and its history across the galaxy, on the age and spatial distribution of its stellar population, and on the mechanism that drive the star formation activity. To address these issues we analyzed the far-ultraviolet (FUV) to near-infrared (near-IR) spectral energy distribution (SED) of 17, 10 kpc diameter, regions across the galaxy, and derived their star formation history, current star formation rate, and stellar population and mass. We find that most of the star formation takes place in the extended arms, with very little star formation in the central 5 kpc of the galaxy, in contrast to what was predicted from previous numerical simulations. There is a trend of increasing star formation activity with distance from the nucleus of the galaxy, ...

  20. Intensity Mapping Cross-Correlations: Connecting the Largest Scales to Galaxy Evolution

    CERN Document Server

    Wolz, L; Blake, C; Wyithe, J S B

    2015-01-01

    Intensity mapping of the neutral hydrogen (HI) is a new observational tool that can be used to efficiently map the large-scale structure of the Universe over wide redshift ranges. The power spectrum of the intensity maps contains cosmological information on the matter distribution and probes galaxy evolution by tracing the HI content of galaxies at different redshifts and the scale-dependence of HI clustering. The cross-correlation of intensity maps with galaxy surveys is a robust measure of the power spectrum which diminishes systematics caused by instrumental effects and foreground removal. We examine the cross-correlation signature at redshift z=0.9 using a variant of the semi-analytical galaxy formation model SAGE (Croton et al. 2016) applied to the Millennium simulation in order to model the HI gas of galaxies as well as their optical magnitudes based on their star-formation history. We determine the clustering of the cross-correlation power for different types of galaxies determined by their colours, ac...

  1. STAR Formation Histories Across the Interacting Galaxy NGC 6872, the Largest-Known Spiral

    Science.gov (United States)

    Eufrasio, Rafael T.; Dwek, E.; Arendt, RIchard G.; deMello, Duilia F.; Gadotti, DImitri A.; Urrutia-Viscarra, Fernanda; deOliveira, CLaudia Mendes; Benford, Dominic J.

    2014-01-01

    NGC6872, hereafter the Condor, is a large spiral galaxy that is interacting with its closest companion, the S0 galaxy IC 4970. The extent of the Condor provides an opportunity for detailed investigation of the impact of the interaction on the current star formation rate and its history across the galaxy, on the age and spatial distribution of its stellar population, and on the mechanism that drives the star formation activity. To address these issues we analyzed the far-ultraviolet (FUV) to near-infrared (near-IR) spectral energy distribution of seventeen 10 kpc diameter regions across the galaxy, and derived their star formation history, current star formation rate, and stellar population and mass. We find that most of the star formation takes place in the extended arms, with very little star formation in the central 5 kpc of the galaxy, in contrast to what was predicted from previous numerical simulations. There is a trend of increasing star formation activity with distance from the nucleus of the galaxy, and no evidence for a recent increase in the current star formation rate due to the interaction. The nucleus itself shows no significant current star formation activity. The extent of the Condor also provides an opportunity to test the applicability of a single standard prescription for conversion of the FUV + IR (22 micrometer) intensities to a star formation rate for all regions. We find that the conversion factor differs from region to region, arising from regional differences in the stellar populations.

  2. Galaxy evolution in nearby galaxy groups. III. A GALEX view of NGC 5846, the largest group in the local universe

    CERN Document Server

    Marino, Antonietta; Rampazzo, Roberto; Bianchi, Luciana

    2016-01-01

    We explore the co-evolution of galaxies in nearby groups (V < 3000 km/s) with a multi-wavelength approach. We analyze GALEX far-UV (FUV) and near-UV (NUV) imaging and SDSS u,g,r,i,z data of groups spanning a large range of dynamical phases. We characterize the photometric properties of spectroscopically-confirmed galaxy members and investigate the global properties of the groups through a dynamical analysis. Here we focus on NGC 5846, the third most massive association of Early-Type Galaxies (ETG) after the Virgo and Fornax clusters. The group, composed of 90 members, is dominated by ETGs (about 80 per cent), and among ETGs about 40\\% are dwarfs. Results are compared with those obtained for three groups in the LeoII cloud, which are radically different both in member-galaxy population and dynamical properties. The FUV-NUV cumulative colour distribution and the normalized UV luminosity function (LF) significantly differ due to the different fraction of late-type galaxy population. The UV LF of NGC 5846 rese...

  3. Energy relaxation in galaxies induced by an external environment and/or incoherent internal pulsations

    CERN Document Server

    Kandrup, H E

    2001-01-01

    This paper explores the phenomenon of energy relaxation for stars in a galaxy embedded in a high density environment that is subjected continually to perturbations reflecting the presence of other nearby galaxies and/or incoherent internal pulsations. The analysis is similar to earlier analyses of energy relaxation induced by binary encounters between nearby stars and between stars and giant molecular clouds in that the perturbations are idealised as a sum of near-random events which can be modeled as diffusion and dynamical friction. However, the analysis differs in one important respect: because the time scale associated with these perturbations need not be short compared with the characteristic dynamical time t_D for stars in the original galaxy, the diffusion process cannot be modeled as resulting from a sequence of instantaneous kicks, i.e., white noise. Instead, the diffusion is modeled as resulting from random kicks of finite duration, i.e., coloured noise characterised by a nonzero autocorrelation tim...

  4. Energetic Impact of Jet Inflated Cocoons in Relaxed Galaxy Clusters

    OpenAIRE

    Vernaleo, John C.; Christopher S. Reynolds

    2007-01-01

    Jets from active galactic nuclei (AGN) in the cores of galaxy clusters have the potential to be a major contributor to the energy budget of the intracluster medium (ICM). To study the dependence of the interaction between the AGN jets and the ICM on the parameters of the jets themselves, we present a parameter survey of two-dimensional (axisymmetric) ideal hydrodynamic models of back-to-back jets injected into a cluster atmosphere (with varying Mach numbers and kinetic luminosities). We follo...

  5. Energetic Impact of Jet Inflated Cocoons in Relaxed Galaxy Clusters

    CERN Document Server

    Vernaleo, John C

    2007-01-01

    Jets from active galactic nuclei (AGN) in the cores of galaxy clusters have the potential to be a major contributor to the energy budget of the intracluster medium (ICM). To study the dependence of the interaction between the AGN jets and the ICM on the parameters of the jets themselves, we present a parameter survey of two-dimensional (axisymmetric) ideal hydrodynamic models of back-to-back jets injected into a cluster atmosphere (with varying Mach numbers and kinetic luminosities). We follow the passive evolution of the resulting structures for several times longer than the active lifetime of the jet. The simulations fall into roughly two classes, cocoon-bounded and non-cocoon bounded sources. We suggest a correspondence between these two classes and the Faranoff-Riley types. We find that the cocoon-bounded sources inject significantly more entropy into the core regions of the ICM atmosphere, even though the efficiency with which energy is thermalized is independent of the morphological class. In all cases,...

  6. Cosmology and Astrophysics from Relaxed Galaxy Clusters III: Thermodynamic Profiles and Scaling Relations

    CERN Document Server

    Mantz, Adam B; Morris, R Glenn; Schmidt, Robert W

    2016-01-01

    This is the third in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot (i.e., massive) in Papers I and II of this series. Here we consider the thermodynamics of the intracluster medium, in particular the profiles of density, temperature and related quantities, as well as integrated measurements of gas mass, average temperature, total luminosity and center-excluded luminosity. We fit power-law scaling relations of each of these quantities as a function of redshift and cluster mass, which can be measured precisely and with minimal bias for these relaxed clusters. For the thermodynamic profiles, we jointly model the density and temperature and their intrinsic scatter as a function of radius, thus also capturing the behavior of the gas pressure and entropy. For the integrated quantities, we also jointly fit a multidimensional intrinsic covariance, providing the first observati...

  7. SDSS-II Supernova Survey: An Analysis of the Largest Sample of Type Ia Supernovae and Correlations with Host-Galaxy Spectral Properties

    CERN Document Server

    Wolf, Rachel C; Gupta, Ravi R; Sako, Masao; Fischer, John A; Kessler, Rick; Jha, Saurabh W; March, Marisa C; Scolnic, Daniel M; Fischer, Johanna-Laina; Campbell, Heather; Nichol, Robert C; Olmstead, Matthew D; Richmond, Michael; Schneider, Donald P; Smith, Mathew

    2016-01-01

    Using the largest single-survey sample of Type Ia supernovae (SNe Ia) to date, we study the relationship between properties of SNe Ia and those of their host galaxies, focusing primarily on correlations with Hubble residuals (HR). Our sample consists of 345 photometrically-classified or spectroscopically-confirmed SNeIa discovered as part of the SDSS-II Supernova Survey (SDSS-SNS). This analysis utilizes host-galaxy spectroscopy obtained during the SDSS-I/II spectroscopic survey and from an ancillary program on the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) that obtained spectra for nearly all host galaxies of SDSS-II SN candidates. In addition, we use photometric host-galaxy properties from the SDSS-SNS data release (Sako et al. 2014) such as host stellar mass and star-formation rate. We confirm the well-known relation between HR and host-galaxy mass and find a 3.6{\\sigma} significance of a non-zero linear slope. We also recover correlations between HR and host-galaxy gas-phase metallicity and s...

  8. A large H$\\alpha$ survey of star formation in relaxed and merging galaxy cluster environments at $z\\sim0.15-0.3$

    CERN Document Server

    Stroe, Andra; Afonso, Ana; Alegre, Lara; Calhau, João; Santos, Sergio; van Weeren, Reinout

    2016-01-01

    We present the first results from the largest H$\\alpha$ survey of star formation and AGN activity in galaxy clusters. Using 9 different narrow band filters, we select $>3000$ H$\\alpha$ emitters within $19$ clusters and their larger scale environment over a total volume of $1.3\\times10^5$ Mpc$^3$. The sample includes both relaxed and merging clusters, covering the $0.15-0.31$ redshift range and spanning from $5\\times10^{14}$ $M_{\\odot}$ to $30\\times10^{14}$ $M_{\\odot}$. We find that the H$\\alpha$ luminosity function (LF) for merging clusters has a higher characteristic density $\\phi^*$ compared to relaxed clusters. $\\phi^*$ drops from cluster core to cluster outskirts for both merging and relaxed clusters, with the merging cluster values $\\sim0.3$ dex higher at each projected radius. The characteristic luminosity $L^*$ drops over the $0.5-2.0$ Mpc distance from the cluster centre for merging clusters and increases for relaxed objects. Among disturbed objects, clusters hosting large-scale shock waves (traced by...

  9. Cosmology and Astrophysics from Relaxed Galaxy Clusters V: Consistency with Cold Dark Matter Structure Formation

    CERN Document Server

    Mantz, Adam B; Morris, R Glenn

    2016-01-01

    This is the fifth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot in Papers I and II of this series. Here we use constraints on cluster mass profiles from X-ray data to test some of the basic predictions of cosmological structure formation in the Cold Dark Matter (CDM) paradigm. We present constraints on the concentration--mass relation for massive clusters, finding a power-law mass dependence with a slope of $\\kappa_m=-0.16\\pm0.07$, in agreement with CDM predictions. For this relaxed sample, the relation is consistent with a constant as a function of redshift (power-law slope with $1+z$ of $\\kappa_\\zeta=-0.17\\pm0.26$), with an intrinsic scatter of $\\sigma_{\\ln c}=0.16\\pm0.03$. We investigate the shape of cluster mass profiles over the radial range probed by the data (typically $\\sim50$kpc--1Mpc), and test for departures from the simple Navarro, Frenk & White (NFW...

  10. SDSS-II Supernova survey. An analysis of the largest sample of type IA supernovae and correlations with host-galaxy spectral properties

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, Rachel C.; D’Andrea, Chris B.; Gupta, Ravi R.; Sako, Masao; Fischer, John A.; Kessler, Rick; Jha, Saurabh W.; March, Marisa C.; Scolnic, Daniel M.; Fischer, Johanna-Laina; Campbell, Heather; Nichol, Robert C.; Olmstead, Matthew D.; Richmond, Michael; Schneider, Donald P.; Smith, Mathew

    2016-04-20

    Using the largest single-survey sample of Type Ia supernovae (SNe Ia) to date, we study the relationship between properties of SNe Ia and those of their host galaxies, focusing primarily on correlations with Hubble residuals (HR). Our sample consists of 345 photometrically-classified or spectroscopicallyconfirmed SNe Ia discovered as part of the SDSS-II Supernova Survey (SDSS-SNS). This analysis utilizes host-galaxy spectroscopy obtained during the SDSS-I/II spectroscopic survey and from an ancillary program on the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) that obtained spectra for nearly all host galaxies of SDSS-II SN candidates. In addition, we use photometric hostgalaxy properties from the SDSS-SNS data release (Sako et al. 2014) such as host stellar mass and star-formation rate. We confirm the well-known relation between HR and host-galaxy mass and find a 3.6σ significance of a non-zero linear slope. We also recover correlations between HR and hostgalaxy gas-phase metallicity and specific star-formation rate as they are reported in the literature. With our large dataset, we examine correlations between HR and multiple host-galaxy properties simultaneously and find no evidence of a significant correlation. We also independently analyze our spectroscopically-confirmed and photometrically-classified SNe Ia and comment on the significance of similar combined datasets for future surveys.

  11. PPAK Wide-field Integral Field Spectroscopy of NGC 628: I. The largest spectroscopic mosaic on a single galaxy

    CERN Document Server

    Sanchez, S F; Kennicutt, R C; Johnson, B D; Diaz, A I; Pasquali, A; Hao, C N

    2010-01-01

    We present a wide-field IFS survey on the nearby face-on Sbc galaxy NGC 628, comprising 11094 individual spectra, covering a nearly circular field-of-view of ~6 arcmin in diameter, with a sampling of ~2.7 arcsec per spectrum in the optical wavelength range (3700--7000 AA). This galaxy is part of the PPAK IFS Nearby Galaxies Survey, (PINGS, Rosales-Ortega et al. 2009). To our knowledge, this is the widest spectroscopic survey ever made in a single nearby galaxy. A detailed flux calibration was applied, granting a spectrophotometric accuracy of $\\sim$\\,0.2 mag. The age of the stellar populations shows a negative gradient from the inner (older) to the outer (younger) regions. We found an inversion of this gradient in the central ~1 kpc region, where a somewhat younger stellar population is present within a ring at this radius. This structure is associated with a circumnuclear star-forming region at ~ 500 pc, also found in similar spiral galaxies. From the study of the integrated and spatially resolved ionized ga...

  12. The Brightest Galaxies at Cosmic Dawn: Securing the Largest Samples of z=9-11 galaxies for JWST by leveraging the HST archive with Spitzer/IRAC.

    Science.gov (United States)

    Bouwens, Rychard; Trenti, Michele; Calvi, Valentina; Bernard, Stephanie; Labbe, Ivo; Oesch, Pascal; Coe, Dan; Holwerda, Benne; Bradley, Larry; Mason, Charlotte; Schmidt, Kasper; Illingworth, Garth

    2015-10-01

    Hubble's WFC3 has been a game changer for studying early galaxy formation in the first 700 Myr after the Big Bang. Reliable samples of sources up to z~10, which can be discovered only from space, are now constraining the evolution of the galaxy luminosity function into the epoch of reionization. Despite these efforts, the size of the highest redshift galaxy samples (z >9 and especially z > 10) is still very small, particularly at high luminosities (L > L*). To deliver transformational results, much larger numbers of bright z > 9 galaxies are needed both to map out the bright end of the luminosity/mass function and for spectroscopic follow-up (with JWST and otherwise). One especially efficient way of expanding current samples is (1) to leverage the huge amounts of pure-parallel data available with HST to identify large numbers of candidate z ~ 9 - 11 galaxies and (2) to follow up each candidate with shallow Spitzer/IRAC observations to distinguish the bona- fide z ~ 9 - 11 galaxies from z ~ 2 old, dusty galaxies. For this program we are requesting shallow Spitzer/IRAC follow-up of 20 candidate z ~ 9 - 11 galaxies we have identified from 130 WFC3/IR pointings obtained from more than 4 separate HST programs with no existing IRAC coverage. Based on our previous CANDELS/GOODS searches, we expect to confirm 5 to 10 sources as L > L* galaxies at z >= 9. Our results will be used to constrain the bright end of the LF at z >= 9, to provide targets for Keck spectroscopy to constrain the ionization state of the z > 8 universe, and to furnish JWST with bright targets for spectroscopic follow-up studies.

  13. Cosmology and astrophysics from relaxed galaxy clusters - IV: Robustly calibrating hydrostatic masses with weak lensing

    CERN Document Server

    Applegate, D E; Allen, S W; von der Linden, A; Morris, R G; Hilbert, S; Kelly, P L; Burke, D L; Ebeling, H; Rapetti, D A; Schmidt, R W

    2015-01-01

    This is the fourth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Here, we use measurements of weak gravitational lensing from the Weighing the Giants project to calibrate Chandra X-ray measurements of total mass that rely on the assumption of hydrostatic equilibrium. This comparison of X-ray and lensing masses provides a measurement of the combined bias of X-ray hydrostatic masses due to both astrophysical and instrumental sources. Assuming a fixed cosmology, and within a characteristic radius (r_2500) determined from the X-ray data, we measure a lensing to X-ray mass ratio of 0.96 +/- 9% (stat) +/- 9% (sys). We find no significant trends of this ratio with mass, redshift or the morphological indicators used to select the sample. In accordance with predictions from hydro simulations for the most massive, relaxed clusters, our results disfavor strong, tens-of-percent departures from hydrostatic equilibrium at these radii. In addition, we find a m...

  14. Cosmology and astrophysics from relaxed galaxy clusters – V. Consistency with cold dark matter structure formation

    Energy Technology Data Exchange (ETDEWEB)

    Mantz, A.B.; /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Allen, S.W.; /KIPAC, Menlo Park /Stanford U., Phys. Dept. /SLAC; Morris, R.Glenn; /KIPAC, Menlo Park /SLAC

    2016-07-15

    This is the fifth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot in Papers I and II of this series. Here we use constraints on cluster mass profiles from X-ray data to test some of the basic predictions of cosmological structure formation in the cold dark matter (CDM) paradigm. We present constraints on the concentration–mass relation for massive clusters, finding a power-law mass dependence with a slope of κm = -0.16 ± 0.07, in agreement with CDM predictions. For this relaxed sample, the relation is consistent with a constant as a function of redshift (power-law slope with 1 + z of κζ = -0.17 ± 0.26), with an intrinsic scatter of σln c = 0.16 ± 0.03. We investigate the shape of cluster mass profiles over the radial range probed by the data (typically ~50 kpc–1 Mpc), and test for departures from the simple Navarro–Frenk–White (NFW) form, for which the logarithmic slope of the density profile tends to -1 at small radii. Specifically, we consider as alternatives the generalized NFW (GNFW) and Einasto parametrizations. For the GNFW model, we find an average value of (minus) the logarithmic inner slope of β = 1.02 ± 0.08, with an intrinsic scatter of σβ = 0.22 ± 0.07, while in the Einasto case we constrain the average shape parameter to be α = 0.29 ± 0.04 with an intrinsic scatter of σα = 0.12 ± 0.04. Our results are thus consistent with the simple NFW model on average, but we clearly detect the presence of intrinsic, cluster-to-cluster scatter about the average.

  15. Cosmology and astrophysics from relaxed galaxy clusters - V. Consistency with cold dark matter structure formation

    Science.gov (United States)

    Mantz, A. B.; Allen, S. W.; Morris, R. G.

    2016-10-01

    This is the fifth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot in Papers I and II of this series. Here we use constraints on cluster mass profiles from X-ray data to test some of the basic predictions of cosmological structure formation in the cold dark matter (CDM) paradigm. We present constraints on the concentration-mass relation for massive clusters, finding a power-law mass dependence with a slope of κm = -0.16 ± 0.07, in agreement with CDM predictions. For this relaxed sample, the relation is consistent with a constant as a function of redshift (power-law slope with 1 + z of κζ = -0.17 ± 0.26), with an intrinsic scatter of σln c = 0.16 ± 0.03. We investigate the shape of cluster mass profiles over the radial range probed by the data (typically ˜50 kpc-1 Mpc), and test for departures from the simple Navarro-Frenk-White (NFW) form, for which the logarithmic slope of the density profile tends to -1 at small radii. Specifically, we consider as alternatives the generalized NFW (GNFW) and Einasto parametrizations. For the GNFW model, we find an average value of (minus) the logarithmic inner slope of β = 1.02 ± 0.08, with an intrinsic scatter of σβ = 0.22 ± 0.07, while in the Einasto case we constrain the average shape parameter to be α = 0.29 ± 0.04 with an intrinsic scatter of σα = 0.12 ± 0.04. Our results are thus consistent with the simple NFW model on average, but we clearly detect the presence of intrinsic, cluster-to-cluster scatter about the average.

  16. THE DENSITY PROFILES OF MASSIVE, RELAXED GALAXY CLUSTERS. I. THE TOTAL DENSITY OVER THREE DECADES IN RADIUS

    Energy Technology Data Exchange (ETDEWEB)

    Newman, Andrew B.; Ellis, Richard S. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Treu, Tommaso; Sand, David J. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Nipoti, Carlo [Astronomy Department, University of Bologna, via Ranzani 1, I-40127 Bologna (Italy); Richard, Johan [CRAL, Observatorie de Lyon, Universite Lyon 1, 9 Avenue Ch. Andre, F-69561 Saint Genis Laval Cedex (France); Jullo, Eric, E-mail: anewman@astro.caltech.edu [Laboratoire d' Astrophysique de Marseille, Universite d' Aix-Marseille and CNRS, UMR7326, 38 rue F. Joliot-Curie, F-13388 Marseille Cedex 13 (France)

    2013-03-01

    Clusters of galaxies are excellent locations to probe the distribution of baryons and dark matter (DM) over a wide range of scales. We study a sample of seven massive (M {sub 200} = 0.4-2 Multiplication-Sign 10{sup 15} M {sub Sun }), relaxed galaxy clusters with centrally located brightest cluster galaxies (BCGs) at z = 0.2-0.3. Using the observational tools of strong and weak gravitational lensing, combined with resolved stellar kinematics within the BCG, we measure the total radial density profile, comprising both dark and baryonic matter, over scales of {approx_equal} 3-3000 kpc. We present Keck spectroscopy yielding seven new spectroscopic redshifts of multiply imaged sources and extended stellar velocity dispersion profiles of the BCGs. Lensing-derived mass profiles typically agree with independent X-ray estimates within {approx_equal} 15%, suggesting that departures from hydrostatic equilibrium are small and that the clusters in our sample (except A383) are not strongly elongated or compressed along the line of sight. The inner logarithmic slope {gamma}{sub tot} of the total density profile measured over r/r {sub 200} = 0.003-0.03, where {rho}{sub tot}{proportional_to}r{sup -{gamma}{sub t}{sub o}{sub t}}, is found to be nearly universal, with a mean ({gamma}{sub tot}) = 1.16 {+-} 0.05(random){sup +0.05} {sub -0.07} (systematic) and an intrinsic scatter {sigma}{sub {gamma}} < 0.13 (68% confidence). This is further supported by the very homogeneous shape of the observed velocity dispersion profiles, which are mutually consistent after a simple scaling. Remarkably, this slope agrees closely with high-resolution numerical simulations that contain only DM, despite the significant contribution of stellar mass on the scales we probe. The Navarro-Frenk-White profile characteristic of collisionless cold DM is a better description of the total mass density at radii {approx}> 5-10 kpc than that of DM alone. Hydrodynamical simulations that include baryons, cooling, and

  17. Comparison of Pressure Profiles of Massive Relaxed Galaxy Clusters using Sunyaev-Zel'dovich and X-ray Data

    CERN Document Server

    Bonamente, Massimiliano; Bulbul, Esra; Carlstrom, John E; Culverhouse, Thomas L; Gralla, Megan; Greer, Christopher; Hawkins, David; Hennessy, Ryan; Joy, Marshall; Kolodziejczak, Jeffery; Lamb, James W; Landry, David; Leitch, Erik M; Marrone, Daniel P; Miller, Amber; Mroczkowski, Tony; Muchovej, Stephen; Plagge, Thomas; Pryke, Clem; Sharp, Matthew; Woody, David

    2011-01-01

    We present Sunyaev-Zel'dovich (SZ) effect observations of a sample of 25 massive relaxed galaxy clusters observed with the Sunyaev-Zel'dovich Array (SZA), an 8-element interferometer that is part of the Combined Array for Research in Millimeter-wave Astronomy (CARMA). We perform an analysis of new SZA data and archival Chandra observations of this sample to investigate the integrated pressure -- a proxy for cluster mass -- determined from X-ray and SZ observations, two independent probes of the intra-cluster medium. This analysis makes use of a model for the intra-cluster medium introduced by Bulbul (2010) which can be applied simultaneously to SZ and X-ray data. With this model, we estimate the pressure profile for each cluster using a joint analysis of the SZ and X-ray data, and using the SZ data alone. We find that the integrated pressures measured from X-ray and SZ data are consistent. This conclusion is in agreement with recent results obtained using WMAP and Planck data, confirming that SZ and X-ray obs...

  18. Metal enrichment of the intra-cluster medium over a Hubble time for merging and relaxed galaxy clusters

    CERN Document Server

    Kapferer, W; Weratschnig, J; Schindler, S; Domainko, W; Van Kampen, E; Kimeswenger, S; Mair, M; Ruffert, M

    2007-01-01

    We investigate the efficiency of galactic mass loss, triggered by ram-pressure stripping and galactic winds of cluster galaxies, on the chemical enrichment of the intra-cluster medium (ICM). We combine N-body and hydrodynamic simulations with a semi-numerical galaxy formation model. By including simultaneously different enrichment processes, namely ram-pressure stripping and galactic winds, in galaxy-cluster simulations, we are able to reproduce the observed metal distribution in the ICM. We find that the mass loss by galactic winds in the redshift regime z>2 is ~10% to 20% of the total galactic wind mass loss, whereas the mass loss by ram-pressure stripping in the same epoch is up to 5% of the total ram-pressure stripping mass loss over the whole simulation time. In the cluster formation epochs z<2 ram-pressure stripping becomes more dominant than galactic winds. We discuss the non-correlation between the evolution of the mean metallicity of galaxy clusters and the galactic mass losses. For comparison wit...

  19. MACSJ1423.8+2404: Gravitational Lensing by a Massive, Relaxed Cluster of Galaxies at z=0.54

    CERN Document Server

    Limousin, M; Ma, C -J; Swinbank, A M; Smith, G P; Richard, J; Edge, A C; Jauzac, M; Kneib, J -P; Marshall, P; Schrabback, T; Smail, I R

    2009-01-01

    We present results of a gravitational-lensing and optical study of MACS ,J1423.8+2404 (z=0.545, MACS, J1423). Our analysis uses high-resolution images taken with the Hubble Space Telescope in the F555W and F814W passbands, ground based imaging in eight optical and near-infrared filters obtained with Subaru and CFHT, as well as extensive spectroscopic data gathered with the Keck telescopes. At optical wavelengths the cluster exhibits no sign of substructure and is dominated by a cD galaxy that is 2.1 magnitudes (K-band) brighter than the second brightest cluster member, suggesting that MACS, J1423 is close to be fully virialized. Analysis of the redshift distribution of 140 cluster members reveals a Gaussian distribution, mildly disturbed by the presence of a loose galaxy group that may be falling into the cluster along the line of sight. Combining strong-lensing constraints from two spectroscopically confirmed multiple-image systems near the cluster core with a weak-lensing measurement of the gravitational sh...

  20. Largest College Endowments, 2011

    Science.gov (United States)

    Chronicle of Higher Education, 2012

    2012-01-01

    Of all endowments valued at more than $250-million, the UCLA Foundation had the highest rate of growth over the previous year, at 49 percent. This article presents a table of the largest college endowments in 2011. The table covers the "rank," "institution," "market value as of June 30, 2011," and "1-year change" of institutions participating in…

  1. The SAMI Galaxy Survey: first 1000 galaxies

    CERN Document Server

    Allen, J T

    2014-01-01

    The Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey is an ongoing project to obtain integral field spectroscopic observations of ~3400 galaxies by mid-2016. Including the pilot survey, a total of ~1000 galaxies have been observed to date, making the SAMI Galaxy Survey the largest of its kind in existence. This unique dataset allows a wide range of investigations into different aspects of galaxy evolution. The first public data from the SAMI Galaxy Survey, consisting of 107 galaxies drawn from the full sample, has now been released. By giving early access to SAMI data for the entire research community, we aim to stimulate research across a broad range of topics in galaxy evolution. As the sample continues to grow, the survey will open up a new and unique parameter space for galaxy evolution studies.

  2. The largest fossil rodent

    Science.gov (United States)

    Rinderknecht, Andrés; Blanco, R. Ernesto

    2008-01-01

    The discovery of an exceptionally well-preserved skull permits the description of the new South American fossil species of the rodent, Josephoartigasia monesi sp. nov. (family: Dinomyidae; Rodentia: Hystricognathi: Caviomorpha). This species with estimated body mass of nearly 1000 kg is the largest yet recorded. The skull sheds new light on the anatomy of the extinct giant rodents of the Dinomyidae, which are known mostly from isolated teeth and incomplete mandible remains. The fossil derives from San José Formation, Uruguay, usually assigned to the Pliocene–Pleistocene (4–2 Myr ago), and the proposed palaeoenvironment where this rodent lived was characterized as an estuarine or deltaic system with forest communities. PMID:18198140

  3. An over-massive black hole in the compact lenticular galaxy NGC 1277.

    Science.gov (United States)

    van den Bosch, Remco C E; Gebhardt, Karl; Gültekin, Kayhan; van de Ven, Glenn; van der Wel, Arjen; Walsh, Jonelle L

    2012-11-29

    Most massive galaxies have supermassive black holes at their centres, and the masses of the black holes are believed to correlate with properties of the host-galaxy bulge component. Several explanations have been proposed for the existence of these locally established empirical relationships, including the non-causal, statistical process of galaxy-galaxy merging, direct feedback between the black hole and its host galaxy, and galaxy-galaxy merging and the subsequent violent relaxation and dissipation. The empirical scaling relations are therefore important for distinguishing between various theoretical models of galaxy evolution, and they furthermore form the basis for all black-hole mass measurements at large distances. Observations have shown that the mass of the black hole is typically 0.1 per cent of the mass of the stellar bulge of the galaxy. Until now, the galaxy with the largest known fraction of its mass in its central black hole (11 per cent) was the small galaxy NGC 4486B. Here we report observations of the stellar kinematics of NGC 1277, which is a compact, lenticular galaxy with a mass of 1.2 × 10(11) solar masses. From the data, we determine that the mass of the central black hole is 1.7 × 10(10) solar masses, or 59 per cent of its bulge mass. We also show observations of five other compact galaxies that have properties similar to NGC 1277 and therefore may also contain over-massive black holes. It is not yet known if these galaxies represent a tail of a distribution, or if disk-dominated galaxies fail to follow the usual black-hole mass scaling relations.

  4. An Over-Massive Black Hole in the Compact Lenticular Galaxy NGC1277

    CERN Document Server

    Bosch, Remco C E van den; Gültekin, Kayhan; van de Ven, Glenn; van der Wel, Arjen; Walsh, Jonelle L; 10.1038/nature11592

    2012-01-01

    All massive galaxies likely have supermassive black holes at their centers, and the masses of the black holes are known to correlate with properties of the host galaxy bulge component. Several explanations have been proposed for the existence of these locally-established empirical relationships; they include the non-causal, statistical process of galaxy-galaxy merging, direct feedback between the black hole and its host galaxy, or galaxy-galaxy merging and the subsequent violent relaxation and dissipation. The empirical scaling relations are thus important for distinguishing between various theoretical models of galaxy evolution, and they further form the basis for all black hole mass measurements at large distances. In particular, observations have shown that the mass of the black hole is typically 0.1% of the stellar bulge mass of the galaxy. The small galaxy NGC4486B currently has the largest published fraction of its mass in a black hole at 11%. Here we report observations of the stellar kinematics of NGC...

  5. WeirdestGalaxies: Outlier Detection Algorithm on Galaxy Spectra

    Science.gov (United States)

    Baron, Dalya; Poznanski, Dovi

    2017-05-01

    WeirdestGalaxies finds the weirdest galaxies in the Sloan Digital Sky Survey (SDSS) by using a basic outlier detection algorithm. It uses an unsupervised Random Forest (RF) algorithm to assign a similarity measure (or distance) between every pair of galaxy spectra in the SDSS. It then uses the distance matrix to find the galaxies that have the largest distance, on average, from the rest of the galaxies in the sample, and defined them as outliers.

  6. Statistical mechanics of violent relaxation

    Science.gov (United States)

    Spergel, David N.; Hernquist, Lars

    1992-01-01

    We propose a functional that is extremized through violent relaxation. It is based on the Ansatz that the wave-particle scattering during violent dynamical processes can be approximated as a sequence of discrete scattering events that occur near a particle's perigalacticon. This functional has an extremum whose structure closely resembles that of spheroidal stellar systems such as elliptical galaxies. The results described here, therefore, provide a simple framework for understanding the physical nature of violent relaxation and support the view that galaxies are structured in accord with fundamental statistical principles.

  7. Tracing cosmic evolution with clusters of galaxies

    CERN Document Server

    Voit, G M

    2004-01-01

    The most successful cosmological models to date envision structure formation as a hierarchical process in which gravity is constantly drawing lumps of matter together to form increasingly larger structures. Clusters of galaxies currently sit atop this hierarchy as the largest objects that have had time to collapse under the influence of their own gravity. Thus, their appearance on the cosmic scene is also relatively recent. Two features of clusters make them uniquely useful tracers of cosmic evolution. First, clusters are the biggest things whose masses we can reliably measure because they are the largest objects to have undergone gravitational relaxation and entered into virial equilibrium. Mass measurements of nearby clusters can therefore be used to determine the amount of structure in the universe on scales of 10^14 to 10^15 solar masses, and comparisons of the present-day cluster mass distribution with the mass distribution at earlier times can be used to measure the rate of structure formation, placing ...

  8. Fossil Group Origins VII. Galaxy substructures in fossil systems

    CERN Document Server

    Zarattini, S; Aguerri, J A L; Boschin, W; Barrena, R; del Burgo, C; Castro-Rodriguez, N; Corsini, E M; D'Onghia, E; Kundert, A; Méndez-Abreu, J; Sánchez-Janssen, R

    2016-01-01

    Fossil groups are expected to be the final product of galaxy merging within galaxy groups. In simulations, they are predicted to assemble their mass at high redshift. This early formation allows for the innermost $M^\\ast$ galaxies to merge into a massive central galaxy. Then, they are expected to maintain their fossil status because of the few interactions with the large-scale structure. In this context, the magnitude gap between the two brightest galaxies of the system is considered a good indicator of its dynamical status. As a consequence, the systems with the largest gaps should be dynamically relaxed. In order to examine the dynamical status of these systems, we systematically analyze, for the first time, the presence of galaxy substructures in a sample of 12 spectroscopically-confirmed fossil systems with redshift $z \\le 0.25$. We apply a number of tests in order to investigate the substructure in fossil systems in the two-dimensional space of projected positions out to $R_{200}$. Moreover, for a subsam...

  9. Galaxy Collisions, Gas Stripping and Star Formation in the Evolution of Galaxies

    CERN Document Server

    Palous, J

    2004-01-01

    A review of gravitational and hydrodynamical processes during formation of clusters and evolution of galaxies is given. Early, at the advent of N-body computer simulations, the importance of tidal fields in galaxy encounters has been recognized. Orbits are crowded due to tides along spiral arms, where the star formation is enhanced. Low relative velocity encounters lead to galaxy mergers. The central dominating galaxies in future clusters form before the clusters in a merging process in galaxy groups. Galaxy clusters are composed in a hierarchical scenario due to relaxation processes between galaxies and galaxy groups. As soon as the overall cluster gravitational potential is built, high speed galaxy versus galaxy encounters start to play a role. These harassment events gradually thicken and shorten spiral galaxy disks leading to the formation of S0 galaxies and ellipticals. Another aspect of the high speed motion in the hot and diluted Intracluster Medium (ICM) is the ram pressure exerted on the Interstellar...

  10. Largest particle detector nearing completion

    CERN Multimedia

    2006-01-01

    "Construction of another part of the Large Hadron Collider (LHC), the worl's largest particle accelerator at CERN in Switzerland, is nearing completion. The Compact Muon Solenoid (CMS) is oner of the LHC project's four large particle detectors. (1/2 page)

  11. Largest US plant gets larger

    Energy Technology Data Exchange (ETDEWEB)

    Fiscor, S.

    2000-04-01

    CONSOL Energy's Bailey complex consists of two extremely large underground mining operations, the Bailey and Enlow Fork mines, and the largest US preparation plant, the Bailey central plant. The original plant was designed with a raw feed capacity of 900 tph and was expanded to a total capacity of 2,200 tph. The recent upgrade, referred to as No. 1B, was completed in early 1999. Two new silos were added and raw feed conveyors were upgraded. The article gives details on the recent upgrade. 2 photos.

  12. Amazing Andromeda Galaxy

    Science.gov (United States)

    2006-01-01

    The many 'personalities' of our great galactic neighbor, the Andromeda galaxy, are exposed in this new composite image from NASA's Galaxy Evolution Explorer and the Spitzer Space Telescope. The wide, ultraviolet eyes of Galaxy Evolution Explorer reveal Andromeda's 'fiery' nature -- hotter regions brimming with young and old stars. In contrast, Spitzer's super-sensitive infrared eyes show Andromeda's relatively 'cool' side, which includes embryonic stars hidden in their dusty cocoons. Galaxy Evolution Explorer detected young, hot, high-mass stars, which are represented in blue, while populations of relatively older stars are shown as green dots. The bright yellow spot at the galaxy's center depicts a particularly dense population of old stars. Swaths of red in the galaxy's disk indicate areas where Spitzer found cool, dusty regions where stars are forming. These stars are still shrouded by the cosmic clouds of dust and gas that collapsed to form them. Together, Galaxy Evolution Explorer and Spitzer complete the picture of Andromeda's swirling spiral arms. Hints of pinkish purple depict regions where the galaxy's populations of hot, high-mass stars and cooler, dust-enshrouded stars co-exist. Located 2.5 million light-years away, the Andromeda is our largest nearby galactic neighbor. The galaxy's entire disk spans about 260,000 light-years, which means that a light beam would take 260,000 years to travel from one end of the galaxy to the other. By comparison, our Milky Way galaxy's disk is about 100,000 light-years across. This image is a false color composite comprised of data from Galaxy Evolution Explorer's far-ultraviolet detector (blue), near-ultraviolet detector (green), and Spitzer's multiband imaging photometer at 24 microns (red).

  13. Radio properties of fossil galaxy groups

    Science.gov (United States)

    Miraghaei, H.; Khosroshahi, H. G.

    2016-09-01

    We study 1.4 GHz radio properties of a sample of fossil galaxy groups using GMRT radio observations and the FIRST survey catalog. Fossil galaxy groups, having no recent major mergers in their dominant galaxies and also group scale mergers, give us the opportunity to investigate the effect of galaxy merger on AGN activity. In this work, we compare the radio properties of a rich sample of fossil groups with a sample of normal galaxy groups and clusters and show that the brightest group galaxies in fossil groups are under luminous at 1.4 GHz, relative to the general population of the brightest group galaxies, indicating that the dynamically relaxed nature of fossil groups has influenced the AGN activity in their dominant galaxy.

  14. Natural relaxation

    Science.gov (United States)

    Marzola, Luca; Raidal, Martti

    2016-11-01

    Motivated by natural inflation, we propose a relaxation mechanism consistent with inflationary cosmology that explains the hierarchy between the electroweak scale and Planck scale. This scenario is based on a selection mechanism that identifies the low-scale dynamics as the one that is screened from UV physics. The scenario also predicts the near-criticality and metastability of the Standard Model (SM) vacuum state, explaining the Higgs boson mass observed at the Large Hadron Collider (LHC). Once Majorana right-handed neutrinos are introduced to provide a viable reheating channel, our framework yields a corresponding mass scale that allows for the seesaw mechanism as well as for standard thermal leptogenesis. We argue that considering singlet scalar dark matter extensions of the proposed scenario could solve the vacuum stability problem and discuss how the cosmological constant problem is possibly addressed.

  15. Magnetic Resonance Fingerprinting with short relaxation intervals.

    Science.gov (United States)

    Amthor, Thomas; Doneva, Mariya; Koken, Peter; Sommer, Karsten; Meineke, Jakob; Börnert, Peter

    2017-09-01

    The aim of this study was to investigate a technique for improving the performance of Magnetic Resonance Fingerprinting (MRF) in repetitive sampling schemes, in particular for 3D MRF acquisition, by shortening relaxation intervals between MRF pulse train repetitions. A calculation method for MRF dictionaries adapted to short relaxation intervals and non-relaxed initial spin states is presented, based on the concept of stationary fingerprints. The method is applicable to many different k-space sampling schemes in 2D and 3D. For accuracy analysis, T1 and T2 values of a phantom are determined by single-slice Cartesian MRF for different relaxation intervals and are compared with quantitative reference measurements. The relevance of slice profile effects is also investigated in this case. To further illustrate the capabilities of the method, an application to in-vivo spiral 3D MRF measurements is demonstrated. The proposed computation method enables accurate parameter estimation even for the shortest relaxation intervals, as investigated for different sampling patterns in 2D and 3D. In 2D Cartesian measurements, we achieved a scan acceleration of more than a factor of two, while maintaining acceptable accuracy: The largest T1 values of a sample set deviated from their reference values by 0.3% (longest relaxation interval) and 2.4% (shortest relaxation interval). The largest T2 values showed systematic deviations of up to 10% for all relaxation intervals, which is discussed. The influence of slice profile effects for multislice acquisition is shown to become increasingly relevant for short relaxation intervals. In 3D spiral measurements, a scan time reduction of 36% was achieved, maintaining the quality of in-vivo T1 and T2 maps. Reducing the relaxation interval between MRF sequence repetitions using stationary fingerprint dictionaries is a feasible method to improve the scan efficiency of MRF sequences. The method enables fast implementations of 3D spatially resolved

  16. Galaxy Zoo: Mergers - Dynamical Models of Interacting Galaxies

    CERN Document Server

    Holincheck, Anthony J; Borne, Kirk; Fortson, Lucy; Lintott, Chris; Smith, Arfon M; Bamford, Steven; Keel, William C; Parrish, Michael

    2016-01-01

    The dynamical history of most merging galaxies is not well understood. Correlations between galaxy interaction and star formation have been found in previous studies, but require the context of the physical history of merging systems for full insight into the processes that lead to enhanced star formation. We present the results of simulations that reconstruct the orbit trajectories and disturbed morphologies of pairs of interacting galaxies. With the use of a restricted three-body simulation code and the help of Citizen Scientists, we sample 10^5 points in parameter space for each system. We demonstrate a successful recreation of the morphologies of 62 pairs of interacting galaxies through the review of more than 3 million simulations. We examine the level of convergence and uniqueness of the dynamical properties of each system. These simulations represent the largest collection of models of interacting galaxies to date, providing a valuable resource for the investigation of mergers. This paper presents the ...

  17. LARGEST EIGENVALUE OF A UNICYCLIC MIXED GRAPH

    Institute of Scientific and Technical Information of China (English)

    FanYizheng

    2004-01-01

    The graphs which maximize and minimize respectively the largest eigenvalue over all unicyclic mixed graphs U on n vertices are determined. The unicyclic mixed graphs U with the largest eigenvalue λ1 (U)=n or λ1 (U)∈ (n ,n+1] are characterized.

  18. Growing Galaxies Gently

    Science.gov (United States)

    2010-10-01

    New observations from ESO's Very Large Telescope have, for the first time, provided direct evidence that young galaxies can grow by sucking in the cool gas around them and using it as fuel for the formation of many new stars. In the first few billion years after the Big Bang the mass of a typical galaxy increased dramatically and understanding why this happened is one of the hottest problems in modern astrophysics. The results appear in the 14 October issue of the journal Nature. The first galaxies formed well before the Universe was one billion years old and were much smaller than the giant systems - including the Milky Way - that we see today. So somehow the average galaxy size has increased as the Universe has evolved. Galaxies often collide and then merge to form larger systems and this process is certainly an important growth mechanism. However, an additional, gentler way has been proposed. A European team of astronomers has used ESO's Very Large Telescope to test this very different idea - that young galaxies can also grow by sucking in cool streams of the hydrogen and helium gas that filled the early Universe and forming new stars from this primitive material. Just as a commercial company can expand either by merging with other companies, or by hiring more staff, young galaxies could perhaps also grow in two different ways - by merging with other galaxies or by accreting material. The team leader, Giovanni Cresci (Osservatorio Astrofisico di Arcetri) says: "The new results from the VLT are the first direct evidence that the accretion of pristine gas really happened and was enough to fuel vigorous star formation and the growth of massive galaxies in the young Universe." The discovery will have a major impact on our understanding of the evolution of the Universe from the Big Bang to the present day. Theories of galaxy formation and evolution may have to be re-written. The group began by selecting three very distant galaxies to see if they could find evidence

  19. Semi analytical description of formation of galaxies and clusters of galaxies

    OpenAIRE

    Demiański, Marek; Doroshkevich, Andrey

    2013-01-01

    We apply the well known semi analytical model of formation of DM halos to discuss the process of formation and evolution of the relaxed objects dominated by the DM component (such as the first and dSph galaxies and clusters of galaxies). On the one hand this approach allows us to obtain a simple description of evolution of the first galaxies. On the other hand it reveals links between the observed characteristics of the relaxed DM halos and the initial power spectrum of density perturbations....

  20. broken magnet highlights largest collider's engineering challenges

    CERN Document Server

    Inman, Mason

    2007-01-01

    "Even at the world's soon-to-be largest particle accelerator - a device that promises to push the boundaries of physics - scientists need to be mindful of one of the most fundamental laws in the universe: Murphy's Law. (2 pages)

  1. The largest table in Chinese restaurant processes

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In this paper,we investigate the expectation of the size of the largest table in an(α,θ)-Chinese restaurant process by using and developing an idea originated in the work by Shepp,which discusses random permutation.

  2. On Finding the Largest Mean Among Many

    OpenAIRE

    Jamieson, Kevin; Malloy, Matthew; Nowak, Robert; Bubeck, Sebastien

    2013-01-01

    Sampling from distributions to find the one with the largest mean arises in a broad range of applications, and it can be mathematically modeled as a multi-armed bandit problem in which each distribution is associated with an arm. This paper studies the sample complexity of identifying the best arm (largest mean) in a multi-armed bandit problem. Motivated by large-scale applications, we are especially interested in identifying situations where the total number of samples that are necessary and...

  3. Bayesian Predictive Distribution for the Magnitude of the Largest Aftershock

    Science.gov (United States)

    Shcherbakov, R.

    2014-12-01

    Aftershock sequences, which follow large earthquakes, last hundreds of days and are characterized by well defined frequency-magnitude and spatio-temporal distributions. The largest aftershocks in a sequence constitute significant hazard and can inflict additional damage to infrastructure. Therefore, the estimation of the magnitude of possible largest aftershocks in a sequence is of high importance. In this work, we propose a statistical model based on Bayesian analysis and extreme value statistics to describe the distribution of magnitudes of the largest aftershocks in a sequence. We derive an analytical expression for a Bayesian predictive distribution function for the magnitude of the largest expected aftershock and compute the corresponding confidence intervals. We assume that the occurrence of aftershocks can be modeled, to a good approximation, by a non-homogeneous Poisson process with a temporal event rate given by the modified Omori law. We also assume that the frequency-magnitude statistics of aftershocks can be approximated by Gutenberg-Richter scaling. We apply our analysis to 19 prominent aftershock sequences, which occurred in the last 30 years, in order to compute the Bayesian predictive distributions and the corresponding confidence intervals. In the analysis, we use the information of the early aftershocks in the sequences (in the first 1, 10, and 30 days after the main shock) to estimate retrospectively the confidence intervals for the magnitude of the expected largest aftershocks. We demonstrate by analysing 19 past sequences that in many cases we are able to constrain the magnitudes of the largest aftershocks. For example, this includes the analysis of the Darfield (Christchurch) aftershock sequence. The proposed analysis can be used for the earthquake hazard assessment and forecasting associated with the occurrence of large aftershocks. The improvement in instrumental data associated with early aftershocks can greatly enhance the analysis and

  4. Two-Body Relaxation in Cosmological Simulations

    CERN Document Server

    Binney, J; Binney, James; Knebe, Alexander

    2002-01-01

    The importance of two-body relaxation in cosmological simulations is explored with simulations in which there are two species of particles. The cases of mass ratio sqrt(2):1 and 4:1 are investigated. Simulations are run with both a fixed softening length and adaptive softening using the publicly available codes GADGET and MLAPM, respectively. The effects of two-body relaxation are detected in both the density profiles of halos and the mass function of halos. The effects are more pronounced with a fixed softening length, but even in this case they are not so large as to suggest that results obtained with one mass species are significantly affected by two-body relaxation. The simulations that use adaptive softening are slightly less affected by two-body relaxation and produce slightly higher central densities in the largest halos. They run about three times faster than the simulations that use a fixed softening length.

  5. Semi analytical description of formation of galaxies and clusters of galaxies

    CERN Document Server

    Demiański, Marek

    2013-01-01

    We apply the well known semi analytical model of formation of DM halos to discuss the process of formation and evolution of the relaxed objects dominated by the DM component (such as the first and dSph galaxies and clusters of galaxies). On the one hand this approach allows us to obtain a simple description of evolution of the first galaxies. On the other hand it reveals links between the observed characteristics of the relaxed DM halos and the initial power spectrum of density perturbations. Results of our analysis of the observed properties of 41 DM dominated dSph galaxies and data of $\\sim 300$ clusters of galaxies are consistent with the $\\Lambda$CDM like power spectrum of initial perturbations down to the scale of $\\sim 10kpc$.

  6. Semi-analytical description of formation of galaxies and clusters of galaxies

    Science.gov (United States)

    Demiański, M.; Doroshkevich, A. G.

    2014-03-01

    We apply the well-known semi-analytical model of formation of the Dark Matter (DM) haloes to discuss properties of the relaxed objects dominated by the DM component (such as the first and dwarf spheroidal galaxies (dSph) and/or clusters of galaxies). This approach allows us to obtain a simple but more detailed description of evolution of the first galaxies. It also reveals links between the observed characteristics of the relaxed DM haloes and the initial power spectrum of density perturbations. Results of our analysis of the observed properties of ˜40 DM dominated galaxies and ˜100 clusters of galaxies are consistent with the Λ cold dark matter like power spectrum of initial perturbations down to the scale of ˜10 kpc. For the DM dominated objects the scaling relations are also discussed.

  7. Percolation technique for galaxy clustering

    Science.gov (United States)

    Klypin, Anatoly; Shandarin, Sergei F.

    1993-01-01

    We study percolation in mass and galaxy distributions obtained in 3D simulations of the CDM, C + HDM, and the power law (n = -1) models in the Omega = 1 universe. Percolation statistics is used here as a quantitative measure of the degree to which a mass or galaxy distribution is of a filamentary or cellular type. The very fast code used calculates the statistics of clusters along with the direct detection of percolation. We found that the two parameters mu(infinity), characterizing the size of the largest cluster, and mu-squared, characterizing the weighted mean size of all clusters excluding the largest one, are extremely useful for evaluating the percolation threshold. An advantage of using these parameters is their low sensitivity to boundary effects. We show that both the CDM and the C + HDM models are extremely filamentary both in mass and galaxy distribution. The percolation thresholds for the mass distributions are determined.

  8. Relaxation Techniques for Health

    Science.gov (United States)

    ... R S T U V W X Y Z Relaxation Techniques for Health Share: On This Page What’s the ... Bottom Line? How much do we know about relaxation techniques? A substantial amount of research has been done ...

  9. Latent Period of Relaxation.

    Science.gov (United States)

    Kobayashi, M; Irisawa, H

    1961-10-27

    The latent period of relaxation of molluscan myocardium due to anodal current is much longer than that of contraction. Although the rate and the grade of relaxation are intimately related to both the stimulus condition and the muscle tension, the latent period of relaxation remains constant, except when the temperature of the bathing fluid is changed.

  10. Galaxy Formation

    DEFF Research Database (Denmark)

    Sparre, Martin

    Galaxy formation is an enormously complex discipline due to the many physical processes that play a role in shaping galaxies. The objective of this thesis is to study galaxy formation with two different approaches: First, numerical simulations are used to study the structure of dark matter and how...... galaxies form stars throughout the history of the Universe, and secondly it is shown that observations of gamma-ray bursts (GRBs) can be used to probe galaxies with active star formation in the early Universe. A conclusion from the hydrodynamical simulations is that the galaxies from the stateof......-the-art cosmological simulation, Illustris, follow a tight relation between star formation rate and stellar mass. This relation agrees well with the observed relation at a redshift of z = 0 and z = 4, but at intermediate redshifts of z ' 2 the normalisation is lower than in real observations. This is highlighted...

  11. Largest sparse subgraphs of random graphs

    NARCIS (Netherlands)

    Fountoulakis, N.; Kang, R.J.; McDiarmid, C.J.H.; Nešetřil, J.; Győri, E.; Sali, A.

    2011-01-01

    For the Erd\\H{o}s-R\\'enyi random graph $G_{n,p}$, we consider the order of a largest vertex subset that induces a subgraph with average degree at most $t$. For the case when both $p$ and $t$ are fixed, this value is asymptotically almost surely concentrated on at most two explicitly given points. Th

  12. CERN tests largest superconducting solenoid magnet

    CERN Multimedia

    2006-01-01

    "CERN's Compacts Muon Solenoid (CMS) - the world's largest superconducting solenoid magnet - has reached full field in testing. The instrument is part of the proton-proton Large Hadron Collider (LHC) project, located in a giant subterranean chamber at Cessy on the Franco-Swiss border." (1 page)

  13. Spin alignment of dark matter haloes in the shells of the largest voids

    CERN Document Server

    Cuesta, A J; Gottlöber, S; Patiri, S G; Yepes, G; Prada, F

    2007-01-01

    Using the high resolution cosmological N-body simulation MareNostrum Universe we study the orientation of shape and angular momentum of galaxy-size dark matter haloes around large voids. We find that haloes located on the shells of the largest cosmic voids have angular momenta that tend to be preferentially perpendicular to the direction that joins the centre of the halo and the centre of the void. This alignment has been found in spiral galaxies around voids using galaxy redshift surveys. We measure for the first time the strength of this alignment, showing how it falls off with increasing distance to the centre of the void. We also confirm the correlation between the intensity of this alignment and the halo mass. The analysis of the orientation of the halo main axes confirms the results of previous works. Moreover, we find a similar alignment for the baryonic matter inside dark matter haloes, which is much stronger in their inner parts.

  14. Local Group galaxies emerge from the dark

    CERN Document Server

    Sawala, Till; Fattahi, Azadeh; Navarro, Julio F; Bower, Richard G; Crain, Robert A; Vecchia, Claudio Dalla; Furlong, Michelle; Helly, John C; Jenkins, Adrian; Oman, Kyle A; Schaller, Matthieu; Schaye, Joop; Theuns, Tom; Trayford, James; White, Simon D M

    2014-01-01

    The "Lambda Cold Dark Matter" (LCDM) model of cosmic structure formation is eminently falsifiable: once its parameters are fixed on large scales, it becomes testable in the nearby Universe. Observations within our Local Group of galaxies, including the satellite populations of the Milky Way and Andromeda, appear to contradict LCDM predictions: there are far fewer satellite galaxies than dark matter halos (the "missing satellites" problem), galaxies seem to avoid the largest substructures (the "too big to fail" problem), and the brightest satellites appear to orbit their host galaxies on a thin plane (the "planes of satellites" problem). We present results from the first hydrodynamic simulations of the Local Group that match the observed abundance of galaxies. We find that when baryonic and dark matter are followed simultaneously in the context of a realistic galaxy formation model, all three "problems" are resolved within the LCDM paradigm.

  15. Disrupted Stars in Unusual Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2016-03-01

    Tidal disruption events (TDEs) occur when a star passes a little too close to a supermassive black hole at the center of a galaxy. Tidal forces from the black hole cause the passing star to be torn apart, resulting in a brief flare of radiation as the stars material accretes onto the black hole. A recent study asks the following question: do TDEs occur most frequently in an unusual type of galaxy?A Trend in DisruptionsSo far, we have data from eight candidate TDEs that peaked in optical and ultraviolet wavelengths. The spectra from these observations have shown an intriguing trend: many of these TDEs host galaxies exhibit weak line emission (indicating little or no current star-formation activity), and yet they show strong Balmer absorption lines (indicating star formation activity occurred within the last Gyr). These quiescent, Balmer-strong galaxies likely underwent a period of intense star formation that recently ended.To determine if TDEs are overrepresented in such galaxies, a team of scientists led by Decker French (Steward Observatory, University of Arizona) has quantified the fraction of galaxies in the Sloan Digital Sky Survey (SDSS) that exhibit similar properties to those of TDE hosts.Quantifying OverrepresentationSpectral characteristics of SDSS galaxies (gray) and TDE candidate host galaxies (colored points): line emission vs. Balmer absorption. The lower right-hand box identifies thequiescent, Balmer-strong galaxies which contain most TDE events, yet are uncommon among the galaxy sample as a whole. Click for a better look! [French et al. 2016]French and collaborators compare the optical spectra of the TDE host galaxies to those of nearly 600,000 SDSS galaxies, using two different cutoffs for the Balmer absorption the indicator of past star formation. Their strictest cut, filtering for very high Balmer absorption, selected only 0.2% of the SDSS galaxies, yet 38% of the TDEs are hosted in such galaxies. Using a more relaxed cutoff selects 2.3% of

  16. The World's Largest Steel Casting Poured Successfully

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ The world's largest steel casting -- the upper beam (or the top head) for free forging oil hydraulic press with a 18,000-ton force capacity, was poured successfully by CITIC Heavy Machinery Co., Ltd. (CITICHM) on May 22, 2008. This head piece is 11.95 meters long, 3.8 meters wide, 4.59 meters high and about 520 tons in gross weight. Pouring is the most important and critical step during its manufacturing process. The production of this huge casting requires about 830 tons of refined molten steel from 10 smelting furnaces and pouring with six ladles into the mold cavity at one time, which made it currently the world's largest steel casting poured and the most one-time molten steel organized.

  17. Galaxy Disks

    NARCIS (Netherlands)

    van der Kruit, P. C.; Freeman, K. C.

    The disks of disk galaxies contain a substantial fraction of their baryonic matter and angular momentum, and much of the evolutionary activity in these galaxies, such as the formation of stars, spiral arms, bars and rings, and the various forms of secular evolution, takes place in their disks. The

  18. The world's largest time projection chamber

    CERN Multimedia

    Maximilien Brice

    2006-01-01

    Peter Glassel, the technical coordinator for the ALICE time projection chamber, is seen sitting inside the detector; the largest in the world at nearly 100 cubic metres. Thousands of wires are connected to read out electronic data produced as particles are created in lead-lead collisions at the centre of the detector. These particles will cause the medium within the time projection chamber to ionise along their tracks allowing the particle paths to be recreated.

  19. World's largest sapphire for many applications

    Science.gov (United States)

    Khattak, Chandra P.; Shetty, Raj; Schwerdtfeger, C. Richard; Ullal, Saurabh

    2016-10-01

    Sapphire has been used for many high technology applications because of its excellent optical, mechanical, high temperature, abrasion resistance and dielectric properties. However, it is expensive and the volume of sapphire used has been limited. The potential sapphire requirements for LED and consumer electronic applications are very high. Emphasis has been on producing larger sapphire boules to achieve significant cost reductions so these applications are realized. World's largest sapphire boules, 500 mm diameter 300+kg, have been grown to address these markets.

  20. Ningxia Becomes China's Largest Coal Chemical Base

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Northwest China's Ningxia Hui Autonomous Region plans to invest more than 100 billion yuan (US$12.9 billion) to build Asia's largest liquefied-coal base,according to the regional development and reform commission. The first group of projects, designed to produce methanol and other chemicals from coal, are under construction in the Ningdong Chemical Resource Base, which is located near coal deposits containing 80 percent of Ningxia's known coal reserves, said Hao Linhai, director of the regional commission.

  1. Galaxy formation

    CERN Document Server

    Silk, Joseph; Dvorkin, Irina

    2015-01-01

    Galaxy formation is at the forefront of observation and theory in cosmology. An improved understanding is essential for improving our knowledge both of the cosmological parameters, of the contents of the universe, and of our origins. In these lectures intended for graduate students, galaxy formation theory is reviewed and confronted with recent observational issues. In Lecture 1, the following topics are presented: star formation considerations, including IMF, star formation efficiency and star formation rate, the origin of the galaxy luminosity function, and feedback in dwarf galaxies. In Lecture 2, we describe formation of disks and massive spheroids, including the growth of supermassive black holes, negative feedback in spheroids, the AGN-star formation connection, star formation rates at high redshift and the baryon fraction in galaxies.

  2. Galaxy Formation

    DEFF Research Database (Denmark)

    Sparre, Martin

    galaxies form stars throughout the history of the Universe, and secondly it is shown that observations of gamma-ray bursts (GRBs) can be used to probe galaxies with active star formation in the early Universe. A conclusion from the hydrodynamical simulations is that the galaxies from the stateof......-the-art cosmological simulation, Illustris, follow a tight relation between star formation rate and stellar mass. This relation agrees well with the observed relation at a redshift of z = 0 and z = 4, but at intermediate redshifts of z ' 2 the normalisation is lower than in real observations. This is highlighted...... of GRB host galaxies is affected by the fact that GRBs appear mainly to happen in low-metallicity galaxies. Solving this problem will make it possible to derive the total cosmic star formation rate more reliably from number counts of GRBs....

  3. Lopsided Collections of Satellite Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2016-12-01

    satellites are located at an angle of degrees from the direction pointing toward the other galaxy in the pair. There are more satellites found in the space between the pair than predicted by a uniform distribution. [Libeskind et al. 2016]What might cause this asymmetric distribution? The authors suggest the primary cause is that galaxies in pairs are not necessarily relaxed halos in equilibrium a case in which spherical symmetry would apply. Instead, these are likely merging, dynamically active pairs of galaxies, so we cannot assume that they have axially symmetric halos.Simulations of Local-Group-like pairs of galaxies will be the next step needed to understand how such asymmetries in the distribution of satellites form and evolve. Meanwhile, the results presented here suggest that the commonly adopted axially symmetric models of the Milky Way (and other galaxies in pairs) should be used with caution, as they may not be capturing the true shape of the halo.CitationNoam I. Libeskind et al 2016 ApJ 830 121. doi:10.3847/0004-637X/830/2/121

  4. Les galaxies

    Science.gov (United States)

    Combes, Francoise

    2016-08-01

    Considerable progress has been made on galaxy formation and evolution in recent years, and new issues. The old Hubble classification according to the tuning fork of spirals, lenticulars and ellipticals, is still useful but has given place to the red sequence, the blue cloud and the green valley, showing a real bimodality of types between star forming galaxies (blue) and quenched ones (red). Large surveys have shown that stellar mass and environment density are the two main factors of the evolution from blue to red sequences. Evolution is followed directly with redshift through a look-back time of more than 12 billion years. The most distant galaxy at z=11. has already a stellar mass of a billion suns. In an apparent anti-hierarchical scenario, the most massive galaxies form stars early on, while essentially dwarf galaxies are actively star-formers now. This downsizing feature also applies to the growth of super-massive black holes at the heart of each bulgy galaxy. The feedback from active nuclei is essential to explain the distribution of mass in galaxies, and in particular to explain why the fraction of baryonic matter is so low, lower by more than a factor 5 than the baryonic fraction of the Universe. New instruments just entering in operation, like MUSE and ALMA, provide a new and rich data flow, which is developed in this series of articles.

  5. Early Science Results from SOFIA, the World's Largest Airborne Observatory

    CERN Document Server

    De Buizer, James M

    2013-01-01

    The Stratospheric Observatory For Infrared Astronomy, or SOFIA, is the largest flying observatory ever built,consisting of a 2.7-meter diameter telescope embedded in a modified Boeing 747-SP aircraft. SOFIA is a joint project between NASA and the German Aerospace Center Deutsches Zentrum fur Luft und-Raumfahrt (DLR). By flying at altitudes up to 45000 feet, the observatory gets above 99.9 percent of the infrared-absorbing water vapor in the Earth's atmosphere. This opens up an almost uninterrupted wavelength range from 0.3-1600 microns that is in large part obscured from ground based observatories. Since its 'Initial Science Flight' in December 2010, SOFIA has flown several dozen science flights, and has observed a wide array of objects from Solar System bodies, to stellar nurseries, to distant galaxies. This paper reviews a few of the exciting new science results from these first flights which were made by three instruments: the mid-infrared camera FORCAST, the far-infrared heterodyne spectrometer GREAT, and...

  6. Fiji's largest marine reserve benefits reef sharks

    Science.gov (United States)

    Goetze, J. S.; Fullwood, L. A. F.

    2013-03-01

    To provide more information about whether sharks benefit from no-take marine reserves, we quantified the relative abundance and biomass of reef sharks inside and outside of Namena, Fiji's largest reserve (60.6 km2). Using stereo baited remote underwater video systems (stereo-BRUVs), we found that the abundance and biomass of sharks was approximately two and four times greater in shallow and deep locations, respectively, within the Namena reserve compared to adjacent fished areas. The greater abundance and biomass of reef sharks inside Namena is likely a result of greater prey availability rather than protection from fishing. This study demonstrates that marine reserves can benefit sharks.

  7. Molecular Gas in the Halo Fuels the Growth of a Massive Cluster Galaxy at High Redshift

    CERN Document Server

    Emonts, B H C; Villar-Martin, M; Norris, R P; Ekers, R D; van Moorsel, G A; Dannerbauer, H; Pentericci, L; Miley, G K; Allison, J R; Sadler, E M; Guillard, P; Carilli, C L; Mao, M Y; Rottgering, H J A; De Breuck, C; Seymour, N; Gullberg, B; Ceverino, D; Jagannathan, P; Vernet, J; Indermuehle, B T

    2016-01-01

    The largest galaxies in the Universe reside in galaxy clusters. Using sensitive observations of carbon-monoxide, we show that the Spiderweb Galaxy -a massive galaxy in a distant protocluster- is forming from a large reservoir of molecular gas. Most of this molecular gas lies between the protocluster galaxies and has low velocity dispersion, indicating that it is part of an enriched inter-galactic medium. This may constitute the reservoir of gas that fuels the widespread star formation seen in earlier ultraviolet observations of the Spiderweb Galaxy. Our results support the notion that giant galaxies in clusters formed from extended regions of recycled gas at high redshift.

  8. Extremal hexagonal chains concerning largest eigenvalue

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Lianzhu

    2001-01-01

    [1]Kristian, J. , Sandage, A. R. , Westphal, J., The extension of the Hubble diagram: Ⅱ. New redshifts and photometry of very distant galaxy clusters, Astrophys. J., 1978, 221: 383.[2]Sandage, A., The redshift-distant relation V. Galaxy co lors as functions of galactic latitude and redshift, Astrophys, J.,1973, 183: 711.[3]Qu, Q. Y., Qin, Z. H., Han, C. S. et al., A relation between magnitudes and redshifts of QSOs with strong interplanetary scientillation, Chinese Astron., 1979, 4: 97.[4]Tinsley, B. M. , The Galaxy counts, color-redshift relation, and related quantities as probes of cosmology and galactic evolu-tion, Astrophys. J., 1977, 211: 621.[5]Spinrad, H., Djorgovski, S., The status of the Hubble diagram in 1986 (eds. Hewitt, A. Burbidge, G. Fang, L. Z. ),Proc. IAU Symp 124 on Observational Cosmology, New York: D. Reidel Publishing Company, 1986, 129.[6]Fang, L. Z., Zhou, Y. Y., Cheng F. Z. et al., Evolution of quasars with resolved components and determination of decel-eration parameter q0, Scientia Sinica, 1979, 22: 1292.[7]Cheng, K. S., Fan, J. H., Li, Y. et al., Do γ-ray burst associated with metal-rich quasars (ed. Cheng, K. S., Singh,H. P.), Proc. of The Pacific Rim Conference on Stellar Astrophysics, August 13-16, 1997, Houg Kong, 1997.[8]Davis, M., Geller, M. J., Huchra, J., The local mean mass density of the universe: new methods for studying galaxy clus-tering, Astrophys. J., 1978, 221: 1.[9]Gott, J. R., Turner, E. L., The mean luminosity and mass densities in the universe, Astrophys. J., 1976, 209: 1.[10]Shapiro, S. L., The density of matter in the form of galaxies, Astron. J., 1971, 76: 291.[11]Fang, L. Z., Hu, F. X., The large-scale inhomogeneities in the universe (eds. Yang, J., Zhu, C. S. ), Proceeding of A-cademia Sinica--Max-Plank Socity Workshop on High Energy Astrophyics Held in Nanjing, China, April 9-17, 1982,New York: Gordon and Breach Science Publishers S.A. 1982, 425[12]Baldwin, J. A

  9. Star formation properties of galaxy cluster A1767

    CERN Document Server

    Yan, Peng-Fei; Yuan, Qi-Rong

    2015-01-01

    Abell 1767 is a dynamically relaxed, cD cluster of galaxies with a redshift of 0.0703. Among 250 spectroscopically confirmed member galaxies within a projected radius of 2.5r_{200}, 243 galaxies (~ 97%) are spectroscopically covered by the Sloan Digital Sky Survey (SDSS). Based on this homogeneous spectral sample, the stellar evolutionary synthesis code, STARLIGHT, is applied to investigate the stellar populations and star formation histories (SFHs) of cluster galaxies. The star formation properties of galaxies, such as mean stellar ages, metallicities, stellar masses, and star formation rates (SFRs), are presented as the functions of local galaxy density. Strong environmental effect is found in the manner that massive galaxies in the high-density core region of cluster tend to have higher metallicities, longer mean stellar ages, and lower specific star formation rates (SSFRs), and their recent star formation activities have been remarkably suppressed. In addition, the correlations of the metallicity and SSFR...

  10. Galaxy Formation

    CERN Document Server

    Longair, Malcolm S

    2008-01-01

    This second edition of Galaxy Formation is an up-to-date text on astrophysical cosmology, expounding the structure of the classical cosmological models from a contemporary viewpoint. This forms the background to a detailed study of the origin of structure and galaxies in the Universe. The derivations of many of the most important results are derived by simple physical arguments which illuminate the results of more advanced treatments. A very wide range of observational data is brought to bear upon these problems, including the most recent results from WMAP, the Hubble Space Telescope, galaxy surveys like the Sloan Digital Sky Survey and the 2dF Galaxy Redshift Survey, studies of Type 1a supernovae, and many other observations.

  11. Segregation effects according to the evolutionary stage of galaxy groups

    Science.gov (United States)

    Ribeiro, A. L. B.; Lopes, P. A. A.; Trevisan, M.

    2010-11-01

    We study segregation phenomena in 57 groups selected from the 2dF Percolation-Inferred Galaxy Groups (2PIGG) catalogue of galaxy groups. The sample corresponds to those systems located in areas of at least 80 per cent redshift coverage out to 10 times the radius of the groups. The dynamical state of the galaxy systems was determined after studying their velocity distributions. We have used the Anderson-Darling test to distinguish relaxed and non-relaxed systems. This analysis indicates that 84 per cent of groups have galaxy velocities consistent with the normal distribution, while 16 per cent of them have more complex underlying distributions. Properties of the member galaxies are investigated taking into account this classification. Our results indicate that galaxies in Gaussian groups are significantly more evolved than galaxies in non-relaxed systems out to distances of ~4R200, presenting significantly redder (B - R) colours. We also find evidence that galaxies with MR <= -21.5 in Gaussian groups are closer to the condition of energy equipartition.

  12. New Galaxies with UV Excess. VI

    Science.gov (United States)

    Kazarian, M. A.; Petrosian, G. V.

    2005-07-01

    A list is presented of 122 new galaxies with UV excess observed on plates obtained using the 40″ Schmidt telescope at the Byurakan Observatory with a 1°.5 objective prism. It is shown that the relative number of galaxies with a strong UV excess (classes 1 and 2) listed in Table 1 is roughly 55.7%. This is 6.7% higher than for the previously observed galaxies. These samples also differ in terms of the morphology of the spectra. The largest deviation, approximately 9.9%, occurs for type “sd.”

  13. Giant radio galaxies and cosmic web

    Science.gov (United States)

    Heinämäki, Pekka

    2016-10-01

    Giant radio galaxies create the welldistinguishable class of sources.These sources are characterized with edge-brightened radio lobes withhighly collimated radio jets and large linear sizes which make themthe largest individual structures in the Universe. They are also knownto be hosted by elliptical/disturbed host galaxies and avoid clustersand high galaxy density regions. Because of GRG, large linear sizeslobes extend well beyond the interstellar media and host galaxyhalo the evolution of the radio lobes may depend on interactionwith this environment. Using our method to extract filamentarystructure of the galaxies in our local universe we study whetherradio lobe properties in some giant radio galaxies are determinedon an interaction of this filament ambient.

  14. Xinjiang to Build Its Largest Copper Mine

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>On September 16, the 6,000,000-ton mining project of Hudehe Copper Mine kicked off, which is the largest copper mine in Xinjiang.Jointly developed by Xinjiang Nonferrous Metals Group and Gansu Jianxin Group, Hudehe Copper Mine is located at Tuoli County, Tacheng Prefecture, Xinjiang. It is a large-scale porphyry-type copper deposit with proven copper reserve of 362,500 tons and prospective reserve of 1,000,000 tons(metal content). According to the preliminary plan, it will be built into a mine with mining and dressing capacity of 6,000,000 tons/year. With a total investment of RMB 1.466 billion, the project is expected to achieve annual sales revenue of RMB 0.8 billion and provide jobs for nearly 1,000 people.

  15. The connection between mass and light in galaxy clusters

    NARCIS (Netherlands)

    Sifón, Andalaft C.J.

    2016-01-01

    Galaxy clusters are the largest reservoirs of matter in the Universe, and as such are unique laboratories to understand the connection between dark and luminous, 'normal' matter. We use several techniques and galaxy cluster samples to study this connection from various angles. In particular, we try

  16. Galaxy Zoo: Mergers - Dynamical models of interacting galaxies

    Science.gov (United States)

    Holincheck, Anthony J.; Wallin, John F.; Borne, Kirk; Fortson, Lucy; Lintott, Chris; Smith, Arfon M.; Bamford, Steven; Keel, William C.; Parrish, Michael

    2016-06-01

    The dynamical history of most merging galaxies is not well understood. Correlations between galaxy interaction and star formation have been found in previous studies, but require the context of the physical history of merging systems for full insight into the processes that lead to enhanced star formation. We present the results of simulations that reconstruct the orbit trajectories and disturbed morphologies of pairs of interacting galaxies. With the use of a restricted three-body simulation code and the help of citizen scientists, we sample 105 points in parameter space for each system. We demonstrate a successful recreation of the morphologies of 62 pairs of interacting galaxies through the review of more than 3 million simulations. We examine the level of convergence and uniqueness of the dynamical properties of each system. These simulations represent the largest collection of models of interacting galaxies to date, providing a valuable resource for the investigation of mergers. This paper presents the simulation parameters generated by the project. They are now publicly available in electronic format at http://data.galaxyzoo.org/mergers.html. Though our best-fitting model parameters are not an exact match to previously published models, our method for determining uncertainty measurements will aid future comparisons between models. The dynamical clocks from our models agree with previous results of the time since the onset of star formation from starburst models in interacting systems and suggest that tidally induced star formation is triggered very soon after closest approach.

  17. Mapping the Cosmic Web with the largest all-sky surveys

    Science.gov (United States)

    Bilicki, Maciej; Peacock, John A.; Jarrett, Thomas H.; Cluver, Michelle E.; Steward, Louise

    2016-10-01

    Our view of the low-redshift Cosmic Web has been revolutionized by galaxy redshift surveys such as 6dFGS, SDSS and 2MRS. However, the trade-off between depth and angular coverage limits a systematic three-dimensional account of the entire sky beyond the Local Volume (z sphere, one must draw on multiwavelength datasets and state-of-the-art photometric redshift techniques. We have undertaken a dedicated program of cross-matching the largest photometric all-sky surveys - 2MASS, WISE and SuperCOSMOS - to obtain accurate redshift estimates of millions of galaxies. The first outcome of these efforts - the 2MASS Photometric Redshift catalog (2MPZ, Bilicki et al. 2014a) - has been publicly released and includes almost 1 million galaxies with a mean redshift of z=0.08. Here we summarize how this catalog was constructed and how using the WISE mid-infrared sample together with SuperCOSMOS optical data allows us to push to redshift shells of z~ 0.2 -0.3 on unprecedented angular scales. Our catalogs, with ~ 20 million sources in total, provide access to cosmological volumes crucial for studies of local galaxy flows (clustering dipole, bulk flow) and cross-correlations with the cosmic microwave background such as the integrated Sachs-Wolfe effect or lensing studies.

  18. Indentation load relaxation test

    Energy Technology Data Exchange (ETDEWEB)

    Hannula, S.P.; Stone, D.; Li, C.Y. (Cornell Univ., Ithaca, NY (USA))

    Most of the models that are used to describe the nonelastic behavior of materials utilize stress-strain rate relations which can be obtained by a load relaxation test. The conventional load relaxation test, however, cannot be performed if the volume of the material to be tested is very small. For such applications the indentation type of test offers an attractive means of obtaining data necessary for materials characterization. In this work the feasibility of the indentation load relaxation test is studied. Experimental techniques are described together with results on Al, Cu and 316 SS. These results are compared to those of conventional uniaxial load relaxation tests, and the conversion of the load-indentation rate data into the stress-strain rate data is discussed.

  19. Relaxation techniques for stress

    Science.gov (United States)

    ... problems such as high blood pressure, stomachaches, headaches, anxiety, and depression. Using relaxation techniques can help you feel calm. These exercises can also help you manage stress and ease the effects of stress on your body.

  20. Largest clinic in the world? (Bogota).

    Science.gov (United States)

    1971-01-01

    The IPPF member, the Asociacion Pro-Bienestar de la Familia Colombiana (Profamilia), is discussed and its clinic, the Pilot Center in Bogota, reputed to be the largest family clinic in the world, is described. From January 1966 until the end of 1970, the Pilot Center served 59,469 new acceptors. Of the 31 Profamilia clinics in Colombia, the Pilot Center was visited by 22% of all new acceptors during 1970. Profamilia established the first vasectomy clinic in Latin America in February 1970. By the end of 1970, 92 vasectomies had been performed. Profamilia has expanded its family planning program, and part of this expansion is a result of Profamilia's extensive use of mass media in its education campaign. In 1970, there was a 24% increase in new acceptors over 1969 and a 66% increase in follow-up visits. 62,292 radio spots and 7 television programs were broadcast and announcements about family planning were shown in public cinemas in the latter half of 1970. Nearly 300,000 women attended talks, meetings, and film shows on family planning, and approximately 2 million leaflets and information sheets were distributed. To increase community involvement, Profamilia held 26 short courses for various groups including religious and community leaders. Profamilia also conducted a training course for doctors and sociologists from Colombia and other Latin American countries.

  1. Perturbations and quantum relaxation

    CERN Document Server

    Kandhadai, Adithya

    2016-01-01

    We investigate whether small perturbations can cause relaxation to quantum equilibrium over very long timescales. We consider in particular a two-dimensional harmonic oscillator, which can serve as a model of a field mode on expanding space. We assume an initial wave function with small perturbations to the ground state. We present evidence that the trajectories are highly confined so as to preclude relaxation to equilibrium even over very long timescales. Cosmological implications are briefly discussed.

  2. AGN feedback in elliptical galaxies: numerical simulations

    CERN Document Server

    Ciotti, L

    2011-01-01

    The importance of feedback (radiative and mechanical) from massive black holes at the centers of elliptical galaxies is not in doubt, given the well established relation among black hole mass and galaxy optical luminosity. Here, with the aid of high-resolution hydrodynamical simulations, we discuss how this feedback affects the hot ISM of isolated elliptical galaxies of different mass. The cooling and heating functions include photoionization plus Compton heating, the radiative transport equations are solved, and the mechanical feedback due to the nuclear wind is also described on a physical basis; star formation is considered. In the medium-high mass galaxies the resulting evolution is highly unsteady. At early times major accretion episodes caused by cooling flows in the recycled gas produced by stellar evolution trigger AGN flaring: relaxation instabilities occur so that duty cycles are small enough to account for the very small fraction of massive ellipticals observed to be in the QSO-phase, when the accr...

  3. The Connection Between Galaxy Environment and the Luminosity Function Slopes of Star-Forming Regions

    CERN Document Server

    Cook, David O; Lee, Janice C; Thilker, David; Calzetti, Daniela; Kennicutt, Robert C

    2016-01-01

    We present the first study of GALEX far ultra-violet (FUV) luminosity functions of individual star-forming regions within a sample of 258 nearby galaxies spanning a large range in total stellar mass and star formation properties. We identify ~65,000 star-forming regions (i.e., FUV sources), measure each galaxy's luminosity function, and characterize the relationships between the luminosity function slope (alpha) and several global galaxy properties. A final sample of 82 galaxies with reliable luminosity functions are used to define these relationships and represent the largest sample of galaxies with the largest range of galaxy properties used to study the connection between luminosity function properties and galaxy environment. We find that alpha correlates with global star formation properties, where galaxies with higher star formation rates and star formation rate densities (Sigma_SFR) tend to have flatter luminosity function slopes. In addition, we find that neither stochastic sampling of the luminosity f...

  4. THE ZURICH ENVIRONMENTAL STUDY OF GALAXIES IN GROUPS ALONG THE COSMIC WEB. I. WHICH ENVIRONMENT AFFECTS GALAXY EVOLUTION?

    Energy Technology Data Exchange (ETDEWEB)

    Carollo, C. Marcella; Cibinel, Anna; Lilly, Simon J.; Miniati, Francesco; Cameron, Ewan; Peng, Yingjie; Pipino, Antonio; Rudick, Craig S. [Institute for Astronomy, ETH Zurich, CH-8093 Zurich (Switzerland); Norberg, Peder [Department of Physics, Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Silverman, John D. [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo, Chiba 277-8583 (Japan); Van Gorkom, Jacqueline [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Finoguenov, Alexis, E-mail: marcella@phys.ethz.ch [Max-Planck-Institut für extraterrestrische Physik, D-84571 Garching (Germany)

    2013-10-20

    The Zurich Environmental Study (ZENS) is based on a sample of ∼1500 galaxy members of 141 groups in the mass range ∼10{sup 12.5-14.5} M{sub ☉} within the narrow redshift range 0.05 < z < 0.0585. ZENS adopts novel approaches, described here, to quantify four different galactic environments, namely: (1) the mass of the host group halo; (2) the projected halo-centric distance; (3) the rank of galaxies as central or satellites within their group halos; and (4) the filamentary large-scale structure density. No self-consistent identification of a central galaxy is found in ∼40% of <10{sup 13.5} M{sub ☉} groups, from which we estimate that ∼15% of groups at these masses are dynamically unrelaxed systems. Central galaxies in relaxed and unrelaxed groups generally have similar properties, suggesting that centrals are regulated by their mass and not by their environment. Centrals in relaxed groups have, however, ∼30% larger sizes than in unrelaxed groups, possibly due to accretion of small satellites in virialized group halos. At M > 10{sup 10} M{sub ☉}, satellite galaxies in relaxed and unrelaxed groups have similar size, color, and (specific) star formation rate distributions; at lower galaxy masses, satellites are marginally redder in relaxed relative to unrelaxed groups, suggesting quenching of star formation in low-mass satellites by physical processes active in relaxed halos. Overall, relaxed and unrelaxed groups show similar stellar mass populations, likely indicating similar stellar mass conversion efficiencies. In the enclosed ZENS catalog, we publish all environmental diagnostics as well as the galaxy structural and photometric measurements described in companion ZENS papers II and III.

  5. Segregation Effects According to the Evolutionary Stage of Galaxy Groups

    CERN Document Server

    Ribeiro, Andre L B; Trevisan, Marina

    2010-01-01

    We study segregation phenomena in 57 groups selected from the 2PIGG catalog of galaxy groups. The sample corresponds to those systems located in areas of at least 80% redshift coverage out to 10 times the radius of the groups. The dynamical state of the galaxy systems was determined after studying their velocity distributions. We have used the Anderson-Darling test to distinguish relaxed and non-relaxed systems. This analysis indicates that 84% of groups have galaxy velocities consistent with the normal distribution, while 16% of them have more complex underlying distributions. Properties of the member galaxies are investigated taking into account this classification. Our results indicate that galaxies in Gaussian groups are significantly more evolved than galaxies in non-relaxed systems out to distances of about 4R200, presenting signficantly redder (B-R) color. We also find evidence that galaxies with M_R < -21.5 in Gaussian groups are closer to the condition of energy equipartition.

  6. Cluster-Void Degeneracy Breaking: Dark Energy, Planck and the Largest Cluster & Void

    CERN Document Server

    Sahlén, Martin; Silk, Joseph

    2015-01-01

    Combining galaxy cluster and void abundances breaks the degeneracy between mean matter density $\\Omega_{\\rm m}$ and power spectrum normalization $\\sigma_8$. In a first for voids, we constrain $\\Omega_{\\rm m} = 0.21 \\pm 0.10$ and $\\sigma_8 = 0.95 \\pm 0.21$ for a flat $\\Lambda$CDM universe, using extreme-value statistics on the claimed largest cluster and void. The Planck-consistent results detect dark energy with two objects, independently of other dark energy probes. Cluster-void studies also offer complementarity in scale, density, and non-linearity - of particular interest for testing modified-gravity models.

  7. XMM-Newton analysis of a newly discovered, extremely X-ray luminous galaxy cluster at high redshift

    Science.gov (United States)

    Thoelken, S.; Schrabback, T.

    2016-06-01

    Galaxy clusters, the largest virialized structures in the universe, provide an excellent method to test cosmology on large scales. The galaxy cluster mass function as a function of redshift is a key tool to determine the fundamental cosmological parameters and especially measurements at high redshifts can e.g. provide constraints on dark energy. The fgas test as a direct cosmological probe is of special importance. Therefore, relaxed galaxy clusters at high redshifts are needed but these objects are considered to be extremely rare in current structure formation models. Here we present first results from an XMM-Newton analysis of an extremely X-ray luminous, newly discovered and potentially cool core cluster at a redshift of z=0.9. We carefully account for background emission and PSF effects and model the cluster emission in three radial bins. Our preliminary results suggest that this cluster is indeed a good candidate for a cool core cluster and thus potentially of extreme value for cosmology.

  8. Evolution of galaxy groups in the Illustris simulation

    CERN Document Server

    Raouf, Mojtaba; Dariush, Ali A

    2016-01-01

    We present the first study of evolution of galaxy groups in the Illustris simulation. We focus on dynamically relaxed and unrelaxed galaxy groups representing dynamically evolved and evolving galaxy systems, respectively. The evolutionary state of a group is probed from its luminosity gap and separation between the brightest group galaxy and the center of mass of the group members. We find that the Illustris simulation, over-produces large luminosity gap galaxy systems, known as fossil systems, in comparison to observations and the probed semi-analytical predictions. However, this simulation is equally successful in recovering the correlation between luminosity gap and luminosity centroid offset, in comparison to the probed semi-analytic model. We find evolutionary tracks based on luminosity gap which indicate that a large luminosity gap group is rooted in a small luminosity gap group, regardless of the position of the brightest group galaxy within the halo. This simulation helps, for the first time, to explo...

  9. Environmental Effects on Late-Type Galaxies in Nearby Clusters

    CERN Document Server

    Boselli, A

    2006-01-01

    The transformations taking place in late-type galaxies in the environment of rich clusters of galaxies at z=0 are reviewed. From the handful of late-type galaxies that inhabit local clusters, whether they were formed in-situ and survived as such, avoiding transformation or even destruction or if they are newcomers that recently infall from outside, we can learn an important lesson on the latest stages of galaxy evolution. We start by reviewing the observational scenario, covering the broadest possible stretch of the electromagnetic spectrum, from the gas tracers, the star formation tracers, the old star tracers and the dust. Strong emphasis is given to the three nearby, well studied clusters Virgo, A1367 and Coma, representative of different evolutionary stages, from unrelaxed, spiral rich (Virgo) to relaxed, spiral poor clusters (Coma). We continue by providing a review of models of galaxy interactions relevant to clusters of galaxies. Prototypes of various mechanisms and processes are discussed and their ty...

  10. The Role of Galaxy Mergers and Molecular Gas in the Early Phase of Galaxy Cluster Assembly

    Science.gov (United States)

    Hung, Chao-Ling

    2017-08-01

    High-redshift protoclusters are ideal places to study the formation of the largest structures in the Universe and the early environmental influences on galaxy evolution. Recent discoveries of z>2 protoclusters with extremely rich populations of dusty star-forming galaxies (DSFGs; SFR>100 Msun/yr) represent the most active assembly phases of massive galaxy clusters. Understanding the triggering mechanisms of these unusual concentrations of extreme star-forming galaxies can provide critical insights into the formation of most massive galaxies in these clusters and the assembly of massive clusters themselves. For example, an increased probability of galaxy interactions and/or enhanced gas supply may trigger an excess of DSFGs. Using the extensive ancillary data in the COSMOS field, we study the role of galaxy mergers through measuring the frequency of galaxy pairs in two such DSFG-rich protoclusters at z=2.10 and 2.47, respectively. We also investigate the mean molecular gas content of protocluster galaxies by stacking SCUBA-2 850 micron images. These independent investigations provide complementary views into the physical nature of these DSFG-rich protoclusters.

  11. Relaxing the Bounds on Primordial Magnetic Seed Fields

    OpenAIRE

    1999-01-01

    We point out that the lower bound on the primordial magnetic field required to seed the galactic dynamo is significantly relaxed in an open universe or in a universe with a positive cosmological constant. It is shown that, for reasonable cosmological parameters, primordial seed fields of strength 10^{-30} Gauss or less at the time of galaxy formation could explain observed galactic magnetic fields. As a consequence, mechanisms of primordial magnetic seed-field generation that have previously ...

  12. Molecular Relaxation in Liquids

    CERN Document Server

    Bagchi, Biman

    2012-01-01

    This book brings together many different relaxation phenomena in liquids under a common umbrella and provides a unified view of apparently diverse phenomena. It aligns recent experimental results obtained with modern techniques with recent theoretical developments. Such close interaction between experiment and theory in this area goes back to the works of Einstein, Smoluchowski, Kramers' and de Gennes. Development of ultrafast laser spectroscopy recently allowed study of various relaxation processes directly in the time domain, with time scales going down to picosecond (ps) and femtosecond (fs

  13. Setting the normalcy level of HI properties in isolated galaxies

    CERN Document Server

    Espada, D; Athanassoula, E; Bosma, A; Huchtmeier, W K; Leon, S; Lisenfeld, U; Sabater, J; Sulentic, J; Verley, S; Yun, M

    2009-01-01

    Studying the atomic gas (HI) properties of the most isolated galaxies is essential to quantify the effect that the environment exerts on this sensitive component of the interstellar medium. We observed and compiled HI data for a well defined sample of ~ 800 galaxies in the Catalog of Isolated Galaxies, as part of the AMIGA project (Analysis of the ISM in Isolated GAlaxies, http://amiga.iaa.es), which enlarges considerably previous samples used to quantify the HI deficiency in galaxies located in denser environments. By studying the shape of 182 HI profiles, we revisited the usually accepted result that, independently of the environment, more than half of the galaxies present a perturbed HI disk. In isolated galaxies this would certainly be a striking result if these are supposed to be the most relaxed systems, and has implications in the relaxation time scales of HI disks and the nature of the most frequent perturbing mechanisms in galaxies. Our sample likely exhibits the lowest HI asymmetry level in the loca...

  14. Galaxy Evolution

    Science.gov (United States)

    Matteucci, F.

    We review both the observational and theoretical constraints on the evolution of the abundances of heavy elements in gas and stars in galaxies of different morphological type. The main aim of this work is to document the progress made in our understanding of the physical processes regulating the chemical evolution of galaxies during the last sixteen years since the appearance, in this same journal (volume 5, page 287), of the well know review of Beatrice Tinsley, to whom I dedicate this paper. Finally, this article is addressed particularly to readers who do not actively work on galactic chemical evolution and who might use it as a cook book where the main ingredients are discussed and useful recipes can be found.

  15. Galaxy formation.

    Science.gov (United States)

    Peebles, P J

    1998-01-01

    It is argued that within the standard Big Bang cosmological model the bulk of the mass of the luminous parts of the large galaxies likely had been assembled by redshift z approximately 10. Galaxy assembly this early would be difficult to fit in the widely discussed adiabatic cold dark matter model for structure formation, but it could agree with an isocurvature version in which the cold dark matter is the remnant of a massive scalar field frozen (or squeezed) from quantum fluctuations during inflation. The squeezed field fluctuations would be Gaussian with zero mean, and the distribution of the field mass therefore would be the square of a random Gaussian process. This offers a possibly interesting new direction for the numerical exploration of models for cosmic structure formation.

  16. Galaxy Zoo: Observing Secular Evolution Through Bars

    CERN Document Server

    Cheung, Edmond; Masters, Karen L; Nichol, Robert C; Bosma, A; Bell, Eric F; Faber, S M; Koo, David C; Lintott, Chris; Melvin, Thomas; Schawinski, Kevin; Skibba, Ramin A; Willett, Kyle W

    2013-01-01

    Observations have shown that there is a connection between the presence of a bar and the properties of a galaxy. In a parallel effort, simulations have shown that this connection is consistent with the theory of bar-driven secular evolution. But observational evidence of bar-driven secular evolution has been sparse. In this paper, we use the Galaxy Zoo 2 dataset to look for evidence of this secular evolution. Our sample consists of 13,295 disk galaxies, with an overall bar fraction of 23.6 +/- 0.4%, of which 1,154 barred galaxies also have bar length measurements. These samples are the largest ever used to study the role of bars in disk galaxy evolution. We characterize bars by the bar likelihood, the likelihood a bar is present in a given galaxy, and the bar length. These two bar properties show interesting correlations with the specific star formation rate and the inner central structure of galaxies. Comparing these observations to state-of-the-art simulations of bar evolution, which include live halos and ...

  17. Do Galaxies Follow Darwinian Evolution?

    Science.gov (United States)

    2006-12-01

    , France, who coordinates the VIMOS VLT Deep Survey team that made the discovery. "They suggest that galaxies as we see them today are the product of their inherent genetic information, evolved over time, as well as complex interactions with their environments, such as mergers." Scientists have known for several decades that galaxies in the Universe's past look different to those in the present-day Universe, local to the Milky Way [3]. Today, galaxies can be roughly classified as red, when few or no new stars are being born, or blue, where star formation is still ongoing. Moreover, a strong correlation exists between a galaxy's colour and the environment it resides in: the more sociable types found in dense clusters are more likely to be red than the more isolated ones. By looking back at a wide range of galaxies of a variety of ages, the astronomers were aiming to study how this peculiar correlation has evolved over time. "Using VIMOS, we were able to use the largest sample of galaxies currently available for this type of study, and because of the instrument's ability to study many objects at a time we obtained many more measurements than previously possible," said Angela Iovino, from the Brera Astronomical Observatory, Italy, another member of the team. The team's discovery of a marked variation in the 'colour-density' relationship, depending on whether a galaxy is found in a cluster or alone, and on its luminosity, has many potential implications. The findings suggest for example that being located in a cluster quenches a galaxy's ability to form stars more quickly compared with those in isolation. Luminous galaxies also run out of star-forming material at an earlier time than fainter ones. They conclude that the connection between galaxies' colour, luminosity and their local environment is not merely a result of primordial conditions 'imprinted' during their formation - but just as for humans, galaxies' relationship and interactions can have a profound impact on their

  18. Galaxy Disks

    CERN Document Server

    van der Kruit, P C

    2011-01-01

    The formation and evolution of galactic disks is particularly important for understanding how galaxies form and evolve, and the cause of the variety in which they appear to us. Ongoing large surveys, made possible by new instrumentation at wavelengths from the ultraviolet (GALEX), via optical (HST and large groundbased telescopes) and infrared (Spitzer) to the radio are providing much new information about disk galaxies over a wide range of redshift. Although progress has been made, the dynamics and structure of stellar disks, including their truncations, are still not well understood. We do now have plausible estimates of disk mass-to-light ratios, and estimates of Toomre's $Q$ parameter show that they are just locally stable. Disks are mostly very flat and sometimes very thin, and have a range in surface brightness from canonical disks with a central surface brightness of about 21.5 $B$-mag arcsec$^{-2}$ down to very low surface brightnesses. It appears that galaxy disks are not maximal, except possibly in ...

  19. "Galaxy," Defined

    CERN Document Server

    Willman, Beth

    2012-01-01

    A growing number of low luminosity and low surface brightness astronomical objects challenge traditional notions of both galaxies and star clusters. To address this challenge, we propose a definition of galaxy that does not depend on a cold dark matter model of the universe: A galaxy is a gravitationally bound collection of stars whose properties cannot be explained by a combination of baryons and Newton's laws of gravity. We use this definition to critically examine the classification of ultra-faint dwarfs, globular clusters, ultra-compact dwarfs, and tidal dwarfs. While kinematic studies provide an effective diagnostic of the definition in many regimes, they can be less useful for compact or very faint systems. To explore the utility of using the [Fe/H] spread as a diagnostic, we use published spectroscopic [Fe/H] measurements of 16 Milky Way dwarfs and 24 globular clusters to uniformly calculate their [Fe/H] spreads and associated uncertainties. Our principal results are: (i) no known, old star cluster wit...

  20. Dwarf spheroidal galaxies keystones of galaxy evolution

    CERN Document Server

    Gallagher, S C; Gallagher, S; Wyse, F G

    1994-01-01

    Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and giant galaxies. The putative dark matter content of these low-surface-brightness systems is of particular interest, as is their chemical evolution. Surveys for new dwarf spheroidals hidden behind the stars of our Galaxy and those which are not bound to giant galaxies may give new clues as to the origins of this unique class of galaxy.

  1. Mapping the Cosmic Web with the largest all-sky surveys

    CERN Document Server

    Bilicki, Maciej; Jarrett, Thomas H; Cluver, Michelle E; Steward, Louise

    2014-01-01

    Our view of the low-redshift Cosmic Web has been revolutionized by galaxy redshift surveys such as 6dFGS, SDSS and 2MRS. However, the trade-off between depth and angular coverage limits a systematic three-dimensional account of the entire sky beyond the Local Volume (z<0.05). In order to reliably map the Universe to cosmologically significant depths over the full celestial sphere, one must draw on multiwavelength datasets and state-of-the-art photometric redshift techniques. We have undertaken a dedicated program of cross-matching the largest photometric all-sky surveys -- 2MASS, WISE and SuperCOSMOS -- to obtain accurate redshift estimates of millions of galaxies. The first outcome of these efforts -- the 2MASS Photometric Redshift catalog (2MPZ, Bilicki et al. 2014a) -- has been publicly released and includes almost 1 million galaxies with a mean redshift of z=0.08. Here we summarize how this catalog was constructed and how using the WISE mid-infrared sample together with SuperCOSMOS optical data allows ...

  2. Kinematic classification of non-interacting spiral galaxies

    CERN Document Server

    Wiegert, Theresa

    2013-01-01

    Using neutral hydrogen (HI) rotation curves of 79 galaxies, culled from the literature, as well as measured from HI data, we present a method for classifying disk galaxies by their kinematics. In order to investigate fundamental kinematic properties we concentrate on non-interacting spiral galaxies. We employ a simple parameterized form for the rotation curve in order to derive the three parameters: the maximum rotational velocity, the turnover radius and a measure of the slope of the rotation curve beyond the turnover radius. Our approach uses the statistical Hierarchical Clustering method to guide our division of the resultant 3D distribution of galaxies into five classes. Comparing the kinematic classes in this preliminary classification scheme to a number of galaxy properties we find that our class containing galaxies with the largest rotational velocities has a mean morphological type of Sb/Sbc while the other classes tend to later types. Other trends also generally agree with those described by previous...

  3. New Fast Lane towards Discoveries of Clusters of Galaxies Inaugurated

    Science.gov (United States)

    2003-07-01

    Space and Ground-Based Telescopes Cooperate to Gain Deep Cosmological Insights Summary Using the ESA XMM-Newton satellite, a team of European and Chilean astronomers [2] has obtained the world's deepest "wide-field" X-ray image of the cosmos to date. This penetrating view, when complemented with observations by some of the largest and most efficient ground-based optical telescopes, including the ESO Very Large Telescope (VLT), has resulted in the discovery of several large clusters of galaxies. These early results from an ambitious research programme are extremely promising and pave the way for a very comprehensive and thorough census of clusters of galaxies at various epochs. Relying on the foremost astronomical technology and with an unequalled observational efficiency, this project is set to provide new insights into the structure and evolution of the distant Universe. PR Photo 19a/03: First image from the XMM-LSS survey. PR Photo 19b/03: Zoom-in on PR Photo 19b/03. PR Photo 19c/03: XMM-Newton contour map of the probable extent of a cluster of galaxies, superimposed upon a CHFT I-band image. PR Photo 19d/03: Velocity distribution in the cluster field shown in PR Photo 19c/03. The universal web Unlike grains of sand on a beach, matter is not uniformly spread throughout the Universe. Instead, it is concentrated into galaxies which themselves congregate into clusters (and even clusters of clusters). These clusters are "strung" throughout the Universe in a web-like structure, cf. ESO PR 11/01. Our Galaxy, the Milky Way, for example, belongs to the so-called Local Group which also comprises "Messier 31", the Andromeda Galaxy. The Local Group contains about 30 galaxies and measures a few million light-years across. Other clusters are much larger. The Coma cluster contains thousands of galaxies and measures more than 20 million light-years. Another well known example is the Virgo cluster, covering no less than 10 degrees on the sky ! Clusters of galaxies are the most

  4. Galaxy Zoo: morphological classifications for 120 000 galaxies in HST legacy imaging

    Science.gov (United States)

    Willett, Kyle W.; Galloway, Melanie A.; Bamford, Steven P.; Lintott, Chris J.; Masters, Karen L.; Scarlata, Claudia; Simmons, B. D.; Beck, Melanie; Cardamone, Carolin N.; Cheung, Edmond; Edmondson, Edward M.; Fortson, Lucy F.; Griffith, Roger L.; Häußler, Boris; Han, Anna; Hart, Ross; Melvin, Thomas; Parrish, Michael; Schawinski, Kevin; Smethurst, R. J.; Smith, Arfon M.

    2017-02-01

    We present the data release paper for the Galaxy Zoo: Hubble (GZH) project. This is the third phase in a large effort to measure reliable, detailed morphologies of galaxies by using crowdsourced visual classifications of colour-composite images. Images in GZH were selected from various publicly released Hubble Space Telescope legacy programmes conducted with the Advanced Camera for Surveys, with filters that probe the rest-frame optical emission from galaxies out to z ˜ 1. The bulk of the sample is selected to have mI814W = 0.9 ± 0.6, with a tail extending out to z ≃ 4. The GZH morphological data include measurements of both bulge- and disc-dominated galaxies, details on spiral disc structure that relate to the Hubble type, bar identification, and numerous measurements of clump identification and geometry. This paper also describes a new method for calibrating morphologies for galaxies of different luminosities and at different redshifts by using artificially redshifted galaxy images as a baseline. The GZH catalogue contains both raw and calibrated morphological vote fractions for 119 849 galaxies, providing the largest data set to date suitable for large-scale studies of galaxy evolution out to z ˜ 1.

  5. Hair Dye and Hair Relaxers

    Science.gov (United States)

    ... For Consumers Consumer Information by Audience For Women Hair Dye and Hair Relaxers Share Tweet Linkedin Pin it More sharing ... products. If you have a bad reaction to hair dyes and relaxers, you should: Stop using the ...

  6. Galaxies Collide to Create Hot, Huge Galaxy

    Science.gov (United States)

    2009-01-01

    This image of a pair of colliding galaxies called NGC 6240 shows them in a rare, short-lived phase of their evolution just before they merge into a single, larger galaxy. The prolonged, violent collision has drastically altered the appearance of both galaxies and created huge amounts of heat turning NGC 6240 into an 'infrared luminous' active galaxy. A rich variety of active galaxies, with different shapes, luminosities and radiation profiles exist. These galaxies may be related astronomers have suspected that they may represent an evolutionary sequence. By catching different galaxies in different stages of merging, a story emerges as one type of active galaxy changes into another. NGC 6240 provides an important 'missing link' in this process. This image was created from combined data from the infrared array camera of NASA's Spitzer Space Telescope at 3.6 and 8.0 microns (red) and visible light from NASA's Hubble Space Telescope (green and blue).

  7. The Galaxy End Sequence

    Science.gov (United States)

    Eales, Stephen; de Vis, Pieter; Smith, Matthew W. L.; Appah, Kiran; Ciesla, Laure; Duffield, Chris; Schofield, Simon

    2017-03-01

    A common assumption is that galaxies fall in two distinct regions of a plot of specific star formation rate (SSFR) versus galaxy stellar mass: a star-forming galaxy main sequence (GMS) and a separate region of 'passive' or 'red and dead galaxies'. Starting from a volume-limited sample of nearby galaxies designed to contain most of the stellar mass in this volume, and thus representing the end-point of ≃12 billion years of galaxy evolution, we investigate the distribution of galaxies in this diagram today. We show that galaxies follow a strongly curved extended GMS with a steep negative slope at high galaxy stellar masses. There is a gradual change in the morphologies of the galaxies along this distribution, but there is no clear break between early-type and late-type galaxies. Examining the other evidence that there are two distinct populations, we argue that the 'red sequence' is the result of the colours of galaxies changing very little below a critical value of the SSFR, rather than implying a distinct population of galaxies. Herschel observations, which show at least half of early-type galaxies contain a cool interstellar medium, also imply continuity between early-type and late-type galaxies. This picture of a unitary population of galaxies requires more gradual evolutionary processes than the rapid quenching process needed to explain two distinct populations. We challenge theorists to predict quantitatively the properties of this 'Galaxy End Sequence'.

  8. ALMA Partners Break Ground on World's Largest Millimeter Wavelength Telescope

    Science.gov (United States)

    2003-11-01

    Scientists and dignitaries from North America, Europe, and Chile broke ground today (Thursday, November 6, 2003) on what will be the world's largest, most sensitive radio telescope operating at millimeter wavelengths. ALMA - the Atacama Large Millimeter Array - will be a single instrument composed of 64 high-precision antennas located on the Chajnantor plain of the Chilean Andes in the District of San Pedro de Atacama, 16,500 feet (5,000 meters) above sea level. ALMA's primary function will be to observe and image with unprecedented clarity the enigmatic cold regions of the Universe, which are optically dark, yet shine brightly in the millimeter portion of the electromagnetic spectrum. ALMA Array Artist's Conception of ALMA Array in Compact Configuration (Click on Image for Larger Version) Other Images Available: Artist's conception of the antennas for the Atacama Large Millimeter Array Moonrise over ALMA test equipment near Cerro Chajnantor, Chile VertexRSI antenna at the VLA test site The Atacama Large Millimeter Array is an international astronomy facility. ALMA is an equal partnership between Europe and North America, in cooperation with the Republic of Chile, and is funded in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC), and in Europe by the European Southern Observatory (ESO) and Spain. ALMA construction and operations are led on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI), and on behalf of Europe by ESO. "The U.S. National Science Foundation joins today with our North American partner, Canada, and with the European Southern Observatory, Spain, and Chile to prepare for a spectacular new instrument," said Dr. Rita Colwell, director of the U.S. National Science Foundation. "The Atacama Large Millimeter Array will expand our vision of the Universe with "eyes" that pierce the shrouded mantles of

  9. Kinetic Actviation Relaxation Technique

    CERN Document Server

    Béland, Laurent Karim; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand

    2011-01-01

    We present a detailed description of the kinetic Activation-Relaxation Technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si, self-interstitial diffusion in Fe and structural relaxation in amorphous silicon.

  10. Nonlinear fractional relaxation

    Indian Academy of Sciences (India)

    A Tofighi

    2012-04-01

    We define a nonlinear model for fractional relaxation phenomena. We use -expansion method to analyse this model. By studying the fundamental solutions of this model we find that when → 0 the model exhibits a fast decay rate and when → ∞ the model exhibits a power-law decay. By analysing the frequency response we find a logarithmic enhancement for the relative ratio of susceptibility.

  11. The HIPASS Catalogue: III - Optical Counterparts & Isolated Dark Galaxies

    CERN Document Server

    Doyle, M T; Rohde, D J; Pimbblet, K A; Read, M; Meyer, M J; Zwaan, M A; Ryan-Weber, E; Stevens, J; Koribalski, B S; Webster, R L; Staveley-Smith, L; Barnes, D G; Howlett, M; Kilborn, V A; Waugh, M; Pierce, M J; Bhathal, R; De Blok, W J G; Disney, M J; Ekers, R D; Freeman, K C; García, D A; Gibson, B K; Harnett, J I; Henning, P A; Jerjen, H; Kesteven, M J; Knezek, P M; Mader, S; Marquarding, M; Minchin, R F; O'Brien, J; Oosterloo, T; Price, R M; Putman, M E; Ryder, S D; Sadler, E M; Stewart, I M; Stootman, F; Wright, A E; Doyle, Marianne T.

    2005-01-01

    We present the largest catalogue to date of optical counterparts for HI radio-selected galaxies, Hopcat. Of the 4315 HI radio-detected sources from the HI Parkes All Sky Survey (Hipass) catalogue, we find optical counterparts for 3618 (84%) galaxies. Of these, 1798 (42%) have confirmed optical velocities and 848 (20%) are single matches without confirmed velocities. Some galaxy matches are members of galaxy groups. From these multiple galaxy matches, 714 (16%) have confirmed optical velocities and a further 258 (6%) galaxies are without confirmed velocities. For 481 (11%), multiple galaxies are present but no single optical counterpart can be chosen and 216 (5%) have no obvious optical galaxy present. Most of these 'blank fields' are in crowded fields along the Galactic plane or have high extinctions. Isolated 'Dark galaxy' candidates are investigated using an extinction cut of ABj < 1 mag and the blank fields category. Of the 3692 galaxies with an ABj extinction < 1 mag, only 13 are also blank fields. ...

  12. Evolution of collisionless systems of gravitating masses, and the formation of galaxies and galaxy clusters

    Energy Technology Data Exchange (ETDEWEB)

    Doroshkevich, A.G.; Klypin, A.A.

    1981-03-01

    A series of dissipation-free models are investigated for the formation of structure in elliptical galaxies or rich clusters of galaxies by the rapid relaxation process. Using the method of macroparticles, the evolution of two types of systems comprising approx.10/sup 4/ particles is computed numerically: a) a system of superposed homogeneous oblate ellipsoids differing widely in mass and initial density; b) successive accretion of a set of low-density envelopes. In all cases an extended, flattened power-law surface-density profile develops, in good agreement with the profiles observed. The relationship between the parameters of the initial and final distributions is discussed.

  13. The Moment Convergence Rates for Largest Eigenvalues of β Ensembles

    Institute of Scientific and Technical Information of China (English)

    Jun Shan XIE

    2013-01-01

    The paper focuses on the largest eigenvalues of the β-Hermite ensemble and theβ-Laguerre ensemble.In particular,we obtain the precise moment convergence rates of their largest eigenvalues.The results are motivated by the complete convergence for partial sums of i.i.d.random variables,and the proofs depend on the small deviations for largest eigenvalues of the β ensembles and tail inequalities of the general β Tracy-Widom law.

  14. Luminosity Function of the Cluster of Galaxies Abell 566

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We investigate the Luminosity Function (LF) of the cluster of galaxies Abell 566. The photometric data of 15 intermediate-bands are obtained from the Beijing- Arizona-Taiwan-Connecticut (BATC) photometric sky survey. For each of the 15 wavebands, the LF of cluster galaxies is well modelled by the Schechter function, with characteristic luminosities from -18.0 to -21.9 magnitude, from the a- to the p-band. Morphological dependence of the LF is investigated by separating the cluster members into 'red' and 'blue' subsamples. It is clear that late type galaxies have a steeper shape of LF than the early type galaxies. We also divided the sample galaxies by their local environment. It was found that galaxies in the sparser region have steeper shape of LF than galaxies in the denser region. Combining the results of morphological and environmental dependence of LFs, we show that Abell 566 is a well relaxed cluster with positive evidence of galaxy interaction and merger, and excess number of bright early type galaxies located in its denser region.

  15. An Overview of the Dwarf Galaxy Survey

    CERN Document Server

    Madden, S C; Galametz, M; Cormier, D; Lebouteiller, V; Galliano, F; Hony, S; Bendo, G J; Smith, M W L; Pohlen, M; Roussel, H; Sauvage, M; Wu, R; Sturm, E; Poglitsch, A; Contursi, A; Doublier, V; Baes, M; Barlow, M J; Boselli, A; Boquien, M; Carlson, L R; Ciesla, L; Cooray, A; Cortese, L; De Looze, I; Irwin, J A; Isaak, K; Kamenetzky, J; Karczewski, O L; Lu, N; MacHattie, J A; Halloran, B O; Parkin, T J; Rangwala, N; Schirm, M R P; Schulz, B; Spinoglio, L; Vaccari, M; Wilson, C D; Wozniak, H

    2013-01-01

    The Dwarf Galaxy Survey (DGS) program is studying low-metallicity galaxies using 230h of far-infrared (FIR) and submillimetre (submm) photometric and spectroscopic observations of the Herschel Space Observatory and draws to this a rich database of a wide range of wavelengths tracing the dust, gas and stars. This sample of 50 galaxies includes the largest metallicity range achievable in the local Universe including the lowest metallicity (Z) galaxies, 1/50 Zsun, and spans 4 orders of magnitude in star formation rates. The survey is designed to get a handle on the physics of the interstellar medium (ISM) of low metallicity dwarf galaxies, especially on their dust and gas properties and the ISM heating and cooling processes. The DGS produces PACS and SPIRE maps of low-metallicity galaxies observed at 70, 100, 160, 250, 350, and 500 mic with the highest sensitivity achievable to date in the FIR and submm. The FIR fine-structure lines, [CII] 158 mic, [OI] 63 mic, [OI] 145 mic, [OIII] 88 mic, [NIII] 57 mic and [NII...

  16. Early assembly of the most massive galaxies

    CERN Document Server

    Collins, Chris A; Hilton, Matt; Kay, Scott T; Stanford, S Adam; Davidson, Michael; Hosmer, Mark; Hoyle, Ben; Liddle, Andrew; Lloyd-Davies, Ed; Mann, Robert G; Mehrtens, Nicola; Miller, Christopher J; Nichol, Robert C; Romer, A Kathy; Sahlen, Martin; Viana, Pedro T P; West, Michael J

    2009-01-01

    The current consensus is that galaxies begin as small density fluctuations in the early Universe and grow by in situ star formation and hierarchical merging. Stars begin to form relatively quickly in sub-galactic sized building blocks called haloes which are subsequently assembled into galaxies. However, exactly when this assembly takes place is a matter of some debate. Here we report that the stellar masses of brightest cluster galaxies, which are the most luminous objects emitting stellar light, some 9 billion years ago are not significantly different from their stellar masses today. Brightest cluster galaxies are almost fully assembled 4-5 Gyrs after the Big Bang, having grown to more than 90% of their final stellar mass by this time. Our data conflict with the most recent galaxy formation models based on the largest simulations of dark matter halo development. These models predict protracted formation of brightest cluster galaxies over a Hubble time, with only 22% of the stellar mass assembled at the epoc...

  17. The Superwind Galaxy NGC 4666

    Science.gov (United States)

    2010-09-01

    The galaxy NGC 4666 takes pride of place at the centre of this new image, made in visible light with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile. NGC 4666 is a remarkable galaxy with very vigorous star formation and an unusual "superwind" of out-flowing gas. It had previously been observed in X-rays by the ESA XMM-Newton space telescope, and the image presented here was taken to allow further study of other objects detected in the earlier X-ray observations. The prominent galaxy NGC 4666 in the centre of the picture is a starburst galaxy, about 80 million light-years from Earth, in which particularly intense star formation is taking place. The starburst is thought to be caused by gravitational interactions between NGC 4666 and its neighbouring galaxies, including NGC 4668, visible to the lower left. These interactions often spark vigorous star-formation in the galaxies involved. A combination of supernova explosions and strong winds from massive stars in the starburst region drives a vast flow of gas from the galaxy into space - a so-called "superwind". The superwind is huge in scale, coming from the bright central region of the galaxy and extending for tens of thousands of light-years. As the superwind gas is very hot it emits radiation mostly as X-rays and in the radio part of the spectrum and cannot be seen in visible light images such as the one presented here. This image was made as part of a follow-up to observations made with the ESA XMM-Newton space telescope in X-rays. NGC 4666 was the target of the original XMM-Newton observations, but thanks to the telescope's wide field-of-view many other X-ray sources were also seen in the background. One such serendipitous detection is a faint galaxy cluster seen close to the bottom edge of the image, right of centre. This cluster is much further away from us than NGC 4666, at a distance of about three billion light-years. In order to fully understand the nature of

  18. Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies

    CERN Document Server

    Darg, D W; Lintott, C J; Schawinski, K; Sarzi, M; Bamford, S; Silk, J; Proctor, R; Andreescu, D; Murray, P; Nichol, R C; Raddick, M J; Slosar, A; Szalay, A S; Thomas, D; Vandenberg, J

    2009-01-01

    We present the largest, most homogeneous catalogue of merging galaxies in the nearby universe obtained through the Galaxy Zoo project - an interface on the world-wide web enabling large-scale morphological classification of galaxies through visual inspection of images from the Sloan Digital Sky Survey (SDSS). The method converts a set of visually-inspected classifications for each galaxy into a single parameter (the 'weighted-merger-vote fraction', f_m) which describes our confidence that the system is part of an ongoing merger. We describe how f_m is used to create a catalogue of 3003 visually-selected pairs of merging galaxies from the SDSS in the redshift range 0.005 < z <0.1. We use our merger sample and values of f_m applied to the SDSS Main Galaxy Spectral sample (MGS) to estimate that the fraction of volume-limited (M_r < -20.55) major mergers (1/3 < M_1/M_2 < 3) in the nearby universe is 1-3%. Having visually classified the morphologies of the constituent galaxies in our mergers, we fin...

  19. Thermally induced magnetic relaxation in square artificial spin ice

    Science.gov (United States)

    Andersson, M. S.; Pappas, S. D.; Stopfel, H.; Östman, E.; Stein, A.; Nordblad, P.; Mathieu, R.; Hjörvarsson, B.; Kapaklis, V.

    2016-11-01

    The properties of natural and artificial assemblies of interacting elements, ranging from Quarks to Galaxies, are at the heart of Physics. The collective response and dynamics of such assemblies are dictated by the intrinsic dynamical properties of the building blocks, the nature of their interactions and topological constraints. Here we report on the relaxation dynamics of the magnetization of artificial assemblies of mesoscopic spins. In our model nano-magnetic system - square artificial spin ice – we are able to control the geometrical arrangement and interaction strength between the magnetically interacting building blocks by means of nano-lithography. Using time resolved magnetometry we show that the relaxation process can be described using the Kohlrausch law and that the extracted temperature dependent relaxation times of the assemblies follow the Vogel-Fulcher law. The results provide insight into the relaxation dynamics of mesoscopic nano-magnetic model systems, with adjustable energy and time scales, and demonstrates that these can serve as an ideal playground for the studies of collective dynamics and relaxations.

  20. Thermally induced magnetic relaxation in square artificial spin ice.

    Science.gov (United States)

    Andersson, M S; Pappas, S D; Stopfel, H; Östman, E; Stein, A; Nordblad, P; Mathieu, R; Hjörvarsson, B; Kapaklis, V

    2016-11-24

    The properties of natural and artificial assemblies of interacting elements, ranging from Quarks to Galaxies, are at the heart of Physics. The collective response and dynamics of such assemblies are dictated by the intrinsic dynamical properties of the building blocks, the nature of their interactions and topological constraints. Here we report on the relaxation dynamics of the magnetization of artificial assemblies of mesoscopic spins. In our model nano-magnetic system - square artificial spin ice - we are able to control the geometrical arrangement and interaction strength between the magnetically interacting building blocks by means of nano-lithography. Using time resolved magnetometry we show that the relaxation process can be described using the Kohlrausch law and that the extracted temperature dependent relaxation times of the assemblies follow the Vogel-Fulcher law. The results provide insight into the relaxation dynamics of mesoscopic nano-magnetic model systems, with adjustable energy and time scales, and demonstrates that these can serve as an ideal playground for the studies of collective dynamics and relaxations.

  1. Gas Dynamics in Galaxy Clusters

    Science.gov (United States)

    McCourt, Michael Kingsley, Jr.

    Galaxy clusters are the most massive structures in the universe and, in the hierarchical pattern of cosmological structure formation, the largest objects in the universe form last. Galaxy clusters are thus interesting objects for a number of reasons. Three examples relevant to this thesis are: 1. Constraining the properties of dark energy: Due to the hierarchical nature of structure formation, the largest objects in the universe form last. The cluster mass function is thus sensitive to the entire expansion history of the universe and can be used to constrain the properties of dark energy. This constraint complements others derived from the CMB or from Type Ia supernovae and provides an important, independent confirmation of such methods. In particular, clusters provide detailed information about the equation of state parameter w because they sample a large redshift range z ˜ 0 - 1. 2. Probing galaxy formation: Clusters contain the most massive galaxies in the uni- verse, and the most massive black holes; because clusters form so late, we can still witness the assembly of these objects in the nearby universe. Clusters thus provide a more detailed view of galaxy formation than is possible in studies of lower-mass ob- jects. An important example comes from x-ray studies of clusters, which unexpectedly found that star formation in massive galaxies in clusters is closely correlated with the properties of the hot, virialized gas in their halos. This correlation persists despite the enormous separation in temperature, in dynamical time-scales, and in length-scales between the virialized gas in the halo and the star-forming regions in the galaxy. This remains a challenge to interpret theoretically. 3. Developing our knowledge of dilute plasmas: The masses and sizes of galaxy clusters imply that the plasma which permeates them is both very hot (˜ 108 K) and very dilute (˜ 10 -2 cm-3). This plasma is collisional enough to be considered a fluid, but collisionless enough to

  2. Grueneisen relaxation photoacoustic microscopy

    Science.gov (United States)

    Wang, Lidai; Zhang, Chi; Wang, Lihong V.

    2014-01-01

    The temperature-dependent property of the Grueneisen parameter has been employed in photoacoustic imaging mainly to measure tissue temperature. Here we explore this property using a different approach and develop Grueneisen-relaxation photoacoustic microscopy (GR-PAM), a technique that images non-radiative absorption with confocal optical resolution. GR-PAM sequentially delivers two identical laser pulses with a micro-second-scale time delay. The first laser pulse generates a photoacoustic signal and thermally tags the in-focus absorbers. Owing to the temperature dependence of the Grueneisen parameter, when the second laser pulse excites the tagged absorbers within the thermal relaxation time, a photoacoustic signal stronger than the first one is produced. GR-PAM detects the amplitude difference between the two co-located photoacoustic signals, confocally imaging the non-radiative absorption. We greatly improved axial resolution from 45 µm to 2.3 µm and at the same time slightly improved lateral resolution from 0.63 µm to 0.41 µm. In addition, the optical sectioning capability facilitates the measurement of the absolute absorption coefficient without fluence calibration. PMID:25379919

  3. SPIDER IX - Classifying Galaxy Groups SPIDER IX - Classifying Galaxy Groups according to their Velocity Distribution

    CERN Document Server

    Ribeiro, A L B; de Carvalho, R R; La Barbera, F; Trevisan, M; Lopes, P A; Capelato, H V

    2013-01-01

    We introduce a new method to study the velocity distribution of galaxy systems, the Hellinger Distance (HD) - designed for detecting departures from a Gaussian velocity distribution. We define a relaxed galactic system as the one with unimodal velocity distribution and a normality deviation below a critical value (HD= 20) systems are significantly larger than in low multiplicity ones (N) and the gaussianity of the velocity distribution of the groups. Bright galaxies (M_r <=-20.7) residing in the inner and outer regions of groups, do not show significant differences in the listed quantities regardless if the group has a Gaussian (G) or a Non-Gaussian (NG) velocity distribution. However, the situation is significantly different when we examine the faint galaxies (-20.7galaxy properties of the inner and outer galaxy populations, testifying how the environment is affecting the galaxies. Instead, in NG groups there is no segregation b...

  4. First LOFAR results on galaxy clusters

    CERN Document Server

    Ferrari, C; Bonafede, A; Bîrzan, L; Brüggen, M; Brunetti, G; Cassano, R; Conway, J; De Gasperin, F; Heald, G; Jackson, N; Macario, G; McKean, J; Offringa, A R; Orrù, E; Pizzo, R; Rafferty, D A; Röttgering, H J A; Shulevski, A; Tasse, C; van der Tol, S; van Weeren, R J; Wise, M; van Zwieten, J E

    2012-01-01

    Deep radio observations of galaxy clusters have revealed the existence of diffuse radio sources related to the presence of relativistic electrons and weak magnetic fields in the intracluster volume. The role played by this non-thermal intracluster component on the thermodynamical evolution of galaxy clusters is debated, with important implications for cosmological and astrophysical studies of the largest gravitationally bound structures of the Universe. The low surface brightness and steep spectra of diffuse cluster radio sources make them more easily detectable at low-frequencies. LOFAR is the first instrument able to detect diffuse radio emission in hundreds of massive galaxy clusters up to their formation epoch. We present the first observations of clusters imaged by LOFAR and the huge perspectives opened by this instrument for non-thermal cluster studies.

  5. The formation history of elliptical galaxies

    CERN Document Server

    De Lucia, G; White, S D M; Croton, D; Kauffmann, G; Lucia, Gabriella De; Springel, Volker; White, Simon D. M.; Croton, Darren; Kauffmann, Guinevere

    2006-01-01

    We take advantage of the largest high-resolution simulation of cosmic structure growth ever carried out -- the Millennium Simulation of the concordance LambdaCDM cosmogony -- to study how the star formation histories, ages and metallicities of elliptical galaxies depend on environment and on stellar mass. We concentrate on a galaxy formation model which is tuned to fit the joint luminosity/colour/morphology/clustering distribution of low redshift galaxies. Massive ellipticals in this model have higher metal abundances, older luminosity-weighted ages, shorter star formation timescales, but lower assembly redshifts than less massive systems. Within clusters the typical masses, ages and metal abundances of ellipticals are predicted to decrease, on average, with increasing distance from the cluster centre. We also quantify the effective number of progenitors of ellipticals as a function of present stellar mass, finding typical numbers below 2 for M* < 10^{11} Msun, rising to about 5 for the most massive system...

  6. The EAGLE simulations: atomic hydrogen associated with galaxies

    CERN Document Server

    Crain, Robert A; Lagos, Claudia del P; Rahmati, Alireza; Schaye, Joop; McCarthy, Ian G; Marasco, Antonino; Bower, Richard G; Schaller, Matthieu; Theuns, Tom; van der Hulst, Thijs

    2016-01-01

    We examine the properties of atomic hydrogen (HI) associated with galaxies in the EAGLE simulations of galaxy formation. EAGLE's feedback parameters were calibrated to reproduce the stellar mass function and galaxy sizes at $z=0.1$, and we assess whether this calibration also yields realistic HI properties. We estimate the self-shielding density with a fitting function calibrated using radiation transport simulations, and correct for molecular hydrogen with empirical or theoretical relations. The `standard-resolution' simulations systematically underestimate HI column densities, leading to an HI deficiency in low-mass ($M_\\star < 10^{10}M_\\odot$) galaxies and poor reproduction of the observed HI mass function. These shortcomings are largely absent from EAGLE simulations featuring a factor of 8 (2) better mass (spatial) resolution, within which the HI mass of galaxies evolves more mildly from $z=1$ to $0$ than in the standard-resolution simulations. The largest-volume simulation reproduces the observed clus...

  7. Detecting the orientation of magnetic fields in galaxy clusters

    CERN Document Server

    Pfrommer, Christoph

    2009-01-01

    Clusters of galaxies, filled with hot, magnetised plasma, are the largest bound objects in existence and an important touchstone in understanding the formation of structures in our Universe. Because in clusters, thermal conduction follows field lines, magnetic fields strongly shape the cluster's thermal history, which remains mysterious; some should have long since cooled and collapsed. In a seemingly unrelated puzzle, recent observations of Virgo cluster spiral galaxies imply ridges of strong, coherent magnetic fields offset from their centre. Here we demonstrate, using 3D magneto-hydrodynamical simulations, that such ridges are easily explained by galaxies sweeping up field lines as they orbit inside the cluster. This magnetic drape is then literally lit up with cosmic rays from the galaxies' stars, generating coherent polarised emission at the galaxies' leading edges. This immediately presents a first technique for probing local orientations and characteristic length scales of cluster magnetic fields. The ...

  8. The Environmental Impact of Lyman-break Galaxies

    CERN Document Server

    Tasker, E J; Bryan, Greg L.; Tasker, Elizabeth J.

    2006-01-01

    We perform cosmological simulations of galaxies forming at z=3 using the hydrodynamics grid code, Enzo. By selecting the largest galaxies in the volume to correspond to Lyman-break galaxies, we construct observational spectra of the HI flux distribution around these objects, as well as column densities of CIV and OVI throughout a refined region. We successfully reproduce the most recent observations of the mean HI flux in the close vicinity of Lyman-break galaxies but see no evidence for the proximity effect in earlier observations. While our galaxies do return metals to the IGM, their quantity and volume appears to be somewhat less than observed. We conclude that either we do not adequately resolve galactic winds, or that at least some of the intergalactic metal enrichment is by early epoch objects whose mass is smaller than our minimum resolved halo mass.

  9. H.E.S.S. observations of galaxy clusters

    CERN Document Server

    Domainko, W; Hinton, J A; Martineau-Huynh, O; De Naurois, Mathieu; Nedbal, D; Pedaletti, G; Rowell, G

    2007-01-01

    Clusters of galaxies, the largest gravitationally bound objects in the universe, are expected to contain a significant population of hadronic and leptonic cosmic rays. Potential sources for these particles are merger and accretion shocks, starburst driven galactic winds and radio galaxies. Furthermore, since galaxy clusters confine cosmic ray protons up to energies of at least 1 PeV for a time longer than the Hubble time they act as storehouses and accumulate all the hadronic particles which are accelerated within them. Consequently clusters of galaxies are potential sources of VHE (> 100 GeV) gamma rays. Motivated by these considerations, promising galaxy clusters are observed with the H.E.S.S. experiment as part of an ongoing campaign. Here, upper limits for the VHE gamma ray emission for the Abell 496 and Coma cluster systems are reported.

  10. Star Formation in Irregular Galaxies.

    Science.gov (United States)

    Hunter, Deidre; Wolff, Sidney

    1985-01-01

    Examines mechanisms of how stars are formed in irregular galaxies. Formation in giant irregular galaxies, formation in dwarf irregular galaxies, and comparisons with larger star-forming regions found in spiral galaxies are considered separately. (JN)

  11. An Intensive HST Survey for z>1 Supernovae by Targeting Galaxy Clusters

    CERN Document Server

    Dawson, K S; Amanullah, R; Barbary, K; Barrientos, L F; Brodwin, M; Connolly, N; Dey, A; Doi, M; Donahue, M; Eisenhardt, P; Ellingson, E; Faccioli, L; Fadeev, V; Fakhouri, H K; Fruchter, A S; Gilbank, D G; Gladders, M D; Goldhaber, G; González, A H; Goobar, A; Gude, A; Hattori, T; Hoekstra, H; Huang, X; Ihara, Y; Jannuzi, B T; Johnston, D; Kashikawa, K; Koester, B; Konishi, K; Kowalski, M; Lidman, C; Linder, E V; Lubin, L; Meyers, J; Morokuma, T; Munshi, F; Mullis, C; Oda, T; Panagia, N; Perlmutter, S; Postman, M; Pritchard, T; Rhodes, J; Rosati, P; Rubin, D; Schlegel, D J; Spadafora, A; Stanford, S A; Stanishev, V; Stern, D; Strovink, M; Suzuki, N; Takanashi, N; Tokita, K; Wagner, M; Wang, L; Yasuda, N; Yee, H K C

    2009-01-01

    We present a new survey strategy to discover and study high redshift Type Ia supernovae (SNe Ia) using the Hubble Space Telescope (HST). By targeting massive galaxy clusters at 0.90.95, nine of which were in galaxy clusters. This strategy provides a SN sample that can be used to decouple the effects of host galaxy extinction and intrinsic color in high redshift SNe, thereby reducing one of the largest systematic uncertainties in SN cosmology.

  12. Combining Galaxy-Galaxy Lensing and Galaxy Clustering

    Energy Technology Data Exchange (ETDEWEB)

    Park, Youngsoo [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Krause, Elisabeth [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Dodelson, Scott [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Jain, Bhuvnesh [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Amara, Adam [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Becker, Matt [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Bridle, Sarah [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Clampitt, Joseph [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Crocce, Martin [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Honscheid, Klaus [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Gaztanaga, Enrique [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Sanchez, Carles [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Wechsler, Risa [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2015-01-01

    Combining galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth rate of large scale structure, a quantity that will shed light on the mechanism driving the acceleration of the Universe. The Dark Energy Survey (DES) is a prime candidate for such an analysis, with its measurements of both the distribution of galaxies on the sky and the tangential shears of background galaxies induced by these foreground lenses. By constructing an end-to-end analysis that combines large-scale galaxy clustering and small-scale galaxy-galaxy lensing, we also forecast the potential of a combined probes analysis on DES datasets. In particular, we develop a practical approach to a DES combined probes analysis by jointly modeling the assumptions and systematics affecting the different components of the data vector, employing a shared halo model, HOD parametrization, photometric redshift errors, and shear measurement errors. Furthermore, we study the effect of external priors on different subsets of these parameters. We conclude that DES data will provide powerful constraints on the evolution of structure growth in the universe, conservatively/ optimistically constraining the growth function to 8%/4.9% with its first-year data covering 1000 square degrees, and to 4%/2.3% with its full five-year data covering 5000 square degrees.

  13. Magnetoviscosity and relaxation in ferrofluids

    Science.gov (United States)

    Felderhof

    2000-09-01

    The increase in viscosity of a ferrofluid due to an applied magnetic field is discussed on the basis of a phenomenological relaxation equation for the magnetization. The relaxation equation was derived earlier from irreversible thermodynamics, and differs from that postulated by Shliomis. The two relaxation equations lead to a different dependence of viscosity on magnetic field, unless the relaxation rates are related in a specific field-dependent way. Both planar Couette flow and Poiseuille pipe flow in parallel and perpendicular magnetic field are discussed. The entropy production for these situations is calculated and related to the magnetoviscosity.

  14. [Death in a relaxation tank].

    Science.gov (United States)

    Rupp, Wolf; Simon, Karl-Heinz; Bohnert, Michael

    2009-01-01

    Complete relaxation can be achieved by floating in a darkened, sound-proof relaxation tank filled with salinated water kept at body temperature. Under these conditions, meditation exercises up to self-hypnosis may lead to deep relaxation with physical and mental revitalization. A user manipulated his tank, presumably to completely cut off all optical and acoustic stimuli and accidentally also covered the ventilation hole. The man was found dead in his relaxation tank. The findings suggested lack of oxygen as the cause of death.

  15. EARLY-TYPE GALAXIES WITH TIDAL DEBRIS AND THEIR SCALING RELATIONS IN THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S{sup 4}G)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Taehyun; Sheth, Kartik; Munoz-Mateos, Juan-Carlos [National Radio Astronomy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Hinz, Joannah L.; Zaritsky, Dennis [Steward Observatory University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Lee, Myung Gyoon [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); Gadotti, Dimitri A. [European Southern Observatory, Casilla 19001, Santiago 19 (Chile); Knapen, Johan H. [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain); Schinnerer, Eva [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, 69117 Heidelberg (Germany); Ho, Luis C.; Madore, Barry F. [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Laurikainen, Eija; Salo, Heikki [Division of Astronomy, Department of Physical Sciences, University of Oulu, Oulu FIN-90014 (Finland); Athanassoula, E.; Bosma, Albert [Laboratoire d' Astrophysique de Marseille (LAM), UMR6110, Universite de Provence/CNRS, Technopole de Marseille Etoile, 38 rue Frederic Joliot Curie, 13388 Marseille Cedex 20 (France); De Swardt, Bonita [South African Astronomical Observatory, Observatory 7935, Cape Town (South Africa); Comeron, Sebastien [Korea Astronomy and Space Science Institute, 61-1 Hwaamdong, Yuseong-gu, Daejeon 305-348 (Korea, Republic of); Regan, Michael W. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Menendez-Delmestre, Karin [Observatorio do Valongo, Universidade Federal do Rio de Janeiro, Ladeira Pedro Antonio, 43, Saude CEP 20080-090 Rio de Janeiro, RJ (Brazil); De Paz, Armando Gil [Departamento de Astrofisica, Universidad Complutense de Madrid, E-28040 Madrid (Spain); and others

    2012-07-01

    Tidal debris around galaxies can yield important clues on their evolution. We have identified tidal debris in 11 early-type galaxies (T {<=} 0) from a sample of 65 early types drawn from the Spitzer Survey of Stellar Structure in Galaxies (S{sup 4}G). The tidal debris includes features such as shells, ripples, and tidal tails. A variety of techniques, including two-dimensional decomposition of galactic structures, were used to quantify the residual tidal features. The tidal debris contributes {approx}3%-10% to the total 3.6 {mu}m luminosity of the host galaxy. Structural parameters of the galaxies were estimated using two-dimensional profile fitting. We investigate the locations of galaxies with tidal debris in the fundamental plane and Kormendy relation. We find that galaxies with tidal debris lie within the scatter of early-type galaxies without tidal features. Assuming that the tidal debris is indicative of recent gravitational interaction or merger, this suggests that these galaxies have either undergone minor merging events so that the overall structural properties of the galaxies are not significantly altered, or they have undergone a major merging events but already have experienced sufficient relaxation and phase mixing so that their structural properties become similar to those of the non-interacting early-type galaxies.

  16. SPIDER - IX. Classifying galaxy groups according to their velocity distribution

    Science.gov (United States)

    Ribeiro, A. L. B.; de Carvalho, R. R.; Trevisan, M.; Capelato, H. V.; La Barbera, F.; Lopes, P. A. A.; Schilling, A. C.

    2013-09-01

    We introduce a new method to study the velocity distribution of galaxy systems, the Hellinger Distance (HD), designed for detecting departures from a Gaussian velocity distribution. Testing different approaches to measure normality of a distribution, we conclude that HD is the least vulnerable method to type I and II statistical errors. We define a relaxed galactic system as the one with unimodal velocity distribution and a normality deviation below a critical value (HD ) and the Gaussianity of the velocity distribution of the groups. Bright galaxies (Mr ≤ -20.7) residing in the inner and outer regions of groups do not show significant differences in the listed quantities regardless if the group has a Gaussian (G) or a Non-Gaussian (NG) velocity distribution. However, the situation is significantly different when we examine the faint galaxies (-20.7 < Mr ≤ -17.9). In G groups, there is a remarkable difference between the galaxy properties of the inner and outer galaxy populations, testifying how the environment is affecting the galaxies. Instead, in NG groups there is no segregation between the properties of galaxies in the inner and outer regions, showing that the properties of these galaxies still reflect the physical processes prevailing in the environment where they were found earlier.

  17. A Connection Between Bulge Properties and the Bimodality of Galaxies

    CERN Document Server

    Drory, Niv

    2007-01-01

    The global colors of galaxies have recently been shown to follow bimodal distributions. Galaxies separate into a ``red sequence'', populated prototypically by early-type galaxies, and a ``blue cloud'', whose typical objects are late-type disk galaxies. Intermediate-type (Sa-Sbc) galaxies populate both regions. It has been suggested that this bimodality reflects the two-component nature of disk-bulge galaxies. However, it has now been established that there are two types of bulges: ``classical bulges'' that are dynamically hot systems resembling (little) ellipticals, and ``pseudobulges'', dynamically cold, flattened, disk-like structures that could not have formed via violent relaxation. Therefore thee question is whether at types Sa-Sbc, where both bulge types are found, the red-blue dichotomy separates galaxies at some value of disk-to-bulge ratio, $B/T$, or, whether it separates galaxies of different bulge type, irrespective of their $B/T$. We identify classical bulges and pseudobulges morphologically with ...

  18. Relaxing Behavioural Inheritance

    Directory of Open Access Journals (Sweden)

    Nuno Amálio

    2013-05-01

    Full Text Available Object-oriented (OO inheritance allows the definition of families of classes in a hierarchical way. In behavioural inheritance, a strong version, it should be possible to substitute an object of a subclass for an object of its superclass without any observable effect on the system. Behavioural inheritance is related to formal refinement, but, as observed in the literature, the refinement constraints are too restrictive, ruling out many useful OO subclassings. This paper studies behavioural inheritance in the context of ZOO, an object-oriented style for Z. To overcome refinement's restrictions, this paper proposes relaxations to the behavioural inheritance refinement rules. The work is presented for Z, but the results are applicable to any OO language that supports design-by-contract.

  19. Guaranteeing uptime at worl's largest particle physics lab

    CERN Multimedia

    Brodkin, Jon

    2007-01-01

    "As the European agency CERN was gearing up to build the world's largest particle accelerator, officials there knew they could not afford to have problems in their technical infrastructure cause any downtime." (1 page)

  20. The World Largest Small Satellite R&D Center Completed

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    The National Institute of Small Satellite Research and Applications, constructed by Dongfanghong Satellite Company,was completed on December 14,2004. It is the world largest satellite research and development center.

  1. Construction starts for largest botanical garden in the world

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ The cornerstone was laid on 30 May for the Qinling Botanical Garden, which boasts the world's largest one in terms of space, in Zhouzhi County of Xi'an, capital of northwest China's Shaanxi Province.

  2. Online uniform machine covering with the known largest size

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper investigates the semi-online scheduling problem with the known largest size on two uniform machines. The objective is to maximize the minimum machine completion time. Both lower bounds and algorithms are given. Algorithms are optimal for the majority values of s≥1, where s is the speed ratio of the two machines. The largest gap between the competitive ratio and the lower bound is about 0. 064. Moreover, the overall competitive ratio 2 matches the overall lower bound.

  3. Branding elements : A study of the largest Latvian companies

    OpenAIRE

    Rageviciusa, Dina

    2014-01-01

    The thesis studied branding elements and management in the largest Latvian companies. The objective of the research is to provide overview information of branding elements, which are used among the largest Latvian companies. The theoretical framework consists of information about the most common and significant branding elements, their management and impact including what the successful use of branding elements can bring to the company. All that was viewed from three scopes – theory, exam...

  4. Shell Becomes 3rd Largest Lubricants Provider in China

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Royal Dutch Shell Group has bought a 75percent stake in China's largest privately owned lubricant oil company Tongyi, making it the third largest in China's lubricants market, based on the recent report from the Chinese news media."The transaction will increase Shell's global finished lubricants volume by 8 percent, giving it approximately 16 percent of the global branded finished lubricants market," the company said in a statement.

  5. The relation between gas density and velocity power spectra in galaxy clusters: qualitative treatment and cosmological simulations

    CERN Document Server

    Zhuravleva, I; Schekochihin, A A; Lau, E T; Nagai, D; Gaspari, M; Allen, S W; Nelson, K; Parrish, I J

    2014-01-01

    We address the problem of evaluating the power spectrum of the velocity field of the ICM using only information on the plasma density fluctuations, which can be measured today by Chandra and XMM-Newton observatories. We argue that for relaxed clusters there is a linear relation between the rms density and velocity fluctuations across a range of scales, from the largest ones, where motions are dominated by buoyancy, down to small, turbulent scales: $(\\delta\\rho_k/\\rho)^2 = \\eta_1^2 (V_{1,k}/c_s)^2$, where $\\delta\\rho_k/\\rho$ is the spectral amplitude of the density perturbations at wave number $k$, $V_{1,k}^2=V_k^2/3$ is the mean square component of the velocity field, $c_s$ is the sound speed, and $\\eta_1$ is a dimensionless constant of order unity. Using cosmological simulations of relaxed galaxy clusters, we calibrate this relation and find $\\eta_1\\approx 1 \\pm 0.3$. We argue that this value is set at large scales by buoyancy physics, while at small scales the density and velocity power spectra are proporti...

  6. Galaxy International Mall Unveiled

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    An agreement between Galaxy International Mall (hereinafter referred to as Galaxy) and its three main partners was signed on January 12, 2011, in the city of Tianjin. The partners are Lotte Department

  7. The Void Galaxy Survey

    CERN Document Server

    van de Weygaert, R; Platen, E; Beygu, B; van Gorkom, J H; van der Hulst, J M; Aragon-Calvo, M A; Peebles, P J E; Jarrett, T; Rhee, G; Kovac, K; Yip, C -W

    2011-01-01

    The Void Galaxy Survey (VGS) is a multi-wavelength program to study $\\sim$60 void galaxies. Each has been selected from the deepest interior regions of identified voids in the SDSS redshift survey on the basis of a unique geometric technique, with no a prior selection of intrinsic properties of the void galaxies. The project intends to study in detail the gas content, star formation history and stellar content, as well as kinematics and dynamics of void galaxies and their companions in a broad sample of void environments. It involves the HI imaging of the gas distribution in each of the VGS galaxies. Amongst its most tantalizing findings is the possible evidence for cold gas accretion in some of the most interesting objects, amongst which are a polar ring galaxy and a filamentary configuration of void galaxies. Here we shortly describe the scope of the VGS and the results of the full analysis of the pilot sample of 15 void galaxies.

  8. Watching a Cannibal Galaxy Dine

    Science.gov (United States)

    2009-11-01

    A new technique using near-infrared images, obtained with ESO's 3.58-metre New Technology Telescope (NTT), allows astronomers to see through the opaque dust lanes of the giant cannibal galaxy Centaurus A, unveiling its "last meal" in unprecedented detail - a smaller spiral galaxy, currently twisted and warped. This amazing image also shows thousands of star clusters, strewn like glittering gems, churning inside Centaurus A. Centaurus A (NGC 5128) is the nearest giant, elliptical galaxy, at a distance of about 11 million light-years. One of the most studied objects in the southern sky, by 1847 the unique appearance of this galaxy had already caught the attention of the famous British astronomer John Herschel, who catalogued the southern skies and made a comprehensive list of nebulae. Herschel could not know, however, that this beautiful and spectacular appearance is due to an opaque dust lane that covers the central part of the galaxy. This dust is thought to be the remains of a cosmic merger between a giant elliptical galaxy and a smaller spiral galaxy full of dust. Between 200 and 700 million years ago, this galaxy is indeed believed to have consumed a smaller spiral, gas-rich galaxy - the contents of which appear to be churning inside Centaurus A's core, likely triggering new generations of stars. First glimpses of the "leftovers" of this meal were obtained thanks to observations with the ESA Infrared Space Observatory , which revealed a 16 500 light-year-wide structure, very similar to that of a small barred galaxy. More recently, NASA's Spitzer Space Telescope resolved this structure into a parallelogram, which can be explained as the remnant of a gas-rich spiral galaxy falling into an elliptical galaxy and becoming twisted and warped in the process. Galaxy merging is the most common mechanism to explain the formation of such giant elliptical galaxies. The new SOFI images, obtained with the 3.58-metre New Technology Telescope at ESO's La Silla Observatory

  9. Magnetic relaxation in anisotropic magnets

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker

    1971-01-01

    The line shape and the kinematic and thermodynamic slowing down of the critical and paramagnetic relaxation in axially anisotropic materials are discussed. Kinematic slowing down occurs only in the longitudinal relaxation function. The thermodynamic slowing down occurs in either the transverse or...

  10. A Cluster and a Sea of Galaxies

    Science.gov (United States)

    2010-05-01

    A new wide-field image released today by ESO displays many thousands of distant galaxies, and more particularly a large group belonging to the massive galaxy cluster known as Abell 315. As crowded as it may appear, this assembly of galaxies is only the proverbial "tip of the iceberg", as Abell 315 - like most galaxy clusters - is dominated by dark matter. The huge mass of this cluster deflects light from background galaxies, distorting their observed shapes slightly. When looking at the sky with the unaided eye, we mostly only see stars within our Milky Way galaxy and some of its closest neighbours. More distant galaxies are just too faint to be perceived by the human eye, but if we could see them, they would literally cover the sky. This new image released by ESO is both a wide-field and long-exposure one, and reveals thousands of galaxies crowding an area on the sky roughly as large as the full Moon. These galaxies span a vast range of distances from us. Some are relatively close, as it is possible to distinguish their spiral arms or elliptical halos, especially in the upper part of the image. The more distant appear just like the faintest of blobs - their light has travelled through the Universe for eight billion years or more before reaching Earth. Beginning in the centre of the image and extending below and to the left, a concentration of about a hundred yellowish galaxies identifies a massive galaxy cluster, designated with the number 315 in the catalogue compiled by the American astronomer George Abell in 1958 [1]. The cluster is located between the faint, red and blue galaxies and the Earth, about two billion light-years away from us. It lies in the constellation of Cetus (the Whale). Galaxy clusters are some of the largest structures in the Universe held together by gravity. But there is more in these structures than the many galaxies we can see. Galaxies in these giants contribute to only ten percent of the mass, with hot gas in between galaxies

  11. The dark matter of galaxy voids

    Science.gov (United States)

    Sutter, P. M.; Lavaux, Guilhem; Wandelt, Benjamin D.; Weinberg, David H.; Warren, Michael S.

    2014-03-01

    How do observed voids relate to the underlying dark matter distribution? To examine the spatial distribution of dark matter contained within voids identified in galaxy surveys, we apply Halo Occupation Distribution models representing sparsely and densely sampled galaxy surveys to a high-resolution N-body simulation. We compare these galaxy voids to voids found in the halo distribution, low-resolution dark matter and high-resolution dark matter. We find that voids at all scales in densely sampled surveys - and medium- to large-scale voids in sparse surveys - trace the same underdensities as dark matter, but they are larger in radius by ˜20 per cent, they have somewhat shallower density profiles and they have centres offset by ˜ 0.4Rv rms. However, in void-to-void comparison we find that shape estimators are less robust to sampling, and the largest voids in sparsely sampled surveys suffer fragmentation at their edges. We find that voids in galaxy surveys always correspond to underdensities in the dark matter, though the centres may be offset. When this offset is taken into account, we recover almost identical radial density profiles between galaxies and dark matter. All mock catalogues used in this work are available at http://www.cosmicvoids.net.

  12. The Challenge of the Largest Structures in the Universe to Cosmology

    CERN Document Server

    Park, Changbom; Kim, Juhan; Gott, J Richard; Kim, Sungsoo S; Kim, Kap-Sung

    2012-01-01

    Large galaxy redshift surveys have long been used to constrain cosmological models and structure formation scenarios. In particular, the largest structures discovered observationally are thought to carry critical information on the amplitude of large-scale density fluctuations or homogeneity of the universe, and have often challenged the standard cosmological framework. The Sloan Great Wall (SGW) recently found in the Sloan Digital Sky Survey (SDSS) region casts doubt on the concordance cosmological model with a cosmological constant (i.e. the flat LCDM model). Here we show that the existence of the SGW is perfectly consistent with the LCDM model, a result that only our very large cosmological N-body simulation (the Horizon Run 2, HR2) could supply. In addition, we report on the discovery of a void complex in the SDSS much larger than the SGW, and show that such size of the largest void is also predicted in the LCDM paradigm. Our results demonstrate that an initially homogeneous isotropic universe with primor...

  13. Identifying dynamically young galaxy groups via wide-angle tail galaxies: A case study in the COSMOS field at z=0.53

    CERN Document Server

    Oklopcic, A; Giodini, S; Zamorani, G; Birzan, L; Schinnerer, E; Carilli, C L; Finoguenov, A; Lilly, S; Koekemoer, A; Scoville, N Z

    2010-01-01

    We present an analysis of a wide-angle tail (WAT) radio galaxy located in a galaxy group in the COSMOS field at a redshift of z=0.53 (hereafter CWAT-02). We find that the host galaxy of CWAT-02 is the brightest galaxy in the group, although it does not coincide with the center of mass of the system. Estimating a) the velocity of CWAT-02, relative to the intra-cluster medium (ICM), and b) the line-of-sight peculiar velocity of CWAT-02's host galaxy, relative to the average velocity of the group, we find that both values are higher than those expected for a dominant galaxy in a relaxed system. This suggests that CWAT-02's host group is dynamically young and likely in the process of an ongoing group merger. Our results are consistent with previous findings showing that the presence of a wide-angle tail galaxy in a galaxy group or cluster can be used as an indicator of dynamically young non-relaxed systems. Taking the unrelaxed state of CWAT-02's host group into account, we discuss the impact of radio-AGN heating...

  14. The Galaxy End Sequence

    CERN Document Server

    Eales, Stephen; Smith, Matthew; Appah, Kiran; Ciesla, Laure; Duffield, Chris; Schofield, Simon

    2016-01-01

    A common assumption is that galaxies fall in two distinct regions on a plot of specific star-formation rate (SSFR) versus galaxy stellar mass: a star-forming Galaxy Main Sequence (GMS) and a separate region of `passive' or `red and dead galaxies'. Starting from a volume-limited sample of nearby galaxies designed to contain most of the stellar mass in this volume, and thus being a fair representation of the Universe at the end of 12 billion years of galaxy evolution, we investigate the distribution of galaxies in this diagram today. We show that galaxies follow a strongly curved extended GMS with a steep negative slope at high galaxy stellar masses. There is a gradual change in the morphologies of the galaxies along this distribution, but there is no clear break between early-type and late-type galaxies. Examining the other evidence that there are two distinct populations, we argue that the `red sequence' is the result of the colours of galaxies changing very little below a critical value of the SSFR, rather t...

  15. Satellite galaxies in nearby groups of galaxies

    CERN Document Server

    Vennik, J

    2015-01-01

    We analyse distribution, kinematics and star-formation (SF) properties of satellite galaxies in three different samples of nearby groups. We find that studied groups are generally well approximated by low-concentration NFW model, show a variety of LOS velocity dispersion profiles and signs of SF quenching in outskirts of dwarf satellite galaxies.

  16. Massive Galaxies at High-z: Assembly Patterns, Structure & Dynamics in the Fast Phase of Galaxy Formation

    CERN Document Server

    Oñorbe, J; Domínguez-Tenreiro, R; Knebe, A; Serna, A

    2011-01-01

    Relaxed, massive galactic objects have been identified at redshifts z = 4;5; and 6 in hydrodynamical simulations run in a large cosmological volume. This allowed us to analyze the assembly patterns of the high mass end of the galaxy distribution at these high zs, by focusing on their structural and dynamical properties. Our simulations indicate that massive objects at high redshift already follow certain scaling relations. These relations define virial planes at the halo scale, whereas at the galactic scale they define intrinsic dynamical planes that are, however, tilted relative to the virial plane. Therefore, we predict that massive galaxies must lie on fundamental planes from their formation. We briefly discuss the physical origin of the tilt in terms the physical processes underlying massive galaxy formation at high z, in the context of a two-phase galaxy formation scenario. Specifically, we have found that it lies on the different behavior of the gravitationally heated gas as compared with cold gas previ...

  17. Extended, regular HI structures around early-type galaxies

    CERN Document Server

    Oosterloo, T; Sadler, E M; Van der Hulst, J M; Serra, P

    2007-01-01

    We discuss the morphology and kinematics of the HI of a sample of 30 southern gas-rich early-type galaxies selected from the HI Parkes All-Sky Survey (HIPASS). This is the largest collection of high-resolution HI data of a homogeneously selected sample. Given the sensitivity of HIPASS, these galaxies represent the most HI-rich early-type galaxies. In two-thirds of the galaxies, we find the HI to be in a large, regular disk- or ring-like structure that in some cases is strongly warped. In the remaining cases we find the HI distributed in irregular tails or clouds offset from the galaxy. The giant, regular HI structures can be up to ~200 kpc in diameter and contain up to 10^10 M_sun of HI. The incidence of irregular HI structures appears to be somewhat higher in elliptical galaxies, but the large, regular structures are observed in both elliptical and S0 galaxies and are not strictly connected to the presence of a stellar disk. If these two types of galaxies are the result of different formation paths, this is ...

  18. Morphology of galaxies

    CERN Document Server

    Wadadekar, Yogesh

    2012-01-01

    The study of the morphology of galaxies is important in order to understand the formation and evolution of galaxies and their sub-components as a function of luminosity, environment, and star-formation and galaxy assembly over cosmic time. Disentangling the many variables that affect galaxy evolution and morphology, requires large galaxy samples and automated ways to measure morphology. The advent of large digital sky surveys, with unprecedented depth and resolution, coupled with sophisticated quantitative methods for morphology measurement are providing new insights in this fast evolving field of astronomical research.

  19. Interplay of inhibition and multiplexing : Largest eigenvalue statistics

    CERN Document Server

    Ghosh, Saptarshi; Ivanchenko, Mikhail V; Jalan, Sarika

    2016-01-01

    The largest eigenvalue of a network provides understanding to various dynamical as well as stability properties of the underlying system. We investigate an interplay of inhibition and multiplexing on the largest eigenvalue statistics of networks. Using numerical experiments, we demonstrate that presence of the inhibitory coupling may lead to a very different behaviour of the largest eigenvalue statistics of multiplex networks than those of the isolated networks depending upon network architecture of the individual layer. We demonstrate that there is a transition from the Weibull to the Gumbel or to the Frechet distribution as networks are multiplexed. Furthermore, for denser networks, there is a convergence to the Gumbel distribution as network size increases indicating higher stability of larger systems.

  20. The DEEP2 Galaxy Redshift Survey: The Voronoi-Delaunay Method Catalog of Galaxy Groups

    Energy Technology Data Exchange (ETDEWEB)

    Gerke, Brian F.; /UC, Berkeley; Newman, Jeffrey A.; /LBNL, NSD; Davis, Marc; /UC, Berkeley /UC, Berkeley, Astron.Dept.; Marinoni, Christian; /Brera Observ.; Yan, Renbin; Coil, Alison L.; Conroy, Charlie; Cooper, Michael C.; /UC, Berkeley, Astron.Dept.; Faber, S.M.; /Lick Observ.; Finkbeiner, Douglas P.; /Princeton U. Observ.; Guhathakurta, Puragra; /Lick Observ.; Kaiser, Nick; /Hawaii U.; Koo, David C.; Phillips, Andrew C.; /Lick Observ.; Weiner, Benjamin J.; /Maryland U.

    2012-02-14

    We use the first 25% of the DEEP2 Galaxy Redshift Survey spectroscopic data to identify groups and clusters of galaxies in redshift space. The data set contains 8370 galaxies with confirmed redshifts in the range 0.7 {<=} z {<=} 1.4, over one square degree on the sky. Groups are identified using an algorithm (the Voronoi-Delaunay Method) that has been shown to accurately reproduce the statistics of groups in simulated DEEP2-like samples. We optimize this algorithm for the DEEP2 survey by applying it to realistic mock galaxy catalogs and assessing the results using a stringent set of criteria for measuring group-finding success, which we develop and describe in detail here. We find in particular that the group-finder can successfully identify {approx}78% of real groups and that {approx}79% of the galaxies that are true members of groups can be identified as such. Conversely, we estimate that {approx}55% of the groups we find can be definitively identified with real groups and that {approx}46% of the galaxies we place into groups are interloper field galaxies. Most importantly, we find that it is possible to measure the distribution of groups in redshift and velocity dispersion, n({sigma}, z), to an accuracy limited by cosmic variance, for dispersions greater than 350 km s{sup -1}. We anticipate that such measurements will allow strong constraints to be placed on the equation of state of the dark energy in the future. Finally, we present the first DEEP2 group catalog, which assigns 32% of the galaxies to 899 distinct groups with two or more members, 153 of which have velocity dispersions above 350 km s{sup -1}. We provide locations, redshifts and properties for this high-dispersion subsample. This catalog represents the largest sample to date of spectroscopically detected groups at z {approx} 1.

  1. The DEEP2 Galaxy Redshift Survey: The Voronoi-Delaunay Method Catalog of Galaxy Groups

    Energy Technology Data Exchange (ETDEWEB)

    Gerke, Brian F.; /UC, Berkeley; Newman, Jeffrey A.; /LBNL, NSD; Davis, Marc; /UC, Berkeley /UC, Berkeley, Astron.Dept.; Marinoni, Christian; /Brera Observ.; Yan, Renbin; Coil, Alison L.; Conroy, Charlie; Cooper, Michael C.; /UC, Berkeley, Astron.Dept.; Faber, S.M.; /Lick Observ.; Finkbeiner, Douglas P.; /Princeton U. Observ.; Guhathakurta, Puragra; /Lick Observ.; Kaiser, Nick; /Hawaii U.; Koo, David C.; Phillips, Andrew C.; /Lick Observ.; Weiner, Benjamin J.; /Maryland U.

    2012-02-14

    We use the first 25% of the DEEP2 Galaxy Redshift Survey spectroscopic data to identify groups and clusters of galaxies in redshift space. The data set contains 8370 galaxies with confirmed redshifts in the range 0.7 {<=} z {<=} 1.4, over one square degree on the sky. Groups are identified using an algorithm (the Voronoi-Delaunay Method) that has been shown to accurately reproduce the statistics of groups in simulated DEEP2-like samples. We optimize this algorithm for the DEEP2 survey by applying it to realistic mock galaxy catalogs and assessing the results using a stringent set of criteria for measuring group-finding success, which we develop and describe in detail here. We find in particular that the group-finder can successfully identify {approx}78% of real groups and that {approx}79% of the galaxies that are true members of groups can be identified as such. Conversely, we estimate that {approx}55% of the groups we find can be definitively identified with real groups and that {approx}46% of the galaxies we place into groups are interloper field galaxies. Most importantly, we find that it is possible to measure the distribution of groups in redshift and velocity dispersion, n({sigma}, z), to an accuracy limited by cosmic variance, for dispersions greater than 350 km s{sup -1}. We anticipate that such measurements will allow strong constraints to be placed on the equation of state of the dark energy in the future. Finally, we present the first DEEP2 group catalog, which assigns 32% of the galaxies to 899 distinct groups with two or more members, 153 of which have velocity dispersions above 350 km s{sup -1}. We provide locations, redshifts and properties for this high-dispersion subsample. This catalog represents the largest sample to date of spectroscopically detected groups at z {approx} 1.

  2. Computers vs. Humans in Galaxy Classification

    Science.gov (United States)

    Kohler, Susanna

    2016-04-01

    54% for spirals and 80% for ellipticals, the agreement is over 98%. [Kuminski et al. 2016]In addition, the classifier calculates a certainty level for each classification, with the certainties adding to 100%: a galaxy categorized as spiral at 85% certainty is categorized as elliptical at 15% certainty. This provides a quantity/quality tradeoff, allowing for the creation of subcatalogs by cutting at specific certainty levels. Selecting for a high level of certainty decreases the sample size, but increases the samples classification accuracy.Comparing the OutcomeTo evaluate the accuracy of the algorithms findings, the authors examined SDSS galaxies that had also been classified by Galaxy Zoo. In particular, they used a 45,000-galaxy subset that consists only of superclean Galaxy Zoo galaxies meaning the human volunteers who categorized them were in agreement at a level of 95% or higher.Number of spiral and elliptical galaxies classified above different certainty levels. Cutting at the 54% certainty level for spirals and 80% for ellipticals leaves ~900,000 and ~600,000 spiral and elliptical galaxies, respectively. [Kuminski et al. 2016]In this set, Kuminski and Shamir found that if they draw a cut-off at the 54% certainty level for spiral galaxies and the 80% certainty level for ellipticals, they find 98% agreement between the computer classification of the galaxies and the human classification via Galaxy Zoo. Applying these cuts to the entire sample resulted in the identification of ~900,000 spiral galaxies and ~600,000 ellipticals, representing the largest catalog of its kind.The authors acknowledge that completeness is a problem; half the data had to be cut to achieve this level of accuracy. Sacrificing some data can still result in very large catalogs, however and as surveys become more powerful and large databases become more prevalent, algorithms such as this one will likely become critical to the scientific process.CitationEvan Kuminski and Lior Shamir 2016 Ap

  3. Adaptive Optics Imaging of Lyman Break Galaxies as Progenitors of Spheroids in the Local Universe

    CERN Document Server

    Akiyama, M; Kobayashi, N; Ohta, K; Iwata, I

    2007-01-01

    In order to reveal the stellar mass distribution of z~3 galaxies, we are conducting deep imaging observations of U-dropout Lyman Break Galaxies (LBGs) with Adaptive Optics (AO) systems in K-band, which corresponds to rest-frame V-band of z~3 galaxies. The results of the Subaru intensive-program observations with AO36/NGS/IRCS indicate that 1) the K-band peaks of some of the LBGs brighter than K=22.0 mag show significant offset from those in the optical images, 2) the z~3 Mv* LBGs and serendipitously observed Distant Red Galaxies (DRGs) have flat profiles similar to disk galaxies in the local universe (i.e., Sersic with n2 systems among the luminous z~3 LBGs and DRGs, and their strong spatial clustering, we infer that the dense n2 spheroids of nearby galaxies through relaxations due to major merger events.

  4. Joint Asymptotic Distributions of Smallest and Largest Insurance Claims

    Directory of Open Access Journals (Sweden)

    Hansjörg Albrecher

    2014-07-01

    Full Text Available Assume that claims in a portfolio of insurance contracts are described by independent and identically distributed random variables with regularly varying tails and occur according to a near mixed Poisson process. We provide a collection of results pertaining to the joint asymptotic Laplace transforms of the normalised sums of the smallest and largest claims, when the length of the considered time interval tends to infinity. The results crucially depend on the value of the tail index of the claim distribution, as well as on the number of largest claims under consideration.

  5. Challenges with the largest commercial hydrogen station in the world

    Energy Technology Data Exchange (ETDEWEB)

    Charbonneau, Thomas; Gauthier, Pierre [Air Liquide Canada (Canada)

    2010-07-01

    This abstract's objective is to share with the participants the story of the largest hydrogen fueling station made to this date and to kick-start the story, we will cover the challenges; first the technical ones; the operational ones; the distribution ones and; the financial ones. We will then move on to review the logistic (geographic) issues raised by the project and conclude our presentation by sharing the output values of the largest fueling station built so far in the world. (orig.)

  6. Largest Common Chemical Feature Subtree as a Virtual Screening Method

    DEFF Research Database (Denmark)

    Kristensen, Thomas Greve; Pedersen, Christian Storm; Thomsen, Rene

    We investigate the effectiveness of using a tree comparison based method to screen for drug candidates. Molecules are represented as trees in which ring systems are reduced to single nodes. These trees are compared to the tree of a selected known binder and the molecules are ranked according...... to the normalized size of their largest common subtree. The nodes of the molecular trees contains information about the atoms or ring systems they represent (e.g. charge and hydrogen donor/acceptor properties). In this way we can restrict which nodes are matched when calculating the size of the largest common...

  7. How Do Galaxies Grow?

    Science.gov (United States)

    2008-08-01

    Astronomers have caught multiple massive galaxies in the act of merging about 4 billion years ago. This discovery, made possible by combining the power of the best ground- and space-based telescopes, uniquely supports the favoured theory of how galaxies form. ESO PR Photo 24/08 ESO PR Photo 24/08 Merging Galaxies in Groups How do galaxies form? The most widely accepted answer to this fundamental question is the model of 'hierarchical formation', a step-wise process in which small galaxies merge to build larger ones. One can think of the galaxies forming in a similar way to how streams merge to form rivers, and how these rivers, in turn, merge to form an even larger river. This theoretical model predicts that massive galaxies grow through many merging events in their lifetime. But when did their cosmological growth spurts finish? When did the most massive galaxies get most of their mass? To answer these questions, astronomers study massive galaxies in clusters, the cosmological equivalent of cities filled with galaxies. "Whether the brightest galaxies in clusters grew substantially in the last few billion years is intensely debated. Our observations show that in this time, these galaxies have increased their mass by 50%," says Kim-Vy Tran from the University of Zürich, Switzerland, who led the research. The astronomers made use of a large ensemble of telescopes and instruments, including ESO's Very Large Telescope (VLT) and the Hubble Space Telescope, to study in great detail galaxies located 4 billion light-years away. These galaxies lie in an extraordinary system made of four galaxy groups that will assemble into a cluster. In particular, the team took images with VIMOS and spectra with FORS2, both instruments on the VLT. From these and other observations, the astronomers could identify a total of 198 galaxies belonging to these four groups. The brightest galaxies in each group contain between 100 and 1000 billion of stars, a property that makes them comparable

  8. Can Black Hole Relax Unitarily?

    Science.gov (United States)

    Solodukhin, S. N.

    2005-03-01

    We review the way the BTZ black hole relaxes back to thermal equilibrium after a small perturbation and how it is seen in the boundary (finite volume) CFT. The unitarity requires the relaxation to be quasi-periodic. It is preserved in the CFT but is not obvious in the case of the semiclassical black hole the relaxation of which is driven by complex quasi-normal modes. We discuss two ways of modifying the semiclassical black hole geometry to maintain unitarity: the (fractal) brick wall and the worm-hole modification. In the latter case the entropy comes out correctly as well.

  9. Can Black Hole Relax Unitarily?

    OpenAIRE

    Solodukhin, Sergey N.

    2004-01-01

    We review the way the BTZ black hole relaxes back to thermal equilibrium after a small perturbation and how it is seen in the boundary (finite volume) CFT. The unitarity requires the relaxation to be quasi-periodic. It is preserved in the CFT but is not obvious in the case of the semiclassical black hole the relaxation of which is driven by complex quasi-normal modes. We discuss two ways of modifying the semiclassical black hole geometry to maintain unitarity: the (fractal) brick wall and the...

  10. Can Black Hole Relax Unitarily?

    CERN Document Server

    Solodukhin, S N

    2004-01-01

    We review the way the BTZ black hole relaxes back to thermal equilibrium after a small perturbation and how it is seen in the boundary (finite volume) CFT. The unitarity requires the relaxation to be quasi-periodic. It is preserved in the CFT but is not obvious in the case of the semiclassical black hole the relaxation of which is driven by complex quasi-normal modes. We discuss two ways of modifying the semiclassical black hole geometry to maintain unitarity: the (fractal) brick wall and the worm-hole modification. In the latter case the entropy comes out correctly as well.

  11. Search for Blue Compact Dwarf Galaxies During Quiescence

    CERN Document Server

    Almeida, J Sanchez; Amorin, R; Aguerri, J A; Sanchez-Janssen, R; Tenorio-Tagle, G

    2008-01-01

    Blue Compact Dwarf (BCD) galaxies are metal poor systems going through a major starburst that cannot last for long. We have identified galaxies which may be BCDs during quiescence (QBCD), i.e., before the characteristic starburst sets in or when it has faded away. These QBCD galaxies are assumed to be like the BCD host galaxies. The SDSS/DR6 database provides ~21500 QBCD candidates. We also select from SDSS/DR6 a complete sample of BCD galaxies to serve as reference. The properties of these two galaxy sets have been computed and compared. The QBCD candidates are thirty times more abundant than the BCDs, with their luminosity functions being very similar except for the scaling factor, and the expected luminosity dimming associated with the end of the starburst. QBCDs are redder than BCDs, and they have larger HII region based oxygen abundance. QBCDs also have lower surface brightness. The BCD candidates turn out to be the QBCD candidates with the largest specific star formation rate (actually, with the largest...

  12. Using Galaxy Winds to Constrain Galaxy Evolution

    Science.gov (United States)

    Churchill, Christopher W.; Klypin, A.; Ceverino, D.; Kacprzak, G.; Klimek, E.

    2010-01-01

    Analysis of mock quasar spectra of metal absorption lines in the proximity of formed galaxies in cosmological simulation is a highly promising for understanding the role of galaxies in IGM physics, or IGM physics in the role of galaxy formation in context of the cosmic web. Such analysis using neutral hydrogen in the cosmic web has literally revolutionized our understanding of the Lyman alpha forest. We are undertaking a wholesale approach to use powerful Lambda-CDM simulations to interpret absorption line data from redshift 1-3 starbursting galaxies e.g. Lyman break galaxies, etc) The data with which direct quantitative comparison is made are from the DEEP survey (Weiner et al.) and the collective work of Steidel et al. and collaborators. The simulations are performed using the Eulerian Gasdynamics plus N-body Adaptive Refinement Tree (ART) code, which has gas cell resolutions of 20-50 pc. Physical processes implemented in the code include realistic radiative cooling, star formation, metal enrichment and thermal feedback due to type II and type Ia supernovae. We quantitatively compare the spatial and kinematic distribution of HI, MgII, CIV, and OVI of absorption lines over a range of impact parameters for various simulated galaxies as a function of redshift, and discuss key insights for interpreting the underlying temperature, density, and ionization structure of the halo/cosmic-web interface, and the influence of galaxies on its chemical enrichment.

  13. Chandra Catches Cannibal Galaxy in the Act

    Science.gov (United States)

    2000-07-01

    NASA's Chandra X-ray Observatory image of Perseus A provides new insight into how this supergiant galaxy has grown by cannibalizing other galaxies and gas in the vicinity. For the first time astronomers see an X-ray shadow cast by a smaller galaxy as its gas is being stripped away by the enormous galaxy. The research was reported by Professor Andrew Fabian of the Institute of Astronomy, Cambridge, England on June 7 at the 196th National Meeting of the American Astronomical Society, in Rochester, NY. Other members of the research team are Jeremy Sanders, Stefano Ettori, Steve Allen, Carolin Crawford, Kazushi Iwasawa, and Roderick Johnstone of the Institute of Astronomy, Gregory Taylor on the National Radio Astronomy Observatory, Socorro, NM, and Patrick Ogle of the Massachusetts Institute of Technology, Cambridge, MA. Perseus A, or NGC 1275, is in the center of a large galaxy cluster 320 million light years from Earth. The cluster, which contains thousands of galaxies and enough gas to make thousands more, is one of the largest gravitationally bound objects in the universe. Over the eons, Perseus A has accumulated hundreds of billions of stars to become one of the most massive known galaxies as gas and galaxies have been pulled inward by gravity. The Chandra observation shows a region of hot gas that extends over several hundred thousand light years. The gas in the outer portion of the cluster has a temperature of 70 million degrees. The cluster gas cools gradually and settles toward the center of the cluster. A galaxy with "only" about 20 billion stars is falling into Perseus A (located at two o'clock from the center of the image) and appears as a small dark patch due to absorption of X rays by cool gas in the infalling galaxy. Another larger hole seen further out is thought to be due to a bubble of high-energy particles ejected in an explosion from Perseus A hundreds of millions of years ago. These outbursts are presumably fueled by matter releasing tremendous

  14. The Chemical Evolution of Narrow Emission Line Galaxies: the Key to their Formation Processes

    CERN Document Server

    Torres-Papaqui, J P; Ortega-Minakata, R A

    2011-01-01

    Using the largest sample of narrow emission line galaxies available so far, we show that their spectral characteristics are correlated with different physical parameters, like the chemical abundances, the morphologies, the masses of the bulge and the mean stellar age of the stellar populations of the host galaxies. It suggests that the spectral variations observed in standard spectroscopic diagnostic diagrams are not due solely to variations of ionization parameters or structures but reflect also the chemical evolution of the galaxies, which in turn can be explained by different galaxy formation processes.

  15. Galaxy clusters and microwave background anisotropy

    CERN Document Server

    Quilis, V; Sáez, D

    1995-01-01

    Previous estimates of the microwave background anisotropies produced by freely falling spherical clusters are discussed. These estimates are based on the Swiss-Cheese and Tolman-Bondi models. It is proved that these models give only upper limits to the anisotropies produced by the observed galaxy clusters. By using spherically symmetric codes including pressureless matter and a hot baryonic gas, new upper limits are obtained. The contributions of the hot gas and the pressureless component to the total anisotropy are compared. The effects produced by the pressure are proved to be negligible; hence, estimations of the cluster anisotropies based on N-body simulations are hereafter justified. After the phenomenon of violent relaxation, any realistic rich cluster can only produce small anisotropies with amplitudes of order 10^{-7}. During the rapid process of violent relaxation, the anisotropies produced by nonlinear clusters are expected to range in the interval (10^{-6},10^{-5}). The angular scales of these anis...

  16. China's Largest Oil Storage Tanks Put into Service

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    @@ Two 125,000-cubic-meter and 90-meter-diameter crude storage tanks, currently largest ones in China,have been constructed and put into service at Sinopec's Maoming Petrochemical Harbor Company in Southeast China's Guangdong Province in recent time.

  17. China Becomes the Second Largest Market for Italian Textile

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    A few days ago, Milano Unica, the Italian Top Textile Fabric Exhibition was held in Beijing. Silvio Albini, President of the Italian textile fabric show, told reporters that China has become the second largest market for Italian textiles, including Hong Kong. Meanwhile, China is a complex fast-growing market with great demand.

  18. Largest Experimental Facility for Acetylene Production in Operation

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ Scientists from the CAS Institute of Plasma Physics (IPP) completed in early November, 2004, a 2-megawatt experimental facility for acetylene production by coal plasma pyrolysis. The successful operation of the largest installation of the kind in the world confirms a new method for the large-scale industrialization of acetylene production.

  19. China’s Largest Copper Foil Factory Opened

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    <正>On October 28,civil engineering and steel structure projects by Nanya No.3 Copper Foil Factory,the largest copper foil factory on the Chinese mainland by Shanghai Baoye Group Corp.,Ltd.,opened on Changjiang Nan Road in Kunshan’s

  20. Kunpeng Copper:The largest Copper Smelting Company of Sichuan

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>On September 9,Liangshan Mining Company’s 100,000 tons/year cathode copper project kicked off.It is another key project of the company following the successful launch of the 100,000 tons/year anode copper project.Based on ISA copper smelting technology of the largest open-cast copper mine in southwest China,

  1. Building Earth's Largest Library: Driving into the Future.

    Science.gov (United States)

    Coffman, Steve

    1999-01-01

    Examines the Amazon.com online bookstore as a blueprint for designing the world's largest library. Topics include selection; accessibility and convenience; quality of Web sites and search tools; personalized service; library collection development, including interlibrary loan; library catalogs and catalog records; a circulation system; costs;…

  2. The Largest Gold Mine in Asia was Found in Gansu

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    <正>Recently,at Yangshan,a place bordering with Shaanxi and Sichuan provinces,of Wen County in Gansu Province,the largest gold mine in Asia was found with proved gold reserve of 308 tons,changing the history of having no super large independent gold deposits over 200 tons in China.

  3. Largest Contract for Rig Export Wound up Successfully

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    @@ In mid-November, the last drilling rig, typed ZJ50DBA,of the 10-rig deal was packed and transported to Uzbekistan from Chuanyou Guanghan Honghua Co Ltd, a drilling equipment producer under Sichuan Petroleum Administration Bureau, putting an end to China's largest contract for export of drilling rigs.

  4. NAFTA: The World's Largest Trading Zone Turns 20

    Science.gov (United States)

    Ferrarini, Tawni Hunt; Day, Stephen

    2014-01-01

    Everyone under the age of 20 who has grown up in North America has lived in the common market created by NAFTA--the North American Free Trade Agreement. In a zone linking the United States, Canada, and Mexico, most goods and investments flow freely across borders to users, consumers, and investors. In 1994, NAFTA created the largest relatively…

  5. World's largest robotic telescope goes into operation at CAS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Lijiang 2.4, one of the world largest fully robotic astronomical telescopes, was put into operation on 12 May at the CAS Yunnan Observatory, the highest of four professional astronomical observatories in China and the only one in the south part of the country.

  6. The Single Largest Education Donor Comes with Controversy

    Science.gov (United States)

    Finkel, Ed

    2012-01-01

    For the last decade, in districts big and small, the Bill & Melinda Gates Foundation has emerged as the largest private funder of educational efforts. This began with an initiative around small schools in the early to mid-2000s, mostly abandoned now, and has gained traction in the past few years in areas such as teacher evaluation, the Common…

  7. Worlds largest particle physics laboratory selects Proxim Wireless Mesh

    CERN Multimedia

    2007-01-01

    "Proxim Wireless has announced that the European Organization for Nuclear Research (CERN), the world's largest particle physics laboratory and the birthplace of the World Wide Web, is using it's ORiNOCO AP-4000 mesh access points to extend the range of the laboratory's Wi-Fi network and to provide continuous monitoring of the lab's calorimeters" (1/2 page)

  8. Analysis of human standing balance by largest lyapunov exponent.

    Science.gov (United States)

    Liu, Kun; Wang, Hongrui; Xiao, Jinzhuang; Taha, Zahari

    2015-01-01

    The purpose of this research is to analyse the relationship between nonlinear dynamic character and individuals' standing balance by the largest Lyapunov exponent, which is regarded as a metric for assessing standing balance. According to previous study, the largest Lyapunov exponent from centre of pressure time series could not well quantify the human balance ability. In this research, two improvements were made. Firstly, an external stimulus was applied to feet in the form of continuous horizontal sinusoidal motion by a moving platform. Secondly, a multiaccelerometer subsystem was adopted. Twenty healthy volunteers participated in this experiment. A new metric, coordinated largest Lyapunov exponent was proposed, which reflected the relationship of body segments by integrating multidimensional largest Lyapunov exponent values. By using this metric in actual standing performance under sinusoidal stimulus, an obvious relationship between the new metric and the actual balance ability was found in the majority of the subjects. These results show that the sinusoidal stimulus can make human balance characteristics more obvious, which is beneficial to assess balance, and balance is determined by the ability of coordinating all body segments.

  9. An Exact Relaxation of Clustering

    DEFF Research Database (Denmark)

    Mørup, Morten; Hansen, Lars Kai

    2009-01-01

    of clustering problems such as the K-means objective and pairwise clustering as well as graph partition problems, e.g., for community detection in complex networks. In particular we show that a relaxation to the simplex can be given for which the extreme solutions are stable hard assignment solutions and vice......Continuous relaxation of hard assignment clustering problems can lead to better solutions than greedy iterative refinement algorithms. However, the validity of existing relaxations is contingent on problem specific fuzzy parameters that quantify the level of similarity between the original...... versa. Based on the new relaxation we derive the SR-clustering algorithm that has the same complexity as traditional greedy iterative refinement algorithms but leading to significantly better partitions of the data. A Matlab implementation of the SR-clustering algorithm is available for download....

  10. The relaxation & stress reduction workbook

    National Research Council Canada - National Science Library

    Davis, Martha; Eshelman, Elizabeth Robbins; McKay, Matthew

    2008-01-01

    "The Relaxation & Stress Reduction Workbook broke new ground when it was first published in 1980, detailing easy, step-by-step techniques for calming the body and mind in an increasingly overstimulated world...

  11. Relaxation Dynamics in Heme Proteins.

    Science.gov (United States)

    Scholl, Reinhard Wilhelm

    A protein molecule possesses many conformational substates that are likely arranged in a hierarchy consisting of a number of tiers. A hierarchical organization of conformational substates is expected to give rise to a multitude of nonequilibrium relaxation phenomena. If the temperature is lowered, transitions between substates of higher tiers are frozen out, and relaxation processes characteristic of lower tiers will dominate the observational time scale. This thesis addresses the following questions: (i) What is the energy landscape of a protein? How does the landscape depend on the environment such as pH and viscosity, and how can it be connected to specific structural parts? (ii) What relaxation phenomena can be observed in a protein? Which are protein specific, and which occur in other proteins? How does the environment influence relaxations? (iii) What functional form best describes relaxation functions? (iv) Can we connect the motions to specific structural parts of the protein molecule, and are these motions important for the function of the protein?. To this purpose, relaxation processes after a pressure change are studied in carbonmonoxy (CO) heme proteins (myoglobin-CO, substrate-bound and substrate-free cytochrome P450cam-CO, chloroperoxidase-CO, horseradish peroxidase -CO) between 150 K and 250 K using FTIR spectroscopy to monitor the CO bound to the heme iron. Two types of p -relaxation experiments are performed: p-release (200 to ~eq40 MPa) and p-jump (~eq40 to 200 MPa) experiments. Most of the relaxations fall into one of three groups and are characterized by (i) nonexponential time dependence and non-Arrhenius temperature dependence (FIM1( nu), FIM1(Gamma)); (ii) exponential time dependence and non-Arrhenius temperature dependence (FIM0(A_{i}to A_{j})); exponential time dependence and Arrhenius temperature dependence (FIMX( nu)). The influence of pH is studied in myoglobin-CO and shown to have a strong influence on the substate population of the

  12. XMM Observations of Metal Abundances in Galaxy Clusters

    Directory of Open Access Journals (Sweden)

    L. Lovisari

    2011-01-01

    Full Text Available The hot gas that fills the space between galaxies in clusters is rich in metals. Due to their large potential well, galaxy clusters accumulate metals over the whole history of the cluster, and retain important information on cluster formation and evolution.We derive detailed metallicity maps for a sample of 5 clusters, observed with XMM-Newton, to study the distribution of metals in the Intra-Cluster Medium (ICM. We show that even in relaxed clusters the distribution of metals shows many inhomogeneities with several maxima separated by low metallicity regions. We also found a deviation from the expected temperature-metallicity relation.

  13. Negative magnetic relaxation in superconductors

    Directory of Open Access Journals (Sweden)

    Krasnoperov E.P.

    2013-01-01

    Full Text Available It was observed that the trapped magnetic moment of HTS tablets or annuli increases in time (negative relaxation if they are not completely magnetized by a pulsed magnetic field. It is shown, in the framework of the Bean critical-state model, that the radial temperature gradient appearing in tablets or annuli during a pulsed field magnetization can explain the negative magnetic relaxation in the superconductor.

  14. The Stripe 82 Massive Galaxy Project I: Catalog Construction

    CERN Document Server

    Bundy, Kevin; Saito, Shun; Bolton, Adam; Lin, Yen-Ting; Marason, Claudia; Nichol, Robert C; Schneider, Donald P; Thomas, Daniel; Wake, David A

    2015-01-01

    The Stripe 82 Massive Galaxy Catalog (S82-MGC) is the largest-volume stellar mass-limited sample of galaxies beyond z~1 constructed to date. Spanning 139.4 deg2, the S82-MGC includes a mass-limited sample of 41,770 galaxies with log Mstar > 11.2 to z~0.7, sampling a volume of 0.3 Gpc3, roughly equivalent to the volume of the Sloan Digital Sky Survey-I/II (SDSS-I/II) z 11.2 sample, and geometric masking. We provide near-IR based stellar mass estimates and compare these to previous estimates. All catalog products are made publicly available. The S82-MGC not only addresses previous statistical limitations in high-mass galaxy evolution studies but begins tackling inherent data challenges in the coming era of wide-field imaging surveys.

  15. Dark-ages Reionization & Galaxy Formation Simulation I: The dynamical lives of high redshift galaxies

    CERN Document Server

    Poole, Gregory B; Mutch, Simon J; Power, Chris; Duffy, Alan R; Geil, Paul M; Mesinger, Andrei; Wyithe, Stuart B

    2015-01-01

    We present the Dark-ages Reionization and Galaxy-formation Observables from Numerical Simulations (DRAGONS) program and Tiamat, the collisionless N-body simulation program upon which DRAGONS is built. The primary trait distinguishing Tiamat from other large simulation programs is its density of outputs at high redshift (100 from z=35 to z=5; roughly one every 10 Myr) enabling the construction of very accurate merger trees at an epoch when galaxy formation is rapid and mergers extremely frequent. We find that the friends-of-friends halo mass function agrees well with the prediction of Watson et al. at high masses, but deviates at low masses, perhaps due to our use of a different halo finder or perhaps indicating a break from "universal" behaviour. We then analyse the dynamical evolution of galaxies during the Epoch of Reionization finding that only a small fraction (~20%) of galactic halos are relaxed. We illustrate this using standard relaxation metrics to establish two dynamical recovery time-scales: i) halo...

  16. The formation and assembly of a typical star-forming galaxy at redshift z approximately 3.

    Science.gov (United States)

    Stark, Daniel P; Swinbank, A Mark; Ellis, Richard S; Dye, Simon; Smail, Ian R; Richard, Johan

    2008-10-09

    Recent studies of galaxies approximately 2-3 Gyr after the Big Bang have revealed large, rotating disks, similar to those of galaxies today. The existence of well-ordered rotation in galaxies during this peak epoch of cosmic star formation indicates that gas accretion is likely to be the dominant mode by which galaxies grow, because major mergers of galaxies would completely disrupt the observed velocity fields. But poor spatial resolution and sensitivity have hampered this interpretation; such studies have been limited to the largest and most luminous galaxies, which may have fundamentally different modes of assembly from those of more typical galaxies (which are thought to grow into the spheroidal components at the centres of galaxies similar to the Milky Way). Here we report observations of a typical star-forming galaxy at z = 3.07, with a linear resolution of approximately 100 parsecs. We find a well-ordered compact source in which molecular gas is being converted efficiently into stars, likely to be assembling a spheroidal bulge similar to those seen in spiral galaxies at the present day. The presence of undisrupted rotation may indicate that galaxies such as the Milky Way gain much of their mass by accretion rather than major mergers.

  17. Galaxy Formation Theory

    CERN Document Server

    Benson, Andrew J

    2010-01-01

    We review the current theory of how galaxies form within the cosmological framework provided by the cold dark matter paradigm for structure formation. Beginning with the pre-galactic evolution of baryonic material we describe the analytical and numerical understanding of how baryons condense into galaxies, what determines the structure of those galaxies and how internal and external processes (including star formation, merging, active galactic nuclei etc.) determine their gross properties and evolution. Throughout, we highlight successes and failings of current galaxy formation theory. We include a review of computational implementations of galaxy formation theory and assess their ability to provide reliable modeling of this complex phenomenon. We finish with a discussion of several "hot topics" in contemporary galaxy formation theory and assess future directions for this field.

  18. The Stuff Between Galaxies

    Institute of Scientific and Technical Information of China (English)

    1995-01-01

    The space between stars in our galaxy,astronomers know, is sprinkled with a diffuse mixture of gas and dust.But what about the immense starless reaches separating galaxies? In the 1960s astronomers discovered isolated, galaxy-size clouds of hydrogen out there.Now an observation made by the repaired Hubble Space Telescope has revealed that intergalactic space is also permeated by a thin fog of ionized helium.

  19. From nearby to distant galaxies: kinematical and dynamical studies

    CERN Document Server

    Epinat, Benoit

    2009-01-01

    Kinematical studies of low and high redshift galaxies enables to probe galaxy formation and evolution scenarios. Integral field spectroscopy is a powerful tool to study with accuracy nearby galaxies kinematics. Recent observations also gives a new 2D vision of high redshift galaxies kinematics. This work mostly relies on the kinematical sample of galaxies GHASP. This control sample, composed of 203 local spiral and irregular galaxies in low density environments observed with Fabry-Perot techniques in the Ha line (6563 A), is by now the largest sample of Fabry-Perot data. After a revue on Fabry-Perot interferometry and a presentation of new data reduction procedures, my implications on both 3D-NTT Fabry-Perot instrument and the wide field spectrograph project (WFSpec) for galaxy evolution study with the european ELT are developed. The second section is dedicated to GHASP data. This sample have been fully reduced and analysed using new methods. The kinematical analysis of 2D kinematical maps has been undertaken...

  20. Ultraluminous infrared galaxies in the AKARI all-sky survey

    Energy Technology Data Exchange (ETDEWEB)

    Kilerci Eser, E., E-mail: ecekilerci@dark-cosmology.dk [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø (Denmark); Goto, T. [National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan (China); Doi, Y., E-mail: tomo@phys.nthu.edu.tw, E-mail: doi@ea.c.u-tokyo.ac.jp [The University of Tokyo, Komaba 3-8-1, Meguro, Tokyo 153-8902 (Japan)

    2014-12-10

    We present a new catalog of 118 ultraluminous infrared galaxies (ULIRGs) and one hyperluminous infrared galaxy (HLIRG) by cross-matching the AKARI all-sky survey with the Sloan Digital Sky Survey Data Release 10 (SDSS DR10) and the final data release of the Two-Degree Field Galaxy Redshift Survey. Forty of the ULIRGs and one HLIRG are new identifications. We find that ULIRGs are interacting pair galaxies or ongoing or postmergers. This is consistent with the widely accepted view: ULIRGs are major mergers of disk galaxies. We confirm the previously known positive trend between the active galactic nucleus fraction and infrared luminosity. We show that ULIRGs have a large offset from the main sequence up to z ∼ 1; their offset from the z ∼ 2 'main sequence' is relatively smaller. We find a result consistent with the previous studies showing that, compared to local star-forming SDSS galaxies of similar mass, local ULIRGs have lower oxygen abundances. We demonstrate for the first time that ULIRGs follow the fundamental metallicity relation (FMR). The scatter of ULIRGs around the FMR (0.09 dex-0.5 dex) is comparable to the scatter of z ∼ 2-3 galaxies. We provide the largest local (0.050

  1. An Elegant Galaxy in an Unusual Light

    Science.gov (United States)

    2010-09-01

    , where astronomers have found evidence for the presence of a super-massive black hole, well hidden among myriads of intensely bright new stars. NGC 1365, including its two huge outer spiral arms, spreads over around 200 000 light-years. Different parts of the galaxy take different times to make a full rotation around the core of the galaxy, with the outer parts of the bar completing one circuit in about 350 million years. NGC 1365 and other galaxies of its type have come to more prominence in recent years with new observations indicating that the Milky Way could also be a barred spiral galaxy. Such galaxies are quite common - two thirds of spiral galaxies are barred according to recent estimates, and studying others can help astronomers understand our own galactic home. More information ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

  2. Worlds Largest Wave Energy Project 2007 in Wales

    DEFF Research Database (Denmark)

    Christensen, Lars; Friis-Madsen, Erik; Kofoed, Jens Peter

    2006-01-01

    a large number of fundamentally different technologies are utilised to harvest wave energy. The Wave Dragon belongs to the wave overtopping class of converters and the paper describes the fundamentals and the technical solutions used in this wave energy converter. An offshore floating WEC like the Wave......This paper introduces world largest wave energy project being developed in Wales and based on one of the leading wave energy technologies. The background for the development of wave energy, the total resource ands its distribution around the world is described. In contrast to wind energy turbines...... Dragon has to be scaled in accordance with the wave climate at the deployment site, which makes the Welch demonstrator device the worlds largest WEC so far with a total width of 300 meters. The project budget, the construction methods and the deployment site are also given....

  3. Temporal properties of seismicity and largest earthquakes in SE Carpathians

    Directory of Open Access Journals (Sweden)

    S. Byrdina

    2006-01-01

    Full Text Available In order to estimate the hazard rate distribution of the largest seismic events in Vrancea, South-Eastern Carpathians, we study temporal properties of historical and instrumental catalogues of seismicity. First, on the basis of Generalized Extreme Value theory we estimate the average return period of the largest events. Then, following Bak et al. (2002 and Corral (2005a, we study scaling properties of recurrence times between earthquakes in appropriate spatial volumes. We come to the conclusion that the seismicity is temporally clustered, and that the distribution of recurrence times is significantly different from a Poisson process even for times largely exceeding corresponding periods of foreshock and aftershock activity. Modeling the recurrence times by a gamma distributed variable, we finally estimate hazard rates with respect to the time elapsed from the last large earthquake.

  4. The dark matter of galaxy voids

    CERN Document Server

    Sutter, P M; Wandelt, Benjamin D; Weinberg, David H; Warren, Michael S

    2013-01-01

    How do observed voids relate to the underlying dark matter distribution? To examine the spatial distribution of dark matter contained within voids identified in galaxy surveys, we apply Halo Occupation Distribution models representing sparsely and densely sampled galaxy surveys to a high-resolution N-body simulation. We compare these galaxy voids to voids found in the halo distribution, low-resolution dark matter, and high-resolution dark matter. We find that voids at all scales in densely sampled surveys - and medium- to large-scale voids in sparse surveys - trace the same underdensities as dark matter, but they are larger in radius by ~20%, they have somewhat shallower density profiles, and they have centers offset by ~0.4Rv rms. However, in void-to-void comparison we find that shape estimators are less robust to sampling, and the largest voids in sparsely sampled surveys suffer fragmentation at their edges. We find that voids in galaxy surveys always correspond to underdensities in the dark matter, though ...

  5. Jilin Chemical Fiber Group Launches Its Largest Carbon Fiber Preject

    Institute of Scientific and Technical Information of China (English)

    Flora

    2011-01-01

    China's carbon fiber precursor production line with 5,000 tons of annual output was put into operation in Jilin Chemical Fiber Group on November 18th this year, creating the maximum production capacity currently in China, for which Jilin Chemical Fiber Group become China's largest carbon fiber precursor production base, The smooth operation of the project has laid a solid foundation for promoting China's carbon fiber industry steady, rapid, and healthy development,

  6. BGP Started Shooting Its Largest Oversea Seismic Survey

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ At 5 a.m. on November 1, 2005 of Beijing time, BGP (Bureau of Geophysical Prospecting)formally began shooting the S-51 3D seismic acquisition project in Saudi Arabia, its largest oversea seismic survey project to date. At the same time, the SRAK 2D seismic survey project was also started in the country. These two projects mark the construction of BGP's another large oversea production base.

  7. A local Echo State Property through the largest Lyapunov exponent.

    Science.gov (United States)

    Wainrib, Gilles; Galtier, Mathieu N

    2016-04-01

    Echo State Networks are efficient time-series predictors, which highly depend on the value of the spectral radius of the reservoir connectivity matrix. Based on recent results on the mean field theory of driven random recurrent neural networks, enabling the computation of the largest Lyapunov exponent of an ESN, we develop a cheap algorithm to establish a local and operational version of the Echo State Property.

  8. On Galaxies and Homology

    OpenAIRE

    Novak, Gregory S.; Jonsson, Patrik; Primack, Joel R.; Cox, Thomas J.; Dekel, Avishai

    2012-01-01

    The definition of homology for single-component galaxies is clear, but for multi-component (luminous and dark matter) galaxies there is some ambiguity. We attempt to clarify the situation by carefully separating the different concepts of homology that have been used to date. We argue that the most useful definition is that a set of galaxies is homologous if they are the same in all respects up to a set of three dimensional scaling constants which may differ from one galaxy to the next. Noting...

  9. Largest Empty Circle Centered on a Query Line

    CERN Document Server

    Augustine, John; Roy, Sasanka

    2008-01-01

    The Largest Empty Circle problem seeks the largest circle centered within the convex hull of a set $P$ of $n$ points in $\\mathbb{R}^2$ and devoid of points from $P$. In this paper, we introduce a query version of this well-studied problem. In our query version, we are required to preprocess $P$ so that when given a query line $Q$, we can quickly compute the largest empty circle centered at some point on $Q$ and within the convex hull of $P$. We present solutions for two special cases and the general case; all our queries run in $O(\\log n)$ time. We restrict the query line to be horizontal in the first special case, which we preprocess in $O(n \\alpha(n) \\log n)$ time and space, where $\\alpha(n)$ is the slow growing inverse of the Ackermann's function. When the query line is restricted to pass through a fixed point, the second special case, our preprocessing takes $O(n \\alpha(n)^{O(\\alpha(n))} \\log n)$ time and space. We use insights from the two special cases to solve the general version of the problem with pr...

  10. What is the largest Einstein radius in the universe?

    CERN Document Server

    Oguri, Masamune

    2008-01-01

    The Einstein radius plays a central role in lens studies as it characterises the strength of gravitational lensing. The distribution of Einstein radii near the upper cutoff should probe the largest mass concentrations in the universe. Adopting a triaxial halo model, we compute expected distributions of large Einstein radii. To assess the cosmic variance, we generate a number of all-sky Monte-Carlo realisations. We find that the expected largest Einstein radius in the universe is sensitive to the cosmological model: for a source redshift z=1, they are 42^{+9}_{-7}, 35^{+8}_{-6}, and 54^{+12}_{-7} arcseconds, assuming best-fit parameters of the WMAP5, WMAP3 and WMAP1 data, respectively. These values are broadly consistent with current observations given their incompleteness. For the same source redshift, we expect in all-sky 35 (WMAP5), 15 (WMAP3), and 150 (WMAP1) clusters that have Einstein radii larger than 20''. Whilst the values of the largest Einstein radii are almost unaffected by the primordial non-Gauss...

  11. Finding largest small polygons with GloptiPoly

    CERN Document Server

    Henrion, Didier

    2011-01-01

    A small polygon is a convex polygon of unit diameter. We are interested in small polygons which have the largest area for a given number of vertices $n$. Many instances are already solved in the literature, namely for all odd $n$, and for $n=4, 6$ and 8. Thus, for even $n\\geq 10$, instances of this problem remain open. Finding those largest small polygons can be formulated as nonconvex quadratic programming problems which can challenge state-of-the-art global optimization algorithms. We show that a recently developed technique for global polynomial optimization, based on a semidefinite programming approach to the generalized problem of moments and implemented in the public-domain Matlab package GloptiPoly, can successfully find largest small polygons for $n=10$ and $n=12$. Therefore this significantly improves existing results in the domain. When coupled with accurate convex conic solvers, GloptiPoly can provide numerical guarantees of global optimality, as well as rigorous guarantees relying on interval arit...

  12. Evolution of growing black holes in axisymmetric galaxy cores

    CERN Document Server

    Fiestas, Jose; Berczik, Peter; Spurzem, Rainer

    2011-01-01

    NBody realizations of axisymmetric collisional galaxy cores (e.g. M32, M33, NGC205, Milky Way) with embedded growing black holes are presented. Stars which approach the disruption sphere are disrupted and accreted to the black hole. We measure the zone of influence of the black hole and disruption rates in relaxation time scales. We show that secular gravitational instabilities dominate the initial core dynamics, while the black hole is small and growing due to consumption of stars. Later, the black hole potential dominates the core, and loss cone theory can be applied. Our simulations show that central rotation in galaxies can not be neglected for relaxed systems, and compare and discuss our results with the standard theory of spherically symmetric systems.

  13. A GMBCG galaxy cluster catalog of 55,880 rich clusters from SDSS DR7

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Jiangang; McKay, Timothy A.; Koester, Benjamin P.; Rykoff, Eli S.; Rozo, Eduardo; Annis, James; Wechsler, Risa H.; Evrard, August; Siegel, Seth R.; Becker, Matthew; Busha, Michael; /Fermilab /Michigan U. /Chicago U., Astron. Astrophys. Ctr. /UC, Santa Barbara /KICP, Chicago /KIPAC, Menlo Park /SLAC /Caltech /Brookhaven

    2010-08-01

    We present a large catalog of optically selected galaxy clusters from the application of a new Gaussian Mixture Brightest Cluster Galaxy (GMBCG) algorithm to SDSS Data Release 7 data. The algorithm detects clusters by identifying the red sequence plus Brightest Cluster Galaxy (BCG) feature, which is unique for galaxy clusters and does not exist among field galaxies. Red sequence clustering in color space is detected using an Error Corrected Gaussian Mixture Model. We run GMBCG on 8240 square degrees of photometric data from SDSS DR7 to assemble the largest ever optical galaxy cluster catalog, consisting of over 55,000 rich clusters across the redshift range from 0.1 < z < 0.55. We present Monte Carlo tests of completeness and purity and perform cross-matching with X-ray clusters and with the maxBCG sample at low redshift. These tests indicate high completeness and purity across the full redshift range for clusters with 15 or more members.

  14. A GMBCG Galaxy Cluster Catalog of 55,424 Rich Clusters from SDSS DR7

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Jiangang; /Fermilab; McKay, Timothy A.; /Michigan U.; Koester, Benjamin P.; /Chicago U.; Rykoff, Eli S.; /UC, Santa Barbara /LBL, Berkeley; Rozo, Eduardo; /Chicago U.; Annis, James; /Fermilab; Wechsler, Risa H.; /SLAC; Evrard, August; /Michigan U.; Siegel, Seth R.; /Michigan U.; Becker, Matthew; /Chicago U.; Busha, Michael; /SLAC; Gerdes, David; /Michigan U.; Johnston, David E.; /Fermilab; Sheldon, Erin; /Brookhaven

    2011-08-22

    We present a large catalog of optically selected galaxy clusters from the application of a new Gaussian Mixture Brightest Cluster Galaxy (GMBCG) algorithm to SDSS Data Release 7 data. The algorithm detects clusters by identifying the red sequence plus Brightest Cluster Galaxy (BCG) feature, which is unique for galaxy clusters and does not exist among field galaxies. Red sequence clustering in color space is detected using an Error Corrected Gaussian Mixture Model. We run GMBCG on 8240 square degrees of photometric data from SDSS DR7 to assemble the largest ever optical galaxy cluster catalog, consisting of over 55,000 rich clusters across the redshift range from 0.1 < z < 0.55. We present Monte Carlo tests of completeness and purity and perform cross-matching with X-ray clusters and with the maxBCG sample at low redshift. These tests indicate high completeness and purity across the full redshift range for clusters with 15 or more members.

  15. What Is the Largest Einstein Radius in the Universe?

    Energy Technology Data Exchange (ETDEWEB)

    Oguri, Masamune; Blandford, Roger D.

    2008-08-05

    The Einstein radius plays a central role in lens studies as it characterizes the strength of gravitational lensing. In particular, the distribution of Einstein radii near the upper cutoff should probe the probability distribution of the largest mass concentrations in the universe. Adopting a triaxial halo model, we compute expected distributions of large Einstein radii. To assess the cosmic variance, we generate a number of Monte-Carlo realizations of all-sky catalogues of massive clusters. We find that the expected largest Einstein radius in the universe is sensitive to parameters characterizing the cosmological model, especially {sigma}{sub s}: for a source redshift of unity, they are 42{sub -7}{sup +9}, 35{sub -6}{sup +8}, and 54{sub -7}{sup +12} arcseconds (errors denote 1{sigma} cosmic variance), assuming best-fit cosmological parameters of the Wilkinson Microwave Anisotropy Probe five-year (WMAP5), three-year (WMAP3) and one-year (WMAP1) data, respectively. These values are broadly consistent with current observations given their incompleteness. The mass of the largest lens cluster can be as small as {approx} 10{sup 15} M{sub {circle_dot}}. For the same source redshift, we expect in all-sky {approx} 35 (WMAP5), {approx} 15 (WMAP3), and {approx} 150 (WMAP1) clusters that have Einstein radii larger than 2000. For a larger source redshift of 7, the largest Einstein radii grow approximately twice as large. While the values of the largest Einstein radii are almost unaffected by the level of the primordial non-Gaussianity currently of interest, the measurement of the abundance of moderately large lens clusters should probe non-Gaussianity competitively with cosmic microwave background experiments, but only if other cosmological parameters are well-measured. These semi-analytic predictions are based on a rather simple representation of clusters, and hence calibrating them with N-body simulations will help to improve the accuracy. We also find that these &apos

  16. The effects of assembly bias on cosmological inference from galaxy-galaxy lensing and galaxy clusters

    CERN Document Server

    McEwen, Joseph E

    2016-01-01

    The combination of galaxy-galaxy lensing (GGL) and galaxy clustering is a promising route to measuring the amplitude of matter clustering and testing modified gravity theories of cosmic acceleration. Halo occupation distribution (HOD) modeling can extend the approach down to nonlinear scales, but galaxy assembly bias could introduce systematic errors by causing the HOD to vary with large scale environment at fixed halo mass. We investigate this problem using the mock galaxy catalogs created by Hearin & Watson (2013, HW13), which exhibit significant assembly bias because galaxy luminosity is tied to halo peak circular velocity and galaxy colour is tied to halo formation time. The preferential placement of galaxies (especially red galaxies) in older halos affects the cutoff of the mean occupation function $\\langle N_\\text{cen}(M_\\text{min}) \\rangle$ for central galaxies, with halos in overdense regions more likely to host galaxies. The effect of assembly bias on the satellite galaxy HOD is minimal. We intro...

  17. Watching the Birth of a Galaxy Cluster?

    Science.gov (United States)

    1999-07-01

    ,000 light-years (280 x 200 kpc). The linear scale is indicated at the lower left. North is up and East is left. The Leiden astronomers used the FORS1 instrument on ANTU to take long-exposure pictures of 1138-262 and a surrounding field of 36 square arcmin. Images were obtained through two optical filters, one which tunes in to light produced by hydrogen gas (the redshifted Lyman-alpha line) and the other which is dominated by light from stars (the B-band). The "difference" between the images shows that the hydrogen gas surrounding the galaxy and from which the galaxy is presumably forming is huge ( Photo 33a/99 ). The measured size is about 20 arcsec or, at the distance of the cluster, somewhat more than 500,000 light-years (160 kpc), making it the largest such structure ever seen. It corresponds to about 5 times the size of the optical extent of the Milky Way Galaxy ! ESO PR Photo 33b/99 ESO PR Photo 33b/99 [Preview - JPEG: 400 x 593 pix - 149k] [Normal - JPEG: 800 x 1185 pix - 335k] [High-Res - JPEG: 1982 x 2935 pix - 1.1M] Caption to ESO PR Photo 33b/99 : Three small fields near radio galaxy 1138-262 as observed with VLT ANTU + FORS1 in a narrow-band filter at the redshifted wavelength of Lyman-alpha emission in that galaxy (left) and a broader filter in the surrounding spectral region (right), respectively. Three excellent candidates of Lyman-alpha emitters are seen at the centres of the fields. They are clearly visible in the narrow-band image (that mostly shows the gas), but are not detected in the broad-band image (that mostly shows the stars). Each field measures 24 x 24 arcsec 2 , corresponding to about 620,000 x 620,000 light-years (190 x 190 kpc); North is up and East is left. Even more intriguing is the presence of a number of objects in the gas picture (to the left in PR Photo 33b/99 ), but absent from the stars' picture (right). These are galaxies whose hydrogen gas is emitting the bright Lyman-alpha spectral line within a distance of the order of about 3

  18. Hyperactive galaxy NGC 7673 [heic0205

    Science.gov (United States)

    2002-03-01

    Hyperactive galaxy NGC 7673 hi-res Size hi-res: 116 kb Credits: European Space Agency & Nicole Homeier (European Southern Observatory and University of Wisconsin-Madison) Hyperactive galaxy NGC 7673 The disturbed spiral galaxy NGC 7673 is ablaze with the light from millions of new stars. Each of its infant giant blue star clusters shines 100 times as brightly in the ultraviolet as similar immense star clusters in our own Galaxy. Scientists studying this object have two pressing questions: "What has triggered this enormous burst of star formation and how will this galaxy evolve in the future?" Telltale patches of blue light are signs of the formation of millions of new stars in the tangled spiral galaxy NGC 7673. Each of the bluish areas in this image consists of immense star clusters containing thousands of young stars. These clusters lie on the spiral arms of NGC 7673 and so emphasise its somewhat ragged look. This image, taken from Earth orbit by the ESA/NASA Hubble Space Telescope in 1996 and 1997, also shows two other galaxies seen in the background of the image, to the left and right of NGC 7673. These galaxies are further away and so appear redder, due to their higher redshift, an effect caused by the expansion of the Universe. The youngest blue stars in NGC 7673 are blazing with intense ultraviolet radiation. Each star cluster radiates 100 times more ultraviolet light than the famous Tarantula Nebula (30 Doradus), the largest star-forming region known in the local group of galaxies. Telltale patches of blue light are signs of the formation of millions of new stars in the tangled spiral galaxy NGC 7673. Each of the bluish areas in this image consists of immense star clusters containing thousands of young stars. These clusters lie on the spiral arms of NGC 7673 and so emphasise its somewhat ragged look. This image, taken from Earth orbit by the ESA/NASA Hubble Space Telescope in 1996 and 1997, also shows two other galaxies seen in the background of the image

  19. Dynamical theory of spin relaxation

    Science.gov (United States)

    Field, Timothy R.; Bain, Alex D.

    2013-02-01

    The dynamics of a spin system is usually calculated using the density matrix. However, the usual formulation in terms of the density matrix predicts that the signal will decay to zero, and does not address the issue of individual spin dynamics. Using stochastic calculus, we develop a dynamical theory of spin relaxation, the origins of which lie in the component spin fluctuations. This entails consideration of random pure states for individual protons, and how these pure states are correctly combined when the density matrix is formulated. Both the lattice and the spins are treated quantum mechanically. Such treatment incorporates both the processes of spin-spin and (finite temperature) spin-lattice relaxation. Our results reveal the intimate connections between spin noise and conventional spin relaxation.

  20. The connection between galaxy environment and the luminosity function slopes of star-forming regions

    Science.gov (United States)

    Cook, David O.; Dale, Daniel A.; Lee, Janice C.; Thilker, David; Calzetti, Daniela; Kennicutt, Robert C.

    2016-11-01

    We present the first study of GALEX far-ultraviolet (FUV) luminosity functions of individual star-forming regions within a sample of 258 nearby galaxies spanning a large range in total stellar mass and star formation properties. We identify ˜65 000 star-forming regions (i.e. FUV sources), measure each galaxy's luminosity function, and characterize the relationships between the luminosity function slope (α) and several global galaxy properties. A final sample of 82 galaxies with reliable luminosity functions are used to define these relationships and represent the largest sample of galaxies with the largest range of galaxy properties used to study the connection between luminosity function properties and galaxy environment. We find that α correlates with global star formation properties, where galaxies with higher star formation rates and star formation rate densities (ΣSFR) tend to have flatter luminosity function slopes. In addition, we find that neither stochastic sampling of the luminosity function in galaxies with low-number statistics nor the effects of blending due to distance can fully account for these trends. We hypothesize that the flatter slopes in high ΣSFR galaxies is due to higher gas densities and higher star formation efficiencies which result in proportionally greater numbers of bright star-forming regions. Finally, we create a composite luminosity function composed of star-forming regions from many galaxies and find a break in the luminosity function at brighter luminosities. However, we find that this break is an artefact of varying detection limits for galaxies at different distances.

  1. A mixed relaxed clock model

    Science.gov (United States)

    2016-01-01

    Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325829

  2. A search for the most massive galaxies: double trouble?

    Energy Technology Data Exchange (ETDEWEB)

    Bernardi, Mariangela; Sheth, R.K.; /Pennsylvania U.; Nichol, R.C.; /Portsmouth U., ICG; Miller, C.J.; /Cerro-Tololo InterAmerican Obs.; Schlegel, D.; /Princeton U. Observ.; Frieman, J.; /Chicago U., Astron. Astrophys. Ctr. /Fermilab; Schneider, D.P.; /Penn State U., Astron. Astrophys.; Subbarao, M.; York, D.G.; /Chicago U., Astron. Astrophys. Ctr.; Brinkmann, J.; /Apache Point Observ.

    2005-10-01

    We describe the results of a search for galaxies with large ({approx}> 350 kms{sup -1}) velocity dispersions. The largest systems we have found appear to be the extremes of the early-type galaxy population: compared to other galaxies with similar luminosities, they have the largest velocity dispersions and the smallest sizes. However, they are not distant outliers from the Fundamental Plane and mass-to-light scaling relations defined by the bulk of the early-type galaxy population. They may host the most massive black holes in the Universe, and their abundance and properties can be used to constrain galaxy formation models. Clear outliers from the scaling relations tend to be objects in superposition (angular separations smaller than 1 arcsec), evidence for which comes sometimes from the spectra, sometimes from the images, and sometimes from both. The statistical properties of the superposed pairs, e.g., the distribution of pair separations and velocity dispersions, can be used to provide useful information about the expected distribution of image multiplicities, separations and flux ratios due to gravitational lensing by multiple lenses, and may also constrain models of their interaction rates.

  3. LAVENDER AROMATERAPHY AS A RELAXANT

    Directory of Open Access Journals (Sweden)

    IGA Prima Dewi AP

    2013-02-01

    Full Text Available Aromatherapy is a kind of treatment that used aroma with aromatherapy essential oil. Extraction process from essential oil generally doing in three methods, there are distilling with water (boiled, distilling with water and steam, and distilling with steam. One of the most favorite aroma is lavender. The main content from lavender is linalyl acetate and linalool (C10H18O. Linalool is main active contents in lavender which can use for anti-anxiety (relaxation. Based on some research, the conclusion indicates that essential oil from lavender can give relaxation (carminative, sedative, reduce anxiety level and increasing mood.

  4. Active optomechanics through relaxation oscillations

    CERN Document Server

    Princepe, Debora; Frateschi, Newton

    2014-01-01

    We propose an optomechanical laser based on III-V compounds which exhibits self-pulsation in the presence of a dissipative optomechanical coupling. In such a laser cavity, radiation pressure drives the mechanical degree of freedom and its back-action is caused by the mechanical modulation of the cavity loss rate. Our numerical analysis shows that even in a wideband gain material, such dissipative coupling couples the mechanical oscillation with the laser relaxation oscillations process. Laser self-pulsation is observed for mechanical frequencies below the laser relaxation oscillation frequency under sufficiently high optomechanical coupling factor.

  5. Thermal relaxation and mechanical relaxation of rice gel

    Institute of Scientific and Technical Information of China (English)

    丁玉琴; 赵思明; 熊善柏

    2008-01-01

    Rice gel was prepared by simulating the production processes of Chinese local rice noodles,and the properties of thermal relaxation and mechanical relaxation during gelatinization were studied by differential scanning calorimetry(DSC) measurement and dynamic rheometer.The results show that during gelatinization,the molecular chains of rice starch undergo the thermal relaxation and mechanical relaxation.During the first heating and high temperature holding processes,the starch crystallites in the rice slurry melt,and the polymer chains stretch and interact,then viscoelastic gel forms.The cooling and low temperatures holding processes result in reinforced networks and decrease the viscoelasticity of the gel.During the second heating,the remaining starch crystallites further melt,the network is reinforced,and the viscoelasticity increases.The viscoelasticity,the molecular conformation and texture of the gel are adjusted by changing the temperature,and finally construct the gel with the textural characteristics of Chinese local rice noodle.

  6. CLASH-VLT: Substructure in the galaxy cluster MACS J1206.2-0847 from kinematics of galaxy populations

    CERN Document Server

    Girardi, M; Balestra, I; Nonino, M; Biviano, A; Grillo, C; Rosati, P; Annunziatella, M; Demarco, R; Fritz, A; Gobat, R; Lemze, D; Presotto, V; Scodeggio, M; Tozzi, P; Caminha, G Bartosch; Brescia, M; Coe, D; Kelson, D; Koekemoer, A; Lombardi, M; Medezinski, E; Postman, M; Sartoris, B; Umetsu, K; Zitrin, A; Boschin, W; Czoske, O; De Lucia, G; Kuchner, U; Maier, C; Meneghetti, M; Monaco, P; Monna, A; Munari, E; Seitz, S; Verdugo, M; Ziegler, B

    2015-01-01

    In the effort to understand the link between the structure of galaxy clusters and their galaxy populations, we focus on MACS J1206.2-0847, at z~0.44, probing its substructure in the projected phase space through the spectrophotometric properties of a large number of galaxies from the CLASH-VLT survey. Our analysis is mainly based on an extensive spectroscopic dataset of 445 member galaxies, mostly acquired with VIMOS@VLT as part of our ESO Large Programme, sampling the cluster out to a radius ~2R200 (4 Mpc). We classify 412 galaxies as: passive, with strong Hdelta absorption (red and blue ones), and with emission lines from weak to very strong ones. A number of tests for substructure detection is applied to analyze the galaxy distribution in the velocity space, in the 2D space, and in the (3D) projected phase-space. Studied in its entirety, the cluster appears as a large-scale relaxed system with a few, secondary, minor overdensities in 2D distribution. We detect no velocity gradient or evidence of deviations...

  7. Dwarf-Galaxy Cosmology

    CERN Document Server

    Schulte-Ladbeck, Regina; Brinks, Elias; Kravtsov, Andrey

    2010-01-01

    Dwarf galaxies provide opportunities for drawing inferences about the processes in the early universe by observing our "cosmological backyard"-the Local Group and its vicinity. This special issue of the open-access journal Advances in Astronomy is a snapshot of the current state of the art of dwarf-galaxy cosmology.

  8. Yunnan Starts its Largest Copper Mining and Dressing Project

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    <正> Along with the recent establishment of DiqingMining Development Co.,the largest coppermining and dressing projeject at Yangla,DeqinCounty in Yunnan province started construc-tion.This project is invested by Yunnan Cop-per Group Corp.with RMB10 million yuan forthe mine’s propecting fight and over RMB30million yuan for risk capital.After a year’swork,the copper mine at Yangla is ready forlarge scale development.Yangla Copper Mineis located at the joint area of Yunnan,Sichuan

  9. The largest $n-1$ Hosoya indices of unicyclic graphs

    CERN Document Server

    Yu, Guihai; Ilic, Aleksandar

    2011-01-01

    The Hosoya index $Z (G)$ of a graph $G$ is defined as the total number of edge independent sets of $G$. In this paper, we extend the research of [J. Ou, On extremal unicyclic molecular graphs with maximal Hosoya index, \\textit{Discrete Appl. Math.} 157 (2009) 391--397.] and [Y. Ye, X. Pan, H. Liu, Ordering unicyclic graphs with respect to Hosoya indices and Merrifield-Simmons indices, \\textit{MATCH Commun. Math. Comput. Chem.} 59 (2008) 191--202.] and order the largest $n-1$ unicyclic graphs with respect to the Hosoya index.

  10. Primordial alignment of elliptical galaxies in intermediate redshift clusters

    CERN Document Server

    Rong, Yu; Liao, Jin-Yuan

    2015-01-01

    We measure primordial alignments for the red galaxies in the sample of eight massive galaxy clusters in the southern sky from the CLASH-VLT Large Programme, at a median redshift of 0.375. We find primordial alignment with about $3\\sigma$ significance in the four dynamically young clusters, but null detection of primordial alignment in the four highly relaxed clusters. The observed primordial alignment is not dominated by any single one of the four dynamically young clusters, and is primarily due to a population of bright galaxies ($M_r<-20.5\\ \\rm{m}$) residing in the region 300 to 810 kpc from the cluster centers. For the first time, we point out that the combination of radial alignment and halo alignment can cause fake primordial alignment. Finally, we find that the detected alignment for the dynamically young clusters is real rather than fake primordial alignment.

  11. Alignment of Red-Sequence Cluster Dwarf Galaxies: From the Frontier Fields to the Local Universe

    Science.gov (United States)

    Barkhouse, Wayne Alan; Archer, Haylee; Burgad, Jaford; Foote, Gregory; Rude, Cody; Lopez-Cruz, Omar

    2015-08-01

    Galaxy clusters are the largest virialized structures in the universe. Due to their high density and mass, they are an excellent laboratory for studying the environmental effects on galaxy evolution. Numerical simulations have predicted that tidal torques acting on dwarf galaxies as they fall into the cluster environment will cause the major axis of the galaxies to align with their radial position vector (a line that extends from the cluster center to the galaxy's center). We have undertaken a study to measure the redshift evolution of the alignment of red-sequence cluster dwarf galaxies based on a sample of 57 low-redshift Abell clusters imaged at KPNO using the 0.9-meter telescope, and 64 clusters from the WINGS dataset. To supplement our low-redshift sample, we have included galaxies selected from the Hubble Space Telescope Frontier fields. Leveraging the HST data allows us to look for evolutionary changes in the alignment of red-sequence cluster dwarf galaxies over a redshift range of 0 < z < 0.35. The alignment of the major axis of the dwarf galaxies is measured by fitting a Sersic function to each red-sequence galaxy using GALFIT. The quality of each model is checked visually after subtracting the model from the galaxy. The cluster sample is then combined by scaling each cluster by r200. We present our preliminary results based on the alignment of the red-sequence dwarf galaxies with: 1) the major axis of the brightest cluster galaxy, 2) the major axis of the cluster defined by the position of cluster members, and 3) a radius vector pointing from the cluster center to individual dwarf galaxies. Our combined cluster sample is sub-divided into different radial regions and redshift bins.

  12. MULTIPLE GALAXY COLLISIONS

    Science.gov (United States)

    2002-01-01

    Here is a sampling of 15 ultraluminous infrared galaxies viewed by NASA's Hubble Space Telescope. Hubble's sharp vision reveals more complexity within these galaxies, which astronomers are interpreting as evidence of a multiple-galaxy pileup. These images, taken by the Wide Field and Planetary Camera 2, are part of a three-year study of 123 galaxies within 3 billion light-years of Earth. The study was conducted in 1996, 1997, and 1999. False colors were assigned to these photos to enhance fine details within these coalescing galaxies. Credits: NASA, Kirk Borne (Raytheon and NASA Goddard Space Flight Center, Greenbelt, Md.), Luis Colina (Instituto de Fisica de Cantabria, Spain), and Howard Bushouse and Ray Lucas (Space Telescope Science Institute, Baltimore, Md.)

  13. Gas accretion onto galaxies

    CERN Document Server

    Davé, Romeel

    2017-01-01

    This edited volume presents the current state of gas accretion studies from both observational and theoretical perspectives, and charts our progress towards answering the fundamental yet elusive question of how galaxies get their gas. Understanding how galaxies form and evolve has been a central focus in astronomy for over a century. These studies have accelerated in the new millennium, driven by two key advances: the establishment of a firm concordance cosmological model that provides the backbone on which galaxies form and grow, and the recognition that galaxies grow not in isolation but within a “cosmic ecosystem” that includes the vast reservoir of gas filling intergalactic space. This latter aspect in which galaxies continually exchange matter with the intergalactic medium via inflows and outflows has been dubbed the “baryon cycle”. The topic of this book is directly related to the baryon cycle, in particular its least well constrained aspect, namely gas accretion. Accretion is a rare area of ast...

  14. MULTIPLE GALAXY COLLISIONS

    Science.gov (United States)

    2002-01-01

    Here is a sampling of 15 ultraluminous infrared galaxies viewed by NASA's Hubble Space Telescope. Hubble's sharp vision reveals more complexity within these galaxies, which astronomers are interpreting as evidence of a multiple-galaxy pileup. These images, taken by the Wide Field and Planetary Camera 2, are part of a three-year study of 123 galaxies within 3 billion light-years of Earth. The study was conducted in 1996, 1997, and 1999. False colors were assigned to these photos to enhance fine details within these coalescing galaxies. Credits: NASA, Kirk Borne (Raytheon and NASA Goddard Space Flight Center, Greenbelt, Md.), Luis Colina (Instituto de Fisica de Cantabria, Spain), and Howard Bushouse and Ray Lucas (Space Telescope Science Institute, Baltimore, Md.)

  15. The galaxy ancestor problem

    CERN Document Server

    Disney, Mike

    2011-01-01

    HST finds galaxies whose Tolman dimming should exceed 10 mag. Could evolution alone explain these as our ancestor galaxies? Or could they be representatives of quite a different dynasty whose descendants are no longer prominent today? We explore this latter hypothesis and argue that Surface Brightness Selection Effects naturally bring into focus quite different dynasties from different redshifts. Thus the HST z=7 galaxies could be examples of galaxies whose descendants are both too small and too choked with dust to be recognizable in our neighborhood easily today. Conversely the ancestors of the Milky Way and its obvious neighbors will have completely sunk below the sky at z>1.2 although their diffuse light could account for the missing Reionization flux. This Succeeding Prominent Dynasties Hypothesis (SPDH) fits the existing observations both naturally and well,including the bizarre distributions of galaxy surface brightnesses found in deep fields, the angular size ~ inverse (1+z) law,'Downsizing' which turn...

  16. Interacting Galaxies with MOND

    CERN Document Server

    Tiret, O

    2007-01-01

    We compare N-body simulations performed in MOND with analogs in Newtonian gravity with dark matter (DM). We have developed a code which solves the Poisson equation in both gravity models. It is a grid solver using adaptive mesh refinement techniques, allowing us to study isolated galaxies as well as interacting galaxies. Galaxies in MOND are found to form bars faster and stronger than in the DM model. In Newton dynamics, it is difficult to reproduce the observed high frequency of strong bars, while MOND appears to fit better the observations. Galaxy interactions and mergers, such as the Antennae, are also simulated with Newton and MOND dynamics. In the latter, dynamical friction is much weaker, and merging time-scales are longer. The formation of tidal dwarf galaxies in tidal tails are also compared in MOND and Newton+DM models.

  17. Faint Blue Galaxies

    CERN Document Server

    Ellis, Richard S

    1997-01-01

    The physical properties of the faint blue galaxy population are reviewed in the context of observational progress made via deep spectroscopic surveys and Hubble Space Telescope imaging of field galaxies at various limits, and theoretical models for the integrated star formation history of the Universe. Notwithstanding uncertainties in the properties of the local population of galaxies, convincing evidence has emerged from several independent studies for a rapid decline in the volume-averaged star formation rate of field galaxies since a redshift z~1. Together with the small angular sizes and modest mean redshift of the faintest detectable sources, these results can be understood in hierarchical models where the bulk of the star formation occurred at redshifts between z~1-2. The physical processes responsible for the subsequent demise of the faint blue galaxy population remains unclear. Considerable progress will be possible when the evolutionary trends can be monitored in the context of independent physical p...

  18. A wide angle tail radio galaxy in the COSMOS field: evidence for cluster formation

    CERN Document Server

    Smolcic, V; Finoguenov, A; Sakelliou, I; Carilli, C L; Botzler, C S; Brusa, M; Scoville, N Z; Ajiki, M; Capak, P; Guzzo, L; Hasinger, G; Impey, C; Jahnke, K; Kartaltepe, J S; McCracken, H J; Mobasher, B; Murayama, T; Sasaki, S S; Shioya, Y; Taniguchi, Y; Trump, J R

    2006-01-01

    We have identified a complex galaxy cluster system in the COSMOS field via a wide angle tail (WAT) radio galaxy consistent with the idea that WAT galaxies can be used as tracers of clusters. The WAT galaxy, CWAT-01, is coincident with an elliptical galaxy resolved in the HST-ACS image. Using the COSMOS multiwavelength data set, we derive the radio properties of CWAT-01 and use the optical and X-ray data to investigate its host environment. The cluster hosting CWAT-01 is part of a larger assembly consisting of a minimum of four X-ray luminous clusters within ~2 Mpc distance. We apply hydrodynamical models that combine ram pressure and buoyancy forces on CWAT-01. These models explain the shape of the radio jets only if the galaxy's velocity relative to the intra-cluster medium (ICM) is in the range of about 300-550 km/s which is higher than expected for brightest cluster galaxies (BCGs) in relaxed systems. This indicates that the CWAT-01 host cluster is not relaxed, but is possibly dynamically young. We argue t...

  19. Galaxy Distribution in Clusters of Galaxies

    Science.gov (United States)

    Okamoto, T.; Yachi, S.; Habe, A.

    beta-discrepancy have been pointed out from comparison of optical and X-ray observations of clusters of galaxies. To examine physical reason of beta-discrepancy, we use N-body simulation which contains two components, dark particles and galaxies which are identified by using adaptive-linking friend of friend technique at a certain red-shift. The gas component is not included here, since the gas distribution follows the dark matter distribution in dark halos (Jubio F. Navarro, Carlos S. Frenk and Simon D. M. White 1995). We find that the galaxy distribution follows the dark matter distribution, therefore beta-discrepancy does not exist, and this result is consistent with the interpretation of the beta-discrepancy by Bahcall and Lubin (1994), which was based on recent observation.

  20. Linking the Structural Properties of Galaxies and their Star Formation Histories with STAGES

    CERN Document Server

    Hoyos, Carlos; Gray, Meghan E; Wolf, Christian; Maltby, David T; Bell, Eric F; Böhm, Asmus; Jogee, Shardha

    2015-01-01

    We study the links between star formation history and structure for a large mass-selected galaxy sample at 0.05 < z_phot < 0.30. The galaxies inhabit a very broad range of environments, from cluster cores to the field. Using HST images, we quantify their structure following Hoyos et al. (2012), and divide them into disturbed and undisturbed. We also visually identify mergers. Additionally, we provide a quantitative measure of the degree of disturbance for each galaxy ("roughness"). The majority of elliptical and lenticular galaxies have relaxed structure, showing no signs of ongoing star formation. Structurally-disturbed galaxies, which tend to avoid the lowest-density regions, have higher star-formation activity and younger stellar populations than undisturbed systems. Cluster spirals with reduced/quenched star formation have somewhat less disturbed morphologies than spirals with "normal" star-formation activity, suggesting that these "passive" spirals have started their morphological transformation in...

  1. On the global triggering mechanism of star formation in galaxies

    CERN Document Server

    Escala, Andres

    2009-01-01

    We study the large-scale triggering of star formation in galaxies. We find that the largest mass-scale not stabilized by rotation, a well defined quantity in a rotating system and with clear dynamical meaning, strongly correlates with the star formation rate in a wide range of galaxies. We find that this relation can be explained in terms of the threshold for stability and the amount of turbulence allowed to sustain the system in equilibrium. Using this relation we also derived the observed correlation between the star formation rate and the luminosity of the brightest young stellar cluster.

  2. The Evolution of Post-Starburst Galaxies from z~1 to the Present

    CERN Document Server

    Pattarakijwanich, Petchara; Ho, Shirley; Ross, Nicholas P

    2014-01-01

    Post-starburst galaxies are in the transitional stage between blue, star-forming galaxies and red, quiescent galaxies, and therefore hold important clues for our understanding of galaxy evolution. In this paper, we systematically searched for and identified a large sample of post-starburst galaxies from the spectroscopic dataset of the Sloan Digital Sky Survey (SDSS) Data Release 9. In total, we found more than 6000 objects with redshifts between z ~ 0.05 to z ~ 1.3, making this the largest sample of post-starburst galaxies in the literature. We calculated the luminosity function of the post-starburst galaxies using two uniformly selected subsamples: the SDSS Main Galaxy Sample and the Baryon Oscillation Spectroscopic Survey CMASS sample. The luminosity functions are roughly log-normal. The peak magnitudes shift as a function of redshift from M ~ -23.5 at z ~ 0.8 to M ~ -20.5 at z ~ 0.1. This is consistent with the downsizing trend, whereby higher mass galaxies form earlier than low-mass galaxies. We compared...

  3. The galaxy ancestor problem

    Science.gov (United States)

    Disney, M. J.; Lang, R. H.

    2012-11-01

    The Hubble Space Telescope (HST) findsgalaxies whose Tolman dimming exceeds 10 mag. Could evolution alone explain these as our ancestor galaxies or could they be representatives of quite a different dynasty whose descendants are no longer prominent today? We explore the latter hypothesis and argue that surface brightness selection effects naturally bring into focus quite different dynasties from different redshifts. Thus, the HST z = 7 galaxies could be examples of galaxies whose descendants are both too small and too choked with dust to be recognizable in our neighbourhood easily today. Conversely, the ancestors of the Milky Way and its obvious neighbours would have completely sunk below the sky at z > 1.2, unless they were more luminous in the past, although their diffused light could account for the missing re-ionization flux. This Succeeding Prominent Dynasties Hypothesis (SPDH) fits the existing observations both naturally and well even without evolution, including the bizarre distributions of galaxy surface brightness found in deep fields, the angular size ˜(1 + z)-1 law, 'downsizing' which turns out to be an 'illusion' in the sense that it does not imply evolution, 'infant mortality', that is, the discrepancy between stars born and stars seen, the existence of 'red nuggets', and finally the recently discovered and unexpected excess of quasar absorption line damped Lyα systems at high redshift. If galaxies were not significantly brighter in the past and the SPDH were true, then a large proportion of galaxies could remain sunk from sight, possibly at all redshifts, and these sunken galaxies could supply the missing re-ionization flux. We show that fishing these sunken galaxies out of the sky by their optical emissions alone is practically impossible, even when they are nearby. More ingenious methods are needed to detect them. It follows that disentangling galaxy evolution through studying ever higher redshift galaxies may be a forlorn hope because one could

  4. On Galaxy Mass-Radius Relationship

    Science.gov (United States)

    Bindoni, D.; Secco, L.; Contini, E.; Caimmi, R.

    In the Clausius' virial maximum theory (TCV) [Secco and Bindoni, NewA 14, 567 (2009)] to explain the galaxy Fundamental Plane (FP) a natural explanation follows about the observed relationship between stellar mass and effective radius, M ∗ - r e , for early type galaxies (ETGs). The key of this correlation lies in the deep link which has to exist between cosmology and the existence of the FP. The general strategy consists in using the two-component tensor virial theorem to describe the virial configuration of the baryonic component of mass M B ≃ M ∗ embedded in a dark matter (DM) halo of mass M D at the end of relaxation phase. In a ΛCDM flat cosmology, starting from variance at equivalence epoch, we derive some preliminary theoretical relationships, M ∗ - r e , which are functions of mass ratio m = M D / M B . They appear to be in agreement with the trends extracted from the data of galaxy sample used by [Tortora et al., MNRAS 396, 1132 (2009)].

  5. Star-Forming Complexes in Galaxies

    CERN Document Server

    Elmegreen, B G

    2004-01-01

    Star complexes are the largest globular regions of star formation in galaxies. If there is a spiral density wave, nuclear ring, tidal arm, or other well-defined stellar structure, then gravitational instabilities in the gaseous component produce giant cloud complexes with a spacing of about three times the width. These gas complexes form star complexes, giving the familiar beads on a string of star formation along spiral arms, or nuclear hotspots in the case of a ring. Turbulence compression, supernovae, and self-gravitational contraction inside the giant clouds produce a nearly scale-free structure, including giant molecular clouds that form OB associations and molecular cloud cores that form clusters. Without stellar density waves or similar structures, random gravitational instabilities form flocculent spirals and these fragment into star complexes, OB associations and star clusters in the same way. The largest coherent star-forming regions are the flocculent arms themselves. At the core of the hierarchy a...

  6. Dielectric relaxation of samarium aluminate

    Energy Technology Data Exchange (ETDEWEB)

    Sakhya, Anup Pradhan; Dutta, Alo; Sinha, T.P. [Bose Institute, Department of Physics, Kolkata (India)

    2014-03-15

    A ceramic SmAlO{sub 3} (SAO) sample is synthesized by the solid-state reaction technique. The Rietveld refinement of the X-ray diffraction pattern has been done to find the crystal symmetry of the sample at room temperature. An impedance spectroscopy study of the sample has been performed in the frequency range from 50 Hz to 1 MHz and in the temperature range from 313 K to 573 K. Dielectric relaxation peaks are observed in the imaginary parts of the spectra. The Cole-Cole model is used to analyze the dielectric relaxation mechanism in SAO. The temperature-dependent relaxation times are found to obey the Arrhenius law having an activation energy of 0.29 eV, which indicates that polaron hopping is responsible for conduction or dielectric relaxation in this material. The complex impedance plane plot of the sample indicates the presence of both grain and grain-boundary effects and is analyzed by an electrical equivalent circuit consisting of a resistance and a constant-phase element. The frequency-dependent conductivity spectra follow a double-power law due to the presence of two plateaus. (orig.)

  7. Choosing a skeletal muscle relaxant.

    Science.gov (United States)

    See, Sharon; Ginzburg, Regina

    2008-08-01

    Skeletal muscle relaxants are widely used in treating musculoskeletal conditions. However, evidence of their effectiveness consists mainly of studies with poor methodologic design. In addition, these drugs have not been proven to be superior to acetaminophen or nonsteroidal anti-inflammatory drugs for low back pain. Systematic reviews and meta-analyses support using skeletal muscle relaxants for short-term relief of acute low back pain when nonsteroidal anti-inflammatory drugs or acetaminophen are not effective or tolerated. Comparison studies have not shown one skeletal muscle relaxant to be superior to another. Cyclobenzaprine is the most heavily studied and has been shown to be effective for various musculoskeletal conditions. The sedative properties of tizanidine and cyclobenzaprine may benefit patients with insomnia caused by severe muscle spasms. Methocarbamol and metaxalone are less sedating, although effectiveness evidence is limited. Adverse effects, particularly dizziness and drowsiness, are consistently reported with all skeletal muscle relaxants. The potential adverse effects should be communicated clearly to the patient. Because of limited comparable effectiveness data, choice of agent should be based on side-effect profile, patient preference, abuse potential, and possible drug interactions.

  8. Onsager relaxation of toroidal plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Samain, A.; Nguyen, F.

    1997-01-01

    The slow relaxation of isolated toroidal plasmas towards their thermodynamical equilibrium is studied in an Onsager framework based on the entropy metric. The basic tool is a variational principle, equivalent to the kinetic equation, involving the profiles of density, temperature, electric potential, electric current. New minimization procedures are proposed to obtain entropy and entropy production rate functionals. (author). 36 refs.

  9. Relaxation properties in classical diamagnetism

    Science.gov (United States)

    Carati, A.; Benfenati, F.; Galgani, L.

    2011-06-01

    It is an old result of Bohr that, according to classical statistical mechanics, at equilibrium a system of electrons in a static magnetic field presents no magnetization. Thus a magnetization can occur only in an out of equilibrium state, such as that produced through the Foucault currents when a magnetic field is switched on. It was suggested by Bohr that, after the establishment of such a nonequilibrium state, the system of electrons would quickly relax back to equilibrium. In the present paper, we study numerically the relaxation to equilibrium in a modified Bohr model, which is mathematically equivalent to a billiard with obstacles, immersed in a magnetic field that is adiabatically switched on. We show that it is not guaranteed that equilibrium is attained within the typical time scales of microscopic dynamics. Depending on the values of the parameters, one has a relaxation either to equilibrium or to a diamagnetic (presumably metastable) state. The analogy with the relaxation properties in the Fermi Pasta Ulam problem is also pointed out.

  10. Active galaxies in a complete sample of isolated galaxies

    OpenAIRE

    Sabater, J.; Leon, S.; Verdes-Montenegro, L.; Bergond, G.; Carpio, J.; Combes, F.; Espada, D.; Garc??a, E.; Huchtmeier, W.; Lisenfeld, Ute; Santander-Vela, J. D.; Sulentic, J.; Verley, S.

    2006-01-01

    Galaxy evolution depends strongly on the environment, in particular, galaxy-galaxy interaction can induce nuclear activity by removing angular momentum from the gas so feeding the central black hole. Hence a higher rate of nuclear activity is expected in interacting galaxies. Different studies of this topic lead to contradictory results. Some works conclude that galaxies hosting an active galactic nuclei (AGN) have a higher rate of companions than non active ones. On the other hand other stud...

  11. Earth's Largest Meteorite Impact Craters discovered in South America?

    Science.gov (United States)

    Kellndorfer, J. M.; Schmidt-Falkenberg, H.

    2014-12-01

    Novel analysis of high resolution InSAR-based digital elevation data from the year 2001 Shuttle Radar Topography Mission combined with a recently produced dataset of pan-tropical vegetation height from ALOS-1 SAR and IceSAT/GLAS Lidar estimates led to the quasi-bald-Earth discovery of four sizable near-perfect circle arcs in South America under dense tropical forests ranging in length from 216 km to 441 km. Terrain elevation profiles of cross-sections across the arcs show a distinct vertical rising and falling in elevations of hundreds of meters over a horizontal distance of tens of kilometers. It is hypothesized that these sizable arcs and associated rim-like topographic terrain features are remnants of huge meteorite impact craters with diameters ranging from 770 km to 1,310 km, thus forming potentially the largest known impact carter structures discovered on Earth today. The potential impact crater rim structures are located north of the eastern Amazon River, in the coastal region of Recife and Natal, and in the Brazilian, Bolivian and Paraguayan border region encompassing the Pantanal. Elevation profiles, hillshades and gray-shaded elevation maps were produced to support the geomorphologic analysis. It is also speculated whether in three of the four potential impact craters, central uplift domes or peaks, which are typical for complex impact crater structures can be identified. The worlds largest iron ore mining area of Carajás in Para, Brazil, falls exactly in the center of the largest hypothesized circular impact crater showing topographic elevations similar to the rim structure discovered 655 km to the north-north-west. Based on the topographic/geomorphologic driven hypothesis, geologic exploration of these topographic features is needed to test whether indeed meteorite impact craters could be verified, what the more exact ellipsoidal shapes of the potential impact craters might be, and to determine when during geologic times the impacts would have taken

  12. Rebuilding Spiral Galaxies

    Science.gov (United States)

    2005-01-01

    Major Observing Programme Leads to New Theory of Galaxy Formation Summary Most present-day large galaxies are spirals, presenting a disc surrounding a central bulge. Famous examples are our own Milky Way or the Andromeda Galaxy. When and how did these spiral galaxies form? Why do a great majority of them present a massive central bulge? An international team of astronomers [1] presents new convincing answers to these fundamental questions. For this, they rely on an extensive dataset of observations of galaxies taken with several space- and ground-based telescopes. In particular, they used over a two-year period, several instruments on ESO's Very Large Telescope. Among others, their observations reveal that roughly half of the present-day stars were formed in the period between 8,000 million and 4,000 million years ago, mostly in episodic burst of intense star formation occurring in Luminous Infrared Galaxies. From this and other evidence, the astronomers devised an innovative scenario, dubbed the "spiral rebuilding". They claim that most present-day spiral galaxies are the results of one or several merger events. If confirmed, this new scenario could revolutionise the way astronomers think galaxies formed. PR Photo 02a/05: Luminosity - Oxygen Abundance Relation for Galaxies (VLT) PR Photo 02b/05: The Spiral Rebuilding Scenario A fleet of instruments How and when did galaxies form? How and when did stars form in these island universes? These questions are still posing a considerable challenge to present-day astronomers. Front-line observational results obtained with a fleet of ground- and space-based telescopes by an international team of astronomers [1] provide new insights into these fundamental issues. For this, they embarked on an ambitious long-term study at various wavelengths of 195 galaxies with a redshift [2] greater than 0.4, i.e. located more than 4000 million light-years away. These galaxies were studied using ESO's Very Large Telescope, as well as the

  13. Galaxy 'Hunting' Made Easy

    Science.gov (United States)

    2007-09-01

    Galaxies found under the Glare of Cosmic Flashlights Astronomers using ESO's Very Large Telescope have discovered in a single pass about a dozen otherwise invisible galaxies halfway across the Universe. The discovery, based on a technique that exploits a first-class instrument, represents a major breakthrough in the field of galaxy 'hunting'. ESO PR Photo 40a/07 ESO PR Photo 40a/07 Newly Found Galaxies (SINFONI/VLT) The team of astronomers led by Nicolas Bouché have used quasars to find these galaxies. Quasars are very distant objects of extreme brilliance, which are used as cosmic beacons that reveal galaxies lying between the quasar and us. The galaxy's presence is revealed by a 'dip' in the spectrum of the quasar - caused by the absorption of light at a specific wavelength. The team used huge catalogues of quasars, the so-called SDSS and 2QZ catalogues, to select quasars with dips. The next step was then to observe the patches of the sky around these quasars in search for the foreground galaxies from the time the Universe was about 6 billion years old, almost half of its current age. "The difficulty in actually spotting and seeing these galaxies stems from the fact that the glare of the quasar is too strong compared to the dim light of the galaxy," says Bouché. This is where observations taken with SINFONI on ESO's VLT made the difference. SINFONI is an infrared 'integral field spectrometer' that simultaneously delivers very sharp images and highly resolved colour information (spectra) of an object on the sky. ESO PR Photo 32e/07 ESO PR Photo 40b/07 Chasing 'Hidden' Galaxies (Artist's Impression) With this special technique, which untangles the light of the galaxy from the quasar light, the team detected 14 galaxies out of the 20 pre-selected quasar patches of sky, a hefty 70% success rate. "This high detection rate alone is a very exciting result," says Bouché. "But, these are not just ordinary galaxies: they are most notable ones, actively forming a lot of

  14. Equivalent Relaxations of Optimal Power Flow

    Energy Technology Data Exchange (ETDEWEB)

    Bose, S; Low, SH; Teeraratkul, T; Hassibi, B

    2015-03-01

    Several convex relaxations of the optimal power flow (OPF) problem have recently been developed using both bus injection models and branch flow models. In this paper, we prove relations among three convex relaxations: a semidefinite relaxation that computes a full matrix, a chordal relaxation based on a chordal extension of the network graph, and a second-order cone relaxation that computes the smallest partial matrix. We prove a bijection between the feasible sets of the OPF in the bus injection model and the branch flow model, establishing the equivalence of these two models and their second-order cone relaxations. Our results imply that, for radial networks, all these relaxations are equivalent and one should always solve the second-order cone relaxation. For mesh networks, the semidefinite relaxation and the chordal relaxation are equally tight and both are strictly tighter than the second-order cone relaxation. Therefore, for mesh networks, one should either solve the chordal relaxation or the SOCP relaxation, trading off tightness and the required computational effort. Simulations are used to illustrate these results.

  15. Statistical multifrequency study of narrow-line Seyfert 1 galaxies

    CERN Document Server

    Järvelä, Emilia; León-Tavares, Jonathan

    2014-01-01

    High-energy {\\gamma}-rays, which are produced by powerful relativistic jets, are usually associated with blazars and radio galaxies. In the current active galactic nuclei (AGN) paradigm, such jets are almost exclusively launched from massive elliptical galaxies. Recently, however, Fermi/LAT detected {\\gamma}-rays from a few narrow-line Seyfert 1 galaxies and thus confirmed the presence of relativistic jets in them. Since NLS1 galaxies are assumed to be young evolving AGN, they offer a unique opportunity to study the production of relativistic jets in late-type galaxies. Our aim is to estimate by which processes the emission of various kinds is produced in NLS1 galaxies and to study how emission properties are connected to other intrinsic AGN properties. We have compiled the so far largest multiwavelength database of NLS1 sources. This allowed us to explore correlations between different wavebands and source properties using, for example, Pearson and Spearman correlations and principal component analysis. We d...

  16. Faint features in the isolated galaxy CIG96

    Science.gov (United States)

    Ramírez-Moreta, P.; Verdes-Montenegro, L.; Leon, S.; Blasco-Herrera, J.; Fernández-Lorenzo, M.; Yun, M.; AMIGA Team

    2017-03-01

    The AMIGA project carries out a multiwavelength study of the largest catalogue of isolated galaxies from the Local Universe (CIG, Karachentseva 1973). Compared to any other sample -field galaxies included- and using highly strict isolation criteria (unperturbed for at least ~3 Gyr, Verdes-Montenegro et al. 2005), all the results show that these galaxies have the lowest values of the physical magnitudes expected to be enhanced by interactions. This strongly supports isolated galaxies as ideal laboratories for the study of galaxy formation and evolution. Despite CIG galaxies show the lowest HI integrated profile asymmetry level when compared to any other sample, some cases present up to 50% HI asymmetry (Espada et al. 2011b). We aim to shed light over the causes and sources of such asymmetries with our deep radiointerferometric and optical observations of CIG targets. Since major mergers are ruled out by the isolation criteria, in this work we are addressing whether minor mergers, internal processes or primordial gas accretion are responsible for such asymmetries.

  17. Detecting multi-scale filaments in galaxy distribution

    Science.gov (United States)

    Tempel, Elmo

    2014-05-01

    The main feature of the spatial large-scale galaxy distribution is its intricate network of galaxy filaments. This network is spanned by the galaxy locations that can be interpreted as a three-dimensional point distribution. The global properties of the point process can be measured by different statistical methods, which, however, do not describe directly the structure elements. The morphology of the large-scale structure, on the other hand, is an important property of the galaxy distribution. Here, we apply an object point process with interactions (the Bisous model) to trace and extract the filamentary network in the presently largest galaxy redshift survey, the Sloan Digital Sky Survey (SDSS data release 10). We search for multi-scale filaments in the galaxy distribution that have a radius of about 0.5, 1.0, 2.0, and 4.0 h -1 Mpc. We extract the spines of the filamentary network and divide the detected network into single filaments.

  18. Accretion by the Galaxy

    Directory of Open Access Journals (Sweden)

    Binney J.

    2012-02-01

    Full Text Available Cosmology requires at least half of the baryons in the Universe to be in the intergalactic medium, much of which is believed to form hot coronae around galaxies. Star-forming galaxies must be accreting from their coronae. Hi observations of external galaxies show that they have Hi halos associated with star formation. These halos are naturally modelled as ensembles of clouds driven up by supernova bubbles. These models can fit the data successfully only if clouds exchange mass and momentum with the corona. As a cloud orbits, it is ablated and forms a turbulent wake where cold high-metallicity gas mixes with hot coronal gas causing the prompt cooling of the latter. As a consequence the total mass of Hi increases. This model has recently been used to model the Leiden-Argentina-Bonn survey of Galactic Hi. The values of the model’s parameters that are required to model NGC 891, NGC 2403 and our Galaxy show a remarkable degree of consistency, despite the very different natures of the two external galaxies and the dramatic difference in the nature of the data for our Galaxy and the external galaxies. The parameter values are also consistent with hydrodynamical simulations of the ablation of individual clouds. The model predicts that a galaxy that loses its cool-gas disc for instance through a major merger cannot reform it from its corona; it can return to steady star formation only if it can capture a large body of cool gas, for example by accreting a gas-rich dwarf. Thus the model explains how major mergers can make galaxies “red and dead.”

  19. Dwarf galaxies : Important clues to galaxy formation

    NARCIS (Netherlands)

    Tolstoy, E

    2003-01-01

    The smallest dwarf galaxies are the most straight forward objects in which to study star formation processes on a galactic scale. They are typically single cell star forming entities, and as small potentials in orbit around a much larger one they are unlikely to accrete much (if any) extraneous matt

  20. Social and Spatial Clustering of People at Humanity's Largest Gathering

    CERN Document Server

    Barnett, Ian; Onnela, Jukka-Pekka

    2016-01-01

    Macroscopic behavior of scientific and societal systems results from the aggregation of microscopic behaviors of their constituent elements, but connecting the macroscopic with the microscopic in human behavior has traditionally been difficult. Manifestations of homophily, the notion that individuals tend to interact with others who resemble them, have been observed in many small and intermediate size settings. However, whether this behavior translates to truly macroscopic levels, and what its consequences may be, remains unknown. Here, we use call detail records (CDRs) to examine the population dynamics and manifestations of social and spatial homophily at a macroscopic level among the residents of 23 states of India at the Kumbh Mela, a 3-month-long Hindu festival. We estimate that the festival was attended by 61 million people, making it the largest gathering in the history of humanity. While we find strong overall evidence for both types of homophily for residents of different states, participants from lo...

  1. The 260: The Largest Solid Rocket Motor Ever Tested

    Science.gov (United States)

    Crimmins, P.; Cousineau, M.; Rogers, C.; Shell, V.

    1999-01-01

    Aerojet in the mid 1960s, under contract to NASA, built and static hot fire tested the largest solid rocket motor (SRM) in history for the purpose of demonstrating the feasibility of utilizing large SRMs for space exploration. This program successfully fabricated two high strength steel chambers, loaded each with approximately 1,68 million pounds of propellant, and static test fired these giants with their nozzles up from an underground silo located adjacent to the Florida everglades. Maximum thrust and total impulse in excess of 5,000,000 lbf and 3,470,000,000 lbf-sec were achieved. Flames from the second firing, conducted at night, were seen over eighty miles away. For comparative purposes: the thrust developed was nearly 100 times that of a Minuteman III second stage and the 260 in.-dia cross-section was over 3 times that of the Space Shuttle SRM.

  2. Opportunities for biodiversity gains under the world's largest reforestation programme

    Science.gov (United States)

    Hua, Fangyuan; Wang, Xiaoyang; Zheng, Xinlei; Fisher, Brendan; Wang, Lin; Zhu, Jianguo; Tang, Ya; Yu, Douglas W.; Wilcove, David S.

    2016-01-01

    Reforestation is a critical means of addressing the environmental and social problems of deforestation. China's Grain-for-Green Program (GFGP) is the world's largest reforestation scheme. Here we provide the first nationwide assessment of the tree composition of GFGP forests and the first combined ecological and economic study aimed at understanding GFGP's biodiversity implications. Across China, GFGP forests are overwhelmingly monocultures or compositionally simple mixed forests. Focusing on birds and bees in Sichuan Province, we find that GFGP reforestation results in modest gains (via mixed forest) and losses (via monocultures) of bird diversity, along with major losses of bee diversity. Moreover, all current modes of GFGP reforestation fall short of restoring biodiversity to levels approximating native forests. However, even within existing modes of reforestation, GFGP can achieve greater biodiversity gains by promoting mixed forests over monocultures; doing so is unlikely to entail major opportunity costs or pose unforeseen economic risks to households. PMID:27598524

  3. The largest Silurian vertebrate and its palaeoecological implications

    Science.gov (United States)

    Choo, Brian; Zhu, Min; Zhao, Wenjin; Jia, Liaotao; Zhu, You'an

    2014-01-01

    An apparent absence of Silurian fishes more than half-a-metre in length has been viewed as evidence that gnathostomes were restricted in size and diversity prior to the Devonian. Here we describe the largest pre-Devonian vertebrate (Megamastax amblyodus gen. et sp. nov.), a predatory marine osteichthyan from the Silurian Kuanti Formation (late Ludlow, ~423 million years ago) of Yunnan, China, with an estimated length of about 1 meter. The unusual dentition of the new form suggests a durophagous diet which, combined with its large size, indicates a considerable degree of trophic specialisation among early osteichthyans. The lack of large Silurian vertebrates has recently been used as constraint in palaeoatmospheric modelling, with purported lower oxygen levels imposing a physiological size limit. Regardless of the exact causal relationship between oxygen availability and evolutionary success, this finding refutes the assumption that pre-Emsian vertebrates were restricted to small body sizes. PMID:24921626

  4. BALU: Largest autoclave research facility in the world

    Directory of Open Access Journals (Sweden)

    Hakan Ucan

    2016-03-01

    Full Text Available Among the large-scale facilities operated at the Center for Lightweight-Production-Technology of the German Aerospace Center in Stade BALU is the world's largest research autoclave. With a loading length of 20m and a loading diameter of 5.8 m the main objective of the facility is the optimization of the curing process operated by components made of carbon fiber on an industrial scale. For this reason, a novel dynamic autoclaving control has been developed that is characterized by peripheral devices to expend the performance of the facility for differential applications, by sensing systems to detect the component state throughout the curing process and by a feedback system, which is capable to intervene into the running autoclave process.

  5. Supergranulation as the Sun's largest buoyantly driven mode of convection

    Science.gov (United States)

    Cossette, Jean-Francois; Rast, Mark

    2016-05-01

    Solar supergranulation has been characterized as horizontally divergent flow motions having a typical scale of 32 Mm using Doppler imaging, granule tracking and helioseismology. Unlike granules, the size of which is comparable to both the thickness of the radiative boundary layer and local scale height at the photosphere, supergranules do not appear to correspond to any particular length scale of the flow. Possible explanations ranging from convection theories involving Helium ionization to spatial correlation or self-organization of granular flows have been proposed as physical mechanisms to explain solar supergranulation. However, its existence remains largely a mystery. Remarkably, horizontal velocity power spectra obtained from Doppler imaging and correlation tracking of flow features at the solar surface reveal the presence of peaks corresponding to granular and supergranular scales, followed by a monotonic decrease in power at scales larger than supergranulation, which suggests that large-scale modes in the deep layers of the convection zone may be suppressed. Using 3D anelastic simulations of solar convection we investigate whether supergranulation may reflect the largest buoyantly driven mode of convection inside the Sun. Results show that the amount of kinetic energy contained in the largest flow scales relative to that associated with supergranular motions is a function of the depth of the transition from a convectively unstable to convectively stable mean stratification inside the simulation. This suggests that the observed monotonic decrease in power at scales larger than supergranulation may be explained by rapid cooling in the subphotospheric layers and an essentially isentropic solar interior, wherein convective driving is effectively suppressed.

  6. Evolution of galaxy habitability

    OpenAIRE

    Gobat, R.; Hong, S. E.

    2016-01-01

    We combine a semi-analytic model of galaxy evolution with constraints on circumstellar habitable zones and the distribution of terrestrial planets to probe the suitability of galaxies of different mass and type to host habitable planets, and how it evolves with time. We find that the fraction of stars with terrestrial planets in their habitable zone (known as habitability) depends only weakly on galaxy mass, with a maximum around 4e10 Msun. We estimate that 0.7% of all stars in Milky Way type...

  7. Executing SADI services in Galaxy.

    Science.gov (United States)

    Aranguren, Mikel Egaña; González, Alejandro Rodríguez; Wilkinson, Mark D

    2014-01-01

    In recent years Galaxy has become a popular workflow management system in bioinformatics, due to its ease of installation, use and extension. The availability of Semantic Web-oriented tools in Galaxy, however, is limited. This is also the case for Semantic Web Services such as those provided by the SADI project, i.e. services that consume and produce RDF. Here we present SADI-Galaxy, a tool generator that deploys selected SADI Services as typical Galaxy tools. SADI-Galaxy is a Galaxy tool generator: through SADI-Galaxy, any SADI-compliant service becomes a Galaxy tool that can participate in other out-standing features of Galaxy such as data storage, history, workflow creation, and publication. Galaxy can also be used to execute and combine SADI services as it does with other Galaxy tools. Finally, we have semi-automated the packing and unpacking of data into RDF such that other Galaxy tools can easily be combined with SADI services, plugging the rich SADI Semantic Web Service environment into the popular Galaxy ecosystem. SADI-Galaxy bridges the gap between Galaxy, an easy to use but "static" workflow system with a wide user-base, and SADI, a sophisticated, semantic, discovery-based framework for Web Services, thus benefiting both user communities.

  8. Organic semiconductors: What makes the spin relax?

    Science.gov (United States)

    Bobbert, Peter A.

    2010-04-01

    Spin relaxation in organic materials is expected to be slow because of weak spin-orbit coupling. The effects of deuteration and coherent spin excitation show that the spin-relaxation time is actually limited by hyperfine fields.

  9. Relaxation Techniques to Manage IBS Symptoms

    Science.gov (United States)

    ... the Day Art of IBS Gallery Contact Us Relaxation Techniques to Manage IBS Symptoms Details Content Last Updated: ... Topic Psychological Treatments Understanding Stress Cognitive Behavioral Therapy Relaxation Techniques for IBS You’ve been to the doctor ...

  10. A Classical Morphological Analysis of Galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S4G)

    CERN Document Server

    Buta, R; Athanassoula, E; Bosma, A; Knapen, J; Laurikainen, E; Salo, H; Elmegreen, D; Ho, L; Zaritsky, D; Courtois, H; Hinz, J; Muñoz-Mateos, J-C; Kim, T; Regan, M; Gadotti, D; de Paz, A Gil; Laine, J; Menendez-Delmestre, K; Comeron, Sebastien; Ferrer, S Erroz; Seibert, M; Mizusawa, T; Holwerda, B; Madore, B

    2015-01-01

    The Spitzer Survey of Stellar Structure in Galaxies (S4G) is the largest available database of deep, homogeneous middle-infrared (mid-IR) images of galaxies of all types. The survey, which includes 2352 nearby galaxies, reveals galaxy morphology only minimally affected by interstellar extinction. This paper presents an atlas and classifications of S4G galaxies in the Comprehensive de Vaucouleurs revised Hubble-Sandage (CVRHS) system. The CVRHS system follows the precepts of classical de Vaucouleurs (1959) morphology, modified to include recognition of other features such as inner, outer, and nuclear lenses, nuclear rings, bars, and disks, spheroidal galaxies, X patterns and box/peanut structures, OLR subclass outer rings and pseudorings, bar ansae and barlenses, parallel sequence late-types, thick disks, and embedded disks in 3D early-type systems. We show that our CVRHS classifications are internally consistent, and that nearly half of the S4G sample consists of extreme late-type systems (mostly bulgeless, p...

  11. Plasmon-mediated energy relaxation in graphene

    Energy Technology Data Exchange (ETDEWEB)

    Ferry, D. K. [School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287-5706 (United States); Somphonsane, R. [Department of Physics, King Mongkut' s Institute of Technology, Ladkrabang, Bangkok 10520 (Thailand); Ramamoorthy, H.; Bird, J. P. [Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, New York 14260-1500 (United States)

    2015-12-28

    Energy relaxation of hot carriers in graphene is studied at low temperatures, where the loss rate may differ significantly from that predicted for electron-phonon interactions. We show here that plasmons, important in the relaxation of energetic carriers in bulk semiconductors, can also provide a pathway for energy relaxation in transport experiments in graphene. We obtain a total loss rate to plasmons that results in energy relaxation times whose dependence on temperature and density closely matches that found experimentally.

  12. Collisionless Relaxation of Stellar Systems

    CERN Document Server

    Kandrup, H E

    1998-01-01

    The objective of the work summarised here has been to exploit and extend ideas from plasma physics and accelerator dynamics to formulate a unified description of collisionless relaxation that views violent relaxation, Landau damping, and phase mixing as (manifestations of) a single phenomenon. This approach embraces the fact that the collisionless Boltzmann equation (CBE), the basic object of the theory, is an infinite-dimensional Hamiltonian system, with the distribution function f playing the role of the fundamental dynamical variable, and that, interpreted appropriately, an evolution described by the other Hamiltonian system. Equilibrium solutions correspond to extremal points of the Hamiltonian subject to the constraints associated with Liouville's Theorem. Stable equilibria correspond to energy minima. The evolution of a system out of equilibrium involves (in general nonlinear) phase space oscillations which may -- or may not -- interfere destructively so as to damp away.

  13. Collisionless Relaxation of Stellar Systems

    Science.gov (United States)

    Kandrup, Henry E.

    1999-08-01

    The objective of the work summarized here has been to exploit and extend ideas from plasma physics and accelerator dynamics to formulate a unified description of collisionless relaxation of stellar systems that views violent relaxation, Landau damping, and phase mixing as (manifestations of) a single phenomenon. This approach embraces the fact that the collisionless Boltzmann equation (CBE), the basic object of the theory, is an infinite-dimensional Hamiltonian system, with the distribution function f playing the role of the fundamental dynamical variable, and that, interpreted appropriately, an evolution described by the CBE is no different fundamentally from an evolution described by any other Hamiltonian system. Equilibrium solutions f0 correspond to extremal points of the Hamiltonian subject to the constraints associated with Liouville's Theorem. Stable equilibria correspond to energy minima. The evolution of a system out of equilibrium involves (in general nonlinear) phase space oscillations which may - or may not - interfere destructively so as to damp away.

  14. Kinetic activation-relaxation technique

    Science.gov (United States)

    Béland, Laurent Karim; Brommer, Peter; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand

    2011-10-01

    We present a detailed description of the kinetic activation-relaxation technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si (crystalline silicon), self-interstitial diffusion in Fe, and structural relaxation in a-Si (amorphous silicon).

  15. Kinetic activation-relaxation technique.

    Science.gov (United States)

    Béland, Laurent Karim; Brommer, Peter; El-Mellouhi, Fedwa; Joly, Jean-François; Mousseau, Normand

    2011-10-01

    We present a detailed description of the kinetic activation-relaxation technique (k-ART), an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search. Combining a topological classification for local environments and event generation with ART nouveau, an efficient unbiased sampling method for finding transition states, k-ART can be applied to complex materials with atoms in off-lattice positions or with elastic deformations that cannot be handled with standard KMC approaches. In addition to presenting the various elements of the algorithm, we demonstrate the general character of k-ART by applying the algorithm to three challenging systems: self-defect annihilation in c-Si (crystalline silicon), self-interstitial diffusion in Fe, and structural relaxation in a-Si (amorphous silicon).

  16. Brief relaxation training program for hospital employees.

    Science.gov (United States)

    Balk, Judith L; Chung, Sheng-Chia; Beigi, Richard; Brooks, Maria

    2009-01-01

    Employee stress leads to attrition, burnout, and increased medical costs. We aimed to assess if relaxation training leads to decreased stress levels based on questionnaire and thermal biofeedback. Thirty-minute relaxation training sessions were conducted for hospital employees and for cancer patients. Perceived Stress levels and skin temperature were analyzed before and after relaxation training.

  17. POS Tagging Using Relaxation Labelling

    CERN Document Server

    Padro, L

    1995-01-01

    Relaxation labelling is an optimization technique used in many fields to solve constraint satisfaction problems. The algorithm finds a combination of values for a set of variables such that satisfies -to the maximum possible degree- a set of given constraints. This paper describes some experiments performed applying it to POS tagging, and the results obtained. It also ponders the possibility of applying it to word sense disambiguation.

  18. Galaxies and Cladistics

    CERN Document Server

    Fraix-Burnet, Didier

    2009-01-01

    The Hubble tuning fork diagram, based on morphology and established in the 1930s, has always been the preferred scheme for classification of galaxies. However, the current large amount of multiwavelength data, most often spectra, for objects up to very high distances, asks for more sophisticated statistical approaches. Interpreting formation and evolution of galaxies as a ?transmission with modification' process, we have shown that the concepts and tools of phylogenetic systematics can be heuristically transposed to the case of galaxies. This approach, which we call ?astrocladistics', has successfully been applied on several samples. Many difficulties still remain, some of them being specific to the nature of both galaxies and their diversification processes, some others being classical in cladistics, like the pertinence of the descriptors in conveying any useful evolutionary information.

  19. Collision Induced Galaxy Formation

    CERN Document Server

    Balland, C; Schäffer, R

    1997-01-01

    We present a semi-analytical model in which galaxy collisions and strong tidal interactions, both in the field and during the collapse phase of groups and clusters help determine galaxy morphology. From a semi-analytical analysis based on simulation results of tidal collisions (Aguilar & White 1985), we propose simple rules for energy exchanges during collisions that allow to discriminate between different Hubble types: efficient collisions result in the disruption of disks and substantial star formation, leading to the formation of elliptical galaxies; inefficient collisions allow a large gas reservoir to survive and form disks. Assuming that galaxy formation proceeds in a Omega_0=1 Cold Dark Matter universe, the model both reproduces a number of observations and makes predictions, among which are the redshifts of formation of the different Hubble types in the field. When the model is normalized to the present day abundance of X-ray clusters, the amount of energy exchange needed to produce elliptical gal...

  20. Black Hole Caught Zapping Galaxy into Existence?

    Science.gov (United States)

    2009-11-01

    Which come first, the supermassive black holes that frantically devour matter or the enormous galaxies where they reside? A brand new scenario has emerged from a recent set of outstanding observations of a black hole without a home: black holes may be "building" their own host galaxy. This could be the long-sought missing link to understanding why the masses of black holes are larger in galaxies that contain more stars. "The 'chicken and egg' question of whether a galaxy or its black hole comes first is one of the most debated subjects in astrophysics today," says lead author David Elbaz. "Our study suggests that supermassive black holes can trigger the formation of stars, thus 'building' their own host galaxies. This link could also explain why galaxies hosting larger black holes have more stars." To reach such an extraordinary conclusion, the team of astronomers conducted extensive observations of a peculiar object, the nearby quasar HE0450-2958 (see eso0523 for a previous study of this object), which is the only one for which a host galaxy has not yet been detected [1]. HE0450-2958 is located some 5 billion light-years away. Until now, it was speculated that the quasar's host galaxy was hidden behind large amounts of dust, and so the astronomers used a mid-infrared instrument on ESO's Very Large Telescope for the observations [2]. At such wavelengths, dust clouds shine very brightly, and are readily detected. "Observing at these wavelengths would allow us to trace dust that might hide the host galaxy," says Knud Jahnke, who led the observations performed at the VLT. "However, we did not find any. Instead we discovered that an apparently unrelated galaxy in the quasar's immediate neighbourhood is producing stars at a frantic rate." These observations have provided a surprising new take on the system. While no trace of stars is revealed around the black hole, its companion galaxy is extremely rich in bright and very young stars. It is forming stars at a rate

  1. Spin relaxation in metallic ferromagnets

    Science.gov (United States)

    Berger, L.

    2011-02-01

    The Elliott theory of spin relaxation in metals and semiconductors is extended to metallic ferromagnets. Our treatment is based on the two-current model of Fert, Campbell, and Jaoul. The d→s electron-scattering process involved in spin relaxation is the inverse of the s→d process responsible for the anisotropic magnetoresistance (AMR). As a result, spin-relaxation rate 1/τsr and AMR Δρ are given by similar formulas, and are in a constant ratio if scattering is by solute atoms. Our treatment applies to nickel- and cobalt-based alloys which do not have spin-up 3d states at the Fermi level. This category includes many of the technologically important magnetic materials. And we show how to modify the theory to apply it to bcc iron-based alloys. We also treat the case of Permalloy Ni80Fe20 at finite temperature or in thin-film form, where several kinds of scatterers exist. Predicted values of 1/τsr and Δρ are plotted versus resistivity of the sample. These predictions are compared to values of 1/τsr and Δρ derived from ferromagnetic-resonance and AMR experiments in Permalloy.

  2. Arresting relaxation in Pickering Emulsions

    Science.gov (United States)

    Atherton, Tim; Burke, Chris

    2015-03-01

    Pickering emulsions consist of droplets of one fluid dispersed in a host fluid and stabilized by colloidal particles absorbed at the fluid-fluid interface. Everyday materials such as crude oil and food products like salad dressing are examples of these materials. Particles can stabilize non spherical droplet shapes in these emulsions through the following sequence: first, an isolated droplet is deformed, e.g. by an electric field, increasing the surface area above the equilibrium value; additional particles are then adsorbed to the interface reducing the surface tension. The droplet is then allowed to relax toward a sphere. If more particles were adsorbed than can be accommodated by the surface area of the spherical ground state, relaxation of the droplet is arrested at some non-spherical shape. Because the energetic cost of removing adsorbed colloids exceeds the interfacial driving force, these configurations can remain stable over long timescales. In this presentation, we present a computational study of the ordering present in anisotropic droplets produced through the mechanism of arrested relaxation and discuss the interplay between the geometry of the droplet, the dynamical process that produced it, and the structure of the defects observed.

  3. Relaxation response in femoral angiography.

    Science.gov (United States)

    Mandle, C L; Domar, A D; Harrington, D P; Leserman, J; Bozadjian, E M; Friedman, R; Benson, H

    1990-03-01

    Immediately before they underwent femoral angiography, 45 patients were given one of three types of audiotapes: a relaxation response tape recorded for this study, a tape of contemporary instrumental music, or a blank tape. All patients were instructed to listen to their audiotape during the entire angiographic procedure. Each audiotape was played through earphones. Radiologists were not told the group assignment or tape contents. The patients given the audiotape with instructions to elicit the relaxation response (n = 15) experienced significantly less anxiety (P less than .05) and pain (P less than .001) during the procedure, were observed by radiology nurses to exhibit significantly less pain (P less than .001) and anxiety (P less than .001), and requested significantly less fentanyl citrate (P less than .01) and diazepam (P less than .01) than patients given either the music (n = 14) or the blank (n = 16) control audiotapes. Elicitation of the relaxation response is a simple, inexpensive, efficacious, and practical method to reduce pain, anxiety, and medication during femoral angiography and may be useful in other invasive procedures.

  4. Alignments between galaxies, satellite systems and haloes

    CERN Document Server

    Shao, Shi; Frenk, Carlos S; Gao, Liang; Crain, Robert A; Schaller, Matthieu; Schaye, Joop; Theuns, Tom

    2016-01-01

    The spatial distribution of the satellite populations of the Milky Way and Andromeda are puzzling in that they are nearly perpendicular to the disks of their central galaxies. To understand the origin of such configurations we study the alignment of the central galaxy, satellite system and dark matter halo in the largest of the "Evolution and Assembly of GaLaxies and their Environments" (EAGLE) simulation. We find that centrals and their satellite systems tend to be well aligned with their haloes, with a median misalignment angle of $33^{\\circ}$ in both cases. While the centrals are better aligned with the inner $10$ kpc halo, the satellite systems are better aligned with the entire halo indicating that satellites preferentially trace the outer halo. The central - satellite alignment is weak (median misalignment angle of $52^{\\circ}$) and we find that around $20\\%$ of systems have a misalignment angle larger than $78^{\\circ}$, which is the value for the Milky Way. The central - satellite alignment is a conseq...

  5. Magnetic Field Amplification in Young Galaxies

    CERN Document Server

    Schober, Jennifer; Klessen, Ralf S

    2013-01-01

    The Universe at present is highly magnetized, with fields of the order of a few 10^-5 G and coherence lengths larger than 10 kpc in typical galaxies like the Milky Way. We propose that the magnetic field was amplified to this values already during the formation and the early evolution of the galaxies. Turbulence in young galaxies is driven by accretion as well as by supernova (SN) explosions of the first generation of stars. The small-scale dynamo can convert the turbulent kinetic energy into magnetic energy and amplify very weak primordial magnetic seed fields on short timescales. The amplification takes place in two phases: in the kinematic phase the magnetic field grows exponentially, with the largest growth on the smallest non-resistive scale. In the following non-linear phase the magnetic energy is shifted towards larger scales until the dynamo saturates on the turbulent forcing scale. To describe the amplification of the magnetic field quantitatively we model the microphysics in the interstellar medium ...

  6. Galaxy Zoo: finding offset discs and bars in SDSS galaxies★

    Science.gov (United States)

    Kruk, Sandor J.; Lintott, Chris J.; Simmons, Brooke D.; Bamford, Steven P.; Cardamone, Carolin N.; Fortson, Lucy; Hart, Ross E.; Häußler, Boris; Masters, Karen L.; Nichol, Robert C.; Schawinski, Kevin; Smethurst, Rebecca J.

    2017-08-01

    We use multiwavelength Sloan Digital Sky Survey (SDSS) images and Galaxy Zoo morphologies to identify a sample of ∼270 late-type galaxies with an off-centre bar. We measure offsets in the range 0.2-2.5 kpc between the photometric centres of the stellar disc and stellar bar. The measured offsets correlate with global asymmetries of the galaxies, with those with largest offsets showing higher lopsidedness. These findings are in good agreement with predictions from simulations of dwarf-dwarf tidal interactions producing off-centre bars. We find that the majority of galaxies with off-centre bars are of Magellanic type, with a median mass of 109.6 M⊙, and 91 per cent of them having M⋆ < 3 × 1010 M⊙, the characteristic mass at which galaxies start having higher central concentrations attributed to the presence of bulges. We conduct a search for companions to test the hypothesis of tidal interactions, but find that a similar fraction of galaxies with offset bars have companions within 100 kpc as galaxies with centred bars. Although this may be due to the incompleteness of the SDSS spectroscopic survey at the faint end, alternative scenarios that give rise to offset bars such as interactions with dark companions or the effect of lopsided halo potentials should be considered. Future observations are needed to confirm possible low-mass companion candidates and to determine the shape of the dark matter halo, in order to find the explanation for the off-centre bars in these galaxies.

  7. What is a Galaxy? Cast your vote here...

    CERN Document Server

    Forbes, Duncan

    2011-01-01

    Although originally classified as galaxies, Ultra Compact Dwarfs (UCDs) share many properties in common with globular star clusters. The debate on the origin and nature of UCDs, and the recently discovered ultra-faint dwarf spheroidal (dSph) galaxies which contain very few stars, has motivated us to ask the question `what is a galaxy?' Our aim here is to promote further discussion of how to define a galaxy and, in particular, what separates it from a star cluster. Like most previous definitions, we adopt the requirement of a gravitationally bound stellar system as a minimum. In order to separate a dwarf galaxy from a globular cluster, we discuss other possible requirements, such as a minimum size, a long two-body relaxation time, a satellite system, the presence of complex stellar populations and non-baryonic dark matter. We briefly mention the implications of each of these definitions if they are adopted. Some special cases of objects with an ambiguous nature are also discussed. Finally, we give our favoured...

  8. Galaxies and chaos

    CERN Document Server

    Voglis, Nikos

    2003-01-01

    Galaxies and Chaos examines the application of tools developed for Nonlinear Dynamical Systems to Galactic Dynamics and Galaxy Formation, as well as to related issues in Celestial Mechanics. The contributions collected in this volume have emerged from selected presentations at a workshop on this topic and key chapters have been suitably expanded in order to be accessible to nonspecialist researchers and postgraduate students wishing to enter this exciting field of research.

  9. SUPERLUMINOUS SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Ogle, Patrick M.; Lanz, Lauranne; Nader, Cyril; Helou, George, E-mail: ogle@ipac.caltech.edu [IPAC, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125 (United States)

    2016-02-01

    We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster galaxies, with r-band monochromatic luminosity L{sub r} = 8–14L* (4.3–7.5 × 10{sup 44} erg s{sup −1}). These super spiral galaxies are also giant and massive, with diameter D = 57–134 kpc and stellar mass M{sub stars} = 0.3–3.4 × 10{sup 11}M{sub ⊙}. We find 53 super spirals out of a complete sample of 1616 SDSS galaxies with redshift z < 0.3 and L{sub r} > 8L*. The closest example is found at z = 0.089. We use existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS and Wide-field Infrared Survey Explorer colors are consistent with normal star-forming spirals on the blue sequence. However, the extreme masses and rapid SFRs of 5–65 M{sub ⊙} yr{sup −1} place super spirals in a sparsely populated region of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a diverse range of environments, from isolation to cluster centers. We find four super spiral galaxy systems that are late-stage major mergers—a possible clue to their formation. We suggest that super spirals are a remnant population of unquenched, massive disk galaxies. They may eventually become massive lenticular galaxies after they are cut off from their gas supply and their disks fade.

  10. The Integral Sign Galaxy

    Science.gov (United States)

    Noll, Keith

    2007-07-01

    We will observe the unusual warped disk galaxy known as the Integral Sign Galaxy, UGC 3697, with a small two-position WFPC2 mosaic. Observations will be obtained in three broad band filters and the resulting image will be released on the 19th anniversary of the launch of the Hubble Space Telescope on ~April 24, 2009. Multidrizzled mosaics will be made available through the archive.

  11. Galaxy Formation and Evolution

    Science.gov (United States)

    Nagamine, Kentaro; Reddy, Naveen; Daddi, Emanuele; Sargent, Mark T.

    2016-07-01

    In this chapter, we discuss the current status of observational and computational studies on galaxy formation and evolution. In particular, a joint analysis of star-formation rates (SFRs), stellar masses, and metallicities of galaxies throughout cosmic time can shed light on the processes by which galaxies build up their stellar mass and enrich the environment with heavy elements. Comparison of such observations and the results of numerical simulations can give us insights on the physical importance of various feedback effects by supernovae and active galactic nuclei. In Sect. 1, we first discuss the primary methods used to deduce the SFRs, stellar masses, and (primarily) gas-phase metallicities in high-redshift galaxies. Then, we show how these quantities are related to each other and evolve with time. In Sect. 2, we further examine the distribution of SFRs in galaxies following the `Main Sequence' paradigm. We show how the so-called `starbursts' display higher specific SFRs and SF efficiencies by an order of magnitude. We use this to devise a simple description of the evolution of the star-forming galaxy population since z ˜3 that can successfully reproduce some of the observed statistics in the infrared (IR) wavelength. We also discuss the properties of molecular gas. In Sect. 3, we highlight some of the recent studies of high-redshift galaxy formation using cosmological hydrodynamic simulations. We discuss the physical properties of simulated galaxies such as luminosity function and escape fraction of ionizing photons, which are important statistics for reionization of the Universe. In particular the escape fraction of ionizing photons has large uncertainties, and studying gamma-ray bursts (which is the main topic of this conference) can also set observational constraints on this uncertain physical parameter as well as cosmic star formation rate density.

  12. CLASH: Complete Lensing Analysis of the Largest Cosmic Lens MACS J0717.5+3745 and Surrounding Structures

    CERN Document Server

    Medezinski, Elinor; Nonino, Mario; Merten, Julian; Zitrin, Adi; Broadhurst, Tom; Donahue, Megan; Sayers, Jack; Waizmann, Jean-Claude; Koekemoer, Anton; Coe, Dan; Molino, Alberto; Melchior, Peter; Mroczkowski, Tony; Czakon, Nicole; Postman, Marc; Meneghetti, Massimo; Lemze, Doron; Ford, Holland; Grillo, Claudio; Kelson, Daniel; Bradley, Larry; Moustakas, John; Bartelmann, Matthias; Benítez, Narciso; Biviano, Andrea; Bouwens, Rychard; Golwala, Sunil; Graves, Genevieve; Infante, Leopoldo; Jiménez-Teja, Yolanda; Jouvel, Stephanie; Lahav, Ofer; Moustakas, Leonidas; Ogaz, Sara; Rosati, Piero; Seitz, Stella; Zheng, Wei

    2013-01-01

    The galaxy cluster MACS J0717.5+3745 (z=0.55) is the largest known cosmic lens, with complex internal structures seen in deep X-ray, Sunyaev-Zel'dovich effect and dynamical observations. We perform a combined weak and strong lensing analysis with wide-field BVRi'z' Subaru/Suprime-Cam observations and 16-band Hubble Space Telescope observations taken as part of the Cluster Lensing And Supernova survey with Hubble (CLASH). We find consistent weak distortion and magnification measurements of background galaxies, and combine these signals to construct an optimally estimated radial mass profile of the cluster and its surrounding large-scale structure out to 5 Mpc/h. We find consistency between strong-lensing and weak-lensing in the region where these independent data overlap, 0.5, in terms of extreme value statistics we conclude that the mass of MACS J0717.5+3745 by itself is not in serious tension with LambdaCDM, representing only a ~2{\\sigma} departure above the maximum simulated halo mass at this redshift.

  13. ATLAS, and Wide-Angle Tail Galaxies in ATLAS

    Indian Academy of Sciences (India)

    Minnie Y. Mao; Rob Sharp; D. J. Saikia; Ray P. Norris; Melanie Johnston-Hollitt; Enno Middelberg; Jim E. J. Lovell

    2011-12-01

    Using the Australia Telescope Compact Array (ATCA), ATLAS (Australia Telescope Large Area Survey) is imaging two fields totalling 7 square degrees down to 10 Jy beam-1 at 1.4 GHz. We have found 6 wide-angle tail galaxies (WATs), 4 of which have sufficient data to identify associated galaxy overdensities. The largest WAT, at a red-shift of 0.22, appears to be associated with an overdensity of galaxies that is spread over an unusually large extent of 12Mpc, with a velocity range of 4500 km s-1. Here we present the WATs in ATLAS and discuss the implications of these observations for future large-scale radio surveys such as ASKAP-EMU.

  14. Structures and components in galaxy clusters: observations and models

    CERN Document Server

    Bykov, A M; Ferrari, C; Forman, W R; Kaastra, J S; Klein, U; Markevitch, M; de Plaa, J

    2015-01-01

    Clusters of galaxies are the largest gravitationally bounded structures in the Universe dominated by dark matter. We review the observational appearance and physical models of plasma structures in clusters of galaxies. Bubbles of relativistic plasma which are inflated by supermassive black holes of AGNs, cooling and heating of the gas, large scale plasma shocks, cold fronts, non-thermal halos and relics are observed in clusters. These constituents are reflecting both the formation history and the dynamical properties of clusters of galaxies. We discuss X-ray spectroscopy as a tool to study the metal enrichment in clusters and fine spectroscopy of Fe X-ray lines as a powerful diagnostics of both the turbulent plasma motions and the energetics of the non-thermal electron populations. The knowledge of the complex dynamical and feedback processes is necessary to understand the energy and matter balance as well as to constrain the role of the non-thermal components of clusters.

  15. Rotating stellar populations in the Fornax dSph galaxy

    CERN Document Server

    del Pino, Andrés; Hidalgo, Sebastian L; Lokas, Ewa L

    2016-01-01

    We present a novel analysis of the internal kinematics of the Fornax dwarf spheroidal galaxy. Our results are based on the largest sample of spectroscopic data for Fornax stars presently available ($> 2500$ stars), for which we have chemical and kinematic information. We introduce new software, Beacon, designed to detect chemo-kinematic patterns among stars of different stellar populations using their metallicity and velocity along the line of sight. Applying Beacon to Fornax we have detected non-negligible rotation signals around main optical axes of the galaxy, characteristic for a triaxial system partially supported by rotation. The dominant rotation pattern is relatively strong ($\\sim 12$ km s$^{-1}$), but the galaxy also shows additional weaker albeit complex rotation patterns. Using the information available from the star formation history of Fornax we have also derived the average age of the different chemo-kinematic components found by Beacon, which has allowed us to obtain its kinematic history. Our ...

  16. Magnetic fields in ring galaxies

    CERN Document Server

    Moss, D; Silchenko, O; Sokoloff, D; Horellou, C; Beck, R

    2016-01-01

    Many galaxies contain magnetic fields supported by galactic dynamo action. However, nothing definitive is known about magnetic fields in ring galaxies. Here we investigate large-scale magnetic fields in a previously unexplored context, namely ring galaxies, and concentrate our efforts on the structures that appear most promising for galactic dynamo action, i.e. outer star-forming rings in visually unbarred galaxies. We use tested methods for modelling $\\alpha-\\Omega$ galactic dynamos, taking into account the available observational information concerning ionized interstellar matter in ring galaxies. Our main result is that dynamo drivers in ring galaxies are strong enough to excite large-scale magnetic fields in the ring galaxies studied. The variety of dynamo driven magnetic configurations in ring galaxies obtained in our modelling is much richer than that found in classical spiral galaxies. In particular, various long-lived transients are possible. An especially interesting case is that of NGC 4513 where th...

  17. Modelling Thermal Emission to Constrain Io's Largest Eruptions

    Science.gov (United States)

    Davies, A. G.; De Pater, I.; de Kleer, K.; Head, J. W., III; Wilson, L.

    2016-12-01

    Massive, voluminous, low-silica content basalt lava flows played a major role in shaping the surfaces of the terrestrial planets and the Moon [1] but the mechanisms of eruption, including effusion rate profiles and flow regime, are often obscure. However, eruptions of large volumes of lava and the emplacement of thick, areally extensive silicate lava flows are extant on the volcanic jovian moon Io [2], thus providing a template for understanding how these processes behaved elsewhere in the Solar System. We have modelled data of the largest of these eruptions to constrain eruption processes from the evolution of the wavelength variation of the resulting thermal emission [3]. We continue to refine our models to further constrain eruption parameters. We focus on large "outburst" eruptions, large lava fountains which feed lava flows [4] which have been directly observed on Io from the Galileo spacecraft [5, 6]. Outburst data continue to be collected by large ground-based telescopes [7, 8]. These data have been fitted with a sophisticated thermal emission model to derive eruption parameters such as areal coverage and effusion rates. We have created a number of tools for investigating and constraining effusion rate for Io's largest eruptions. It remains for all of the components to be integrated into a single model with rheological properties dependent on flow regime and the effects of heat loss. The crucial advance on previous estimates of lava flow emplacement on Io [e.g., 5] is that, by keeping track of the temperature distribution on the surface of the lava flows (a function of flow regime and varying effusion rate) the integrated thermal emission spectrum can be synthesized. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. We thank the NASA OPR Program (NNN13D466T) and NSF (Grant AST-1313485) for supports. Refs: [1] Wilson, L. and J. W. Head (2016), Icarus, doi:10.1016/j.icarus.2015.12.039. [2

  18. Superluminous Spiral Galaxies

    CERN Document Server

    Ogle, Patrick M; Nader, Cyril; Helou, George

    2015-01-01

    We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster galaxies, with r-band monochromatic luminosity L_r=8-14L* (4.3-7.5E44 erg/s). These super spiral galaxies are also giant and massive, with diameter D=57-134 kpc and stellar mass M_stars=0.3-3.4E11 M_sun. We find 53 super spirals out of a complete sample of 1,616 SDSS galaxies with redshift z8L*. The closest example is found at z=0.089. We use existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS and WISE colors are consistent with normal star-forming spirals on the blue sequence. However, the extreme masses and rapid SFRs of 5-65 M_sun/yr place super spirals in a sparsely populated region of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a diverse range of environments, from isolation to cluster centers. We find four super spiral galaxy systems that are late-stage major mergers--a possible clue to their formation. We su...

  19. Coma cluster of galaxies

    Science.gov (United States)

    1999-01-01

    Atlas Image mosaic, covering 34' x 34' on the sky, of the Coma cluster, aka Abell 1656. This is a particularly rich cluster of individual galaxies (over 1000 members), most prominently the two giant ellipticals, NGC 4874 (right) and NGC 4889 (left). The remaining members are mostly smaller ellipticals, but spiral galaxies are also evident in the 2MASS image. The cluster is seen toward the constellation Coma Berenices, but is actually at a distance of about 100 Mpc (330 million light years, or a redshift of 0.023) from us. At this distance, the cluster is in what is known as the 'Hubble flow,' or the overall expansion of the Universe. As such, astronomers can measure the Hubble Constant, or the universal expansion rate, based on the distance to this cluster. Large, rich clusters, such as Coma, allow astronomers to measure the 'missing mass,' i.e., the matter in the cluster that we cannot see, since it gravitationally influences the motions of the member galaxies within the cluster. The near-infrared maps the overall luminous mass content of the member galaxies, since the light at these wavelengths is dominated by the more numerous older stellar populations. Galaxies, as seen by 2MASS, look fairly smooth and homogeneous, as can be seen from the Hubble 'tuning fork' diagram of near-infrared galaxy morphology. Image mosaic by S. Van Dyk (IPAC).

  20. Searches For Primeval Galaxies

    CERN Document Server

    Collins, C A

    1998-01-01

    A primeval galaxy represents the earliest stages of a galaxy's life and as such provides clues to the early history of the Universe and the evolution of stars and galaxies. Over the last 20 years astronomers have been engaged in the quest to detect the faint signals from these objects, believed to lie at a distance comparable with the size of the Universe. A wide variety of observational techniques have been employed in this search, with astronomers eagerly awaiting each new generation of astronomical telescope or detector in the hope of finally solving the mystery to the origin of galaxies -- or at least placing new and interesting constraints. Until recently, primeval galaxies have eluded detection in these searches, however experiments over the last couple of years which use either 10m-class optical telescopes or state-of-the-art submillimetre array detectors, may hold the clue to the origin of structure as they have finally uncovered what appears to be a widespread population of young galaxies.

  1. Dissection of a Galaxy

    Science.gov (United States)

    2004-01-01

    Sometimes, the best way to understand how something works is to take it apart. The same is true for galaxies like NGC 300, which NASA's Spitzer Space Telescope has divided into its various parts. NGC 300 is a face-on spiral galaxy located 7.5 million light-years away in the southern constellation Sculptor. This false-color image taken by the infrared array camera on Spitzer readily distinguishes the main star component of the galaxy (blue) from its dusty spiral arms (red). The star distribution peaks strongly in the central bulge where older stars congregate, and tapers off along the arms where younger stars reside. Thanks to Spitzer's unique ability to sense the heat or infrared emission from dust, astronomers can now clearly trace the embedded dust structures within NGC 300's arms. When viewed at visible wavelengths, the galaxy's dust appears as dark lanes, largely overwhelmed by bright starlight. With Spitzer, the dust - in particular organic compounds called polycyclic aromatic hydrocarbons - can be seen in vivid detail (red). These organic molecules are produced, along with heavy elements, by the stellar nurseries that pepper the arms. The findings provide a better understanding of spiral galaxy mechanics and, in the future, will help decipher more distant galaxies, whose individual components cannot be resolved. This image was taken on Nov. 21, 2003 and is composed of photographs obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

  2. General statistics and principal component analysis of multiwavelength properties of Seyfert galaxies.

    Science.gov (United States)

    Dultzin-Hacyan, D.; Ruano, C.

    1996-01-01

    We present a statistical study including principal component analysis (PCA) of multiwavelength properties of types 1 and 2 Seyfert galaxies. We have applied PCA to an ensemble of X-ray, optical, near and far infrared, and radio data of Seyfert galaxies. We used Lipovetsky et al. (1987) catalog which provides the largest list of Seyfert galaxies with multiwavelength data. Our main result is that the Spectral Energy Distribution (SED) of Seyfert 1 galaxies is well accounted by one and only one underlying variable, at least to a first approximation. On the other hand, in the case of Seyfert 2 galaxies, at least three variables are required. Several details of the analysis lead us to the following interpretation of this result: In the case of Seyfert 1 galaxies, the main process at the origin of radiation is the release of energy of gravitational origin by accretion unto a supermassive black hole. In the case of Seyfert 2 galaxies, there are other important processes apart from energy of gravitational origin, which we may identify with stellar and interstellar radiation (mainly dust absortion and re-emission) from the circumnuclear region. In the framework of this interpretation the analysis reveals that the variance in luminosity related to radiation of stellar/interstellar origin in no case exceeds ~13% for Seyfert 1 galaxies. In contrast, for Seyfert 2 galaxies the radiation of stellar/interstellar origin can account for ~46% of the variance in certain luminosities.

  3. The SCUBA-2 Cosmology Legacy Survey: the clustering of submillimetre galaxies in the UKIDSS UDS field

    Science.gov (United States)

    Wilkinson, Aaron; Almaini, Omar; Chen, Chian-Chou; Smail, Ian; Arumugam, Vinodiran; Blain, Andrew; Chapin, Edward L.; Chapman, Scott C.; Conselice, Christopher J.; Cowley, William I.; Dunlop, James S.; Farrah, Duncan; Geach, James; Hartley, William G.; Ivison, Rob J.; Maltby, David T.; Michałowski, Michał J.; Mortlock, Alice; Scott, Douglas; Simpson, Chris; Simpson, James M.; van der Werf, Paul; Wild, Vivienne

    2017-01-01

    Submillimetre galaxies (SMGs) are among the most luminous dusty galaxies in the Universe, but their true nature remains unclear; are SMGs the progenitors of the massive elliptical galaxies we see in the local Universe, or are they just a short-lived phase among more typical star-forming galaxies? To explore this problem further, we investigate the clustering of SMGs identified in the SCUBA-2 Cosmology Legacy Survey. We use a catalogue of submillimetre (850 μm) source identifications derived using a combination of radio counterparts and colour/infrared selection to analyse a sample of 610 SMG counterparts in the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Survey (UKIDSS) Ultra Deep Survey (UDS), making this the largest high-redshift sample of these galaxies to date. Using angular cross-correlation techniques, we estimate the halo masses for this large sample of SMGs and compare them with passive and star-forming galaxies selected in the same field. We find that SMGs, on average, occupy high-mass dark matter haloes (Mhalo > 1013 M⊙) at redshifts z > 2.5, consistent with being the progenitors of massive quiescent galaxies in present-day galaxy clusters. We also find evidence of downsizing, in which SMG activity shifts to lower mass haloes at lower redshifts. In terms of their clustering and halo masses, SMGs appear to be consistent with other star-forming galaxies at a given redshift.

  4. The Clustering Characteristics of HI-Selected Galaxies from the 40% ALFALFA Survey

    CERN Document Server

    Martin, Ann M; Haynes, Martha P; Guzzo, Luigi

    2012-01-01

    The 40% Arecibo Legacy Fast ALFA (ALFALFA) survey catalog (\\alpha.40) of approximately 10,150 HI-selected galaxies is used to analyze the clustering properties of gas-rich galaxies. By employing the Landy-Szalay estimator and a full covariance analysis for the two-point galaxy-galaxy correlation function, we obtain the real-space correlation function and model it as a power law, \\xi(r) = (r/r_0)^(-\\gamma), on scales less than 10 h^{-1} Mpc. As the largest sample of blindly HI-selected galaxies to date, \\alpha.40 provides detailed understanding of the clustering of this population. We find \\gamma = 1.51 +/- 0.09 and r_0 = 3.3 +0.3, -0.2 h^{-1} Mpc, reinforcing the understanding that gas-rich galaxies represent the most weakly clustered galaxy population known; we also observe a departure from a pure power law shape at intermediate scales, as predicted in \\Lambda CDM halo occupation distribution models. Furthermore, we measure the bias parameter for the \\alpha.40 galaxy sample and find that HI galaxies are seve...

  5. The Angular Momentum of Disk Galaxies: A Multi-Wavelength Study Using the Virtual Observatory

    Science.gov (United States)

    Cortese, Luca; Catinella, B.; Springob, C. M.

    2006-12-01

    The determination of the angular momentum distribution of disk galaxies and its dependence on other galaxy properties and environment is essential in order to develop an accurate picture of galaxy formation and evolution. N-body simulations and semi-analytic models of galaxy formation within the standard cosmological framework identify the spin parameter of the dark matter halos as one of the main drivers of galaxy evolution and yield insights into its properties and distribution in present-day galaxies. Various relations have been proposed to link the halo spin parameter to observational data. In this work, we exploit such relations to obtain observational constraints for theoretical models of galaxy formation. To this extent, we used the Virtual Observatory to create a multi-wavelength database for the study of the properties of the angular momentum distribution of disk galaxies. Our sample builds upon the SFI++ database, which includes the largest collection of long-slit optical galaxy rotation curves currently available. Preliminary results of our analysis will be presented. This work is partially funded by PPARC under grant PPA/G/O/2002/00497. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation.

  6. The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts

    OpenAIRE

    Newman, Jeffrey A.; Kassin, Susan A.; Noeske, K. G.; Lotz, Jennifer M.

    2013-01-01

    We describe the design and data analysis of the DEEP2 Galaxy Redshift Survey, the densest and largest high-precision redshift survey of galaxies at z ~ 1 completed to date. The survey was designed to conduct a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude M_B = −20 at z ~ 1 via ~90 nights of observation on the Keck telescope. The survey covers an area of 2.8 deg^2 divided into four separate fields observed to a l...

  7. VizieR Online Data Catalog: New galaxies with UV excess. VI. (Kazarian+, 2005)

    Science.gov (United States)

    Kazarian, M. A.; Petrosian, G. V.

    2006-06-01

    A list is presented of 122 new galaxies with UV excess observed on plates obtained using the 40 Schmidt telescope at the Byurakan Observatory with a 1.5{deg} objective prism. It is shown that the relative number of galaxies with a strong UV excess (classes 1 and 2) listed in Table 1 is roughly 55.7%. This is 6.7% higher than for the previously observed galaxies. These samples also differ in terms of the morphology of the spectra. The largest deviation, approximately 9.9%, occurs for type sd. (1 data file).

  8. Statistical uncertainties and systematic errors in weak lensing mass estimates of galaxy clusters

    CERN Document Server

    Köhlinger, F; Eriksen, M

    2015-01-01

    Upcoming and ongoing large area weak lensing surveys will also discover large samples of galaxy clusters. Accurate and precise masses of galaxy clusters are of major importance for cosmology, for example, in establishing well calibrated observational halo mass functions for comparison with cosmological predictions. We investigate the level of statistical uncertainties and sources of systematic errors expected for weak lensing mass estimates. Future surveys that will cover large areas on the sky, such as Euclid or LSST and to lesser extent DES, will provide the largest weak lensing cluster samples with the lowest level of statistical noise regarding ensembles of galaxy clusters. However, the expected low level of statistical uncertainties requires us to scrutinize various sources of systematic errors. In particular, we investigate the bias due to cluster member galaxies which are erroneously treated as background source galaxies due to wrongly assigned photometric redshifts. We find that this effect is signifi...

  9. The Auriga Project: the properties and formation mechanisms of disc galaxies across cosmic time

    CERN Document Server

    Grand, Robert J J; Marinacci, Federico; Pakmor, Ruediger; Springel, Volker; Campbell, David J R; Frenk, Carlos S; Jenkins, Adrian; White, Simon D M

    2016-01-01

    We introduce a suite of thirty cosmological magneto-hydrodynamical zoom simulations of the formation of Milky Way-like galaxies and their dark haloes. These were carried out with the moving mesh code \\textlcsc{AREPO}, together with a comprehensive model for galaxy formation physics, including AGN feedback and magnetic fields, which produces realistic galaxy populations in large cosmological simulations. We demonstrate that our simulations reproduce a wide range of observables, in particular, two component disc dominated galaxies with appropriate stellar masses, sizes, rotation curves, star formation rates and metallicities. We investigate the driving mechanisms that set present day disc sizes/scale lengths, and find that they are related to the angular momentum of halo material. We show that the largest discs are produced by quiescent mergers that inspiral into the galaxy and deposit high angular momentum material into the pre-existing disc, simultaneously increasing the spin of dark matter and gas in the hal...

  10. The intragroup medium in loose groups of galaxies

    OpenAIRE

    Helsdon, S. F.; Ponman, T.J.

    2000-01-01

    We have used the ROSAT PSPC to study the properties of a sample of 24 X-ray bright galaxy groups, representing the largest sample examined in detail to date. Hot plasma models are fitted to the spectral data to derive temperatures, and modified King models are used to characterise the surface brightness profiles. In agreement with previous work, we find evidence for the presence of two components in the surface brightness profiles. The extended component is generally found to be much flatter ...

  11. A mathematical model of star formation in the Galaxy

    Directory of Open Access Journals (Sweden)

    M.A. Sharaf

    2012-06-01

    Full Text Available This paper is generally concerned with star formation in the Galaxy, especially blue stars. Blue stars are the most luminous, massive and the largest in radius. A simple mathematical model of the formation of the stars is established and put in computational algorithm. This algorithm enables us to know more about the formation of the star. Some real and artificial examples had been used to justify this model.

  12. Capturing molecular multimode relaxation processes in excitable gases based on decomposition of acoustic relaxation spectra

    Science.gov (United States)

    Zhu, Ming; Liu, Tingting; Wang, Shu; Zhang, Kesheng

    2017-08-01

    Existing two-frequency reconstructive methods can only capture primary (single) molecular relaxation processes in excitable gases. In this paper, we present a reconstructive method based on the novel decomposition of frequency-dependent acoustic relaxation spectra to capture the entire molecular multimode relaxation process. This decomposition of acoustic relaxation spectra is developed from the frequency-dependent effective specific heat, indicating that a multi-relaxation process is the sum of the interior single-relaxation processes. Based on this decomposition, we can reconstruct the entire multi-relaxation process by capturing the relaxation times and relaxation strengths of N interior single-relaxation processes, using the measurements of acoustic absorption and sound speed at 2N frequencies. Experimental data for the gas mixtures CO2-N2 and CO2-O2 validate our decomposition and reconstruction approach.

  13. Triple Scoop from Galaxy Hunter

    Science.gov (United States)

    2006-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] Figure 1Figure 2Figure 3 Silver Dollar Galaxy: NGC 253 (figure 1) Located 10 million light-years away in the southern constellation Sculptor, the Silver Dollar galaxy, or NGC 253, is one of the brightest spiral galaxies in the night sky. In this edge-on view from NASA's Galaxy Evolution Explorer, the wisps of blue represent relatively dustless areas of the galaxy that are actively forming stars. Areas of the galaxy with a soft golden glow indicate regions where the far-ultraviolet is heavily obscured by dust particles. Gravitational Dance: NGC 1512 and NGC 1510 (figure 2) In this image, the wide ultraviolet eyes of NASA's Galaxy Evolution Explorer show spiral galaxy NGC 1512 sitting slightly northwest of elliptical galaxy NGC 1510. The two galaxies are currently separated by a mere 68,000 light-years, leading many astronomers to suspect that a close encounter is currently in progress. The overlapping of two tightly wound spiral arm segments makes up the light blue inner ring of NGC 1512. Meanwhile, the galaxy's outer spiral arm is being distorted by strong gravitational interactions with NGC 1510. Galaxy Trio: NGC 5566, NGC 5560, and NGC 5569 (figure 3) NASA's Galaxy Evolution Explorer shows a triplet of galaxies in the Virgo cluster: NGC 5560 (top galaxy), NGC 5566 (middle galaxy), and NGC 5569 (bottom galaxy). The inner ring in NGC 5566 is formed by two nearly overlapping bright arms, which themselves spring from the ends of a central bar. The bar is not visible in ultraviolet because it consists of older stars or low mass stars that do not emit energy at ultraviolet wavelengths. The outer disk of NGC 5566 appears warped, and the disk of NGC 5560 is clearly disturbed. Unlike its galactic neighbors, the disk of NGC 5569 does not appear to have been distorted by any passing galaxies.

  14. A CLASSICAL MORPHOLOGICAL ANALYSIS OF GALAXIES IN THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S{sup 4}G)

    Energy Technology Data Exchange (ETDEWEB)

    Buta, Ronald J. [Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487-0324 (United States); Sheth, Kartik; Muñoz-Mateos, Juan-Carlos; Kim, Taehyun [National Radio Astronomy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Athanassoula, E.; Bosma, A. [Aix Marseille Universite, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France); Knapen, Johan H. [Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna (Spain); Laurikainen, Eija; Salo, Heikki; Laine, Jarkko; Comerón, Sébastien [Division of Astronomy, Department of Physical Sciences, University of Oulu, Oulu, FI-90014 (Finland); Elmegreen, Debra [Vassar College, Deparment of Physics and Astronomy, Poughkeepsie, NY 12604 (United States); Ho, Luis C. [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Zaritsky, Dennis; Hinz, Joannah L. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Courtois, Helene [Université Lyon 1, CNRS/IN2P3, Institut de Physique Nucléaire, Lyon (France); Regan, Michael W. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Gadotti, Dimitri A. [European Southern Observatory, Casilla 19001, Santiago 19 (Chile); Paz, Armando Gil de [Departmento de Astrofisica, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Menéndez-Delmestre, Karín [University of Rio de Janeiro, Observatorio de Valongo, Ladeira Pedro Antonio, 43, CEP 20080-090, Rio de Janeiro (Brazil); and others

    2015-04-15

    The Spitzer Survey of Stellar Structure in Galaxies (S{sup 4}G) is the largest available database of deep, homogeneous middle-infrared (mid-IR) images of galaxies of all types. The survey, which includes 2352 nearby galaxies, reveals galaxy morphology only minimally affected by interstellar extinction. This paper presents an atlas and classifications of S{sup 4}G galaxies in the Comprehensive de Vaucouleurs revised Hubble-Sandage (CVRHS) system. The CVRHS system follows the precepts of classical de Vaucouleurs morphology, modified to include recognition of other features such as inner, outer, and nuclear lenses, nuclear rings, bars, and disks, spheroidal galaxies, X patterns and box/peanut structures, OLR subclass outer rings and pseudorings, bar ansae and barlenses, parallel sequence late-types, thick disks, and embedded disks in 3D early-type systems. We show that our CVRHS classifications are internally consistent, and that nearly half of the S{sup 4}G sample consists of extreme late-type systems (mostly bulgeless, pure disk galaxies) in the range Scd-Im. The most common family classification for mid-IR types S0/a to Sc is SA while that for types Scd to Sm is SB. The bars in these two type domains are very different in mid-IR structure and morphology. This paper examines the bar, ring, and type classification fractions in the sample, and also includes several montages of images highlighting the various kinds of “stellar structures” seen in mid-IR galaxy morphology.

  15. Matching Supernovae to Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2016-12-01

    One of the major challenges for modern supernova surveys is identifying the galaxy that hosted each explosion. Is there an accurate and efficient way to do this that avoids investing significant human resources?Why Identify Hosts?One problem in host galaxy identification. Here, the supernova lies between two galaxies but though the centroid of the galaxy on the right is closer in angular separation, this may be a distant background galaxy that is not actually near the supernova. [Gupta et al. 2016]Supernovae are a critical tool for making cosmological predictions that help us to understand our universe. But supernova cosmology relies on accurately identifying the properties of the supernovae including their redshifts. Since spectroscopic followup of supernova detections often isnt possible, we rely on observations of the supernova host galaxies to obtain redshifts.But how do we identify which galaxy hosted a supernova? This seems like a simple problem, but there are many complicating factors a seemingly nearby galaxy could be a distant background galaxy, for instance, or a supernovas host could be too faint to spot.The authors algorithm takes into account confusion, a measure of how likely the supernova is to be mismatched. In these illustrations of low (left) and high (right) confusion, the supernova is represented by a blue star, and the green circles represent possible host galaxies. [Gupta et al. 2016]Turning to AutomationBefore the era of large supernovae surveys, searching for host galaxies was done primarily by visual inspection. But current projects like the Dark Energy Surveys Supernova Program is finding supernovae by the thousands, and the upcoming Large Synoptic Survey Telescope will likely discover hundreds of thousands. Visual inspection will not be possible in the face of this volume of data so an accurate and efficient automated method is clearly needed!To this end, a team of scientists led by Ravi Gupta (Argonne National Laboratory) has recently

  16. Time of relaxation in dusty plasma model

    Science.gov (United States)

    Timofeev, A. V.

    2015-11-01

    Dust particles in plasma may have different values of average kinetic energy for vertical and horizontal motion. The partial equilibrium of the subsystems and the relaxation processes leading to this asymmetry are under consideration. A method for the relaxation time estimation in nonideal dusty plasma is suggested. The characteristic relaxation times of vertical and horizontal motion of dust particles in gas discharge are estimated by analytical approach and by analysis of simulation results. These relaxation times for vertical and horizontal subsystems appear to be different. A single hierarchy of relaxation times is proposed.

  17. Dark-ages Reionization and Galaxy formation simulation - I. The dynamical lives of high-redshift galaxies

    Science.gov (United States)

    Poole, Gregory B.; Angel, Paul W.; Mutch, Simon J.; Power, Chris; Duffy, Alan R.; Geil, Paul M.; Mesinger, Andrei; Wyithe, Stuart B.

    2016-07-01

    We present the Dark-ages Reionization and Galaxy formation Observables from Numerical Simulations (DRAGONS) programme and Tiamat, the collisionless N-body simulation programme upon which DRAGONS is built. The primary trait distinguishing Tiamat from other large simulation programme is its density of outputs at high redshift (100 from z = 35 to z = 5; roughly one every 10 Myr) enabling the construction of very accurate merger trees at an epoch when galaxy formation is rapid and mergers extremely frequent. We find that the friends-of-friends halo mass function agrees well with the prediction of Watson et al. at high masses, but deviates at low masses, perhaps due to our use of a different halo finder or perhaps indicating a break from `universal' behaviour. We then analyse the dynamical evolution of galaxies during the Epoch of Reionization finding that only a small fraction (˜20 per cent) of galactic haloes are relaxed. We illustrate this using standard relaxation metrics to establish two dynamical recovery time-scales: (i) haloes need ˜1.5 dynamical times following formation, and (ii) ˜2 dynamical times following a major (3:1) or minor (10:1) merger to be relaxed. This is remarkably consistent across a wide mass range. Lastly, we use a phase-space halo finder to illustrate that major mergers drive long-lived massive phase-space structures which take many dynamical times to dissipate. This can yield significant differences in the inferred mass build-up of galactic haloes and we suggest that care must be taken to ensure a physically meaningful match between the galaxy formation physics of semi-analytic models and the halo finders supplying their input.

  18. Spectral properties of the largest asteroids associated with Taurid Complex

    CERN Document Server

    Popescu, M; Nedelcu, D A; Vaubaillon, J; Cristescu, C P

    2014-01-01

    We obtained spectra of six of the largest asteroids (2201, 4183, 4486, 5143, 6063, and 269690) associated with Taurid complex. The observations were made with the IRTF telescope equipped with the spectro-imager SpeX. Their taxonomic classification is made using Bus-DeMeo taxonomy. The asteroid spectra are compared with the meteorite spectra from the Relab database. Mineralogical models were applied to determine their surface composition. All the spectral analysis is made in the context of the already published physical data. Five of the objects studied in this paper present spectral characteristics similar to the S taxonomic complex. The spectra of ordinary chondrites (spanning H, L, and LL subtypes) are the best matches for these asteroid spectra. {\\bf The asteroid} (269690) 1996 RG3 presents a flat featureless spectrum which could be associated to a primitive C-type object. The increased reflectance above 2.1 microns constrains its geometrical albedo to a value around 0.03. While there is an important dynam...

  19. Largest US oil and gas fields, August 1993

    Energy Technology Data Exchange (ETDEWEB)

    1993-08-06

    The Largest US Oil and Gas Fields is a technical report and part of an Energy Information Administration (EIA) series presenting distributions of US crude oil and natural gas resources, developed using field-level data collected by EIA`s annual survey of oil and gas proved reserves. The series` objective is to provide useful information beyond that routinely presented in the EIA annual report on crude oil and natural gas reserves. These special reports also will provide oil and gas resource analysts with a fuller understanding of the nature of US crude oil and natural gas occurrence, both at the macro level and with respect to the specific subjects addressed. The series` approach is to integrate EIA`s crude oil and natural gas survey data with related data obtained from other authoritative sources, and then to present illustrations and analyses of interest to a broad spectrum of energy information users ranging from the general public to oil and gas industry personnel.

  20. Largest Particle Simulations Downgrade the Runaway Electron Risk for ITER

    CERN Document Server

    Liu, Jian; Wang, Yulei; Yang, Guangwen; Zheng, Jiangshan; Yao, Yicun; Zheng, Yifeng; Liu, Zhao; Liu, Xin

    2016-01-01

    Fusion energy will be the ultimate clean energy source for mankind. One of the most visible concerns of the future fusion device is the threat of deleterious runaway electrons (REs) produced during unexpected disruptions of the fusion plasma. Both efficient long-term algorithms and super-large scale computing power are necessary to reveal the complex dynamics of REs in a realistic fusion reactor. In the present study, we deploy the world's fastest supercomputer, Sunway TaihuLight, and the newly developed relativistic volume-preserving algorithm to carry out long-term particle simulations of 10^7 sampled REs in 6D phase space, which involves simulation scale of 10^18 particle-steps, the largest ever achieved in fusion research. Our simulations show that in a realistic fusion reactor, the concern of REs is not as serious as previously thought. Specifically, REs are confined much better than previously predicted and the maximum average energy is in the range of 150MeV, less than half of previous estimate.

  1. Radio recombination lines from the largest bound atoms in space

    CERN Document Server

    Stepkin, S V; Kantharia, N G; Shankar, N U

    2006-01-01

    In this paper, we report the detection of a series of radio recombination lines (RRLs) in absorption near 26 MHz arising from the largest bound carbon atoms detected in space. These atoms, which are more than a million times larger than the ground state atoms are undergoing delta transitions (n~1009, Delta n=4) in the cool tenuous medium located in the Perseus arm in front of the supernova remnant, Cassiopeia A. Theoretical estimates had shown that atoms which recombined in tenuous media are stable up to quantum levels n~1500. Our data indicates that we have detected radiation from atoms in states very close to this theoretical limit. We also report high signal-to-noise detections of alpha, beta and gamma transitions in carbon atoms arising in the same clouds. In these data, we find that the increase in line widths with quantum number (proportional to n^5) due to pressure and radiation broadening of lines is much gentler than expected from existing models which assume a power law background radiation field. T...

  2. Elephants have relatively the largest cerebellum size of mammals.

    Science.gov (United States)

    Maseko, Busisiwe C; Spocter, Muhammad A; Haagensen, Mark; Manger, Paul R

    2012-04-01

    The current study used MR imaging to determine the volume of the cerebellum and its component parts in the brain of three adult male African elephants (Loxodonta africana) and compared this with published data from Asian elephants and other mammalian species including odontocete cetaceans, primates, chiropterans, insectivores, carnivores, and artiodactyls. The cerebellum of the adult elephant has a volume of ∼925 mL (average of both African and Asian species). Allometric analysis indicates that the elephant has the largest relative cerebellum size of all mammals studied to date. In addition, both odontocete cetaceans and microchiropterans appear to have large relative cerebellar sizes. The vermal and hemispheric components of the African elephant cerebellum are both large relative to other mammals of similar brain size, however, for odontocete cetaceans the vermal component is small and the hemispheric component is large. These volumetric observations are related to life-histories and anatomies of the species investigated. The current study provides context for one aspect of the elephant brain in the broader picture of mammalian brain evolution. Copyright © 2012 Wiley Periodicals, Inc.

  3. Characterization of the largest effector gene cluster of Ustilago maydis.

    Directory of Open Access Journals (Sweden)

    Thomas Brefort

    2014-07-01

    Full Text Available In the genome of the biotrophic plant pathogen Ustilago maydis, many of the genes coding for secreted protein effectors modulating virulence are arranged in gene clusters. The vast majority of these genes encode novel proteins whose expression is coupled to plant colonization. The largest of these gene clusters, cluster 19A, encodes 24 secreted effectors. Deletion of the entire cluster results in severe attenuation of virulence. Here we present the functional analysis of this genomic region. We show that a 19A deletion mutant behaves like an endophyte, i.e. is still able to colonize plants and complete the infection cycle. However, tumors, the most conspicuous symptoms of maize smut disease, are only rarely formed and fungal biomass in infected tissue is significantly reduced. The generation and analysis of strains carrying sub-deletions identified several genes significantly contributing to tumor formation after seedling infection. Another of the effectors could be linked specifically to anthocyanin induction in the infected tissue. As the individual contributions of these genes to tumor formation were small, we studied the response of maize plants to the whole cluster mutant as well as to several individual mutants by array analysis. This revealed distinct plant responses, demonstrating that the respective effectors have discrete plant targets. We propose that the analysis of plant responses to effector mutant strains that lack a strong virulence phenotype may be a general way to visualize differences in effector function.

  4. LHC : The World's Largest Vacuum Systems being commissioned at CERN

    CERN Document Server

    Jiménez, J M

    2008-01-01

    When it switches on in 2008, the 26.7 km Large Hadron Collider (LHC) at CERN, will have the world's largest vacuum system operating over a wide range of pressures and employing an impressive array of vacuum technologies. This system is composed by 54 km of UHV vacuum for the circulating beams and 50 km of insulation vacuum around the cryogenic magnets and the liquid helium transfer lines. Over the 54 km of UHV beam vacuum, 48 km of this are at cryogenic temperature (1.9 K). The remaining 6 km of beam vacuum containing the insertions for "cleaning" the proton beams, radiofrequency cavities for accelerating the protons as well as beam-monitoring equipment is at ambient temperature and uses non-evaporable getter (NEG) coatings - a vacuum technology that was born and industrialized at CERN. The pumping scheme is completed using 780 ion pumps to remove noble gases and to provide pressure interlocks to the 303 vacuum safety valves. Pressure readings are provided by 170 Bayard-Alpert gauges and 1084 gauges (Pirani a...

  5. Characterization of the largest effector gene cluster of Ustilago maydis.

    Science.gov (United States)

    Brefort, Thomas; Tanaka, Shigeyuki; Neidig, Nina; Doehlemann, Gunther; Vincon, Volker; Kahmann, Regine

    2014-07-01

    In the genome of the biotrophic plant pathogen Ustilago maydis, many of the genes coding for secreted protein effectors modulating virulence are arranged in gene clusters. The vast majority of these genes encode novel proteins whose expression is coupled to plant colonization. The largest of these gene clusters, cluster 19A, encodes 24 secreted effectors. Deletion of the entire cluster results in severe attenuation of virulence. Here we present the functional analysis of this genomic region. We show that a 19A deletion mutant behaves like an endophyte, i.e. is still able to colonize plants and complete the infection cycle. However, tumors, the most conspicuous symptoms of maize smut disease, are only rarely formed and fungal biomass in infected tissue is significantly reduced. The generation and analysis of strains carrying sub-deletions identified several genes significantly contributing to tumor formation after seedling infection. Another of the effectors could be linked specifically to anthocyanin induction in the infected tissue. As the individual contributions of these genes to tumor formation were small, we studied the response of maize plants to the whole cluster mutant as well as to several individual mutants by array analysis. This revealed distinct plant responses, demonstrating that the respective effectors have discrete plant targets. We propose that the analysis of plant responses to effector mutant strains that lack a strong virulence phenotype may be a general way to visualize differences in effector function.

  6. Diverse Hispanic population to become largest U.S. minority.

    Science.gov (United States)

    1997-11-01

    High immigration rates and relatively high birth rates have made Hispanics the second fastest growing minority population in the US. Only the Asian population is growing faster. In 1996, 11% of the US's population was Hispanic. However, Hispanic Americans are projected to outnumber African Americans by 2005, and by 2050, the Hispanic population in the US is projected to total approximately 100 million, 25% of the US population and the largest of the country's ethnic minorities. Latinos have the lowest rates of high school and college graduation of any major population group in the US. Since relevant data first became available in 1972 and until 1994, the median income of Latino families has remained below that of White families, but above that of African American families. The Hispanics' median family income of $24,000 in 1995 was below that of African American families. Puerto Rican and Mexican families are most likely to be poor, while Cubans are least likely. There is considerable diversity within the US's Hispanic population. For example, some Hispanics speak only Spanish, while others speak no Spanish at all. Hispanic Americans come from many countries and cultures, making the differences between and within the Hispanic ethnic groups sometimes as great as their similarities. Most Americans do not understand that Hispanics are an ethnic group, not a racial group.

  7. Annual trauma load of the world's largest indoor skiing center.

    Science.gov (United States)

    Van Laarhoven, S N; Latten, G; de Loos, E; van Hemert, W; Vles, G F

    2017-04-01

    There is limited data on the trauma load caused by indoor skiing centers. Therefore, all patients treated at the accident and emergency department of our level I trauma center who sustained injuries at the world's largest indoor skiing center were analyzed during a 3-year period. Business intelligence was used to identify all patients who sustained injury at SnowWorld, Landgraaf, The Netherlands, and were seen at the accident and emergency department of the Zuyderland Medical Center from January 1, 2012 till December 31, 2014. Data were collected on patient characteristics, trauma mechanism, transportation, admission, diagnostics, injury and its severity, and treatment. Of the 732 patients seen, 305 had a fracture and 80 a dislocation. Most patients were male snowboarders and most injuries were sustained during winter. More than 2000 X-rays and 100 CT scans were required. Seventy-two patients were admitted and immediate surgery was performed in 21 patients. Ten patients had Injury Severity Scores of 10 or higher. Snowboarders differed significantly from skiers on several parameters, e.g., 1 in 4 snowboarders seen had sustained a distal radius fracture compared to 1 in 100 skiers. Acquiring more insight into the characteristics of this specific patient population could benefit clinical care and help clinicians identify and target preventive strategies. IV.

  8. [A Standing Balance Evaluation Method Based on Largest Lyapunov Exponent].

    Science.gov (United States)

    Liu, Kun; Wang, Hongrui; Xiao, Jinzhuang; Zhao, Qing

    2015-12-01

    In order to evaluate the ability of human standing balance scientifically, we in this study proposed a new evaluation method based on the chaos nonlinear analysis theory. In this method, a sinusoidal acceleration stimulus in forward/backward direction was forced under the subjects' feet, which was supplied by a motion platform. In addition, three acceleration sensors, which were fixed to the shoulder, hip and knee of each subject, were applied to capture the balance adjustment dynamic data. Through reconstructing the system phase space, we calculated the largest Lyapunov exponent (LLE) of the dynamic data of subjects' different segments, then used the sum of the squares of the difference between each LLE (SSDLLE) as the balance capabilities evaluation index. Finally, 20 subjects' indexes were calculated, and compared with evaluation results of existing methods. The results showed that the SSDLLE were more in line with the subjects' performance during the experiment, and it could measure the body's balance ability to some extent. Moreover, the results also illustrated that balance level was determined by the coordinate ability of various joints, and there might be more balance control strategy in the process of maintaining balance.

  9. A BRIGHTEST CLUSTER GALAXY WITH AN EXTREMELY LARGE FLAT CORE

    Energy Technology Data Exchange (ETDEWEB)

    Postman, Marc; Coe, Dan; Koekemoer, Anton; Bradley, Larry [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Lauer, Tod R. [National Optical Astronomy Observatory, P.O. Box 26732, Tucson, AZ 85726 (United States); Donahue, Megan [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Graves, Genevieve [Department of Astronomy, 601 Campbell Hall, University of California, Berkeley, CA 94720 (United States); Moustakas, John [Center for Astrophysics and Space Sciences, University of California, La Jolla, CA 92093 (United States); Ford, Holland C.; Lemze, Doron; Medezinski, Elinor [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Grillo, Claudio [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Mariesvej 30, DK-2100 Copenhagen (Denmark); Zitrin, Adi [University of Heidelberg, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Broadhurst, Tom [Department of Theoretical Physics, University of the Basque Country UPV/EHU, Bizkaia, E-48940 Leioa (Spain); Moustakas, Leonidas [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Ascaso, Begona [Instituto de Astrofisica de Andalucia (CSIC), C/Camino Bajo de Huetor 24, E-18008 Granada (Spain); Kelson, Daniel [The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2012-09-10

    Hubble Space Telescope images of the galaxy cluster A2261, obtained as part of the Cluster Lensing And Supernova survey with Hubble, show that the brightest galaxy in the cluster, A2261-BCG, has the largest core yet detected in any galaxy. The cusp radius of A2261-BCG is 3.2 kpc, twice as big as the next largest core known, and {approx}3 Multiplication-Sign bigger than those typically seen in the most luminous brightest cluster galaxies. The morphology of the core in A2261-BCG is also unusual, having a completely flat interior surface brightness profile, rather than the typical shallow cusp rising into the center. This implies that the galaxy has a core with constant or even centrally decreasing stellar density. Interpretation of the core as an end product of the 'scouring' action of a binary supermassive black hole implies a total black hole mass {approx}10{sup 10} M{sub Sun} from the extrapolation of most relationships between core structure and black hole mass. The core falls 1{sigma} above the cusp radius versus galaxy luminosity relation. Its large size in real terms, and the extremely large black hole mass required to generate it, raises the possibility that the core has been enlarged by additional processes, such as the ejection of the black holes that originally generated the core. The flat central stellar density profile is consistent with this hypothesis. The core is also displaced by 0.7 kpc from the center of the surrounding envelope, consistent with a local dynamical perturbation of the core.

  10. A "Universal" Density Profile for the Outer Stellar Halos of Galaxies

    CERN Document Server

    Remus, Rhea-Silvia; Dolag, Klaus

    2016-01-01

    The outer stellar halos of galaxies contain vital information about the formation history of galaxies, since the relaxation timescales in the outskirts are long enough to keep the memory, while the information about individual formation events in the central parts has long been lost due to mixing, star formation and relaxation. To unveil some of the information encoded in these faint outer halo regions, we study the stellar outskirts of galaxies selected from a fully hydrodynamical high resolution cosmological simulation, called Magneticum. We find that the density profiles of the outer stellar halos of galaxies over a broad mass range can be well described by an Einasto profile. For a fixed total mass range, the free parameters of the Einasto fits are closely correlated. Galaxies which had more (dry) merger events tend to have lesser curved outer stellar halos, however, we find no indication that the amount of curvature is correlated with galaxy morphology. The Einasto-like shape of the outer stellar halo de...

  11. Two-body relaxation in modified Newtonian dynamics

    CERN Document Server

    Ciotti, L

    2004-01-01

    A naive extension to MOND of the standard computation of the two-body relaxation time Tb implies that Tb is comparable to the crossing time regardless of the number N of stars in the system. This computation is questionable in view of the non-linearity of MOND's field equation. A non-standard approach to the calculation of Tb is developed that can be extended to MOND whenever discreteness noise generates force fluctuations that are small compared to the mean-field force. It is shown that this approach yields standard Newtonian results for systems in which the mean density profile is either plane-parallel or spherical. In the plane-parallel case we find that in the deep-MOND regime Tbb scales with N as in the Newtonian case, but is shorter by the square of the factor by which MOND enhances the gravitational force over its Newtonian value for the same system. Application of these results to dwarf galaxies and groups and clusters of galaxies reveals that in MOND luminosity segregation should be far advanced in g...

  12. 5 Things To Know About Relaxation Techniques for Stress

    Science.gov (United States)

    ... X Y Z 5 Things To Know About Relaxation Techniques for Stress Share: When you’re under stress, ... creating the relaxation response through regular use of relaxation techniques could counteract the negative effects of stress. Relaxation ...

  13. How environment drives galaxy evolution: lessons learnt from satellite galaxies

    CERN Document Server

    Pasquali, A

    2015-01-01

    It is by now well established that galaxy evolution is driven by intrinsic and environmental processes, both contributing to shape the observed properties of galaxies. A number of early studies, both observational and theoretical, have shown that the star formation activity of galaxies depends on their environmental local density and also on galaxy hierarchy, i.e. centrals vs. satellites. In fact, contrary to their central (most massive) galaxy of a group/cluster, satellite galaxies are stripped of their gas and stars, and have their star formation quenched by their environment. Large galaxy surveys like SDSS now permit us to investigate in detail environment-driven transformation processes by comparing centrals and satellites. In this paper I summarize what we have so far learnt about environmental effects by analysing the observed properties of local central and satellite galaxies in SDSS, as a function of their stellar mass and the dark matter mass of their host group/cluster.

  14. Stratification at the Earth's largest hyperacidic lake and its consequences

    Science.gov (United States)

    Caudron, Corentin; Campion, Robin; Rouwet, Dmitri; Lecocq, Thomas; Capaccioni, Bruno; Syahbana, Devy; Suparjan; Purwanto, Bambang Heri; Bernard, Alain

    2017-02-01

    Volcanic lakes provide windows into the interior of volcanoes as they integrate the heat flux discharged by a magma body and condense volcanic gases. Volcanic lake temperatures and geochemical compositions therefore typically serve as warnings for resumed unrest or prior to eruptions. If acidic and hot, these lakes are usually considered to be too convective to allow any stratification within their waters. Kawah Ijen volcano, featuring the largest hyperacidic lake on Earth (volume of 27 million m3), is less homogeneous than previously thought. Hourly temperature measurements reveal the development of a stagnant layer of cold waters (<30 °C), overlying warmer and denser water (generally above 30 °C and density ∼1.083 kg/m3). Examination of 20 yrs of historical records and temporary measurements show a systematic thermal stratification during rainy seasons. The yearly rupture of stratification at the end of the rainy season causes a sudden release of dissolved gases below the cold water layer which appears to generate a lake overturn, i.e. limnic eruption, and a resonance of the lake, i.e. a seiche, highlighting a new hazard for these extreme reservoirs. A minor non-volcanic event, such as a heavy rainfall or an earthquake, may act as a trigger. The density driven overturn requires specific salinity-temperature conditions for the colder and less saline top water layer to sink into the hot saline water. Spectacular degassing occurs when the dissolved gases, progressively stored during the rainy season due to a weakened diffusion of carbon dioxide in the top layer, are suddenly released. These findings challenge the homogenization assumption at acidic lakes and stress the need to develop appropriate monitoring setups.

  15. Liver retransplantation in adults: the largest multicenter Italian study.

    Directory of Open Access Journals (Sweden)

    Umberto Maggi

    Full Text Available This study is the largest Italian survey on liver retransplantations (RET. Data report on 167 adult patients who received 2 grafts, 16 who received 3 grafts, and one who received 4 grafts over a 11 yr period.There was no statistically significant difference in graft survival after the first or the second RET (52, 40, and 29% vs 44, 36, and 18% at 1,5,and 10 yr, respectively: Log-Rank test, p = 0.30.Survivals at 1, 5, and 10 years of patients who underwent 2 (n = 151 or 3 (n = 15 RETs, were 65, 48,and 39% vs 59, 44, and 30%, respectively (p = 0.59.Multivariate analysis of survival showed that only the type of graft (whole vs reduced was associated with a statistically significant difference (HR = 3.77, Wald test p = 0. 05; the donor age appeared to be a relevant factor as well, although the difference was not statistically significant (HR = 1.91, Wald test p = 0.08.Though late RETs have better results on long term survival relative to early RETs, no statistically significant difference can be found in early results, till three years after RET.Considering late first RETs (interval>30 days from previous transplantation with whole grafts the difference in graft survival in RETs due to HCV recurrence (n = 17 was not significantly different from RETs due to other causes (n = 53 (65-58 and 31% vs 66-57 and 28% respectively at 1-5 and 10 years, p = 0.66.

  16. Global assessment of nutrient loads to the world's largest lakes

    Science.gov (United States)

    Fink, Gabriel; Reder, Klara; Malsy, Marcus; Eisner, Stephanie; Flörke, Martina

    2015-04-01

    Lakes are essential resources of drinking water for a large part of mankind. Even so, most of the industrial and domestic waste water is discharged - often untreated - into rivers and streams that are finally the tributaries of these important freshwater bodies. Additionally, diffuse nutrient sources such as fertilizer and atmospheric deposition exacerbate existing algal blooms and low oxygen concentrations in rivers, lakes, and reservoirs. In this tense atmosphere of competing water uses, it is necessary to analyze all sources of pollution as well as their total contributions in order to protect these water bodies against deterioration. Finally, this is a general and urgently needed basis for developing recommendations for involved stakeholders and decision makers. Therefore, the project eartH2Observe, initiated and financed by the European Commission, creates the necessary and underlying quantitative and qualitative hydrological and water use data. In this context, information for global as well as for regional water resource assessments is being prepared based on new earth observations and an ensemble of global hydrological models. As a member of this ensemble, WaterGAP3 provides global estimates of lake water quality relevant parameters on a 5 arc minutes grid, namely total phosphorus and total nitrogen. These nutrient loads to lakes from different sources such as industrial fertilizer, organic fertilizer, domestic loads, atmospheric deposition, and urban surface runoff are estimated for the period 1990 to 2010 in a monthly time step. Whereas nutrient loads and their changes into numerous lakes worldwide are calculated, a special focus is set on nutrient loads into the large and shallow Lake Peipus, which is located between Estonia and Russia and subject to blooms of harmful cyanobacteria. We present estimates, trends, as well as sources of present nutrient loads (TN and TP) to the world's largest lakes with detailed insights to the Lake Peipus situation

  17. Bayesian approaches to infer the physical properties of star-forming galaxies at cosmic dawn

    Science.gov (United States)

    Salmon, Brett Weston Killebrew

    In this thesis, I seek to advance our understanding of galaxy formation and evolution in the early universe. Using the largest single project ever conducted by the Hubble Space Telescope (the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, CANDELS) I use deep and wide broadband photometric imaging to infer the physical properties of galaxies from z=8.5 to z=1.5. First, I will present a study that extends the relationship between the star-formation rates (SFRs) and stellar masses (M⋆) of galaxies to 3.5attenuated in galaxies. I calculate the Bayesian evidence for galaxies under different assumptions of their underlying dust-attenuation law. By modeling galaxy ultraviolet-to-near-IR broadband CANDELS data I produce Bayesian evidence towards the dust law in individual galaxies that is confirmed by their observed IR luminosities. Moreover, I find a tight correlation between the strength of attenuation in galaxies and their dust law, a relation reinforced by the results from radiative transfer simulations. Finally, I use the Bayesian methods developed in this thesis to study the number density of SFR in galaxies from z=8 to z=4, and resolve the current disconnect between its evolution and that of the stellar mass function. In doing so, I place the first constraints on the dust law of z>4 galaxies, finding it obeys a similar relation as found at z˜2. I find a clear excess in number density at high SFRs. This new SFR function is in better agreement with the observed stellar mass functions, the few to-date infrared detections at high redshifts, and the connection to the observed distribution of lower redshift infrared sources. Together, these studies greatly improve our understanding of the galaxy star-formation histories, the nature of their dust attenuation, and the distribution of SFR among some of the most distant galaxies in the universe.

  18. The Evolution of Post-starburst Galaxies from z ~ 1 to the Present

    Science.gov (United States)

    Pattarakijwanich, Petchara; Strauss, Michael A.; Ho, Shirley; Ross, Nicholas P.

    2016-12-01

    Post-starburst galaxies are in the transitional stage between blue, star-forming galaxies and red, quiescent galaxies and therefore hold important clues for our understanding of galaxy evolution. In this paper, we systematically searched for and identified a large sample of post-starburst galaxies from the spectroscopic data set of the Sloan Digital Sky Survey (SDSS) Data Release 9. In total, we found more than 6000 objects with redshifts between z ˜ 0.05 and z ˜ 1.3, making this the largest sample of post-starburst galaxies in the literature. We calculated the luminosity function of the post-starburst galaxies using two uniformly selected subsamples: the SDSS main galaxy sample and the Baryon Oscillation Spectroscopic Survey CMASS sample. The luminosity functions are reasonably fit by half-Gaussian functions. The peak magnitudes shift as a function of redshift from M ˜ -23.5 at z ˜ 0.8 to M ˜ -20.3 at z ˜ 0.1. This is consistent with the downsizing trend, whereby more massive galaxies form earlier than low-mass galaxies. We compared the mass of the post-starburst stellar population found in our sample to the decline of the global star formation rate and found that only a small amount (˜1%) of all star formation quenching in the redshift range z = 0.2-0.7 results in post-starburst galaxies in the luminosity range our sample is sensitive to. Therefore, luminous post-starburst galaxies are not the place where most of the decline in the star formation rate of the universe is happening.

  19. ALMA Explores How Supermassive Black Holes Talk to Their Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2017-03-01

    We believe that supermassive black holes evolve in tandem with their host galaxies but how do the two communicate? Observations from the Atacama Large Millimeter/submillimeter Array (ALMA) have revealed new clues about how a monster black hole talks to its galaxy.A Hubble image of the central galaxy in the Phoenix cluster. [Adapted from Russell et al. 2017]Observing FeedbackActive galactic nuclei (AGN), the highly luminous centers of some galaxies, are thought to radiate due to active accretion onto the supermassive black hole at their center.Its long been suspected that the radiation and outflowing material which often takes the form of enormous bipolar radio jets emitted into the surroundings influence the AGNs host galaxy, affecting star formation rates and the evolution of the galaxy. This AGN feedback has been alternately suggested to trigger star formation, quench it, and truncate the growth of massive galaxies.The details of this feedback process, however, have yet to be thoroughly understood in part because its difficult to obtain detailed observations of how AGN outflows interact with the galactic gas surrounding them. Now, a team of scientists led by Helen Russell (Institute of Astronomy in Cambridge, UK) has published the results of a new, high-resolution look at the gas in a massive galaxy in the center of the Phoenix cluster.Many Uses for FuelThe Phoenix cluster, a nearby (z = 0.596) group of star-forming galaxies, is the most luminous X-ray cluster known. The central galaxy in the cluster is especially active: it hosts a starburst of 500800 solar masses per year, the largest starburst found in any galaxy below a redshift of z= 1.The star formation in this galaxy is sustained by an enormous reservoir of cold molecular gas roughly 20 billion solar masses worth. This reservoir also powers the galaxys central black hole, fueling powerful radio jets that extend into the hot atmosphere of the galaxy and blow a giant bubble into the hot gas at each pole

  20. Compaction and relaxation of biofilms

    KAUST Repository

    Valladares Linares, R.

    2015-06-18

    Operation of membrane systems for water treatment can be seriously hampered by biofouling. A better characterization of biofilms in membrane systems and their impact on membrane performance may help to develop effective biofouling control strategies. The objective of this study was to determine the occurrence, extent and timescale of biofilm compaction and relaxation (decompaction), caused by permeate flux variations. The impact of permeate flux changes on biofilm thickness, structure and stiffness was investigated in situ and non-destructively with optical coherence tomography using membrane fouling monitors operated at a constant crossflow velocity of 0.1 m s−1 with permeate production. The permeate flux was varied sequentially from 20 to 60 and back to 20 L m−2 h−1. The study showed that the average biofilm thickness on the membrane decreased after elevating the permeate flux from 20 to 60 L m−2 h−1 while the biofilm thickness increased again after restoring the original flux of 20 L m−2 h−1, indicating the occurrence of biofilm compaction and relaxation. Within a few seconds after the flux change, the biofilm thickness was changed and stabilized, biofilm compaction occurred faster than the relaxation after restoring the original permeate flux. The initial biofilm parameters were not fully reinstated: the biofilm thickness was reduced by 21%, biofilm stiffness had increased and the hydraulic biofilm resistance was elevated by 16%. Biofilm thickness was related to the hydraulic biofilm resistance. Membrane performance losses are related to the biofilm thickness, density and morphology, which are influenced by (variations in) hydraulic conditions. A (temporarily) permeate flux increase caused biofilm compaction, together with membrane performance losses. The impact of biofilms on membrane performance can be influenced (increased and reduced) by operational parameters. The article shows that a (temporary) pressure increase leads to more

  1. Plasma Relaxation in Hall Magnetohydrodynamics

    CERN Document Server

    Shivamoggi, B K

    2011-01-01

    Parker's formulation of isotopological plasma relaxation process in magnetohydrodynamics (MHD) is extended to Hall MHD. The torsion coefficient alpha in the Hall MHD Beltrami condition turns out now to be proportional to the "potential vorticity." The Hall MHD Beltrami condition becomes equivalent to the "potential vorticity" conservation equation in two-dimensional hydrodynamics if the Hall MHD Lagrange multiplier beta is taken to be proportional to the "potential vorticity" as well. The winding pattern of the magnetic field lines in Hall MHD then appears to evolve in the same way as "potential vorticity" lines in 2D hydrodynamics.

  2. Spectral Estimation of NMR Relaxation

    Science.gov (United States)

    Naugler, David G.; Cushley, Robert J.

    2000-08-01

    In this paper, spectral estimation of NMR relaxation is constructed as an extension of Fourier Transform (FT) theory as it is practiced in NMR or MRI, where multidimensional FT theory is used. nD NMR strives to separate overlapping resonances, so the treatment given here deals primarily with monoexponential decay. In the domain of real error, it is shown how optimal estimation based on prior knowledge can be derived. Assuming small Gaussian error, the estimation variance and bias are derived. Minimum bias and minimum variance are shown to be contradictory experimental design objectives. The analytical continuation of spectral estimation is constructed in an optimal manner. An important property of spectral estimation is that it is phase invariant. Hence, hypercomplex data storage is unnecessary. It is shown that, under reasonable assumptions, spectral estimation is unbiased in the context of complex error and its variance is reduced because the modulus of the whole signal is used. Because of phase invariance, the labor of phasing and any error due to imperfect phase can be avoided. A comparison of spectral estimation with nonlinear least squares (NLS) estimation is made analytically and with numerical examples. Compared to conventional sampling for NLS estimation, spectral estimation would typically provide estimation values of comparable precision in one-quarter to one-tenth of the spectrometer time when S/N is high. When S/N is low, the time saved can be used for signal averaging at the sampled points to give better precision. NLS typically provides one estimate at a time, whereas spectral estimation is inherently parallel. The frequency dimensions of conventional nD FT NMR may be denoted D1, D2, etc. As an extension of nD FT NMR, one can view spectral estimation of NMR relaxation as an extension into the zeroth dimension. In nD NMR, the information content of a spectrum can be extracted as a set of n-tuples (ω1, … ωn), corresponding to the peak maxima

  3. Relaxing Chosen-Ciphertext Security

    DEFF Research Database (Denmark)

    Canetti, Ran; Krawczyk, Hugo; Nielsen, Jesper Buus

    2003-01-01

    Security against adaptive chosen ciphertext attacks (or, CCA security) has been accepted as the standard requirement from encryption schemes that need to withstand active attacks. In particular, it is regarded as the appropriate security notion for encryption schemes used as components within...... “for most practical purposes.” We propose a relaxed variant of CCA security, called Replayable CCA (RCCA) security. RCCA security accepts as secure the non-CCA (yet arguably secure) schemes mentioned above; furthermore, it suffices for most existing applications of CCA security. We provide three...

  4. Shocks and cold fronts in galaxy clusters

    CERN Document Server

    Markevitch, M L; Markevitch, Maxim; Vikhlinin, Alexey

    2007-01-01

    The currently operating X-ray imaging observatories provide us with an exquisitely detailed view of the Megaparsec-scale plasma atmospheres in nearby galaxy clusters. At z < 0.05, the Chandra's 1" angular resolution corresponds to linear resolution of less than a kiloparsec, which is smaller than some interesting linear scales in the intracluster plasma. This enables us to study the previously unseen hydrodynamic phenomena in clusters: classic bow shocks driven by the infalling subclusters, and the unanticipated "cold fronts," or sharp contact discontinuities between regions of gas with different entropies. The ubiquitous cold fronts are found in mergers as well as around the central density peaks in "relaxed" clusters. They are caused by motion of cool, dense gas clouds in the ambient higher-entropy gas. These clouds are either remnants of the infalling subclusters, or the displaced gas from the cluster's own cool cores. Both shock fronts and cold fronts provide novel tools to study the intracluster plasm...

  5. Galaxies et trous noirs supermassifs

    Science.gov (United States)

    Collin-Zahn, Suzy

    2016-08-01

    A few percents of galaxies are classified as « active ». An active galaxy is a galaxy whose nucleus emits more energy than the whole galaxy in the form of electromagnetic radiation, relativistic particles, or mechanical energy. It is activated by a supermassive black hole fueled by matter falling on it, whose characteristics (Eddington luminosity, spin) are recalled. The class includes quasars and Seyfert galaxies. All massive "non active" galaxies contain a supermassive black hole, but there is not enough matter in its environment so as the nucleus becomes luminous. Different items are considered in the paper : how supermassive black holes are fueled, the accretion disc, the jets and the winds, the unified model of active galaxies, how are determined the masses of supermassive black holes, and what is the relation between the evolution of galaxies and supermassive black holes.

  6. Tidal alignment of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Blazek, Jonathan; Vlah, Zvonimir; Seljak, Uroš

    2015-08-01

    We develop an analytic model for galaxy intrinsic alignments (IA) based on the theory of tidal alignment. We calculate all relevant nonlinear corrections at one-loop order, including effects from nonlinear density evolution, galaxy biasing, and source density weighting. Contributions from density weighting are found to be particularly important and lead to bias dependence of the IA amplitude, even on large scales. This effect may be responsible for much of the luminosity dependence in IA observations. The increase in IA amplitude for more highly biased galaxies reflects their locations in regions with large tidal fields. We also consider the impact of smoothing the tidal field on halo scales. We compare the performance of this consistent nonlinear model in describing the observed alignment of luminous red galaxies with the linear model as well as the frequently used "nonlinear alignment model," finding a significant improvement on small and intermediate scales. We also show that the cross-correlation between density and IA (the "GI" term) can be effectively separated into source alignment and source clustering, and we accurately model the observed alignment down to the one-halo regime using the tidal field from the fully nonlinear halo-matter cross correlation. Inside the one-halo regime, the average alignment of galaxies with density tracers no longer follows the tidal alignment prediction, likely reflecting nonlinear processes that must be considered when modeling IA on these scales. Finally, we discuss tidal alignment in the context of cosmic shear measurements.

  7. Hyperluminous Infrared Galaxies

    CERN Document Server

    Rowan-Robinson, M

    1999-01-01

    (39) galaxies are now known, from follow-up of faint IRAS sources and from submm observations of high redshift AGN, with far infrared luminosities > 10^{13} Lo. 13 of these, which have been found in 60 or 850 mu surveys, form an important unbiased sub-sample. 12 have been found by comparison of 60 mu surveys with quasar or radio-galaxy catalogues, or from infrared surveys with colour selection biased towards AGN, while a further 14 have been found through submm observations of known high redshift AGN. In this paper I argue, on the basis of detailed modelling of the spectral energy distributions of hyperluminous galaxies with accurate radiative transfer models, and from evidence of high gas-mass in several cases, that the bulk of the emission from these galaxies at rest-frame wavelengths >= 50 mu is due to star formation. Even after correction for the effects of lensing, hyperluminous galaxies with emission peaking at rest-frame wavelengths >= 50 mu are therefore undergoing star-formation at rates > 1000 Mo/yr...

  8. Lopsided Spiral Galaxies

    CERN Document Server

    Jog, Chanda J

    2008-01-01

    The light distribution in the disks of many galaxies is non-axisymmetric or `lopsided' with a spatial extent much larger along one half of a galaxy than the other, as in M101. Recent near-IR observations show that lopsidedness is common. The stellar disks in nearly 30 % of galaxies have significant lopsidedness, greater than 10 % measured as the Fourier amplitude of the m=1 component normalized to the average value. This asymmetry is traced particularly well by the atomic hydrogen gas distribution lying in the outer parts. The lopsidedness also occurs in the nuclear regions, where the nucleus is offset with respect to the outer isophotes. The galaxies in a group environment show higher lopsidedness. The origin of lopsidedness could be due to the disk response to a tidally distorted halo, or via gas accretion. The lopsidedness has a large impact on the dynamics of the galaxy, its evolution, the star formation in it, and on the growth of the central black hole and on the nuclear fueling, merging of binary black...

  9. HOW DO STAR-FORMING GALAXIES AT z > 3 ASSEMBLE THEIR MASSES?

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kyoung-Soo [Department of Physics and Astronomy, Yale Center for Astronomy and Astrophysics, Yale University, New Haven, CT 06520 (United States); Ferguson, Henry C.; Dahlen, Tomas; Grogin, Norman [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Wiklind, Tommy [ALMA/ESO, Santiago (Chile); Dickinson, Mark E. [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States); Giavalisco, Mauro; Guo, Yicheng [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Papovich, Casey [Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Messias, Hugo [Departamento de Astronomia, Av. Esteban Iturra 6to piso, Facultad de Ciencias Fisicas y Matematicas, Universidad de Concepcion (Chile); Lin, Lihwai [Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 106, Taiwan (China)

    2012-06-10

    We investigate how star-forming galaxies typically assemble their masses at high redshift. Taking advantage of the deep multi-wavelength coverage of the GOODS data set, we select two of the largest samples of high-redshift star-forming galaxies based on their UV colors and measure stellar mass of individual galaxies. We use template-fitting photometry to obtain optimal estimates of the fluxes in lower-resolution ground-based and Spitzer images using prior information about galaxy positions, shapes, and orientations. By combining the data and realistic simulations to understand measurement errors and biases, we make a statistically robust determination of stellar mass function (SMF) of the UV-selected star-forming galaxies at z {approx} 4 and 5. We report a broad correlation between stellar mass and UV luminosity, such that more UV-luminous galaxies are, on average, also more massive. However, we show that the correlation has a substantial intrinsic scatter, particularly for UV-faint galaxies, evidenced by the fact there is a non-negligible number of UV faint but massive galaxies. Furthermore, we find that the low-mass end of the SMF does not rise as steeply as the UV luminosity function ({alpha}{sub UVLF} Almost-Equal-To - (1.7-1.8) while {alpha}{sub SMF} Almost-Equal-To - (1.3-1.4)) of the same galaxies. In a smooth and continuous formation scenario where star formation rates (SFRs) are sustained at the observed rates for a long time, these galaxies would have accumulated more stellar mass (by a factor of Almost-Equal-To 3) than observed and therefore the SMF would mirror more closely that of the UV luminosity function. The relatively shallow slope of the SMF is due to the fact that many of the UV-selected galaxies are not massive enough, and therefore are too faint in their rest-frame optical bands, to be detected in the current observations. Our results favor a more episodic formation history in which SFRs of low-mass galaxies vary significantly over cosmic time

  10. GIS learning tool for world's largest earthquakes and their causes

    Science.gov (United States)

    Chatterjee, Moumita

    The objective of this thesis is to increase awareness about earthquakes among people, especially young students by showing the five largest and two most predictable earthquake locations in the world and their plate tectonic settings. This is a geographic based interactive tool which could be used for learning about the cause of great earthquakes in the past and the safest places on the earth in order to avoid direct effect of earthquakes. This approach provides an effective way of learning for the students as it is very user friendly and more aligned to the interests of the younger generation. In this tool the user can click on the various points located on the world map which will open a picture and link to the webpage for that point, showing detailed information of the earthquake history of that place including magnitude of quake, year of past quakes and the plate tectonic settings that made this place earthquake prone. Apart from knowing the earthquake related information students will also be able to customize the tool to suit their needs or interests. Students will be able to add/remove layers, measure distance between any two points on the map, select any place on the map and know more information for that place, create a layer from this set to do a detail analysis, run a query, change display settings, etc. At the end of this tool the user has to go through the earthquake safely guidelines in order to be safe during an earthquake. This tool uses Java as programming language and uses Map Objects Java Edition (MOJO) provided by ESRI. This tool is developed for educational purpose and hence its interface has been kept simple and easy to use so that students can gain maximum knowledge through it instead of having a hard time to install it. There are lots of details to explore which can help more about what a GIS based tool is capable of. Only thing needed to run this tool is latest JAVA edition installed in their machine. This approach makes study more fun and

  11. Genome size analyses of Pucciniales reveal the largest fungal genomes

    Directory of Open Access Journals (Sweden)

    Silvia eTavares

    2014-08-01

    Full Text Available Rust fungi (Basidiomycota, Pucciniales are biotrophic plant pathogens which exhibit diverse complexities in their life cycles and host ranges. The completion of genome sequencing of a few rust fungi has revealed the occurrence of large genomes. Sequencing efforts for other rust fungi have been hampered by uncertainty concerning their genome sizes. Flow cytometry was recently applied to estimate the genome size of a few rust fungi, and confirmed the occurrence of large genomes in this order (averaging 151.5 Mbp, while the average for Basidiomycota was 49.9 Mbp and was 37.7 Mbp for all fungi. In this work, we have used an innovative and simple approach to simultaneously isolate nuclei from the rust and its host plant in order to estimate the genome size of 30 rust species by flow cytometry. Genome sizes varied over 10-fold, from 70 to 893 Mbp, with an average genome size value of 380.2 Mbp. Compared to the genome sizes of over 1,800 fungi, Gymnosporangium confusum possesses the largest fungal genome ever reported (893.2 Mbp. Moreover, even the smallest rust genome determined in this study is larger than the vast majority of fungal genomes (94 %. The average genome size of the Pucciniales is now of 305.5 Mbp, while the average Basidiomycota genome size has shifted to 70.4 Mbp and the average for all fungi reached 44.2 Mbp. Despite the fact that no correlation could be drawn between the genome sizes, the phylogenomics or the life cycle of rust fungi, it is interesting to note that rusts with Fabaceae hosts present genomes clearly larger than those with Poaceae hosts. Although this study comprises only a small fraction of the more than 7,000 rust species described, it seems already evident that the Pucciniales represent a group where genome size expansion could be a common characteristic. This is in sharp contrast to sister taxa, placing this order in a relevant position in fungal genomics research.

  12. Can A Galaxy Redshift Survey Measure Dark Energy Clustering?

    CERN Document Server

    Takada, M

    2006-01-01

    (abridged) A wide-field galaxy redshift survey allows one to probe galaxy clustering at largest spatial scales, which carries an invaluable information on horizon-scale physics complementarily to the cosmic microwave background (CMB). Assuming the planned survey consisting of z~1 and z~3 surveys with areas of 2000 and 300 square degrees, respectively, we study the prospects for probing dark energy clustering from the measured galaxy power spectrum, assuming the dynamical properties of dark energy are specified in terms of the equation of state and the effective sound speed c_e in the context of an adiabatic cold dark matter (CDM) model. The dark energy clustering adds a power to the galaxy power spectrum amplitude at spatial scales greater than the sound horizon, and the enhancement is sensitive to redshift evolution of the net dark energy density, i.e. the equation of state. We find that the galaxy survey, when combined with Planck, can distinguish dark energy clustering from a smooth dark energy model such ...

  13. Supermassive black holes and their host spheroids I. Galaxy vivisection

    CERN Document Server

    Savorgnan, Giulia A D

    2015-01-01

    Several recent studies have performed galaxy decompositions to investigate correlations between the black hole mass and various properties of the host spheroid, but they have not converged on the same conclusions. This is because their models for the same galaxy were often significantly different and not consistent with each other in terms of fitted components. Using $3.6 \\rm ~\\mu m$ $Spitzer$ imagery, which is a superb tracer of the stellar mass (superior to the $K$-band), we have performed state-of-the-art multicomponent decompositions for 66 galaxies with directly measured black hole masses. Our sample is the largest to date and, unlike previous studies, contains a large number (17) of spiral galaxies with low black hole masses. We paid careful attention to the image mosaicking, sky subtraction and masking of contaminating sources. After a scrupulous inspection of the galaxy photometry (through isophotal analysis and unsharp masking) and - for the first time - 2D kinematics, we were able to account for sph...

  14. The Local Tully–Fisher Relation for Dwarf Galaxies

    Science.gov (United States)

    Karachentsev, Igor D.; Kaisina, Elena I.; Kashibadze (Nasonova, Olga G.

    2017-01-01

    We study different incarnations of the Tully–Fisher (TF) relation for the Local Volume (LV) galaxies taken from Updated Nearby Galaxy Catalog. The UNGC sample contains 656 galaxies with W50 H i-line-width estimates, mostly belonging to low-mass dwarfs. Of them, 296 objects have distances measured with accuracies better than 10%. For the sample of 331 LV galaxies having baryonic masses {log}{M}{bar}> 5.8{log} {M}ȯ , we obtain a relation {log}{M}{bar}=2.49{log}{W}50+3.97 with an observed scatter of 0.38 dex. The largest factors affecting the scatter are observational errors in K-band magnitudes and W50 line widths for the tiny dwarfs, as well as uncertainty of their inclinations. We find that accounting for the surface brightness of the LV galaxies or their gas fraction, specific star-formation rate, or isolation index does not essentially reduce the observed scatter on the baryonic TF diagram. We also notice that a sample of 71 dSph satellites of the Milky Way and M31 with a known stellar velocity dispersion σ* tends to follow nearly the same bTF relation, having slightly lower masses than that of late-type dwarfs.

  15. The local Tully-Fisher relation for dwarf galaxies

    CERN Document Server

    Karachentsev, Igor D; Kashibadze, Olga G

    2016-01-01

    We study different incarnations of the Tully-Fisher (TF) relation for the Local Volume (LV) galaxies taken from Updated Nearby Galaxy Catalog. The UNGC sample contains 656 galaxies with $W_{50}$ HI-line-width estimates, mostly belonging to low mass dwarfs. Of them, 296 objects have distances measured with accuracy better than 10%. For the sample of 331 LV galaxies having baryonic masses $\\log M_{bar} > 5.8 \\log M_\\odot$ we obtain a relation $\\log M_{bar}= 2.49 \\log W_{50} + 3.97$ with observed scatter of 0.38 dex. The largest factors affecting the scatter are observational errors in $K$-band magnitudes and $W_{50}$ line widths for the tiny dwarfs, as well as uncertainty of their inclinations. We find that accounting for the surface brightness of the LV galaxies, or their gas fraction, or specific star formation rate, or the isolation index do not reduce essentially the observed scatter on the baryonic TF-diagram. We also notice that a sample of 71 dSph satellites of the Milky Way and M31 with known stellar ve...

  16. Statistical approach to the theory of galaxy formation

    Energy Technology Data Exchange (ETDEWEB)

    Doroshkevich, A.G.; Shandarin, S.F.

    1978-11-01

    Some topics concerning the development of galaxies and clusters of galaxies from random adiabatic irregularities are discussed. The perturbations would grow according to the nonlinear theory of gravitational instability, wherein the maxima of the largest principle value lambdaatsub llat of the deformation tensor partialS/sub i//partialq/sub k/ act as singular points. Dense, flattened, pancake-shaped structures would begin to form near these points, and would later evolve into galaxies and galaxy clusters. Parameters of an individual pancake such as its epoch of origin, mass, and temperature will be governed by the value of lambdaatsub llat at the center of the pancake. The distribution function of lambdaatsub llat is derived, and the rate of mass condensation into pancakes as well as the birth rate and space density of pancakes are determined. The statistical properties of individual pancakes are established, including the mean displacement and its dispersion in the neighborhood of the center of the pancake. The analogous characteristics of the deformation tensor and parameters describing the shape of the pancake are given. Possible relationships between young galaxies and quasars are considered from the standpoint of this theory.

  17. The Ubiquity of Coeval Starbursts in Massive Galaxy Cluster Progenitors

    CERN Document Server

    Casey, Caitlin M

    2016-01-01

    The Universe's largest galaxy clusters likely built the majority of their massive $>10^{11} M_\\odot$ galaxies in simultaneous, short-lived bursts of activity well before virialization. This conclusion is reached from emerging datasets on $z>2$ proto-clusters and the characteristics of their member galaxies, in particular, rare starbursts and ultraluminous active galactic nuclei (AGN). The most challenging observational hurdle in identifying such structures is their very large volumes, $\\sim10^{4}$ comoving Mpc$^3$ at $z>2$, subtending areas $\\sim$half a degree on the sky. Thus the contrast afforded by an overabundance of very rare galaxies in comparison to the background can more easily distinguish overdense structures from the surrounding, normal density field. Five $210^{15} M_\\odot$ galaxy clusters in the nearby Universe, a factor of five larger than expected in some simulations. Some tension yet exists between measurements of their volume density of starburst-rich proto-clusters and the expectation that t...

  18. Contribution of Lensed SCUBA Galaxies to the Cosmic Infrared Background

    Science.gov (United States)

    Zemcov, Michael; Blain, Andrew; Halpern, Mark; Levenson, Louis

    2010-09-01

    The surface density of submillimeter (sub-mm) galaxies as a function of flux, usually termed the source number counts, constrains models of the evolution of the density and luminosity of starburst galaxies. At the faint end of the distribution, direct detection and counting of galaxies are not possible. However, gravitational lensing by clusters of galaxies allows detection of sources which would otherwise be too dim to study. We have used the largest catalog of sub-mm-selected sources along the line of sight to galaxy clusters to estimate the faint end of the 850 μm number counts; integrating to S = 0.10 mJy, the equivalent flux density at 850 μm is νI ν = 0.24 ± 0.03 nW m-2 sr-1. This provides a lower limit to the extragalactic far-infrared background and is consistent with direct estimates of the full intensity from the FIRAS. The results presented here can help to guide strategies for upcoming surveys carried out with single-dish sub-mm instruments.

  19. Contribution of Lensed SCUBA Galaxies to the Cosmic Infrared Background

    CERN Document Server

    Zemcov, M; Halpern, M; Levenson, L

    2010-01-01

    The surface density of sub-millimeter galaxies as a function of flux, usually termed the source number counts, constrains models of the evolution of the density and luminosty of starburst galaxies. At the faint end of the distribution, direct detection and counting of galaxies is not possible. However, gravitational lensing by clusters of galaxies allows detection of sources which would otherwise be too dim to study. We have used the largest catalog of sub-mm-selected sources along the line of sight to galaxy clusters to estimate the faint end of the 850 micron number counts; the equivalent flux density at 850 microns is v I_v = 3.9 +/- 0.7 x 10^-10 W/m^2/sr. This provides a lower limit to the extragalactic far infrared background and is consistent with direct estimates of the full intensity from the FIRAS. The results presented here can help to guide strategies for upcoming surveys carried out with single dish sub-mm instruments.

  20. Star formation in isolated AMIGA galaxies: dynamical influence of bars

    CERN Document Server

    Verley, S; Verdes-Montenegro, L; Bergond, G; Leon, S

    2007-01-01

    Star formation depends strongly both on the local environment of galaxies, and on the internal dynamics of the interstellar medium. To disentangle the two effects, we obtained, in the framework of the AMIGA project, Ha and Gunn r photometric data for more than 200 spiral galaxies lying in very low-density regions of the local Universe. We characterise the Ha emission, tracing current star formation, of the 45 largest and less inclined galaxies observed for which we estimate the torques between the gas and the bulk of the optical matter. We could subsequently study the Ha morphological aspect of these isolated spiral galaxies. Using Fourier analysis, we focus on the modes of the spiral arms and also on the strength of the bars, computing the torques between the gas and newly formed stars (Ha) and the bulk of the optical matter (Gunn r). We interpret the various bar/spiral morphologies observed in terms of the secular evolution experienced by galaxies in isolation. We also classify the different spatial distrib...

  1. Supermassive Black Hole Binaries: Environment and Galaxy Host Properties of PTA and eLISA sources

    CERN Document Server

    Palafox, Eva Martínez; Colín, Pedro; Gottlöber, Stefan

    2014-01-01

    Supermassive black hole (BH) binaries would comprise the strongest sources of gravitational waves (GW) once they reach <<1 pc separations, for both pulsar timing arrays (PTAs) and space based (SB) detectors. While BH binaries coalescences constitute a natural outcome of the cosmological standard model and galaxy mergers, their dynamical evolution is still poorly understood and therefore their abundances at different stages. We use a dynamical model for the decay of BH binaries coupled with a cosmological simulation and semi-empirical approaches to the occupation of haloes by galaxies and BHs, in order to follow the evolution of the properties distribution of galaxies hosting BH binaries candidates to decay due to GWs emission. Our models allow us to relax simplifying hypothesis about the binaries occupation in galaxies and their mass, as well as redshift evolution. Following previously proposed electromagnetic (EM) signatures of binaries in the subpc regime, that include spectral features and variabilit...

  2. SUPERMASSIVE BLACK HOLES AND THEIR HOST SPHEROIDS. I. DISASSEMBLING GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Savorgnan, G. A. D.; Graham, A. W., E-mail: gsavorgn@astro.swin.edu.au [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia)

    2016-01-15

    Several recent studies have performed galaxy decompositions to investigate correlations between the black hole mass and various properties of the host spheroid, but they have not converged on the same conclusions. This is because their models for the same galaxy were often significantly different and not consistent with each other in terms of fitted components. Using 3.6 μm Spitzer imagery, which is a superb tracer of the stellar mass (superior to the K band), we have performed state-of-the-art multicomponent decompositions for 66 galaxies with directly measured black hole masses. Our sample is the largest to date and, unlike previous studies, contains a large number (17) of spiral galaxies with low black hole masses. We paid careful attention to the image mosaicking, sky subtraction, and masking of contaminating sources. After a scrupulous inspection of the galaxy photometry (through isophotal analysis and unsharp masking) and—for the first time—2D kinematics, we were able to account for spheroids; large-scale, intermediate-scale, and nuclear disks; bars; rings; spiral arms; halos; extended or unresolved nuclear sources; and partially depleted cores. For each individual galaxy, we compared our best-fit model with previous studies, explained the discrepancies, and identified the optimal decomposition. Moreover, we have independently performed one-dimensional (1D) and two-dimensional (2D) decompositions and concluded that, at least when modeling large, nearby galaxies, 1D techniques have more advantages than 2D techniques. Finally, we developed a prescription to estimate the uncertainties on the 1D best-fit parameters for the 66 spheroids that takes into account systematic errors, unlike popular 2D codes that only consider statistical errors.

  3. The EAGLE simulations: atomic hydrogen associated with galaxies

    Science.gov (United States)

    Crain, Robert A.; Bahé, Yannick M.; Lagos, Claudia del P.; Rahmati, Alireza; Schaye, Joop; McCarthy, Ian G.; Marasco, Antonino; Bower, Richard G.; Schaller, Matthieu; Theuns, Tom; van der Hulst, Thijs

    2017-02-01

    We examine the properties of atomic hydrogen (H I) associated with galaxies in the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations of galaxy formation. EAGLE's feedback parameters were calibrated to reproduce the stellar mass function and galaxy sizes at z = 0.1, and we assess whether this calibration also yields realistic H I properties. We estimate the self-shielding density with a fitting function calibrated using radiation transport simulations, and correct for molecular hydrogen with empirical or theoretical relations. The `standard-resolution' simulations systematically underestimate H I column densities, leading to an H I deficiency in low-mass (M⋆ standard-resolution simulations. The largest volume simulation reproduces the observed clustering of H I systems, and its dependence on H I richness. At fixed M⋆, galaxies acquire more H I in simulations with stronger feedback, as they become associated with more massive haloes and higher infall rates. They acquire less H I in simulations with a greater star formation efficiency, since the star formation and feedback necessary to balance the infall rate is produced by smaller gas reservoirs. The simulations indicate that the H I of present-day galaxies was acquired primarily by the smooth accretion of ionized, intergalactic gas at z ≃ 1, which later self-shields, and that only a small fraction is contributed by the reincorporation of gas previously heated strongly by feedback. H I reservoirs are highly dynamic: over 40 per cent of H I associated with z = 0.1 galaxies is converted to stars or ejected by z = 0.

  4. Globular Cluster Systems in Brightest Cluster Galaxies. III: Beyond Bimodality

    Science.gov (United States)

    Harris, William E.; Ciccone, Stephanie M.; Eadie, Gwendolyn M.; Gnedin, Oleg Y.; Geisler, Douglas; Rothberg, Barry; Bailin, Jeremy

    2017-01-01

    We present new deep photometry of the rich globular cluster (GC) systems around the Brightest Cluster Galaxies UGC 9799 (Abell 2052) and UGC 10143 (Abell 2147), obtained with the Hubble Space Telescope (HST) ACS and WFC3 cameras. For comparison, we also present new reductions of similar HST/ACS data for the Coma supergiants NGC 4874 and 4889. All four of these galaxies have huge cluster populations (to the radial limits of our data, comprising from 12,000 to 23,000 clusters per galaxy). The metallicity distribution functions (MDFs) of the GCs can still be matched by a bimodal-Gaussian form where the metal-rich and metal-poor modes are separated by ≃ 0.8 dex, but the internal dispersions of each mode are so large that the total MDF becomes very broad and nearly continuous from [Fe/H] ≃ ‑2.4 to solar. There are, however, significant differences between galaxies in the relative numbers of metal-rich clusters, suggesting that they underwent significantly different histories of mergers with massive gas-rich halos. Last, the proportion of metal-poor GCs rises especially rapidly outside projected radii R≳ 4 {R}{eff}, suggesting the importance of accreted dwarf satellites in the outer halo. Comprehensive models for the formation of GCs as part of the hierarchical formation of their parent galaxies will be needed to trace the systematic change in structure of the MDF with galaxy mass, from the distinctly bimodal form in smaller galaxies up to the broad continuum that we see in the very largest systems.

  5. Galaxy Zoo Supernovae

    CERN Document Server

    Smith, A M; Sullivan, M; Lintott, C J; Nugent, P E; Botyanszki, J; Kasliwal, M; Quimby, R; Bamford, S P; Fortson, L F; Schawinski, K; Hook, I; Blake, S; Podsiadlowski, P; Joensson, J; Gal-Yam, A; Arcavi, I; Howell, D A; Bloom, J S; Jacobsen, J; Kulkarni, S R; Law, N M; Ofek, E O; Walters, R

    2010-01-01

    This paper presents the first results from a new citizen science project: Galaxy Zoo Supernovae. This proof of concept project uses members of the public to identify supernova candidates from the latest generation of wide-field imaging transient surveys. We describe the Galaxy Zoo Supernovae operations and scoring model, and demonstrate the effectiveness of this novel method using imaging data and transients from the Palomar Transient Factory (PTF). We examine the results collected over the period April-July 2010, during which nearly 14,000 supernova candidates from PTF were classified by more than 2,500 individuals within a few hours of data collection. We compare the transients selected by the citizen scientists to those identified by experienced PTF scanners, and find the agreement to be remarkable - Galaxy Zoo Supernovae performs comparably to the PTF scanners, and identified as transients 93% of the ~130 spectroscopically confirmed SNe that PTF located during the trial period (with no false positive iden...

  6. PEARS Emission Line Galaxies

    Science.gov (United States)

    Pirzkal, Nor; Rothberg, Barry; Ly, Chun; Rhoads, James E.; Malhotra, Sangeeta; Grogin, Norman A.; Dahlen, Tomas; Meurer, Gerhardt R.; Walsh, Jeremy; Hathi, Nimish P.; Cohen, Seth; Belini, Andrea; Holwerda, Benne W.; Straughn, Amber; Mechtley, Matthew

    2012-01-01

    We present a full analysis of the Probing Evolution And Reionization Spectroscopically (PEARS) slitless grism spectroscopic data obtained vl'ith the Advanced Camera for Surveys on HST. PEARS covers fields within both the Great Observatories Origins Deep Survey (GOODS) North and South fields, making it ideal as a random surveY of galaxies, as well as the availability of a wide variety of ancillary observations to support the spectroscopic results. Using the PEARS data we are able to identify star forming galaxies within the redshift volume 0 = 10(exp 9) Solar M decreases by an order of magnitude at z<=0.5 relative to the number at 0.5 < z < 0.9 in support of the argument for galaxy downsizing.

  7. Magnetic fields in galaxies

    CERN Document Server

    Beck, Rainer

    2013-01-01

    Most of the visible matter in the Universe is ionized, so that cosmic magnetic fields are quite easy to generate and due to the lack of magnetic monopoles hard to destroy. Magnetic fields have been measured in or around practically all celestial objects, either by in-situ measurements of spacecrafts or by the electromagnetic radiation of embedded cosmic rays, gas or dust. The Earth, the Sun, solar planets, stars, pulsars, the Milky Way, nearby galaxies, more distant (radio) galaxies, quasars and even intergalactic space in clusters of galaxies have significant magnetic fields, and even larger volumes of the Universe may be permeated by "dark" magnetic fields. Information on cosmic magnetic fields has increased enormously as the result of the rapid development of observational methods, especially in radio astronomy. In the Milky Way, a wealth of magnetic phenomena was discovered, which are only partly related to objects visible in other spectral ranges. The large-scale structure of the Milky Way's magnetic fie...

  8. Slowly cooking galaxies

    CERN Document Server

    Legrand, F

    1999-01-01

    Recent spectroscopic observations of IZw~18 have revealed homogeneous abundance throughout the galaxy and several observations of other starburst galaxies have shown no significant gradient or discontinuity in the abundance distributions within the HII regions. I thus concur with Tenorio-Tagle (1996) and Devost et al. (1997) that these observed abundance homogeneities cannot be produced by the material ejected from the stars formed in the current burst and result from a previous star formation episode. Metals ejected in the current burst of star formation remain most probably hidden in a hot phase and are undetectable using optical spectroscopy. Combining various observational facts, for instance the faint star formation rate observed in low surface brightness galaxies (van Zee et al., 1997), I propose that a low and continuous star formation rate occurring during quiescent phases between bursts is a non negligible source of new elements in the interstellar medium. Using a spectrophotometric and chemical evol...

  9. Enhancing the view of a million galaxies

    Science.gov (United States)

    2004-06-01

    Composite image hi-res Size hi-res: 851 KB Credits: ESA/Univ. of Leicester/I. Stewart and M. Watson XMM-Newton X-ray spectral colour composite image XMM-Newton X-ray spectral colour composite image of the Subaru/XMM-Newton Deep Field. The view gives an X-ray pseudo-colour representation of all the sources, coded according to their X-ray energy. More energetic sources are shown in blue and less energetic ones in red. This mosaic image, composed of 7 partially overlapping pointings, maps the full extent of the SXDF and corresponds to an exposure time exceeding one hundred hours. These data form the largest contiguous area over which deep X-ray observations have been performed. Composite image hi-res Size hi-res: 6215 KB Credits: NAOJ/Subaru Telescope XMM-Newton/Subaru colour composite image A colour composite image obtained by combining data taken with the Subaru Telescope in blue, red and near-infrared light. The image, worth over two hundred hours of exposure time, covers an area of sky seven times larger than the full moon. The images in blue light show details several hundred million times fainter than what can be seen with the naked eye. SXDS field hi-res Size hi-res: 448 KB Credits: NAOJ/Subaru Telescope SXDS field A particular of the SXDS field. The teardrop-shaped galaxy in the upper right portion of the frame is likely to have suffered from a collision with another galaxy. SXDS field hi-res Size hi-res: 358 KB Credits: NAOJ/Subaru Telescope SXDS field A particular of the SXDS field. The prominent spiral galaxy near the centre may be ineracting with a less-conspicuous dwarf galaxy to its lower right. One of the fundamental goals of modern astronomy is understanding the history of the Universe, and in particular learning about the processes that shape the formation and evolution of galaxies. To observe these processes as they unfold, astronomers must survey galaxies near and far, spanning a large enough volume of the Universe, so that local variations in the

  10. Radio Galaxy Zoo: discovery of a poor cluster through a giant wide-angle tail radio galaxy

    CERN Document Server

    Banfield, J K; Kapinska, A D; Rudnick, L; Hardcastle, M J; Cotter, G; Vaughan, S; Jones, T W; Heywood, I; Wing, J D; Wong, O I; Matorny, T; Terentev, I A; Lopez-Sanchez, A R; Norris, R P; Seymour, N; Shabala, S S; Willett, K W

    2016-01-01

    We have discovered a previously unreported poor cluster of galaxies (RGZ-CL J0823.2+0333) through an unusual giant wide-angle tail radio galaxy found in the Radio Galaxy Zoo project. We obtained a spectroscopic redshift of $z=0.0897$ for the E0-type host galaxy, 2MASX J08231289+0333016, leading to M$_r = -22.6$ and a $1.4\\,$GHz radio luminosity density of $L_{\\rm 1.4} = 5.5\\times10^{24}$ W Hz$^{-1}$. These radio and optical luminosities are typical for wide-angle tailed radio galaxies near the borderline between Fanaroff-Riley (FR) classes I and II. The projected largest angular size of $\\approx8\\,$arcmin corresponds to $800\\,$kpc and the full length of the source along the curved jets/trails is $1.1\\,$Mpc in projection. X-ray data from the XMM-Newton archive yield an upper limit on the X-ray luminosity of the thermal emission surrounding RGZ J082312.9+033301,at $1.2-2.6\\times10^{43}$ erg s$^{-1}$ for assumed intra-cluster medium temperatures of $1.0-5.0\\,$keV. Our analysis of the environment surrounding RGZ ...

  11. Galaxy Zoo Supernovae

    Science.gov (United States)

    Smith, A. M.; Lynn, S.; Sullivan, M.; Lintott, C. J.; Nugent, P. E.; Botyanszki, J.; Kasliwal, M.; Quimby, R.; Bamford, S. P.; Fortson, L. F.; Schawinski, K.; Hook, I.; Blake, S.; Podsiadlowski, P.; Jönsson, J.; Gal-Yam, A.; Arcavi, I.; Howell, D. A.; Bloom, J. S.; Jacobsen, J.; Kulkarni, S. R.; Law, N. M.; Ofek, E. O.; Walters, R.

    2011-04-01

    This paper presents the first results from a new citizen science project: Galaxy Zoo Supernovae. This proof-of-concept project uses members of the public to identify supernova candidates from the latest generation of wide-field imaging transient surveys. We describe the Galaxy Zoo Supernovae operations and scoring model, and demonstrate the effectiveness of this novel method using imaging data and transients from the Palomar Transient Factory (PTF). We examine the results collected over the period 2010 April-July, during which nearly 14 000 supernova candidates from the PTF were classified by more than 2500 individuals within a few hours of data collection. We compare the transients selected by the citizen scientists to those identified by experienced PTF scanners and find the agreement to be remarkable - Galaxy Zoo Supernovae performs comparably to the PTF scanners and identified as transients 93 per cent of the ˜130 spectroscopically confirmed supernovae (SNe) that the PTF located during the trial period (with no false positive identifications). Further analysis shows that only a small fraction of the lowest signal-to-noise ratio detections (r > 19.5) are given low scores: Galaxy Zoo Supernovae correctly identifies all SNe with ≥8σ detections in the PTF imaging data. The Galaxy Zoo Supernovae project has direct applicability to future transient searches, such as the Large Synoptic Survey Telescope, by both rapidly identifying candidate transient events and via the training and improvement of existing machine classifier algorithms. This publication has been made possible by the participation of more than 10 000 volunteers in the Galaxy Zoo Supernovae project ().

  12. Ring Around a Galaxy

    Science.gov (United States)

    1999-01-01

    Space Telescope Science Institute astronomers are giving the public chances to decide where to aim NASA's Hubble Space Telescope. Guided by 8,000 Internet voters, Hubble has already been used to take a close-up, multi-color picture of the most popular object from a list of candidates, the extraordinary 'polar-ring' galaxy NGC 4650A. Located about 130 million light-years away, NGC 4650A is one of only 100 known polar-ring galaxies. Their unusual disk-ring structure is not yet understood fully. One possibility is that polar rings are the remnants of colossal collisions between two galaxies sometime in the distant past, probably at least 1 billion years ago. What is left of one galaxy has become the rotating inner disk of old red stars in the center. Meanwhile, another smaller galaxy which ventured too close was probably severely damaged or destroyed. The bright bluish clumps, which are especially prominent in the outer parts of the ring, are regions containing luminous young stars, examples of stellar rebirth from the remnants of an ancient galactic disaster. The polar ring appears to be highly distorted. No regular spiral pattern stands out in the main part of the ring, and the presence of young stars below the main ring on one side and above on the other shows that the ring is warped and does not lie in one plane. Determining the typical ages of the stars in the polar ring is an initial goal of our Polar Ring Science Team that can provide a clue to the evolution of this unusual galaxy. The HST exposures were acquired by the Hubble Heritage Team, consisting of Keith Noll, Howard Bond, Carol Christian, Jayanne English, Lisa Frattare, Forrest Hamilton, Anne Kinney and Zolt Levay, and guest collaborators Jay Gallagher (University of Wisconsin-Madison), Lynn Matthews (National Radio Astronomy Observatory-Charlottesville), and Linda Sparke (University of Wisconsin-Madison).

  13. Relaxation of liquid bridge after droplets coalescence

    Directory of Open Access Journals (Sweden)

    Jiangen Zheng

    2016-11-01

    Full Text Available We investigate the relaxation of liquid bridge after the coalescence of two sessile droplets resting on an organic glass substrate both experimentally and theoretically. The liquid bridge is found to relax to its equilibrium shape via two distinct approaches: damped oscillation relaxation and underdamped relaxation. When the viscosity is low, damped oscillation shows up, in this approach, the liquid bridge undergoes a damped oscillation process until it reaches its stable shape. However, if the viscous effects become significant, underdamped relaxation occurs. In this case, the liquid bridge relaxes to its equilibrium state in a non-periodic decay mode. In depth analysis indicates that the damping rate and oscillation period of damped oscillation are related to an inertial-capillary time scale τc. These experimental results are also testified by our numerical simulations with COMSOL Multiphysics.

  14. Cross relaxation in nitroxide spin labels

    Science.gov (United States)

    Marsh, Derek

    2016-11-01

    Cross relaxation, and mI -dependence of the intrinsic electron spin-lattice relaxation rate We , are incorporated explicitly into the rate equations for the electron-spin population differences that govern the saturation behaviour of 14N- and 15N-nitroxide spin labels. Both prove important in spin-label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We , the intrinsic spin-lattice relaxation rate. Independence of the saturation recovery rates from the hyperfine line pumped or observed follows directly from solution of the rate equations including cross relaxation, even when the intrinsic spin-lattice relaxation rate We is mI -dependent.

  15. Chandra Finds Surprising Black Hole Activity In Galaxy Cluster

    Science.gov (United States)

    2002-09-01

    bright active galaxies, often referred to as Active Galactic Nuclei, or AGN. Many astronomers think that all galaxies have central, supermassive black holes, yet only a small percent show activity. What is needed to power the AGN is fuel in the form of a nearby reservoir of gas and dust. Galaxy clusters contain hundreds to thousands of galaxies. They are the largest known structures in the universe and serve as a microcosm for the mechanics of the Universe at large. The galaxies in clusters are often old, reddish elliptically shaped galaxies, distinct from blue, spiral galaxies like our own. These old galaxies also do not have many young stars. The theory now in question is that as galaxies enter into clusters at high speeds, they are stripped of their interstellar gas, much as a strong wind strips leaves from a tree. Galaxies may also collide with one another and use up all of their gas in one huge burst of star formation triggered by this interaction. These processes remove most, if not all, of the gas that isn't locked up in stars. As they no longer have the raw material to form new stars, the stellar population slowly gets old and the Galaxy appears red. No gas is left to fuel an AGN. Previous surveys of galaxy clusters with optical telescopes have found that about only one percent of the galaxies in a cluster have AGN. This latest Chandra observation if typical, however, bumps the count up to about 5 percent. The team found six red galaxies with high X-ray activity during a nearly 14-hour Chandra observation of a galaxy cluster named Abell 2104, over 700 million light years from Earth. Based on previous optical surveys, only one was expected. "If we relied on optical data alone, we would have missed these hidden monsters," said co-author Dr. John Mulchaey. Only one of the six AGN, in fact, had the optical spectral properties typical of AGN activity. "The presence of these AGN indicate that supermassive black holes have somehow retained a fuel source, despite the

  16. Galaxies & the universe

    CERN Document Server

    Homer, Charlene

    2007-01-01

    Get the big picture about Galaxies and our Universe. From the smallest particles of matter to the biggest star system, our universe is made up of all things that exist in space. Our resource takes you through the Milky Way Galaxy, Black Holes and Gravity, then on to Nebulae, Sources of Light and the Speed of Light, and finally to Quasars, the most distant objects in the universe. Written using simplified language and vocabulary, our resource presents science concepts in a way that makes them accessible to students and easier to understand. Comprised of reading passages, student activities for

  17. Galaxy alignments: An overview

    CERN Document Server

    Joachimi, Benjamin; Kitching, Thomas D; Leonard, Adrienne; Mandelbaum, Rachel; Schäfer, Björn Malte; Sifón, Cristóbal; Hoekstra, Henk; Kiessling, Alina; Kirk, Donnacha; Rassat, Anais

    2015-01-01

    The alignments between galaxies, their underlying matter structures, and the cosmic web constitute vital ingredients for a comprehensive understanding of gravity, the nature of matter, and structure formation in the Universe. We provide an overview on the state of the art in the study of these alignment processes and their observational signatures, aimed at a non-specialist audience. The development of the field over the past one hundred years is briefly reviewed. We also discuss the impact of galaxy alignments on measurements of weak gravitational lensing, and discuss avenues for making theoretical and observational progress over the coming decade.

  18. Galaxy S II

    CERN Document Server

    Gralla, Preston

    2011-01-01

    Unlock the potential of Samsung's outstanding smartphone with this jargon-free guide from technology guru Preston Gralla. You'll quickly learn how to shoot high-res photos and HD video, keep your schedule, stay in touch, and enjoy your favorite media. Every page is packed with illustrations and valuable advice to help you get the most from the smartest phone in town. The important stuff you need to know: Get dialed in. Learn your way around the Galaxy S II's calling and texting features.Go online. Browse the Web, manage email, and download apps with Galaxy S II's 3G/4G network (or create you

  19. Watching the Creation of Southern California's Largest Reservoir

    Science.gov (United States)

    2001-01-01

    The new Diamond Valley Lake Reservoir near the city of Hemet in Riverside County is billed as the largest earthworks construction project in U.S.history. Construction began in 1995 and involved 31 million cubic meters of foundation excavation and 84 million cubic meters of embankment construction. This set of MISR images captures the most recent phase in the reservoir's activation. At the upper left is a natural-color view acquired by the instrument's vertical-viewing (nadir) camera on March 14, 2000 (Terra orbit 1273), shortly after the Metropolitan Water District began filling the reservoir with water from the Colorado River and Northern California. Water appears darker than the surrounding land. The image at the upper right was acquired nearly one year later on March 1, 2001 (Terra orbit 6399), and shows a clear increase in the reservoir's water content. When full, the lake will hold nearly a trillion liters of water.According to the Metropolitan Water District, the 7 kilometer x 3 kilometer reservoir nearly doubles Southern California's above-groundwater storage capacity. In addition to routine water management, Diamond Valley Lake is designed to provide protection against drought and a six-month emergency supply in the event of earthquake damage to a major aqueduct. In the face of electrical power shortages, it is also expected to reduce dependence on the pumping of water from northern mountains during the high-demand summer months. An unexpected result of site excavation was the uncovering of mastodon and mammoth skeletons along with bones from extinct species not previously thought to have been indigenous to the area, such as the giant long-horned bison and North American lion. A museum and interpretive center is being built to protect these finds.The lower MISR image, from May 20, 2001 (Terra orbit 7564), is a false-color view combining data from the instrument's 26-degree forward view (displayed as blue) with data from the 26-degree backward view

  20. Smart-Geology for the World's largest fossil oyster reef

    Science.gov (United States)

    Dorninger, Peter; Nothegger, Clemens; Djuricic, Ana; Rasztovits, Sascha; Harzhauser, Mathias

    2014-05-01

    The geo-edutainment park "Fossilienwelt Weinviertel" at Stetten in Lower Austria exposes the world's largest fossil oyster biostrome. In the past decade, significant progress has been made in 3D digitizing sensor technology. To cope with the high amount of data, processing methods have been automated to a high degree. Consequently, we formulated the hypothesis that appropriate application of state-of-the-art 3D digitizing, data processing, and visualization technologies allows for a significant automation in paleontological prospection, making an evaluation of huge areas commercially feasible in both time and costs. We call the necessary processing steps "Smart Geology", being characterized by automation and large volumes of data. The Smart Geology project (FWF P 25883-N29) investigates three topics, 3D digitizing, automated geological and paleontological analysis and interpretation and finally investigating the applicability of smart devices for on-site accessibility of project data in order to support the two scientific hypotheses concerning the emerging process of the shell bed, i.e. was it formed by a tsunami or a major storm, and does it preserve pre- and post-event features. This contribution concentrates on the innovative and sophisticated 3D documentation and visualization processes being applied to virtualise approximately 15.000 fossil oysters at the approximately 25 by 17 m accessible shell bad. We decided to use a Terrestrial Laserscanner (TLS) for the determination of the geometrical 3D structures. The TLS achieves about 2 mm single point measurement accuracy. The scanning campaign provides a "raw" point cloud of approximately 1 bio. points at the respective area. Due to the scanning configuration used, the occurrence of occluded ares is minimized hence the full 3D structure of this unique site can be modelled. In addition, approximately 300 photos were taken with a nominal resolution of 0.6 mm per pixel. Sophisticated artificial lightning (close to

  1. Watching the Creation of Southern California's Largest Reservoir

    Science.gov (United States)

    2001-01-01

    The new Diamond Valley Lake Reservoir near the city of Hemet in Riverside County is billed as the largest earthworks construction project in U.S.history. Construction began in 1995 and involved 31 million cubic meters of foundation excavation and 84 million cubic meters of embankment construction. This set of MISR images captures the most recent phase in the reservoir's activation. At the upper left is a natural-color view acquired by the instrument's vertical-viewing (nadir) camera on March 14, 2000 (Terra orbit 1273), shortly after the Metropolitan Water District began filling the reservoir with water from the Colorado River and Northern California. Water appears darker than the surrounding land. The image at the upper right was acquired nearly one year later on March 1, 2001 (Terra orbit 6399), and shows a clear increase in the reservoir's water content. When full, the lake will hold nearly a trillion liters of water.According to the Metropolitan Water District, the 7 kilometer x 3 kilometer reservoir nearly doubles Southern California's above-groundwater storage capacity. In addition to routine water management, Diamond Valley Lake is designed to provide protection against drought and a six-month emergency supply in the event of earthquake damage to a major aqueduct. In the face of electrical power shortages, it is also expected to reduce dependence on the pumping of water from northern mountains during the high-demand summer months. An unexpected result of site excavation was the uncovering of mastodon and mammoth skeletons along with bones from extinct species not previously thought to have been indigenous to the area, such as the giant long-horned bison and North American lion. A museum and interpretive center is being built to protect these finds.The lower MISR image, from May 20, 2001 (Terra orbit 7564), is a false-color view combining data from the instrument's 26-degree forward view (displayed as blue) with data from the 26-degree backward view

  2. The Largest Holocene Eruption of the Central Andes Found

    Science.gov (United States)

    Fernandez-Turiel, J.; Rodriguez-Gonzalez, A.; Saavedra, J.; Perez-Torrado, F.; Carracedo, J.; Osterrieth, M.; Carrizo, J.; Esteban, G.

    2013-12-01

    We present new data and interpretation about a major eruption -spreading ˜110 km3 ashes over 440.000 km2- long thought to have occurred around 4200 years ago in the Cerro Blanco Volcanic Complex (CBVC) in NW Argentina. This eruption may be the biggest during the past five millennia in the Central Volcanic Zone of the Andes, and possibly one of the largest Holocene eruptions in the world. The environmental effects of this voluminous eruption are still noticeable, as evidenced by the high content of arsenic and other trace elements in the groundwaters of the Chacopampean Plain. The recognition of this significant volcanic event may shed new light on interpretations of critical changes observed in the mid-Holocene paleontological and archaeological records, and offers researchers an excellent, extensive regional chronostratigraphic marker for reconstructing mid-Holocene geological history over a wide geographical area of South America. More than 100 ashes were sampled in Argentina, Chile and Uruguay during different field campaigns. Ash samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), grain size distributions laser diffraction, and geochemically by electron microprobe (EMPA) and laser ablation-HR-ICP-MS. New and published 14C ages were calibrated to calendar years BP. The age of the most recent CBVC eruption is 4407-4093 cal y BP, indirectly dated by 14C of associated organic sediment within the lower part of a proximal fall deposit of this event (26°53'16.05"S-67°44'48.68"W). This is the youngest record of a major volcanic event in the Southern Puna. This age is consistent with other radiocarbon dates of organic matter in palaeosols underlying or overlying distal ash fall deposits. Based on their products, all of rhyolitic composition, we have distinguished 8 main episodes during the evolution of the most recent CBVC eruption: 1) the eruption began with a white rhyolite lava dome extrusion; 2) followed by a Plinian

  3. Physical Coupling of Kazarian Galaxies with Surrounding Galaxies

    Science.gov (United States)

    Kazarian, M. A.; Martirosian, J. R.

    2003-04-01

    Results from a statistical study of Kazarian galaxies and the objects surrounding them are presented. It is shown that: (1) the sample of Kazarian galaxies up to 16m.0 is complete. (2) Roughly 35.7% of the Kazarian galaxies are members of clusters, 14.0% of groups, and 13.6% of binary systems, while 36.7% are single galaxies. (3) Of the 580 Kazarian galaxies, roughly 61.2% are infrared, 8.8% radio, and 2.8% x-ray sources. (4) The relative numbers of Kazarian galaxies for complete samples of I, R, and X in the different groups are systematically higher than the corresponding numbers for samples of all Kazarian galaxies.

  4. The high redshift galaxy population in hierarchical galaxy formation models

    CERN Document Server

    Kitzbichler, M G; Kitzbichler, Manfred G.; White, Simon D. M.

    2006-01-01

    We compare observations of the high redshift galaxy population to the predictions of the galaxy formation model of Croton et al. (2006). This model, implemented on the Millennium Simulation of the concordance LCDM cosmogony, introduces "radio mode" feedback from the central galaxies of groups and clusters in order to obtain quantitative agreement with the luminosity, colour, morphology and clustering properties of the low redshift galaxy population. Here we compare the predictions of this same model to the observed counts and redshift distributions of faint galaxies, as well as to their inferred luminosity and mass functions out to redshift 5. With the exception of the mass functions, all these properties are sensitive to modelling of dust obscuration. A simple but plausible treatment gives moderately good agreement with most of the data, although the predicted abundance of relatively massive (~M*) galaxies appears systematically high at high redshift, suggesting that such galaxies assemble earlier in this mo...

  5. Galaxy-galaxy Lensing: Dissipationless Simulations Versus the Halo Model

    CERN Document Server

    Mandelbaum, R; Seljak, U; Kravtsov, A V; Wechsler, R H; Mandelbaum, Rachel; Tasitsiomi, Argyro; Seljak, Uros; Kravtsov, Andrey V.; Wechsler, Risa H.

    2004-01-01

    Galaxy-galaxy lensing is a powerful probe of the relation between galaxies and dark matter halos, but its theoretical interpretation requires a careful modeling of various contributions, such as the contribution from central and satellite galaxies. For this purpose, a phenomenological approach based on the halo model has been developed, allowing for fast exploration of the parameter space of models. In this paper, we investigate the ability of the halo model to extract information from the g-g weak lensing signal by comparing it to high-resolution dissipationless simulations that resolve subhalos. We find that the halo model reliably determines parameters such as the host halo mass of central galaxies, the fraction of galaxies that are satellites, and their radial distribution inside larger halos. If there is a significant scatter present in the central galaxy host halo mass distribution, then the mean and median mass of that distribution can differ significantly from one another, and the halo model mass dete...

  6. Galaxy bachelors, couples, spouses: Star formation in interacting galaxies

    Science.gov (United States)

    Sun, Jing; Barger, Kathleen; Richstein, Hannah; SDSS-IV/MaNGA

    2017-01-01

    We investigate the star formation activity in three galaxy systems in different stages of interaction to determine how the environment of galaxies affects their star forming ability and potential. These systems include an isolated galaxy, a pair of interacting galaxies, and a pair of merging galaxies. All of the target galaxies in these systems have similar stellar masses and similar radii and are at similar redshifts. We trace the star formation activity over the past 1-2 Gyr using spatially and kinematically resolved H-alpha emission, H-alpha equivalent width, and 4000-Angstrom break maps. This work is based on data from the fourth-generation Sloan Digital Sky Survey (SDSS-IV)/Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), and is part of the Project No.0285 in SDSS-IV.

  7. Utilizing RELAX NG Schemas in XML Editors

    OpenAIRE

    Schmied, Martin

    2008-01-01

    This thesis explores the possibilities of utilizing RELAX NG schemata in the process of editing XML documents. The ultimate goal of this thesis is to prototype a system supporting user while editing XML document with bound RELAX NG schema inside the Eclipse IDE. Such a system comprises two major components -- an integration of RELAX NG validator and an autocompletion engine. Design of the autocompletion engine represents the main contribution of this thesis, because similar systems are almost...

  8. LoCuSS: Weak-lensing mass calibration of galaxy clusters

    CERN Document Server

    Okabe, Nobuhiro

    2015-01-01

    We present weak-lensing mass measurements of 50 X-ray luminous galaxy clusters at $0.15\\le z\\le0.3$, based on high quality observations with Suprime-Cam mounted on the 8.2-m Subaru telescope. We pay close attention to possible systematic biases, aiming to control them at the $\\lt4$ per cent level. The dominant source of systematic bias in weak-lensing measurements of the mass of individual galaxy clusters is contamination of background galaxy catalogues by faint cluster and foreground galaxies. We extend our conservative method for selecting background galaxies with $(V-i')$ colours redder than the red sequence of cluster members to use a colour-cut that depends on cluster-centric radius. This allows us to define background galaxy samples that suffer $\\le1$ per cent contamination, and comprise $13$ galaxies per square arcminute. Thanks to the purity of our background galaxy catalogue, the largest systematic in our measurement is a shape measurement bias of $3$ per cent, that we measure using custom-made simul...

  9. How tidal erosion has shaped the relation between globular cluster specific frequency and galaxy luminosity

    CERN Document Server

    Mieske, Steffen; Brockamp, Michael

    2014-01-01

    We quantify to what extent tidal erosion of globular clusters (GCs) has contributed to the observed u-shaped relation between GC specific frequencies S_N and host galaxy luminosity M_V. We used our MUESLI code to calculate GC survival rates for typical early-type galaxy potentials covering a wide range of observed galaxy properties. We do this for isotropic and radially anisotropic GC velocity distributions. We find that the calculated GC survival fraction, f_s, depends linearly on the logarithm of the 3D mass density, rho_3D, within the galaxy's half light radius, with f_s proportional to (rho_3D)^(-0.17). For a given galaxy, survival rates are lower for radially anisotropic configurations than for the isotropic GC cases. We apply these relations to a literature sample of 219 early-type galaxies from Harris et al. (2013) in the range M_V=[-24.5:-15.5] mag. The expected GC survival fraction ranges from ~50% for the most massive galaxies with the largest radii to ~10% for the most compact galaxies. We find tha...

  10. LOFAR MSSS: Discovery of a 2.56 Mpc giant radio galaxy associated with a disturbed galaxy group

    Science.gov (United States)

    Clarke, A. O.; Heald, G.; Jarrett, T.; Bray, J. D.; Hardcastle, M. J.; Cantwell, T. M.; Scaife, A. M. M.; Brienza, M.; Bonafede, A.; Breton, R. P.; Broderick, J. W.; Carbone, D.; Croston, J. H.; Farnes, J. S.; Harwood, J. J.; Heesen, V.; Horneffer, A.; van der Horst, A. J.; Iacobelli, M.; Jurusik, W.; Kokotanekov, G.; McKean, J. P.; Morabito, L. K.; Mulcahy, D. D.; Nikiel-Wroczyñski, B. S.; Orrú, E.; Paladino, R.; Pandey-Pommier, M.; Pietka, M.; Pizzo, R.; Pratley, L.; Riseley, C. J.; Rottgering, H. J. A.; Rowlinson, A.; Sabater, J.; Sendlinger, K.; Shulevski, A.; Sridhar, S. S.; Stewart, A. J.; Tasse, C.; van Velzen, S.; van Weeren, R. J.; Wise, M. W.

    2017-05-01

    We report on the discovery in the LOFAR Multifrequency Snapshot Sky Survey (MSSS) of a giant radio galaxy (GRG) with a projected size of 2.56 ± 0.07 Mpc projected on the sky. It is associated with the galaxy triplet UGC 9555, within which one is identified as a broad-line galaxy in the Sloan Digital Sky Survey (SDSS) at a redshift of 0.05453 ± 1 × 10-5, and with a velocity dispersion of 215.86 ± 6.34 km s-1. From archival radio observations we see that this galaxy hosts a compact flat-spectrum radio source, and we conclude that it is the active galactic nucleus (AGN) responsiblefor generating the radio lobes. The radio luminosity distribution of the jets, and the broad-line classification of the host AGN, indicate this GRG is orientated well out of the plane of the sky, making its physical size one of the largest known for any GRG. Analysis of the infrared data suggests that the host is a lenticular type galaxy with a large stellar mass (log M/M⊙ = 11.56 ± 0.12), and a moderate star formation rate (1.2 ± 0.3 M⊙/ year). Spatially smoothing the SDSS images shows the system around UGC 9555 to be significantly disturbed, with a prominent extension to the south-east. Overall, the evidence suggests this host galaxy has undergone one or more recent moderate merger events and is also experiencing tidal interactions with surrounding galaxies, which have caused the star formation and provided the supply of gas to trigger and fuel the Mpc-scale radio lobes.

  11. Temperature relaxation in dense plasma mixtures

    Science.gov (United States)

    Faussurier, Gérald; Blancard, Christophe

    2016-09-01

    We present a model to calculate temperature-relaxation rates in dense plasma mixtures. The electron-ion relaxation rates are calculated using an average-atom model and the ion-ion relaxation rates by the Landau-Spitzer approach. This method allows the study of the temperature relaxation in many-temperature electron-ion and ion-ion systems such as those encountered in inertial confinement fusion simulations. It is of interest for general nonequilibrium thermodynamics dealing with energy flows between various systems and should find broad use in present high energy density experiments.

  12. Baryogenesis via Elementary Goldstone Higgs Relaxation

    CERN Document Server

    Gertov, Helene; Pearce, Lauren; Yang, Louis

    2016-01-01

    We extend the relaxation mechanism to the Elementary Goldstone Higgs frame- work. Besides studying the allowed parameter space of the theory we add the minimal ingredients needed for the framework to be phenomenologically viable. The very nature of the extended Higgs sector allows to consider very flat scalar potential directions along which the relaxation mechanism can be implemented. This fact translates into wider regions of applicability of the relaxation mechanism when compared to the Standard Model Higgs case. Our results show that, if the electroweak scale is not fundamental but radiatively generated, it is possible to generate the observed matter-antimatter asymmetry via the relaxation mechanism.

  13. Dielectric relaxation studies in polyvinyl butyral

    Science.gov (United States)

    Mehendru, P. C.; Kumar, Naresh; Arora, V. P.; Gupta, N. P.

    1982-10-01

    Dielectric measurements have been made in thick films (˜100 μm) of polyvinyl butyral (PVB) having degree of polymerization n=1600, in the frequency range 100 Hz-100 KHz and temperature range 300-373 K. The results indicated that PVB was in the amorphous phase and observed dielectric dispersion has been assigned as the β-relaxation process. The β relaxation is of Debye type with symmetrical distribution of relaxation times. The dielectric relaxation strength Δɛ and the distribution parameters β¯ increase with temperature. The results can be qualitatively explained by assuming the hindered rotation of the side groups involving hydroxyl/acetate groups.

  14. Relaxation and Visualization Strategies for Story Telling

    Institute of Scientific and Technical Information of China (English)

    冯灵林

    2012-01-01

    The importance of training students to tell or retell story is self - evident for mastering English language. The following activity introduces relaxation and visualization strategies for story telling.

  15. Non-bipartite Graphs with Third Largest Laplacian Eigenvalue Less Than Three

    Institute of Scientific and Technical Information of China (English)

    Xiao Dong ZHANG; Rong LUO

    2006-01-01

    All bipartite graphs whose third largest Laplacian eigenvalue is less than 3 have been characterized by Zhang. In this paper, all connected non-bipartite graphs with third largest Laplacian eigenvalue less than three are determined.

  16. West Inner Mongolia Coalfield to be the Largest Bauxite Mine in China

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>With the acceleration of industrialization of extraction of alumina from high aluminum fly ash technology, the West Inner Mongolia coalfield is expected to become the largest bauxite mine with the largest aluminum reserves in China.

  17. Origin of 12 micrometer Emission Across Galaxy Populations from Wise and ADSS Surveys

    Science.gov (United States)

    Donso, E.; Yan, Lin; Tsai, C.; Eisenhardt, P; Stern, D.; Assef, R. J.; Leisawitz, D.; Jarrett, T. H.; Stanford, S. A.

    2012-01-01

    We cross-matched Wide-field Infrared Survey Explorer sources brighter than 1 mJy at 12 micron with the Sloan Digital Sky Survey galaxy spectroscopic catalog to produce a sample of approx. 10(exp 5) galaxies at z = 0.08, the largest of its kind. This sample is dominated (70%) by star-forming (SF) galaxies from the blue sequence, with total IR luminosities in the range approx 10(exp 8)-10(exp 12) Solar L. We identify which stellar populations are responsible for most of the 12 micron emission. We find that most (approx 80%) of the 12 micron emission in SF galaxies is produced by stellar populations younger than 0.6 Gyr. In contrast, the 12 micron emission in weak active galactic nuclei (AGNs; L [O iii] populations. SF galaxies and weak AGNs follow different L(sub 12 micron) - SFR (star formation rate) relations, with weak AGNs showing excess 12 micron emission at low SFR (0.02-1 solar M /yr). This is likely due to dust grains heated by older stars. While the specific star formation rate (SSFR) of SF galaxies is nearly constant, the SSFR of weak AGNs decreases by approx 3 orders of magnitude, reflecting the very different star formation efficiencies between SF galaxies and massive, early-type galaxies. Stronger type II AGNs in our sample (L(sub [O iii]) > 10(exp 7) solar L ), act as an extension of massive SF galaxies, connecting the SF and weak AGN sequences. This suggests a picture where galaxies form stars normally until an AGN (possibly after a starburst episode) starts to gradually quench the SF activity. We also find that 4.6-12 micron color is a useful first-order indicator of SF activity in a galaxy when no other data are available.

  18. Host Galaxy Properties of the Swift BAT Ultra Hard X-Ray Selected AGN

    Science.gov (United States)

    Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa M.; Baumgartner, Wayne; Tueller, Jack; Gehrels, Neil; Valencic, Lynne

    2011-01-01

    We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) AGN with host galaxy optical data to date, with 185 nearby (zAGN from the Swift Burst Alert Telescope (BAT) sample. The BAT AGN host galaxies have intermediate optical colors (u -- r and g -- r) that are bluer than a comparison sample of inactive galaxies and optically selected AGN from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BAT AGN are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGN in massive galaxies (log Stellar Mass >10.5) have a 5 to 10 times higher rate of spiral morphologies than in SDSS AGN or inactive galaxies. We also see enhanced far-IR emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGN are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line (NL) BAT AGN have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [O III] Lambda 5007. There is also a correlation between the stellar mass and X-ray emission. The BAT AGN in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as whole. In agreement with the Unified Model of AGN, and the relatively unbiased nature of the BAT sources, the host galaxy colors and morphologies are independent of measures of obscuration such as X-ray column density or Seyfert type. The high fraction of massive spiral galaxies and galaxy mergers in BAT AGN suggest that host galaxy morphology is related to the activation and fueling of local AGN.

  19. Modeling The GRB Host Galaxy Mass Distribution: Are GRBs Unbiased Tracers of Star Formation?

    Energy Technology Data Exchange (ETDEWEB)

    Kocevski, Daniel; /KIPAC, Menlo Park; West, Andrew A.; /UC, Berkeley, Astron. Dept. /MIT, MKI; Modjaz, Maryam; /UC, Berkeley, Astron. Dept.

    2009-08-03

    We model the mass distribution of long gamma-ray burst (GRB) host galaxies given recent results suggesting that GRBs occur in low metallicity environments. By utilizing measurements of the redshift evolution of the mass-metallicity (M-Z) relationship for galaxies, along with a sharp host metallicity cut-off suggested by Modjaz and collaborators, we estimate an upper limit on the stellar mass of a galaxy that can efficiently produce a GRB as a function of redshift. By employing consistent abundance indicators, we find that sub-solar metallicity cut-offs effectively limit GRBs to low stellar mass spirals and dwarf galaxies at low redshift. At higher redshifts, as the average metallicity of galaxies in the Universe falls, the mass range of galaxies capable of hosting a GRB broadens, with an upper bound approaching the mass of even the largest spiral galaxies. We compare these predicted limits to the growing number of published GRB host masses and find that extremely low metallicity cut-offs of 0.1 to 0.5 Z{sub {circle_dot}} are effectively ruled out by a large number of intermediate mass galaxies at low redshift. A mass function that includes a smooth decrease in the efficiency of producing GRBs in galaxies of metallicity above 12+log(O/H){sub KK04} = 8.7 can, however, accommodate a majority of the measured host galaxy masses. We find that at z {approx} 1, the peak in the observed GRB host mass distribution is inconsistent with the expected peak in the mass of galaxies harboring most of the star formation. This suggests that GRBs are metallicity biased tracers of star formation at low and intermediate redshifts, although our model predicts that this bias should disappear at higher redshifts due to the evolving metallicity content of the universe.

  20. Fundamental properties of Fanaroff-Riley type II radio galaxies investigated via Monte Carlo simulations

    NARCIS (Netherlands)

    Kapińska, A.D.; Uttley, P.; Kaiser, C.

    2012-01-01

    Radio galaxies and quasars are among the largest and most powerful single objects known and are believed to have had a significant impact on the evolving Universe and its large-scale structure. We explore the intrinsic and extrinsic properties of the population of Fanaroff-Riley type II (FR II) obje

  1. Fundamental parameters of FR II radio galaxies and their impact on groups and clusters' environments

    NARCIS (Netherlands)

    Kapińska, A.D.; Uttley, P.

    2013-01-01

    Radio galaxies are among the largest and most powerful single objects known and are found at variety of redshifts, hence they are believed to have had a significant impact on the evolving Universe. Their relativistic jets inject considerable amounts of energy into the environments in which the sourc

  2. Hubble Space Telescope NICMOS observations of the host galaxies of powerful radio sources : Does size matter?

    NARCIS (Netherlands)

    de Vries, WH; O'Dea, CP; Barthel, PD; Fanti, C; Fanti, R; Lehnert, MD

    2000-01-01

    We present near-infrared J- and K-band imaging of a sample of powerful radio source host galaxies with the Hubble Space Telescope NICMOS2 camera. These sources have been selected on their double-lobed radio structure and include a wide range of projected radio source sizes. The largest projected

  3. Nuclear relaxation via paramagnetic impurities

    CERN Document Server

    Dzheparov, F S; Jacquinot, J F

    2002-01-01

    First part of the work contains a calculation of the kinetics of nuclear relaxation via paramagnetic impurities for systems with arbitrary (including fractal) space dimension d basing on ideas, which run current for 3d objects now. A new mean-field-type theory is constructed in the second part of the work. It reproduces all results of the first part for integer d and gives a possibility to describe the process for longer time, when a crossover to Balagurov-Waks asymptotics starts to develop. Solutions of the equations of the new theory are constructed for integer d. To obtain the solutions a method of calculation of the low-energy and long-wave asymptotics for T matrix of potential scattering out of the mass shell for singular repulsive potentials is developed

  4. Relaxing Chosen-Ciphertext Security

    DEFF Research Database (Denmark)

    Canetti, Ran; Krawczyk, Hugo; Nielsen, Jesper Buus

    2003-01-01

    Security against adaptive chosen ciphertext attacks (or, CCA security) has been accepted as the standard requirement from encryption schemes that need to withstand active attacks. In particular, it is regarded as the appropriate security notion for encryption schemes used as components within...... general protocols and applications. Indeed, CCA security was shown to suffice in a large variety of contexts. However, CCA security often appears to be somewhat too strong: there exist encryption schemes (some of which come up naturally in practice) that are not CCA secure, but seem sufficiently secure...... “for most practical purposes.” We propose a relaxed variant of CCA security, called Replayable CCA (RCCA) security. RCCA security accepts as secure the non-CCA (yet arguably secure) schemes mentioned above; furthermore, it suffices for most existing applications of CCA security. We provide three...

  5. Constraints on Black Hole/Host Galaxy Co-evolution and Binary Stalling Using Pulsar Timing Arrays

    CERN Document Server

    Simon, Joseph

    2016-01-01

    Pulsar timing arrays are now setting increasingly tight limits on the gravitational wave background from binary supermassive black holes. But as upper limits grow more constraining, what can be implied about galaxy evolution? We investigate which astrophysical parameters have the largest impact on strain spectrum predictions and provide a simple framework to directly translate between measured values for the parameters of galaxy evolution and PTA limits on the gravitational wave background of binary supermassive black holes. We find that the most influential observable is the relation between a host galaxy's central bulge and its central black hole, $\\mbox{$M_{\\bullet}$-$M_{\\rm bulge}$}$, which has the largest effect on the mean value of the characteristic strain amplitude. However, the variance of each prediction is dominated by uncertainties in the galaxy stellar mass function. Using this framework with the best published PTA limit, we can set limits on the shape and scatter of the $\\mbox{$M_{\\bullet}$-$M_{...

  6. Galaxy And Mass Assembly (GAMA) Blended Spectra Catalog: Strong Galaxy-Galaxy Lens and Occulting Galaxy Pair Candidates

    CERN Document Server

    Holwerda, B W; Alpaslan, M; Bauer, A; Bland-Hawthorn, J; Brough, S; Brown, M J I; Cluver, M E; Conselice, C; Driver, S P; Hopkins, A M; Jones, D H; Lopez-Sanchez, A R; Loveday, J; Meyer, M J; Moffett, A

    2015-01-01

    We present the catalogue of blended galaxy spectra from the Galaxy And Mass Assembly (GAMA) survey. These are cases where light from two galaxies are significantly detected in a single GAMA fibre. Galaxy pairs identified from their blended spectrum fall into two principal classes: they are either strong lenses, a passive galaxy lensing an emission-line galaxy; or occulting galaxies, serendipitous overlaps of two galaxies, of any type. Blended spectra can thus be used to reliably identify strong lenses for follow-up observations (high resolution imaging) and occulting pairs, especially those that are a late-type partly obscuring an early-type galaxy which are of interest for the study of dust content of spiral and irregular galaxies. The GAMA survey setup and its autoz automated redshift determination were used to identify candidate blended galaxy spectra from the cross-correlation peaks. We identify 280 blended spectra with a minimum velocity separation of 600 km/s, of which 104 are lens pair candidates, 71 e...

  7. Featured Image: Identifying Weird Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2017-08-01

    Hoags Object, an example of a ring galaxy. [NASA/Hubble Heritage Team/Ray A. Lucas (STScI/AURA)]The above image (click for the full view) shows PanSTARRSobservationsof some of the 185 galaxies identified in a recent study as ring galaxies bizarre and rare irregular galaxies that exhibit stars and gas in a ring around a central nucleus. Ring galaxies could be formed in a number of ways; one theory is that some might form in a galaxy collision when a smaller galaxy punches through the center of a larger one, triggering star formation around the center. In a recent study, Ian Timmis and Lior Shamir of Lawrence Technological University in Michigan explore ways that we may be able to identify ring galaxies in the overwhelming number of images expected from large upcoming surveys. They develop a computer analysis method that automatically finds ring galaxy candidates based on their visual appearance, and they test their approach on the 3 million galaxy images from the first PanSTARRS data release. To see more of the remarkable galaxies the authors found and to learn more about their identification method, check out the paper below.CitationIan Timmis and Lior Shamir 2017 ApJS 231 2. doi:10.3847/1538-4365/aa78a3

  8. The Smallest AGN Host Galaxies

    CERN Document Server

    Greene, J E; Ho, L C

    2005-01-01

    We describe our efforts to study dwarf galaxies with active nuclei, whose black holes, with masses < 10^6 M_sun, provide the best current observational constraints on the mass distribution of primordial seed black holes. Although these low-mass galaxies do not necessarily contain classical bulges, Barth, Greene, & Ho (2005) show that their stellar velocity dispersions and black hole masses obey the same relation as more massive systems. In order to characterize the properties of the dwarf hosts without the glare of the active nucleus, we have compiled a complementary sample of narrow-line active galaxies with low-mass hosts. The host galaxy properties, both their structures and stellar populations, are consistent with the general properties of low-mass, blue galaxies from Sloan. The black holes in these galaxies are probably radiating close to their Eddington limits, suggesting we may have found Type 2 analogues of narrow-line Seyfert 1 galaxies.

  9. Formation of polar ring galaxies

    CERN Document Server

    Bournaud, F

    2003-01-01

    Polar ring galaxies are peculiar systems in which a gas rich, nearly polar ring surrounds an early-type or elliptical host galaxy. Two formation scenarios for these objects have been proposed: they are thought to form either in major galaxy mergers or by tidal accretion of the polar material from a gas rich donor galaxy. Both scenarios are studied through N-body simulations including gas dynamics and star formation. Constraints on physical parameters are drawn out, in order to determine which scenario is the most likely to occur. Polar ring galaxies from each scenario are compared with observations and we discuss whether the accretion scenario and the merging scenario account for observational properties of polar ring galaxies. The conclusion of this study is that the accretion scenario is both the most likely and the most supported by observations. Even if the merging scenario is rather robust, most polar ring galaxies are shown to be the result of tidal gas accretion events.

  10. Collective Relaxation Dynamics of Small-World Networks

    CERN Document Server

    Grabow, Carsten; Kurths, Jürgen; Timme, Marc

    2015-01-01

    Complex networks exhibit a wide range of collective dynamic phenomena, including synchronization, diffusion, relaxation, and coordination processes. Their asymptotic dynamics is generically characterized by the local Jacobian, graph Laplacian or a similar linear operator. The structure of networks with regular, small-world and random connectivities are reasonably well understood, but their collective dynamical properties remain largely unknown. Here we present a two-stage mean-field theory to derive analytic expressions for network spectra. A single formula covers the spectrum from regular via small-world to strongly randomized topologies in Watts-Strogatz networks, explaining the simultaneous dependencies on network size N, average degree k and topological randomness q. We present simplified analytic predictions for the second largest and smallest eigenvalue, and numerical checks confirm our theoretical predictions for zero, small and moderate topological randomness q, including the entire small-world regime...

  11. Mass Distribution in the Central Few Parsecs of Our Galaxy

    CERN Document Server

    Oh, Seungkyung; Figer, Donald F

    2009-01-01

    We estimate the enclosed mass profile in the central 10 pc of the Milky Way by analyzing the infrared photometry and the velocity observations of dynamically relaxed stellar population in the Galactic center. HST/NICMOS and Gemini Adaptive Optics images in the archive are used to obtain the number density profile, and proper motion and radial velocity data were compiled from the literature to find the velocity dispersion profile assuming a spherical symmetry and velocity isotropy. From these data, we calculate the enclosed mass and density profiles in the central 10 pc of the Galaxy using the Jeans equation. Our improved estimates can better describe the exact evolution of the molecular clouds and star clusters falling down to the Galactic center, and constrain the star formation history of the inner part of the Galaxy.

  12. H I Asymmetries in the Isolated Galaxy CIG 292

    Science.gov (United States)

    Portas, António; Scott, Tom C.; Brinks, Elias; Bosma, Albert; Verdes-Montenegro, Lourdes; Heesen, Volker; Espada, Daniel; Verley, Simon; Sulentic, Jack; Sengupta, Chandreyee; Athanassoula, E.; Yun, Min

    2011-09-01

    We present Expanded Very Large Array (EVLA) D-array observations of the 21 cm line of neutral hydrogen (H I) of CIG 292, an isolated SA(s)b galaxy at a distance of ~24.3 Mpc. From previous H I single dish observations the galaxy was known to have a mildly asymmetric H I profile (A flux = 1.23 ± 0.3). Our EVLA observations show there is ~12% more H I projected south of the optical center (approaching velocities) than in the north (receding velocities), despite the H I extending ~16% further to the north than the south. The H I projected within the optical disk must have been perturbed within the H I relaxation time (~108 yr) which implies that this cannot have been caused by any of the three nearest companions, as their distance (~0.5 Mpc) is too large. Neither H I-rich companions nor tidal tails were found within our field of view and velocity range covered. Our kinematical data suggest that the inner part harbors an oval distortion whereas the outer regions show signs of a modest warp. The mild asymmetry in the H I global profile thus actually masks stronger asymmetries in the two-dimensional distributions of gas and star-forming regions in this galaxy. Since the galaxy is isolated, this must predominantly be due to processes related to its formation and secular evolution.

  13. Tracy-Widom statistic for the largest eigenvalue of autoscaled real matrices

    NARCIS (Netherlands)

    Saccenti, E.; Smilde, A.K.; Westerhuis, J.A.; Hendriks, M.M.W.B.

    2011-01-01

    Eigenanalysis is common practice in biostatistics, and the largest eigenvalue of a data set contains valuable information about the data. However, to make inferences about the size of the largest eigenvalue, its distribution must be known. Johnstone's theorem states that the largest eigenvalues l1 o

  14. Featured Image: Interacting Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2017-06-01

    This beautiful image shows two galaxies, IC 2163 and NGC 2207, as they undergo a grazing collision 114 million light-years away. The image is composite, constructed from Hubble (blue), Spitzer (green), and ALMA (red) data. In a recent study, Debra Elmegreen (Vassar College) and collaborators used this ALMA data to trace the individual molecular clouds in the two interacting galaxies, identifying a total of over 200 clouds that each contain a mass of over a million solar masses. These clouds represent roughly half the molecular gas in the two galaxies total. Elmegreen and collaborators track the properties of these clouds and their relation to star-forming regions observed with Hubble. For more information about their observations, check out the paper linked below.A closer look at the ALMA observations for these galaxies, with the different emission regions labeled. Most of the molecular gas emission comes from the eyelids of IC 2163, and the nuclear ring and Feature i in NGC 2207. [Elmegreen et al. 2017]CitationDebra Meloy Elmegreen et al 2017 ApJ 841 43. doi:10.3847/1538-4357/aa6ba5

  15. Cosmography with Galaxy Clusters

    CERN Document Server

    Soares-Santos, M; La Barbera, F; Lopes, P A A; Annis, J

    2008-01-01

    In the present work we focus on future experiments using cluster abundance observations to constraint the Dark Energy equation of state parameter, w. To obtain tight constraints from this kind of experiment, a reliable sample of galaxy clusters must be obtained from deep and wide-field images. We therefore present the computational environment (2DPHOT) that allow us to build the galaxy catalog from the images and the Voronoi Tessellation cluster finding algorithm that we use to identify the galaxy clusters on those catalogs. To test our pipeline with data similar in quality to what will be gathered by future wide field surveys, we process images from the Deep fields obtained as part of the LEGACY Survey (four fields of one square degree each, in five bands, with depth up to r'=25). We test our cluster finder by determining the completeness and purity of the finder when applied to mock galaxy catalogs made for the Dark Energy Survey cluster finder comparison project by Risa Wechsler and Michael Busha. This pro...

  16. The Hooked Galaxy

    Science.gov (United States)

    2006-06-01

    Life is not easy, even for galaxies. Some indeed get so close to their neighbours that they get rather distorted. But such encounters between galaxies have another effect: they spawn new generations of stars, some of which explode. ESO's VLT has obtained a unique vista of a pair of entangled galaxies, in which a star exploded. Because of the importance of exploding stars, and particularly of supernovae of Type Ia [1], for cosmological studies (e.g. relating to claims of an accelerated cosmic expansion and the existence of a new, unknown, constituent of the universe - the so called 'Dark Energy'), they are a preferred target of study for astronomers. Thus, on several occasions, they pointed ESO's Very Large Telescope (VLT) towards a region of the sky that portrays a trio of amazing galaxies. MCG-01-39-003 (bottom right) is a peculiar spiral galaxy, with a telephone number name, that presents a hook at one side, most probably due to the interaction with its neighbour, the spiral galaxy NGC 5917 (upper right). In fact, further enhancement of the image reveals that matter is pulled off MCG-01-39-003 by NGC 5917. Both these galaxies are located at similar distances, about 87 million light-years away, towards the constellation of Libra (The Balance). ESO PR Photo 22/06 ESO PR Photo 22/06 The Hooked Galaxy and its Companion NGC 5917 (also known as Arp 254 and MCG-01-39-002) is about 750 times fainter than can be seen by the unaided eye and is about 40,000 light-years across. It was discovered in 1835 by William Herschel, who strangely enough, seems to have missed its hooked companion, only 2.5 times fainter. As seen at the bottom left of this exceptional VLT image, a still fainter and nameless, but intricately beautiful, barred spiral galaxy looks from a distance the entangled pair, while many 'island universes' perform a cosmic dance in the background. But this is not the reason why astronomers look at this region. Last year, a star exploded in the vicinity of the hook

  17. Outskirts of galaxies

    CERN Document Server

    Lee, Janice; Paz, Armando

    2017-01-01

    This book consists of invited reviews written by world-renowned experts on the subject of the outskirts of galaxies, an upcoming field which has been understudied so far. These regions are faint and hard to observe, yet hide a tremendous amount of information on the origin and early evolution of galaxies. They thus allow astronomers to address some of the most topical problems, such as gaseous and satellite accretion, radial migration, and merging. The book is published in conjunction with the celebration of the end of the four-year DAGAL project, an EU-funded initial training network, and with a major international conference on the topic held in March 2016 in Toledo. It thus reflects not only the views of the experts, but also the scientific discussions and progress achieved during the project and the meeting. The reviews in the book describe the most modern observations of the outer regions of our own Galaxy, and of galaxies in the local and high-redshift Universe. They tackle disks, haloes, streams, and a...

  18. Slowly cooking galaxies

    Science.gov (United States)

    Legrand, François

    2000-07-01

    Recent spectroscopic observations of IZw 18 have revealed homogeneous abundance throughout the galaxy and several observations of other starburst galaxies have shown no significant gradient or discontinuity in the abundance distributions within the H II regions. I thus concur with Tenorio-Tagle G., 1996, AJ 111, 1641 and Devost D., Roy J.R., Drissen L., 1997, ApJ 482, 765, that these observed abundance homogeneities cannot be produced by the material ejected from the stars formed in the current burst and result from a previous star-formation episode. Metals ejected in the current burst of star formation remain most probably hidden in a hot phase and are undetectable using optical spectroscopy. Combining various observational facts, for instance, the faint star-formation rate observed in low surface brightness galaxies, Van Zee L., Haynes M.P., Salzer J.J., Broeils A.H., 1997c, AJ 113, 1618. I propose that a low and continuous star-formation rate, occurring during quiescent phases between bursts, is a non negligible source of new elements in the interstellar medium. Using a spectrophotometric and chemical evolution model for galaxies, I investigated the star formation history IZw 18. I demonstrate that the continuous star formation scenario reproduces all the observed parameters of IZw 18. I discuss the consequences of such a quiet star-formation regime.

  19. The Faintest Galaxies

    NARCIS (Netherlands)

    Salvadori, Stefania; Ferrara, Andrea; Whalen, D; Bromm,; Yoshida, N

    2010-01-01

    We investigate the nature of ultra faint dwarf spheroidal galaxies (UF dSphs) in a general cosmological context, simultaneously accounting for various ``classical'' dSphs and Milky Way (MW) properties, including their metallicity distribution function (MDF). Our model successfully reproduces both

  20. Explosions during galaxy formation

    Directory of Open Access Journals (Sweden)

    Hugo Martel

    2001-01-01

    Full Text Available As an idealized model of the e ects of energy release by supernovae during galaxy formation, we consider an explosion at the center of a halo which forms at the intersection of laments in the plane of a cosmological pancake by gravitational instability during pancake collapse. Such halos resemble the virialized objects found in N{body simulations in a CDM universe and, therefore, serve as a convenient, scale{free test{bed model for galaxy formation. ASPH=P3M simulations reveal that such explosions are anisotropic. The energy and metals are channeled into the low density regions, away from the pancake plane. The pancake remains essentially undisturbed, even if the explosion is strong enough to blow away all the gas lo- cated inside the halo at the onset of the explosion and reheat the IGM surrounding the pancake. Infall quickly replenishes this ejected gas and gradually restores the gas fraction as the halo mass continues to grow. Estimates of the collapse epoch and SN energy{release for galaxies of di erent mass in the CDM model can re- late these results to scale{dependent questions of blow{out and blow{away and their implication for early IGM heating and metal enrichment and the creation of dark{matter{dominated dwarf galaxies.

  1. Galaxy Disks are Submaximal

    NARCIS (Netherlands)

    Bershady, Matthew A.; Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Andersen, David R.; Swaters, Rob A.

    2011-01-01

    We measure the contribution of galaxy disks to the overall gravitational potential of 30 nearly face-on intermediate-to-late-type spirals from the DiskMass Survey. The central vertical velocity dispersion of the disk stars (sigma(disk)(z,R=0)) is related to the maximum rotation speed (V-max) as sigm

  2. Discovering Teenage Galaxies

    Science.gov (United States)

    2007-11-01

    Staring for the equivalent of every night for two weeks at the same little patch of sky with ESO's Very Large Telescope, an international team of astronomers has found the extremely faint light from teenage galaxies billions of light years away. These galaxies, which the research team believes are the building blocks of normal galaxies like our Milky Way, had eluded detection for three decades, despite intensive searches. ESO PR Photo 52/07 ESO PR Photo 52/07 A 92-hour long spectrum Two-dimensional spectrum obtained in 92 hours of exposure time, showing the line emitter candidates. The quasar absorption lines are visible close to the centre of the image. The team, led by Martin Haehnelt of the University of Cambridge, UK, Michael Rauch and George Becker of the Observatories of the Carnegie Institution, USA, and Andy Bunker of the Anglo-Australian Observatory, reports their results in the 1 March 2008 issue of the Astrophysical Journal. "This is the first time that the sky has been searched to this depth and the unrivalled sensitivity of the picture taken with the VLT was key to succeeding," says Haehnelt. Experts have long speculated that galaxies like ours were created by the amalgamation of proto-galaxies early in the history of the Universe, but the light from these fragments was so faint that astronomers had struggled to prove they were there at all. Astronomers thought that the teenage galaxies must be out there because they were blocking part of the light from objects even further away in space. "Previous attempts have usually been frustrated by the difficulty of detecting extremely faint objects: the amount of time required even with an 8-metre class telescope like the VLT considerably exceeds typical observing time awards. We have thus exploited the periods of less good weather with the FORS2 spectrograph at the VLT, taking advantage of the service observing mode," says Becker. In service mode, ESO staff astronomers at Paranal are responsible for carrying

  3. The Fundamental Planes of E+A galaxies and GALEX UV-excess early-type galaxies: revealing their intimate connection

    Science.gov (United States)

    Choi, Yumi; Goto, Tomotsugu; Yoon, Suk-Jin

    2009-05-01

    Strong Balmer absorption lines and the lack of Hα and [OII] emission lines signify that E+A galaxies are post-starburst systems. Recent studies suggest that E+As may undergo the transition from the `blue cloud' to the `red sequence' and eventually migrate to red-sequence early-type galaxies. An observational validation of this scenario is to identify the intervening galaxy population between E+As and the red sequence. Motivated by recent findings with Galaxy Evolution Explorer (GALEX) that an unexpectedly large fraction of early-type galaxies exhibit ultraviolet (UV) excess (i.e. blue UV - optical colours) as a sign of recent star formation (RSF), we investigate the possible connection of the UV-excess galaxies to E+As. In particular, we examine the Fundamental Plane (FP) scaling relations of the currently largest sample of ~1000 E+As selected from the Sloan Digital Sky Survey (SDSS) and ~20000 morphologically selected SDSS early-type galaxies with GALEX UV data. The FP parameters, combined with stellar population indicators, reveal a certain group of UV-excess early types that bridge between E+As and quiescent red galaxies. The newly identified galaxies are the post-starburst systems characterized by UV-excess but no Hα emission. This is essentially a conceptual generalization of `E+A', in that the Balmer absorption line in the `E+A' definition is replaced with UV - optical colours that are far more sensitive to RSF than the Balmer lines. We refer to these UV-excess galaxies as `E+a' galaxies (named after `E+A'), which stand for elliptical (`E') galaxies with a minority of A-type (`a') young stars. The species are either (1) galaxies that experienced starbursts weaker than those observed in E+As (1 ~ 10 per cent of E+As, `mild E+As') or (2) the products of passively evolved E+As after quenching star formation quite a while ago (~1 Gyr, `old E+As'). We suggest that the latter type of E+a galaxies (i.e. old `E+As') represents the most recent arrival to the red

  4. The construction of non-spherical models of quasi-relaxed stellar systems

    CERN Document Server

    Bertin, G

    2008-01-01

    Spherical models of collisionless but quasi-relaxed stellar systems have long been studied as a natural framework for the description of globular clusters. Here we consider the construction of self-consistent models under the same physical conditions, but including explicitly the ingredients that lead to departures from spherical symmetry. In particular, we focus on the effects of the tidal field associated with the hosting galaxy. We then take a stellar system on a circular orbit inside a galaxy represented as a "frozen" external field. The equilibrium distribution function is obtained from the one describing the spherical case by replacing the energy integral with the relevant Jacobi integral in the presence of the external tidal field. Then the construction of the model requires the investigation of a singular perturbation problem for an elliptic partial differential equation with a free boundary, for which we provide a method of solution to any desired order, with explicit solutions to two orders. We outl...

  5. Green valley galaxies

    Directory of Open Access Journals (Sweden)

    Salim S.

    2014-01-01

    Full Text Available The “green valley” is a wide region separating the blue and the red peaks in the ultraviolet-optical color magnitude diagram, first revealed using GALEX UV photometry. The term was coined by Christopher Martin (Caltech, in 2005. Green valley highlights the discriminating power of UV to very low relative levels of ongoing star formation, to which the optical colors, including u−r, are insensitive. It corresponds to massive galaxies below the star-forming, “main” sequence, and therefore represents a critical tool for the study of the quenching of star formation and its possible resurgence in otherwise quiescent galaxies. This article reviews the results pertaining to (predominantly disk morphology, structure, environment, dust content and gas properties of green valley galaxies in the local universe. Their relationship to AGN is also discussed. Attention is given to biases emerging from defining the “green valley” using optical colors. We review various evolutionary scenarios and we present evidence for a new one, the quasi-static view of the green valley, in which the majority (but not all of galaxies currently in the green valley were only partially quenched in the distant past and now participate in a slow cosmic decline of star formation, which also drives down the activity on the main sequence, presumably as a result of the dwindling accretion/cooling onto galaxy disks. This emerging synthetic picture is based on the findings from Fang et al. (2012, Salim et al. (2012 and Martin et al. (2007, as well as other results.

  6. Cosmological parameter constraints from galaxy-galaxy lensing and galaxy clustering with the SDSS DR7

    CERN Document Server

    Mandelbaum, Rachel; Baldauf, Tobias; Seljak, Uros; Hirata, Christopher M; Nakajima, Reiko; Reyes, Reinabelle; Smith, Robert E

    2012-01-01

    Recent studies have shown that the cross-correlation coefficient between galaxies and dark matter is very close to unity on scales outside a few virial radii of galaxy halos, independent of the details of how galaxies populate dark matter halos. This finding makes it possible to determine the dark matter clustering from measurements of galaxy-galaxy weak lensing and galaxy clustering. We present new cosmological parameter constraints based on large-scale measurements of spectroscopic galaxy samples from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We generalise the approach of Baldauf et al. (2010) to remove small scale information (below 2 and 4 Mpc/h for lensing and clustering measurements, respectively), where the cross-correlation coefficient differs from unity. We derive constraints for three galaxy samples covering 7131 sq. deg., containing 69150, 62150, and 35088 galaxies with mean redshifts of 0.11, 0.28, and 0.40. We clearly detect scale-dependent galaxy bias for the more luminous galaxy...

  7. A law for star formation in galaxies

    CERN Document Server

    Escala, Andres

    2011-01-01

    We study the galactic-scale triggering of star formation. We find that the largest mass-scale not stabilized by rotation, a well defined quantity in a rotating system and with clear dynamical meaning, strongly correlates with the star formation rate in a wide range of galaxies. We find that this relation can be understood in terms of self-regulation towards marginal Toomre stability and the amount of turbulence allowed to sustain the system in this self-regulated quasi-stationary state. We test such an interpretation by computing the predicted star formation rates for a galactic interstellar medium characterized by lognormal probability distribution function and find good agreement with the observed relation.

  8. Superparamagnetic relaxation of weakly interacting particles

    DEFF Research Database (Denmark)

    Mørup, Steen; Tronc, Elisabeth

    1994-01-01

    The influence of particle interactions on the superparamagnetic relaxation time has been studied by Mossbauer spectroscopy in samples of maghemite (gamma-Fe2O3) particles with different particle sizes and particle separations. It is found that the relaxation time decreases with decreasing particl...

  9. Postextrasystolic relaxation in the dog heart

    NARCIS (Netherlands)

    Kuijer, P.J.P.; Heethaar, R.M.; Herbschleb, J.N.; Zimmerman, A.N.E.; Meijler, F.L.

    1978-01-01

    Left ventricular relaxation was studied in 8 dogs using parameters derived from the left ventricular pressure: the fastest pressure fall and the time constant of pressure decline. Effects of extrasystolic rhythm interventions were examined on the relaxation parameters of the post-relative to the pre

  10. Superparamagnetic relaxation in alpha-Fe particles

    DEFF Research Database (Denmark)

    Bødker, Franz; Mørup, Steen; Pedersen, Michael Stanley;

    1998-01-01

    The superparamagnetic relaxation time of carbon-supported alpha-Fe particles with an average size of 3.0 Mm has been studied over a large temperature range by the use of Mossbauer spectroscopy combined with AC and DC magnetization measurements. It is found that the relaxation time varies with tem...

  11. Cross relaxation in nitroxide spin labels

    DEFF Research Database (Denmark)

    Marsh, Derek

    2016-01-01

    -label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We, the intrinsic spin-lattice relaxation rate. Independence of the saturation recovery rates from...

  12. Magnetization Transfer Induced Biexponential Longitudinal Relaxation

    Science.gov (United States)

    Prantner, Andrew M.; Bretthorst, G. Larry; Neil, Jeffrey J.; Garbow, Joel R.; Ackerman, Joseph J.H.

    2009-01-01

    Longitudinal relaxation of brain water 1H magnetization in mammalian brain in vivo is typically analyzed on a per voxel basis using a monoexponential model, thereby assigning a single relaxation time constant to all 1H magnetization within a given voxel. This approach was tested by obtaining inversion recovery data from grey matter of rats at 64 exponentially-spaced recovery times. Using Bayesian probability for model selection, brain water data were best represented by a biexponential function characterized by fast and slow relaxation components. At 4.7 T, the amplitude fraction of the rapidly relaxing component is 3.4 ± 0.7 % with a rate constant of 44 ± 12 s-1 (mean ± SD; 174 voxels from 4 rats). The rate constant of the slow relaxing component is 0.66 ± 0.04 s-1. At 11.7 T, the corresponding values are 6.9 ± 0.9 %, 19 ± 5 s-1, and 0.48 ± 0.02 s-1 (151 voxels from 4 rats). Several putative mechanisms for biexponential relaxation behavior were evaluated, and magnetization transfer between bulk water protons and non-aqueous protons was determined to be the source of biexponential longitudinal relaxation. MR methods requiring accurate quantification of longitudinal relaxation may need to take this effect explicitly into account. PMID:18759367

  13. Windowing Waveform Relaxation of Initial Value Problems

    Institute of Scientific and Technical Information of China (English)

    Yao-lin Jiang

    2006-01-01

    We present a windowing technique of waveform relaxation for dynamic systems. An effective estimation on window length is derived by an iterative error expression provided here. Relaxation processes can be speeded up if one takes the windowing technique in advance. Numerical experiments are given to further illustrate the theoretical analysis.

  14. Isolated Galaxies and Isolated Satellite Systems

    CERN Document Server

    Ann, H B; Choi, Yun-Young

    2009-01-01

    We search for isolated galaxies using a volume-limited sample of galaxies with 0.02r_{vir,nei} and \\rho <\\bar{\\rho} well segregates the CIG galaxies. We confirm the morphology conformity between the host and their satellites, which suggests importance of hydrodynamic interaction among galaxies within their virial radii in galaxy evolution.

  15. Stress Relaxation in Entangled Polymer Melts

    DEFF Research Database (Denmark)

    Hou, Ji-Xuan; Svaneborg, Carsten; Everaers, Ralf

    2010-01-01

    We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements and into the t......We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements...... and into the terminal relaxation regime for Z=10. Using the known (Rouse) mobility of unentangled chains and the melt entanglement length determined via the primitive path analysis of the microscopic topological state of our systems, we have performed parameter-free tests of several different tube models. We find...

  16. Stress and Relaxation in Relation to Personality

    Directory of Open Access Journals (Sweden)

    Harish Kumar Sharma

    2011-09-01

    Full Text Available Relaxation plays a significant role in facing stress. The aim of the present study is to see whether personality patterns determine an individual’s ability to relax. As a reaction to stress, coping is the best way to handle stress, which requires rational and conscious thinking. Does this ability to relax anyway facilitate coping reactions? A study was conducted on 100 college students. Results revealed that extraverts relax easily than introverts. In addition, if intelligence level is average or above average, relaxation does play a role in facilitating coping reactions. It suggests that in designing techniques of stress management, the personality and intelligence level must be taken into consideration to make techniques effective.

  17. The CALIFA survey across the Hubble sequence. Spatially resolved stellar population properties in galaxies

    Science.gov (United States)

    González Delgado, R. M.; García-Benito, R.; Pérez, E.; Cid Fernandes, R.; de Amorim, A. L.; Cortijo-Ferrero, C.; Lacerda, E. A. D.; López Fernández, R.; Vale-Asari, N.; Sánchez, S. F.; Mollá, M.; Ruiz-Lara, T.; Sánchez-Blázquez, P.; Walcher, C. J.; Alves, J.; Aguerri, J. A. L.; Bekeraité, S.; Bland-Hawthorn, J.; Galbany, L.; Gallazzi, A.; Husemann, B.; Iglesias-Páramo, J.; Kalinova, V.; López-Sánchez, A. R.; Marino, R. A.; Márquez, I.; Masegosa, J.; Mast, D.; Méndez-Abreu, J.; Mendoza, A.; del Olmo, A.; Pérez, I.; Quirrenbach, A.; Zibetti, S.

    2015-09-01

    Various different physical processes contribute to the star formation and stellar mass assembly histories of galaxies. One important approach to understanding the significance of these different processes on galaxy evolution is the study of the stellar population content of today's galaxies in a spatially resolved manner. The aim of this paper is to characterize in detail the radial structure of stellar population properties of galaxies in the nearby universe, based on a uniquely large galaxy sample, considering the quality and coverage of the data. The sample under study was drawn from the CALIFA survey and contains 300 galaxies observed with integral field spectroscopy. These cover a wide range of Hubble types, from spheroids to spiral galaxies, while stellar masses range from M⋆ ~ 109 to 7 × 1011 M⊙. We apply the fossil record method based on spectral synthesis techniques to recover the following physical properties for each spatial resolution element in our target galaxies: the stellar mass surface density (μ⋆), stellar extinction (AV), light-weighted and mass-weighted ages (⟨log age⟩L, ⟨log age⟩M), and mass-weighted metallicity (⟨log Z⋆⟩M). To study mean trends with overall galaxy properties, the individual radial profiles are stacked in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc, and Sd). We confirm that more massive galaxies are more compact, older, moremetal rich, and less reddened by dust. Additionally, we find that these trends are preserved spatially with the radial distance to the nucleus. Deviations from these relations appear correlated with Hubble type: earlier types are more compact, older, and more metal rich for a given M⋆, which is evidence that quenching is related to morphology, but not driven by mass. Negative gradients of ⟨log age⟩L are consistent with an inside-out growth of galaxies, with the largest ⟨log age⟩L gradients in Sb-Sbc galaxies. Further, the mean stellar ages of disks and bulges are

  18. IR Colors and Sizes of Faint Galaxies

    CERN Document Server

    Saracco, P; Moorwood, A F M; Buzzoni, A; Cuby, J G; Lidman, C E

    1999-01-01

    We present J and Ks band galaxy counts down to J=24 and Ks=22.5 obtained with the new infrared imager/spectrometer, SOFI, at the ESO New Technology Telescope. The co-addition of short, dithered, images led to a total exposure time of 256 and 624 minutes respectively, over an area of $\\sim20$ arcmin$^2$ centered on the NTT Deep Field. The total number of sources with S/N$>5$ is 1569 in the J sample and 1025 in the Ks-selected sample. These are the largest samples currently available at these depths. A d$logN$/d$m$ relation with slope of $\\sim0.36$ in J and $\\sim0.38$ in Ks is found with no evident sign of a decline at the magnitude limit. The observed surface density of ``small'' sources is much lower than ``large'' ones at bright magnitudes and rises more steeply than the large sources to fainter magnitudes. Fainter than $J\\sim22.5$ and Ks$\\sim21.5$, small sources dominate the number counts. Galaxies get redder in J-K down to J$\\sim20$ and Ks$\\sim19$. At fainter magnitudes, the median color becomes bluer with...

  19. A pseudo-spectrum analysis of galaxy-galaxy lensing

    Science.gov (United States)

    Hikage, Chiaki; Oguri, Masamune

    2016-10-01

    We present the application of the pseudo-spectrum method to galaxy-galaxy lensing. We derive explicit expressions for the pseudo-spectrum analysis of the galaxy-shear cross-spectrum, which is the Fourier space counterpart of the stacked galaxy-galaxy lensing profile. The pseudo-spectrum method corrects observational issues such as the survey geometry, masks of bright stars and their spikes, and inhomogeneous noise, which distort the spectrum and also mix the E-mode and the B-mode signals. Using ray-tracing simulations in N-body simulations including realistic masks, we confirm that the pseudo-spectrum method successfully recovers the input galaxy-shear cross-spectrum. We also show that the galaxy-shear cross-spectrum has an excess covariance relative to the Gaussian covariance at small scales (k ≳ 1h Mpc-1) where the shot noise is dominated in the Gaussian approximation. We find that the excess is consistent with the expectation from the halo sample variance (HSV), which originates from the matter fluctuations at scales larger than the survey area. We apply the pseudo-spectrum method to the observational data of Canada-France-Hawaii Telescope Lensing survey shear catalogue and three different spectroscopic samples of Sloan Digital Sky Survey Luminous Red Galaxy, and Baryon Oscillation Spectroscopic Survey CMASS and LOWZ galaxies. The galaxy-shear cross-spectra are significantly detected at the level of 7-10σ using the analytic covariance with the HSV contribution included. We also confirm that the observed spectra are consistent with the halo model predictions with the halo occupation distribution parameters estimated from previous work. This work demonstrates the viability of galaxy-galaxy lensing analysis in the Fourier space.

  20. Galaxies with Wolf-Rayet signatures in the low-redshift Universe - A survey using the Sloan Digital Sky Survey

    CERN Document Server

    Brinchmann, J; Durret, F

    2008-01-01

    We have carried out a search for Wolf-Rayet galaxies in all galaxies with EW(Hb)>2AA in the SDSS DR6. We identify Wolf-Rayet features using a mixture of automatic and visual classification and find a total of 570 galaxies with significant Wolf-Rayet (WR) features and a further 1115 potential candidates, several times more than even the largest heterogeneously assembled catalogues. We discuss in detail the properties of galaxies showing Wolf-Rayet features with a focus on their empirical properties. We are able to accurately quantify the incidence of Wolf-Rayet galaxies with redshift and show that the likelihood of otherwise similar galaxies showing Wolf-Rayet features increases with increasing metallicity, but that WR features are found in galaxies of a wide range in morphology. The large sample allows us to show explicitly that there are systematic differences in the metal abundances of WR and non-WR galaxies. The most striking result is that, below EW(Hb)=100AA, Wolf-Rayet galaxies show an elevated N/O rela...

  1. Domain Relaxation in Langmuir Films

    Science.gov (United States)

    Bernoff, Andrew J.; Alexander, James C.; Mann, Elizabeth K.; Mann, J. Adin; Zou, Lu; Wintersmith, Jacob R.

    2007-11-01

    We report on an experimental, theoretical and computational study of a molecularly thin polymer Langmuir layer domain on the surface of a subfluid. When stretched (by a transient stagnation flow), the Langmuir layer takes the form of a bola consisting of two roughly circular reservoirs connected by a thin tether. This shape relaxes to the circular minimum energy configuration. The tether is never observed to rupture, even when it is more than a hundred times as long as it is thin. We model these experiments as a free boundary problem where motion is driven by the line tension of the domain and damped by the viscosity of the subfluid. We process the digital images of the experiment to extract the domain shape, use one of these shapes as an initial condition for the numerical solution of a boundary-integral model of the underlying hydrodynamics, and compare the subsequent images of the experiment to the numerical simulation. The numerical evolutions verify that our hydrodynamical model can reproduce the observed dynamics. They also allow us to deduce the magnitude of the line tension in the system, often to within 1%.

  2. Supervised Discrete Hashing With Relaxation.

    Science.gov (United States)

    Gui, Jie; Liu, Tongliang; Sun, Zhenan; Tao, Dacheng; Tan, Tieniu

    2016-12-29

    Data-dependent hashing has recently attracted attention due to being able to support efficient retrieval and storage of high-dimensional data, such as documents, images, and videos. In this paper, we propose a novel learning-based hashing method called ''supervised discrete hashing with relaxation'' (SDHR) based on ''supervised discrete hashing'' (SDH). SDH uses ordinary least squares regression and traditional zero-one matrix encoding of class label information as the regression target (code words), thus fixing the regression target. In SDHR, the regression target is instead optimized. The optimized regression target matrix satisfies a large margin constraint for correct classification of each example. Compared with SDH, which uses the traditional zero-one matrix, SDHR utilizes the learned regression target matrix and, therefore, more accurately measures the classification error of the regression model and is more flexible. As expected, SDHR generally outperforms SDH. Experimental results on two large-scale image data sets (CIFAR-10 and MNIST) and a large-scale and challenging face data set (FRGC) demonstrate the effectiveness and efficiency of SDHR.

  3. Spin relaxation in organic semiconductors

    Science.gov (United States)

    Bobbert, Peter

    2011-03-01

    Intriguing magnetic field effects in organic semiconductor devices have been reported: anomalous magnetoresistance in organic spin valves and large effects of small magnetic fields on the current and luminescence of organic light-emitting diodes. Influences of isotopic substitution on these effects points at the role of hyperfine coupling. We performed studies of spin relaxation in organic semiconductors based on (i) coherent spin precession of the electron spin in an effective magnetic field consisting of a random hyperfine field and an applied magnetic field and (ii) incoherent hopping of charges. These ingredients are incorporated in a stochastic Liouville equation for the dynamics of the spin density matrix of single charges as well as pairs of charges. For single charges we find a spin diffusion length that depends on the magnetic field, explaining anomalous magnetoresistance in organic spin valves. For pairs of charges we show that the magnetic field influences formation of singlet bipolarons, in the case of like charges, and singlet and triplet excitons, in the case of opposite charges. We can reproduce different line shapes of reported magnetic field effects, including recently found effects at ultra-small fields.

  4. PACS photometry of the Herschel Reference Survey: far-infrared/submillimetre colours as tracers of dust properties in nearby galaxies

    OpenAIRE

    Cortese, L.; Fritz, Jacopo; S. Bianchi; Boselli, A.; Ciesla, L.; Bendo, GJ; Boquien, M.; Roussel, H.; Baes, Maarten; Buat, V.; Clemens, M.; Cooray, A.; Cormier, D.; Davies, JI; De Looze, Ilse

    2014-01-01

    We present Herschel/PACS 100 and 160 mu m integrated photometry for the 323 galaxies in the Herschel Reference Survey (HRS), a K-band, volume-limited sample of galaxies in the local Universe. Once combined with the Herschel/SPIRE observations already available, these data make the HRS the largest representative sample of nearby galaxies with homogeneous coverage across the 100-500 mu m wavelength range. In this paper, we take advantage of this unique data set to investigate the properties and...

  5. VIPERS: An Unprecedented View of Galaxies and Large-Scale Structure Halfway Back in the Life of the Universe

    CERN Document Server

    Guzzo, L; Adami, C; Arnouts, S; Bel, J; Bolzonella, M; Bottini, D; Branchini, E; Burden, A; Cappi, A; Coupon, J; Cucciati, O; Davidzon, I; de la Torre, S; De Lucia, G; Di Porto, C; Franzetti, P; Fritz, A; Fumana, M; Garilli, B; Granett, B R; Guennou, L; Ilbert, O; Iovino, A; Krywult, J; Brun, V Le; Fèvre, O Le; Maccagni, D; Malek, K; Marchetti, A; Marinoni, C; Marulli, F; McCracken, H J; Mellier, Y; Moscardini, L; Nichol, R C; Paioro, L; Peacock, J A; Percival, W J; Phleps, S; Polletta, M; Pollo, A; Schlagenhaufer, H; Scodeggio, M; Solarz, A; Tasca, L A M; Tojeiro, R; Vergani, D; Wolk, M; Zamorani, G; Zanichelli, A

    2013-01-01

    The VIMOS Public Extragalactic Redshift Survey (VIPERS) is an ongoing ESO Large Programme to map in detail the large-scale distribution of galaxies at 0.5 < z <1.2. With a combination of volume and sampling density that is unique for these redshifts, it focuses on measuring galaxy clustering and related cosmological quantities as part of the grand challenge of understanding the origin of cosmic acceleration. VIPERS has also been designed to guarantee a broader legacy, allowing detailed investigations of the properties and evolutionary trends of z~1 galaxies. The survey strategy exploits the specific advantages of the VIMOS spectrograph at the VLT, aiming at a final sample of nearly 100,000 galaxy redshifts to iAB = 22.5 mag, which represents the largest redshift survey ever performed with ESO telescopes. In this introductory article we describe the survey construction, together with early results based on a first sample of ~55,000 galaxies.

  6. Host Galaxy Spectra and Consequences for SN Typing from the SDSS SN Survey

    Energy Technology Data Exchange (ETDEWEB)

    Olmstead, Matthew D.; Brown, Peter J.; Sako, Masao; Bassett, Bruce; Bizyaev, Dmitry; Brinkmann, J.; Brownstein, Joel R.; Brewington, Howard; Campbell, Heather; D’Andrea, Chris B.; Dawson, Kyle S.; Ebelke, Garrett L.; Frieman, Joshua A.; Galbany, Lluís; Garnavich, Peter; Gupta, Ravi R.; Hlozek, Renee; Jha, Saurabh W.; Kunz, Martin; Lampeitl, Hubert; Malanushenko, Elena; Malanushenko, Viktor; Marriner, John; Miquel, Ramon; Montero-Dorta, Antonio D.; Nichol, Robert C.; Oravetz, Daniel J.; Pan, Kaike; Schneider, Donald P.; Simmons, Audrey E.; Smith, Mathew; Snedden, Stephanie A.

    2014-03-06

    We present the spectroscopy from 5254 galaxies that hosted supernovae (SNe) or other transient events in the Sloan Digital Sky Survey II (SDSS-II). Obtained during SDSS-I, SDSS-II, and the Baryon Oscillation Spectroscopic Survey (BOSS), this sample represents the largest systematic, unbiased, magnitude limited spectroscopic survey of supernova (SN) host galaxies. Using the host galaxy redshifts, we test the impact of photometric SN classification based on SDSS imaging data with and without using spectroscopic redshifts of the host galaxies. Following our suggested scheme, there are a total of 1166 photometrically classified SNe Ia when using a flat redshift prior and 1126 SNe Ia when the host spectroscopic redshift is assumed. For 1024 (87.8%) candidates classified as likely SNe Ia without redshift information, we find that the classification is unchanged when adding the host galaxy redshift. Using photometry from SDSS imaging data and the host galaxy spectra, we also report host galaxy properties for use in future nalysis of SN astrophysics. Finally, we investigate the differences in the interpretation of the light curve properties with and without knowledge of the redshift. When using the SALT2 light curve fitter, we find a 21% increase in the number of fits that converge when using the spectroscopic redshift. Without host galaxy redshifts, we find that SALT2 light curve fits are systematically biased towards lower photometric redshift estimates and redder colors in the limit of low signal-to-noise data. The general improvements in performance of the light curve fitter and the increased diversity of the host galaxy sample highlights the importance of host galaxy spectroscopy for current photometric SN surveys such as the Dark Energy Survey and future surveys such as the Large Synoptic Survey Telescope.

  7. Recent galaxy mergers and residual star formation of red sequence galaxies in galaxy clusters

    CERN Document Server

    Sheen, Yun-Kyeong; Ree, Chang H; Jaffé, Yara; Demarco, Ricardo; Treister, Ezequiel

    2016-01-01

    This study explored the GALEX ultraviolet (UV) properties of optical red sequence galaxies in 4 rich Abell clusters at z \\leq 0.1. In particular, we tried to find a hint of merger-induced recent star formation (RSF) in red sequence galaxies. Using the NUV - r' colors of the galaxies, RSF fractions were derived based on various criteria for post-merger galaxies and normal galaxies. Following k-correction, about 36% of the post-merger galaxies were classified as RSF galaxies with a conservative criterion (NUV - r' \\leq 5), and that number was doubled (~ 72%) when using a generous criterion (NUV - r' \\leq 5.4). The trend was the same when we restricted the sample to galaxies within 0.5xR_{200}. Post-merger galaxies with strong UV emission showed more violent, asymmetric features in the deep optical images. The RSF fractions did not show any trend along the clustocentric distance within R_{200}. We performed a Dressler-Shectman test to check whether the RSF galaxies had any correlation with the sub-structures in ...

  8. Galaxy bias from galaxy-galaxy lensing in the DES Science Verification Data

    CERN Document Server

    Prat, J; Miquel, R; Kwan, J; Blazek, J; Bonnett, C; Amara, A; Bridle, S L; Clampitt, J; Crocce, M; Fosalba, P; Gaztanaga, E; Giannantonio, T; Hartley, W G; Jarvis, M; MacCrann, N; Percival, W J; Ross, A J; Sheldon, E; Zuntz, J; Abbott, T M C; Abdalla, F B; Annis, J; Benoit-Lévy, A; Bertin, E; Brooks, D; Burke, D L; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Castander, F J; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Doel, P; Eifler, T F; Evrard, A E; Neto, A Fausti; Flaugher, B; Frieman, J; Gerdes, D W; Gruen, D; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Kuehn, K; Kuropatkin, N; Lahav, O; Lima, M; Marshall, J L; Melchior, P; Menanteau, F; Nord, B; Plazas, A A; Reil, K; Romer, A K; Roodman, A; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla-Noarbe, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thomas, D; Walker, A R

    2016-01-01

    We present a measurement of galaxy-galaxy lensing around a magnitude-limited ($i_{AB} < 22.5$) sample of galaxies selected from the Dark Energy Survey Science Verification (DES-SV) data. We split these lenses into three photometric-redshift bins from 0.2 to 0.8, and determine the product of the galaxy bias $b$ and cross-correlation coefficient between the galaxy and dark matter overdensity fields $r$ in each bin, using scales above 4 Mpc/$h$ comoving, where we find the linear bias model to be valid given our current uncertainties. We compare our galaxy bias results from galaxy-galaxy lensing with those obtained from galaxy clustering (Crocce et al. 2016) and CMB lensing (Giannantonio et al. 2016) for the same sample of galaxies, and find our measurements to be in good agreement with those in Crocce et al. (2016), while, in the lowest redshift bin ($z\\sim0.3$), they show some tension with the findings in Giannantonio et al. (2016). Our results are found to be rather insensitive to a large range of systemati...

  9. Galaxy Morphology - Halo Gas Connections

    CERN Document Server

    Kacprzak, G G; Steidel, C C; Kacprzak, Glenn G.; Churchill, Christopher W.; Steidel, Charles C.

    2005-01-01

    We studied a sample of 38 intermediate redshift MgII absorption-selected galaxies using (1) Keck/HIRES and VLT/UVES quasar spectra to measure the halo gas kinematics from MgII absorption profiles and (2) HST/WFPC-2 images to study the absorbing galaxy morphologies. We have searched for correlations between quantified gas absorption properties, and host galaxy impact parameters, inclinations, position angles, and quantified morphological parameters. We report a 3.2-sigma correlation between asymmetric perturbations in the host galaxy morphology and the MgII absorption equivalent width. We suggest that this correlation may indicate a connection between past merging and/or interaction events in MgII absorption-selected galaxies and the velocity dispersion and quantity of gas surrounding these galaxies.

  10. Black holes and galaxy formation

    CERN Document Server

    Propst, Raphael J

    2010-01-01

    Galaxies are the basic unit of cosmology. The study of galaxy formation is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning. The physics of galaxy formation is complicated because it deals with the dynamics of stars, thermodynamics of gas and energy production of stars. A black hole is a massive object whose gravitational field is so intense that it prevents any form of matter or radiation to escape. It is hypothesized that the most massive galaxies in the universe- "elliptical galaxies"- grow simultaneously with the supermassive black holes at their centers, giving us much stronger evidence that black holes control galaxy formation. This book reviews new evidence in the field.

  11. Galaxies appear simpler than expected

    CERN Document Server

    Disney, M J; Garcia-Appadoo, D A; West, A A; Dalcanton, J J; Cortese, L

    2008-01-01

    Galaxies are complex systems the evolution of which apparently results from the interplay of dynamics, star formation, chemical enrichment, and feedback from supernova explosions and supermassive black holes. The hierarchical theory of galaxy formation holds that galaxies are assembled from smaller pieces, through numerous mergers of cold dark matter. The properties of an individual galaxy should be controlled by six independent parameters including mass, angular-momentum, baryon-fraction, age and size, as well as by the accidents of its recent haphazard merger history. Here we report that a sample of galaxies that were first detected through their neutral hydrogen radio-frequency emission, and are thus free of optical selection effects, shows five independent correlations among six independent observables, despite having a wide range of properties. This implies that the structure of these galaxies must be controlled by a single parameter, although we cannot identify this parameter from our dataset. Such a de...

  12. Supernova Feedback Keeps Galaxies Simple

    CERN Document Server

    Chakraborti, Sayan

    2011-01-01

    Galaxies evolve continuously under the influence of self-gravity, rotation, accretion, mergers and feedback. The currently favored cold dark matter cosmological framework, suggests a hierarchical process of galaxy formation, wherein the present properties of galaxies are decided by their individual histories of being assembled from smaller pieces. However, recent studies have uncovered surprising correlations among the properties of galaxies, to the extent of forming a one-parameter set lying on a single fundamental line. It has been argued in the literature that such simplicity is hard to explain within the paradigm of hierarchical galaxy mergers. One of the puzzling results, is the simple linear correlation between the neutral hydrogen mass and the surface area, implying that widely different galaxies share very similar neutral hydrogen surface densities. In this work we show that self-regulated star formation, driven by the competition between gravitational instabilities and mechanical feedback from supern...

  13. The Shocked POststarburst Galaxy Survey

    Science.gov (United States)

    Alatalo, Katherine A.; SPOGS Team

    2017-01-01

    Modern day galaxies are found to be in a bimodal distribution, both in terms of their morphologies, and in terms of their colors, and these properties are inter-related. In color space, there is a genuine dearth of intermediate colored galaxies, which has been taken to mean that the transition a galaxy undergoes to transform must be rapid. Given that this transformation is largely one-way (at z=0), identifying all initial conditions that catalyze it becomes essential. The Shocked POststarburst Galaxy Survey (http://www.spogs.org) is able to pinpoint transitioning galaxies at an earlier stage of transition than other traditional searches, possibly opening a new door to identifying new pathways over which galaxies transform from blue spirals to red ellipticals.

  14. The Star Formation Histories of Local Group Dwarf Galaxies. III. Characterizing Quenching in Low-mass Galaxies

    Science.gov (United States)

    Weisz, Daniel R.; Dolphin, Andrew E.; Skillman, Evan D.; Holtzman, Jon; Gilbert, Karoline M.; Dalcanton, Julianne J.; Williams, Benjamin F.

    2015-05-01

    We explore the quenching of low-mass galaxies (104 ≲ {{M}\\star } ≲ 108 {{M}⊙ }) as a function of lookback time using the star formation histories (SFHs) of 38 Local Group dwarf galaxies. The SFHs were derived by analyzing color-magnitude diagrams of resolved stellar populations in archival Hubble Space Telescope/Wide Field Planetary Camera 2 imaging. We find: (1) lower-mass galaxies quench earlier than higher-mass galaxies; (2) inside of Rvirial there is no correlation between a satellite’s current proximity to a massive host and its quenching epoch; and (3) there are hints of systematic differences in the quenching times of M31 and Milky Way (MW) satellites, although the sample size and uncertainties in the SFHs of M31 dwarfs prohibit definitive conclusions. Combined with results from the literature, we qualitatively consider the redshift evolution (z = 0-1) of the quenched galaxy fraction over ˜7 dex in stellar mass (104 ≲ {{M}\\star } ≲ 1011.5 {{M}⊙ }). The quenched fraction of all galaxies generally increases toward the present, with both the lowest and highest-mass systems exhibiting the largest quenched fractions at all redshifts. In contrast, galaxies between {{M}\\star } ˜ 108-1010 {{M}⊙ } have the lowest quenched fractions. We suggest that such intermediate-mass galaxies are the least efficient at quenching. Finally, we compare our quenching times with predictions for infall times for low-mass galaxies associated with the MW. We find that some of the lowest-mass satellites (e.g., CVn II, Leo IV) may have been quenched before infall, while higher-mass satellites (e.g., Leo I, Fornax) typically quench ˜1-4 Gyr after infall. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA constract NAS 5-26555.

  15. Genesis of spiral galaxies

    CERN Document Server

    Kiselev, Valery V

    2013-01-01

    Enigmatic spiral structure of many galaxies and its huge orbital momentum originated due to the capture of lightweight bare black hole by gravity of heavy primordial gas cloud at large impact parameter. The rotating of black hole caused the formation of accretion disc from the cloud and the transfer of orbital momentum to the disc, while during the fall to the center of mass, the spiral trace of black hole in the disc did create the spiral front line of sound waves in the gas, that further evolved into the stellar spiral arms. This mechanism opens the way to study features of spiral galaxy formation, say, an influence and a significance of dark matter in this process.

  16. Molecules in galaxies

    CERN Document Server

    Omont, Alain

    2007-01-01

    The main achievements, current developments and prospects of molecular studies in external galaxies are reviewed. They are put in the context of the results of several decades of studies of molecules in local interstellar medium, their chemistry and their importance for star formation. CO observations have revealed the gross structure of molecular gas in galaxies. Together with other molecules, they are among the best tracers of star formation at galactic scales. Our knowledge about molecular abundances in various local galactic environments is progressing. They trace physical conditions and metallicity, and they are closely related to dust processes and large aromatic molecules. Major recent developments include mega-masers, and molecules in Active Galactic Nuclei; millimetre emission of molecules at very high redshift; and infrared H2 emission as tracer of warm molecular gas, shocks and photodissociation regions. The advent of sensitive giant interferometers from the centimetre to sub-millimetre range, espe...

  17. The Anatomy of Galaxies

    Science.gov (United States)

    D'Onofrio, Mauro; Rampazzo, Roberto; Zaggia, Simone; Longair, Malcolm S.; Ferrarese, Laura; Marziani, Paola; Sulentic, Jack W.; van der Kruit, Pieter C.; Laurikainen, Eija; Elmegreen, Debra M.; Combes, Françoise; Bertin, Giuseppe; Fabbiano, Giuseppina; Giovanelli, Riccardo; Calzetti, Daniela; Moss, David L.; Matteucci, Francesca; Djorgovski, Stanislav George; Fraix-Burnet, Didier; Graham, Alister W. McK.; Tully, Brent R.

    Just after WWII Astronomy started to live its "Golden Age", not differently to many other sciences and human activities, especially in the west side countries. The improved resolution of telescopes and the appearance of new efficient light detectors (e.g. CCDs in the middle eighty) greatly impacted the extragalactic researches. The first morphological analysis of galaxies were rapidly substituted by "anatomic" studies of their structural components, star and gas content, and in general by detailed investigations of their properties. As for the human anatomy, where the final goal was that of understanding the functionality of the organs that are essential for the life of the body, galaxies were dissected to discover their basic structural components and ultimately the mystery of their existence.

  18. Galaxy mapping the cosmos

    CERN Document Server

    Geach, James

    2014-01-01

    Each night, we are able to gaze up at the night sky and look at the thousands of stars that stretch to the end of our individual horizons. But the stars we see are only those that make up our own Milky Way galaxy-but one of hundreds of billions in the whole of the universe, each separated  by inconceivably huge tracts of empty space. In this book, astronomer James Geach tells the rich stories of both the evolution of galaxies and our ability to observe them, offering a fascinating history of how we've come to realize humanity's tiny place in the vast universe.             Taking us on a compel

  19. Radio Galaxy Zoo: discovery of a poor cluster through a giant wide-angle tail radio galaxy

    Science.gov (United States)

    Banfield, J. K.; Andernach, H.; Kapińska, A. D.; Rudnick, L.; Hardcastle, M. J.; Cotter, G.; Vaughan, S.; Jones, T. W.; Heywood, I.; Wing, J. D.; Wong, O. I.; Matorny, T.; Terentev, I. A.; López-Sánchez, Á. R.; Norris, R. P.; Seymour, N.; Shabala, S. S.; Willett, K. W.

    2016-08-01

    We have discovered a previously unreported poor cluster of galaxies (RGZ-CL J0823.2+0333) through an unusual giant wide-angle tail radio galaxy found in the Radio Galaxy Zoo project. We obtained a spectroscopic redshift of z = 0.0897 for the E0-type host galaxy, 2MASX J08231289+0333016, leading to Mr = -22.6 and a 1.4 GHz radio luminosity density of L1.4 = 5.5 × 1024 W Hz-1. These radio and optical luminosities are typical for wide-angle tailed radio galaxies near the borderline between Fanaroff-Riley classes I and II. The projected largest angular size of ≈8 arcmin corresponds to 800 kpc and the full length of the source along the curved jets/trails is 1.1 Mpc in projection. X-ray data from the XMM-Newton archive yield an upper limit on the X-ray luminosity of the thermal emission surrounding RGZ J082312.9+033301 at 1.2-2.6 × 1043 erg s-1 for assumed intracluster medium temperatures of 1.0-5.0 keV. Our analysis of the environment surrounding RGZ J082312.9+033301 indicates that RGZ J082312.9+033301 lies within a poor cluster. The observed radio morphology suggests that (a) the host galaxy is moving at a significant velocity with respect to an ambient medium like that of at least a poor cluster, and that (b) the source may have had two ignition events of the active galactic nucleus with 107 yr in between. This reinforces the idea that an association between RGZ J082312.9+033301 and the newly discovered poor cluster exists.

  20. Quantitative analysis of spirality in elliptical galaxies

    CERN Document Server

    Dojcsak, Levente

    2013-01-01

    We use an automated galaxy morphology analysis method to quantitatively measure the spirality of galaxies classified manually as elliptical. The data set used for the analysis consists of 60,518 galaxy images with redshift obtained by the Sloan Digital Sky Survey (SDSS) and classified manually by Galaxy Zoo, as well as the RC3 and NA10 catalogues. We measure the spirality of the galaxies by using the Ganalyzer method, which transforms the galaxy image to its radial intensity plot to detect galaxy spirality that is in many cases difficult to notice by manual observation of the raw galaxy image. Experimental results using manually classified elliptical and S0 galaxies with redshift <0.3 suggest that galaxies classified manually as elliptical and S0 exhibit a nonzero signal for the spirality. These results suggest that the human eye observing the raw galaxy image might not always be the most effective way of detecting spirality and curves in the arms of galaxies.

  1. Structures in Galaxy Clusters

    CERN Document Server

    Escalera, E; Girardi, M; Giuricin, G; Mardirossian, F; Mazure, A; Mezzetti, M

    1993-01-01

    The analysis of the presence of substructures in 16 well-sampled clusters of galaxies suggests a stimulating hypothesis: Clusters could be classified as unimodal or bimodal, on the basis of to the sub-clump distribution in the {\\em 3-D} space of positions and velocities. The dynamic study of these clusters shows that their fundamental characteristics, in particular the virial masses, are not severely biased by the presence of subclustering if the system considered is bound.

  2. Nuclear spirals in galaxies

    OpenAIRE

    Maciejewski, Witold

    2006-01-01

    Recent high-resolution observations indicate that nuclear spirals are often present in the innermost few hundred parsecs of disc galaxies. My models show that nuclear spirals form naturally as a gas response to non-axisymmetry in the gravitational potential. Some nuclear spirals take the form of spiral shocks, resulting in streaming motions in the gas, and in inflow comparable to the accretion rates needed to power local Active Galactic Nuclei. Recently streaming motions of amplitude expected...

  3. Relaxation of a 1-D gravitational system

    CERN Document Server

    Valageas, P

    2006-01-01

    We study the relaxation towards thermodynamical equilibrium of a 1-D gravitational system. This OSC model shows a series of critical energies $E_{cn}$ where new equilibria appear and we focus on the homogeneous ($n=0$), one-peak ($n=\\pm 1$) and two-peak ($n=2$) states. Using numerical simulations we investigate the relaxation to the stable equilibrium $n=\\pm 1$ of this $N-$body system starting from initial conditions defined by equilibria $n=0$ and $n=2$. We find that in a fashion similar to other long-range systems the relaxation involves a fast violent relaxation phase followed by a slow collisional phase as the system goes through a series of quasi-stationary states. Moreover, in cases where this slow second stage leads to a dynamically unstable configuration (two peaks with a high mass ratio) it is followed by a new sequence ``violent relaxation/slow collisional relaxation''. We obtain an analytical estimate of the relaxation time $t_{2\\to \\pm 1}$ through the mean escape time of a particle from its potent...

  4. Plasma Relaxation Dynamics Moderated by Current Sheets

    Science.gov (United States)

    Dewar, Robert; Bhattacharjee, Amitava; Yoshida, Zensho

    2014-10-01

    Ideal magnetohydrodynamics (IMHD) is strongly constrained by an infinite number of microscopic constraints expressing mass, entropy and magnetic flux conservation in each infinitesimal fluid element, the latter preventing magnetic reconnection. By contrast, in the Taylor-relaxed equilibrium model all these constraints are relaxed save for global magnetic flux and helicity. A Lagrangian is presented that leads to a new variational formulation of magnetized fluid dynamics, relaxed MHD (RxMHD), all static solutions of which are Taylor equilibrium states. By postulating that some long-lived macroscopic current sheets can act as barriers to relaxation, separating the plasma into multiple relaxation regions, a further generalization, multi-relaxed MHD (MRxMHD), is developed. These concepts are illustrated using a simple two-region slab model similar to that proposed by Hahm and Kulsrud--the formation of an initial shielding current sheet after perturbation by boundary rippling is calculated using MRxMHD and the final island state, after the current sheet has relaxed through a reconnection sequence, is calculated using RxMHD. Australian Research Council Grant DP110102881.

  5. The Laniakea supercluster of galaxies

    OpenAIRE

    Tully, R. Brent; Courtois, Helene; Hoffman, Yehuda; Pomarède, Daniel

    2014-01-01

    Galaxies congregate in clusters and along filaments, and are missing from large regions referred to as voids. These structures are seen in maps derived from spectroscopic surveys that reveal networks of structure that are interconnected with no clear boundaries. Extended regions with a high concentration of galaxies are called 'superclusters', although this term is not precise. There is, however, another way to analyse the structure. If the distance to each galaxy from Earth is directly measu...

  6. The Automatic Galaxy Collision Software

    CERN Document Server

    Smith, Beverly J; Pfeiffer, Phillip; Perkins, Sam; Barkanic, Jason; Fritts, Steve; Southerland, Derek; Manchikalapudi, Dinikar; Baker, Matt; Luckey, John; Franklin, Coral; Moffett, Amanda; Struck, Curtis

    2009-01-01

    The key to understanding the physical processes that occur during galaxy interactions is dynamical modeling, and especially the detailed matching of numerical models to specific systems. To make modeling interacting galaxies more efficient, we have constructed the `Automatic Galaxy Collision' (AGC) code, which requires less human intervention in finding good matches to data. We present some preliminary results from this code for the well-studied system Arp 284 (NGC 7714/5), and address questions of uniqueness of solutions.

  7. Very high redshift radio galaxies

    Energy Technology Data Exchange (ETDEWEB)

    van Breugel, W.J.M., LLNL

    1997-12-01

    High redshift radio galaxies (HzRGs) provide unique targets for the study of the formation and evolution of massive galaxies and galaxy clusters at very high redshifts. We discuss how efficient HzRG samples ae selected, the evidence for strong morphological evolution at near-infracd wavelengths, and for jet-induced star formation in the z = 3 800 HzRG 4C41 17

  8. Star Formation in MUSCEL Galaxies

    Science.gov (United States)

    Young, Jason; Kuzio de Naray, Rachel; Wang, Sharon Xuesong

    2017-01-01

    We present preliminary star-formation histories for a subset of the low surface brightness (LSB) galaxies in the MUSCEL (MUltiwavelength observations of the Structure, Chemistry, and Evolution of LSB galaxies) program. These histories are fitted against ground-based IFU spectra in tandem with space-based UV and IR photometry. MUSCEL aims to use these histories along with kinematic analyses to determine the physical processes that have caused the evolution of LSB galaxies to diverge from their high surface brightness counterparts.

  9. Origin of the 12um Emission Across Galaxy Populations from WISE and SDSS Surveys

    CERN Document Server

    Donoso, E; Tsai, C; Eisenhardt, P; Stern, D; Assef, R J; Leisawitz, D; Jarrett, T H; Stanford, S A

    2012-01-01

    We cross-matched Wide-field Infrared Survey Explorer (WISE) sources brighter than 1 mJy at 12um with the Sloan Digital Sky Survey (SDSS) galaxy spectroscopic catalog to produce a sample of ~10^5 galaxies at =0.08, the largest of its kind. This sample is dominated (70%) by star-forming (SF) galaxies from the blue sequence, with total IR luminosities in the range ~10^8-10^12 L_sun. We identify which stellar populations are responsible for most of the 12um emission. We find that most (~80%) of the 12um emission in SF galaxies is produced by stellar populations younger than 0.6 Gyr. In contrast, the 12um emission in weak AGN (L[OIII]10^7 L_sun), act as an extension of massive SF galaxies, connecting the SF and weak AGN sequences. This suggests a picture where galaxies form stars normally until an AGN (possibly after a starburst episode) starts to gradually quench the SF activity. We also find that 4.6-12um color is a useful first-order indicator of SF activity in a galaxy when no other data are available.

  10. Two ten-billion-solar-mass black holes at the centres of giant elliptical galaxies.

    Science.gov (United States)

    McConnell, Nicholas J; Ma, Chung-Pei; Gebhardt, Karl; Wright, Shelley A; Murphy, Jeremy D; Lauer, Tod R; Graham, James R; Richstone, Douglas O

    2011-12-08

    Observational work conducted over the past few decades indicates that all massive galaxies have supermassive black holes at their centres. Although the luminosities and brightness fluctuations of quasars in the early Universe suggest that some were powered by black holes with masses greater than 10 billion solar masses, the remnants of these objects have not been found in the nearby Universe. The giant elliptical galaxy Messier 87 hosts the hitherto most massive known black hole, which has a mass of 6.3 billion solar masses. Here we report that NGC 3842, the brightest galaxy in a cluster at a distance from Earth of 98 megaparsecs, has a central black hole with a mass of 9.7 billion solar masses, and that a black hole of comparable or greater mass is present in NGC 4889, the brightest galaxy in the Coma cluster (at a distance of 103 megaparsecs). These two black holes are significantly more massive than predicted by linearly extrapolating the widely used correlations between black-hole mass and the stellar velocity dispersion or bulge luminosity of the host galaxy. Although these correlations remain useful for predicting black-hole masses in less massive elliptical galaxies, our measurements suggest that different evolutionary processes influence the growth of the largest galaxies and their black holes.

  11. A 17-billion-solar-mass black hole in a group galaxy with a diffuse core.

    Science.gov (United States)

    Thomas, Jens; Ma, Chung-Pei; McConnell, Nicholas J; Greene, Jenny E; Blakeslee, John P; Janish, Ryan

    2016-04-21

    Quasars are associated with and powered by the accretion of material onto massive black holes; the detection of highly luminous quasars with redshifts greater than z = 6 suggests that black holes of up to ten billion solar masses already existed 13 billion years ago. Two possible present-day 'dormant' descendants of this population of 'active' black holes have been found in the galaxies NGC 3842 and NGC 4889 at the centres of the Leo and Coma galaxy clusters, which together form the central region of the Great Wall--the largest local structure of galaxies. The most luminous quasars, however, are not confined to such high-density regions of the early Universe; yet dormant black holes of this high mass have not yet been found outside of modern-day rich clusters. Here we report observations of the stellar velocity distribution in the galaxy NGC 1600--a relatively isolated elliptical galaxy near the centre of a galaxy group at a distance of 64 megaparsecs from Earth. We use orbit superposition models to determine that the black hole at the centre of NGC 1600 has a mass of 17 billion solar masses. The spatial distribution of stars near the centre of NGC 1600 is rather diffuse. We find that the region of depleted stellar density in the cores of massive elliptical galaxies extends over the same radius as the gravitational sphere of influence of the central black holes, and interpret this as the dynamical imprint of the black holes.

  12. The EDGE-CALIFA Survey: Interferometric Observations of 126 Galaxies with CARMA

    Science.gov (United States)

    Bolatto, Alberto D.; Wong, Tony; Utomo, Dyas; Blitz, Leo; Vogel, Stuart N.; Sánchez, Sebastián F.; Barrera-Ballesteros, Jorge; Cao, Yixian; Colombo, Dario; Dannerbauer, Helmut; García-Benito, Rubén; Herrera-Camus, Rodrigo; Husemann, Bernd; Kalinova, Veselina; Leroy, Adam K.; Leung, Gigi; Levy, Rebecca C.; Mast, Damián; Ostriker, Eve; Rosolowsky, Erik; Sandstrom, Karin M.; Teuben, Peter; van de Ven, Glenn; Walter, Fabian

    2017-09-01

    We present interferometric CO observations, made with the Combined Array for Millimeter-wave Astronomy (CARMA) interferometer, of galaxies from the Extragalactic Database for Galaxy Evolution survey (EDGE). These galaxies are selected from the Calar Alto Legacy Integral Field Area (CALIFA) sample, mapped with optical integral field spectroscopy. EDGE provides good-quality CO data (3σ sensitivity {{{Σ }}}{mol}∼ 11 {M}ȯ {{pc}}-2 before inclination correction, resolution ∼1.4 kpc) for 126 galaxies, constituting the largest interferometric CO survey of galaxies in the nearby universe. We describe the survey and data characteristics and products, then present initial science results. We find that the exponential scale lengths of the molecular, stellar, and star-forming disks are approximately equal, and galaxies that are more compact in molecular gas than in stars tend to show signs of interaction. We characterize the molecular-to-stellar ratio as a function of Hubble type and stellar mass and present preliminary results on the resolved relations between the molecular gas, stars, and star-formation rate. We then discuss the dependence of the resolved molecular depletion time on stellar surface density, nebular extinction, and gas metallicity. EDGE provides a key data set to address outstanding topics regarding gas and its role in star formation and galaxy evolution, which will be publicly available on completion of the quality assessment.

  13. Accretion/Jet Activity and Narrow [O III] Kinematics in Young Radio Galaxies

    CERN Document Server

    Wu, Qingwen; Humphrey, Andrew

    2009-01-01

    We estimate black hole masses and Eddington ratios for a sample of 81 young radio galaxies (42 CSS +39 GPS). We find that the average black hole (BH) mass of these young radio galaxies is ~8.3, which is less than that of radio loud QSOs and low redshift radio galaxies. The CSS/GPS sources have relatively high Eddington ratios, with an average value of =-0.75, which are similar to those of narrow line Seyfert 1 galaxies (NLS1s). This suggests that young radio galaxies may not only be in the early stages of their radio activity, but also in the early stage of their accretion activity. We find that the young radio galaxies as a class deviate systematically from M_bh-\\sigma relation defined by nearby inactive galaxies, when using [O III] as a surrogate for stellar velocity dispersion, \\sigma_* . We also find that the deviation of the [O III] line width is correlated with the Eddington ratio and sources with Lbol/LEdd~1 have the largest deviations, which are similar to those of radio quiet QSOs/NLS1s (radio jets i...

  14. Intense star formation within resolved compact regions in a galaxy at z = 2.3.

    Science.gov (United States)

    Swinbank, A M; Smail, I; Longmore, S; Harris, A I; Baker, A J; De Breuck, C; Richard, J; Edge, A C; Ivison, R J; Blundell, R; Coppin, K E K; Cox, P; Gurwell, M; Hainline, L J; Krips, M; Lundgren, A; Neri, R; Siana, B; Siringo, G; Stark, D P; Wilner, D; Younger, J D

    2010-04-01

    Massive galaxies in the early Universe have been shown to be forming stars at surprisingly high rates. Prominent examples are dust-obscured galaxies which are luminous when observed at sub-millimetre wavelengths and which may be forming stars at a rate of 1,000 solar masses (M(middle dot in circle)) per year. These intense bursts of star formation are believed to be driven by mergers between gas-rich galaxies. Probing the properties of individual star-forming regions within these galaxies, however, is beyond the spatial resolution and sensitivity of even the largest telescopes at present. Here we report observations of the sub-millimetre galaxy SMMJ2135-0102 at redshift z = 2.3259, which has been gravitationally magnified by a factor of 32 by a massive foreground galaxy cluster lens. This magnification, when combined with high-resolution sub-millimetre imaging, resolves the star-forming regions at a linear scale of only 100 parsecs. We find that the luminosity densities of these star-forming regions are comparable to the dense cores of giant molecular clouds in the local Universe, but they are about a hundred times larger and 10(7) times more luminous. Although vigorously star-forming, the underlying physics of the star-formation processes at z approximately 2 appears to be similar to that seen in local galaxies, although the energetics are unlike anything found in the present-day Universe.

  15. The SLUGGS Survey: stellar masses and effective radii of early-type galaxies from Spitzer Space Telescope 3.6 μm imaging

    Science.gov (United States)

    Forbes, Duncan A.; Sinpetru, Luciana; Savorgnan, Giulia; Romanowsky, Aaron J.; Usher, Christopher; Brodie, Jean

    2017-02-01

    Galaxy starlight at 3.6 μm is an excellent tracer of stellar mass. Here we use the latest 3.6 μm imaging from the Spitzer Space Telescope to measure the total stellar mass and effective radii in a homogeneous way for a sample of galaxies from the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey. These galaxies are representative of nearby early-type galaxies in the stellar mass range of 10 samples of early-type galaxies. We model each galaxy in 2D and estimate its total asymptotic magnitude from a 1D curve-of-growth. Magnitudes are converted into stellar masses using a 3.6 μm mass-to-light ratio from the latest stellar population models of Röck et al., assuming a Kroupa initial mass function. We apply a ratio based on each galaxy's mean mass-weighted stellar age within one effective radius (the mass-to-light ratio is insensitive to galaxy metallicity for the generally old stellar ages and high metallicities found in massive early-type galaxies). Our 3.6 μm stellar masses agree well with masses derived from 2.2 μm data. From the 1D surface brightness profile, we fit a single Sérsic law, excluding the very central regions. We measure the effective radius, Sérsic n parameter and effective surface brightness for each galaxy. We find that galaxy sizes derived from shallow optical imaging and the 2MASS survey tend to underestimate the true size of the largest, most massive galaxies in our sample. We adopt the 3.6 μm stellar masses and effective radii for the SLUGGS survey galaxies.

  16. Investigating Dwarf Spiral Galaxies

    Science.gov (United States)

    Weerasooriya, Sachithra; Dunn, Jacqueline M.

    2017-01-01

    Several studies have proposed that dwarf elliptical / spheroidal galaxies form through the transformation of dwarf irregular galaxies. Early and late type dwarfs resemble each other in terms of their observed colors and light distributions (each can often be represented by exponential disks), providing reason to propose an evolutionary link between the two types. The existence of dwarf spirals has been largely debated. However, more and more recent studies are using the designation of dwarf spiral to describe their targets of interest. This project seeks to explore where dwarf spirals fit into the above mentioned evolutionary sequence, if at all. Optical colors will be compared between a sample of dwarf irregular, dwarf elliptical, and dwarf spiral galaxies. The dwarf irregular and dwarf elliptical samples have previously been found to overlap in both optical color and surface brightness profile shape when limiting the samples to their fainter members. A preliminary comparison including the dwarf spiral sample will be presented here, along with a comparison of available ultraviolet and near-infrared data. Initial results indicate a potential evolutionary link that merits further investigation.

  17. The Densest Galaxy

    CERN Document Server

    Strader, Jay; Forbes, Duncan; Fabbiano, Giuseppina; Romanowsky, Aaron; Brodie, Jean; Conroy, Charlie; Caldwell, Nelson; Pota, Vincenzo; Usher, Christopher; Arnold, Jacob

    2013-01-01

    We report the discovery of a remarkable ultra-compact dwarf galaxy around the massive Virgo elliptical galaxy NGC 4649 (M60), which we term M60-UCD1. With a dynamical mass of 2.0 x 10^8 M_sun but a half-light radius of only ~ 24 pc, M60-UCD1 is more massive than any ultra-compact dwarfs of comparable size, and is arguably the densest galaxy known in the local universe. It has a two-component structure well-fit by a sum of Sersic functions, with an elliptical, compact (r_h=14 pc; n ~ 3.3) inner component and a round, exponential, extended (r_h=49 pc) outer component. Chandra data reveal a variable central X-ray source with L_X ~ 10^38 erg/s that could be an active galactic nucleus associated with a massive black hole or a low-mass X-ray binary. Analysis of optical spectroscopy shows the object to be old (~> 10 Gyr) and of solar metallicity, with elevated [Mg/Fe] and strongly enhanced [N/Fe] that indicates light element self-enrichment; such self-enrichment may be generically present in dense stellar systems. T...

  18. Wide HI profile galaxies

    CERN Document Server

    Brosch, Noah; Zitrin, Adi

    2011-01-01

    We investigate the nature of objects in a complete sample of 28 galaxies selected from the first sky area fully covered by ALFALFA, being well-detected and having HI profiles wider than 550 km/s. The selection does not use brightness, morphology, or any other property derived from optical or other spectral bands. We investigate the degree of isolation, the morphology, and other properties gathered or derived from open data bases and show that some objects have wide HI profiles probably because they are disturbed or are interacting, or might be confused in the ALFALFA beam. We identify a sub-sample of 14 galaxies lacking immediate interacting neighbours and showing regular, symmetric, two-horned HI profiles that we propose as candidate high-mass disk systems (CHMDs). We measure the net-Halpha emission from the CHMDs and combine this with public multispectral data to model the global star formation (SF) properties of each galaxy. The Halpha observations show SFRs not higher than a few solar masses per year. Sim...

  19. Gaseous Galaxy Halos

    CERN Document Server

    Putman, M E; Joung, M R

    2012-01-01

    Galactic halo gas traces inflowing star formation fuel and feedback from a galaxy's disk and is therefore crucial to our understanding of galaxy evolution. In this review, we summarize the multi-wavelength observational properties and origin models of Galactic and low redshift spiral galaxy halo gas. Galactic halos contain multiphase gas flows that are dominated in mass by the ionized component and extend to large radii. The densest, coldest halo gas observed in neutral hydrogen (HI) is generally closest to the disk ( 10^5.5 K) and cold mode in simulations, with the compressed material close to the disk the coldest and densest, in agreement with observations. There is evidence in halo gas observations for radiative and mechanical feedback mechanisms, including escaping photons from the disk, supernova-driven winds, and a galactic fountain. Satellite accretion also leaves behind abundant halo gas. This satellite gas interacts with the existing halo medium, and much of this gas will become part of the diffuse h...

  20. ARCHANGEL: Galaxy Photometry System

    Science.gov (United States)

    Schombert, James

    2011-07-01

    ARCHANGEL is a Unix-based package for the surface photometry of galaxies. While oriented for large angular size systems (i.e. many pixels), its tools can be applied to any imaging data of any size. The package core contains routines to perform the following critical galaxy photometry functions: sky determinationframe cleaningellipse fittingprofile fittingtotal and isophotal magnitudes The goal of the package is to provide an automated, assembly-line type of reduction system for galaxy photometry of space-based or ground-based imaging data. The procedures outlined in the documentation are flux independent, thus, these routines can be used for non-optical data as well as typical imaging datasets. ARCHANGEL has been tested on several current OS's (RedHat Linux, Ubuntu Linux, Solaris, Mac OS X). A tarball for installation is available at the download page. The main routines are Python and FORTRAN based, therefore, a current installation of Python and a FORTRAN compiler are required. The ARCHANGEL package also contains Python hooks to the PGPLOT package, an XML processor and network tools which automatically link to data archives (i.e. NED, HST, 2MASS, etc) to download images in a non-interactive manner.