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Sample records for dwarf kinematics project

  1. The Brown Dwarf Kinematics Project (BDKP. III. Parallaxes for 70 Ultracool Dwarfs

    Science.gov (United States)

    2012-06-10

    National Science Foundation. 10 Hellman Fellow. Distances provide a direct means for calculating the luminos- ity and (if there is a reliable radius ...automatically removed. These were usually spurious sources caused by unfiltered detector artifacts or cosmic rays. The typical centroiding...to its final radius . Indeed, two of the three overluminous M dwarfs are suspected members of the TW Hydrae association. However, eight out of the ten

  2. THE BROWN DWARF KINEMATICS PROJECT (BDKP). IV. RADIAL VELOCITIES OF 85 LATE-M AND L DWARFS WITH MagE

    Energy Technology Data Exchange (ETDEWEB)

    Burgasser, Adam J. [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States); Logsdon, Sarah E. [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States); Gagné, Jonathan [Institute for Research on Exoplanets (iREx), Université de Montréal, Département de Physique, C.P. 6128 Succ. Centre-ville, Montréal, QC H3C 3J7 (Canada); Bochanski, John J. [Rider University, 2083 Lawrenceville Road, Lawrenceville, NJ 08648 (United States); Faherty, Jaqueline K. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States); West, Andrew A. [Department of Astronomy, Boston University, 725 Commonwealth Avenue Boston, MA 02215 (United States); Mamajek, Eric E. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Schmidt, Sarah J. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Cruz, Kelle L., E-mail: aburgasser@ucsd.edu [Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10034 (United States)

    2015-09-15

    Radial velocity measurements are presented for 85 late M- and L-type very low-mass stars and brown dwarfs obtained with the Magellan Echellette spectrograph. Targets primarily have distances within 20 pc of the Sun, with more distant sources selected for their unusual spectral energy distributions. We achieved precisions of 2–3 km s{sup −1}, and combined these with astrometric and spectrophotometric data to calculate UVW velocities. Most are members of the thin disk of the Galaxy, and velocity dispersions indicate a mean age of 5.2 ± 0.2 Gyr for sources within 20 pc. We find signficantly different kinematic ages between late-M dwarfs (4.0 ± 0.2 Gyr) and L dwarfs (6.5 ± 0.4 Gyr) in our sample that are contrary to predictions from prior simulations. This difference appears to be driven by a dispersed population of unusually blue L dwarfs which may be more prevalent in our local volume-limited sample than in deeper magnitude-limited surveys. The L dwarfs exhibit an asymmetric U velocity distribution with a net inward flow, similar to gradients recently detected in local stellar samples. Simulations incorporating brown dwarf evolution and Galactic orbital dynamics are unable to reproduce the velocity asymmetry, suggesting non-axisymmetric perturbations or two distinct L dwarf populations. We also find the L dwarfs to have a kinematic age-activity correlation similar to more massive stars. We identify several sources with low surface gravities, and two new substellar candidate members of nearby young moving groups: the astrometric binary DENIS J08230313–4912012AB, a low-probability member of the β Pictoris Moving Group; and 2MASS J15104786–2818174, a moderate-probability member of the 30–50 Myr Argus Association.

  3. The Brown Dwarf Kinematics Project (BDKP). IV. Radial Velocities of 85 Late-M and L dwarfs with MagE

    CERN Document Server

    Burgasser, Adam J; Gagne, Jonathan; Bochanski, John J; Faherty, Jaqueline K; West, Andrew A; Mamajek, Eric E; Schmidt, Sarah J; Cruz, Kelle L

    2015-01-01

    Radial velocity measurements are presented for 85 late M- and L-type very low mass stars and brown dwarfs obtained with the Magellan Echellette (MagE) spectrograph. Targets primarily have distances within 20 pc of the Sun, with more distant sources selected for their unusual spectral energy distributions. We achieved precisions of 2--3 km/s, and combined these with astrometric and spectrophotometric data to calculate $UVW$ velocities. Most are members of the thin disk of the Galaxy, and velocity dispersions indicate a mean age of 5.2$\\pm$0.2 Gyr for sources within 20 pc. We find significantly different kinematic ages between late-M dwarfs (4.0$\\pm$0.2 Gyr) and L dwarfs (6.5$\\pm$0.4 Gyr) in our sample that are contrary to predictions from prior simulations. This difference appears to be driven by a dispersed population of unusually blue L dwarfs which may be more prevalent in our local volume-limited sample than in deeper magnitude-limited surveys. The L dwarfs exhibit an asymmetric $U$ velocity distribution w...

  4. Global HI Kinematics in Dwarf Galaxies

    CERN Document Server

    Stilp, Adrienne M; Warren, Steven R; Skillman, Evan; Ott, Juergen; Koribalski, Baerbel

    2013-01-01

    HI line widths are typically interpreted as a measure of ISM turbulence, which is potentially driven by star formation. In an effort to better understand the possible connections between line widths and star formation, we have characterized \\hi{} kinematics in a sample of nearby dwarf galaxies by co-adding line-of-sight spectra after removing the rotational velocity to produce an average, global \\hi{} line profile. These "superprofiles" are composed of a central narrow peak (~6-10 km/s) with higher-velocity wings to either side that contain ~10-15% of the total flux. The superprofiles are all very similar, indicating a universal global HI profile for dwarf galaxies. We compare characteristics of the superprofiles to various galaxy properties, such as mass and measures of star formation (SF), with the assumption that the superprofile represents a turbulent peak with energetic wings to either side. We use these quantities to derive average scale heights for the sample galaxies. When comparing to physical proper...

  5. GLOBAL H I KINEMATICS IN DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Stilp, Adrienne M.; Dalcanton, Julianne J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Warren, Steven R.; Skillman, Evan [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States); Ott, Juergen [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801 (United States); Koribalski, Baerbel [Australia Telescope National Facility, CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia)

    2013-03-10

    H I line widths are typically interpreted as a measure of interstellar medium turbulence, which is potentially driven by star formation (SF). In an effort to better understand the possible connections between line widths and SF, we have characterized H I kinematics in a sample of nearby dwarf galaxies by co-adding line-of-sight spectra after removing the rotational velocity to produce average global H I line profiles. These ''superprofiles'' are composed of a central narrow peak ({approx}6-10 km s{sup -1}) with higher-velocity wings to either side that contain {approx}10%-15% of the total flux. The superprofiles are all very similar, indicating a universal global H I profile for dwarf galaxies. We compare characteristics of the superprofiles to various galaxy properties, such as mass and measures of SF, with the assumption that the superprofile represents a turbulent peak with energetic wings to either side. We use these quantities to derive average scale heights for the sample galaxies. When comparing to physical properties, we find that the velocity dispersion of the central peak is correlated with ({Sigma}{sub HI}). The fraction of mass and characteristic velocity of the high-velocity wings are correlated with measures of SF, consistent with the picture that SF drives surrounding H I to higher velocities. While gravitational instabilities provide too little energy, the SF in the sample galaxies does provide enough energy through supernovae, with realistic estimates of the coupling efficiency, to produce the observed superprofiles.

  6. STELLAR KINEMATICS AND STRUCTURAL PROPERTIES OF VIRGO CLUSTER DWARF EARLY-TYPE GALAXIES FROM THE SMAKCED PROJECT. III. ANGULAR MOMENTUM AND CONSTRAINTS ON FORMATION SCENARIOS

    Energy Technology Data Exchange (ETDEWEB)

    Toloba, E.; Guhathakurta, P. [UCO/Lick Observatory, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Boselli, A.; Boissier, S. [Aix Marseille Universit, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Peletier, R. F. [Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen (Netherlands); Emsellem, E. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Lisker, T. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg (Germany); Van de Ven, G. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Simon, J. D.; Adams, J. J.; Benson, A. J. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Falcón-Barroso, J.; Ryś, A. [Instituto de Astrofísica de Canarias, Vía Láctea s/n, E-38200 La Laguna, Tenerife (Spain); Den Brok, M. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Gorgas, J. [Departamento de Astrofísica y Ciencias de la Atmósfera, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Hensler, G. [Department of Astrophysics, University of Vienna, Türkenschanzstraße 17, A-1180 Vienna (Austria); Janz, J. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Laurikainen, E.; Salo, H. [Division of Astronomy, Department of Physics, University of Oulu, P.O. Box 3000, FI-90014 Oulu (Finland); Paudel, S., E-mail: toloba@ucolick.org [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)

    2015-02-01

    We analyze the stellar kinematics of 39 dwarf early-type galaxies (dEs) in the Virgo Cluster. Based on the specific stellar angular momentum λ{sub Re} and the ellipticity, we find 11 slow rotators and 28 fast rotators. The fast rotators in the outer parts of the Virgo Cluster rotate significantly faster than fast rotators in the inner parts of the cluster. Moreover, 10 out of the 11 slow rotators are located in the inner 3° (D < 1 Mpc) of the cluster. The fast rotators contain subtle disk-like structures that are visible in high-pass filtered optical images, while the slow rotators do not exhibit these structures. In addition, two of the dEs have kinematically decoupled cores and four more have emission partially filling in the Balmer absorption lines. These properties suggest that Virgo Cluster dEs may have originated from late-type star-forming galaxies that were transformed by the environment after their infall into the cluster. The correlation between λ{sub Re} and the clustercentric distance can be explained by a scenario where low luminosity star-forming galaxies fall into the cluster, their gas is rapidly removed by ram-pressure stripping, although some of it can be retained in their core, their star formation is quenched but their stellar kinematics are preserved. After a long time in the cluster and several passes through its center, the galaxies are heated up and transformed into slow rotating dEs.

  7. Activity and Kinematics of White Dwarf-M Dwarf Binaries from the SUPERBLINK Proper Motion Survey

    Science.gov (United States)

    Skinner, Julie N.; Morgan, Dylan P.; West, Andrew A.; Lépine, Sébastien; Thorstensen, John R.

    2017-09-01

    We present an activity and kinematic analysis of high proper motion white dwarf-M dwarf binaries (WD+dMs) found in the SUPERBLINK survey, 178 of which are new identifications. To identify WD+dMs, we developed a UV–optical–IR color criterion and conducted a spectroscopic survey to confirm each candidate binary. For the newly identified systems, we fit the two components using model white dwarf spectra and M dwarf template spectra to determine physical parameters. We use Hα chromospheric emission to examine the magnetic activity of the M dwarf in each system, and investigate how its activity is affected by the presence of a white dwarf companion. We find that the fraction of WD+dM binaries with active M dwarfs is significantly higher than their single M dwarf counterparts at early and mid-spectral types. We corroborate previous studies that find high activity fractions at both close and intermediate separations. At more distant separations, the binary fraction appears to approach the activity fraction for single M dwarfs. Using derived radial velocities and the proper motions, we calculate 3D space velocities for the WD+dMs in SUPERBLINK. For the entire SUPERBLINK WD+dMs, we find a large vertical velocity dispersion, indicating a dynamically hotter population compared to high proper motion samples of single M dwarfs. We compare the kinematics for systems with active M dwarfs and those with inactive M dwarfs, and find signatures of asymmetric drift in the inactive sample, indicating that they are drawn from an older population. Based on observations obtained at the MDM Observatory operated by Dartmouth College, Columbia University, The Ohio State University, and the University of Michigan.

  8. Structure and Kinematics of the Nearby Dwarf Galaxy UGCA 105

    CERN Document Server

    Schmidt, Philip; Gentile, Gianfranco; Oh, Se-Heon; Schuberth, Ylva; Bekhti, Nadya Ben; Winkel, Benjamin; Klein, Uli

    2013-01-01

    Owing to their shallow stellar potential, dwarf galaxies possess thick gas disks, which makes them good candidates for studies of the galactic vertical kinematical structure. We present 21 cm line observations of the isolated nearby dwarf irregular galaxy UGCA 105, taken with the Westerbork Synthesis Radio Telescope (WSRT), and analyse the geometry of its neutral hydrogen (HI) disk and its kinematics. The galaxy shows a fragmented HI distribution. It is more extended than the optical disk, and hence allows one to determine its kinematics out to very large galacto-centric distances. The HI kinematics and morphology are well-ordered and symmetric for an irregular galaxy. The HI is sufficiently extended to observe a substantial amount of differential rotation. Moreover, UGCA 105 shows strong signatures for the presence of a kinematically anomalous gas component. Performing tilted-ring modelling by use of the least-squares fitting routine TiRiFiC, we found that the HI disk of UGCA 105 has a moderately warped and ...

  9. STELLAR KINEMATICS AND STRUCTURAL PROPERTIES OF VIRGO CLUSTER DWARF EARLY-TYPE GALAXIES FROM THE SMAKCED PROJECT. II. THE SURVEY AND A SYSTEMATIC ANALYSIS OF KINEMATIC ANOMALIES AND ASYMMETRIES

    Energy Technology Data Exchange (ETDEWEB)

    Toloba, E.; Guhathakurta, P. [UCO/Lick Observatory, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Peletier, R. F. [Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen (Netherlands); Boselli, A. [Laboratoire d' Astrophysique de Marseille-LAM, Université d' Aix-Marseille and CNRS, UMR 7326, 38 rue F. Joliot-Curie, 13388 Marseille Cedex 13 (France); Lisker, T. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg (Germany); Falcón-Barroso, J.; Ryś, A. [Instituto de Astrofísica de Canarias, Vía Láctea s/n, La Laguna, Tenerife (Spain); Simon, J. D. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Van de Ven, G. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Paudel, S. [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Emsellem, E. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748, Garching (Germany); Janz, J. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Den Brok, M. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Gorgas, J. [Departamento de Astrofísica y Física de la Atmósfera, Universidad Complutense de Madrid, E-28040, Madrid (Spain); Hensler, G. [Department of Astrophysics, University of Vienna, Türkenschanzstraße 17, 1180 Vienna (Austria); Laurikainen, E.; Salo, H. [Division of Astronomy, Department of Physics, PO Box 3000, FI-90014 University of Oulu (Finland); Niemi, S.-M., E-mail: toloba@ucolick.org [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)

    2015-01-01

    We present spatially resolved kinematics and global stellar populations and mass-to-light ratios for a sample of 39 dwarf early-type (dE) galaxies in the Virgo cluster studied as part of the SMAKCED stellar absorption-line spectroscopy and imaging survey. This sample is representative of the early-type population in the Virgo cluster in the absolute magnitude range –19.0 < M{sub r} < –16.0 and of all morphological subclasses found in this galaxy population. For each dE, we measure the rotation curve and velocity dispersion profile and fit an analytic function to the rotation curve. We study the significance of the departure of the rotation curve from the best-fit analytic function (poorly fit) and of the difference between the approaching and receding sides of the rotation curve (asymmetry). Our sample includes two dEs with kinematically decoupled cores that have been previously reported. We find that 62 ± 8% (23 out of the 39) of the dEs have a significant anomaly in their rotation curve. Analysis of the images reveals photometric anomalies for most galaxies. However, there is no clear correlation between the significance of the photometric and kinematic anomalies. We measure age-sensitive (H{sub β} and H{sub γA}) and metallicity sensitive (Fe4668 and Mgb) Lick spectral indices in the LIS-5 Å system. This population of galaxies exhibits a wide range of ages and metallicities; we also find that 4 dEs show clear evidence of emission partially filling in the Balmer absorption lines. Finally, we estimate the total masses and dark matter fractions of the dEs and plot them in the mass-size, the mass-velocity dispersion, and the fundamental plane scaling relations. The dEs seem to be the bridge between massive early-type galaxies and dSphs, and have a median total mass within the R{sub e} of log M{sub e} = 9.1 ± 0.2 and a median dark matter fraction within the R{sub e} of f {sub DM} = 46 ± 18%. Any formation model for the dE galaxy class must account for this

  10. Kinematic sub-populations in dwarf spheroidal galaxies

    CERN Document Server

    Ural, Ugur; Koch, Andreas; Gilmore, Gerard; Beers, Timothy C; Belokurov, Vasily; Evans, N Wyn; Grebel, Eva K; Vidrih, Simon; Zucker, Daniel B

    2008-01-01

    We present new spectroscopic data for twenty six stars in the recently-discovered Canes Venatici I (CVnI) dwarf spheroidal galaxy. We use these data to investigate the recent claim of the presence of two dynamically inconsistent stellar populations in this system (Ibata et al., 2006). We do not find evidence for kinematically distinct populations in our sample and we are able to obtain a mass estimate for CVnI that is consistent with all available data, including previously published data. We discuss possible differences between our sample and the earlier data set and study the general detectability of sub-populations in small kinematic samples. We conclude that in the absence of supporting observational evidence (for example, metallicity gradients), sub-populations in small kinematic samples (typically fewer than 100 stars) should be treated with extreme caution, as their detection depends on multiple parameters and rarely produces a signal at the 3sigma confidence level. It is therefore essential to determi...

  11. Kinematics of nearby K-M dwarfs: first results .

    Science.gov (United States)

    Upgren, A. R.; Boyle, R. P.; Sperauskas, J.; Bartašiūtė, S.

    The lists of stars selected spectroscopically by Vyssotsky at the McCormick Observatory and the 4th version of the Catalogue of Nearby Stars (CNS4) are two major sources of nearby K-M dwarfs, which complement each other and provide a kinematically unbiased sample of about 1400 such stars. With the addition of Hipparcos and Tycho astrometry, this stellar sample offers perhaps best insight on the kinematical properties of the lower main sequence stars in the immediate solar neighborhood. Until recently, however, the main limitation in observational data for this sample was the lack of well determined radial velocities, especially for fainter magnitude stars. Therefore our first goal was to perform radial velocity observations for one-third of the sample stars which had no accurate or any radial velocity data. Using the CORAVEL spectrometer of Vilnius University Observatory, attached to the 1.5-m NASA and 1.6-m Kuiper telescopes at Steward Observatory, US, and the 1.6-m telescope at Molėtai Observatory, Lithuania, radial velocities have been recently measured for 475 K-M dwarfs. These observations, together with previous radial-velocity data and available astrometry, are used to derive complete kinematical information on the sample stars. Preliminary analysis shows the presence of different age populations which dominate in different regions of the asymmetric drift: from the young disk component, showing no lag behind the rotational motion of the Sun, to the thick disk stars which make up an extended asymmetric tail. Assuming that the U and W velocity components have zero motion relative to the LSR, and that the asymmetric drift is proportional to sigma 2_U, we find the peculiar motion of the Sun relative to the LSR (U_⊙, V_⊙, W_⊙)= (9.3± 1.3, 5.9± 0.8, 6.9±0.7) km s-1. No attempt was made at this stage of work to determine V_⊙ directly from the mean V-motion of the young disk stars. After completion of the radial-velocity program, the next step will be to

  12. Formation and evolution of dwarf early-type galaxies in the Virgo cluster I. Internal kinematics

    NARCIS (Netherlands)

    Toloba, E.; Boselli, A.; Cenarro, A. J.; Peletier, R. F.; Gorgas, J.; Gil de Paz, A.; Munoz-Mateos, J. C.

    We present new medium resolution kinematic data for a sample of 21 dwarf early-type galaxies (dEs) mainly in the Virgo cluster, obtained with the WHT and INT telescopes at the Roque de los Muchachos Observatory (La Palma, Spain). These data are used to study the origin of the dwarf elliptical galaxy

  13. Formation and evolution of dwarf early-type galaxies in the Virgo cluster I. Internal kinematics

    NARCIS (Netherlands)

    Toloba, E.; Boselli, A.; Cenarro, A. J.; Peletier, R. F.; Gorgas, J.; Gil de Paz, A.; Munoz-Mateos, J. C.

    2011-01-01

    We present new medium resolution kinematic data for a sample of 21 dwarf early-type galaxies (dEs) mainly in the Virgo cluster, obtained with the WHT and INT telescopes at the Roque de los Muchachos Observatory (La Palma, Spain). These data are used to study the origin of the dwarf elliptical galaxy

  14. Kinematics and chemistry of faint high latitude dwarf carbon stars

    Science.gov (United States)

    Yoon, Jinmi; Beers, Timothy C.; Dietz, Sarah; Lee, Young Sun; Placco, Vinicius M.

    2017-01-01

    The diffuse halo system of the Milky Way is complex, and has been shown to comprise at least two main components: a near-zero net rotation inner-halo and a more rapidly rotating outer-halo component. Studies of the ancient, very metal-poor stars in the Galactic halo system are crucial for understanding its early formation history. The so-called carbon-enhanced metal-poor (CEMP) stars are an important subset of the stars in the halo system, which exhibit distinctive kinematic and chemical signatures that can be used to constrain the star-formation histories and assembly of the various Galactic components.We have examined the sample of main-sequence dwarf and other faint high Galactic latitude carbon-enhanced stars from the Sloan Digital Sky Survey studied by Green (2013). As noted by Green, many of these starsexhibit high proper motions, which have been later claimed to be related to possible binary ejection models Plant et al. (2016). By use of the CEMP sub-classification approach of Yoon et al. (2016), we investigate whether the kinematics of these stars might instead result from their membership in the inner/outer halo populations of the Galaxy.ReferencesGreen, P. 2013, ApJ, 765, 12Plant, K. et al. 2016, AAS 227.34115Yoon, J. et al. 2016, ApJ, in pressAcknowledgementThis work was supported in part by the National Science Foundation under Grant No. PHY-1430152 (JINA Center for the Evolution of the Elements).

  15. Kinematics of the Galactic disk from LAMOST Dwarf sample

    CERN Document Server

    Jing, Yingjie; Gu, Jiayin; Jia, Yunpeng; Peng, Xiyan; Chen, Yuqin; Wu, Zhenyu; Ma, Jun; Zhou, Xu; Cao, Zihuang; Hou, Yonghui; Wang, Yuefei; Zhang, Yong

    2016-01-01

    Based on the LAMOST survey and Sloan Digital Sky Survey (SDSS), we use low-resolution spectra of 130,043 F/G-type dwarf stars to study the kinematics and metallicity properties of the Galactic disk. Our study shows that the stars with poorer metallicity and larger vertical distance from Galactic plane tend to have larger eccentricity and velocity dispersion. After separating the sample stars into likely thin-disk and thick-disk sub-sample, we find that there exits a negative gradient of rotation velocity $V_{\\phi}$ with metallicity [Fe/H] for the likely thin-disk sub-sample, and the thick-disk sub-sample exhibit a larger positive gradient of rotation velocity with metallicity. By comparing with model prediction, we consider the radial migration of stars appears to have influenced on the thin-disk formation. In addition, our results shows that the observed thick-disk stellar orbital eccentricity distribution peaks at low eccentricity ($e \\sim 0.2$) and extends to a high eccentricity ($e \\sim 0.8$). We compare ...

  16. Kinematics of dwarf galaxies in gas-rich groups, and the survival and detectability of tidal dwarf galaxies

    CERN Document Server

    Sweet, Sarah M; Meurer, Gerhardt; Kilborn, Virginia; Audcent-Ross, Fiona; Baumgardt, Holger; Bekki, Kenji

    2015-01-01

    We present DEIMOS multi-object spectroscopy (MOS) of 22 star-forming dwarf galaxies located in four gas-rich groups, including six newly-discovered dwarfs. Two of the galaxies are strong tidal dwarf galaxy (TDG) candidates based on our luminosity-metallicity relation definition. We model the rotation curves of these galaxies. Our sample shows low mass-to-light ratios (M/L=0.73$\\pm0.39M_\\odot/L_\\odot$) as expected for young, star-forming dwarfs. One of the galaxies in our sample has an apparently strongly-falling rotation curve, reaching zero rotational velocity outside the turnover radius of $r_{turn}=1.2r_e$. This may be 1) a polar ring galaxy, with a tilted bar within a face-on disk; 2) a kinematic warp. These scenarios are indistinguishable with our current data due to limitations of slit alignment inherent to MOS-mode observations. We consider whether TDGs can be detected based on their tidal radius, beyond which tidal stripping removes kinematic tracers such as H$\\alpha$ emission. When the tidal radius i...

  17. The kinematic properties of dwarf early-type galaxies in the Virgo cluster

    NARCIS (Netherlands)

    Toloba, E.; Boselli, A.; Peletier, R. F.; Gorgas, J.; Zapatero Osorio, M.R.; Gorgas, J.; Maíz Apellániz, J.; Pardo, J.R.; Gil de Paz, A.

    2011-01-01

    We present new medium resolution kinematic data for a sample of 21 dwarf early-type galaxies (dEs) mainly in the Virgo cluster. These data are used to study the origin of dEs inhabiting clusters. Within them we detect two populations: half of the sample (52%) are rotationally supported and the other

  18. On the origin of bursts in blue compact dwarf galaxies: clues from kinematics and stellar populations

    CERN Document Server

    Koleva, M; Zeilinger, W W; Verbeke, R; Schroyen, J; Vermeylen, L

    2014-01-01

    Blue compact dwarf galaxies (BCDs) form stars at, for their sizes, extraordinarily high rates. In this paper, we study what triggers this starburst and what is the fate of the galaxy once its gas fuel is exhausted. We select four BCDs with smooth outer regions, indicating them as possible progenitors of dwarf elliptical galaxies. We have obtained photometric and spectroscopic data with the FORS and ISAAC instruments on the VLT. We analyse their infra-red spectra using a full spectrum fitting technique which yields the kinematics of their stars and ionized gas together with their stellar population characteristics. We find that the_stellar_ velocity to velocity dispersion ratio (v/sigma) of our BCDs is of the order of 1.5, similar to that of dwarf elliptical galaxies. Thus, those objects do not require significant (if any) loss of angular momentum to fade into early type dwarfs. This finding is in discordance with previous studies, which however compared the stellar kinematics of dwarf elliptical galaxies with...

  19. Open Science Project in White Dwarf Research

    Science.gov (United States)

    Vornanen, T.

    2013-01-01

    I will propose a new way of advancing white dwarf research. Open science is a method of doing research that lets everyone who has something to say about the subject take part in the problem solving process. Already now, the amount of information we gather from observations, theory and modeling is too vast for any one individual to comprehend and turn into knowledge. And the amount of information just keeps growing in the future. A platform that promotes sharing of thoughts and ideas allows us to pool our collective knowledge of white dwarfs and get a clear picture of our research field. It will also make it possible for researchers in fields closely related to ours (AGB stars, planetary nebulae etc.) to join the scientific discourse. In the first stage this project would allow us to summarize what we know and what we don't, and what we should search for next. Later, it could grow into a large collaboration that would have the impact to, for example, suggest instrument requirements for future telescopes to satisfy the needs of the white dwarf community, or propose large surveys. A simple implementation would be a wiki page for collecting knowledge combined with a forum for more extensive discussions. These would be simple and cheap to maintain. A large community effort on the whole would be needed for the project to succeed, but individual workload should stay at a low level.

  20. The influence of binary stars on dwarf spheroidal galaxy kinematics

    CERN Document Server

    Hargreaves, J C; Annan, J D

    1995-01-01

    We have completed a Monte-Carlo simulation to estimate the effect of binary star orbits on the measured velocity dispersion in dwarf spheroidal galaxies. This paper analyses previous attempts at this calculation, and explains the simulations which were performed with mass, period and ellipticity distributions similar to that measured for the solar neighbourhood. The conclusion is that with functions such as these, the contribution of binary stars to the velocity dispersion is small. The distributions are consistent with the percentage of binaries detected by observations, although this is quite dependent on the measuring errors and on the number of years over which measurements have been taken. For binaries to be making a significant contribution to the dispersion measured in dSph galaxies, the distributions of the orbital parameters would need to be very different from those of stars in the solar neighbourhood. In particular more smaller period orbits with higher mass secondaries would be required. The shape...

  1. Testing core creation in hydrodynamical simulations using the HI kinematics of field dwarfs

    CERN Document Server

    Papastergis, Emmanouil

    2016-01-01

    The majority of recent hydrodynamical simulations indicate the creation of central "cores" in the mass profiles of low-mass halos, a process that is attributed to star formation-related baryonic feedback. Core creation is regarded as one of the most promising solutions to potential issues faced by LambdaCDM cosmology on small scales. For example, the reduced dynamical mass enclosed by cores can explain the low rotational velocities measured for nearby dwarf galaxies, thus possibly lifting the seeming contradiction with the LambdaCDM expectations (the so-called "too big to fail" problem). Here we test core creation as a solution of cosmological issues by using a sample of dwarfs with measurements of their atomic hydrogen (HI) kinematics extending to large radii. Using the NIHAO hydrodynamical simulation as an example, we show that core creation can successfully reproduce the kinematics of dwarfs with small kinematic radii, R <~ 1.5 kpc. However, the agreement with observations becomes poor once galaxies wit...

  2. Open Science Project in White Dwarf Research

    CERN Document Server

    Vornanen, Tommi

    2012-01-01

    I will propose a new way of advancing white dwarf research. Open science is a method of doing research that lets everyone who has something to say about the subject take part in the problem solving process. Already now, the amount of information we gather from observations, theory and modelling is too vast for any one individual to comprehend and turn into knowledge. And the amount of information just keeps growing in the future. A platform that promotes sharing of thoughts and ideas allows us to pool our collective knowledge of white dwarfs and get a clear picture of our research field. It will also make it possible for researchers in fields closely related to ours (AGB stars, planetary nebulae etc.) to join the scientific discourse. In the first stage this project would allow us to summarize what we know and what we don't, and what we should search for next. Later, it could grow into a large collaboration that would have the impact to, for example, suggest instrument requirements for future telescopes to sa...

  3. Dwarf Galaxy Dark Matter Density Profiles Inferred from Stellar and Gas Kinematics

    CERN Document Server

    Adams, Joshua J; Fabricius, Maximilian H; Bosch, Remco C E van den; Barentine, John C; Bender, Ralf; Gebhardt, Karl; Hill, Gary J; Murphy, Jeremy D; Swaters, R A; Thomas, Jens; van de Ven, Glenn

    2014-01-01

    We present new constraints on the density profiles of dark matter (DM) halos in seven nearby dwarf galaxies from measurements of their integrated stellar light and gas kinematics. The gas kinematics of low mass galaxies frequently suggest that they contain constant density DM cores, while N-body simulations instead predict a cuspy profile. We present a data set of high resolution integral field spectroscopy on seven galaxies and measure the stellar and gas kinematics simultaneously. Using Jeans modeling on our full sample, we examine whether gas kinematics in general produce shallower density profiles than are derived from the stars. Although 2/7 galaxies show some localized differences in their rotation curves between the two tracers, estimates of the central logarithmic slope of the DM density profile, gamma, are generally robust. The mean and standard deviation of the logarithmic slope for the population are gamma=0.67+/-0.10 when measured in the stars and gamma=0.58+/-0.24 when measured in the gas. We als...

  4. Formation and evolution of dwarf early-type galaxies in the Virgo cluster I. Internal kinematics

    CERN Document Server

    Toloba, E; Cenarro, A J; Peletier, R F; Gorgas, J; de Paz, A Gil; Munoz-Mateos, J C

    2010-01-01

    We present new medium resolution kinematic data for a sample of 21 dwarf early-type galaxies (dEs) mainly in the Virgo cluster, obtained with the WHT and INT telescopes at the Roque de los Muchachos Observatory (La Palma, Spain). These data are used to study the origin of the dwarf elliptical galaxy population inhabiting clusters. We confirm that dEs are not dark matter dominated galaxies, at least up to the half-light radius. We also find that the observed galaxies in the outer parts of the cluster are mostly rotationally supported systems with disky morphological shapes. Rotationally supported dEs have rotation curves similar to those of star forming galaxies of similar luminosity and follow the Tully-Fisher relation. This is expected if dE galaxies are the descendant of low luminosity star forming systems which recently entered the cluster environment and lost their gas due to a ram pressure stripping event, quenching their star formation activity and transforming into quiescent systems, but conserving the...

  5. The white dwarfs within 25 pc of the Sun: Kinematics and spectroscopic subtypes

    Energy Technology Data Exchange (ETDEWEB)

    Sion, Edward M.; McCook, George P.; Wasatonic, Richard; Myszka, Janine [Department of Astronomy and Astrophysics, Villanova University, Villanova, PA 19085 (United States); Holberg, J. B. [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 75201 (United States); Oswalt, Terry D., E-mail: edward.sion@villanova.edu, E-mail: george.mccook@villanova.edu, E-mail: richard.wasatonic@villanova.edu, E-mail: janine.myszka@villanova.edu, E-mail: holberg@vega.lpl.arizona.edu, E-mail: toswalt@fit.edu [Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL 19085 (United States)

    2014-06-01

    We present the fractional distribution of spectroscopic subtypes, range and distribution of surface temperatures, and kinematical properties of the white dwarfs (WDs) within 25 pc of the Sun. There is no convincing evidence of halo WDs in the total 25 pc sample of 224 WDs. There is also little to suggest the presence of genuine thick disk subcomponent members within 25 pc. It appears that the entire 25 pc sample likely belongs to the thin disk. We also find no significant kinematic differences with respect to spectroscopic subtypes. The total DA to non-DA ratio of the 25 pc sample is 1.8, a manifestation of deepening envelope convection, which transforms DA stars with sufficiently thin H surface layers into non-DAs. We compare this ratio with the results of other studies. We find that at least 11% of the WDs within 25 pc of the Sun (the DAZ and DZ stars) have photospheric metals that likely originate from accretion of circumstellar material (debris disks) around them. If this interpretation is correct, then it suggests the possibility that a similar percentage have planets, asteroid-like bodies, or debris disks orbiting them. Our volume-limited sample reveals a pileup of DC WDs at the well-known cutoff in DQ WDs at T {sub eff} ∼ 6000 K. Mindful of small number statistics, we speculate on its possible evolutionary significance. We find that the incidence of magnetic WDs in the 25 pc sample is at least 8% in our volume-limited sample, dominated by cool WDs. We derive approximate formation rates of DB and DQ degenerates and present a preliminary test of the evolutionary scenario that all cooling DB stars become DQ WDs via helium convective dredge-up with the diffusion tail of carbon extending upward from their cores.

  6. AN ACTIVITY–ROTATION RELATIONSHIP AND KINEMATIC ANALYSIS OF NEARBY MID-TO-LATE-TYPE M DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    West, Andrew A.; Weisenburger, Kolby L. [Department of Astronomy, Boston University, 725 Commonwealth Ave, Boston, MA 02215 (United States); Irwin, Jonathan; Charbonneau, David; Dittmann, Jason [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Berta-Thompson, Zachory K. [MIT, Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Ave., Bldg. 37, Cambridge, MA 02139 (United States); Pineda, J. Sebastian, E-mail: aawest@bu.edu [California Institute of Technology, Department of Astronomy, 1200 E. California Ave, Pasadena, CA 91125 (United States)

    2015-10-10

    Using spectroscopic observations and photometric light curves of 238 nearby M dwarfs from the MEarth exoplanet transit survey, we examine the relationships between magnetic activity (quantified by Hα emission), rotation period, and stellar age. Previous attempts to investigate the relationship between magnetic activity and rotation in these stars were hampered by the limited number of M dwarfs with measured rotation periods (and the fact that v sin i measurements probe only rapid rotation). However, the photometric data from MEarth allows us to probe a wide range of rotation periods for hundreds of M dwarf stars (from shorter than one to longer than 100 days). Over all M spectral types that we probe, we find that the presence of magnetic activity is tied to rotation, including for late-type, fully convective M dwarfs. We also find evidence that the fraction of late-type M dwarfs that are active may be higher at longer rotation periods compared to their early-type counterparts, with several active, late-type, slowly rotating stars present in our sample. Additionally, we find that all M dwarfs with rotation periods shorter than 26 days (early-type; M1–M4) and 86 days (late-type; M5–M8) are magnetically active. This potential mismatch suggests that the physical mechanisms that connect stellar rotation to chromospheric heating may be different in fully convective stars. A kinematic analysis suggests that the magnetically active, rapidly rotating stars are consistent with a kinematically young population, while slow-rotators are less active or inactive and appear to belong to an older, dynamically heated stellar population.

  7. Kinematic properties as probes of the evolution of dwarf galaxies in the Virgo cluster

    CERN Document Server

    Toloba, E; Gorgas, J; Peletier, R F; Cenarro, A J; Gadotti, D A; de Paz, A Gil; Pedraz, S; Yildiz, U

    2009-01-01

    We present new observational results on the kinematical, morphological, and stellar population properties of a sample of 21 dEs located both in the Virgo cluster and in the field, which show that 52% of the dEs i) are rotationally supported, ii) exhibit structural signs of typical rotating systems such as discs, bars or spiral arms, iii) are younger (~3 Gyr) than non-rotating dEs, and iv) are preferentially located either in the outskirts of Virgo or in the field. This evidence is consistent with the idea that rotationally supported dwarfs are late type spirals or irregulars that recently entered the cluster and lost their gas through a ram pressure stripping event, quenching their star formation and becoming dEs through passive evolution. We also find that all, but one, galaxies without photometric hints for hosting discs are pressure supported and are all situated in the inner regions of the cluster. This suggests a different evolution from the rotationally supported systems. Three different scenarios for t...

  8. Chemistry and Kinematics of the Late-forming Dwarf Irregular Galaxies Leo A, Aquarius, and Sagittarius DIG

    Science.gov (United States)

    Kirby, Evan N.; Rizzi, Luca; Held, Enrico V.; Cohen, Judith G.; Cole, Andrew A.; Manning, Ellen M.; Skillman, Evan D.; Weisz, Daniel R.

    2017-01-01

    We present Keck/DEIMOS spectroscopy of individual stars in the relatively isolated Local Group dwarf galaxies Leo A, Aquarius, and the Sagittarius dwarf irregular galaxy. The three galaxies—but especially Leo A and Aquarius—share in common delayed star formation histories (SFHs) relative to many other isolated dwarf galaxies. The stars in all three galaxies are supported by dispersion. We found no evidence of stellar velocity structure, even for Aquarius, which has rotating H i gas. The velocity dispersions indicate that all three galaxies are dark-matter-dominated, with dark-to-baryonic mass ratios ranging from {4.4}-0.8+1.0 (SagDIG) to {9.6}-1.8+2.5 (Aquarius). Leo A and SagDIG have lower stellar metallicities than Aquarius, and they also have higher gas fractions, both of which would be expected if Aquarius were further along in its chemical evolution. The metallicity distribution of Leo A is inconsistent with a closed or leaky box model of chemical evolution, suggesting that the galaxy was pre-enriched or acquired external gas during star formation. The metallicities of stars increased steadily for all three galaxies, but possibly at different rates. The [α/Fe] ratios at a given [Fe/H] are lower than that of the Sculptor dwarf spheroidal galaxy, which indicates more extended SFHs than Sculptor, consistent with photometrically derived SFHs. Overall, the bulk kinematic and chemical properties for the late-forming dwarf galaxies do not diverge significantly from those of less delayed dwarf galaxies, including dwarf spheroidal galaxies. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  9. VizieR Online Data Catalog: Kinematic analysis of M7-L8 dwarfs (Faherty+, 2016)

    Science.gov (United States)

    Faherty, J. K.; Riedel, A. R.; Cruz, K. L.; Gagne, J.; Filippazzo, J. C.; Lambrides, E.; Fica, H.; Weinberger, A.; Thorstensen, J. R.; Tinney, C. G.; Baldassare, V.; Lemonier, E.; Rice, E. L.

    2017-08-01

    The sample of 152 M7-L8 ultra-cool dwarfs comprising our sample (see table 1) were placed on follow-up programs --either imaging (parallax, proper motion), spectroscopy (radial velocity), or both-- to determine kinematic membership in a nearby moving group. For Northern Hemisphere astrometry targets, we obtained I-band images with the MDM Observatory 2.4m Hiltner telescope on Kitt Peak, Arizona. We also observed 16 of the most southern targets with the Carnegie Astrometric Planet Search Camera (CAPSCam) on the 100 inch du Pont telescope and 5 with the FourStar imaging camera on the Magellan Baade Telescope. Table 2 gives the pertinent astrometric information; Table 3 lists our measured parallaxes and proper motions. New proper-motion measurements are listed in Table 5. See also section 3.1. We used the 6.5m Baade Magellan telescope and the FIRE spectrograph to obtain near-infrared spectra of 36 sources. Observations were made over seven runs between 2013 July and 2014 September. All observations (resolution R~6000) cover the full 0.8-2.5um band with a spatial resolution of 0.18"/pixel. We used the 3m NASA IRTF to obtain low-resolution near-infrared spectroscopy for 10 targets. All of the observations were aligned to the parallactic angle to obtain R~120 spectral data over the wavelength range of 0.7-2.5um. We used the Triple Spectrograph (TSpec) at the 5m Hale Telescope at Palomar Observatory to obtain near-infrared spectra of two targets. TSpec covers simultaneously the range from 1.0 to 2.45um and achieves a resolution of ~2500. Exposure times for each source and the number of images acquired are listed in Table 6; see also section 3.2. Multiple observations of 17 sources were taken in high-resolution mode on Keck II on 2008 September 14-16, using the NIRSPEC-5 filter to obtain H-band spectra in Order 49 (1.545-1.570um ). Observations of 18 sources were taken during semesters 2007B and 2009B using the H6420 filter of the Phoenix instrument (previously on Gemini

  10. Kinematic Constraints on Evolutionary Scenarios for Blue Compact Dwarf Galaxies I. Neutral Gas Dynamics

    CERN Document Server

    Van Zee, L; Skillman, E D; Zee, Liese van; Salzer, John J.; Skillman, Evan D.

    2001-01-01

    We present the results of high spatial resolution HI synthesis observations of six blue compact dwarf (BCD) galaxies. Optically, the selected galaxies have smooth, symmetric isophotes, and thus are the most likely of the BCD class to fade into an object morphologically similar to a dwarf elliptical when the current starburst ends. The neutral gas in all six galaxies appears to be rotationally supported, however, indicating that true morphological transformation from a BCD to a dE will require significant loss of angular momentum. Based on the observed neutral gas dynamics of these and other BCDs, it is unlikely that present-day BCDs will evolve directly into dwarf ellipticals after a starburst phase. We discuss alternative evolutionary scenarios for BCDs and place them within the larger context of galaxy formation and evolution models.

  11. Chemical Abundances and Kinematics in Globular Clusters and Local Group Dwarf Galaxies and Their Implications for Formation Theories of the Galactic Halo

    CERN Document Server

    Geisler, Doug; Smith, Verne V; Casetti-Dinescu, Dana I

    2007-01-01

    We review Galactic halo formation theories and supporting evidence, in particular kinematics and detailed chemical abundances of stars in some relevant globular clusters as well as Local Group dwarf galaxies. Outer halo red HB clusters tend to have large eccentricities and inhabit the area populated by dwarf spheroidal stars, favoring an extraGalactic origin. Old globulars show the full range of eccentricities, while younger ones seem to have preferentially high eccentricities, again hinting at their extraGalactic origin. We compare detailed abundances of a variety of elements between the halo and all dwarf galaxies studied to date, including both dwarf spheroidals and irregulars. The salient feature is that halo abundances are essentially unique. In particular, the general alpha vs. [Fe/H] pattern of 12 of the 13 galaxies studied are similar to each other and very different from the Milky Way. Sagittarius appears to be the only possible exception. It appears very unlikely that a significant fraction of the m...

  12. A Gemini/GMOS study of the physical conditions and kinematics of the blue compact dwarf galaxy Mrk 996

    CERN Document Server

    Telles, Eduardo; Izotov, Yuri I; Carrasco, Eleazar Rodrigo

    2013-01-01

    We present an integral field spectroscopic study with the Gemini Multi-Object Spectrograph (GMOS) of the unusual blue compact dwarf (BCD) galaxy Mrk 996. We show through velocity and dispersion maps, emission-line intensity and ratio maps, and by a new technique of electron density limit imaging that the ionization properties of different regions in Mrk 996 are correlated with their kinematic properties. From the maps, we can spatially distinguish a very dense high-ionization zone with broad lines in the nuclear region, and a less dense low-ionization zone with narrow lines in the circumnuclear region. Four kinematically distinct systems of lines are identified in the integrated spectrum of Mrk 996, suggesting stellar wind outflows from a population of Wolf-Rayet (WR) stars in the nuclear region, superposed on an underlying rotation pattern. From the intensities of the blue and red bumps, we derive a population of $\\sim$473 late nitrogen (WNL) stars and $\\sim$98 early carbon (WCE) stars in the nucleus of Mrk ...

  13. The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood

    CERN Document Server

    Newton, Elisabeth R; Charbonneau, David; Berta-Thompson, Zachory K; Dittmann, Jason A; West, Andrew A

    2015-01-01

    Rotation is a directly-observable stellar property, and drives magnetic field generation and activity through a magnetic dynamo. Main sequence stars with masses below approximately 0.35Msun (mid-to-late M dwarfs) are fully-convective, and are expected to have a different type of dynamo mechanism than solar-type stars. Measurements of their rotation rates provide insights into these mechanisms, but few rotation periods are available for these stars at field ages. Using photometry from the MEarth transit survey, we measure rotation periods for 391 nearby, mid-to-late M dwarfs in the Northern hemisphere, finding periods from 0.1 to 150 days. The typical detected rotator has stable, sinusoidal photometric modulations at a semi-amplitude of 0.5 to 1%. We find no period-amplitude relation for stars below 0.25Msun and an anti-correlation between period and amplitude for higher-mass M dwarfs. We highlight the existence of older, slowly-rotating stars without H{\\alpha} emission that nevertheless have strong photometri...

  14. Seventy six T dwarfs from the UKIDSS LAS: benchmarks, kinematics and an updated space density

    CERN Document Server

    Burningham, Ben; Smith, L; Leggett, S K; Smart, R L; Mann, A W; Dhital, S; Lucas, P W; Tinney, C G; Pinfield, D J; Zhang, Z; Morley, C; Saumon, D; Aller, K; Littlefair, S P; Homeier, D; Lodieu, N; Deacon, N; Marley, M S; van Spaandonk, L; Baker, D; Allard, F; Andrei, A H; Canty, J; Clarke, J; Day-Jones, A C; Dupuy, T; Fortney, J J; Gomes, J; Ishii, M; Jones, H R A; Liu, M; Magazzu, A; Marocco, F; Murray, D N; Rojas-Ayala, B; Tamura, M

    2013-01-01

    We report the discovery of 76 new T dwarfs from the UKIDSS Large Area Survey (LAS). Near-infrared broad and narrow-band photometry and spectroscopy are presented for the new objects, along with WISE and warm-Spitzer photometry. Proper motions for 128 UKIDSS T dwarfs are presented from a new two epoch LAS proper motion catalogue. We use these motions to identify two new benchmark systems: LHS 6176AB, a T8+M4 pair and HD118865AB, a T5.5+F8 pair. Using age constraints from the primaries and evolutionary models to constrain the radii we have estimated their physical properties from their bolometric luminosity. We compare the colours and properties of known benchmark T dwarfs to the latest model atmospheres and draw two principal conclusions. Firstly, it appears that the H - [4.5] and J - W2 colours are more sensitive to metallicity than has previously been recognised, such that differences in metallicity may dominate over differences in Teff when considering relative properties of cool objects using these colours...

  15. THE NEXT GENERATION VIRGO CLUSTER SURVEY. VI. THE KINEMATICS OF ULTRA-COMPACT DWARFS AND GLOBULAR CLUSTERS IN M87

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hong-Xin; Peng, Eric W.; Li, Biao [Department of Astronomy, Peking University, Beijing 100871 (China); Côté, Patrick; Ferrarese, Laura; Gwyn, Stephen D. J.; Blakeslee, John P. [National Research Council of Canada, Herzberg Astronomy and Astrophysics Program, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Liu, Chengze [Center for Astronomy and Astrophysics, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Cuillandre, Jean-Charles [Canada-France-Hawaii Telescope Corporation, Kamuela, HI 96743 (United States); Caldwell, Nelson [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Jordán, Andrés; Muñoz, Roberto P.; Puzia, Thomas H. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago (Chile); Lançon, Ariane [Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l' Universite, F-67000 Strasbourg (France); Bekki, Kenji [School of Physics, University of New South Wales, Sydney 2052, NSW (Australia); Boselli, Alessandro [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Drinkwater, Michael J. [School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072 (Australia); Duc, Pierre-Alain, E-mail: hongxin@pku.edu.cn, E-mail: peng@pku.edu.cn [Laboratoire AIM Paris-Saclay, CNRS/INSU, Université Paris Diderot, CEA/IRFU/SAp, F-91191 Gif-sur-Yvette Cedex (France); and others

    2015-03-20

    The origin of ultra-compact dwarfs (UCDs; r{sub h} ≳ 10 pc)—objects larger and more massive than typical globular clusters (GCs), but more compact than typical dwarf galaxies—has been hotly debated in the 15 years since their discovery. Even whether UCDs should be considered galactic in origin, or simply the most extreme star clusters, is not yet settled. We present the dynamical properties of 97 spectroscopically confirmed UCDs and 911 GCs associated with the central cD galaxy of the Virgo cluster, M87. Our UCDs, of which 89% have M {sub *} ≳ 2× 10{sup 6} M {sub ☉} and 92% are as blue as the classic blue GCs, nearly triple the confirmed sample of Virgo UCDs, providing by far the best opportunity for studying global dynamics of a UCD system. We found that (1) UCDs have a surface number density profile that is shallower than that of blue GCs in the inner ∼70 kpc and as steep as that of red GCs at larger radii; (2) UCDs exhibit a significantly stronger rotation than GCs, and blue GCs seem to have a velocity field that is more consistent with that of the surrounding dwarf ellipticals than with that of UCDs; (3) UCDs have an orbital anisotropy profile that is tangentially biased at radii ≲40 kpc and radially biased farther out, whereas blue GCs become more tangentially biased at larger radii beyond ∼40 kpc; (4) GCs with M {sub *} ≳ 2 × 10{sup 6} M {sub ☉} have rotational properties indistinguishable from the less massive ones, suggesting that it is the size, instead of mass, that differentiates UCDs from GCs as kinematically distinct populations. We conclude that most UCDs in M87 are not consistent with being merely the most luminous and extended examples of otherwise normal GCs. The radially biased orbital structure of UCDs at large radii is in general agreement with the 'tidally threshed dwarf galaxy' scenario.

  16. Stellar Kinematics and Metallicities in the Ultra-faint Dwarf Galaxy Reticulum II

    Science.gov (United States)

    Simon, J. D.; Drlica-Wagner, A.; Li, T. S.; Nord, B.; Geha, M.; Bechtol, K.; Balbinot, E.; Buckley-Geer, E.; Lin, H.; Marshall, J.; Santiago, B.; Strigari, L.; Wang, M.; Wechsler, R. H.; Yanny, B.; Abbott, T.; Bauer, A. H.; Bernstein, G. M.; Bertin, E.; Brooks, D.; Burke, D. L.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; D'Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Dodelson, S.; Cunha, C. E.; Estrada, J.; Evrard, A. E.; Fausti Neto, A.; Fernandez, E.; Finley, D. A.; Flaugher, B.; Frieman, J.; Gaztanaga, E.; Gerdes, D.; Gruen, D.; Gruendl, R. A.; Honscheid, K.; James, D.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; March, M.; Martini, P.; Miller, C. J.; Miquel, R.; Ogando, R.; Romer, A. K.; Roodman, A.; Rykoff, E. S.; Sako, M.; Sanchez, E.; Schubnell, M.; Sevilla, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thaler, J.; Tucker, D.; Vikram, V.; Walker, A. R.; Wester, W.; DES Collaboration

    2015-07-01

    We present Magellan/M2FS, Very Large Telescope/GIRAFFE, and Gemini South/GMOS spectroscopy of the newly discovered Milky Way satellite Reticulum II. Based on the spectra of 25 Ret II member stars selected from Dark Energy Survey imaging, we measure a mean heliocentric velocity of 62.8+/- 0.5 {km} {{{s}}}-1 and a velocity dispersion of 3.3+/- 0.7 {km} {{{s}}}-1. The mass-to-light ratio of Ret II within its half-light radius is 470+/- 210 {M}⊙ /{L}⊙ , demonstrating that it is a strongly dark matter-dominated system. Despite its spatial proximity to the Magellanic Clouds, the radial velocity of Ret II differs from that of the LMC and SMC by 199 and 83 {km} {{{s}}}-1, respectively, suggesting that it is not gravitationally bound to the Magellanic system. The likely member stars of Ret II span 1.3 dex in metallicity, with a dispersion of 0.28 ± 0.09 dex, and we identify several extremely metal-poor stars with {{[Fe/H]}}\\lt -3. In combination with its luminosity, size, and ellipticity, these results confirm that Ret II is an ultra-faint dwarf galaxy. With a mean metallicity of {{[Fe/H]}}=-2.65+/- 0.07, Ret II matches Segue 1 as the most metal-poor galaxy known. Although Ret II is the third-closest dwarf galaxy to the Milky Way, the line-of-sight integral of the dark matter density squared is {{log}}10(J)=18.8+/- 0.6 {GeV}{ }2 {{cm}}-5 within 0.°2, indicating that the predicted gamma-ray flux from dark matter annihilation in Ret II is lower than that of several other dwarf galaxies. Based on data obtained from the ESO Science Archive Facility under request number 157689.

  17. The Stellar and Gas Kinematics of the LITTLE THINGS Dwarf Irregular Galaxy NGC 1569

    CERN Document Server

    Johnson, Megan; Oh, Se-Heon; Zhang, Hong-Xin; Elmegreen, Bruce; Brinks, Elias; Tollerud, Erik; Herrmann, Kimberly

    2012-01-01

    In order to understand the formation and evolution of dIm galaxies, one needs to understand their three-dimensional structure. We present measurements of the stellar velocity dispersion in NGC 1569, a nearby post-starburst dIm galaxy. The stellar vertical velocity dispersion, $\\sigma_{\\rm z}$, coupled with the maximum rotational velocity derived from \\ion{H}{1} observations, $V_{\\rm max}$, gives a measure of how kinematically hot the galaxy is, and, therefore, indicates its structure. We conclude that the stars in NGC 1569 are in a thick disk with a $V_{\\rm max} / \\sigma_{\\rm z}$ = 2.4 $\\pm$ 0.7. In addition to the structure, we analyze the ionized gas kinematics from \\ion{O}{3} observations along the morphological major axis. These data show evidence for outflow from the inner starburst region and a potential expanding shell near supermassive star cluster (SSC) A. When compared to the stellar kinematics, the velocity dispersion of the stars increase in the region of SSC A supporting the hypothesis of an expa...

  18. Virgo Cluster and field dwarf ellipticals in 3D: I. On the variety of stellar kinematic and line-strength properties

    CERN Document Server

    Ryś, Agnieszka; van de Ven, Glenn

    2012-01-01

    We present the first large-scale stellar kinematic and line-strength maps for dwarf elliptical galaxies (9 in the Virgo Cluster and 3 in the field environment) obtained with the SAURON integral-field unit. No two galaxies in our sample are alike: we see that the level of rotation is not tied to flattening (we have, e.g. round rotators and flattened nonrotators); we observe kinematic twists in 1 Virgo and 1 field object; we discover large-scale kinematically-decoupled components in 2 field galaxies; we see varying gradients in line-strength maps, from nearly flat to strongly peaked in the center. The great variety of morphological, kinematic, and stellar population parameters seen in our data points to a formation scenario in which properties are shaped stochastically. A combined effect of ram-pressure stripping and galaxy harassment is the most probable explanation. We show the need for a comprehensive analysis of kinematic, dynamical, and stellar population properties which will enable us to place dwarf elli...

  19. Life at the Periphery of the Local Group: the kinematics of the Tucana Dwarf Galaxy

    CERN Document Server

    Fraternali, F; Irwin, M; Cole, A

    2009-01-01

    Dwarf spheroidal galaxies in the Local Group are usually located close to the Milky Way or M31. Currently, there are two clear exceptions to this rule, and the Tucana dwarf galaxy is the most distant at almost 1 Mpc from the Milky Way. Using the VLT/FORS2 spectrograph in multi-object mode we were able to measure the velocities of 23 individual Red Giant Branch stars in and around Tucana using the Ca triplet absorption lines. From this sample 17 reliable members have been identified. We measured the systemic velocity and dispersion of Tucana to be v_hel = +194.0+-4.3 km/s and sigma_l.o.s. = 15.8+4.1-3.1 km/s respectively. These measures are derived after removing the signature of rotation using a linear gradient of 6.5 x R/R_core+-2.9 km/s, which corresponds to a rotation of 16 km/s at the reliable limit of our data. Our systemic velocity corresponds to a receding velocity from the barycentre of the Local Group of v_LG = +73.3 km/s. We also determined the mean metallicity of Tucana to be [Fe/H] = -1.95+-0.15 w...

  20. Kinematic Properties and Dark Matter Fraction of Virgo Dwarf Early-Type Galaxies

    CERN Document Server

    Toloba, E; Peletier, R; Gorgas, J

    2012-01-01

    What happens to dwarf galaxies as they enter the cluster potential well is one of the main unknowns in studies of galaxy evolution. Several evidence suggests that late-type galaxies enter the cluster and are transformed to dwarf early-type galaxies (dEs). We study the Virgo cluster to understand which mechanisms are involved in this transformation. We find that the dEs in the outer parts of Virgo have rotation curves with shapes and amplitudes similar to late-type galaxies of the same luminosity. These dEs are rotationally supported, have disky isophotes, and younger ages than those dEs in the center of Virgo, which are pressure supported, often have boxy isophotes and are older. Ram pressure stripping, thus, explains the properties of the dEs located in the outskirts of Virgo. However, the dEs in the central cluster regions, which have lost their angular momentum, must have suffered a more violent transformation. A combination of ram pressure stripping and harassment is not enough to remove the rotation and ...

  1. Willman 1 - a probable dwarf galaxy with an irregular kinematic distribution

    CERN Document Server

    Willman, Beth; Strader, Jay; Strigari, Louis E; Simon, Joshua D; Kirby, Evan; Warres, Alex

    2010-01-01

    We investigate the kinematic properties and stellar population of the Galactic satellite Willman 1 (Wil 1) by combining Keck/DEIMOS spectroscopy with KPNO mosaic camera imaging. Wil 1 is a nearby, ultra-low luminosity Milky Way companion. This object lies in a region of size-luminosity space (M_V ~ -2 mag, d ~ 38 kpc, r_half ~ 20 pc) also occupied by the Galactic satellites Bo\\"otes II and Segue 1 and 2, but no other known old stellar system. We use kinematic and color-magnitude criteria to identify 45 stars as possible members of Wil 1. With a systemic velocity of -12.8 +\\- 1.0 km/s, Wil 1 stars have velocities similar to those of foreground Milky Way stars. Informed by Monte-Carlo simulations, we identify 5 of the 45 candidate member stars as likely foreground contaminants, with a small number possibly remaining at faint apparent magnitudes. These contaminants could have mimicked a large velocity dispersion and an abundance spread in previous work. The significant spread in the [Fe/H] of the two brightest W...

  2. Stellar Kinematics and Metallicities in the Ultra-Faint Dwarf Galaxy Reticulum II

    CERN Document Server

    Simon, J D; Li, T S; Nord, B; Geha, M; Bechtol, K; Balbinot, E; Buckley-Geer, E; Lin, H; Marshall, J; Santiago, B; Strigari, L; Wang, M; Wechsler, R H; Yanny, B; Abbott, T; Bauer, A H; Bernstein, G M; Bertin, E; Brooks, D; Burke, D L; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Dodelson, S; Cunha, C E; Estrada, J; Evrard, A E; Neto, A Fausti; Fernandez, E; Finley, D A; Flaugher, B; Frieman, J; Gaztanaga, E; Gerdes, D; Gruen, D; Gruendl, R A; Honscheid, K; James, D; Kuehn, K; Kuropatkin, N; Lahav, O; Maia, M A G; March, M; Martini, P; Miller, C J; Miquel, R; Ogando, R; Romer, A K; Roodman, A; Rykoff, E S; Sako, M; Sanchez, E; Schubnell, M; Sevilla, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Tucker, D; Vikram, V; Walker, A R; Wester, W

    2015-01-01

    We present Magellan/M2FS, VLT/GIRAFFE, and Gemini South/GMOS spectroscopy of the newly discovered Milky Way satellite Reticulum II. Based on the spectra of 25 Ret II member stars selected from Dark Energy Survey imaging, we measure a mean heliocentric velocity of 62.8 +/- 0.5 km/s and a velocity dispersion of 3.3 +/- 0.7 km/s. The mass-to-light ratio of Ret II within its half-light radius is 470 +/- 210 Msun/Lsun, demonstrating that it is a strongly dark matter-dominated system. Despite its spatial proximity to the Magellanic Clouds, the radial velocity of Ret II differs from that of the LMC and SMC by 199 and 83 km/s, respectively, suggesting that it is not gravitationally bound to the Magellanic system. The likely member stars of Ret II span 1.3 dex in metallicity, with a dispersion of 0.28 +/- 0.09 dex, and we identify several extremely metal-poor stars with [Fe/H] < -3. In combination with its luminosity, size, and ellipticity, these results confirm that Ret II is an ultra-faint dwarf galaxy. With a me...

  3. Clean Kinematic Samples in Dwarf Spheroidals: An Algorithm for Evaluating Membership and Estimating Distribution Parameters When Contamination is Present

    CERN Document Server

    Walker, Matthew G; Olszewski, Edward W; Sen, Bodhisattva; Woodroofe, Michael

    2008-01-01

    (abridged) We develop an algorithm for estimating parameters of a distribution sampled with contamination, employing a statistical technique known as ``expectation maximization'' (EM). Given models for both member and contaminant populations, the EM algorithm iteratively evaluates the membership probability of each discrete data point, then uses those probabilities to update parameter estimates for member and contaminant distributions. The EM approach has wide applicability to the analysis of astronomical data. Here we tailor an EM algorithm to operate on spectroscopic samples obtained with the Michigan-MIKE Fiber System (MMFS) as part of our Magellan survey of stellar radial velocities in nearby dwarf spheroidal (dSph) galaxies. These samples are presented in a companion paper and contain discrete measurements of line-of-sight velocity, projected position, and Mg index for ~1000 - 2500 stars per dSph, including some fraction of contamination by foreground Milky Way stars. The EM algorithm quantifies both dSp...

  4. Contamination of stellar-kinematic samples and uncertainty about dark matter annihilation profiles in ultrafaint dwarf galaxies: the example of Segue I

    Science.gov (United States)

    Bonnivard, V.; Maurin, D.; Walker, M. G.

    2016-10-01

    The expected gamma-ray flux coming from dark matter annihilation in dwarf spheroidal (dSph) galaxies depends on the so-called J-factor, the integral of the squared dark matter density along the line of sight. We examine the degree to which estimates of J are sensitive to contamination (by foreground Milky Way stars and stellar streams) of the stellar-kinematic samples that are used to infer dark matter densities in `ultrafaint' dSphs. Applying standard kinematic analyses to hundreds of mock data sets that include varying levels of contamination, we find that misclassified contaminants can cause J-factors to be overestimated by orders of magnitude. Stellar-kinematic data sets for which we obtain such biased estimates tend (1) to include relatively large fractions of stars with ambiguous membership status, and (2) to give estimates for J that are sensitive to specific choices about how to weight and/or to exclude stars with ambiguous status. Comparing publicly available stellar-kinematic samples for the nearby dSphs Reticulum II and Segue I, we find that only the latter displays both of these characteristics. Estimates of Segue I's J-factor should therefore be regarded with a larger degree of caution when planning and interpreting gamma-ray observations. Moreover, robust interpretations regarding dark matter annihilation in dSph galaxies in general will require explicit examination of how interlopers might affect the inferred dark matter density profiles.

  5. Pedestrian kinematics: a detailed study from the aspects project

    NARCIS (Netherlands)

    Rodarius, C.; Hair-Buijssen, S.H.H.M. de; Mottola, E.; Schaub, S.

    2013-01-01

    This study aims at providing insight on pedestrian kinematics during vehicle impact for the following variables: pedestrian size, position and posture as well as vehicle related variables like shape, speed and pre-crash braking. It is part of the work conducted within work package 3 “Injury assessme

  6. A Projected Non-linear Conjugate Gradient Method for Interactive Inverse Kinematics

    DEFF Research Database (Denmark)

    Engell-Nørregård, Morten; Erleben, Kenny

    2009-01-01

    Inverse kinematics is the problem of posing an articulated figure to obtain a wanted goal, without regarding inertia and forces. Joint limits are modeled as bounds on individual degrees of freedom, leading to a box-constrained optimization problem. We present A projected Non-linear Conjugate...... Gradient optimization method suitable for box-constrained optimization problems for inverse kinematics. We show application on inverse kinematics positioning of a human figure. Performance is measured and compared to a traditional Jacobian Transpose method. Visual quality of the developed method...

  7. The First Brown Dwarf Discovered by the Backyard Worlds: Planet 9 Citizen Science Project

    Science.gov (United States)

    Kuchner, Marc J.; Faherty, Jacqueline K.; Schneider, Adam C.; Meisner, Aaron M.; Filippazzo, Joseph C.; Gagne, Jonathan; Trouille, Laura; Silverberg, Steven M.; Castro, Rosa; Fletcher, Bob; hide

    2017-01-01

    The Wide-field Infrared Survey Explorer (WISE) is a powerful tool for finding nearby brown dwarfs and searching for new planets in the outer solar system, especially with the incorporation of NEOWISE and NEOWISE Reactivation data. However, so far, searches for brown dwarfs in WISE data have yet to take advantage of the full depth of the WISE images. To efficiently search this unexplored space via visual inspection, we have launched anew citizen science project, called "Backyard Worlds: Planet 9," which asks volunteers to examine short animations composed of difference images constructed from time-resolved WISE co adds. We report the first new substellar object discovered by this project, WISEA J110125.95+540052.8, a T5.5 brown dwarf located approximately 34 pc from the Sun with a total proper motion of approx.0. "7/ yr. WISEA J110125.95+540052.8 has a WISE W2 magnitude of W2 = 15.37+/- 0.09; our sensitivity to this source demonstrates the ability of citizen scientists to identify moving objects via visual inspection that are 0.9 mag fainter than the W2 single-exposure sensitivity, a threshold that has limited prior motion-based brown dwarf searches with WISE.

  8. The First Brown Dwarf Discovered by the Backyard Worlds: Planet 9 Citizen Science Project

    Science.gov (United States)

    Kuchner, Marc J.; Faherty, Jacqueline K.; Schneider, Adam C.; Meisner, Aaron M.; Filippazzo, Joseph C.; Gagné, Jonathan; Trouille, Laura; Silverberg, Steven M.; Castro, Rosa; Fletcher, Bob; Mokaev, Khasan; Stajic, Tamara

    2017-06-01

    The Wide-field Infrared Survey Explorer (WISE) is a powerful tool for finding nearby brown dwarfs and searching for new planets in the outer solar system, especially with the incorporation of NEOWISE and NEOWISE-Reactivation data. However, so far, searches for brown dwarfs in WISE data have yet to take advantage of the full depth of the WISE images. To efficiently search this unexplored space via visual inspection, we have launched a new citizen science project, called “Backyard Worlds: Planet 9,” which asks volunteers to examine short animations composed of difference images constructed from time-resolved WISE coadds. We report the first new substellar object discovered by this project, WISEA J110125.95+540052.8, a T5.5 brown dwarf located approximately 34 pc from the Sun with a total proper motion of ˜0.″7 {{yr}}-1. WISEA J110125.95+540052.8 has a WISE W2 magnitude of W2=15.37+/- 0.09; our sensitivity to this source demonstrates the ability of citizen scientists to identify moving objects via visual inspection that are 0.9 mag fainter than the W2 single-exposure sensitivity, a threshold that has limited prior motion-based brown dwarf searches with WISE.

  9. An Activity-Rotation Relationship and Kinematic Analysis of Nearby Mid-to-Late-type M Dwarfs

    CERN Document Server

    West, Andrew A; Irwin, Jonathan; Berta-Thompson, Zachory K; Charbonneau, David; Dittmann, Jason; Pineda, J Sebastian

    2015-01-01

    Using spectroscopic observations and photometric light curves of 238 nearby M dwarfs from the MEarth exoplanet transit survey, we examine the relationships between magnetic activity (quantified by H-alpha emission), rotation period, and stellar age. Previous attempts to investigate the relationship between magnetic activity and rotation in these stars were hampered by the limited number of M dwarfs with measured rotation periods (and the fact that vsini measurements probe only rapid rotation). However, the photometric data from MEarth allows us to probe a wide range of rotation periods for hundreds of M dwarf stars (from shorter than than one to longer than 100 days). Over all M spectral types that we probe, we find that the presence of magnetic activity is tied to rotation, including for late-type, fully convective M dwarfs. We also find evidence that the fraction of late-type M dwarfs that are active may be higher at longer rotation periods compared to their early-type counterparts, with several active, lat...

  10. When does an old nova become a dwarf nova? Kinematics and age of the nova shell of the dwarf nova AT Cnc

    CERN Document Server

    Shara, Michael M; Martin, Thomas; Alarie, Alexandre

    2016-01-01

    The Z Cam-type dwarf nova AT Cnc displays a classical nova (CN) shell, demonstrating that mass transfer in cataclysmic binaries decreases substantially after a CN eruption. The hibernation scenario of cataclysmic binaries predicts such a decrease, on a timescale of a few centuries. In order to measure the time since AT Cnc's last CN eruption, we have measured the radial velocities of a hundred clumps in its ejecta with SITELLE, CFHT's recently commissioned imaging Fourier transform spectrometer. These range from -455 to +490 km/s. Coupled with the known distance to AT Cnc of 460 pc (Shara 2012), the size of AT Cnc's shell, and a simple model of nova ejecta deceleration, we determine that the last CN eruption of this system occurred $330_{-90}^{+135}$ years ago. This is the most rapid transition from a high mass transfer rate, novalike variable to a low mass transfer rate, dwarf nova yet measured, and in accord with the hibernation scenario of cataclysmic binaries. We conclude by noting the similarity in deduc...

  11. When does an old nova become a dwarf nova? Kinematics and age of the nova shell of the dwarf nova AT Cancri

    Science.gov (United States)

    Shara, Michael M.; Drissen, Laurent; Martin, Thomas; Alarie, Alexandre; Stephenson, F. Richard

    2017-02-01

    The Z Cam-type dwarf nova AT Cancri (AT Cnc) displays a classical nova (CN) shell, demonstrating that mass transfer in cataclysmic binaries decreases substantially after a CN eruption. The hibernation scenario of cataclysmic binaries predicts such a decrease, on a time-scale of a few centuries. In order to measure the time since AT Cnc's last CN eruption, we have measured the radial velocities of a hundred clumps in its ejecta with SITELLE, Canada-France-Hawaii Telescope's recently commissioned imaging Fourier transform spectrometer. These range from -455 to +490 km s-1. Coupled with the known distance to AT Cnc of 460 pc, the size of AT Cnc's shell, and a simple model of nova ejecta deceleration, we determine that the last CN eruption of this system occurred 330_{-90}^{+135} yr ago. This is the most rapid transition from a high mass-transfer rate, nova-like variable to a low mass-transfer rate, dwarf nova yet measured, and in accord with the hibernation scenario of cataclysmic binaries. We conclude by noting the similarity in the deduced outburst date (within a century of 1686 CE) of AT Cnc to a `guest star' reported in the constellation Cancer by Korean observers in 1645 CE.

  12. Stellar Kinematics and Metallicities in the Draco and Ursa Minor Dwarf Spheroidal Galaxies from WHT/AF2-WYFFOS

    NARCIS (Netherlands)

    Jin, S.; Irwin, M.; Tolstoy, E.; Lewis, J.; Hartke, J.; Skillen, I.; Barcells, M.; Trager, S.

    2016-01-01

    We present preliminary results from our chemo-dynamical survey of two Milky Way dwarf spheroidal (dSph) galaxies, Draco and Ursa Minor. The two galaxies have similar radial velocities and reside in close proximity in the outskirts of the Milky Way halo, yet exhibit noteworthy differences in their mo

  13. Chemistry and Kinematics of the Late-Forming Dwarf Irregular Galaxies Leo A, Aquarius, and Sagittarius DIG

    CERN Document Server

    Kirby, Evan N; Held, Enrico V; Cohen, Judith G; Cole, Andrew A; Manning, Ellen M; Skillman, Evan D; Weisz, Daniel R

    2016-01-01

    We present Keck/DEIMOS spectroscopy of individual stars in the relatively isolated Local Group dwarf galaxies Leo A, Aquarius, and the Sagittarius dwarf irregular galaxy. The three galaxies--but especially Leo A and Aquarius--share in common delayed star formation histories relative to many other isolated dwarf galaxies. The stars in all three galaxies are supported by dispersion. We found no evidence of stellar velocity structure, even for Aquarius, which has rotating HI gas. The velocity dispersions indicate that all three galaxies are dark matter-dominated, with dark-to-baryonic mass ratios ranging from $4.4^{+1.1}_{-0.8}$ (SagDIG) to $9.6^{+2.5}_{-1.8}$ (Aquarius). Leo A and SagDIG have lower stellar metallicities than Aquarius, and they also have higher gas fractions, both of which would be expected if Aquarius were farther along in its chemical evolution. The metallicity distribution of Leo A is inconsistent with a Closed or Leaky Box model of chemical evolution, suggesting that the galaxy was pre-enric...

  14. The Next Generation Virgo Cluster Survey. VI. The Kinematics of Ultra-compact Dwarfs and Globular Clusters in M87

    CERN Document Server

    Zhang, Hong-Xin; Cote, Patrick; Liu, Chengze; Ferrarese, Laura; Cuillandre, Jean-Charles; Caldwell, Nelson; Gwyn, Stephen D J; Jordan, Andres; Lancon, Ariane; Li, Biao; Munoz, Roberto P; Puzia, Thomas H; Bekki, Kenji; Blakeslee, John; Boselli, Alessandro; Drinkwater, Michael J; Duc, Pierre-Alain; Durrell, Patrick; Emsellem, Eric; Firth, Peter; Sanchez-Janssen, Ruben

    2015-01-01

    The origin of ultra-compact dwarfs (UCDs)--objects larger and more massive than typical globular clusters (GCs), but more compact than typical dwarf galaxies--has been hotly debated in the 15 years since their discovery. Even whether UCDs should be considered galactic in origin, or simply the most extreme GCs, is not yet settled. We present the dynamical properties of 97 spectroscopically confirmed UCDs (rh >~10 pc) and 911 GCs associated with central cD galaxy of the Virgo cluster, M87. Our UCDs, of which 89% have M_star > ~2X10^6 M_sun and 92% are as blue as the classic blue GCs, nearly triple the sample of previous confirmed Virgo UCDs, providing by far the best opportunity for studying the global dynamics of a UCD system. We found that (1) UCDs have a surface number density profile that is shallower than that of the blue GCs in the inner ~ 70 kpc and as steep as that of the red GCs at larger radii; (2) UCDs exhibit a significantly stronger rotation than the GCs, and the blue GCs seem to have a velocity fi...

  15. ALFALFA Discovery of the Nearby Gas-rich Dwarf Galaxy Leo P. V. Neutral Gas Dynamics and Kinematics

    CERN Document Server

    Bernstein-Cooper, Elijah Z; Elson, Edward C; Warren, Steven R; Chengalur, Jayaram; Skillman, Evan D; Adams, Elizabeth A K; Bolatto, Alberto D; Giovanelli, Riccardo; Haynes, Martha P; McQuinn, Kristen B W; Pardy, Stephen A; Rhode, Katherine L; Salzer, John J

    2014-01-01

    We present new HI spectral line imaging of the extremely metal-poor, star-forming dwarf irregular galaxy Leo P. Our HI images probe the global neutral gas properties and the local conditions of the interstellar medium (ISM). The HI morphology is slightly elongated along the optical major-axis. We do not find obvious signatures of interaction or infalling gas at large spatial scales. The neutral gas disk shows obvious rotation, although the velocity dispersion is comparable to the rotation velocity. The rotation amplitude is estimated to be V_c = 15 +/- 5 km/s. Within the HI radius probed by these observations, the mass ratio of gas to stars is roughly 2:1, while the ratio of the total mass to the baryonic mass is ~15:1. We use this information to place Leo P on the baryonic Tully-Fisher relation, testing the baryonic content of cosmic structures in a sparsely populated portion of parameter space that has hitherto been occupied primarily by dwarf spheroidal galaxies. We detect the signature of two temperature ...

  16. Formation and evolution of dwarf early-type galaxies in the Virgo cluster II. Kinematic Scaling Relations

    CERN Document Server

    Toloba, E; Peletier, R; Falcon-Barroso, J; van de Ven, G; Gorgas, J

    2012-01-01

    We place our sample of 18 Virgo dwarf early-type galaxies (dEs) on the V-K - velocity dispersion, Faber-Jackson, and Fundamental Plane (FP) scaling relations for massive early-type galaxies (Es). We use a generalized velocity dispersion, which includes rotation, to be able to compare the location of both rotationally and pressure supported dEs with those of early and late-type galaxies. We find that dEs seem to bend the Faber-Jackson relation of Es to lower velocity dispersions, being the link between Es and dwarf spheroidal galaxies (dSphs). Regarding the FP relation, we find that dEs are significantly offset with respect to massive hot stellar systems, and re-casting the FP into the so-called kappa-space suggests that this offset is related to dEs having a total mass-to-light ratio higher than Es but still significantly lower than dSph galaxies. Given a stellar mass-to-light ratio based on the measured line indices of dEs, the FP offset allows us to infer that the dark matter fraction within the half light ...

  17. Alfalfa discovery of the nearby gas-rich dwarf galaxy LEO P. V. Neutral gas dynamics and kinematics

    Energy Technology Data Exchange (ETDEWEB)

    Bernstein-Cooper, Elijah Z.; Pardy, Stephen A. [Department of Astronomy, University of Wisconsin, 475 N Charter Street, Madison, WI 53706 (United States); Cannon, John M., E-mail: ezbc@astro.wisc.edu, E-mail: spardy@astro.wisc.edu, E-mail: jcannon@macalester.edu [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); and others

    2014-08-01

    We present new H I spectral line imaging of the extremely metal-poor, star-forming dwarf irregular galaxy Leo P. Our H I images probe the global neutral gas properties and the local conditions of the interstellar medium (ISM). The H I morphology is slightly elongated along the optical major axis. We do not find obvious signatures of interaction or infalling gas at large spatial scales. The neutral gas disk shows obvious rotation, although the velocity dispersion is comparable to the rotation velocity. The rotation amplitude is estimated to be V {sub c} =15 ± 5 km s{sup –1}. Within the H I radius probed by these observations, the mass ratio of gas to stars is roughly 2:1, while the ratio of the total mass to the baryonic mass is ≳15:1. We use this information to place Leo P on the baryonic Tully-Fisher relation, testing the baryonic content of cosmic structures in a sparsely populated portion of parameter space that has hitherto been occupied primarily by dwarf spheroidal galaxies. We detect the signature of two temperature components in the neutral ISM of Leo P; the cold and warm components have characteristic velocity widths of 4.2 ± 0.9 km s{sup –1} and 10.1 ± 1.2 km s{sup –1}, corresponding to kinetic temperature upper limits of ∼1100 K and ∼6200 K, respectively. The cold H I component is unresolved at a physical resolution of 200 pc. The highest H I surface densities are observed in close physical proximity to the single H II region. A comparison of the neutral gas properties of Leo P with other extremely metal-deficient (XMD) galaxies reveals that Leo P has the lowest neutral gas mass of any known XMD, and that the dynamical mass of Leo P is more than two orders of magnitude smaller than any known XMD with comparable metallicity.

  18. The Shape of LITTLE THINGS Dwarf Galaxies DDO 46 and DDO 168: Understanding the stellar and gas kinematics

    CERN Document Server

    Johnson, Megan C; Wood, Sarah; Oh, Se-Heon; Zhang, Hong-Xin; Herrmann, Kimberly A; Levine, Stephen E

    2015-01-01

    We present the stellar and gas kinematics of DDO 46 and DDO 168 from the LITTLE THINGS survey and determine their respective Vmax/sigma_z,0 values. We used the KPNO's 4-meter telescope with the Echelle spectrograph as a long-slit spectrograph. We acquired spectra of DDO 168 along four position angles by placing the slit over the morphological major and minor axes and two intermediate position angles. However, due to poor weather conditions during our observing run for DDO 46, we were able to extract only one useful data point from the morphological major axis. We determined a central stellar velocity dispersion perpendicular to the disk, sigma_z,0, of 13.5+/-8 km/s for DDO 46 and of 10.7+/-2.9 km/s for DDO 168. We then derived the maximum rotation speed in both galaxies using the LITTLE THINGS HI data. We separated bulk motions from non-circular motions using a double Gaussian decomposition technique and applied a tilted-ring model to the bulk velocity field. We corrected the observed HI rotation speeds for ...

  19. A GMOS-N IFU study of the central H ii region in the blue compact dwarf galaxy NGC 4449: kinematics, nebular metallicity and star formation

    Science.gov (United States)

    Kumari, Nimisha; James, Bethan L.; Irwin, Mike J.

    2017-10-01

    We use integral field spectroscopic (IFS) observations from the Gemini Multi-Object Spectrograph North (GMOS-N) to study the central H ii region in a nearby blue compact dwarf (BCD) galaxy NGC 4449. The IFS data enable us to explore the variation of physical and chemical conditions of the star-forming region and the surrounding gas on spatial scales as small as 5.5 pc. Our kinematical analysis shows possible signatures of shock ionization and shell structures in the surroundings of the star-forming region. The metallicity maps of the region, created using direct Te and indirect strong line methods (R23, O3N2 and N2), do not show any chemical variation. From the integrated spectrum of the central H ii region, we find a metallicity of 12 + log(O/H) = 7.88 ± 0.14 ({˜ }0.15^{+0.06}_{-0.04} Z⊙) using the direct method. Comparing the central H ii region metallicity derived here with those of H ii regions throughout this galaxy from previous studies, we find evidence of increasing metallicity with distance from the central nucleus. Such chemical inhomogeneities can be due to several mechanisms, including gas loss via supernova blowout, galactic winds or metal-poor gas accretion. However, we find that the localized area of decreased metallicity aligns spatially with the peak of star-forming activity in the galaxy, suggesting that gas accretion may be at play here. Spatially resolved IFS data for the entire galaxy are required to confirm the metallicity inhomogeneity found in this study and determine its possible cause.

  20. Flares of Nearby, Mid-to-late M-dwarfs Characterized by the MEarth Project

    Science.gov (United States)

    Mondrik, Nicholas; Charbonneau, David; Irwin, Jonathan; Newton, Elisabeth R.

    2017-01-01

    Stellar flares are both a curse and a blessing: Transit and radial velocity searches for exoplanets are hindered by the variability caused by flares, while the characteristics of this variability offer valuable insight into the magnetic properties of the star. We present an analysis of flare events of nearby, mid-to-late M-dwarfs from the MEarth Project. MEarth consists of a northern and a southern array of 8 telescopes each that photometrically monitors most mid-to-late M-dwarfs within 30 parsecs. Although the initial motivation was to search for exoplanet transits, the cadence of approximately 20 minutes is well-suited to capturing long-lived flares. However, MEarth employs a single, wide, red bandpass, which poses challenges to the robust detection of flare events, which are typically bluer in color. Using MEarth data, our team has recently published trigonometric parallaxes and estimates of rotation periods for an unprecedented number of nearby low-mass stars. We also gathered supplementary optical and near infrared spectra of a subset of these stars. We describe here the properties of the flares detected by MEarth, and explore the relation of the presence of flares on individual stars with stellar parameters such as rotational period, mass, and H-alpha equivalent width. We also provide an estimate of flare rate for individual stars by injecting flares into our pipeline.The MEarth project acknowledges funding from the National Science Foundation and the David and Lucile Packard Foundation Fellowship for Science and Engineering. This work was made possible through the support of a grant from the John Templeton Foundation.

  1. Juvenile Ultracool Dwarfs

    CERN Document Server

    Rice, Emily L; Cruz, Kelle; Barman, Travis; Looper, Dagny; Malo, Lison; Mamajek, Eric E; Metchev, Stanimir; Shkolnik, Evgenya L

    2011-01-01

    Juvenile ultracool dwarfs are late spectral type objects (later than ~M6) with ages between 10 Myr and several 100 Myr. Their age-related properties lie intermediate between very low mass objects in nearby star-forming regions (ages 1-5 Myr) and field stars and brown dwarfs that are members of the disk population (ages 1-5 Gyr). Kinematic associations of nearby young stars with ages from ~10-100 Myr provide sources for juvenile ultracool dwarfs. The lowest mass confirmed members of these groups are late-M dwarfs. Several apparently young L dwarfs and a few T dwarfs are known, but they have not been kinematically associated with any groups. Normalizing the field IMF to the high mass population of these groups suggests that more low mass (mainly late-M and possibly L dwarf) members have yet to be found. The lowest mass members of these groups, along with low mass companions to known young stars, provide benchmark objects with which spectroscopic age indicators for juvenile ultracool dwarfs can be calibrated and...

  2. Abundances as Tracers of the Formation and Evolution of (Dwarf) Galaxies

    CERN Document Server

    Tolstoy, E

    2004-01-01

    This aims to be an overview of what detailed observations of individual stars in nearby dwarf galaxies may teach us about galaxy evolution. This includes some early results from the DART (Dwarf Abundances and Radial velocity Team) Large Programme at ESO. This project has used 2.2m/WFI and VLT/FLAMES to obtain spectra of large samples of individual stars in nearby dwarf spheroidal galaxies and determine accurate abundances and kinematics. These results can be used to trace the formation and evolution of nearby galaxies from the earliest times to the present.

  3. WISDOM project - I. Black hole mass measurement using molecular gas kinematics in NGC 3665

    Science.gov (United States)

    Onishi, Kyoko; Iguchi, Satoru; Davis, Timothy A.; Bureau, Martin; Cappellari, Michele; Sarzi, Marc; Blitz, Leo

    2017-07-01

    As a part of the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM) project, we present an estimate of the mass of the supermassive black hole (SMBH) in the nearby fast-rotator early-type galaxy NGC 3665. We obtained the Combined Array for Research in Millimeter Astronomy (CARMA) B and C array observations of the 12CO(J = 2 - 1) emission line with a combined angular resolution of 0.59 arcsec. We analysed and modelled the three-dimensional molecular gas kinematics, obtaining a best-fitting SMBH mass M_BH=5.75^{+1.49}_{-1.18} × 108 M⊙, a mass-to-light ratio at H-band (M/L)H = 1.45 ± 0.04 (M/L)⊙,H and other parameters describing the geometry of the molecular gas disc (statistical errors, all at 3σ confidence). We estimate the systematic uncertainties on the stellar M/L to be ≈0.2 (M/L)⊙,H, and on the SMBH mass to be ≈0.4 × 108 M⊙. The measured SMBH mass is consistent with that estimated from the latest correlations with galaxy properties. Following our older works, we also analysed and modelled the kinematics using only the major-axis position-velocity diagram, and conclude that the two methods are consistent.

  4. 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.

  5. The APOSTLE project: Local Group kinematic mass constraints and simulation candidate selection

    CERN Document Server

    Fattahi, Azadeh; Sawala, Till; Frenk, Carlos S; Oman, Kyle A; Crain, Robert A; Furlong, Michelle; Schaller, Matthieu; Schaye, Joop; Theuns, Tom; Jenkins, Adrian

    2015-01-01

    We use a large sample of isolated dark matter halo pairs drawn from cosmological N-body simulations to identify candidate systems whose kinematics match that of the Local Group of Galaxies (LG). We find, in agreement with the "timing argument" and earlier work, that the separation and approach velocity of the Milky Way (MW) and Andromeda (M31) galaxies favour a total mass for the pair of ~ 5*10^12 M_sun. A mass this large, however, is difficult to reconcile with the small relative tangential velocity of the pair, as well as with the small deceleration from the Hubble flow observed for the most distant LG members. Halo pairs that match these three criteria have average masses a factor of ~2 times smaller than suggested by the timing argument, but with large dispersion, spanning more than a decade in mass. Guided by these results, we have selected 12 halo pairs with total mass in the range 1.6-3.6 *10^12 M_sun for the APOSTLE project (A Project Of Simulations of The Local Environment), a suite of resimulations ...

  6. STELLAR METALLICITIES AND KINEMATICS IN A GAS-RICH DWARF GALAXY : FIRST CALCIUM TRIPLET SPECTROSCOPY OF RED GIANT BRANCH STARS IN WLM

    NARCIS (Netherlands)

    Leaman, Ryan; Cole, Andrew A.; Venn, Kim A.; Tolstoy, Eline; Irwin, Mike J.; Szeifert, Thomas; Skillman, Evan D.; McConnachie, Alan W.

    2009-01-01

    We present the first determination of the radial velocities and metallicities of 78 red giant stars in the isolated dwarf irregular galaxy WLM. Observations of the calcium II triplet in these stars were made with FORS2 at the VLT-UT2 in two separated fields of view in WLM, and the [Fe/H] values were

  7. Kinematic Sunyaev-Zel'dovich effect with projected fields. II. Prospects, challenges, and comparison with simulations

    Science.gov (United States)

    Ferraro, Simone; Hill, J. Colin; Battaglia, Nick; Liu, Jia; Spergel, David N.

    2016-12-01

    The kinematic Sunyaev-Zel'dovich (kSZ) signal is a powerful probe of the cosmic baryon distribution. The kSZ signal is proportional to the integrated free electron momentum rather than the electron pressure (which sources the thermal SZ signal). Since velocities should be unbiased on large scales, the kSZ signal is an unbiased tracer of the large-scale electron distribution, and thus can be used to detect the "missing baryons" that evade most observational techniques. While most current methods for kSZ extraction rely on the availability of very accurate redshifts, we revisit a method that allows measurements even in the absence of redshift information for individual objects. It involves cross-correlating the square of an appropriately filtered cosmic microwave background (CMB) temperature map with a projected density map constructed from a sample of large-scale structure tracers. We show that this method will achieve high signal-to-noise when applied to the next generation of high-resolution CMB experiments, provided that component separation is sufficiently effective at removing foreground contamination. Considering statistical errors only, we forecast that this estimator can yield S /N ≈3 , 120 and over 150 for Planck, Advanced ACTPol, and a hypothetical Stage IV CMB experiment, respectively, in combination with a galaxy catalog from WISE, and about 20% larger S /N for a galaxy catalog from the proposed SPHEREx experiment. We show that the basic estimator receives a contribution due to leakage from CMB lensing, but that this term can be effectively removed by either direct measurement or marginalization, with little effect on the kSZ significance. We discuss possible sources of systematic contamination and propose mitigation strategies for future surveys. We compare the theoretical predictions to numerical simulations and validate the approximations in our analytic approach. This work serves as a companion paper to the first kSZ measurement with this method

  8. THE ACS LCID PROJECT: ON THE ORIGIN OF DWARF GALAXY TYPES—A MANIFESTATION OF THE HALO ASSEMBLY BIAS?

    Energy Technology Data Exchange (ETDEWEB)

    Gallart, Carme; Monelli, Matteo; Aparicio, Antonio; Battaglia, Giuseppina; Drozdovsky, Igor; Hidalgo, Sebastian L. [Instituto de Astrofísica de Canarias, La Laguna, Tenerife (Spain); Mayer, Lucio [Institut für Theoretische Physik, University of Zurich, Zürich (Switzerland); Bernard, Edouard J. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Cassisi, Santi [INAF-Osservatorio Astronomico di Collurania, Teramo (Italy); Cole, Andrew A. [School of Physical Sciences, University of Tasmania, Private Bag 37, Hobart, TAS 7005 (Australia); Dolphin, Andrew E. [Raytheon, 1151 E. Hermans Road, Tucson, AZ 85706 (United States); Navarro, Julio F. [Department of Physics and Astronomy, University of Victoria, PO Box 1700, STN CSC, Victoria, BC V8W 3P6 (Canada); Salvadori, Stefania [Kapteyn Astronomical Institute, Landleven 12, NL-9747 AD Groningen (Netherlands); Skillman, Evan D. [Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN (United States); Stetson, Peter B. [Herzberg Astronomy and Astrophysics, National Research Council Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Weisz, Daniel R., E-mail: monelli@iac.es [Astronomy Department, University of Washington, Box 351580, Seattle, WA (United States)

    2015-10-01

    We discuss how knowledge of the whole evolutionary history of dwarf galaxies, including details on the early star formation events, can provide insight on the origin of the different dwarf galaxy types. We suggest that these types may be imprinted by the early conditions of formation rather than only being the result of a recent morphological transformation driven by environmental effects. We present precise star formation histories of a sample of Local Group dwarf galaxies, derived from color–magnitude diagrams reaching the oldest main-sequence turnoffs. We argue that these galaxies can be assigned to two basic types: fast dwarfs that started their evolution with a dominant and short star formation event and slow dwarfs that formed a small fraction of their stars early and have continued forming stars until the present time (or almost). These two different evolutionary paths do not map directly onto the present-day morphology (dwarf spheroidal versus dwarf irregular). Slow and fast dwarfs also differ in their inferred past location relative to the Milky Way and/or M31, which hints that slow dwarfs were generally assembled in lower-density environments than fast dwarfs. We propose that the distinction between a fast and slow dwarf galaxy primarily reflects the characteristic density of the environment where they form. At a later stage, interaction with a large host galaxy may play a role in the final gas removal and ultimate termination of star formation.

  9. The Carina Project. X. On the kinematics of old and intermediate-age stellar populations

    CERN Document Server

    Fabrizio, M; Nonino, M; Lokas, E L; Ferraro, I; Iannicola, G; Buonanno, R; Cassisi, S; Coppola, G; Dall'Ora, M; Gilmozzi, R; Marconi, M; Monelli, M; Romaniello, M; Stetson, P B; Thévenin, F; Walker, A R

    2016-01-01

    We present new radial velocity (RV) measurements of old (horizontal branch) and intermediate-age (red clump) stellar tracers in the Carina dwarf spheroidal. They are based on more than 2,200 low-resolution spectra collected with VIMOS at VLT. The targets are faint (20dwarf galaxy orbit...

  10. The scatter about the "Universal" dwarf spheroidal mass profile: A kinematic study of the M31 satellites, And V and And VI

    CERN Document Server

    Collins, M L M; Rich, R M; Ibata, R A; Irwin, M J; Peñarrubia, J; Arimoto, N; Brooks, A M; Lewis, G F; McConnachie, A W; Venn, K

    2011-01-01

    While the satellites of the Milky Way (MW) have been shown to be largely consistent in terms of their mass contained within one half--light radius (M_{half}) with a "Universal" mass profile, a number of M31 satellites are found to be inconsistent with such relations, and seem kinematically colder in their central regions than their MW cousins. In this work, we present new kinematic and updated structural properties for two M31 dSphs, And V and And VI using data from the Keck Low Resolution Imaging Spectrograph (LRIS) and the DEep Imaging Multi-Object Spectrograph (DEIMOS) instruments and the Subaru Suprime-Cam imager. We measure systemic velocities of v_r=-393.1+/-4.2km/s and -344.8+/-2.5km/s, and dispersions of sigma_v=11.5{+5.3}{-4.4}km/s and sigma_v=9.4{+3.2}{-2.4}km/s for And V and And VI respectively, meaning these two objects are consistent with the trends in sigma_v and r_{half} set by their MW counterparts. We also investigate the nature of this scatter about the MW dSph mass profiles for the "Classic...

  11. Inverse Kinematics using Quaternions

    DEFF Research Database (Denmark)

    Henriksen, Knud; Erleben, Kenny; Engell-Nørregård, Morten

    In this project I describe the status of inverse kinematics research, with the focus firmly on the methods that solve the core problem. An overview of the different methods are presented Three common methods used in inverse kinematics computation have been chosen as subject for closer inspection....... suite, developed in this project and in [4]. Source code developed for this project includes the CCD method , improvements on the BFGS method and Jacobian inverse originally developed in [4]....

  12. Three-Dimensional Optical Reconstruction of Vocal Fold Kinematics Using High-Speed Video With a Laser Projection System.

    Science.gov (United States)

    Luegmair, Georg; Mehta, Daryush D; Kobler, James B; Döllinger, Michael

    2015-12-01

    Vocal fold kinematics and its interaction with aerodynamic characteristics play a primary role in acoustic sound production of the human voice. Investigating the temporal details of these kinematics using high-speed videoendoscopic imaging techniques has proven challenging in part due to the limitations of quantifying complex vocal fold vibratory behavior using only two spatial dimensions. Thus, we propose an optical method of reconstructing the superior vocal fold surface in three spatial dimensions using a high-speed video camera and laser projection system. Using stereo-triangulation principles, we extend the camera-laser projector method and present an efficient image processing workflow to generate the three-dimensional vocal fold surfaces during phonation captured at 4000 frames per second. Initial results are provided for airflow-driven vibration of an ex vivo vocal fold model in which at least 75% of visible laser points contributed to the reconstructed surface. The method captures the vertical motion of the vocal folds at a high accuracy to allow for the computation of three-dimensional mucosal wave features such as vibratory amplitude, velocity, and asymmetry.

  13. The ACS LCID Project: On the Origin of Dwarf Galaxy Types—A Manifestation of the Halo Assembly Bias?

    NARCIS (Netherlands)

    Gallart, Carme; Monelli, Matteo; Mayer, Lucio; Aparicio, Antonio; Battaglia, Giuseppina; Bernard, Edouard J.; Cassisi, Santi; Cole, Andrew A.; Dolphin, Andrew E.; Drozdovsky, Igor; Hidalgo, Sebastian L.; Navarro, Julio F.; Salvadori, Stefania; Skillman, Evan D.; Stetson, Peter B.; Weisz, Daniel R.

    2015-01-01

    We discuss how knowledge of the whole evolutionary history of dwarf galaxies, including details on the early star formation events, can provide insight on the origin of the different dwarf galaxy types. We suggest that these types may be imprinted by the early conditions of formation rather than onl

  14. The ACS LCID Project: On the origin of dwarf galaxy types: a manifestation of the halo assembly bias?

    CERN Document Server

    Gallart, C; Mayer, L; Aparicio, A; Battaglia, G; Bernard, E J; Cassisi, S; Cole, A A; Dolphin, A E; Drozdovsky, I; HIdalgo, S L; Navarro, J F; Salvadori, S; Skillman, E D; Stetson, P B; Weisz, D R

    2015-01-01

    We discuss how knowledge of the whole evolutionary history of dwarf galaxies, including details on the early star formation events, can provide insight on the origin of the different dwarf galaxy types. We suggest that these types may be imprinted by the early conditions of formation rather than being only the result of a recent morphological transformation driven by environmental effects. We present precise star formation histories of a sample of Local Group dwarf galaxies, derived from colour-magnitude diagrams reaching the oldest main-sequence turnoffs. We argue that these galaxies can be assigned to two basic types: fast dwarfs that started their evolution with a dominant and short star formation event, and slow dwarfs that formed a small fraction of their stars early and have continued forming stars until the present time (or almost). These two different evolutionary paths do not map directly onto the present-day morphology (dwarf spheroidal vs dwarf irregular). Slow and fast dwarfs also differ in their ...

  15. The ACS LCID Project: On the Origin of Dwarf Galaxy Types—A Manifestation of the Halo Assembly Bias?

    NARCIS (Netherlands)

    Gallart, Carme; Monelli, Matteo; Mayer, Lucio; Aparicio, Antonio; Battaglia, Giuseppina; Bernard, Edouard J.; Cassisi, Santi; Cole, Andrew A.; Dolphin, Andrew E.; Drozdovsky, Igor; Hidalgo, Sebastian L.; Navarro, Julio F.; Salvadori, Stefania; Skillman, Evan D.; Stetson, Peter B.; Weisz, Daniel R.

    2015-01-01

    We discuss how knowledge of the whole evolutionary history of dwarf galaxies, including details on the early star formation events, can provide insight on the origin of the different dwarf galaxy types. We suggest that these types may be imprinted by the early conditions of formation rather than

  16. Binaries discovered by the MUCHFUSS project SDSS J08205+0008 - An eclipsing subdwarf B binary with brown dwarf companion

    CERN Document Server

    Geier, S; Drechsel, H; Heber, U; Kupfer, T; Tillich, A; Oestensen, R H; Smolders, K; Degroote, P; Maxted, P F L; Barlow, B N; Gaensicke, B T; Marsh, T R; Napiwotzki, R

    2011-01-01

    Hot subdwarf B stars (sdBs) are extreme horizontal branch stars believed to originate from close binary evolution. Indeed about half of the known sdB stars are found in close binaries with periods ranging from a few hours to a few days. The enormous mass loss required to remove the hydrogen envelope of the red-giant progenitor almost entirely can be explained by common envelope ejection. A rare subclass of these binaries are the eclipsing HW Vir binaries where the sdB is orbited by a dwarf M star. Here we report the discovery of an HW Vir system in the course of the MUCHFUSS project. A most likely substellar object ($\\simeq0.068\\,M_{\\rm \\odot}$) was found to orbit the hot subdwarf J08205+0008 with a period of 0.096 days. Since the eclipses are total, the system parameters are very well constrained. J08205+0008 has the lowest unambiguously measured companion mass yet found in a subdwarf B binary. This implies that the most likely substellar companion has not only survived the engulfment by the red-giant envelo...

  17. SHIELD: Neutral Gas Kinematics and Dynamics

    CERN Document Server

    McNichols, Andrew T; Nims, Elise; Cannon, John M; Adams, Elizabeth A K; Bernstein-Cooper, Elijah Z; Giovanelli, Riccardo; Haynes, Martha P; Józsa, Gyula I G; McQuinn, Kristen B W; Salzer, John J; Skillman, Evan D; Warren, Steven R; Dolphin, Andrew; Elson, E C; Haurberg, Nathalie; Ott, Jürgen; Saintonge, Amelie; Cave, Ian; Hagen, Cedric; Huang, Shan; Janowiecki, Steven; Marshall, Melissa V; Thomann, Clara M; Van Sistine, Angela

    2016-01-01

    We present kinematic analyses of the 12 galaxies in the "Survey of HI in Extremely Low-mass Dwarfs" (SHIELD). We use multi-configuration interferometric observations of the HI 21cm emission line from the Karl G. Jansky Very Large Array (VLA) to produce image cubes at a variety of spatial and spectral resolutions. Both two- and three-dimensional fitting techniques are employed in an attempt to derive inclination-corrected rotation curves for each galaxy. In most cases, the comparable magnitudes of velocity dispersion and projected rotation result in degeneracies that prohibit unambiguous circular velocity solutions. We thus make spatially resolved position-velocity cuts, corrected for inclination using the stellar components, to estimate the circular rotation velocities. We find circular velocities <30 km/s for the entire survey population. Baryonic masses are calculated using single-dish HI fluxes from Arecibo and stellar masses derived from HST and Spitzer imaging. Comparison is made with total dynamical ...

  18. The Kinematic Sunyaev-Zel'dovich Effect with Projected Fields II: prospects, challenges, and comparison with simulations

    CERN Document Server

    Ferraro, Simone; Battaglia, Nick; Liu, Jia; Spergel, David N

    2016-01-01

    The kinematic Sunyaev-Zel'dovich (kSZ) signal is a powerful probe of the cosmic baryon distribution. The kSZ signal is proportional to the integrated free electron momentum rather than the electron pressure (which sources the thermal SZ signal). Since velocities should be unbiased on large scales, the kSZ signal is an unbiased tracer of the large-scale electron distribution, and thus can be used to detect the "missing baryon" that evade most observational techniques. While most current methods for kSZ extraction rely on the availability of very accurate redshifts, we revisit a method that allows measurements even in the absence of redshift information for individual objects. It involves cross-correlating the square of an appropriately filtered cosmic microwave background (CMB) temperature map with a projected density map constructed from a sample of large-scale structure tracers. We show that this method will achieve high signal-to-noise when applied to the next generation of high-resolution CMB experiments, ...

  19. CARMA Large Area Star Formation Survey: Project Overview with Analysis of Dense Gas Structure and Kinematics in Barnard 1

    CERN Document Server

    Storm, S; Fernández-López, M; Lee, K I; Looney, L W; Teuben, P J; Rosolowsky, E; Arce, H G; Ostriker, E C; Segura-Cox, D; Pound, M W; Salter, D M; Volgenau, N H; Shirley, Y L; Chen, C; Gong, H; Plunkett, A L; Tobin, J J; Kwon, W; Isella, A; Kauffmann, J; Tassis, K; Crutcher, R M; Gammie, C F; Testi, L

    2014-01-01

    We present details of the CARMA Large Area Star Formation Survey (CLASSy), while focusing on observations of Barnard 1. CLASSy is a CARMA Key Project that spectrally imaged N2H+, HCO+, and HCN (J=1-0 transitions) across over 800 square arcminutes of the Perseus and Serpens Molecular Clouds. The observations have angular resolution near 7" and spectral resolution near 0.16 km/s. We imaged ~150 square arcminutes of Barnard 1, focusing on the main core, and the B1 Ridge and clumps to its southwest. N2H+ shows the strongest emission, with morphology similar to cool dust in the region, while HCO+ and HCN trace several molecular outflows from a collection of protostars in the main core. We identify a range of kinematic complexity, with N2H+ velocity dispersions ranging from ~0.05-0.50 km/s across the field. Simultaneous continuum mapping at 3 mm reveals six compact object detections, three of which are new detections. A new non-binary dendrogram algorithm is used to analyze dense gas structures in the N2H+ position...

  20. The projected gravitational potential of the galaxy cluster MACS~J1206 derived from galaxy kinematics

    CERN Document Server

    Stock, Dennis; Sarli, Eleonora; Bartelmann, Matthias

    2015-01-01

    We reconstruct the radial profile of the projected gravitational potential of the galaxy cluster MACS-J1206 from 592 spectroscopic measurements of velocities of cluster members. For doing so, we use a method we have developed recently based on the Richardson-Lucy deprojection algorithm and an inversion of the spherically-symmetric Jeans equation. We find that, within the uncertainties, our reconstruction agrees very well with a potential reconstruction from weak and strong gravitational lensing as well as with a potential obtained from X-ray measurements. In addition, our reconstruction is in good agreement with several common analytic profiles of the lensing potential. Varying the anisotropy parameter in the Jeans equation, we find that isotropy parameters which are either small, $\\beta\\lesssim0.2$, or decrease with radius yield potential profiles which strongly disagree with that obtained from gravitational lensing. We achieve the best agreement between our potential profile and the profile from gravitation...

  1. CARMA Large Area Star Formation Survey: project overview with analysis of dense gas structure and kinematics in Barnard 1

    Energy Technology Data Exchange (ETDEWEB)

    Storm, Shaye; Mundy, Lee G.; Lee, Katherine I.; Teuben, Peter; Pound, Marc W.; Salter, Demerese M.; Chen, Che-Yu; Gong, Hao [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Fernández-López, Manuel; Looney, Leslie W.; Segura-Cox, Dominique M. [Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801 (United States); Rosolowsky, Erik [Departments of Physics and Statistics, University of British Columbia, Okanagan Campus, 3333 University Way, Kelowna BC V1V 1V7 (Canada); Arce, Héctor G.; Plunkett, Adele L. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Ostriker, Eve C. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Volgenau, Nikolaus H. [Owens Valley Radio Observatory, MC 105-24 OVRO, Pasadena, CA 91125 (United States); Shirley, Yancy L. [Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Tobin, John J. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Kwon, Woojin [SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen (Netherlands); Isella, Andrea, E-mail: sstorm@astro.umd.edu [Astronomy Department, California Institute of Technology, 1200 East California Blvd., Pasadena, CA 91125 (United States); and others

    2014-10-20

    We present details of the CARMA Large Area Star Formation Survey (CLASSy), while focusing on observations of Barnard 1. CLASSy is a CARMA Key Project that spectrally imaged N{sub 2}H{sup +}, HCO{sup +}, and HCN (J = 1 → 0 transitions) across over 800 square arcminutes of the Perseus and Serpens Molecular Clouds. The observations have angular resolution near 7'' and spectral resolution near 0.16 km s{sup –1}. We imaged ∼150 square arcminutes of Barnard 1, focusing on the main core, and the B1 Ridge and clumps to its southwest. N{sub 2}H{sup +} shows the strongest emission, with morphology similar to cool dust in the region, while HCO{sup +} and HCN trace several molecular outflows from a collection of protostars in the main core. We identify a range of kinematic complexity, with N{sub 2}H{sup +} velocity dispersions ranging from ∼0.05 to 0.50 km s{sup –1} across the field. Simultaneous continuum mapping at 3 mm reveals six compact object detections, three of which are new detections. A new, non-binary dendrogram algorithm is used to analyze dense gas structures in the N{sub 2}H{sup +} position-position-velocity (PPV) cube. The projected sizes of dendrogram-identified structures range from about 0.01 to 0.34 pc. Size-linewidth relations using those structures show that non-thermal line-of-sight velocity dispersion varies weakly with projected size, while rms variation in the centroid velocity rises steeply with projected size. Comparing these relations, we propose that all dense gas structures in Barnard 1 have comparable depths into the sky, around 0.1-0.2 pc; this suggests that overdense, parsec-scale regions within molecular clouds are better described as flattened structures rather than spherical collections of gas. Science-ready PPV cubes for Barnard 1 molecular emission are available for download.

  2. The ACS LCID project : RR Lyrae stars as tracers of old population gradients in the isolated dwarf spheroidal galaxy tucana

    NARCIS (Netherlands)

    Bernard, Edouard J.; Gallart, Carme; Monelli, Matteo; Aparicio, Antonio; Cassisi, Santi; Skillman, Evan D.; Stetson, Peter B.; Cole, Andrew A.; Drozdovsky, Igor; Hidalgo, Sebastian L.; Mateo, Mario; Tolstoy, Eline

    2008-01-01

    We present a study of the radial distribution of RR Lyrae variables, which present a range of photometric and pulsational properties, in the dwarf spheroidal galaxy Tucana. We find that the fainter RR Lyrae stars, having a shorter period, are more centrally concentrated than the more luminous, longe

  3. THE ACS LCID PROJECT. I. SHORT-PERIOD VARIABLES IN THE ISOLATED DWARF SPHEROIDAL GALAXIES CETUS AND TUCANA

    NARCIS (Netherlands)

    Bernard, Edouard J.; Monelli, Matteo; Gallart, Carme; Drozdovsky, Igor; Stetson, Peter B.; Aparicio, Antonio; Cassisi, Santi; Mayer, Lucio; Cole, Andrew A.; Hidalgo, Sebastian L.; Skillman, Evan D.; Tolstoy, Eline

    2009-01-01

    We present the first study of the variable star populations in the isolated dwarf spheroidal galaxies (dSphs) Cetus and Tucana. Based on Hubble Space Telescope images obtained with the Advanced Camera for Surveys in the F475W and F814W bands, we identified 180 and 371 variables in Cetus and Tucana,

  4. The ACS LCID project : RR Lyrae stars as tracers of old population gradients in the isolated dwarf spheroidal galaxy tucana

    NARCIS (Netherlands)

    Bernard, Edouard J.; Gallart, Carme; Monelli, Matteo; Aparicio, Antonio; Cassisi, Santi; Skillman, Evan D.; Stetson, Peter B.; Cole, Andrew A.; Drozdovsky, Igor; Hidalgo, Sebastian L.; Mateo, Mario; Tolstoy, Eline

    2008-01-01

    We present a study of the radial distribution of RR Lyrae variables, which present a range of photometric and pulsational properties, in the dwarf spheroidal galaxy Tucana. We find that the fainter RR Lyrae stars, having a shorter period, are more centrally concentrated than the more luminous,

  5. LHS 2803B: A very wide mid-T dwarf companion to an old M dwarf identified from Pan-STARRS1

    CERN Document Server

    Deacon, Niall R; Magnier, Eugene A; Bowler, Brendan P; Mann, Andrew W; Redstone, Joshua A; Burgett, William S; Chambers, Ken C; Hodapp, Klaus W; Kaiser, Nick; Kudritzki, Rolf-Peter; Morgan, Jeff S; Price, Paul A; Tonry, John L; Wainscoat, Richard J

    2012-01-01

    We report the discovery of a wide (approximately 400 AU projected separation), common proper motion companion to the nearby M dwarf LHS 2803 (PSO J207.0300-13.7422). This object was discovered during our census of the local T dwarf population using Pan-STARRS1 and 2MASS data. Using IRTF/SpeX near-infrared spectroscopy, we classify the secondary to be spectral type T5.5. University of Hawai`i 2.2m/SNIFS optical spectroscopy indicates the primary has a spectral type of M4.5, with approximately solar metallicity and no measurable H_alpha emission. We use this lack of activity to set a lower age limit for the system of 3.5 Gyr. Using a comparison with chance alignments of brown dwarfs and nearby stars, we conclude that the two objects are unlikely to be a chance association. The primary's photometric distance of 21 pc and its proper motion implies thin disk kinematics. Based on these kinematics and its metallicity, we set an upper age limit for the system of 10 Gyr. Evolutionary model calculations suggest the sec...

  6. The BaLROG project - I. Quantifying the influence of bars on the kinematics of nearby galaxies

    CERN Document Server

    Seidel, M K; Martínez-Valpuesta, I; Díaz-García, S; Laurikainen, E; Salo, H; Knapen, J H

    2015-01-01

    We present the BaLROG (Bars in Low Redshift Optical Galaxies) sample of 16 morphologically distinct barred spirals to characterise observationally the influence of bars on nearby galaxies. Each galaxy is a mosaic of several pointings observed with the IFU spectrograph SAURON leading to a tenfold sharper spatial resolution (~100 pc) compared to ongoing IFU surveys. In this paper we focus on the kinematic properties. We calculate the bar strength Qb from classical torque analysis using 3.6 {\\mu}m Spitzer (S4G) images, but also develop a new method based solely on the kinematics. A correlation between the two measurements is found and backed up by N-body simulations, verifying the measurement of Qb . We find that bar strengths from ionised gas kinematics are ~2.5 larger than those measured from stellar kinematics and that stronger bars have enhanced influence on inner kinematic features. We detect that stellar angular momentum "dips" at 0.2$\\pm$0.1 bar lengths and half of our sample exhibits an anti-correlation ...

  7. Relativistic Kinematics

    CERN Document Server

    Sahoo, Raghunath

    2016-01-01

    This lecture note covers Relativistic Kinematics, which is very useful for the beginners in the field of high-energy physics. A very practical approach has been taken, which answers "why and how" of the kinematics useful for students working in the related areas.

  8. The ACS LCID project. IX. Imprints of the early universe in the radial variation of the star formation history of dwarf galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Hidalgo, Sebastian L.; Monelli, Matteo; Aparicio, Antonio; Gallart, Carme, E-mail: shidalgo@iac.es, E-mail: monelli@iac.es, E-mail: aparicio@iac.es, E-mail: carme@iac.es [Instituto de Astrofísica de Canarias, Vía Láctea s/n, E-38200 La Laguna, Tenerife, Canary Islands (Spain); and others

    2013-12-01

    Based on Hubble Space Telescope observations from the Local Cosmology from Isolated Dwarfs project, we present the star formation histories, as a function of galactocentric radius, of four isolated Local Group dwarf galaxies: two dSph galaxies, Cetus and Tucana, and two transition galaxies (dTrs), LGS-3 and Phoenix. The oldest stellar populations of the dSphs and dTrs are, within the uncertainties, coeval (∼13 Gyr) at all galactocentric radii. We find that there are no significative differences between the four galaxies in the fundamental properties (such as the normalized star formation rate or age-metallicity relation) of their outer regions (radii greater than four exponential scale lengths); at large radii, these galaxies consist exclusively of old (≳ 10.5 Gyr) metal-poor stars. The duration of star formation in the inner regions varies from galaxy to galaxy, and the extended central star formation in the dTrs produces the dichotomy between dSph and dTr galaxy types. The dTr galaxies show prominent radial stellar population gradients: The centers of these galaxies host young (≲ 1 Gyr) populations, while the age of the last formation event increases smoothly with increasing radius. This contrasts with the two dSph galaxies. Tucana shows a similar, but milder, gradient, but no gradient in age is detected Cetus. For the three galaxies with significant stellar population gradients, the exponential scale length decreases with time. These results are in agreement with outside-in scenarios of dwarf galaxy evolution, in which a quenching of the star formation toward the center occurs as the galaxy runs out of gas in the outskirts.

  9. Strangelet dwarfs

    CERN Document Server

    Alford, Mark G; Reddy, Sanjay

    2011-01-01

    If the surface tension of quark matter is low enough, quark matter is not self bound. At sufficiently low pressure and temperature, it will take the form of a crystal of positively charged strangelets in a neutralizing background of electrons. In this case there will exist, in addition to the usual family of strange stars, a family of low-mass large-radius objects analogous to white dwarfs, which we call "strangelet dwarfs". Using a generic parametrization of the equation of state of quark matter, we calculate the mass-radius relationship of these objects.

  10. The Carina Project. X. On the Kinematics of Old and Intermediate-age Stellar Populations1,2

    Science.gov (United States)

    Fabrizio, M.; Bono, G.; Nonino, M.; Łokas, E. L.; Ferraro, I.; Iannicola, G.; Buonanno, R.; Cassisi, S.; Coppola, G.; Dall’Ora, M.; Gilmozzi, R.; Marconi, M.; Monelli, M.; Romaniello, M.; Stetson, P. B.; Thévenin, F.; Walker, A. R.

    2016-10-01

    We present new radial velocity (RV) measurements of old (horizontal branch) and intermediate-age (red clump) stellar tracers in the Carina dwarf spheroidal. They are based on more than 2200 low-resolution spectra collected with VIMOS at Very Large Telescope (VLT). The targets are faint (20 ≲ V ≲ 21.5 mag), but the accuracy at the faintest limit is ≤9 km s‑1. These data were complemented with RV measurements either based on spectra collected with FORS2 and FLAMES/GIRAFFE at VLT or available in the literature. We ended up with a sample of 2748 stars and among them, 1389 are candidate Carina stars. We found that the intermediate-age stellar component shows a well-defined rotational pattern around the minor axis. The western and the eastern side of the galaxy differ by +5 and ‑4 km s‑1 when compared with the main RV peak. The old stellar component is characterized by a larger RV dispersion and does not show evidence of the RV pattern. We compared the observed RV distribution with N-body simulations for a former disky dwarf galaxy orbiting a giant Milky Way–like galaxy. We rotated the simulated galaxy by 60° with respect to the major axis, we kept the observer on the orbital plane of the dwarf and extracted a sample of stars similar to the observed one. Observed and predicted {V}{rot}/σ ratios across the central regions are in remarkable agreement. This evidence indicates that Carina was a disky dwarf galaxy that experienced several strong tidal interactions with the Milky Way. Owing to these interactions, Carina transformed from a disky to a prolate spheroid and the rotational velocity transformed into random motions.

  11. The ACS LCID project. IX. Imprints of the early Universe in the radial variation of the star formation history of dwarf galaxies

    CERN Document Server

    Hidalgo, Sebastian L; Aparicio, Antonio; Gallart, Carme; Skillman, Evan D; Cassisi, Santi; Bernard, Edouard J; Mayer, Lucio; Stetson, Peter; Cole, Andrew; Dolphin, Andrew

    2013-01-01

    Based on Hubble Space Telescope observations from the Local Cosmology from Isolated Dwarfs project, we present the star formation histories, as a function of galactocentric radius, of four isolated Local Group dwarf galaxies: two dSph galaxies, Cetus and Tucana, and two transition galaxies (dTrs), LGS-3 and Phoenix. The oldest stellar populations of the dSphs and dTrs are, within the uncertainties, coeval ($\\sim 13 Gyr$) at all galactocentric radii. We find that there are no significative differences between the four galaxies in the fundamental properties (such as the normalized star formation rate or age-metallicity relation) of their outer regions (radii greater than four exponential scale lengths); at large radii, these galaxies consist exclusively of old ($\\geq 10.5 Gyr$) metal-poor stars. The duration of star formation in the inner regions vary from galaxy to galaxy, and the extended central star formation in the dTrs produces the dichotomy between dSph and dTr galaxy types. The dTr galaxies show promine...

  12. The ACS LCID Project: RR Lyrae stars as tracers of old population gradients in the isolated dwarf spheroidal galaxy Tucana

    CERN Document Server

    Bernard, Edouard J; Monelli, Matteo; Aparicio, Antonio; Cassisi, Santi; Skillman, Evan D; Stetson, Peter B; Cole, Andrew A; Drozdovsky, Igor; Hidalgo, Sebastian L; Mateo, Mario; Tolstoy, Eline

    2008-01-01

    We present a study of the radial distribution of RR Lyrae variables, which present a range of photometric and pulsational properties, in the dwarf spheroidal galaxy Tucana. We find that the fainter RR Lyrae stars, having a shorter period, are more centrally concentrated than the more luminous, longer period RR Lyrae variables. Through comparison with the predictions of theoretical models of stellar evolution and stellar pulsation, we interpret the fainter RR Lyrae stars as a more metal-rich subsample. In addition, we show that they must be older than about 10 Gyr. Therefore, the metallicity gradient must have appeared very early on in the history of this galaxy.

  13. When the Jeans don't fit: How stellar feedback drives stellar kinematics and complicates dynamical modeling in low-mass galaxies

    CERN Document Server

    El-Badry, Kareem; Geha, Marla; Quataert, Eliot; Hopkins, Philip F; Kereš, Dusan; Chan, T K; Faucher-Giguère, Claude-André

    2016-01-01

    In low-mass galaxies, stellar feedback can drive gas outflows that generate non-equilibrium fluctuations in the gravitational potential. Using cosmological zoom-in baryonic simulations from the Feedback in Realistic Environments (FIRE) project, we investigate how these fluctuations affect stellar kinematics and the reliability of Jeans dynamical modeling in low-mass galaxies. We find that stellar velocity dispersion and anisotropy profiles fluctuate significantly over the course of galaxies' starburst cycles. We therefore predict an observable correlation between star formation rate and stellar kinematics: dwarf galaxies with higher recent star formation rates should have systemically higher stellar velocity dispersions. This prediction provides an observational test of the role of stellar feedback in regulating both stellar and dark-matter densities in dwarf galaxies. We find that Jeans modeling, which treats galaxies as virialized systems in dynamical equilibrium, overestimates a galaxy's dynamical mass dur...

  14. White dwarf-red dwarf binaries in the Galaxy

    NARCIS (Netherlands)

    Besselaar, E.J.M. van den

    2007-01-01

    This PhD thesis shows several studies on white dwarf - red dwarf binaries. White dwarfs are the end products of most stars and red dwarfs are normal hydrogen burning low-mass stars. White dwarf - red dwarf binaries are both blue (white dwarf) and red (red dwarf). Together with the fact that they are

  15. The Stellar and Gas Kinematics of NGC 1569

    Science.gov (United States)

    Jackson, Megan C.; Hunter, D. A.

    2009-01-01

    The intrinsic shape of dwarf irregular (dIm) galaxies remains controversial. Projected minor-to-major axis ratios provide insufficient data to determine the shapes of dIm galaxies. However, the stellar velocity dispersion coupled with the maximum rotational velocity derived from HI observations gives a measure of how kinematically hot a system is, and, therefore, indicates its structure. We present, for the first time, the stellar kinematics of NGC 1569 obtained using the KPNO 4-m+Echelle spectrograph. These data are combined with the HI rotation velocity obtained from VLA observations acquired by the THINGS group. NGC 1569 is the first of four dIm galaxies for which optical spectroscopic observations have been completed. The PI's dissertation thesis project will be based on the completion of observations obtained using the KPNO 4-m+Echelle spectrograph for a total sample of 4 dIm galaxies, including NGC 1569. We would like to thank the NSF for the funding necessary for the VLA observations as well as the Lowell Observatory Pre-doctoral Program which has made it possible for the PI to complete her Ph. D. thesis project.

  16. Kinematical Quantization

    CERN Document Server

    Anderson, Edward

    2016-01-01

    We consider here kinematical quantization: a first and often overlooked step in quantization procedures. $\\mathbb{R}$, $\\mathbb{R}_+$ and the interval are considered, as well as direct (Cartesian) products thereof. Some simple minisuperspace models, and mode by mode consideration of slightly inhomogeneous cosmology, have indefinite signature versions of such kinematical quantizations. The examples in the current paper build in particular toward the case of vacuum $\\mathbb{S}^3$ slightly inhomogeneous cosmology's mode configuration space, which is mathematically a finite time interval slab of Minkowski spacetime.

  17. The ATLAS3D project - XVII. Linking photometric and kinematic signatures of stellar discs in early-type galaxies

    CERN Document Server

    Krajnovic, Davor; Blitz, Leo; Bois, Maxime; Bournaud, Frederic; Bureau, Martin; Cappellari, Michele; Davies, Roger L; Davis, Timothy A; de Zeeuw, P T; Emsellem, Eric; Khochfar, Sadegh; Kuntschner, Harald; McDermid, Richard M; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M

    2012-01-01

    [Abridged] We analyse the morphological structures in galaxies of the ATLAS3D sample by fitting a single Sersic profile and decomposing all non-barred objects (180 of 260 objects) in two components parameterised by an exponential and a general Sersic function. The aim of this analysis is to look for signatures of discs in light distributions of nearby early-type galaxies and compare them to kinematic properties. Using Sersic index from single component fits for a distinction between slow and fast rotators, or even late- and early-type galaxies, is not recommended. Assuming that objects with n>3 are slow rotators (or ellipticals), there is only a 22 per cent probability to correctly classify objects as slow rotators (or 37 per cent of previously classified as ellipticals). We show that exponential sub-components, as well as light profiles fitted with only a single component of a low Sersic index, can be linked with the kinematic evidence for discs in early-type galaxies. The median disk-to-total light ratio fo...

  18. SMC in space and time: a project to study the evolution of the prototype interacting late-type dwarf galaxy

    CERN Document Server

    Tosi, M; Sabbi, E; Glatt, K; Grebel, E K; Christian, C; Cignoni, M; Clementini, G; Cole, A; Da Costa, G; Harbeck, D; Marconi, M; Meixner, M; Nota, A; Sirianni, M; Smecker-Hane, T

    2008-01-01

    We introduce the SMC in space and time, a large coordinated space and ground-based program to study star formation processes and history, as well as variable stars, structure, kinematics and chemical evolution of the whole SMC. Here, we present the Colour-Magnitude Diagrams(CMDs) resulting from HST/ACS photometry, aimed at deriving the star formation history (SFH) in six fields of the SMC. The fields are located in the central regions, in the stellar halo, and in the wing toward the LMC. The CMDs are very deep, well beyond the oldest Main Sequence Turn-Off, and will allow us to derive the SFH over the entire Hubble time.

  19. Rational kinematics

    CERN Document Server

    Angeles, Jorge

    1988-01-01

    A rational study of kinematics is a treatment of the subject based on invariants, i.e., quantities that remain essentially unchanged under a change of observer. An observer is understood to be a reference frame supplied with a clock (Truesdell 1966). This study will therefore include an introduction to invariants. The language of these is tensor analysis and multilinear algebra, both of which share many isomorphic relations, These subjects are treated in full detail in Ericksen (1960) and Bowen and Wang (1976), and hence will not be included here. Only a short account of notation and definitions will be presented. Moreover, definitions and basic concepts pertaining to the kinematics of rigid bodies will be also included. Although the kinematics of rigid bodies can be regarded as a particular case of the kinematics of continua, the former deserves attention on its own merits for several reasons. One of these is that it describes locally the motions undergone by continua. Another reason is that a whole area of ...

  20. The structure of Andromeda II dwarf spheroidal galaxy

    CERN Document Server

    del Pino, Andrés; Hidalgo, Sebastian L; Fouquet, Sylvain

    2016-01-01

    We analyze in detail the spatial distribution and kinematic properties of two different stellar populations in Andromeda II (And II) dwarf spheroidal galaxy. We obtained their detailed surface density maps, together with their radial density profiles. The two populations differ not only in age and metallicity, but also in their spatial distribution and kinematics. Old stars ($\\gtrsim 11$ Gyr) follow a round distribution well fitted by truncated density profiles. These stars rotate around the projected optical major axis of the galaxy with line-of-sight velocities $v_{los}(r_h) = 16 \\pm 3$ km s$^{-1}$ and a velocity gradient of $2.06 \\pm 0.21$ km s$^{-1}$ arcmin$^{-1}$. Intermediate-age stars ($\\lesssim 9$ Gyr) concentrate in the centre of the galaxy and form an elongated structure extending along the projected optical major axis. This structure appears to rotate with a steeper velocity gradient, $2.24 \\pm 0.22$ km s$^{-1}$ arcmin$^{-1}$, and around the optical minor axis. The centres of rotation and kinetic p...

  1. Naming Disney's Dwarfs.

    Science.gov (United States)

    Sidwell, Robert T.

    1980-01-01

    Discusses Disney's version of the folkloric dwarfs in his production of "Snow White" and weighs the Disney rendition of the dwarf figure against the corpus of traits and behaviors pertaining to dwarfs in traditional folklore. Concludes that Disney's dwarfs are "anthropologically true." (HOD)

  2. Brown Dwarf Companions to White Dwarfs

    CERN Document Server

    Burleigh, M R; Dobbie, P D; Farihi, J; Napiwotzki, R; Maxted, P F L; Barstow, M A; Jameson, R F; Casewell, S L; Gänsicke, B T; Marsh, T R

    2011-01-01

    Brown dwarf companions to white dwarfs are rare, but recent infra-red surveys are slowly reveal- ing examples. We present new observations of the post-common envelope binary WD0137-349, which reveals the effects of irradiation on the ~ 0.05M* secondary, and new observations of GD 1400 which show that it too is a close, post-comon envelope system. We also present the lat- est results in a near-infrared photometric search for unresolved ultracool companions and to white dwarfs with UKIDSS. Twenty five DA white dwarfs were identified as having photometric excesses indicative of a low mass companion, with 8-10 of these having a predicted mass in the range asso- ciated with brown dwarfs. The results of this survey show that the unresolved (< 2") brown dwarf companion fraction to DA white dwarfs is 0.3 \\leq fWD+BD \\leq 1.3%.

  3. How chameleons core dwarfs with cusps

    CERN Document Server

    Lombriser, Lucas

    2014-01-01

    The presence of a scalar field that couples nonminimally and universally to matter can enhance gravitational forces on cosmological scales while restoring general relativity in the Solar neighborhood. In the intermediate regime, kinematically inferred masses experience an additional radial dependence with respect to the underlying distribution of matter, which is caused by the increment of gravitational forces with increasing distance from the Milky Way center. The same effect can influence the internal kinematics of subhalos and cause cuspy matter distributions to appear core-like. Specializing to the chameleon model as a worked example, we demonstrate this effect by tracing the scalar field from the outskirts of the Milky Way halo to its interior, simultaneously fitting observed velocity dispersions of chemo-dynamically discriminated red giant populations in the Fornax and Sculptor dwarf spheroidals. Whereas in standard gravity these observations suggest that the matter distribution of the dwarfs is cored, ...

  4. New Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main Sequence

    Science.gov (United States)

    Gizis, John E.; Monet, David G.; Reid, I. Neill; Kirkpatrick, J. Davy; Liebert, James; Williams, Rik J.

    2000-08-01

    We have combined 2MASS and POSS II data in a search for nearby ultracool (later than M6.5) dwarfs with Ksmass function that is smooth across the stellar/substellar limit. We show the observed frequency of Hα emission peaks at ~100% for M7 dwarfs and then decreases for cooler dwarfs. In absolute terms, however, as measured by the ratio of Hα to bolometric luminosity, none of the ultracool M dwarfs can be considered very active compared to earlier M dwarfs, and we show that the decrease that begins at spectral type M6 continues to the latest L dwarfs. We find that flaring is common among the coolest M dwarfs and estimate the frequency of flares at 7% or higher. We show that the kinematics of relatively active (EW>6 Å) ultracool M dwarfs are consistent with an ordinary old disk stellar population, while the kinematics of inactive ultracool M dwarfs are more typical of a 0.5 Gyr old population. The early L dwarfs in the sample have kinematics consistent with old ages, suggesting that the hydrogen-burning limit is near spectral types L2-L4. We use the available data on M and L dwarfs to show that chromospheric activity drops with decreasing mass and temperature and that at a given (M8 or later) spectral type, the younger field (brown) dwarfs are less active than many of the older, more massive field stellar dwarfs. Thus, contrary to the well-known stellar age-activity relationship, low activity in field ultracool dwarfs can be an indication of comparative youth and substellar mass.

  5. Youth Indicators of Late-M Dwarfs

    Science.gov (United States)

    Feldman, Daniel; Cruz, K.; Lépine, S.; Alpert, N.

    2011-01-01

    We present a study in which we searched for a correlation between weak Na absorption doublet (8183Å, 8194Å) and strong H-Alpha emission (6563Å) in late-M dwarf stars (M6-M9), as both are indicative of youth. Our sample consists of late-M Dwarfs from the LSPM Survey (Lépine and Shara, 2005), which contain stars with measured proper motions of mu > 40 mas/yr. Measurements for emission and absorption strength were made using spectral indices. Our preliminary results are presented; future work will include a similar analysis of early type M Dwarfs, as well as kinematics. This work was funded by the CUNY Summer Undergraduate Research Program, as well as the CUNY Macaulay Honors College, and we acknowledge the hospitality of the American Museum of Natural History.

  6. The Atlas3D project - XIV. The extent and kinematics of molecular gas in early-type galaxies

    CERN Document Server

    Davis, Timothy A; Bureau, Martin; Cappellari, Michele; Scott, Nicholas; Young, Lisa M; Blitz, Leo; Crocker, Alison F; Bayet, Estelle; Bois, Maxime; Bournaud, Frédéric; Davies, Roger L; de Zeeuw, P Tim; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; Lablanche, Pierre-Yves; McDermid, Richard M; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Serra, Paolo; Weijmans, Anne-Marie

    2012-01-01

    We use interferometric CO observations to compare the extent, surface brightness profiles and kinematics of the molecular gas in CO-rich Atlas3D early-type galaxies (ETGs) and spiral galaxies. We find that the molecular gas extent is smaller in absolute terms in ETGs than in late-type galaxies, but that the size distributions are similar once scaled by the galaxies optical/stellar characteristic scale-lengths. Virgo cluster ETGs have less extended molecular gas reservoirs than field counterparts. Approximately half of ETGs have molecular gas surface brightness profiles that follow the stellar light profile. These systems often have relaxed gas out to large radii, suggesting they are unlikely to have had recent merger/accretion events. A third of the sample galaxies show molecular gas surface brightness profiles that fall off slower than the light, and sometimes show a truncation. We suggest that ram pressure stripping and/or the presence of hot gas has compressed/truncated the gas in these systems. The remain...

  7. A kinetic and Kinematic analysis in two assessment situation with bench press. Free Weight vs Smith Machine. Project pilot.

    Directory of Open Access Journals (Sweden)

    I. J. Bautista

    2012-06-01

    Full Text Available This pilot study examines the most relevant kinetic and kinematics variables in two bench press exercises; Smith Machine (PMS vs. free weights (PBL. Two trained subjects participated in the research following informed consent. To determine the maximum load (1-RM, two incremental protocols were used for PMS and PBL. Subject 1 (S-1 produced force values of 770N and 837N, peak force of 28ms and 12ms, in PBL and PMS respectively. Values for subject 2 (S-2 were 693N and 849N, PMF of 60ms and 66ms for PBL and PMS respectively. Detailed analyses of the following variables were performed; velocity curves for each load, the “sticking period”, the distances of grip width, and changes in bar inclination during the ascent phase of the lift were examined. The key findings of this research, and the basis for future research demonstrate that PBL is recommended as a training exercise, while more reliable information regarding force variables can be attained through using PMS in measurement sessions. Key Words: Bench Press, smith machine, free weight, strength assessment, upper limb.

  8. The M4 Core Project with HST - IV. Internal Kinematics from Accurate Radial Velocities of 2771 Cluster Members

    CERN Document Server

    Malavolta, L; Bedin, L R; Sneden, C; Nascimbeni, V; Sommariva, V

    2015-01-01

    We present a detailed study of the internal kinematics of the Galactic Globular Cluster M 4 (NGC 6121), by deriving the radial velocities from 7250 spectra for 2771 stars distributed from the upper part of the Red Giant Branch down to the Main Sequence. We describe new approaches to determine the wavelength solution from day-time calibrations and to determine the radial velocity drifts that can occur between calibration and science observations when observing with the GIRAFFE spectrograph at VLT. Two techniques to determine the radial velocity are compared, after a qualitative description of their advantages with respect to other commonly used algorithm, and a new approach to remove the sky contribution from the spectra obtained with fibre-fed spectrograph and further improve the radial velocity precision is presented. The average radial velocity of the cluster is $\\langle v \\rangle = 71.08 \\pm 0.08$ km s$^{-1}$ with an average dispersion of $\\mu_{v_c} = 3.97$ km s$^{-1}$. Using the same dataset and the same ...

  9. The EBLM project. I. Physical and orbital parameters, including spin-orbit angles, of two low-mass eclipsing binaries on opposite sides of the brown dwarf limit

    Science.gov (United States)

    Triaud, A. H. M. J.; Hebb, L.; Anderson, D. R.; Cargile, P.; Collier Cameron, A.; Doyle, A. P.; Faedi, F.; Gillon, M.; Gomez Maqueo Chew, Y.; Hellier, C.; Jehin, E.; Maxted, P.; Naef, D.; Pepe, F.; Pollacco, D.; Queloz, D.; Ségransan, D.; Smalley, B.; Stassun, K.; Udry, S.; West, R. G.

    2013-01-01

    This paper introduces a series of papers aiming to study the dozens of low-mass eclipsing binaries (EBLM), with F, G, K primaries, that have been discovered in the course of the WASP survey. Our objects are mostly single-line binaries whose eclipses have been detected by WASP and were initially followed up as potential planetary transit candidates. These have bright primaries, which facilitates spectroscopic observations during transit and allows the study of the spin-orbit distribution of F, G, K+M eclipsing binaries through the Rossiter-McLaughlin effect. Here we report on the spin-orbit angle of WASP-30b, a transiting brown dwarf, and improve its orbital parameters. We also present the mass, radius, spin-orbit angle and orbital parameters of a new eclipsing binary, J1219-39b (1SWAPJ121921.03-395125.6, TYC 7760-484-1), which, with a mass of 95 ± 2 Mjup, is close to the limit between brown dwarfs and stars. We find that both objects have projected spin-orbit angles aligned with their primaries' rotation. Neither primaries are synchronous. J1219-39b has a modestly eccentric orbit and is in agreement with the theoretical mass-radius relationship, whereas WASP-30b lies above it. Using WASP-South photometric observations (Sutherland, South Africa) confirmed with radial velocity measurement from the CORALIE spectrograph, photometry from the EulerCam camera (both mounted on the Swiss 1.2 m Euler Telescope), radial velocities from the HARPS spectrograph on the ESO's 3.6 m Telescope (prog ID 085.C-0393), and photometry from the robotic 60 cm TRAPPIST telescope, all located at ESO, La Silla, Chile. The data is publicly available at the CDS Strasbourg and on demand to the main author.Tables A.1-A.3 are available in electronic form at http://www.aanda.orgPhotometry tables are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/549/A18

  10. Atmospheres of Brown Dwarfs

    CERN Document Server

    Helling, Christiane

    2014-01-01

    Brown Dwarfs are the coolest class of stellar objects known to date. Our present perception is that Brown Dwarfs follow the principles of star formation, and that Brown Dwarfs share many characteristics with planets. Being the darkest and lowest mass stars known makes Brown Dwarfs also the coolest stars known. This has profound implication for their spectral fingerprints. Brown Dwarfs cover a range of effective temperatures which cause brown dwarfs atmospheres to be a sequence that gradually changes from a M-dwarf-like spectrum into a planet-like spectrum. This further implies that below an effective temperature of < 2800K, clouds form already in atmospheres of objects marking the boundary between M-Dwarfs and brown dwarfs. Recent developments have sparked the interest in plasma processes in such very cool atmospheres: sporadic and quiescent radio emission has been observed in combination with decaying Xray-activity indicators across the fully convective boundary.

  11. LHS 2803B: A VERY WIDE MID-T DWARF COMPANION TO AN OLD M DWARF IDENTIFIED FROM PAN-STARRS1

    Energy Technology Data Exchange (ETDEWEB)

    Deacon, Niall R. [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Liu, Michael C.; Magnier, Eugene A.; Bowler, Brendan P.; Mann, Andrew W.; Burgett, William S.; Chambers, Ken C.; Kaiser, Nick; Kudritzki, Rolf-Peter; Morgan, Jeff S.; Tonry, John L.; Wainscoat, Richard J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Redstone, Joshua A. [Facebook, 1601 Willow Road, Menlo Park, CA 94025 (United States); Hodapp, Klaus W. [Institute for Astronomy, University of Hawaii, 640 North Aohoku Place, Hilo, HI 96720 (United States); Price, Paul A., E-mail: deacon@mpia.de [Princeton University Observatory, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States)

    2012-09-20

    We report the discovery of a wide ({approx}1400 AU projected separation), common proper motion companion to the nearby M dwarf LHS 2803 (PSO J207.0300-13.7422). This object was discovered during our census of the local T dwarf population using Pan-STARRS1 and Two Micron All Sky Survey data. Using the Infrared Telescope Facility/SpeX near-infrared spectroscopy, we classify the secondary to be spectral type T5.5. University of Hawaii 2.2 m/SuperNova Integral Field Spectrograph optical spectroscopy indicates that the primary has a spectral type of M4.5, with approximately solar metallicity and no measurable H{alpha} emission. We use this lack of activity to set a lower age limit for the system of 3.5 Gyr. Using a comparison with chance alignments of brown dwarfs and nearby stars, we conclude that the two objects are unlikely to be a chance association. The primary's photometric distance of 21 pc and its proper motion implies thin disk kinematics. Based on these kinematics and its metallicity, we set an upper age limit for the system of 10 Gyr. Evolutionary model calculations suggest that the secondary has a mass of 72{+-}{sup 4}{sub 7} M{sub Jup}, temperature of 1120 {+-} 80 K, and log g = 5.4 {+-} 0.1 dex. Model atmosphere fitting to the near-IR spectrum gives similar physical parameters of 1100 K and log g = 5.0.

  12. Drivers of Turbulence in the Neutral Interstellar Medium of Dwarf Galaxies

    Science.gov (United States)

    Stilp, Adrienne M.

    The cause of HI velocity dispersions in the interstellar medium (ISM) of galaxies is often attributed to star formation, but recent evidence has shown these two quantities are not connected in regions of low star formation. This lack of connection is most apparent in dwarf galaxies and the outer disks of spiral galaxies. However, unique data sets have recently been collected that can help address this discrepancy. The ACS Nearby Survey Treasury Project (ANGST) has measured time-resolved star formation histories (SFHs) in ˜ 70 nearby galaxies. The followup Very Large Array-ANGST survey (VLA-ANGST) provides complementary HI observations of a subset of ANGST galaxies. In this thesis, I explore the connection between star formation and HI kinematics in a number of nearby dwarf galaxies. I first present the Very Large Array-ACS Nearby Galaxy Survey Treasury Project (ANGST). VLA-ANGST was designed to provide high spatial and velocity resolution observations of the HI component of the interstellar medium (ISM) in ANGST galaxies. I describe the data calibration and imaging procedures, and then present the publicly-available data products. The observations from this survey and from The HI Nearby Galaxy Survey (THINGS) comprise the majority of data in my thesis. Using VLA-ANGST and THINGS data, I present a method to measure the average HI kinematics in a number of nearby dwarf galaxies by co-adding individual line-of-sight profiles. These "superprofiles" are composed of a central narrow peak (˜ 6-10 km s-1) with higher velocity wings to either side. When scaled to the same half-width half-maximum, the shapes of the superprofiles are very similar. I interpret the central peak as representative of the average turbulent motion; the wings are then due to HI moving faster than expected compared to the average kinematics. I then compare the superprofile parameters to physical properties such as mass surface density and star formation intensity. The average velocity dispersion

  13. Study of the Sextans dwarf spheroidal galaxy from the DART CaII triplet survey

    CERN Document Server

    Battaglia, G; Helmi, A; Irwin, M; Parisi, P; Hill, V; Jablonka, P

    2010-01-01

    We use VLT/FLAMES intermediate resolution (R~6500) spectra of individual red giant branch stars in the near-infrared CaII triplet (CaT) region to investigate the wide-area metallicity properties and internal kinematics of the Sextans dwarf spheroidal galaxy (dSph). Our final sample consists of 174 probable members of Sextans with accurate line-of-sight velocities (+- 2 km/s) and CaT [Fe/H] measurements (+- 0.2 dex). We use the MgI line at 8806.8 \\AA\\, as an empirical discriminator for distinguishing between probable members of the dSph (giant stars) and probable Galactic contaminants (dwarf stars). Sextans shows a similar chemo-dynamical behaviour to other Milky Way dSphs, with its central regions being more metal rich than the outer parts and with the more metal-rich stars displaying colder kinematics than the more metal-poor stars. Hints of a velocity gradient are found along the projected major axis and along an axis at P.A.=191 deg, however a larger and more spatially extended sample may be necessary to p...

  14. The ATLAS(3D) project : II. Morphologies, kinemetric features and alignment between photometric and kinematic axes of early-type galaxies

    NARCIS (Netherlands)

    Krajnovic, Davor; Emsellem, Eric; Cappellari, Michele; Alatalo, Katherine; Blitz, Leo; Bois, Maxime; Bournaud, Frederic; Bureau, Martin; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Khochfar, Sadegh; Kuntschner, Harald; Lablanche, Pierre-Yves; McDermid, Richard M.; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

    2011-01-01

    We use the ATLAS(3D) sample of 260 early-type galaxies to study the apparent kinematic misalignment angle, Psi, defined as the angle between the photometric and kinematic major axes. We find that 71 per cent of nearby early-type galaxies are strictly aligned systems (Psi

  15. Binaries discovered by the SPY project I. HE 1047-0436 a subdwarf B + white dwarf system

    CERN Document Server

    Napiwotzki, R; Heber, U; Karl, C; Drechsel, H; Pauli, E M; Christlieb, N

    2001-01-01

    In the course of our search for double degenerate binaries as potential progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT (ESO SN Ia Progenitor surveY - SPY) we discovered that the sdB star HE 1047-0436 is radial velocity variable. The orbital period of 1.213253d, a semi-amplitude of 94km/s, and a minimum mass of the invisible companion of 0.44Msol are derived from the analysis of the radial velocity curve. We use an upper limit on the projected rotational velocity of the sdB star to constrain the system inclination and the companion mass to M>0.71Msol, bringing the total mass of the system closer to the Chandrasekhar limit. However, the system will merge due to loss of angular momentum via gravitational wave radiation only after several Hubble times. Atmospheric parameters and metal abundances are also derived. The resulting values are typical for sdB stars.

  16. The Kinematic Sunyaev-Zel'dovich Effect with Projected Fields: A Novel Probe of the Baryon Distribution with Planck, WMAP, and WISE Data

    CERN Document Server

    Hill, J Colin; Battaglia, Nick; Liu, Jia; Spergel, David N

    2016-01-01

    The kinematic Sunyaev-Zel'dovich (kSZ) effect - the Doppler boosting of cosmic microwave background (CMB) photons due to Compton-scattering off free electrons with non-zero bulk velocity - is an ideal tool to probe the abundance and distribution of baryons in the Universe. All kSZ measurements to date have explicitly required spectroscopic redshifts. Here, we implement a novel estimator for the kSZ - large-scale structure cross-correlation based on projected fields: it does not require redshift estimates for individual objects, allowing kSZ measurements from large-scale imaging surveys for the first time. We apply this estimator to cleaned CMB temperature maps constructed from Planck and Wilkinson Microwave Anisotropy Probe data and a galaxy sample from the Wide-field Infrared Survey Explorer (WISE). We measure the kSZ effect at 3.8-4.5$\\sigma$ significance, depending on the use of additional WISE galaxy bias constraints. We verify that our measurements are robust to possible dust emission from the WISE galax...

  17. Finite rotation and nonlinear beam kinematics

    Science.gov (United States)

    Hodges, Dewey H.

    1987-01-01

    Standard means of representing finite rotation in rigid-body kinematics, including orientation angles, Euler parameters, and Rodrigues parameters, are reviewed and compared. General kinematical relations for a beam theory that treats arbitrarily large rotation are then presented. The standard methods of representing finite rotations are applied to these kinematical expressions, and comparison is made among the standard methods and additional methods found in the literature, such as quasi-coordinates and linear combinations of projection angles. The method of Rodrigues parameters is shown to stand out for both its simplicity and generality when applied to beam kinematics, a result that is really missing from the literature.

  18. Giant Broad Line Regions in Dwarf Seyferts

    Indian Academy of Sciences (India)

    Nick Devereux

    2015-12-01

    High angular resolution spectroscopy obtained with the Hubble Space Telescope (HST) has revealed a remarkable population of galaxies hosting dwarf Seyfert nuclei with an unusually large broad-line region (BLR). These objects are remarkable for two reasons. Firstly, the size of the BLR can, in some cases, rival those seen in the most luminous quasars. Secondly, the size of the BLR is not correlated with the central continuum luminosity, an observation that distinguishes them from their reverberating counterparts. Collectively, these early results suggest that non-reverberating dwarf Seyferts are a heterogeneous group, and not simply scaled versions of each other. Careful inspection reveals broad H Balmer emission lines with single peaks, double peaks, and a combination of the two, suggesting that the broad emission lines are produced in kinematically distinct regions centered on the black hole (BH). Because the gravitational field strength is already known for these objects, by virtue of knowing their BH mass, the relationship between velocity and radius may be established, given a kinematic model for the BLR gas. In this way, one can determine the inner and outer radii of the BLRs by modeling the shape of their broad emission line profiles. In the present contribution, high quality spectra obtained with the Space Telescope Imaging Spectrograph (STIS) are used to constrain the size of the BLR in the dwarf Seyfert nuclei of M81, NGC 3998, NGC 4203, NGC 3227, NGC 4051 and NGC 3516.

  19. The DART Imaging And CaT Survey of the Fornax Dwarf Spheroidal Galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Battaglia, Giuseppina; Tolstoy, E.; Helmi, A.; /Kapteyn Astron. Inst., Groningen; Irwin, M.J.; /Cambridge U., Inst. of Astron.; Letarte, B.; /Kapteyn Astron. Inst.,; Jablonka, P.; /LASTRO Observ.; Hill, V.; /Meudon Observ.; Venn, K.A.; /Victoria U.; Shetrone, M.D.; /Texas U., McDonald Observ.; Arimoto, N.; /Tokyo, Astron. Observ.; Primas,; /European Southern Observ.; Kaufer, A.; /European Southern Obs., Chile; Francois, P.; /Meudon Observ.; Szeifert, T.; /European Southern Obs., Chile; Abel, T.; /KIPAC, Menlo Park; Sadakane, K.; /Osaka Kyoiku U.

    2006-08-28

    As part of the DART project we have used the ESO/2.2m Wide Field Imager in conjunction with the VLT/FLAMES* GIRAFFE spectrograph to study the detailed properties of the resolved stellar population of the Fornax dwarf spheroidal galaxy out to and beyond its tidal radius. Fornax dSph has had a complicated evolution and contains significant numbers of young, intermediate age and old stars. We investigate the relation between these different components by studying their photometric, kinematic and abundance distributions. We re-derived the structural parameters of the Fornax dwarf spheroidal using our wide field imaging covering the galaxy out to its tidal radius, and analyzed the spatial distribution of the Fornax stars of different ages as selected from Colour-Magnitude Diagram analysis. We have obtained accurate velocities and metallicities from spectra in the Ca II triplet wavelength region for 562 Red Giant Branch stars which have velocities consistent with membership in Fornax dwarf spheroidal. We have found evidence for the presence of at least three distinct stellar components: a young population (few 100 Myr old) concentrated in the center of the galaxy, visible as a Main Sequence in the Colour-Magnitude Diagram; an intermediate age population (2-8 Gyr old); and an ancient population (> 10Gyr), which are distinguishable from each other kinematically, from the metallicity distribution and in the spatial distribution of stars found in the Colour-Magnitude Diagram. From our spectroscopic analysis we find that the ''metal rich'' stars ([Fe/H] > -1.3) show a less extended and more concentrated spatial distribution, and display a colder kinematics than the ''metal poor'' stars ([Fe/H] < -1.3). There is tentative evidence that the ancient stellar population in the center of Fornax does not exhibit equilibrium kinematics. This could be a sign of a relatively recent accretion of external material, such as the merger of another

  20. 21st Century Kinematics : The 2012 NSF Workshop

    CERN Document Server

    2013-01-01

    21st Century Kinematics focuses on algebraic problems in the analysis and synthesis of mechanisms and robots, compliant mechanisms, cable-driven systems and protein kinematics. The specialist contributors provide the background for a series of presentations at the 2012 NSF Workshop. The text shows how the analysis and design of innovative mechanical systems yield increasingly complex systems of polynomials, characteristic of those systems. In doing so, takes advantage of increasingly sophisticated computational tools developed for numerical algebraic geometry and demonstrates the now routine derivation of polynomial systems dwarfing the landmark problems of even the recent past. The 21st Century Kinematics workshop echoes the NSF-supported 1963 Yale Mechanisms Teachers Conference that taught a generation of university educators the fundamental principles of kinematic theory. As such these proceedings will be provide admirable supporting theory for a graduate course in modern kinematics and should be of consid...

  1. The Cold Gas Content of Bulgeless Dwarf Galaxies

    CERN Document Server

    Pilkington, K; Calura, F; Brooks, A M; Mayer, L; Brook, C B; Stinson, G S; Thacker, R J; Few, C G; Cunnama, D; Wadsley, J

    2011-01-01

    We present an analysis of the neutral hydrogen (HI) properties of a fully cosmological hydrodynamical dwarf galaxy, run with varying simulation parameters. As reported by Governato et al. (2010), the high resolution, high star formation density threshold version of this galaxy is the first simulation to result in the successful reproduction of a (dwarf) spiral galaxy without any associated stellar bulge. We have set out to compare in detail the HI distribution and kinematics of this simulated bulgeless disk with what is observed in a sample of nearby dwarfs. To do so, we extracted the radial gas density profiles, velocity dispersion (e.g., velocity ellipsoid, turbulence), and the power spectrum of structure within the cold interstellar medium from the simulations. The highest resolution dwarf, when using a high density star formation threshold comparable to densities of giant molecular clouds, possesses bulk characteristics consistent with those observed in nature, though the cold gas is not as radially exten...

  2. Construction and compression of Dwarf

    Institute of Scientific and Technical Information of China (English)

    XIANG Long-gang; FENG Yu-cai; GUI Hao

    2005-01-01

    There exists an inherent difficulty in the original algorithm for the construction of Dwarf, which prevents it from constructing true Dwarfs. We explained when and why it introduces suffix redundancies into the Dwarf structure. To solve this problem, we proposed a completely new algorithm called PID. It bottom-up computes partitions of a fact table, and inserts them into the Dwarf structure. Ifa partition is an MSV partition, coalesce its sub-Dwarf; otherwise create necessary nodes and cells. Our performance study showed that PID is efficient. For further condensing of Dwarf, we proposed Condensed Dwarf, a more compressed structure, combining the strength of Dwarf and Condensed Cube. By eliminating unnecessary stores of "ALL" cells from the Dwarf structure, Condensed Dwarf could effectively reduce the size of Dwarf, especially for Dwarfs of the real world, which was illustrated by our experiments. Its query processing is still simple and, only two minor modifications to PID are required for the construction of Condensed Dwarf.

  3. Parallel kinematics type, kinematics, and optimal design

    CERN Document Server

    Liu, Xin-Jun

    2014-01-01

    Parallel Kinematics- Type, Kinematics, and Optimal Design presents the results of 15 year's research on parallel mechanisms and parallel kinematics machines. This book covers the systematic classification of parallel mechanisms (PMs) as well as providing a large number of mechanical architectures of PMs available for use in practical applications. It focuses on the kinematic design of parallel robots. One successful application of parallel mechanisms in the field of machine tools, which is also called parallel kinematics machines, has been the emerging trend in advanced machine tools. The book describes not only the main aspects and important topics in parallel kinematics, but also references novel concepts and approaches, i.e. type synthesis based on evolution, performance evaluation and optimization based on screw theory, singularity model taking into account motion and force transmissibility, and others.   This book is intended for researchers, scientists, engineers and postgraduates or above with interes...

  4. Giant Broad Line Regions in Dwarf Seyferts

    CERN Document Server

    Devereux, Nick

    2015-01-01

    High angular resolution spectroscopy obtained with the Hubble Space Telescope (HST) has revealed a remarkable population of galaxies hosting dwarf Seyfert nuclei with an unusually large broad-line region (BLR). These objects are remarkable for two reasons. Firstly, the size of the BLR can, in some cases, rival those seen in the most luminous quasars. Secondly, the size of the BLR is not correlated with the central continuum luminosity, an observation that distinguishes them from their reverberating counterparts. Collectively, these early results suggest that non-reverberating dwarf Seyferts are a heterogeneous group and not simply scaled versions of each other. Careful inspection reveals broad H Balmer emission lines with single peaks, double peaks, and a combination of the two, suggesting that the broad emission lines are produced in kinematically distinct regions centered on the black hole (BH). Because the gravitational field strength is already known for these objects, by virtue of knowing their BH mass, ...

  5. Kinematic Sunyaev-Zel'dovich Effect with Projected Fields: A Novel Probe of the Baryon Distribution with Planck, WMAP, and WISE Data

    Science.gov (United States)

    Hill, J. Colin; Ferraro, Simone; Battaglia, Nick; Liu, Jia; Spergel, David N.

    2016-07-01

    The kinematic Sunyaev-Zel'dovich (KSZ) effect—the Doppler boosting of cosmic microwave background (CMB) photons due to Compton scattering off free electrons with nonzero bulk velocity—probes the abundance and the distribution of baryons in the Universe. All KSZ measurements to date have explicitly required spectroscopic redshifts. Here, we implement a novel estimator for the KSZ—large-scale structure cross-correlation based on projected fields: it does not require redshift estimates for individual objects, allowing KSZ measurements from large-scale imaging surveys. We apply this estimator to cleaned CMB temperature maps constructed from Planck and WMAP data and a galaxy sample from the Wide-field Infrared Survey Explorer (WISE). We measure the KSZ effect at 3.8 σ - 4.5 σ significance, depending on the use of additional WISE galaxy bias constraints. We verify that our measurements are robust to possible dust emission from the WISE galaxies. Assuming the standard Λ cold dark matter cosmology, we directly constrain (fb/0.158 ) (ffree/1.0 ) =1.48 ±0.19 (statistical error only) at redshift z ≈0.4 , where fb is the fraction of matter in baryonic form and ffree is the free electron fraction. This is the tightest KSZ-derived constraint reported to date on these parameters. Astronomers have long known that baryons do not trace dark matter on ˜ kiloparsec scales and there has been strong evidence that galaxies are baryon poor. The consistency between the fb value found here and the values inferred from analyses of the primordial CMB and big bang nucleosynthesis verifies that baryons approximately trace the dark matter distribution down to ˜ megaparsec scales. While our projected-field estimator is already competitive with other KSZ approaches when applied to current data sets (because we are able to use the full-sky WISE photometric survey), it will yield enormous signal-to-noise ratios when applied to upcoming high-resolution, multifrequency CMB surveys.

  6. Kinematic Sunyaev-Zel'dovich Effect with Projected Fields: A Novel Probe of the Baryon Distribution with Planck, WMAP, and WISE Data.

    Science.gov (United States)

    Hill, J Colin; Ferraro, Simone; Battaglia, Nick; Liu, Jia; Spergel, David N

    2016-07-29

    The kinematic Sunyaev-Zel'dovich (KSZ) effect-the Doppler boosting of cosmic microwave background (CMB) photons due to Compton scattering off free electrons with nonzero bulk velocity-probes the abundance and the distribution of baryons in the Universe. All KSZ measurements to date have explicitly required spectroscopic redshifts. Here, we implement a novel estimator for the KSZ-large-scale structure cross-correlation based on projected fields: it does not require redshift estimates for individual objects, allowing KSZ measurements from large-scale imaging surveys. We apply this estimator to cleaned CMB temperature maps constructed from Planck and WMAP data and a galaxy sample from the Wide-field Infrared Survey Explorer (WISE). We measure the KSZ effect at 3.8σ-4.5σ significance, depending on the use of additional WISE galaxy bias constraints. We verify that our measurements are robust to possible dust emission from the WISE galaxies. Assuming the standard Λ cold dark matter cosmology, we directly constrain (f_{b}/0.158)(f_{free}/1.0)=1.48±0.19 (statistical error only) at redshift z≈0.4, where f_{b} is the fraction of matter in baryonic form and f_{free} is the free electron fraction. This is the tightest KSZ-derived constraint reported to date on these parameters. Astronomers have long known that baryons do not trace dark matter on ∼ kiloparsec scales and there has been strong evidence that galaxies are baryon poor. The consistency between the f_{b} value found here and the values inferred from analyses of the primordial CMB and big bang nucleosynthesis verifies that baryons approximately trace the dark matter distribution down to ∼ megaparsec scales. While our projected-field estimator is already competitive with other KSZ approaches when applied to current data sets (because we are able to use the full-sky WISE photometric survey), it will yield enormous signal-to-noise ratios when applied to upcoming high-resolution, multifrequency CMB surveys.

  7. A Search for Fine Wines: Discovering Close Red Dwarf-White Dwarf Binaries

    Science.gov (United States)

    Boyd, Mark; Finch, C. T.; Hambly, N. C.; Henry, T. J.; Jao, W.; Riedel, A. R.; Subasavage, J. P.; Winters, J. G.; RECONS

    2012-01-01

    Like fine wines, stars come in both red and white varieties. Here we present initial results of the Fine Wines Project that targets red dwarf-white dwarf pairs. The two scientific goals of Fine Wines are (1) to develop methods to estimate ages for red dwarfs based on the cooling ages of the white dwarfs, and (2) to identify suitable pairs for dynamical mass determinations of white dwarfs to probe their interior structures. Here we focus on the search for Fine Wines, including sample selection, elimination of false positives, and initial reconnaissance. The sample was extracted via color-color plots from a pool of more than 30,000 proper motion systems examined during the SuperCOSMOS-RECONS (SCR) and UCAC3 Proper Motion (UPM) surveys. The initial sample of 75 best candidates is being observed for BVRI photometry and 3500-9500 A spectroscopy to confirm whether or not the systems are red dwarf-white dwarf pairs. Early results indicate that roughly 50% of the candidates selected are indeed Fine Wine systems. This effort is supported by the NSF through grant AST 09-08402 and via observations made possible by the SMARTS Consortium.

  8. CFBDS J111807-064016: A new L/T transition brown dwarf in a binary system

    CERN Document Server

    Reylé, C; Artigau, É; Delfosse, X; Albert, L; Forveille, T; Rajpurohit, A S; Allard, F; Homeier, D; Robin, A C

    2013-01-01

    Stellar-substellar binary systems are quite rare, and provide interesting benchmarks. They constrain the complex physics of substellar atmospheres, because several physical parameters of the substellar secondary can be fixed from the much better characterized main sequence primary. We report the discovery of CFBDS J111807-064016, a T2 brown dwarf companion to 2MASS J111806.99-064007.8, a low-mass M4.5-M5 star. The brown-dwarf was identified from the Canada France Brown Dwarf Survey. At a distance of 50-120 pc, the 7.7 arcsec angular separation corresponds to projected separations of 390-900 AU. The primary displays no Halpha emission, placing a lower limit on the age of the system of about 6 Gyr. The kinematics is also consistent with membership in the old thin disc. We obtained near-infrared spectra, which together with recent atmosphere models allow us determine the effective temperature and gravity of both components. From these parameters and the age constraint, evolutionary models estimate masses of 0.10...

  9. A Near-Infrared Spectroscopic Survey of 886 Nearby M Dwarfs

    Science.gov (United States)

    Terrien, Ryan C.; Mahadevan, Suvrath; Deshpande, Rohit; Bender, Chad F.

    2015-09-01

    We present a catalog of near-infrared (NIR) spectra and associated measurements for 886 nearby M dwarfs. The spectra were obtained with the NASA-Infrared Telescope Facility SpeX Spectrograph during a two-year observing campaign; they have high signal-to-noise ratios (S/N > 100-150), span 0.8-2.4 μm, and have R˜ 2000. Our catalog of measured values contains useful Teff and composition-sensitive features, empirical stellar parameter measurements, and kinematic, photometric, and astrometric properties compiled from the literature. We focus on measurements of M dwarf abundances ([Fe/H] and [M/H]), capitalizing on the precision of recently published empirical NIR spectroscopic calibrations. We explore systematic differences between different abundance calibrations, and from other similar M dwarf catalogs. We confirm that the M dwarf abundances we measure show the expected inverse dependence with kinematic-, activity-, and color-based age indicators. Finally, we provide updated [Fe/H] and [M/H] for 16 M dwarf planet hosts. This catalog represents the largest published compilation of NIR spectra and associated parameters for M dwarfs. It provides a rich and uniform resource for nearby M dwarfs, and will be especially valuable for measuring Habitable Zone locations and comparative abundances of the M dwarf planet hosts that will be uncovered by upcoming exoplanet surveys.

  10. 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.

  11. White Dwarf - Red Dwarf Systems Resolved with the Hubble Space Telescope. II. Full Snapshot Survey Results

    CERN Document Server

    Farihi, J; Wachter, S

    2010-01-01

    {Abrigded} Results are presented for a Hubble Space Telescope Advanced Camera for Surveys high-resolution imaging campaign of 90 white dwarfs with known or suspected low mass stellar and substellar companions. Of the 72 targets which remain candidate and confirmed white dwarfs with near-infrared excess, 43 are spatially resolved into two or more components, and a total of 12 systems are potentially triples. There is a possible, slight deficit of earlier spectral types (bluer colors) among the spatially unresolved companions, exactly the opposite of expectations if significant mass is transferred to the companion during the common envelope phase. Using the best available distance estimates, the low mass companions to white dwarfs exhibit a bimodal distribution in projected separation. This result supports the hypothesis that during the giant phases of the white dwarf progenitor, any unevolved companions either migrate inward to short periods of hours to days, or outward to periods of hundreds to thousands of y...

  12. growth and physiological performance of west african dwarf goats

    African Journals Online (AJOL)

    user

    2014-09-02

    Sep 2, 2014 ... Department of Animal Science and ** Department of Crop Science. Faculty of ... production of small ruminants such as sheep ... JOURNAL OF RESEARCH IN FORESTRY, WILDLIFE AND .... African Dwarf Goat project.

  13. New Neighbors from 2MASS Activity and Kinematics at the Bottom of the Main Sequence

    CERN Document Server

    Gizis, J E; Reid, I N; Kirkpatrick, J D; Liebert, J; Williams, R J; Gizis, John E.; Monet, David G.; Liebert, James; Williams, Rik J.

    2000-01-01

    We have combined 2MASS and POSS II data in a search for nearby ultracool (later than M6.5) dwarfs with K_s6 Angstroms) ultracool M dwarfs are consistent with an ordinary old disk stellar population, while the kinematics of inactive ultracool M dwarfs are more typical of a 0.5 Gyr old population. The early L dwarfs in the sample have kinematics consistent with old ages, suggesting that the hydrogen burning limit is near spectral types L2-L4. We use the available data on M and L dwarfs to show that chromospheric activity drops with decreasing mass and temperature, and that at a given (M8 or later) spectral type, the younger field (brown) dwarfs are less active than many of the older, more massive field stellar dwarfs. Thus, contrary to the well-known stellar age-activity relationship, low activity in field ultracool dwarfs can be an indication of comparative youth and substellar mass.

  14. Planet Host Stars: Mass, Age and Kinematics

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    We determine the mass, age and kinematics of 51 extra-solar planet host stars. The results are then used to search for signs of connection of the data with metallicity and to investigate the population nature. We find that the increase in mean metallicity with stellar mass is similar to that in normal field stars, so it seems unsuitable to use this relation as a constraint on the theory of planet formation. The age and kinematic distributions seem to favour the metallicity of extra-solar planet host stars being initial. Although the kinematic data of these stars indicate their origin from two populations - the thin and the thick disks, kinematics may not help in the maintenance of the planet around the host. Stars with planets, brown dwarfs or stellar companions are sorted into three groups and re-investigated separately for their formation mechanism. The main results indicate that stars with M2 < 25MJ have [Fe/H] > -0.1 and a wide period range, but there are no other differences.Thus, there does not seem to be any physically distinguishable characteristics among the three star groups.

  15. The Hyperactive L Dwarf 2MASS J13153094-2649513: Continued Emission and a Brown Dwarf Companion

    Science.gov (United States)

    Burgasser, Adam J.; Sitarski, Breann N.; Gelino, Christopher R.; Logsdon, Sarah E.; Perrin, Marshall D.

    2011-09-01

    We report new observations of the unusually active, high proper motion L5e dwarf 2MASS J13153094-2649513. Optical spectroscopy with Magellan/MagE reveals persistent nonthermal emission, with narrow H I Balmer, Na I and K I lines all observed in emission. Low-resolution near-infrared spectroscopy with the Infrared Telescope Facility/SpeX Spectrograph indicates the presence of a low-temperature companion, which is resolved through multi-epoch laser guide star adaptive optics imaging at the W. M. Keck Observatory. The co-moving companion is separated by 338 ± 4 mas, and its relative brightness (ΔKs = 5.09 ± 0.10) makes this system the second-most-extreme flux ratio very-low-mass binary identified to date. Resolved near-infrared spectroscopy with Keck/OSIRIS identifies the companion as a T7 dwarf. The absence of Li I absorption in combined-light optical spectroscopy constrains the system age to gsim0.8-1.0 Gyr, while the system's kinematics and unusually low mass ratio (M 2/M 1 = 0.3-0.6) suggest that it is even older. A coevality test of the components also indicates an older age, but reveals discrepancies between evolutionary and atmosphere model fits of the secondary, which are likely attributable to poor reproduction of its near-infrared spectrum. With a projected separation of 6.6 ± 0.9 AU, the 2MASS J1315-2649 system is too widely separated for mass exchange or magnetospheric interactions to be powering its persistent nonthermal emission. Rather, the emission is probably chromospheric in nature, consistent with an inversion in the age-activity relation in which strong magnetic fields are maintained by relatively old and massive ultracool dwarfs. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration, and made possible by the generous financial support of the W. M. Keck

  16. Microlensing Planet Around Brown-Dwarf

    CERN Document Server

    Han, C; Udalski, A; Sumi, T; Gaudi, B S; Gould, A; Bennett, D P; Tsapras, Y; Szymański, M K; Kubiak, M; Pietrzyński, G; Soszyński, I; Skowron, J; Kozłowski, S; Poleski, R; Ulaczyk, K; Wyrzykowski, Ł; Pietrukowicz, P; Abe, F; Bond, I A; Botzler, C S; Chote, P; Freeman, M; Fukui, A; Furusawa, K; Harris, P; Itow, Y; Ling, C H; Masuda, K; Matsubara, Y; Muraki, Y; Ohnishi, K; Rattenbury, N J; Saito, To; Sullivan, D J; Sweatman, W L; Suzuki, D; Tristram, P J; Wada, K; Yock, P C M; Batista, V; Christie, G; Choi, J -Y; DePoy, D L; Dong, Subo; Hwang, K -H; Kavka, A; Lee, C -U; Monard, L A G; Natusch, T; Ngan, H; Park, H; Pogge, R W; Porritt, I; Shin, I -G; Tan, T G; Yee, J C; Alsubai, K A; Bramich, D M; Browne, P; Dominik, M; Horne, K; Hundertmark, M; Ipatov, S; Kains, N; Liebig, C; Snodgrass, C; Steele, I A; Street, R A

    2013-01-01

    Observations of accretion disks around young brown dwarfs have led to the speculation that they may form planetary systems similar to normal stars. While there have been several detections of planetary-mass objects around brown dwarfs (2MASS 1207-3932 and 2MASS 0441-2301), these companions have relatively large mass ratios and projected separations, suggesting that they formed in a manner analogous to stellar binaries. We present the discovery of a planetary-mass object orbiting a field brown dwarf via gravitational microlensing, OGLE-2012-BLG-0358Lb. The system is a low secondary/primary mass ratio (0.080 +- 0.001), relatively tightly-separated (~0.87 AU) binary composed of a planetary-mass object with 1.9 +- 0.2 Jupiter masses orbiting a brown dwarf with a mass 0.022 M_Sun. The relatively small mass ratio and separation suggest that the companion may have formed in a protoplanetary disk around the brown dwarf host, in a manner analogous to planets.

  17. The stellar kinematics in the solar neighborhood from LAMOST data

    CERN Document Server

    Tian, Hai-Jun; Carlin, Jeffrey L; Zhao, Yong-Heng; Chen, Xue-Lei; Wu, Yue; Li, Guang-Wei; Hou, Yong-Hui; Zhang, Yong

    2015-01-01

    We use about 200,000 FGK type main-sequence stars from the LAMOST DR1 data to map the local stellar kinematics. With the velocity de-projection technique, we are able to derive the averaged 3 dimensional velocity and velocity ellipsoids using only the line-of-sight velocity for the stars with various effective temperatures within $100 6000$K show a net asymmetric motion of $\\sim3 km\\,s^{-1}$ in $\\langle W\\rangle$ compared to the stars with ${T}_{\\rm eff}<6000$K. And their azimuthal velocity increases when $|z|$ increases. This peculiar motion in the warmer stars is likely because they are young and not completely relaxed, although other reasons, such as the resonance induced by the central rotating bar or the spiral structures, and the perturbation of the merging dwarf galaxies, can not be ruled out. The derived velocity dispersions and cross terms for the data are approximately consistent with previous studies. We also find that the vertical gradients of $\\sigma_{U}$ and $\\sigma_V$ are larger than that of...

  18. A Magellanic Origin of the DES Dwarfs

    CERN Document Server

    Jethwa, Prashin; Belokurov, Vasily

    2016-01-01

    We establish the connection between the Magellanic Clouds (MCs) and the dwarf galaxy candidates discovered in the Dark Energy Survey (DES) by building a dynamical model of the MC satellite populations, based on an extensive suite of tailor-made numerical simulations. Our model takes into account the response of the Galaxy to the MCs infall, the dynamical friction experienced by the MCs and the disruption of the MC satellites by their hosts. The simulation suite samples over the uncertainties in the MC's proper motions, the masses of the MW and the Clouds themselves and allows for flexibility in the intrinsic volume density distribution of the MC satellites. As a result, we can accurately reproduce the DES satellites' observed positions and kinematics. Assuming that Milky Way (MW) dwarfs follow the distribution of subhaloes in $\\Lambda$CDM, we further demonstrate that, of 14 observed satellites, the MW halo contributes fewer than 4 (8) of these with 68% (95%) confidence and that 7 (12) DES dwarfs have probabil...

  19. Dwarf spheroidal galaxies and Bose-Einstein condensate dark matter

    CERN Document Server

    Diez-Tejedor, Alberto; Profumo, Stefano

    2014-01-01

    We constrain the parameters of a self-interacting massive dark matter scalar particle in a condensate using the kinematics of the eight brightest dwarf spheroidal satellites of the Milky Way. For the case of an attractive self-interaction the condensate develops a mass density profile with a characteristic scale radius that is closely related to the fundamental parameters of the theory. We find that the velocity dispersion of dwarf spheroidal galaxies suggests a scale radius of the order of 1 kpc, in tension with previous results found using the rotational curve of low-surface-brightness and dwarf galaxies. We discuss the implications of our findings for the particle dark matter model and argue that a single classical coherent state cannot play, in general, a relevant role for the description of dark matter in galaxies.

  20. On high proper motion white dwarfs from photographic surveys

    CERN Document Server

    Reylé, C; Creze, M; Reyle, Celine; Robin, Annie C.; Creze, Michel

    2001-01-01

    The interpretation of high proper motion white dwarfs detected by Oppenheimer et al (2001) was the start of a tough controversy. While the discoverers identify a large fraction of their findings as dark halo members, others interpret the same sample as essentially made of disc and/or thick disc stars. We use the comprehensive description of galactic stellar populations provided by the "Besancon" model to produce a realistic simulation of Oppenheimer et al. data, including all observational selections and calibration biases. The conclusion is unambiguous: Thick disc white dwarfs resulting from ordinary hypotheses on the local density and kinematics are sufficient to explain the observed objects, there is no need for halo white dwarfs. This conclusion is robust to reasonable changes in model ingredients. The main cause of the misinterpretation seems to be that the velocity distribution of a proper motion selected star sample is severely biased in favour of high velocities. This has been neglected in previous an...

  1. Metallicities and kinematics for dwarf spheroidals in the local group

    NARCIS (Netherlands)

    Battaglia, G.; Tolstoy, E.; Helmi, A.; Irwin, M.; Randich, S; Pasquini, L

    2006-01-01

    We present the first results of Call triplet observations from VLT/FLAMES for Sculptor, Fornax and Sextans dSphs. For each galaxy, we obtained accurate velocity and metallicity measurements for hundreds of stars out to and beyond the tidal radius. In each case, we find clear evidence for the presenc

  2. KINEMATICS AND VELOCITY ELLIPSOID OF THE SOLAR NEIGHBORHOOD WHITE DWARFS

    OpenAIRE

    2015-01-01

    Con el objeto de determinar la distribuci ́on de velocidades de las enanas blancas en el entorno solar utilizamos las componentes de la velocidad espacial. Utilizamos dos muestras, las m ́as cercanas que 20 y 25 pc. Ade m ́as, calculamos el movimiento solar y las dispersiones de velocidades para c uatro sub-muestras, a saber, DA, no-DA, enanas blancas calientes, y fr ́ıas. La com paraci ́on de nuestros resultados para las muestras de 20 y 25 pc da como resultado un a buena concordan- cia, mie...

  3. KINEMATICS AND VELOCITY ELLIPSOID OF THE SOLAR NEIGHBORHOOD WHITE DWARFS

    Directory of Open Access Journals (Sweden)

    W. H. Elsanhoury

    2015-01-01

    Full Text Available Con el objeto de determinar la distribuci ́on de velocidades de las enanas blancas en el entorno solar utilizamos las componentes de la velocidad espacial. Utilizamos dos muestras, las m ́as cercanas que 20 y 25 pc. Ade m ́as, calculamos el movimiento solar y las dispersiones de velocidades para c uatro sub-muestras, a saber, DA, no-DA, enanas blancas calientes, y fr ́ıas. La com paraci ́on de nuestros resultados para las muestras de 20 y 25 pc da como resultado un a buena concordan- cia, mientras que los resultados de las comparaciones entre las otras sub-muestras no concuerdan. Se discute la dependencia de las dispersione s de velocidades y el movimiento solar de la composici ́on qu ́ımica y la temperatu ra efectiva

  4. Irradiated brown dwarfs

    CERN Document Server

    Casewell, S L; Lawrie, K A; Maxted, P F L; Dobbie, P D; Napiwotzki, R

    2014-01-01

    We have observed the post common envelope binary WD0137-349 in the near infrared $J$, $H$ and $K$ bands and have determined that the photometry varies on the system period (116 min). The amplitude of the variability increases with increasing wavelength, indicating that the brown dwarf in the system is likely being irradiated by its 16500 K white dwarf companion. The effect of the (primarily) UV irradiation on the brown dwarf atmosphere is unknown, but it is possible that stratospheric hazes are formed. It is also possible that the brown dwarf (an L-T transition object) itself is variable due to patchy cloud cover. Both these scenarios are discussed, and suggestions for further study are made.

  5. The ATLA$^{\\rm{3D}}$ project - XXV: Two-dimensional kinematic analysis of simulated galaxies and the cosmological origin of fast and slow rotators

    CERN Document Server

    Naab, T; Emsellem, E; Cappellari, M; Krajnovic, D; McDermid, R M; Alatalo, K; Bayet, E; Blitz, L; Bois, M; Bournaud, F; Bureau, M; Crocker, A; Davies, R L; Davis, T A; de Zeeuw, P T; Duc, P -A; Hirschmann, M; Johansson, P H; Khochfar, S; Kuntschner, H; Morganti, R; Oosterloo, T; Sarzi, M; Scott, N; Serra, P; van de Ven, G; Weijmans, A; Young, L M

    2013-01-01

    We present a detailed two-dimensional stellar dynamical analysis of a sample of 44 cosmological hydrodynamical simulations of individual central galaxies and their satellites. Kinematic maps of the stellar line-of-sight velocity, velocity dispersion, and higher-order Gauss-Hermite moments $h_3$ and $h_4$ are constructed for each central galaxy and for the most massive satellites. The amount of rotation is quantified using the $\\lambda_{\\mathrm{R}}$-parameter. The velocity, velocity dispersion, $h_3$, and $h_4$ fields of the simulated galaxies show a diversity similar to observed kinematic maps of early-type galaxies in the ATLAS$^{\\rm{3D}}$ survey. This includes fast (regular), slow, and misaligned rotation, hot spheroids with embedded cold disk components as well as galaxies with counter-rotating cores or central depressions in the velocity dispersion. We link the present day kinematic properties to the individual cosmological formation histories of the galaxies. In general, major galaxy mergers have a signi...

  6. The Properties of the 500 K Dwarf UGPS J072227.51-054031.2, and a Study of the Far-Red Flux of Cold Brown Dwarfs

    CERN Document Server

    Leggett, S K; Marley, M S; Lodders, K; Canty, J; Lucas, P; Smart, R L; Tinney, C G; Homeier, D; Allard, F; Burningham, Ben; Day-Jones, A; Fegley, B; Ishii, Miki; Jones, H R A; Marocco, F; Pinfield, D J; Tamura, M

    2012-01-01

    We present i and z photometry for 25 T dwarfs and one L dwarf. Combined with published photometry, the data show that the i - z, z - Y and z - J colors of T dwarfs are very red, and continue to increase through to the late-type T dwarfs, with a hint of a saturation for the latest types with T_eff ~ 600 K. We present new 0.7-1.0 um and 2.8-4.2 um spectra for the very late-type T dwarf UGPS J072227.51-054031.2, as well as improved astrometry for this dwarf. Examination of the spectral energy distribution using the new and published data, with Saumon & Marley models, shows that the dwarf has T_eff = 505 +/- 10 K, a mass of 3-11 M_Jupiter and an age between 60 Myr and 1 Gyr. This young age is consistent with the thin disk kinematics of the dwarf. The mass range overlaps with that usually considered to be planetary, despite this being an unbound object discovered in the field near the Sun. This apparently young rapid rotator is also undergoing vigorous atmospheric mixing, as determined by the IRAC and WISE-2 4...

  7. Dwarfs in ancient Egypt.

    Science.gov (United States)

    Kozma, Chahira

    2006-02-15

    Ancient Egypt was one of the most advanced and productive civilizations in antiquity, spanning 3000 years before the "Christian" era. Ancient Egyptians built colossal temples and magnificent tombs to honor their gods and religious leaders. Their hieroglyphic language, system of organization, and recording of events give contemporary researchers insights into their daily activities. Based on the record left by their art, the ancient Egyptians documented the presence of dwarfs in almost every facet of life. Due to the hot dry climate and natural and artificial mummification, Egypt is a major source of information on achondroplasia in the old world. The remains of dwarfs are abundant and include complete and partial skeletons. Dwarfs were employed as personal attendants, animal tenders, jewelers, and entertainers. Several high-ranking dwarfs especially from the Old Kingdom (2700-2190 BCE) achieved important status and had lavish burial places close to the pyramids. Their costly tombs in the royal cemeteries and the inscriptions on their statutes indicate their high-ranking position in Egyptian society and their close relation to the king. Some of them were Seneb, Pereniankh, Khnumhotpe, and Djeder. There were at least two dwarf gods, Ptah and Bes. The god Ptah was associated with regeneration and rejuvenation. The god Bes was a protector of sexuality, childbirth, women, and children. He was a favored deity particularly during the Greco-Roman period. His temple was recently excavated in the Baharia oasis in the middle of Egypt. The burial sites and artistic sources provide glimpses of the positions of dwarfs in daily life in ancient Egypt. Dwarfs were accepted in ancient Egypt; their recorded daily activities suggest assimilation into daily life, and their disorder was not shown as a physical handicap. Wisdom writings and moral teachings in ancient Egypt commanded respect for dwarfs and other individuals with disabilities.

  8. Kinematic space and wormholes

    Science.gov (United States)

    Zhang, Jian-dong; Chen, Bin

    2017-01-01

    The kinematic space could play a key role in constructing the bulk geometry from dual CFT. In this paper, we study the kinematic space from geometric points of view, without resorting to differential entropy. We find that the kinematic space could be intrinsically defined in the embedding space. For each oriented geodesic in the Poincaré disk, there is a corresponding point in the kinematic space. This point is the tip of the causal diamond of the disk whose intersection with the Poincaré disk determines the geodesic. In this geometric construction, the causal structure in the kinematic space can be seen clearly. Moreover, we find that every transformation in the SL(2,R) leads to a geodesic in the kinematic space. In particular, for a hyperbolic transformation defining a BTZ black hole, it is a timelike geodesic in the kinematic space. We show that the horizon length of the static BTZ black hole could be computed by the geodesic length of corresponding points in the kinematic space. Furthermore, we discuss the fundamental regions in the kinematic space for the BTZ blackhole and multi-boundary wormholes.

  9. Kinematic Space and Wormholes

    CERN Document Server

    Zhang, Jian-dong

    2016-01-01

    The kinematic space could play a key role in constructing the bulk geometry from dual CFT. In this paper, we study the kinematic space from geometric points of view, without resorting to differential entropy. We find that the kinematic space could be intrinsically defined in the embedding space. For each oriented geodesic in the Poincar\\'e disk, there is a corresponding point in the kinematic space. This point is the tip of the causal diamond of the disk whose intersection with the Poincar\\'e disk determines the geodesic. In this geometric construction, the causal structure in the kinematic space can be seen clearly. Moreover, we find that every transformation in the $SL(2,\\mathbb{R})$ leads to a geodesic in the kinematic space. In particular, for a hyperbolic transformation defining a BTZ black hole, it is a timelike geodesic in the kinematic space. We show that the horizon length of the static BTZ black hole could be computed by the geodesic length of corresponding points in the kinematic space. Furthermore...

  10. Kinematics theory and applications

    CERN Document Server

    Wittenburg, Jens

    2016-01-01

    The book deals with kinematics of mechanisms. It focuses on a solid theoretical foundation and on mathematical methods applicable to the solution of problems of very diverse nature. Applications are demonstrated in a large number of fully worked-out problems.  In kinematics a wide variety of mathematical tools is applicable. In this book, wherever possible vector equations are formulated instead of lengthy scalar coordinate equations. The principle of transference is applied to problems of very diverse nature. 15 chapters of the book are devoted to spatial kinematics and three chapters to planar kinematics. In Chapt. 19 nonlinear dynamics equations of motion are formulated for general spatial mechanisms. Nearly one half of the book is dealing with position theory and the other half with motion. The book is intended for use as reference book for researchers and as textbook in advanced courses on kinematics of mechanisms.

  11. The Origin of Dwarf Early-Type Galaxies in the Virgo Cluster

    NARCIS (Netherlands)

    Toloba, E.; Boselli, A.; Peletier, R. F.; Gorgas, J.

    2011-01-01

    We present new medium resolution kinematic data for a sample of 21 dwarf early-type galaxies (dEs) mainly in the Virgo cluster. These data are used to study the origin of the dE population inhabiting rich clusters. Within them we detect two different subpopulations: half of the sample (52%) are rota

  12. White Dwarf Mass Distribution

    CERN Document Server

    Kepler, S O; Romero, Alejandra Daniela; Ourique, Gustavo; Pelisoli, Ingrid

    2016-01-01

    We present the mass distribution for all S/N > 15 pure DA white dwarfs detected in the Sloan Digital Sky Survey up to Data Release 12, fitted with Koester models for ML2/alpha=0.8, and with Teff > 10 000 K, and for DBs with S/N >10, fitted with ML2/alpha=1.25, for Teff > 16 000 K. These mass distributions are for log g > 6.5 stars, i.e., excluding the Extremely Low Mass white dwarfs. We also present the mass distributions corrected by volume with the 1/Vmax approach, for stars brighter than g=19. Both distributions have a maximum at M=0.624 Msun but very distinct shapes. From the estimated z-distances, we deduce a disk scale height of 300 pc. We also present 10 probable halo white dwarfs, from their galactic U, V, W velocities.

  13. The K2-ESPRINT Project III: A Close-in Super-Earth around a Metal-rich Mid-M Dwarf

    Science.gov (United States)

    Hirano, Teruyuki; Fukui, Akihiko; Mann, Andrew W.; Sanchis-Ojeda, Roberto; Gaidos, Eric; Narita, Norio; Dai, Fei; Van Eylen, Vincent; Lee, Chien-Hsiu; Onozato, Hiroki; Ryu, Tsuguru; Kusakabe, Nobuhiko; Ito, Ayaka; Kuzuhara, Masayuki; Onitsuka, Masahiro; Tatsuuma, Misako; Nowak, Grzegorz; Pallè, Enric; Ribas, Ignasi; Tamura, Motohide; Yu, Liang

    2016-03-01

    We validate a {R}p=2.32+/- 0.24{R}\\oplus planet on a close-in orbit (P = 2.260455 ± 0.000041 days) around K2-28 (EPIC 206318379), a metal-rich M4-type dwarf in the Campaign 3 field of the K2 mission. Our follow-up observations included multi-band transit observations from the optical to the near-infrared, low-resolution spectroscopy, and high-resolution adaptive optics (AO) imaging. We perform a global fit to all of the observed transits using a Gaussian process-based method and show that the transit depths in all of the passbands adopted for the ground-based transit follow-ups ({r}2\\prime ,{z}s,2,J,H,{K}s) are within ˜2σ of the K2 value. Based on a model of the background stellar population and the absence of nearby sources in our AO imaging, we estimate the probability that a background eclipsing binary could cause a false positive to be GJ 1214b. Given the relative brightness of K2-28 in the near-infrared ({m}{Kep}=14.85 mag and mH = 11.03 mag) and relatively deep transit (0.6%-0.7%), a comparison between the atmospheric properties of these two planets with future observations would be especially interesting.

  14. The ACS LCID Project XI. On the early time resolution of LG dwarf galaxy SFHs: Comparing the effects of reionization in models with observations

    CERN Document Server

    Aparicio, Antonio; Skillman, Evan; Cassisi, Santi; Mayer, Lucio; Navarro, Julio; Cole, Andrew; Gallart, Carme; Monelli, Matteo; Weisz, Daniel; Bernard, Edouard; Dolphin, Andrew; Stetson, Peter

    2016-01-01

    The analysis of the early star formation history (SFH) of nearby galaxies, obtained from their resolved stellar populations is relevant as a test for cosmological models. However, the early time resolution of observationally derived SFHs is limited by several factors. Thus, direct comparison of observationally derived SFHs with those derived from theoretical models of galaxy formation is potentially biased. Here we investigate and quantify this effect. For this purpose, we analyze the duration of the early star formation activity in a sample of four Local Group dwarf galaxies and test whether they are consistent with being true fossils of the pre-reionization era; i.e., if the quenching of their star formation occurred before cosmic reionization by UV photons was completed. Two classical dSph (Cetus and Tucana) and two dTrans (LGS-3 and Phoenix) isolated galaxies with total stellar masses between $1.3\\times 10^6$ to $7.2\\times 10^6$ M$_\\odot$ have been studied. Accounting for time resolution effects, the SFHs...

  15. The K2-ESPRINT Project III: A Close-in Super-Earth around a Metal-rich Mid-M Dwarf

    CERN Document Server

    Hirano, Teruyuki; Mann, Andrew W; Sanchis-Ojeda, Roberto; Gaidos, Eric; Narita, Norio; Dai, Fei; Van Eylen, Vincent; Lee, Chien-Hsiu; Onozato, Hiroki; Ryu, Tsuguru; Kusakabe, Nobuhiko; Ito, Ayaka; Kuzuhara, Masayuki; Onitsuka, Masahiro; Tatsuuma, Misako; Nowak, Grzegorz; Pallè, Enric; Ribas, Ignasi; Tamura, Motohide; Yu, Liang

    2015-01-01

    We validate a candidate super-Earth ($R_p=2.38\\pm 0.25R_\\oplus$) on a close-in orbit ($P=2.26$ days) around EPIC 206318379, a metal-rich M4-type dwarf in the Campaign 3 field of the K2 mission. Our follow-up observations included multi-band transit observations from the optical to the near infrared, low-resolution spectroscopy, and high-resolution adaptive-optics (AO) imaging. The phase-folded K2 transit light curve has a V-shape because the transit duration around this small star is comparable to the 30-minute K2 cadence. However, the light curves from our follow-up observations exhibit a sharp ingress and/or egress and flat bottom, ruling out a grazing eclipse of a binary system. We perform a global fit to all ground-based observations using a Gaussian process-based method and show that the transit depths in all passbands ($r'_2, z_\\mathrm{s,2}, J, H, K_\\mathrm{s}$) are within $2.2\\sigma$ of the K2 value. Based on a model of the background stellar population and the absence of nearby sources in our AO imagi...

  16. Axions and White Dwarfs

    CERN Document Server

    Isern, J; Garcia-Berro, E; Salaris, M; Torres, S

    2010-01-01

    White dwarfs are almost completely degenerate objects that cannot obtain energy from the thermonuclear sources and their evolution is just a gravothermal process of cooling. The simplicity of these objects, the fact that the physical inputs necessary to understand them are well identified, although not always well understood, and the impressive observational background about white dwarfs make them the most well studied Galactic population. These characteristics allow to use them as laboratories to test new ideas of physics. In this contribution we discuss the robustness of the method and its application to the axion case.

  17. Local Volume TiNy Titans: Gaseous Dwarf-Dwarf Interactions in the Local Universe

    CERN Document Server

    Pearson, Sarah; Putman, Mary E; Lutz, Katharina A; Fernandez, Ximena; Stierwalt, Sabrina; Patton, David R; Kim, Jinhyub; Kallivayalil, Nitya; Johnson, Kelsey; Sung, Eon-Chang

    2016-01-01

    In this paper, we introduce the Local Volume TiNy Titans sample (LV-TNT), which is a part of a larger body of work on interacting dwarf galaxies: TNT (Stierwalt et al. 2015). This LV-TNT sample consists of 10 dwarf galaxy pairs in the Local Universe (< 30 Mpc from Milky Way), which span mass ratios of M_(*,1)/M_(*,2) < 20, projected separations < 100 kpc, and pair member masses of log(M_*/M_Sun) < 9.9. All 10 LV-TNT pairs have resolved synthesis maps of their neutral hydrogen, are located in a range of environments and captured at various interaction stages. This enables us to do a comparative study of the diffuse gas in dwarf-dwarf interactions and disentangle the gas lost due to interactions with halos of massive galaxies, from the gas lost due to mutual interaction between the dwarfs. We find that the neutral gas is extended in the interacting pairs when compared to non-paired analogs, indicating that gas is tidally pre-processed. Additionally, we find that the environment can shape the HI dist...

  18. Dwarf galaxies in the Antlia Cluster: First results

    CERN Document Server

    Castelli, A V S; Cellone, S A; Richtler, T; Dirsch, B; Infante, L; Aruta, C; Gómez, M

    2006-01-01

    We present the first results of a project aimed to study the galaxy population of the Antlia cluster, the third nearest galaxy cluster after Virgo and Fornax. The observations for the Antlia project consist of Washington wide-field images taken with the MOSAIC camera mounted at the prime focus of the CTIO 4-m Blanco telescope. Our preliminary results correspond to the identification and classification of dwarf galaxies in the central cluster region, extending the list of Ferguson & Sandage (1990). The final aim of our project is to study the luminosity function, morphology and structural parameters of dwarf galaxies in the Antlia cluster with a more complete sample.

  19. GTC OSIRIS z-band imaging of Y dwarfs

    CERN Document Server

    Lodieu, N; Rebolo, R

    2013-01-01

    The aim of the project is to contribute to the characterisation of the spectral energy distribution of the coolest brown dwarfs discovered to date, the Y dwarfs. We obtained z-band far-red imaging for six Y dwarfs and a T9+Y0 binary with the OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) instrument on the 10.4-m Gran Telescopio de Canarias (GTC). We detect five of the seven known Y dwarfs in the $z$-band, infer their optical-to-infrared colours, and measure their proper motions. We find a higher dispersion in the z-J and z-H colours of Y0 dwarfs than in T dwarfs. This dispersion is found to be correlated with H-w2. The high dispersion in the optical-to-infrared colours of Y dwarfs and the possible turn-over towards bluer colours may be a consequence of the presence of sulfide clouds with different thicknesses, the depletion of alcalines, and/or gravity effects.

  20. Analysis of White Dwarfs with Strange-Matter Cores

    CERN Document Server

    Mathews, G J; O'Gorman, B; Lan, N Q; Zech, W; Otsuki, K; Weber, F

    2006-01-01

    We summarize masses and radii for a number of white dwarfs as deduced from a combination of proper motion studies, Hipparcos parallax distances, effective temperatures, and binary or spectroscopic masses. A puzzling feature of these data is that some stars appear to have radii which are significantly smaller than that expected for a standard electron-degenerate white-dwarf equations of state. We construct a projection of white-dwarf radii for fixed effective mass and conclude that there is at least marginal evidence for bimodality in the radius distribution forwhite dwarfs. We argue that if such compact white dwarfs exist it is unlikely that they contain an iron core. We propose an alternative of strange-quark matter within the white-dwarf core. We also discuss the impact of the so-called color-flavor locked (CFL) state in strange-matter core associated with color superconductivity. We show that the data exhibit several features consistent with the expected mass-radius relation of strange dwarfs. We identify ...

  1. Advances in robot kinematics

    CERN Document Server

    Khatib, Oussama

    2014-01-01

    The topics addressed in this book cover the whole range of kinematic analysis, synthesis and design and consider robotic systems possessing serial, parallel and cable driven mechanisms. The robotic systems range from being less than fully mobile to kinematically redundant to overconstrained.  The fifty-six contributions report the latest results in robot kinematics with emphasis on emerging areas such as design and control of humanoids or humanoid subsystems. The book is of interest to researchers wanting to bring their knowledge up to date regarding modern topics in one of the basic disciplines in robotics, which relates to the essential property of robots, the motion of mechanisms.

  2. White Dwarfs in Globular Clusters

    CERN Document Server

    Möhler, S

    2008-01-01

    We review empirical and theoretical findings concerning white dwarfs in Galactic globular clusters. Since their detection is a critical issue we describe in detail the various efforts to find white dwarfs in globular clusters. We then outline the advantages of using cluster white dwarfs to investigate the formation and evolution of white dwarfs and concentrate on evolutionary channels that appear to be unique to globular clusters. We also discuss the usefulness of globular cluster white dwarfs to provide independent information on the distances and ages of globular clusters, information that is very important far beyond the immediate field of white dwarf research. Finally, we mention possible future avenues concerning globular cluster white dwarfs, like the study of strange quark matter or plasma neutrinos.

  3. The ACS LCID Project. XI. On the Early Time Resolution of SFHs of Local Group Dwarf Galaxies: Comparing the Effects of Reionization in Models with Observations

    Science.gov (United States)

    Aparicio, Antonio; Hidalgo, Sebastian L.; Skillman, Evan; Cassisi, Santi; Mayer, Lucio; Navarro, Julio; Cole, Andrew; Gallart, Carme; Monelli, Matteo; Weisz, Daniel; Bernard, Edouard; Dolphin, Andrew; Stetson, Peter

    2016-05-01

    The analysis of the early star formation history (SFH) of nearby galaxies, obtained from their resolved stellar populations, is relevant as a test for cosmological models. However, the early time resolution of observationally derived SFHs is limited by several factors. Thus, direct comparison of observationally derived SFHs with those derived from theoretical models of galaxy formation is potentially biased. Here we investigate and quantify this effect. For this purpose, we analyze the duration of the early star formation activity in a sample of four Local Group dwarf galaxies and test whether they are consistent with being true fossils of the pre-reionization era; i.e., if the quenching of their star formation occurred before cosmic reionization by UV photons was completed. Two classical dSph (Cetus and Tucana) and two dTrans (LGS-3 and Phoenix) isolated galaxies with total stellar masses between 1.3× {10}6 and 7.2× {10}6 {M}⊙ have been studied. Accounting for time resolution effects, the SFHs peak as much as 1.25 Gyr earlier than the optimal solutions. Thus, this effect is important for a proper comparison of model and observed SFHs. It is also shown that none of the analyzed galaxies can be considered a true fossil of the pre-reionization era, although it is possible that the outer regions of Cetus and Tucana are consistent with quenching by reionization. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #10505.

  4. Eastern Spruce Dwarf Mistletoe

    Science.gov (United States)

    F. Baker; Joseph O' Brien; R. Mathiasen; Mike Ostry

    2006-01-01

    Eastern spruce dwarf mistletoe (Arceuthobium pusillum) is a parasitic flowering plant that causes the most serious disease of black spruce (Picea mariana) throughout its range. The parasite occurs in the Canadian provinces of Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, and Newfoundland; in the Lake States of Minnesota,...

  5. Lodgepole Pine Dwarf Mistletoe

    Science.gov (United States)

    Frank G. Hawksworth; Oscar J. Dooling

    1984-01-01

    Lodgepole pine dwarf mistletoe (Arceuthobium americanum Nutt. ex Engelm.) is a native, parasitic, seed plant that occurs essentially throughout the range of lodgepole pine in North America. It is the most damaging disease agent in lodgepole pine, causing severe growth loss and increased tree mortality. Surveys in the Rocky Mountains show that the parasite is found in...

  6. Mass modelling of dwarf spheroidal galaxies: the effect of unbound stars from tidal tails and the Milky Way

    CERN Document Server

    Klimentowski, J; Kazantzidis, S; Prada, F; Mayer, L; Mamon, G A; Klimentowski, Jaroslaw; Lokas, Ewa L.; Kazantzidis, Stelios; Prada, Francisco; Mayer, Lucio; Mamon, Gary A.

    2006-01-01

    We study the origin and properties of the population of unbound stars in the kinematic samples of dwarf spheroidal galaxies. For this purpose we have run a high resolution N-body simulation of a two-component dwarf galaxy orbiting in a Milky Way potential. In agreement with the tidal stirring scenario of Mayer et al., the dwarf is placed on a highly eccentric orbit, its initial stellar component is in the form of an exponential disk and it has a NFW-like dark matter halo. After 10 Gyrs of evolution the dwarf produces a spheroidal stellar component and is strongly tidally stripped so that mass follows light and the stars are on almost isotropic orbits. From this final state, we create mock kinematic data sets for 200 stars by observing the dwarf in different directions. We find that when the dwarf is observed along the tidal tails the kinematic samples are strongly contaminated by unbound stars from the tails. We also study another source of possible contamination by adding stars from the Milky Way. We demonst...

  7. Runaway M Dwarf Candidates from the Sloan Digital Sky Survey

    CERN Document Server

    Favia, Andrej; Theissen, Christopher A

    2015-01-01

    We present a sample of 20 runaway M dwarf candidates (RdMs) within 1 kpc of the Sun whose Galactocentric velocities exceed 400 km s$^{-1}$. The candidates were selected from the SDSS DR7 M Dwarf Catalog of West et al. (2011). Our RdMs have SDSS+USNO-B proper motions that are consistent with those recorded in the PPMXL, LSPM, and combined WISE+SDSS+2MASS catalogs. Sixteen RdMs are classified as dwarfs, while the remaining four RdMs are subdwarfs. We model the Galactic potential using a bulge-disk-halo profile (Kenyon et al. 2008; Brown et al. 2014). Our fastest RdM, with Galactocentric velocity 658.5 $\\pm$ 236.9 km s$^{-1}$, is a possible hypervelocity candidate, as it is unbound in 77% of our simulations. About half of our RdMs have kinematics that are consistent with ejection from the Galactic center. Seven of our RdMs have kinematics consistent with an ejection scenario from M31 or M32 to within 2{\\sigma}, although our distance-limited survey makes such a realization unlikely. No more than four of our RdMs ...

  8. The Parentage of Magnetic White Dwarfs: Implications from Their Space Motions

    Science.gov (United States)

    Anselowitz, Tara; Wasatonic, Richard; Matthews, Karen; Sion, Edward M.; McCook, George P.

    1999-06-01

    We have examined the statistical properties, cooling ages, and vector components of the three-dimensional space motion U, V, W for the enlarged sample of 53 magnetic white dwarfs contained in the fourth edition of the Catalog of Spectroscopically Identified White Dwarfs (McCook & Sion). Their cooling ages range from 2 million years to 12.6 billion years. A comparison of the total kinematic samples of magnetics and DA stars over the same luminosity range 10.0near miss'' pulsar progenitors. We find preliminary evidence that the magnetic white dwarfs show a peculiar distribution in UV velocity space relative to other spectroscopic subgroups of white dwarfs. However, there is little evidence of a difference in velocity dispersion among the hot and cool magnetic degenerates, despite their having vastly different cooling ages. This may be taken as indirect evidence that the magnetics represent a sample of mixed evolutionary progeny.

  9. Drivers of HI Turbulence in Dwarf Galaxies

    CERN Document Server

    Stilp, Adrienne M; Skillman, Evan D; Warren, Steven R; Ott, Juergen; Koribalski, Baerbel

    2013-01-01

    Neutral hydrogen (HI) velocity dispersions are believed to be set by turbulence in the interstellar medium (ISM). Although turbulence is widely believed to be driven by star formation (SF), recent studies have shown that this driving mechanism may not be dominant in regions of low SF rate surface density (SFRSD), such as found in dwarf galaxies or the outer regions of spirals. We have generated average HI line profiles in a number of nearby dwarfs and low-mass spirals by co-adding HI spectra in regions with either a common radius or SFRSD. We find that the spatially-resolved superprofiles are composed of a central narrow peak (5-15 km/s) with higher velocity wings to either side. With the assumption that the central peak reflects the turbulent velocity dispersion, we compare HI kinematics to local ISM properties, including surface mass densities and measures of SF. The HI velocity dispersion is correlated most strongly with surface mass density, which points at a gravitational origin for turbulence, but it is...

  10. A Magellanic origin of the DES dwarfs

    Science.gov (United States)

    Jethwa, P.; Erkal, D.; Belokurov, V.

    2016-09-01

    We establish the connection between the Magellanic Clouds (MCs) and the dwarf galaxy candidates discovered in the Dark Energy Survey (DES) by building a dynamical model of the MC satellite populations, based on an extensive suite of tailor-made numerical simulations. Our model takes into account the response of the Galaxy to the MCs infall, the dynamical friction experienced by the MCs and the disruption of the MC satellites by their hosts. The simulation suite samples over the uncertainties in the MC's proper motions, the masses of the MW and the Clouds themselves, and allows for flexibility in the intrinsic volume density distribution of the MC satellites. As a result, we can accurately reproduce the DES satellites' observed positions and kinematics. Assuming that Milky Way (MW) dwarfs follow the distribution of sub-haloes in Λ cold dark matter, we further demonstrate that, of 14 observed satellites, the MW halo contributes fewer than 4(8) of these with 68(95) per cent confidence and that 7(12) DES dwarfs have probabilities greater than 0.7(0.5) of belonging to the Large Magellanic Cloud (LMC). Marginalizing over the entire suite, we constrain the number of Magellanic satellites in the range -7 < MV < -1 which exceed the DES surface brightness threshold at ˜70, and the mass of the LMC around 1011 M⊙. The data also strongly support a first-infall scenario for the LMC. Finally, we give predictions for the line-of-sight velocities and the proper motions of the satellites discovered in the vicinity of the LMC.

  11. A 3D kinematic estimation of knee prosthesis using X-ray projection images: clinical assessment of the improved algorithm for fluoroscopy images.

    Science.gov (United States)

    Hirokawa, Shunji; Abrar Hossain, M; Kihara, Yuichi; Ariyoshi, Shogo

    2008-12-01

    In this paper, we propose three ideas to improve a kinematic estimation algorithm for total knee arthroplasty. The first is a two-step estimation algorithm that improves estimation accuracy by excluding certain assumptions needed for the pattern matching algorithm reported by Banks and Hodge. The second is incorporating a 3D geometric articulation model into the algorithm to improve estimation accuracy substantially for the depth translation, and to introduce contact points' trajectories between the articular surfaces. The third is an algorithm to process estimation even when the silhouettes of two components overlap. To assess our algorithm's potential for clinical application, we carried out two experiments. First, we used a robot to position the prosthesis. Estimation accuracy was checked by comparing input data to the robot with the estimates from X-ray photographs. Incorporating our articulation model remarkably reduced the error in the depth translation. Next, we performed a clinical assessment by applying the algorithm and articulation model to fluoroscopy images of a patient who had recently had TKA.

  12. The white dwarf luminosity function

    Science.gov (United States)

    García-Berro, Enrique; Oswalt, Terry D.

    2016-06-01

    White dwarfs are the final remnants of low- and intermediate-mass stars. Their evolution is essentially a cooling process that lasts for ∼ 10 Gyr. Their observed properties provide information about the history of the Galaxy, its dark matter content and a host of other interesting astrophysical problems. Examples of these include an independent determination of the past history of the local star formation rate, identification of the objects responsible for the reported microlensing events, constraints on the rate of change of the gravitational constant, and upper limits to the mass of weakly interacting massive particles. To carry on these tasks the essential observational tools are the luminosity and mass functions of white dwarfs, whereas the theoretical tools are the evolutionary sequences of white dwarf progenitors, and the corresponding white dwarf cooling sequences. In particular, the observed white dwarf luminosity function is the key manifestation of the white dwarf cooling theory, although other relevant ingredients are needed to compare theory and observations. In this review we summarize the recent attempts to empirically determine the white dwarf luminosity function for the different Galactic populations. We also discuss the biases that may affect its interpretation. Finally, we elaborate on the theoretical ingredients needed to model the white dwarf luminosity function, paying special attention to the remaining uncertainties, and we comment on some applications of the white dwarf cooling theory. Astrophysical problems for which white dwarf stars may provide useful leverage in the near future are also discussed.

  13. M Dwarf Mysteries

    Science.gov (United States)

    Henry, Todd J.; Jao, Wei-Chun; Irwin, Jonathan; Dieterich, Sergio; Finch, Charlie T.; Riedel, Adric R.; Subasavage, John P.; Winters, Jennifer; RECONS Team

    2017-01-01

    During RECONS' 17-year (so far) astrometry/photometry program at the CTIO/SMARTS 0.9m, we have observed thousands of the ubiquitous red dwarfs in the solar neighborhood. During this reconnaissance, a few mysterious characters have emerged ...The Case of the Mercurial Stars: One M dwarf has been fading steadily for more than a decade, at last measure 6% fainter than when it was first observed. Another has grown brighter by 7% over 15 years. Are these brightness changes part of extremely long stellar cycles, or something else entirely?The Case of Identical Stellar Twins that Aren't: Two M dwarfs seem at first to be identical siblings traveling together through the Galaxy. They have virtually identical spectra at optical wavelengths and identical colors throughout the VRIJHK bands. Long-term astrometry indicates that they are, indeed, at the same distance via parallax measurements, and their proper motions match precisely. Yet, one of the twins is FOUR times brighter than the other. Followup work has revealed that the brighter component is a very close spectroscopic double, but no other stars are seen. So, the mystery may be half solved, but why do the close stars remain twice as bright as their widely-separated twin?The Case of the Great Kaboom!: After more than 1000 nights of observing on the reliable 0.9m telescope, with generally routine frames reading out upon the screen, one stellar system comprised of five red dwarfs flared in stunning fashion. Of the two distinct sources, the fainter one (an unresolved double) surpassed the brightness of the brighter one (an unresolved triple), increasing by more than three full magnitudes in the V filter. Which component actually flared? Is this magnificent outburst an unusual event, or in fact typical for this system and other M dwarfs?At the AAS meeting, we hope to probe the cognoscenti who study the Sun's smaller cousins to solve these intriguing M Dwarf Mysteries.This effort has been supported by the NSF through grants

  14. On the Assembly of Dwarf Galaxies in Clusters and their Efficient Formation of Globular Clusters

    CERN Document Server

    Mistani, Pouria A; Pillepich, Annalisa; Sanchez-Janssen, Ruben; Vogelsberger, Mark; Nelson, Dylan; Rodriguez-Gomez, Vicente; Torrey, Paul; Hernquist, Lars

    2015-01-01

    Galaxy clusters contain a large population of low mass dwarf elliptical galaxies whose exact origin is unclear: their colors, structural properties and kinematics differ substantially from those of dwarf irregulars in the field. We use the Illustris cosmological simulation to study differences in the assembly paths of dwarf galaxies (3e8 < M_*/M_sun < 1e10) according to their environment. We find that cluster dwarfs achieve their maximum total and stellar mass on average ~ 8 and ~ 4.5 Gyr ago, respectively, around the time of infall into the clusters. In contrast, field dwarfs not subjected to environmental stripping, reach their maximum mass at redshift z = 0. This different assembly history naturally produces a color bimodality, with blue isolated dwarfs and redder cluster dwarfs exhibiting negligible star-formation today. The cessation of star formation happens over median times 3.5-5 Gyr depending on stellar mass, and shows a large scatter (~ 1-8 Gyr), with the lower values associated with starburst...

  15. Population Properties of Brown Dwarf Analogs to Exoplanets

    CERN Document Server

    Faherty, Jacqueline K; Cruz, Kelle L; Gagne, Jonathan; Filippazzo, Joseph C; Lambrides, Erini; Fica, Haley; Weinberger, Alycia; Thorstensen, John R; Tinney, C G; Baldassare, Vivienne; Lemonier, Emily; Rice, Emily L

    2016-01-01

    We present a kinematic analysis of 152 low surface gravity M7-L8 dwarfs by adding 8 parallaxes, 38 radial velocities, and 19 proper motions. We find 39 objects to be high-likelihood or bona fide members of nearby moving groups, 92 objects to be ambiguous members and 21 objects that are non-members. We find that gravity classification and photometric color separate 5-150 Myr sources from > 3 Gyr field objects, but they do not correlate one-to-one with the narrower 5 -150 Myr age range. The absolute magnitudes of low-gravity sources from J band through W3 show a flux redistribution when compared to equivalent field sources that is correlated with spectral subtype. Clouds, which are a far more dominant opacity source for L dwarfs, are the likely cause. On CMDs, the latest-type low-gravity L dwarfs drive the elbow of the L/T transition up to 1 mag redder and 1 mag fainter than field dwarfs at M_J but are consistent with or brighter than the elbow at M_W1 and M_W2. Furthermore, there is an indication on CMD's (suc...

  16. An All-Sky Catalog of Bright M Dwarfs

    CERN Document Server

    Lépine, Sébastien

    2011-01-01

    We present an all-sky catalog of M dwarf stars with apparent infrared magnitude J40 mas/yr, supplemented on the bright end with the TYCHO-2 catalog. Completeness tests which account for kinematic (proper motion) bias suggest that our catalog represents ~75% of the estimated ~11,900 M dwarfs with J<10 expected to populate the entire sky. Our catalog is, however, significantly more complete for the Northern sky (~90%) than it is for the South (~60%). Stars are identified as cool, red M dwarfs from a combination of optical and infrared color cuts, and are distinguished from background M giants and highly-reddened stars using either existing parallax measurements or, if such measurements are lacking, on their location in an optical-to-infrared reduced proper motion diagram. These bright M dwarfs are all prime targets for exoplanet surveys using the Doppler radial velocity or transit methods; the combination of low-mass and bright apparent magnitude should make possible the detection of Earth-size planets on sh...

  17. Missing dark matter in dwarf galaxies?

    CERN Document Server

    Oman, Kyle A; Sales, Laura V; Fattahi, Azadeh; Frenk, Carlos S; Sawala, Till; Schaller, Matthieu; White, Simon D M

    2016-01-01

    We use cosmological hydrodynamical simulations of the APOSTLE project to examine the fraction of baryons in $\\Lambda$CDM haloes that collect into galaxies. This `galaxy formation efficiency' correlates strongly and with little scatter with halo mass, dropping steadily towards dwarf galaxies. The baryonic mass of a galaxy may thus be used to place a lower limit on total halo mass and, consequently, on its asymptotic maximum circular velocity. A number of dwarfs seem to violate this constraint, having baryonic masses up to ten times higher than expected from their rotation speeds, or, alternatively, rotating at only half the speed expected for their mass. Taking the data at face value, either these systems have formed galaxies with extraordinary efficiency - highly unlikely given their shallow potential wells - or they inhabit haloes with extreme deficits in their dark matter content. This `missing dark matter' is reminiscent of the inner mass deficits of galaxies with slowly-rising rotation curves, but extends...

  18. The white dwarf luminosity function

    CERN Document Server

    García-Berro, Enrique

    2016-01-01

    White dwarfs are the final remnants of low- and intermediate-mass stars. Their evolution is essentially a cooling process that lasts for $\\sim 10$ Gyr. Their observed properties provide information about the history of the Galaxy, its dark matter content and a host of other interesting astrophysical problems. Examples of these include an independent determination of the past history of the local star formation rate, identification of the objects responsible for the reported microlensing events, constraints on the rate of change of the gravitational constant, and upper limits to the mass of weakly interacting massive particles. To carry on these tasks the essential observational tools are the luminosity and mass functions of white dwarfs, whereas the theoretical tools are the evolutionary sequences of white dwarf progenitors, and the corresponding white dwarf cooling sequences. In particular, the observed white dwarf luminosity function is the key manifestation of the white dwarf cooling theory, although other...

  19. Dwarf Spheroidals in MOND

    CERN Document Server

    Angus, Garry W

    2008-01-01

    We take the line of sight velocity dispersions as functions of radius for 8 Milky Way dwarf spheroidal galaxies and use Jeans analysis to calculate the mass-to-light ratios (M/L) in Modified Newtonian Dynamics (MOND). Using the latest structural parameters, distances and variable velocity anisotropy, we find 6/8 dwarfs have sensible M/L using only the stellar populations. Sextans and Draco, however, have M/L=9.2_{-3.0}^{+5.3} and 43.9_{-19.3}^{+29.0} respectively, which poses a problem. Apart from the need for Sextans' integrated magnitude to be reviewed, we propose tidal effects intrinsic to MOND, testable with numerical simulations, but fully orbit dependant, which are disrupting Draco. The creation of the Magellanic Stream is also re-addressed in MOND, the scenario being the stream is ram pressure stripped from the SMC as it crosses the LMC.

  20. Searching for Brown Dwarf Outflows

    CERN Document Server

    Whelan, E T; Bacciotti, F; Randich, S; Natta, A

    2009-01-01

    As outflow activity in low mass protostars is strongly connected to ac- cretion it is reasonable to expect accreting brown dwarfs to also be driving out- flows. In the last three years we have searched for brown dwarf outflows using high quality optical spectra obtained with UVES on the VLT and the technique of spectro-astrometry. To date five brown dwarf outflows have been discovered. Here the method is discussed and the results to date outlined.

  1. Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites

    Science.gov (United States)

    Wheeler, Coral Rose

    2016-06-01

    The high dark matter content and the shallow potential wells of low mass galaxies (10^3 Msun 10 Gyr), having had their star formation shut down by reionization. Additionally, we show that the kinematics and ellipticities of isolated simulated dwarf centrals are consistent with observed dSphs satellites without the need for harassment from a massive host. We further show that most (but not all) observed *isolated* dIrrs in the Local Volume also have dispersion-supported stellar populations, contradicting the previous view that these objects are rotating. Finally, we investigate the stellar age gradients in dwarfs — showing that early mergers and strong feedback can create an inverted gradient, with the older stars occupying larger galactocentric radii.These results offer an interesting direction in testing models that attempt to solve dark matter problems via explosive feedback episodes. Can the same models that create large cores in simulated dwarfs preserve the mild stellar rotation that is seen in a minority of isolated dIrrs? Can the bursty star formation that created a dark matter core also match observed stellar gradients in low mass galaxies? Comparisons between our simulations and observed dwarfs should provide an important benchmark for this question going forward.

  2. Dwarf Dark Matter Halos

    CERN Document Server

    Colin, Pierre; Valenzuela, O; Gottlöber, S

    2003-01-01

    We use N-body simulations to study properties of dwarf halos with virial masses in the range 10^7-10^9 Msun/h. Unlike recent reported results, we find that the density profiles of relaxed dwarf halos are well fitted by the NFW profile and do not have cores. We estimate the distribution of concentrations for halos in mass range that covers six orders of magnitude from 10^7 Msun/h to 10^13 Msun/h, and find that the data are well reproduced by the model of Bullock et al. (2001). We predict that present-day isolated dwarf halos should have a very large median concentration of ~ 35. For halos with masses that range from 4.6 x 10^9 Msun/h to 10^13 Msun/h we measure the subhalo circular velocity function and find that they are similar when normalized to the circular velocity of the parent halo. We compute the halo mass function and the halo spin parameter distribution and find that the former is very well reproduced by the Sheth and Tormen model while the latter is well fitted by a lognormal distribution with lambda...

  3. Population Properties of Brown Dwarf Analogs to Exoplanets

    Science.gov (United States)

    Faherty, Jacqueline K.; Riedel, Adric R.; Cruz, Kelle L.; Gagne, Jonathan; Filippazzo, Joseph C.; Lambrides, Erini; Fica, Haley; Weinberger, Alycia; Thorstensen, John R.; Tinney, C. G.; Baldassare, Vivienne; Lemonier, Emily; Rice, Emily L.

    2016-07-01

    We present a kinematic analysis of 152 low surface gravity M7-L8 dwarfs by adding 18 new parallaxes (including 10 for comparative field objects), 38 new radial velocities, and 19 new proper motions. We also add low- or moderate-resolution near-infrared spectra for 43 sources confirming their low surface gravity features. Among the full sample, we find 39 objects to be high-likelihood or new bona fide members of nearby moving groups, 92 objects to be ambiguous members and 21 objects that are non-members. Using this age-calibrated sample, we investigate trends in gravity classification, photometric color, absolute magnitude, color-magnitude, luminosity, and effective temperature. We find that gravity classification and photometric color clearly separate 5-130 Myr sources from >3 Gyr field objects, but they do not correlate one to one with the narrower 5-130 Myr age range. Sources with the same spectral subtype in the same group have systematically redder colors, but they are distributed between 1 and 4σ from the field sequences and the most extreme outlier switches between intermediate- and low-gravity sources either confirmed in a group or not. The absolute magnitudes of low-gravity sources from the J band through W3 show a flux redistribution when compared to equivalently typed field brown dwarfs that is correlated with spectral subtype. Low-gravity, late-type L dwarfs are fainter at J than the field sequence but brighter by W3. Low-gravity M dwarfs are >1 mag brighter than field dwarfs in all bands from J through W3. Clouds, which are a far more dominant opacity source for L dwarfs, are the likely cause. On color-magnitude diagrams, the latest-type, low-gravity L dwarfs drive the elbow of the L/T transition up to 1 mag redder and 1 mag fainter than field dwarfs at M J but are consistent with or brighter than the elbow at M W1 and M W2. We conclude that low-gravity dwarfs carry an extreme version of the cloud conditions of field objects to lower temperatures

  4. OGLE-2005-BLG-071Lb, the Most Massive M-Dwarf Planetary Companion?

    Energy Technology Data Exchange (ETDEWEB)

    Dong, S; Gould, A; Udalski, A; Anderson, J; Christie, G W; Gaudi, B S; Jaroszynski, M; Kubiak, M; Szymanski, M K; Pietrzynski, G; Soszynski, I; Szewczyk, O; Ulaczyk, K; Wyrzykowski, L; DePoy, D L; Fox, D B; Gal-Yam, A; Han, C; Lepine, S; McCormick, J; Ofek, E; Park, B; Pogge, R W; Abe, F; Bennett, D P; Bond, I A; Britton, T R; Gilmore, A C; Hearnshaw, J B; Itow, Y; Kamiya, K; Kilmartin, P M; Korpela, A; Masuda, K; Matsubara, Y; Motomura, M; Muraki, Y; Nakamura, S; Ohnishi, K; Okada, C; Rattenbury, N; Saito, T; Sako, T; Sasaki, M; Sullivan, D; Sumi, T; Tristram, P J; Yanagisawa, T; Yock, P M; Yoshoika, T; Albrow, M D; Beaulieu, J P; Brillant, S; Calitz, H; Cassan, A; Cook, K H; Coutures, C; Dieters, S; Prester, D D; Donatowicz, J; Fouque, P; Greenhill, J; Hill, K; Hoffman, M; Horne, K; J?rgensen, U G; Kane, S; Kubas, D; Marquette, J B; Martin, R; Meintjes, P; Menzies, J; Pollard, K R; Sahu, K C; Vinter, C; Wambsganss, J; Williams, A; Bode, M; Bramich, D M; Burgdorf, M; Snodgrass, C; Steele, I; Doublier, V; Foelmi, C

    2008-04-18

    We combine all available information to constrain the nature of OGLE-2005-BLG-071Lb, the second planet discovered by microlensing and the first in a high-magnification event. These include photometric and astrometric measurements from Hubble Space Telescope, as well as constraints from higher-order effects extracted from the ground-based light curve, such as microlens parallax, planetary orbital motion and finite-source effects. Our primary analysis leads to the conclusion that the host of Jovian planet OGLE-2005-BLG-071Lb is a foreground M dwarf, with mass M = 0.46 {+-} 0.04M{sub {circle_dot}}, distance D{sub l} = 3.3 {+-} 0.4 kpc, and thick-disk kinematics {nu}{sub LSR} {approx} 103 km s{sup -1}. From the best-fit model, the planet has mass M{sub p} = 3.5 {+-} 0.3 M{sub Jupiter}, lies at a projected separation r{sub {perpendicular}} = 3.6 {+-} 0.2 AU from its host and has an equilibrium temperature of T {approx} 50 K, i.e., similar to Neptune. A degenerate model less favored by {Delta}{sub {chi}}{sup 2} {approx} 4 gives essentially the same planetary mass M{sub p} = 3.3 {+-} 0.3 M{sub Jupiter} with a smaller projected separation, r{sub {perpendicular}} = 2.1 {+-} 0.1 AU, and higher equilibrium temperature T {approx} 68 K. These results from the primary analysis suggest that OGLE-2005-BLG-071Lb is likely to be the most massive planet yet discovered that is hosted by an M dwarf. However, the formation of such high-mass planetary companions in the outer regions of M-dwarf planetary systems is predicted to be unlikely within the core-accretion scenario. There are a number of caveats to this analysis, but these could mostly be resolved by a single astrometric measurement a few years after the event.

  5. Morphology of Dwarf Galaxies in Isolated Satellite Systems

    Science.gov (United States)

    Ann, Hong Bae

    2017-08-01

    The environmental dependence of the morphology of dwarf galaxies in isolated satellite systems is analyzed to understand the origin of the dwarf galaxy morphology using the visually classified morphological types of 5836 local galaxies with z ≲ 0.01. We consider six sub-types of dwarf galaxies, dS0, dE, dE_{bc}, dSph, dE_{blue}, and dI, of which the first four sub-types are considered as early-type and the last two as late-type. The environmental parameters we consider are the projected distance from the host galaxy (r_{p}), local and global background densities, and the host morphology. The spatial distributions of dwarf satellites of early-type galaxies are much different from those of dwarf satellites of late-type galaxies, suggesting the host morphology combined with r_{p} plays a decisive role on the morphology of the dwarf satellite galaxies. The local and global background densities play no significant role on the morphology of dwarfs in the satellite systems hosted by early-type galaxies. However, in the satellite system hosted by late-type galaxies, the global background densities of dE and dSph satellites are significantly different from those of dE_{bc}, dE_{blue}, and dI satellites. The blue-cored dwarf satellites (dE_{bc}) of early-type galaxies are likely to be located at r_{p} > 0.3 Mpc to keep their cold gas from the ram pressure stripping by the hot corona of early-type galaxies. The spatial distribution of dE_{bc} satellites of early-type galaxies and their global background densities suggest that their cold gas is intergalactic material accreted before they fall into the satellite systems.

  6. The Modular Robots Kinematics

    Directory of Open Access Journals (Sweden)

    Claudiu Pozna

    2007-08-01

    Full Text Available The present paper intention is to develop a kinematical foundation for our nextworks in industrial robots (IR modular design. The goal of this works is todevelop cheap and improved robots which are adapted to the costumer needs. Inorder to achieve the mentioned goal, in [43], we have started a bibliographicalresearch of the main modular design aspects. The mentioned analyze of the actualresults in modular robots design gives us the possibility to establish our researchprogram. The idea of this paper is to develop a kinematical formalism which willbe use in the next dedicated to this subject.

  7. Qualitative Kinematics of Linkages

    Science.gov (United States)

    1990-05-01

    links and the connections between them, the following algorithm computes an envisionment for that system . lotatioa(P1,P2) - CCV lotatioa(P1,P2) CCV...1988 Appendix A : Slider-Crank Envisionment Each qualitative state consists of a kinematic state representing the orientation of each link, and a...8 +++ 6 -- . f. 6 000 , 7 --0 7 ++0 8 +- -+ > 1 000 1 +0+ 8 000 8 000 7 --0 7 000 8 --- m 8 +++ Appendix B : Drag-Link Envisionment Kinematic State

  8. Kinematical Clues to the Origin of the Virgo Stellar Stream

    Science.gov (United States)

    Yam, William; Carlin, J. L.; Casetti-Dinescu, D. I.; Willett, B. A.; Newberg, H.; Majewski, S. R.; Girard, T. M.

    2012-01-01

    Milky Way stellar substructure has been detected in the Virgo constellation (the so-called Virgo Stellar Stream, or VSS; and the possibly associated Virgo Overdensity) using a variety of different stellar tracers over a large (perhaps 100-1000 square degrees) area of sky, but the nature of the overdensities has yet to be determined. Fortuitously, one of Kapteyn's Selected Areas (SAs) making up our deep proper motion survey (Casetti-Dinescu et al. 2006) intersects this structure. Our data in this field, denoted SA 103, span 40x40 arcminutes centered at (RA, Dec) = (178.8, -0.6). We supplemented our proper motions with multifiber spectroscopy. VSS members are selected via kinematics (radial velocities and proper motions), as well as position on the CMD. Theoretical isochrones were fitted to the identified members in the CMD to obtain distance. We find 14 candidates with properties consistent with membership in the VSS (based in part on comparison to previous detections), and use the mean 3-D kinematics of these members to derive an orbit for the VSS debris. We show that Virgo debris is near the pericenter of a high-eccentricity, plunging orbit similar to that found by Casetti-Dinescu et al. (2009) based on one VSS RR-Lyrae star. We explore possible progenitors for the VSS by integrating an orbit with the measured kinematics and comparing this to known Milky Way satellites and stellar substructures. At least three structures (a dwarf galaxy, globular cluster, and at least one diffuse stellar overdensity) are identified whose properties suggest that they may be related to the VSS. An n-body simulation of a Sagittarius-sized dwarf galaxy on our derived orbit produces a remnant with similar properties to the extant VSS detections, supporting the idea that the VSS is the remains of a tidally disrupted dwarf galaxy. Supported by NSF grants AST 09-37523, AST 11-15146, AST 10-09670.

  9. Teaching about Kinematics

    Science.gov (United States)

    Nelson, Jane Bray; Nelson, Jim

    2009-01-01

    Written by Jim and Jane Nelson, Teaching About Kinematics is the latest AAPT/PTRA resource book. Based on physics education research, the book provides teachers with the resources needed to introduce students to some of the fundamental building blocks of physics. It is a carefully thought-out, step-by-step laboratory-based introduction to the…

  10. Axion cooling of white dwarfs

    CERN Document Server

    Isern, J; Garcia--Berro, E; Salaris, M; Torres, S

    2013-01-01

    The evolution of white dwarfs is a simple gravothermal process. This process can be tested in two ways, through the luminosity function of these stars and through the secular variation of the period of pulsation of those stars that are variable. Here we show how the mass of the axion can be constrained using the white dwarf luminosity function.

  11. Hot C-rich white dwarfs: testing the DB-DQ transition through pulsations

    CERN Document Server

    Córsico, A H; Althaus, L G; García-Berro, E

    2009-01-01

    Hot DQ white dwarfs constitute a new class of white dwarf stars, uncovered recently within the framework of the SDSS project. Recently, three hot DQ white dwarfs have been reported to exhibit photometric variability with periods compatible with pulsation g-modes. Here, we present a nonadiabatic pulsation analysis of the recently discovered carbon-rich hot DQ white dwarf stars. One of our main aims is to test the convective-mixing picture for the origin of hot DQs through the pulsational properties. Our study relies on the full evolutionary models of hot DQ white dwarfs recently developed by Althaus et al. (2009), that consistently cover the whole evolution from the born-again stage to the white dwarf cooling track. Specifically, we present a stability analysis of white dwarf models from stages before the blue edge of the DBV instability strip until the domain of the hot DQ white dwarfs, including the transition DB --> hot DQ white dwarf. We found that at evolutionary phases in which the models are characteriz...

  12. A Very Cool Pair of Brown Dwarfs

    Science.gov (United States)

    2011-03-01

    determine the distance to the brown dwarfs. More information This research was presented in a paper, "CFBDSIR J1458+1013B: A Very Cold (>T10) Brown Dwarf in a Binary System", Liu et al. to appear in the Astrophysical Journal. The team is composed of Michael C. Liu (Institute for Astronomy [IfA], University of Hawaii, USA), Philippe Delorme (Institut de planétologie et d'astrophysique de Grenoble, CNRS/Université Joseph Fourier, France [IPAG]), Trent J. Dupuy (Harvard-Smithsonian Center for Astrophysics, Cambridge, USA), Brendan P. Bowler (IfA), Loic Albert (Canada-France-Hawaii Telescope Corporation, Hawaii, USA), Etienne Artigau (Université de Montréal, Canada), Celine Reylé (Observatoire de Besançon, France), Thierry Forveille (IPAG) and Xavier Delfosse (IPAG). 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 15 countries: Austria, Belgium, Brazil, 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".

  13. Tracing kinematic (mis)alignments in CALIFA merging galaxies: Stellar and ionized gas kinematic orientations at every merger stage

    CERN Document Server

    Barrera-Ballesteros, J K; Falcón-Barroso, J; van de Ven, G; Lyubenova, M; Wild, V; Méndez-Abreu, J; Sánchez, S F; Marquez, I; Masegosa, J; Monreal-Ibero, A; Ziegler, B; del Olmo, A; Verdes-Montenegro, L; García-Benito, R; Husemann, B; Mast, D; Kehrig, C; Iglesias-Paramo, J; Marino, R A; Aguerri, J A L; Walcher, C J; Vílchez, J M; Bomans, D J; Cortijo-Ferrero, C; Delgado, R M González; Bland-Hawthorn, J; McIntosh, D H; Bekeraite, Simona

    2015-01-01

    We present spatially resolved stellar and/or ionized gas kinematic properties for a sample of 103 interacting galaxies, tracing all merger stages: close companions, pairs with morphological signatures of interaction, and coalesced merger remnants. We compare our sample with 80 non-interacting galaxies. We measure for the stellar and the ionized gas components the major (projected) kinematic position angles (PA$_{\\mathrm{kin}}$, approaching and receding) directly from the velocity fields with no assumptions on the internal motions. This method allow us to derive the deviations of the kinematic PAs from a straight line ($\\delta$PA$_{\\mathrm{kin}}$). Around half of the interacting objects show morpho-kinematic PA misalignments that cannot be found in the control sample. Those misalignments are present mostly in galaxies with morphological signatures of interaction. Alignment between the kinematic sides for both samples is similar, with most of the galaxies displaying small misalignments. Radial deviations of the...

  14. WISE Y Dwarfs As Probes of the Brown Dwarf-Exoplanet Connection

    CERN Document Server

    Beichman, C; Kirkpatrick, J Davy; Cushing, Michael C; Dodson-Robinson, Sally; Marley, Mark S; Morley, Caroline V; Wright, E L

    2014-01-01

    We have determined astrometric positions for 15 WISE-discovered late-type brown dwarfs (6 T8-9 and 9 Y dwarfs) using the Keck II telescope, the Spitzer Space Telescope, and the Hubble Space Telescope. Combining data from 8 to 20 epochs we derive parallactic and proper motions for these objects which put the majority within 15 parsecs. For ages greater than a few Gyr, as suggested from kinematic considerations, we find masses of 10-30 M$_{Jup}$ based on standard models for the evolution of low mass objects with a range of mass estimates for individual objects depending on the model in question. Three of the coolest objects have effective temperatures $\\sim$ 350 K and inferred masses of 10-15 M$_{Jup}$. Our parallactic distances confirm earlier photometric estimates (Kirkpatrick et al. 2012) and direct measurements (Marsh et al. 2013, Beichman et al. 2013, Dupuy and Krauss 2013) and suggest that the number of objects with masses below about 15 M$_{Jup}$ must be flat or declining relative to higher mass objects....

  15. Habitability of planets around red dwarf stars.

    Science.gov (United States)

    Heath, M J; Doyle, L R; Joshi, M M; Haberle, R M

    1999-08-01

    Recent models indicate that relatively moderate climates could exist on Earth-sized planets in synchronous rotation around red dwarf stars. Investigation of the global water cycle, availability of photosynthetically active radiation in red dwarf sunlight, and the biological implications of stellar flares, which can be frequent for red dwarfs, suggests that higher plant habitability of red dwarf planets may be possible.

  16. Magnetized White Dwarfs

    CERN Document Server

    Terrero, D Alvear; Martínez, A Pérez

    2016-01-01

    The purpose of this thesis is to obtain more realistic equations of state to describe the matter forming magnetized white dwarfs, and use them to solve its structure equations. The equations of state are determined by considering the weak magnetic field approximation $Bdwarfs. Also, we consider the energy and pressure correction due to the Coulomb interaction of the electron gas with the ions located in a crystal lattice. Moreover, spherically symmetric Tolman-Oppenheimer-Volkoff structure equations are solved independently for the perpendicular and parallel pressures, confirming the necessity of using axisymmetric structure equations, more adequate to describe the anisotropic system. Therefore, we study the solutions in cylindrical coordinates. In this case, the mass per longitude unit is obtained instead of the total mass of the whit...

  17. The no-spin zone: rotation versus dispersion support in observed and simulated dwarf galaxies

    Science.gov (United States)

    Wheeler, Coral; Pace, Andrew B.; Bullock, James S.; Boylan-Kolchin, Michael; Oñorbe, Jose; Elbert, Oliver D.; Fitts, Alex; Hopkins, Philip F.; Kereš, Dušan

    2017-02-01

    We perform a systematic Bayesian analysis of rotation versus dispersion support (vrot/σ) in 40 dwarf galaxies throughout the local volume (LV) over a stellar mass range of 10^{3.5} M_{⊙}sample have vrot/σ ≲ 1.0, while all have vrot/σ ≲ 2.0. These results challenge the traditional view that the stars in gas-rich dwarf irregulars (dIrrs) are distributed in cold, rotationally supported stellar discs, while gas-poor dwarf spheroidals (dSphs) are kinematically distinct in having dispersion-supported stars. We see no clear trend between vrot/σ and distance to the closest L⋆ galaxy, nor between vrot/σ and M⋆ within our mass range. We apply the same Bayesian analysis to four FIRE hydrodynamic zoom-in simulations of isolated dwarf galaxies (10^9 M_{⊙}population of dIrrs and dSphs without the need to subject these dwarfs to any external perturbations or tidal forces. We posit that most dwarf galaxies form as puffy, dispersion-dominated systems, rather than cold, angular-momentum-supported discs. If this is the case, then transforming a dIrr into a dSph may require little more than removing its gas.

  18. Study of the nature of dark matter in halos of dwarf galaxies

    Science.gov (United States)

    Karmakar, Pradip; Chattopadhyay, Tanuka; Chattopadhyay, Asis Kumar

    2015-08-01

    The kinematics of dwarf galaxies are strongly influenced by dark matter down to small galactocentric radii. So they are good candidates to investigate the nature of Dark Matter. In the present work we have carried out mass modeling of a number of recently observed dwarf galaxies Swaters et al. in Astron. Astrophys. 493:871, 2009. We have used a Navarro-Frenk-White (NFW) halo, Freeman disc along with a gaseous disc for modeling the observed rotation curves of those dwarf galaxies. For comparison we also used a Burkert halo, Freeman disc and gaseous disc. For both the scenario we have performed Kolmogorov-Smirnov (KS) test between the observed and predicted rotational velocity profiles. The tests are rejected for NFW halo almost in 50 per cent cases but they are accepted almost for all cases for Burkert halo, preferring a Burkert halo model generally for dwarf galaxies. The above results reveal a constant density core of dark matter (DM) in the halos of dwarf galaxies compared to a cuspy nature of NFW halo and a possible challenge to -CDM scenario for the nature of dark matter in most of the dwarf galaxies.

  19. Throwing Icebergs at White Dwarfs

    Science.gov (United States)

    Kohler, Susanna

    2017-08-01

    Where do the metals come from that pollute the atmospheres of many white dwarfs? Close-in asteroids may not be the only culprits! A new study shows that distant planet-size and icy objects could share some of the blame.Pollution ProblemsArtists impression of rocky debris lying close around a white dwarf star. [NASA/ESA/STScI/G. Bacon]When a low- to intermediate-mass star reaches the end of its life, its outer layers are blown off, leaving behind its compact core. The strong gravity of this white dwarf causes elements heavier than hydrogen and helium to rapidly sink to its center in a process known as sedimentation, leaving an atmosphere that should be free of metallic elements.Therefore its perhaps surprising that roughly 2550% of all white dwarfs are observed to have atmospheric pollution by heavy elements. The short timescales for sedimentation suggest that these elements were added to the white dwarf recently but how did they get there?Bringing Ice InwardIn the generally accepted theory, pre-existing rocky bodies or an orbiting asteroid belt survive the stars evolution, later accreting onto the final white dwarf. But this scenario doesnt explain a few observations that suggest white dwarfs might be accreting larger planetary-size bodies and bodies with ices and volatile materials.Dynamical evolution of a Neptune-like planet (a) and a Kuiper belt analog object (b) in wide binary star systems. Both have large eccentricity excitations during the white dwarf phase. [Stephan et al. 2017]How might you get large or icy objects which would begin on very wide orbits close enough to a white dwarf to become disrupted and accrete? Led by Alexander Stephan, a team of scientists at UCLA now suggest that the key is for the white dwarf to be in a binary system.Influence of a CompanionIn the authors model, the white-dwarf progenitor is orbited by both a distant stellar companion (a common occurrence) and a number of large potential polluters, which could have masses between that

  20. PROPERTIES OF THE COOLEST DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    SAUMON, DIDIER [Los Alamos National Laboratory; LEGGETT, SANDY K. [NON LANL; FREEDMAN, RICHARD S. [NON LANL; GEBALLE, THOMAS R. [NON LANL; GOLIMOWSKI, DAVID A. [NON LANL; LODIEU, NICOLAS [NON LANL; MARLEY, MARK S. [NON LANL; STEPHENS, DENISE [NON LANL; PINFIELD, DAVID J. [NON LANL; WARREN, STEPHEN J. [NON LANL

    2007-01-18

    Eleven years after the discovery of the first T dwarf, we have a population of ultracool L and T dwarfs that is large enough to show a range of atmospheric properties, as well as model atmospheres advanced enough to study these properties in detail. Since the last Cool Stars meeting, there have been observational developments which aid in these studies. they present recent mid-infrared photometry and spectroscopy from the Spitzer Space Telescope which confirms the prevalence of vertical mixing in the atmospheres of L and T dwarfs. Hence, the 700 K to 2200 K L and t dwarf photspheres require a large number of parameters for successful modeling: effective temperature, gravity, metallicity, grain sedimentation and vertical mixing efficiency. They also describe initial results of a search for ultracool dwarfs in the UKIRT Infrared Deep Sky Survey, and present the latest T dwarf found to date. They conclude with a discussion of the definition of the later-than-T spectral type, the Y dwarf.

  1. HADES RV Programme with HARPS-N at TNG . III. Flux-flux and activity-rotation relationships of early-M dwarfs

    Science.gov (United States)

    Maldonado, J.; Scandariato, G.; Stelzer, B.; Biazzo, K.; Lanza, A. F.; Maggio, A.; Micela, G.; González-Álvarez, E.; Affer, L.; Claudi, R. U.; Cosentino, R.; Damasso, M.; Desidera, S.; González Hernández, J. I.; Gratton, R.; Leto, G.; Messina, S.; Molinari, E.; Pagano, I.; Perger, M.; Piotto, G.; Rebolo, R.; Ribas, I.; Sozzetti, A.; Suárez Mascareño, A.; Zanmar Sanchez, R.

    2017-01-01

    Context. Understanding stellar activity in M dwarfs is crucial for the physics of stellar atmospheres and for ongoing radial velocity exoplanet programmes. Despite the increasing interest in M dwarfs, our knowledge of the chromospheres of these stars is far from being complete. Aims: We test whether the relations between activity, rotation, and stellar parameters and flux-flux relationships previously investigated for main-sequence FGK stars and for pre-main-sequence M stars also hold for early-M dwarfs on the main-sequence. Although several attempts have been made so far, here we analyse a large sample of stars undergoing relatively low activity. Methods: We analyse in a homogeneous and coherent way a well-defined sample of 71 late-K/early-M dwarfs that are currently being observed in the framework of the HArps-N red Dwarf Exoplanet Survey (HADES). Rotational velocities are derived using the cross-correlation technique, while emission flux excesses in the Ca ii H & K and Balmer lines from Hα up to Hɛ are obtained by using the spectral subtraction technique. The relationships between the emission excesses and the stellar parameters (projected rotational velocity, effective temperature, kinematics, and age) are studied. Relations between pairs of fluxes of different chromospheric lines (flux-flux relationships) are also studied and compared with the literature results for other samples of stars. Results: We find that the strength of the chromospheric emission in the Ca ii H & K and Balmer lines is roughly constant for stars in the M0-M3 spectral range. Although our sample is likely to be biased towards inactive stars, our data suggest that a moderate but significant correlation between activity and rotation might be present, as well as a hint of kinematically selected young stars showing higher levels of emission in the calcium line and in most of the Balmer lines. We find our sample of M dwarfs to be complementary in terms of chromospheric and X-ray fluxes with

  2. Dark matter inner slope and concentration in galaxies: from the Fornax dwarf to M87

    CERN Document Server

    Mamon, G A; Romanowsky, A J; Wojtak, R

    2014-01-01

    We apply two new state-of-the-art methods that model the distribution of observed tracers in projected phase space to lift the mass / velocity anisotropy (VA) degeneracy and deduce constraints on the mass profiles of galaxies, as well as their VA. We first show how a distribution function based method applied to the satellite kinematics of otherwise isolated SDSS galaxies shows convincing observational evidence of age matching: red galaxies have more concentrated dark matter (DM) halos than blue galaxies of the same stellar or halo mass. Then, applying the MAMPOSSt technique to M87 (traced by its red and blue globular clusters) we find that very cuspy DM is favored, unless we release priors on DM concentration or stellar mass (leading to unconstrained slope). For the Fornax dwarf spheroidal (traced by its metal-rich and metal-poor stars), the inner DM slope is unconstrained, with weak evidence for a core if the stellar mass is fixed. This highlights how priors are crucial for DM modeling. Finally, we find tha...

  3. Blasting away a dwarf galaxy: The "tail" of ESO 324-G024

    CERN Document Server

    Johnson, Megan C; Koribalski, Baerbel S; Wang, Jing; Oh, Se-Heon; Hil, Alex; O'Sullivan, Shane; Haan, Sebastian; Serra, Paolo

    2015-01-01

    We present Australia Telescope Compact Array radio data of the dwarf irregular galaxy ESO 324-G024 which is seen in projection against the giant, northern lobe of the radio galaxy Centaurus A (Cen A, NGC 5128). The distorted morphology and kinematics of ESO 324-G024, as observed in the 21 cm spectral line emission of neutral hydrogen, indicate disruptions by external forces. We investigate whether tidal interactions and/or ram pressure stripping are responsible for the formation of the HI tail stretching to the northeast of ESO 324-G024 with the latter being most probable. Furthermore, we closely analyze the sub-structure of Cen A's polarized radio lobes to ascertain whether ESO 324-G024 is located in front, within or behind the northern lobe. Our multi-wavelength, multi-component approach allows us to determine that ESO 324-G024 is most likely behind the northern radio lobe of Cen A. This result helps to constrain the orientation of the lobe, which is likely inclined to our line of sight by approximately 60 ...

  4. Kinematic Stirling Engine Performance

    Science.gov (United States)

    Tew, J. R. C.

    1986-01-01

    Computer program developed for analyzing thermodynamic characteristics of kinematic Stirling engine. Computes time-varying piston positions, pressures, and gas temperatures in each of gas-control volumes into which engine working space is divided. Engine performance characterized by calculations of power and efficiency (both indicated and brake). Inputs to code are engine geometrical parameter, engine-operating conditions, and indexes that specify various options available.

  5. A Pulsar and White Dwarf in an Unexpected Orbit

    Science.gov (United States)

    Kohler, Susanna

    2016-11-01

    motion of the pulsar (black solid lines; current position marked with diamond) in our galaxy over the past 1.5 Gyr. This motion is typical for low-mass X-ray binary descendants, favoring a binary-evolution model over a 3-body-interaction model. [Antoniadis et al. 2016]In the first model, the eccentric binary was created via adynamic three-body formation channel. This possibility is deemed unlikely, as the white-dwarf properties and all the kinematic properties of the system point to normal binary evolution.In the secondmodel, the binary system gains its high eccentricity after mass transfer ends, when the pulsar progenitor experiences a spontaneous phase transition. The authors explore two options for this: one in which the neutron star implodes into a strange-quark star, and the other in which an over-massive white dwarf suffers a delayed collapse into a neutron star. Both cases are deemed unlikely, because the mass inferred for the pulsar progenitor is not consistent with either model.In the third model, the system forms a circumbinary disk fueled by material escaping the proto-white dwarf. After mass transfer has ended, interactions between the binary and its disk gradually increase the eccentricity of the system, pumping it up to what we observe today. All of the properties of the system measured by Antoniadis and collaborators are thus far consistent with this model.Further observations of this system and systems like it (several others have been detected, though not yet confirmed) will help determine whether binary evolution combined with interactions with a disk can indeed explain the formation of this unexpectedly eccentricsystem.CitationJohn Antoniadis et al 2016 ApJ 830 36. doi:10.3847/0004-637X/830/1/36

  6. Pluto and other dwarf planets

    CERN Document Server

    Saxena, Shalini

    2017-01-01

    The reclassification of Pluto in 2006 not only decreased the number of planets in our solar system by one but also introduced the new category of dwarf planet. Readers will come to understand what separates a dwarf planet from a planet-or for that matter from any of the other bodies found within the solar system. They'll learn about Pluto itself, as well as its fellow dwarf planets, Ceres, Makemake, Haumea, and Eris. Full of recent information, this title is sure to inspire an interest in space science among young readers.

  7. A New Benchmark Brown Dwarf

    CERN Document Server

    Tinney, C G; Forveille, T; Delfosse, Xavier

    1997-01-01

    We present optical spectroscopy of three brown dwarf candidates identified in the first 1% of the DENIS sky survey. Low resolution spectra from 6430--9000A show these objects to have similar spectra to the uncertain brown dwarf candidate GD 165B. High resolution spectroscopy shows that one of the objects -- DBD 1228-1547 -- has a strong EW=2.3+-0.05A absorption line of Li I 6708A, and is therefore a brown dwarf with mass below 0.065 Msol. DBD 1228-1547 can now be the considered proto-type for objects JUST below the hydrogen burning limit.

  8. Pan-Planets: Searching for hot Jupiters around cool dwarfs

    CERN Document Server

    Obermeier, C; Saglia, R P; Henning, Th; Bender, R; Kodric, M; Deacon, N; Riffeser, A; Burgett, W; Chambers, K C; Draper, P W; Flewelling, H; Hodapp, K W; Kaiser, N; Kudritzki, R -P; Magnier, E A; Metcalfe, N; Price, P A; Sweeney, W; Wainscoat, R J; Waters, C

    2015-01-01

    The Pan-Planets survey observed an area of 42 sq deg. in the galactic disk for about 165 hours. The main scientific goal of the project is the detection of transiting planets around M dwarfs. We establish an efficient procedure for determining the stellar parameters $T_{eff}$ and log$g$ of all sources using a method based on SED fitting, utilizing a three-dimensional dust map and proper motion information. In this way we identify more than 60000 M dwarfs, which is by far the largest sample of low-mass stars observed in a transit survey to date. We present several planet candidates around M dwarfs and hotter stars that are currently being followed up. Using Monte-Carlo simulations we calculate the detection efficiency of the Pan-Planets survey for different stellar and planetary populations. We expect to find $3.0^{+3.3}_{-1.6}$ hot Jupiters around F, G, and K dwarfs with periods lower than 10 days based on the planet occurrence rates derived in previous surveys. For M dwarfs, the percentage of stars with a ho...

  9. VizieR Online Data Catalog: Radial velocities of K-M dwarfs (Sperauskas+, 2016)

    Science.gov (United States)

    Sperauskas, J.; Bartasiute, S.; Boyle, R. P.; Deveikis, V.; Raudeliunas, S.; Upgren, A. R.

    2016-09-01

    We analyzed nearly 3300 measurements of radial velocities for 1049 K-M dwarfs, that we obtained during the past decade with a CORAVEL-type instrument, with a primary emphasis on detecting and eliminating from kinematic calculations the spectroscopic binaries and binary candidates. We present the catalog of our observations of radial velocities for 959 stars which are not suspected of velocity variability. Of these, 776 stars are from the MCC sample and 173 stars are K-M dwarfs from the CNS4. The catalog consists of two parts: Table 2 lists the mean radial velocities, and Table 2a contains individual measurements. Our radial velocities agree with the best published standard stars to within 0.7km/s in precision. Combining these and supplementary radial-velocity data with Hipparcos/Tycho-2 astrometry (Table 4 summarizes input observational data) we calculated the space velocity components and parameters of the galactic orbits in a three-component model potential by Johnston K.V. et al. (1995ApJ...451..598J) for a total of 1088 K-M dwarfs (Table 5), that we use for kinematical analysis and for the identification of possible candidate members of nearby stellar kinematic groups. We identified 146 stars as possible candidate members of the classical moving groups and known or suspected subgroups (Table 7). We show that the distributions of space-velocity components, orbital eccentricities, and maximum distances from the Galactic plane for nearby K-M dwarfs are consistent with the presence of young, intermediate-age and old populations of the thin disk and a small fraction (3%) of stars with the thick disk kinematics. (7 data files).

  10. Microlensing Discovery of a Population of Very Tight, Very Low-mass Binary Brown Dwarfs

    CERN Document Server

    Choi, J -Y; Udalski, A; Sumi, T; Gaudi, B S; Gould, A; Bennett, D P; Dominik, M; Beaulieu, J -P; Tsapras, Y; Bozza, V; Abe, F; Bond, I A; Botzler, C S; Chote, P; Freeman, M; Fukui, A; Furusawa, K; Itow, Y; Ling, C H; Masuda, K; Matsubara, Y; Miyake, N; Muraki, Y; Ohnishi, K; Rattenbury, N J; Saito, To; Sullivan, D J; Suzuki, K; Sweatman, W L; Suzuki, D; Takino, S; Tristram, P J; Wada, K; Yock, P C M; Szymański, M K; Kubiak, M; Pietrzyński, G; Soszyński, I; Skowron, J; Kozłowski, S; Poleski, R; Ulaczyk, K; Wyrzykowski, Ł; Pietrukowicz, P; Almeida, L A; DePoy, D L; Dong, Subo; Gorbikov, E; Jablonski, F; Henderson, C B; Hwang, K -H; Janczak, J; Jung, Y -K; Kaspi, S; Lee, C -U; Malamud, U; Maoz, D; McGregor, D; Munoz, J A; Park, B -G; Park, H; Pogge, R W; Shvartzvald, Y; Shin, I -G; Yee, J C; Alsubai, K A; Browne, P; Burgdorf, M J; Novati, S Calchi; Dodds, P; Fang, X -S; Finet, F; Glitrup, M; Grundahl, F; Gu, S -H; Hardis, S; Harpsøe, K; Hinse, T C; Hornstrup, A; Hundertmark, M; Jessen-Hansen, J; Jørgensen, U G; Kains, N; Kerins, E; Liebig, C; Lund, M N; Lundkvist, M; Maier, G; Mancini, L; Mathiasen, M; Penny, M T; Rahvar, S; Ricci, D; Scarpetta, G; Skottfelt, J; Snodgrass, C; Southworth, J; Surdej, J; Tregloan-Reed, J; Wambsganss, J; Wertz, O; Zimmer, F; Albrow, M D; Bachelet, E; Batista, V; Brillant, S; Cassan, A; Cole, A A; Coutures, C; Dieters, S; Prester, D Dominis; Donatowicz, J; Fouqué, P; Greenhill, J; Kubas, D; Marquette, J -B; Menzies, J W; Sahu, K C; Zub, M; Bramich, D M; Horne, K; Steele, I A; Street, R A

    2013-01-01

    Although many models have been proposed, the physical mechanisms responsible for the formation of low-mass brown dwarfs are poorly understood. The multiplicity properties and minimum mass of the brown-dwarf mass function provide critical empirical diagnostics of these mechanisms. We present the discovery via gravitational microlensing of two very low-mass, very tight binary systems. These binaries have directly and precisely measured total system masses of 0.025 Msun and 0.034 Msun, and projected separations of 0.31 AU and 0.19 AU, making them the lowest-mass and tightest field brown-dwarf binaries known. The discovery of a population of such binaries indicates that brown dwarf binaries can robustly form at least down to masses of ~0.02 Msun. Future microlensing surveys will measure a mass-selected sample of brown-dwarf binary systems, which can then be directly compared to similar samples of stellar binaries.

  11. Mass modelling of dwarf spheroidal galaxies: the effect of unbound stars from tidal tails and the Milky Way

    Science.gov (United States)

    Klimentowski, Jarosław; Łokas, Ewa L.; Kazantzidis, Stelios; Prada, Francisco; Mayer, Lucio; Mamon, Gary A.

    2007-06-01

    We study the origin and properties of the population of unbound stars in the kinematic samples of dwarf spheroidal (dSph) galaxies. For this purpose we have run a high-resolution N-body simulation of a two-component dwarf galaxy orbiting in a Milky Way potential. In agreement with the tidal stirring scenario of Mayer et al., the dwarf is placed on a highly eccentric orbit, its initial stellar component is in the form of an exponential disc and it has a NFW-like dark matter (DM) halo. After 10 Gyr of evolution the dwarf produces a spheroidal stellar component and is strongly tidally stripped so that mass follows light and the stars are on almost isotropic orbits. From this final state, we create mock kinematic data sets for 200 stars by observing the dwarf in different directions. We find that when the dwarf is observed along the tidal tails the kinematic samples are strongly contaminated by unbound stars from the tails. We also study another source of possible contamination by adding stars from the Milky Way. We demonstrate that most of the unbound stars can be removed by the method of interloper rejection proposed by den Hartog & Katgert and recently tested on simulated DM haloes. We model the cleaned-up kinematic samples using solutions of the Jeans equation with constant mass-to-light ratio (M/L) and velocity anisotropy parameter. We show that even for such a strongly stripped dwarf the Jeans analysis, when applied to cleaned samples, allows us to reproduce the mass and M/L of the dwarf with accuracy typically better than 25 per cent and almost exactly in the case when the line of sight is perpendicular to the tidal tails. The analysis was applied to the new data for the Fornax dSph galaxy. We show that after careful removal of interlopers the velocity dispersion profile of Fornax can be reproduced by a model in which mass traces light with a M/L of 11 solar units and isotropic orbits. We demonstrate that most of the contamination in the kinematic sample of

  12. Mass Modelling of Dwarf Spheroidal Galaxies: the Effect of Unbound Stars From Tidal Tails And the Milky Way

    Energy Technology Data Exchange (ETDEWEB)

    Klimentowski, Jaroslaw; Lokas, Ewa L.; /Warsaw, Copernicus Astron. Ctr.; Kazantzidis, Stelios; /KIPAC, Menlo Park; Prada, Francisco; /IAA, Granada; Mayer, Lucio; /Zurich,; Mamon, Gary A.; /Paris, Inst. Astrophys. /Meudon Observ.

    2006-11-14

    We study the origin and properties of the population of unbound stars in the kinematic samples of dwarf spheroidal galaxies. For this purpose we have run a high resolution N- body simulation of a two-component dwarf galaxy orbiting in a Milky Way potential. In agreement with the tidal stirring scenario of Mayer et al., the dwarf is placed on a highly eccentric orbit, its initial stellar component is in the form of an exponential disk and it has a NFW-like dark matter halo. After 10 Gyrs of evolution the dwarf produces a spheroidal stellar component and is strongly tidally stripped so that mass follows light and the stars are on almost isotropic orbits. From this final state, we create mock kinematic data sets for 200 stars by observing the dwarf in different directions.We find that when the dwarf is observed along the tidal tails the kinematic samples are strongly contaminated by unbound stars from the tails.We also study another source of possible contamination by adding stars from the Milky Way. We demonstrate that most of the unbound stars can be removed by the method of interloper rejection proposed by den Hartog & Katgert and recently tested on simulated dark matter haloes. We model the cleaned up kinematic samples using solutions of the Jeans equation with constant mass-to-light ratio and velocity anisotropy parameter. We show that even for such strongly stripped dwarf the Jeans analysis, when applied to cleaned samples, allows us to reproduce the mass and mass-to-light ratio of the dwarf with accuracy typically better than 25 percent and almost exactly in the case when the line of sight is perpendicular to the tidal tails. The analysis was applied to the new data for the Fornax dSph galaxy for which we find a mass-to-light ratio of 11 solar units and isotropic orbits. We demonstrate that most of the contamination in the kinematic sample of Fornax probably originates from the Milky Way.

  13. Cool dwarfs in wide multiple systems. Paper 5: New astrometry of 54 wide pairs with M dwarfs

    CERN Document Server

    Cortés-Contreras, M; Montes, D

    2015-01-01

    We investigate the membership in double, triple or higher-order-multiplicity systems of 54 pairs with at least one bright M dwarf in the solar neighbourhood. These M dwarfs are potential targets of radial-velocity surveys for exoplanets. We measure angular separations and position angles from optical images taken with TCP and CAMELOT at the IAC80 telescope at the Observatorio del Teide, and complement them with our measurements on photographic plate digitizations. We also use data in the Washington Double Star Catalogue and other bibliographic sources. We confirm the physical binding of 52 multiple systems, for which we comprehensively compile, derive and provide basic astrophysical parameters in a homogeneous way (spectral types, heliocentric distances, projected physical separations, individual masses, estimated orbital periods, binding energies). Of the 52 systems, 38 are double, 11 are triple and three are quadruple with a variety of architectures. Four systems contain white dwarfs, six systems display va...

  14. Asteroseismology of white dwarf stars

    CERN Document Server

    Córsico, A H

    2014-01-01

    Most of low- and intermediate-mass stars that populate the Universe will end their lives as white dwarf stars. These ancient stellar remnants have encrypted inside a precious record of the evolutionary history of the progenitor stars, providing a wealth of information about the evolution of stars, star formation, and the age of a variety of stellar populations, such as our Galaxy and open and globular clusters. While some information like surface chemical composition, temperature and gravity of white dwarfs can be inferred from spectroscopy, the internal structure of these compact stars can be unveiled only by means of asteroseismology, an approach based on the comparison between the observed pulsation periods of variable stars and the periods of appropriate theoretical models. In this communication, we first briefly describe the physical properties of white dwarf stars and the various families of pulsating white dwarfs known up to the present day, and then we present two recent analysis carried out by the La...

  15. Inside the whale: the structure and dynamics of the isolated Cetus dwarf spheroidal

    CERN Document Server

    Lewis, G F; Chapman, S C; McConnachie, A; Irwin, M J; Tolstoy, E; Tanvir, N R

    2006-01-01

    This paper presents a study of the Cetus dwarf, an isolated dwarf galaxy within the Local Group. A matched-filter analysis of the INT/WFC imaging of this system reveals no evidence for significant tidal debris that could have been torn from the galaxy, bolstering the hypothesis that Cetus has never significantly interacted with either the Milky Way or M31. Additionally, Keck/Deimos spectroscopic observations identify this galaxy as a distinct kinematic population possessing a systematic velocity of $-87\\pm2{\\rm km\\ s^{-1}}$ and with a velocity dispersion of $17\\pm2{\\rm km s^{-1}}$; while tentative, these data also suggest that Cetus possesses a moderate rotational velocity of $\\sim8{\\rm km s^{-1}}$. The population is confirmed to be relatively metal-poor, consistent with ${\\rm [Fe/H]\\sim-1.9}$, and, assuming virial equilibrium, implies that the Cetus dwarf galaxy possesses a $M/L\\sim70$. It appears, therefore, that Cetus may represent a primordial dwarf galaxy, retaining the kinematic and structural propertie...

  16. SDSS-IV MaNGA: properties of galaxies with kinematically decoupled stellar and gaseous components

    Science.gov (United States)

    Jin, Yifei; Chen, Yanmei; Shi, Yong; Tremonti, C. A.; Bershady, M. A.; Merrifield, M.; Emsellem, E.; Fu, Hai; Wake, D.; Bundy, K.; Lin, Lihwai; Argudo-Fernandez, M.; Huang, Song; Stark, D. V.; Storchi-Bergmann, T.; Bizyaev, D.; Brownstein, J.; Chisholm, J.; Guo, Qi; Hao, Lei; Hu, Jian; Li, Cheng; Li, Ran; Masters, K. L.; Malanushenko, E.; Pan, Kaike; Riffel, R. A.; Roman-Lopes, A.; Simmons, A.; Thomas, D.; Wang, Lan; Westfall, K.; Yan, Renbin

    2016-11-01

    We study the properties of 66 galaxies with kinematically misaligned gas and stars from MaNGA survey. The fraction of kinematically misaligned galaxies varies with galaxy physical parameters, i.e. M*, SFR and sSFR. According to their sSFR, we further classify these 66 galaxies into three categories, 10 star-forming, 26 `Green Valley' and 30 quiescent ones. The properties of different types of kinematically misaligned galaxies are different in that the star-forming ones have positive gradient in Dn4000 and higher gas-phase metallicity, while the green valley/quiescent ones have negative Dn4000 gradients and lower gas-phase metallicity on average. There is evidence that all types of the kinematically misaligned galaxies tend to live in more isolated environment. Based on all these observational results, we propose a scenario for the formation of star-forming galaxies with kinematically misaligned gas and stars -- the progenitor accretes misaligned gas from a gas-rich dwarf or cosmic web, the cancellation of angular momentum from gas-gas collisions between the pre-existing gas and the accreted gas largely accelerates gas inflow, leading to fast centrally concentrated star formation. The higher metallicity is due to enrichment from this star formation. For the kinematically misaligned green valley and quiescent galaxies, they might be formed through gas-poor progenitors accreting kinematically misaligned gas from satellites which are smaller in mass.

  17. Singing and dancing white dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Mukadam, Anjum S; Szkody, Paula [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Gaensicke, Boris T [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Nitta, Atsuko, E-mail: anjum@astro.washington.ed [Gemini Observatory, Hilo, HI 96720 (United States)

    2009-06-01

    Accreting white dwarfs have recently been shown to exhibit non-radial pulsations similar to their non-interacting counterparts. This allows us to probe the interior of the accreting white dwarf using seismology, and may be the only way to determine masses for non-eclipsing cataclysmic variables. Improving our understanding of accreting white dwarfs will have implications for models of supernovae Type Ia. Pulsating white dwarfs in cataclysmic variables are also useful in establishing the effects of accretion on pulsations. A search for nonradial pulsations among suitable candidates has led to the discovery of twelve such systems known to date. With the goal of establishing an instability strip (or strips) for these pulsating accretors, we acquired HST ultra-violet time-series spectroscopy of six pulsating white dwarfs in cataclysmic variables in 2007 and 2008. This approach enables us to measure the effective temperature of the white dwarf using the co-added spectrum, and to simultaneously characterize the pulsations. We also intended to constrain the pulsation mode identification by comparing the ultra-violet amplitudes to those from near-simultaneous ground-based photometry. Our preliminary results indicate a broad instability strip in the temperature range of 10500-15400 K.

  18. X-ray emission from the young brown dwarfs of the Taurus molecular cloud

    Science.gov (United States)

    Grosso, N.; Briggs, K. R.; Güdel, M.; Guieu, S.; Franciosini, E.; Palla, F.; Dougados, C.; Monin, J.-L.; Ménard, F.; Bouvier, J.; Audard, M.; Telleschi, A.

    2007-06-01

    Aims:We report the X-ray properties of young (~3 Myr) bona fide brown dwarfs of the Taurus Molecular Cloud (TMC). Methods: The XMM-Newton Extended Survey of the TMC (XEST) is a large program designed to systematically investigate the X-ray properties of young stellar/substellar objects in the TMC. In particular, the area surveyed by 15 XMM-Newton pointings (of which three are archival observations), supplemented with one archival Chandra observation, allows us to study 17 brown dwarfs with M spectral types. Results: Half of this sample (9 out of 17 brown dwarfs) is detected; 7 brown dwarfs are detected here for the first time in X-rays. We observed a flare from one brown dwarf. We confirm several previous findings on brown dwarf X-ray activity: a log-log relation between X-ray and bolometric luminosity for stars (with L* ≤ 10 L_⊙) and brown dwarfs detected in X-rays, which is consistent with a mean X-ray fractional luminosity =-3.5 ± 0.4; for the XEST brown dwarfs, the median of log(L_X/L_*) (including upper limits) is -4.0; a shallow log-log relation between X-ray fractional luminosity and mass; a log-log relation between X-ray fractional luminosity and effective temperature; a log-log relation between X-ray surface flux and effective temperature. We find no significant log-log correlation between the X-ray fractional luminosity and EW(Hα). Accreting and nonaccreting brown dwarfs have a similar X-ray fractional luminosity. The median X-ray fractional luminosity of nonaccreting brown dwarfs is about 4 times lower than the mean saturation value for rapidly rotating low-mass field stars. Our TMC brown dwarfs have higher X-ray fractional luminosity than brown dwarfs in the Chandra Orion Ultradeep Project. Conclusions: The X-ray fractional luminosity declines from low-mass stars to M-type brown dwarfs, and as a sample, the brown dwarfs are less efficient X-ray emitters than low-mass stars. We thus conclude that while the brown dwarf atmospheres observed here are

  19. Kinematics grounded on light

    CERN Document Server

    Neda, Zoltan

    2015-01-01

    The space-time of modern physics is tailored on light. We rigorously construct the basic entities needed by kinematics: geometry of the physical space and time, using as tool electromagnetic waves, and particularly light-rays. After such a mathematically orthodox construction, the special theory of relativity will result naturally. One will clearly understand and easily accept all those puzzling consequences that makes presently the special theory of relativity hard to digest. Such an approach is extremely rewarding in teaching the main ideas of Einstein's relativity theory for high-school and/or university students. Interesting speculations regarding the fundaments and future of physics are made.

  20. Kinematic geometry of gearing

    CERN Document Server

    Dooner, David B

    2012-01-01

    Building on the first edition published in 1995 this new edition of Kinematic Geometry of Gearing has been extensively revised and updated with new and original material. This includes the methodology for general tooth forms, radius of torsure', cylinder of osculation, and cylindroid of torsure; the author has also completely reworked the '3 laws of gearing', the first law re-written to better parallel the existing 'Law of Gearing" as pioneered by Leonard Euler, expanded from Euler's original law to encompass non-circular gears and hypoid gears, the 2nd law of gearing describing a unique relat

  1. Kinematics of the symbiotic system R Aqr

    Science.gov (United States)

    Navarro, S.; Corral, L. J.; Steffen, W.

    2014-04-01

    We present the results of the kinematical analysis of the symbiotic system R Aqr. We obtained high dispersion spectra with the MES spectrograph at the 2.1 m telescope of San Pedro Mártir (MEZCAL). The used filter were Ha + [NII], (λc = 6575Å, Δλ = 90Å). We analyse the [NII] λλ6583 line. When the observations are compared with previous ones by Solf (1992) we detected an important change in the projected velocities of the observed knots, supporting the idea of a precessing jet. We are working also in a 3-D kinematic model for the object using the measured velocities and the state of the model is presented.

  2. High-Frequency Properties of Ultracool Dwarf Star Radio Transients, or The Little Dwarfs that Could

    Science.gov (United States)

    Ravi, Vikram; Hobbs, George; Keith, Michael; Champion, David; Ferrario, Lilia; Wickramasinghe, Dayal

    2009-07-01

    Radio transients are among the most intriguing phenomena in astronomy. Numerous flaring events, some periodic, have lately surfaced, with only few identified with known objects such as magnetic stars. Periodic, non-thermal, highly circularly-polarised pulses and unusually strong quiescence have been recently detected from three late-type quickly-rotating (~2hr periods) ultracool dwarf stars (>M7) at centimetric wavelengths. This violates empirical relations and quantifiers of dwarf-star surface activity. Measurements of dwarf-star kiloGauss magnetic fields have led to emission models based on dipole fields and incoherent gyrosynchrotron or coherent electron-cyclotron maser mechanisms. We propose to observe two such similar objects at 1cm and 7mm (LP944-20 and DENIS1048-3956) that are known to flare but without detected periodicities. No observations of high-frequency emission from any magnetic star have been published. The broadband capabilities of CABB will provide extraordinary frequency-synthesised sensitivity in a search for periodicity. The obtained spectral indices, along with possible high-frequency spectral cut-offs, will greatly help constrain emission models of magnetic stars. This is the first attempt to characterise the high-frequency transient radio sky, a key science project for future telescopes such as ASKAP and the SKA.

  3. The distribution of alpha elements in Andromeda dwarf galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Vargas, Luis C.; Geha, Marla C.; Tollerud, Erik J., E-mail: luis.vargas@yale.edu [Department of Astronomy, Yale University, 260 Whitney Avenue, New Haven, CT 06511 (United States)

    2014-07-20

    We present alpha to iron abundance ratios for 226 individual red giant branch stars in nine dwarf galaxies of the Andromeda (M31) satellite system. The abundances are measured from the combined signal of Mg, Si, Ca, and Ti lines in Keck/DEIMOS medium-resolution spectra. This constitutes the first large sample of alpha abundance ratios measured in the M31 satellite system. The dwarf galaxies in our sample exhibit a variety of alpha abundance ratios, with the average values in each galaxy ranging from approximately solar ([α/Fe] ∼ + 0.0) to alpha-enhanced ([α/Fe] ∼ + 0.5). These variations do not show a correlation with internal kinematics, environment, or stellar density. We confirm radial gradients in the iron abundance of two galaxies out of the five with sufficient data (NGC 185 and And II). There is only tentative evidence for an alpha abundance radial gradient in NGC 185. We homogeneously compare our results to the Milky Way classical dwarf spheroidals, finding evidence for wider variation in average alpha abundance. In the absence of chemical abundances for the M31 stellar halo, we compare to the Milky Way stellar halo. A stellar halo comprised of disrupted M31 satellites is too metal-rich and inconsistent with the Milky Way halo alpha abundance distribution even if considering only satellites with predominantly old stellar populations. The M31 satellite population provides a second system in which to study chemical abundances of dwarf galaxies and reveals a wider variety of abundance patterns than the Milky Way.

  4. White dwarfs, red dwarfs and halo dark matter

    Energy Technology Data Exchange (ETDEWEB)

    GarcIa-Berro, E; Torres, S; Camacho, J [Departament de Fisica Aplicada, Escola Politecnica Superior de Castelldefels, Universitat Politecnica de Catalunya, Av. del Canal Olimpic, s/n, 08860 Castelldefels (Spain); Isern, J, E-mail: garcia@fa.upc.ed [Institut de Ciencies de l' Espai, CSIC, Campus UAB, Facultat de Ciencies, Torre C-5, 08193 Bellaterra (Spain)

    2009-06-01

    The nature of the microlensing events observed by the MACHO team towards the LMC still remains controversial. Low-mass substellar objects and stars with masses larger than approx 1M{sub o-dot} have been ruled out, while stars of approx 0.5 M{sub o-dot} are the most probable candidates. This means that the microlenses should be either red or white dwarfs. Consequently, we assess jointly the relative contributions of both types of stars to the mass budget of the Galactic halo. We use a Monte Carlo code that incorporates up-to-date evolutionary sequences of both red dwarfs and white dwarfs as well as detailed descriptions of both our Galaxy and the LMC and we compare the synthetic populations obtained with our simulator with the results obtained by the MACHO and EROS experiments. We find that the contribution of the red dwarf population is not enough to explain the number of events measured by the MACHO team. Even though, the optical depth obtained in our simulations almost doubles that obtained when taking into account the white dwarf population alone. Finally, we also find that the contribution to the halo dark matter of the entire population under study is smaller than 10%, at the 95% confidence level.

  5. The effect of tides on the Fornax dwarf spheroidal galaxy

    CERN Document Server

    Battaglia, Giuseppina; Nipoti, Carlo

    2015-01-01

    Estimates of the mass distribution and dark-matter (DM) content of dwarf spheroidal galaxies (dSphs) are usually derived under the assumption that the effect of the tidal field of the host galaxy is negligible over the radial extent probed by kinematic data-sets. We assess the implications of this assumption in the specific case of the Fornax dSph by means of N-body simulations of a satellite orbiting around the Milky Way. We consider observationally-motivated orbits and we tailor the initial distributions of the satellite's stars and DM to match, at the end of the simulations, the observed structure and kinematics of Fornax. In all our simulations the present-day observable properties of Fornax are not significantly influenced by tidal effects. The DM component is altered by the interaction with the Galactic field (up to 20% of the DM mass within 1.6 kpc is lost), but the structure and kinematics of the stellar component are only mildly affected even in the more eccentric orbit (more than 99% of the stellar ...

  6. Effects of Tides on Milky Way Dwarf Satellite Galaxies

    Science.gov (United States)

    Wang, Mei-Yu; Strigari, Louis; Fattahi, Azadeh; Frenk, Carlos S.; Cooper, Andrew; Lovell, Mark; Navarro, Julio F.; Sawala, Till; Zentner, Andrew

    2017-01-01

    Using detailed observations of the Local Group to study wide-ranging questions in galaxy formation and dark matter physics - has become a rich field over the past decade. In this talk, I will present frameworks that address some of these questions by combining high-precision stellar kinematic measurements with state-of-art cosmological hydrodynamical N-body simulations. I will demonstrate that the properties of dark matter subhalo of individual satellite galaxies implied by stellar kinematic data can be linked to the galaxy evolution mechanisms such as infall time and the gravitational tidal interaction with Milky Way potential. In the cold dark matter (CDM) scenario, some dwarf galaxies explicitly require to be shaped under significant gravitational tidal forces, which will leave imprints on their stellar distribution and kinematics. I will discuss how these features could serve as a test to the nature of dark matter or stellar feedback strength. I will also discuss how we can study the tidally “disturbed” or even “destroyed” satellite galaxies as building blocks to our Milky Way stellar halo by understanding the properties of their progenitors and observation limit imposed by current and future surveys.

  7. The Atlas3D project - XX. Mass-size and Mass-sigma projections of the Virial Plane of early-type galaxies: variation of morphology, kinematics, mass-to-light ratio and stellar initial mass function

    CERN Document Server

    Cappellari, Michele; Alatalo, Katherine; Blitz, Leo; Bois, Maxime; Bournaud, Frederic; Bureau, M; Crocker, Alison F; Davies, Roger L; Davis, Timothy A; de Zeeuw, P T; Duc, Pierre-Alain; Khochfar, Sadegh; Krajnovic, Davor; Kuntschner, Harald; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M

    2013-01-01

    In the companion Paper XIX we derive accurate total (M/L)_JAM within a sphere of radius r=Re, as well as stellar (M/L)_stars for the volume-limited Atlas3D sample of 260 early-type galaxies. Here we study the two projections (M_JAM,sigma_e) and (M_JAM,R_e^max) of the thin Virial Plane (VP)(M_JAM,sigma_e,R_e^max) which describes the distribution of the galaxy population. The distribution of galaxy properties on both projections of the VP is characterized by (i) a boundary in the galaxy distribution, described by two power-laws, joined by a break at a characteristic mass M_JAM ~ 3*10^10 Msun, which corresponds to the minimum Re and maximum stellar density, and (ii) a characteristic mass M_JAM ~ 2*10^11 Msun which separates a population dominated by fast rotator with disks at lower masses, from one dominated by quite round slow rotators at larger masses. The distribution of ETGs properties on the two projections of the VP tends to be constant along lines of constant sigma_e, and forms a continuous and parallel s...

  8. White Dwarfs:. Contributors and Tracers of the Galactic Dark-Matter Halo

    Science.gov (United States)

    Koopmans, L. V. E.; Blandford, R. D.

    2002-03-01

    We examine the claim by Oppenheimer et al. (2001) that the local halo density of white dwarfs is an order of magnitude higher than previously thought. As it stands, the observational data support the presence of a kinematically distinct population of halo white dwarfs at the >99% confidence level. A maximum-likelihood analysis gives a radial velocity dispersionREFID="9789812778017_0024FN001"> of σ hU = 150+80-40\\ km s-1 and an asymmetric drift of ν ha = 176+102-80\\ km s-1, for a Schwarzschild velocity distribution function with σU:σV:σW = 1:2/3:1/2. Halo white dwarfs have a local number density of 1.1+2.1-0.7 × 10-4\\ pc-3, which amounts to 0.8+1.6-0.5 per cent of the nominal local dark-matter halo density and is 5.0+9.5-3.2 times (90% C.L.) higher and thus only marginally in agreement with previous estimates. We discuss several direct consequences of this white-dwarf population (e.g. microlensing) and postulate a potential mechanism to eject young white dwarfs from the disc to the halo, through the orbital instabilities in triple or multiple stellar systems.

  9. The no-spin zone: rotation vs dispersion support in observed and simulated dwarf galaxies

    CERN Document Server

    Wheeler, Coral; Bullock, James S; Boylan-Kolchin, Michael; Onorbe, Jose; Fitts, Alex; Hopkins, Philip F; Keres, Dusan

    2015-01-01

    We perform a systematic Bayesian analysis of rotation vs. dispersion support ($v_{\\rm rot} / \\sigma$) in $40$ dwarf galaxies throughout the Local Volume (LV) over a stellar mass range $10^{3.5} M_{\\rm \\odot} < M_{\\star} < 10^8 M_{\\rm \\odot}$. We find that the stars in $\\sim 90\\%$ of the LV dwarf galaxies studied -- both satellites and isolated systems -- are dispersion-supported. In particular, we show that $7/10$ *isolated* dwarfs in our sample have stellar populations with $v_{\\rm rot} / \\sigma < 0.6$. All have $v_{\\rm rot} / \\sigma \\lesssim 2$. These results challenge the traditional view that the stars in gas-rich dwarf irregulars (dIrrs) are distributed in cold, rotationally-supported stellar disks, while gas-poor dwarf spheroidals (dSphs) are kinematically distinct in having dispersion-supported stars. We see no clear trend between $v_{\\rm rot} / \\sigma$ and distance to the closest $\\rm L_{\\star}$ galaxy, nor between $v_{\\rm rot} / \\sigma$ and $M_{\\star}$ within our mass range. We apply the sam...

  10. Brown dwarfs as close companions to white dwarfs

    Science.gov (United States)

    Stringfellow, Guy S.; Bodenheimer, Peter; Black, David C.

    1990-01-01

    The influence of the radiation flux emitted by a white dwarf primary on the evolution of a closely orbiting brown dwarf (BD) companion is investigated. Full stellar evolutionary calculations are presented for both isolated and thermal bath cases, including effects of large variations in the atmospheric grain opacities. High grain opacities significantly increase the radii of the BDs, but the thermal bath does not. The major influence of the thermal bath is to increase substantially the surface temperature and luminosity of the BD at a given age. These results are compared with the observational properties of the possible BD companion of the white dwarf G29-38. Inclusion of both physical effects, high grain opacities and thermal bath, increases the mass range (0.034-0.063 solar masses) of viable models significantly, yet the final determination of whether the object is indeed a BD requires improvements in the observations of the system's properties.

  11. Young tidal dwarf galaxies cannot be used to probe dark matter in galaxies

    CERN Document Server

    Flores, H; Fouquet, S; Puech, M; Kroupa, P; Yang, Y; Pawlowski, M

    2015-01-01

    The location of dark-matter free, tidal dwarf galaxies (TDGs) in the baryonic Tully Fisher (bTF) diagram has been used to test cosmological scenarios, leading to various and controversial results. Using new high-resolution 3D spectroscopic data, we re-investigate the morpho-kinematics of these galaxies to verify whether or not they can be used for such a purpose. We find that the three observed TDGs are kinematically not virialized and show complex morphologies and kinematics, leading to considerable uncertainties about their intrinsic rotation velocities and their locations on the bTF. Only one TDG can be identify as a (perturbed) rotation disk that it is indeed a sub-component of NGC5291N and that lies at $<$1$\\sigma$ from the local bTF relation. It results that the presently studied TDGs are young, dynamically forming objects, which are not enough virialized to robustly challenge cosmological scenarios.

  12. Prolate rotation and metallicity gradient in the transforming dwarf galaxy Phoenix

    Science.gov (United States)

    Kacharov, Nikolay; Battaglia, Giuseppina; Rejkuba, Marina; Cole, Andrew A.; Carrera, Ricardo; Fraternali, Filippo; Wilkinson, Mark I.; Gallart, Carme G.; Irwin, Mike; Tolstoy, Eline

    2017-04-01

    Transition type dwarf galaxies are thought to be systems undergoing the process of transformation from a star-forming into a passively evolving dwarf, which makes them particularly suitable to study evolutionary processes driving the existence of different dwarf morphological types. Here we present results from a spectroscopic survey of ∼200 individual red giant branch stars in the Phoenix dwarf, the closest transition type with a comparable luminosity to 'classical' dwarf galaxies. We measure a systemic heliocentric velocity Vhelio = -21.2 ± 1.0 km s-1. Our survey reveals the clear presence of prolate rotation that is aligned with the peculiar spatial distribution of the youngest stars in Phoenix. We speculate that both features might have arisen from the same event, possibly an accretion of a smaller system. The evolved stellar population of Phoenix is relatively metal-poor ( = -1.49 ± 0.04 dex) and shows a large metallicity spread (σ[Fe/H] = 0.51 ± 0.04 dex), with a pronounced metallicity gradient of -0.13 ± 0.01 dex arcmin-1 similar to luminous, passive dwarf galaxies. We also report a discovery of an extremely metal-poor star candidate in Phoenix and discuss the importance of correcting for spatial sampling when interpreting the chemical properties of galaxies with metallicity gradients. This study presents a major leap forward in our knowledge of the internal kinematics of the Phoenix transition type dwarf galaxy and the first wide area spectroscopic survey of its metallicity properties. A table containing the measured velocities, metallicities, and CaT equivalent widths of all spectroscopic targets is available online at the CDS.

  13. Kinematics in CTB 80

    Science.gov (United States)

    Greidanus, H.; Strom, R. G.

    1990-12-01

    This paper presents data describing the radial kinematics of the core of the complex object CTB 80, believed to be a supernova remnant. The radial velocity of the CTB 80 was found to extend between -130 and 95 km/sec (LSR), with the emission being brightest and most concentrated in filaments around -30 km/sec, and weaker at higher velocities. The character of the position-velocity diagrams was found to be consistent with models of expanding ellipsoidal shells. A comparison with these models indicated a short dimension for the core along the line of sight, and favors a momentum-driven expansion. This type of expansion is indicative of a neutron star excitation for the core of CTB 80, as opposed to a normal supernova shock.

  14. Kinematically Detected Halo Streams

    CERN Document Server

    Smith, Martin C

    2016-01-01

    Clues to the origins and evolution of our Galaxy can be found in the kinematics of stars around us. Remnants of accreted satellite galaxies produce over- densities in velocity-space, which can remain coherent for much longer than spatial over-densities. This chapter reviews a number of studies that have hunted for these accretion relics, both in the nearby solar-neighborhood and the more-distant stellar halo. Many observational surveys have driven this field forwards, from early work with the Hipparcos mission, to contemporary surveys like RAVE & SDSS. This active field continues to flourish, providing many new discoveries, and will be revolutionised as the Gaia mission delivers precise proper motions for a billion stars in our Galaxy.

  15. Simulating avian wingbeat kinematics.

    Science.gov (United States)

    Parslew, Ben; Crowther, William J

    2010-12-01

    Inverse dynamics methods are used to simulate avian wingbeats in varying flight conditions. A geometrically scalable multi-segment bird model is constructed, and optimisation techniques are employed to determine segment motions that generate desired aerodynamic force coefficients with minimal mechanical power output. The results show that wingbeat kinematics vary gradually with changes in cruise speed, which is consistent with experimental data. Optimised solutions for cruising flight of the pigeon suggest that upstroke wing retraction is used as a method of saving energy. Analysis of the aerodynamic force coefficient variation in high and low speed cruise leads to the proposal that a suitable gait metric should include both thrust and lift generation during each half-stroke.

  16. Rattlesnake strike behavior: kinematics

    Science.gov (United States)

    Kardong; v

    1998-03-01

    The predatory behavior of rattlesnakes includes many distinctive preparatory phases leading to an extremely rapid strike, during which venom is injected. The rodent prey is then rapidly released, removing the snake's head from retaliation by the prey. The quick action of the venom makes possible the recovery of the dispatched prey during the ensuing poststrike period. The strike is usually completed in less than 0.5 s, placing a premium on an accurate strike that produces no significant errors in fang placement that could result in poor envenomation and subsequent loss of the prey. To clarify the basis for effective strike performance, we examined the basic kinematics of the rapid strike using high-speed film analysis. We scored numerous strike variables. Four major results were obtained. (1) Neurosensory control of the strike is based primarily upon sensory inputs via the eyes and facial pits to launch the strike, and upon tactile stimuli after contact. Correction for errors in targeting occurs not by a change in strike trajectory, but by fang repositioning after the jaws have made contact with the prey. (2) The rattlesnake strike is based upon great versatility and variation in recruitment of body segments and body postures. (3) Forces generated during acceleration of the head are transferred to posterior body sections to decelerate the head before contact with the prey, thereby reducing impact forces upon the snake's jaws. (4) Body acceleration is based on two patterns of body displacement, one in which acute sections of the body open like a gate, the other in which body segments flow around postural curves similar to movements seen during locomotion. There is one major implication of these results: recruitment of body segments, launch postures and kinematic features of the strike may be quite varied from strike to strike, but the overall predatory success of each strike by a rattlesnake is very consistent.

  17. Scapula Kinematics of Youth Baseball Players

    Directory of Open Access Journals (Sweden)

    Oliver Gretchen

    2015-12-01

    Full Text Available Literature has revealed the importance of quantifying resting scapular posture in overhead athletes as well as quantifying scapular kinematics during dynamic movement. Prior to this project much of the attention in throwing research had been focused on the position of the humerus without description of the positioning of the scapula. Therefore, it was the purpose of this study to present scapular kinematics during pitching in youth baseball players. Twenty-five youth baseball players (age 11.3 + 1.0 years; body height 152.4 + 9.0 cm; body mass 47.5 + 11.3 kg, with no history of injury, participated in the study. Scapular kinematics at the events of maximum humeral external rotation (MER and maximum humeral internal rotation (MIR during the pitching motion were assessed three-dimensionally while pitching fastballs for strikes. Results revealed that at the event of MER, the scapula was in a position of retraction, upward rotation and a posterior tilt. While at the event of MIR, the scapula was protracted, upward rotated and tilted anteriorly.

  18. Scapula Kinematics of Youth Baseball Players.

    Science.gov (United States)

    Oliver, Gretchen; Weimar, Wendi

    2015-12-22

    Literature has revealed the importance of quantifying resting scapular posture in overhead athletes as well as quantifying scapular kinematics during dynamic movement. Prior to this project much of the attention in throwing research had been focused on the position of the humerus without description of the positioning of the scapula. Therefore, it was the purpose of this study to present scapular kinematics during pitching in youth baseball players. Twenty-five youth baseball players (age 11.3 + 1.0 years; body height 152.4 + 9.0 cm; body mass 47.5 + 11.3 kg), with no history of injury, participated in the study. Scapular kinematics at the events of maximum humeral external rotation (MER) and maximum humeral internal rotation (MIR) during the pitching motion were assessed three-dimensionally while pitching fastballs for strikes. Results revealed that at the event of MER, the scapula was in a position of retraction, upward rotation and a posterior tilt. While at the event of MIR, the scapula was protracted, upward rotated and tilted anteriorly.

  19. The evolution of iron white dwarf stars

    Directory of Open Access Journals (Sweden)

    J. A. Panei

    2001-01-01

    Full Text Available Recent measurements by Hipparcos provide strong observational evidence supporting the existence of white dwarf stars with iron-rich core composition. Here we examine the evolution of iron-rich white dwarfs, for which the cooling is substancially accelerated as compared with the standard carbon-oxigen white dwarfs.

  20. Morphological Mutations of Dwarf Galaxies

    CERN Document Server

    Hensler, Gerhard

    2012-01-01

    Dwarf galaxies (DGs) are extremely challenging objects in extragalactic astrophysics. They are expected to originate as the first units in Cold Dark-Matter cosmology. They are the galaxy type most sensitive to environmental influences and their division into multiple types with various properties have invoked the picture of their variant morphological transformations. Detailed observations reveal characteristics which allow to deduce the evolutionary paths and to witness how the environment has affected the evolution. Here we review peculiarities of general morphological DG types and refer to processes which can deplete gas-rich irregular DGs leading to dwarf ellipticals, while gas replenishment implies an evolutionary cycling. Finally, as the less understood DG types the Milky Way satellite dwarf spheroidal galaxies are discussed in the context of transformation.

  1. The rotation of brown dwarfs

    CERN Document Server

    Scholz, Aleks

    2016-01-01

    One of the characteristic features of low-mass stars is their propensity to shed large amounts of angular momentum throughout their evolution. This distinguishs them from brown dwarfs which remain fast rotators over timescales of gigayears. Brown dwarfs with rotation periods longer than a couple of days have only been found in star forming regions and young clusters. This is a useful constraint on the mass dependency of mechanisms for angular momentum regular in stars. Rotational braking by disks and winds become highly inefficient in the substellar regime. In this short review I discuss the observational evidence for the fast rotation in brown dwarfs, the implications, and the link to the spin-mass relation in planets.

  2. Faint Dwarfs in Nearby Groups

    CERN Document Server

    Speller, Ryan

    2013-01-01

    The number and distribution of dwarf satellite galaxies remain a critical test of cold dark matter-dominated structure formation on small scales. Until recently, observational information about galaxy formation on these scales has been limited mainly to the Local Group. We have searched for faint analogues of Local Group dwarfs around nearby bright galaxies, using a spatial clustering analysis of the photometric catalog of the Sloan Digital Sky Survey (SDSS) Data Release 8. Several other recent searches of SDSS have detected clustered satellite populations down to $\\Delta m_r \\equiv ({m}_{r,\\, {\\rm sat}} -\\, {m}_{r,\\, {\\rm main}}) \\sim 6$-$8$, using photometric redshifts to reduce background contamination. SDSS photometric redshifts are relatively imprecise, however, for faint and nearby galaxies. Instead we use angular size to select potential nearby dwarfs, and consider only the nearest isolated bright galaxies as primaries. As a result, we are able to detect an excess clustering signal from companions down...

  3. Branes constrictions with White Dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    García-Aspeitia, Miguel A., E-mail: aspeitia@fisica.uaz.edu.mx [Consejo Nacional de Ciencia y Tecnología, Av, Insurgentes Sur 1582, Colonia Crédito Constructor, Del. Benito Juárez, C.P. 03940, Mexico, D.F. (Mexico); Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esquina con Paseo a la Bufa S/N, C.P. 98060, Zacatecas (Mexico)

    2015-11-06

    We consider here a robust study of stellar dynamics for white dwarf stars with polytropic matter in the weak-field approximation using the Lane–Emden equation from the brane-world scenario. We also derive an analytical solution to the nonlocal energy density and show the behavior and sensitivity of these stars to the presence of extra dimensions. Similarly, we analyze stability and compactness, in order to show whether it is possible to agree with the conventional wisdom of white dwarfs dynamics. Our results predict an average value of the brane tension of <λ>≳84.818 MeV{sup 4}, with a standard deviation σ≃82.021 MeV{sup 4}, which comes from a sample of dwarf stars, being weaker than other astrophysical observations but remaining higher than cosmological results provided by nucleosynthesis among others.

  4. Branes constrictions with White Dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Aspeitia, Miguel A. [Consejo Nacional de Ciencia y Tecnologia, Mexico (Mexico); Unidad Academica de Fisica, Universidad Autonoma de Zacatecas (Mexico)

    2015-11-15

    We consider here a robust study of stellar dynamics for white dwarf stars with polytropic matter in the weak-field approximation using the Lane-Emden equation from the brane-world scenario. We also derive an analytical solution to the nonlocal energy density and show the behavior and sensitivity of these stars to the presence of extra dimensions. Similarly, we analyze stability and compactness, in order to show whether it is possible to agree with the conventional wisdom of white dwarfs dynamics. Our results predict an average value of the brane tension of left angle λ right angle >or similar 84.818 MeV{sup 4}, with a standard deviation σ ≅ 82.021 MeV{sup 4}, which comes from a sample of dwarf stars, being weaker than other astrophysical observations but remaining higher than cosmological results provided by nucleosynthesis among others. (orig.)

  5. Satellite Dwarf Galaxies in a Hierarchical Universe: The Prevalence of Dwarf-Dwarf Major Mergers

    CERN Document Server

    Deason, Alis; Garrison-Kimmel, Shea

    2014-01-01

    Mergers are a common phenomenon in hierarchical structure formation, especially for massive galaxies and clusters, but their importance for dwarf galaxies in the Local Group remains poorly understood. We investigate the frequency of major mergers between dwarf galaxies in the Local Group using the ELVIS suite of cosmological zoom-in dissipationless simulations of Milky Way- and M31-like host halos. We find that ~10% of satellite dwarf galaxies with M_star > 10^6 M_sun that are within the host virial radius experienced a major merger of stellar mass ratio closer than 0.1 since z = 1, with a lower fraction for lower mass dwarf galaxies. Recent merger remnants are biased towards larger radial distance and more recent virial infall times, because most recent mergers occurred shortly before crossing within the virial radius of the host halo. Satellite-satellite mergers also occur within the host halo after virial infall, catalyzed by the large fraction of dwarf galaxies that fell in as part of a group. The merger ...

  6. JFKengine: A Jacobian and Forward Kinematics Generator

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, K.N.

    2003-02-13

    During robot path planning and control the equations that describe the robot motions are determined and solved. Historically these expressions were derived analytically off-line. For robots that must adapt to their environment or perform a wide range of tasks, a way is needed to rapidly re-derive these expressions to take into account the robot kinematic changes, such as when a tool is added to the end-effector. The JFKengine software was developed to automatically produce the expressions representing the manipulator arm motion, including the manipulator arm Jacobian and the forward kinematic expressions. Its programming interface can be used in conjunction with robot simulation software or with robot control software. Thus, it helps to automate the process of configuration changes for serial robot manipulators. If the manipulator undergoes a geometric change, such as tool acquisition, then JFKengine can be invoked again from the control or simulation software, passing it parameters for the new arm configuration. This report describes the automated processes that are implemented by JFKengine to derive the kinematic equations and the programming interface by which it is invoked. Then it discusses the tree data structure that was chosen to store the expressions, followed by several examples of portions of expressions as represented in the tree. The C++ classes and their methods that implement the expression differentiation and evaluation operations are described. The algorithms used to construct the Jacobian and forward kinematic equations using these basic building blocks are then illustrated. The activity described in this report is part of a larger project entitled ''Multi-Optimization Criteria-Based Robot Behavioral Adaptability and Motion Planning'' that focuses on the development of a methodology for the generalized resolution of robot motion equations with time-varying configurations, constraints, and task objective criteria. A specific

  7. 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...

  8. A non-uniform distribution of the nearest brown dwarfs

    CERN Document Server

    Bihain, G

    2016-01-01

    The census of solar neighbours is still complemented by new discoveries, mainly of very low-mass, faint dwarfs, close to or within the substellar domain. These discoveries contribute to a better understanding of the field population; its origin in terms of Galactic dynamics and (sub)stellar formation and evolution. Also, the nearest stars and brown dwarfs at any given age allow the most precise direct characterization, including the search for planetary companions. We aim to further assess the substellar census on the Galactic plane. We projected the 136 stars and 26 brown dwarfs known at <6.5 pc on the Galactic plane and evaluated their distributions. Stars present a uniform- and brown dwarfs a non-uniform distribution, with 21 objects behind the Sun and only five ahead relative to the direction of rotation of the Galaxy. This substellar configuration has a probability of 0.098$^{+10.878}_{-0.098}$% relative to uniformity. The helio- and geocentric nature of the distribution suggests it might result in pa...

  9. Microlensing Binaries with Candidate Brown Dwarf Companions

    DEFF Research Database (Denmark)

    Shin, I.-G; Han, C.; Gould, A.

    2012-01-01

    Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation histories. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing...... masses of the brown dwarf companions are 0.02 ± 0.01 M⊙ and 0.019 ± 0.002 M⊙ for MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149, respectively, and both companions are orbiting low-mass M dwarf host stars. More microlensing brown dwarfs are expected to be detected as the number of lensing events...

  10. Future Observations of White Dwarfs from Space

    Science.gov (United States)

    Barstow, M. A.; Casewell, S. L.

    2015-06-01

    We outline two possible future space missions suitable for the study of white dwarfs. These lie at the extreme ends of the spectrum of such opportunities in terms of cost and timescale. The SIRIUS extreme ultraviolet spectrograph will be proposed for the ESA/Chinese Academy of Sciences small, ≍ 50M Euro, mission. If selected it will fly in 2021. ATLAST is planned to be a very large UVOIR space observatory to provide a true replacement for the capabilities of HST. If it goes ahead, it will be a several billion-dollar project and will not fly before 2030. The paper provides further details on the technical capabilities of these space telescopes.

  11. Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition

    CERN Document Server

    Burgasser, A J; Cruz, K L; Reid, I N; Leggett, S K; Liebert, J; Burrows, A; Brown, M E; Burgasser, Adam J.; Cruz, Kelle L.; Leggett, Sandy K.; Liebert, James; Burrows, Adam; Brown, Michael E.

    2006-01-01

    We present the results of a Hubble Space Telescope NICMOS imaging survey of 22 T-type field brown dwarfs. Five are resolved as binary systems with angular separations of 0"05-0"35, and companionship is established on the basis of component F110W-F170M colors (indicative of CH4 absorption) and low probabilities of background contamination. Prior ground-based observations show 2MASS 1553+1532AB to be a common proper motion binary. The properties of these systems - low multiplicity fraction (11[+7][-3]% resolved, as corrected for sample selection baises), close projected separations (a = 1.8-5.0 AU) and near-unity mass ratios - are consistent with previous results for field brown dwarf binaries. Three of the binaries have components that span the poorly-understood transition between L dwarfs and T dwarfs. Spectral decomposition analysis of one of these, SDSS 1021-0304AB, reveals a peculiar flux reversal between its components, as its T5 secondary is ~30% brighter at 1.05 and 1.27 micron than its T1 primary. This...

  12. Decoupling Kinematic Loops for Real-Time Multibody Dynamic Simulations

    Directory of Open Access Journals (Sweden)

    Omar Mohamed

    2016-01-01

    Full Text Available Earth moving equipment are typically equipped with hydraulic cylinder actuators to perform the designated tasks. Multibody modelling of such systems results in models with kinematic loops that couples the motion variables of the loop bodies. Iterative solutions will be needed to satisfy the loop constraints and the applied constraints, which require evaluation of the constraint Jacobean matrix. The size of the Jacobean matrix and the associated projections depends on the number of motion variables in each kinematic loop. Consequently, the computational cost significantly increases as the number of variables in the kinematic loop increases. Real-time control and hybrid hardware-in-the-loop systems both require efficient and fast computational algorithms. Eliminating the kinematic loops can improve the computational efficiency and effectiveness of the control algorithms. This paper presents an efficient approach to eliminate the coupling due to the cylinder-rod connections and consequently the kinematic loops in the multibody models leading to efficient simulation. The proposed approach calculates the spatial accelerations and inertia forces of the actuator bodies and the interaction forces with other components. The actuator forces are then projected onto the connecting bodies leading to exact dynamics of the system.

  13. Joint kinematic calculation based on clinical direct kinematic versus inverse kinematic gait models.

    Science.gov (United States)

    Kainz, H; Modenese, L; Lloyd, D G; Maine, S; Walsh, H P J; Carty, C P

    2016-06-14

    Most clinical gait laboratories use the conventional gait analysis model. This model uses a computational method called Direct Kinematics (DK) to calculate joint kinematics. In contrast, musculoskeletal modelling approaches use Inverse Kinematics (IK) to obtain joint angles. IK allows additional analysis (e.g. muscle-tendon length estimates), which may provide valuable information for clinical decision-making in people with movement disorders. The twofold aims of the current study were: (1) to compare joint kinematics obtained by a clinical DK model (Vicon Plug-in-Gait) with those produced by a widely used IK model (available with the OpenSim distribution), and (2) to evaluate the difference in joint kinematics that can be solely attributed to the different computational methods (DK versus IK), anatomical models and marker sets by using MRI based models. Eight children with cerebral palsy were recruited and presented for gait and MRI data collection sessions. Differences in joint kinematics up to 13° were found between the Plug-in-Gait and the gait 2392 OpenSim model. The majority of these differences (94.4%) were attributed to differences in the anatomical models, which included different anatomical segment frames and joint constraints. Different computational methods (DK versus IK) were responsible for only 2.7% of the differences. We recommend using the same anatomical model for kinematic and musculoskeletal analysis to ensure consistency between the obtained joint angles and musculoskeletal estimates.

  14. Another baryon miracle? Testing solutions to the "missing dwarfs" problem

    CERN Document Server

    Trujillo-Gomez, Sebastian; Papastergis, Emmanouil; Reed, Darren S; Lake, George

    2016-01-01

    No explanation exists so far for the observed dearth of dwarf galaxies in the local universe compared to the large number of dark matter halos predicted by $\\Lambda$CDM. Although attempts have been made to attribute the discrepancy to observational systematics, this would require an extreme modification of the density profiles of haloes through baryonic processes. In this paper we perform a systematic evaluation of the uncertainties affecting the measurement of DM halo abundance using galaxy kinematics. Including observational systematics and modelling uncertainties, we derive the abundance of galaxies as a function of maximum circular velocity --a direct probe of mass-- from the observed line-of-sight velocity function in the Local Volume. This provides a direct means of comparing the predictions of theoretical models and simulations (including nonstandard cosmologies and novel galaxy formation physics) to the observational constraints. The new "galactic $V_{max}$" function is steeper than the line-of-sight ...

  15. An Extended Star Formation History in an Ultra Compact Dwarf

    CERN Document Server

    Norris, Mark A; Faifer, Favio R; Kannappan, Sheila J; Forte, Juan Carlos; Bosch, Remco C E van den

    2015-01-01

    There has been significant controversy over the mechanisms responsible for forming compact stellar systems like ultra compact dwarfs (UCDs), with suggestions that UCDs are simply the high mass extension of the globular cluster (GC) population, or alternatively, the liberated nuclei of galaxies tidally stripped by larger companions. Definitive examples of UCDs formed by either route have been difficult to find, with only a handful of persuasive examples of stripped-nucleus type UCDs being known. In this paper we present very deep Gemini/GMOS spectroscopic observations of the suspected stripped nucleus UCD NGC 4546-UCD1 taken in good seeing conditions (< 0.7"). With these data we examine the spatially resolved kinematics and star formation history of this unusual object. We find no evidence of a rise in the central velocity dispersion of the UCD, suggesting that this UCD lacks a massive central black hole like those found in some other compact stellar systems, a conclusion confirmed by detailed dynamical mod...

  16. White dwarfs in cataclysmic variables

    Science.gov (United States)

    Gaensicke, Boris

    2016-07-01

    Cataclysmic variables (CVs) provide excellent laboratories to study the effect that the accretion of matter, energy and angular momentum has on the structure of white dwarfs, with important implications on the evolution of these compact binaries, the ignition of thermonuclear surface burning, and potentially their explosion as SNIa. I will provide an overview of our current understanding of CV white dwarfs, with a particular emphasis on the results of a recent large HST program. I will review our knowledge regarding the mass distribution of CV white dwarfs, as well as the secular mean accretion rates that can be inferred from their effective temperatures, and compare those statistics with predictions from CV population models. I will also discuss a sub-set of CVs which underwent thermal-time scale mass transfer, one of the channels that is often discussed as a pathway to SN Ia, and I will illustrate how the study of these "failed SNIa" can contribute to the discussion of SNIa progenitors. Finally, I will discuss the occurrence of non-radial pulsations in white dwarfs, both in CVs and their detached progenitors.

  17. Manganese in dwarf spheroidal galaxies

    NARCIS (Netherlands)

    North, P.; Cescutti, G.; Jablonka, P.; Hill, V.; Shetrone, M.; Letarte, B.; Lemasle, B.; Venn, K. A.; Battaglia, G.; Tolstoy, E.; Irwin, M. J.; Primas, F.; Francois, P.

    We provide manganese abundances (corrected for the effect of the hyperfine structure) for a large number of stars in the dwarf spheroidal galaxies Sculptor and Fornax, and for a smaller number in the Carina and Sextans dSph galaxies. Abundances had already been determined for a number of other

  18. Planets Around Low-Mass Stars (PALMS). III. A Young Dusty L Dwarf Companion at the Deuterium-Burning Limit

    CERN Document Server

    Bowler, Brendan P; Shkolnik, Evgenya L; Dupuy, Trent J

    2013-01-01

    We report the discovery of an L-type companion to the young M3.5V star 2MASS J01225093-2439505 at a projected separation of 1.45" (~52 AU) as part of our adaptive optics imaging search for extrasolar giant planets around young low-mass stars. 2MASS 0122-2439 B has very red near-infrared colors similar to the HR 8799 planets and the reddest known young/dusty L dwarfs in the field. Moderate-resolution (R~3800) 1.5-2.4 $\\mu$m spectroscopy reveals a near-infrared spectral type of L4-L6 and an angular H-band shape, confirming its cool temperature and young age. The kinematics of 2MASS 0122-2439 AB are marginally consistent with members of the ~120 Myr AB Dor young moving group based on the photometric distance to the primary (36 +/- 4 pc) and our radial velocity measurement of 2MASS 0122-2439 A from Keck/HIRES. We adopt the AB Dor group age for the system, but the high energy emission, lack of Li I $\\lambda$6707 absorption, and spectral shape of 2MASS 0122-2439 B suggest a range of ~10-120 Myr is possible. The age...

  19. Kinematic precision of gear trains

    Science.gov (United States)

    Litvin, F. L.; Goldrich, R. N.; Coy, J. J.; Zaretsky, E. V.

    1982-01-01

    Kinematic precision is affected by errors which are the result of either intentional adjustments or accidental defects in manufacturing and assembly of gear trains. A method for the determination of kinematic precision of gear trains is described. The method is based on the exact kinematic relations for the contact point motions of the gear tooth surfaces under the influence of errors. An approximate method is also explained. Example applications of the general approximate methods are demonstrated for gear trains consisting of involute (spur and helical) gears, circular arc (Wildhaber-Novikov) gears, and spiral bevel gears. Gear noise measurements from a helicopter transmission are presented and discussed with relation to the kinematic precision theory.

  20. Kinematic precision of gear trains

    Science.gov (United States)

    Litvin, F. L.; Goldrich, R. N.; Coy, J. J.; Zaretsky, E. V.

    1983-01-01

    Kinematic precision is affected by errors which are the result of either intentional adjustments or accidental defects in manufacturing and assembly of gear trains. A method for the determination of kinematic precision of gear trains is described. The method is based on the exact kinematic relations for the contact point motions of the gear tooth surfaces under the influence of errors. An approximate method is also explained. Example applications of the general approximate methods are demonstrated for gear trains consisting of involute (spur and helical) gears, circular arc (Wildhaber-Novikov) gears, and spiral bevel gears. Gear noise measurements from a helicopter transmission are presented and discussed with relation to the kinematic precision theory. Previously announced in STAR as N82-32733

  1. LIVE KINEMATIC MODELS IN MATHCAD

    Directory of Open Access Journals (Sweden)

    Valery F. Ochkov

    2013-01-01

    Full Text Available The paper considers creating animation of different kinematical devices in mathematical package Mathcad (steam engine, windscreen wipers, walking machine. Mathematical tools for solving algebraic equations and their systems are described. 

  2. Tensor Networks from Kinematic Space

    CERN Document Server

    Czech, Bartlomiej; McCandlish, Samuel; Sully, James

    2015-01-01

    We point out that the MERA network for the ground state of a 1+1-dimensional conformal field theory has the same structural features as kinematic space---the geometry of CFT intervals. In holographic theories kinematic space becomes identified with the space of bulk geodesics studied in integral geometry. We argue that in these settings MERA is best viewed as a discretization of the space of bulk geodesics rather than of the bulk geometry itself. As a test of this kinematic proposal, we compare the MERA representation of the thermofield-double state with the space of geodesics in the two-sided BTZ geometry, obtaining a detailed agreement which includes the entwinement sector. We discuss how the kinematic proposal can be extended to excited states by generalizing MERA to a broader class of compression networks.

  3. Tensor networks from kinematic space

    Science.gov (United States)

    Czech, Bartlomiej; Lamprou, Lampros; McCandlish, Samuel; Sully, James

    2016-07-01

    We point out that the MERA network for the ground state of a 1+1-dimensional conformal field theory has the same structural features as kinematic space — the geometry of CFT intervals. In holographic theories kinematic space becomes identified with the space of bulk geodesics studied in integral geometry. We argue that in these settings MERA is best viewed as a discretization of the space of bulk geodesics rather than of the bulk geometry itself. As a test of this kinematic proposal, we compare the MERA representation of the thermofield-double state with the space of geodesics in the two-sided BTZ geometry, obtaining a detailed agreement which includes the entwinement sector. We discuss how the kinematic proposal can be extended to excited states by generalizing MERA to a broader class of compression networks.

  4. THREE NEW ECLIPSING WHITE-DWARF-M-DWARF BINARIES DISCOVERED IN A SEARCH FOR TRANSITING PLANETS AROUND M-DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Law, Nicholas M. [Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George St., Toronto, ON M5S 3H4 (Canada); Kraus, Adam L. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Street, Rachel; Fulton, Benjamin J.; Shporer, Avi; Lister, Tim [Las Cumbres Observatory Global Telescope Network, Inc., 6740 Cortona Dr. Suite 102, Santa Barbara, CA 93117 (United States); Hillenbrand, Lynne A.; Baranec, Christoph; Bui, Khanh; Davis, Jack T. C.; Dekany, Richard G.; Kulkarni, S. R.; Ofek, Eran O. [Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Bloom, Joshua S.; Cenko, S. Bradley; Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Burse, Mahesh P.; Das, H. K. [Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune-411007 (India); Kasliwal, Mansi M. [Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (United States); Nugent, Peter [Computational Cosmology Center, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); and others

    2012-10-01

    We present three new eclipsing white-dwarf/M-dwarf binary systems discovered during a search for transiting planets around M-dwarfs. Unlike most known eclipsing systems of this type, the optical and infrared emission is dominated by the M-dwarf components, and the systems have optical colors and discovery light curves consistent with being Jupiter-radius transiting planets around early M-dwarfs. We detail the PTF/M-dwarf transiting planet survey, part of the Palomar Transient Factory (PTF). We present a graphics processing unit (GPU)-based box-least-squares search for transits that runs approximately 8 Multiplication-Sign faster than similar algorithms implemented on general purpose systems. For the discovered systems, we decompose low-resolution spectra of the systems into white-dwarf and M-dwarf components, and use radial velocity measurements and cooling models to estimate masses and radii for the white dwarfs. The systems are compact, with periods between 0.35 and 0.45 days and semimajor axes of approximately 2 R{sub Sun} (0.01 AU). The M-dwarfs have masses of approximately 0.35 M{sub Sun }, and the white dwarfs have hydrogen-rich atmospheres with temperatures of around 8000 K and have masses of approximately 0.5 M{sub Sun }. We use the Robo-AO laser guide star adaptive optics system to tentatively identify one of the objects as a triple system. We also use high-cadence photometry to put an upper limit on the white-dwarf radius of 0.025 R{sub Sun} (95% confidence) in one of the systems. Accounting for our detection efficiency and geometric factors, we estimate that 0.08%{sub -0.05%}{sup +0.10%} (90% confidence) of M-dwarfs are in these short-period, post-common-envelope white-dwarf/M-dwarf binaries where the optical light is dominated by the M-dwarf. The lack of detections at shorter periods, despite near-100% detection efficiency for such systems, suggests that binaries including these relatively low-temperature white dwarfs are preferentially found at

  5. Four Faint T Dwarfs from the UKIRT Infrared Deep Sky Survey (UKIDSS) Southern Stripe

    CERN Document Server

    Chiu, Kuenley; Jiang, Linhua; Allers, Katelyn N; Stark, Daniel P; Bunker, Andrew; Fan, Xiaohui; Glazebrook, Karl; Dupuy, Trent J

    2007-01-01

    We present the optical and near-infrared photometry and spectroscopy of four faint T dwarfs newly discovered from the UKIDSS first data release. The sample, drawn from an imaged area of ~136 square degrees to a depth of Y=19.9 (5-sigma, Vega), is located in the SDSS Southern Equatorial Stripe, a region of significant future deep imaging potential. We detail the selection and followup of these objects, three of which are spectroscopically confirmed brown dwarfs ranging from type T2.5 to T7.5, and one is photometrically identified as early T. Their magnitudes range from Y=19.01 to 19.88 with derived distances from 34 to 98 pc, making these among the coldest and faintest brown dwarfs known. The sample brings the total number of T dwarfs found or confirmed by UKIDSS data in this region to nine, and we discuss the projected numbers of dwarfs in the future survey data. We estimate that ~240 early- and late-T dwarfs are discoverable in the UKIDSS LAS data, falling significantly short of published model projections a...

  6. A Virtual Observatory Census to Address Dwarfs Origins (AVOCADO). I. Science goals, sample selection, and analysis tools

    Science.gov (United States)

    Sánchez-Janssen, R.; Amorín, R.; García-Vargas, M.; Gomes, J. M.; Huertas-Company, M.; Jiménez-Esteban, F.; Mollá, M.; Papaderos, P.; Pérez-Montero, E.; Rodrigo, C.; Sánchez Almeida, J.; Solano, E.

    2013-06-01

    Context. Even though they are by far the most abundant of all galaxy types, the detailed properties of dwarf galaxies are still only poorly characterised - especially because of the observational challenge that their intrinsic faintness and weak clustering properties represent. Aims: AVOCADO aims at establishing firm conclusions on the formation and evolution of dwarf galaxies by constructing and analysing a homogeneous, multiwavelength dataset for a statistically significant sample of approximately 6500 nearby dwarfs (Mi - 5 log h100 > - 18 mag). The sample is selected to lie within the 20 < D < 60 h100-1 Mpc volume covered by the SDSS-DR7 footprint, and is thus volume-limited for Mi - 5 log h100 < -16 mag dwarfs - but includes ≈1500 fainter systems. We will investigate the roles of mass and environment in determining the current properties of the different dwarf morphological types - including their structure, their star formation activity, their chemical enrichment history, and a breakdown of their stellar, dust, and gas content. Methods: We present the sample selection criteria and describe the suite of analysis tools, some of them developed in the framework of the Virtual Observatory. We use optical spectra and UV-to-NIR imaging of the dwarf sample to derive star formation rates, stellar masses, ages, and metallicities - which are supplemented with structural parameters that are used to classify them morphologically. This unique dataset, coupled with a detailed characterisation of each dwarf's environment, allows for a fully comprehensive investigation of their origins and enables us to track the (potential) evolutionary paths between the different dwarf types. Results: We characterise the local environment of all dwarfs in our sample, paying special attention to trends with current star formation activity. We find that virtually all quiescent dwarfs are located in the vicinity (projected distances ≲ 1.5 h100-1 Mpc) of ≳ L∗ companions, consistent with

  7. A nearby young M dwarf with a wide, possibly planetary-mass companion

    CERN Document Server

    Deacon, Niall R; Murphy, Simon J

    2016-01-01

    We present the identification of two previously known young objects in the solar neighbourhood as a likely very wide binary. TYC 9486-927-1, an active, rapidly rotating early-M dwarf, and 2MASS J21265040-8140293, a low-gravity L3 dwarf previously identified as candidate members of the $\\sim$45 Myr old Tucana Horologium association (TucHor). An updated proper motion measurement of the L3 secondary, and a detailed analysis of the pair's kinematics in the context of known nearby, young stars, reveals that they share common proper motion and are likely bound. New observations and analyses reveal the primary exhibits Li 6708~\\AA~absorption consistent with M dwarfs younger than TucHor but older than the $\\sim$10 Myr TW Hydra association yielding an age range of 10-45 Myr. A revised kinematic analysis suggests the space motions and positions of the pair are closer to, but not entirely in agreement with, the $\\sim$24 Myr old $\\beta$ Pictoris moving group. This revised 10-45 Myr age range yields a mass range of 11.6--...

  8. HI Observations of two New Dwarf Galaxies: Pisces A & B with the SKA Pathfinder KAT-7

    CERN Document Server

    Carignan, C; Lucero, D M; Randriamampandry, T H; Jarrett, T H; Oosterloo, T A; Tollerud, E J

    2016-01-01

    Context. Pisces A & Pisces B are the only two galaxies found via optical imaging and spectroscopy out of 22 HI clouds identified in the GALFAHI survey as dwarf galaxy candidates. Aims. Derive the HI content and kinematics of Pisces A & B. Methods. Aperture synthesis HI observations using the seven dish Karoo Array Telescope (KAT-7), which is a pathfinder instrument for MeerKAT, the South African precursor to the mid-frequency Square Kilometre Array (SKA-MID). Results. The small rotation velocities detected of ~5 km/sec and ~10 km/sec in Pisces A & B respectively, and their HI content show that they are really dwarf irregular galaxies (dIrr). Despite that small rotation component, it is more the random motions ~9-11 km/sec that provide most of the gravitational support, especially in the outer parts. The study of their kinematics, especially the strong gradients of random motions, suggest that those two dwarf galaxies are not yet in equilibrium. Conclusions. These HI rich galaxies may be indicative...

  9. The EBLM Project I-Physical and orbital parameters, including spin-orbit angles, of two low-mass eclipsing binaries on opposite sides of the Brown Dwarf limit

    CERN Document Server

    Triaud, Amaury H M J; Anderson, David R; Cargile, Phill; Cameron, Andrew Collier; Doyle, Amanda P; Faedi, Francesca; Gillon, Michaël; Chew, Yilen Gomez Maqueo; Hellier, Coel; Jehin, Emmanuel; Maxted, Pierre; Naef, Dominique; Pepe, Francesco; Pollacco, Don; Queloz, Didier; Ségransan, Damien; Smalley, Barry; Stassun, Keivan; Udry, Stéphane; West, Richard G

    2012-01-01

    This paper introduces a series of papers aiming to study the dozens of low mass eclipsing binaries (EBLM), with F, G, K primaries, that have been discovered in the course of the WASP survey. Our objects are mostly single-line binaries whose eclipses have been detected by WASP and were initially followed up as potential planetary transit candidates. These have bright primaries, which facilitates spectroscopic observations during transit and allows the study of the spin-orbit distribution of F, G, K+M eclipsing binaries through the Rossiter-McLaughlin effect. Here we report on the spin-orbit angle of WASP-30b, a transiting brown dwarf, and improve its orbital parameters. We also present the mass, radius, spin-orbit angle and orbital parameters of a new eclipsing binary, J1219-39b (1SWAPJ121921.03-395125.6, TYC 7760-484-1), which, with a mass of 95 +/- 2 Mjup, is close to the limit between brown dwarfs and stars. We find that both objects orbit in planes that appear aligned with their primaries' equatorial plane...

  10. The Galaxy in Context: Structural, Kinematic, and Integrated Properties

    Science.gov (United States)

    Bland-Hawthorn, Joss; Gerhard, Ortwin

    2016-09-01

    Our Galaxy, the Milky Way, is a benchmark for understanding disk galaxies. It is the only galaxy whose formation history can be studied using the full distribution of stars from faint dwarfs to supergiants. The oldest components provide us with unique insight into how galaxies form and evolve over billions of years. The Galaxy is a luminous (L⋆) barred spiral with a central box/peanut bulge, a dominant disk, and a diffuse stellar halo. Based on global properties, it falls in the sparsely populated “green valley” region of the galaxy color-magnitude diagram. Here we review the key integrated, structural and kinematic parameters of the Galaxy, and point to uncertainties as well as directions for future progress. Galactic studies will continue to play a fundamental role far into the future because there are measurements that can only be made in the near field and much of contemporary astrophysics depends on such observations.

  11. The Galaxy in Context: Structural, Kinematic and Integrated Properties

    CERN Document Server

    Bland-Hawthorn, Joss

    2016-01-01

    Our Galaxy, the Milky Way, is a benchmark for understanding disk galaxies. It is the only galaxy whose formation history can be studied using the full distribution of stars from white dwarfs to supergiants. The oldest components provide us with unique insight into how galaxies form and evolve over billions of years. The Galaxy is a luminous (L-star) barred spiral with a central box/peanut bulge, a dominant disk, and a diffuse stellar halo. Based on global properties, it falls in the sparsely populated "green valley" region of the galaxy colour-magnitude diagram. Here we review the key integrated, structural and kinematic parameters of the Galaxy, and point to uncertainties as well as directions for future progress. Galactic studies will continue to play a fundamental role far into the future because there are measurements that can only be made in the near field and much of contemporary astrophysics depends on such observations.

  12. Candidate tidal dwarf galaxies associated with the Stephan's Quintet

    CERN Document Server

    De Oliveira, C M; Amram, P; Balkowski, C; Bolte, M

    2001-01-01

    We present kinematic and photometric evidence for the presence of seven candidate tidal dwarf galaxies in Stephan's quintet. The central regions of the two most probable parent galaxies, N7319 and N7318B, contain little or no gas whereas the intragroup medium, and particularly the optical tails that seem to be associated with N7318B are rich in cold and ionized gas. Two tidal-dwarf candidates may be located at the edge of a tidal tail, one within a tail and for four others there is no obvious stellar/gaseous bridge between them and the parent galaxy. Two of the candidates are associated with HI clouds, one of which is, in addition, associated with a CO cloud. All seven regions have low continuum fluxes and high H$\\alpha$ luminosity densities (F(H$\\alpha$) = 1 -- 60 $\\times$ 10$^{-14}$ erg s$^{-1}$ cm$^{-2}$). Their magnitudes (M$_B =$ --16.1 to --12.6), sizes ($\\sim$ 3.5 h$_{75}^{-1}$ kpc), colors (typically $B-R = 0.7$) and gas velocity gradients ($\\sim$ 8 -- 26 h$_{75}$ km s$^{-1}$ kpc$^{-1}$) are typical f...

  13. New dwarf galaxy candidates in the Centaurus group

    CERN Document Server

    Müller, Oliver; Binggeli, Bruno

    2015-01-01

    Recent studies of the distribution and kinematics of the Milky Way and Andromeda satellite galaxy systems have confirmed the existence of coplanar, corotating structures of galaxies. In addition to the 'missing satellite problem', these structures pose a major challenge to the standard $\\Lambda$CDM scenario of structure formation. We complement the efforts made by the dwarf galaxy community to extend these studies to other nearby galaxy groups by systematically searching for faint, unresolved dwarf members with a low surface brightness in the Southern Centaurus group of galaxies. The aim is to determine whether these coplanar, corotating structures are a universal phenomenon. We imaged an area of 60 square degrees (0.3 Mpc$^2$) around the M83 subgroup with the wide-field Dark Energy Camera (DECam) at the CTIO 4 m Blanco telescope in $g$ and $r$ down to a limiting surface brightness of $\\mu_r\\approx 30$ mag arcsec$^{-2}$. Various image-filtering techniques were applied to the DECam data to enhance the visibili...

  14. Kinematical Analysis of an Articulated Mechanism

    CERN Document Server

    Fleischfresser, Luciano

    2015-01-01

    The purpose of this work is twofold: to present mathematical expressions for the kinematics of an articulated mechanism and to perform numerical experiments with the implemented Fortran code. The system of rigid parts is made of two slender bars and a disk. A constant 2 rad/s counterclockwise rotation rate is imposed on the disk triggering the planar motion of the longer bar (link) and the rotation of the shorter one (output). Angular relations, velocities and accelerations are analyzed for a 90-degree turn of the disk. The inversion of the linking bar sense of rotation is well captured by the simulation, and the paper and pencil solutions that may lead to wrong conclusions are explained. Equations are derived from first principles and the Fortran code is placed under version control (currently, v.0.8-beta). This computer project is relevant for those in charge of vector dynamics courses and wishing to expose students to project-based learning activities.

  15. AR Sco: A White Dwarf Synchronar

    CERN Document Server

    Katz, J I

    2016-01-01

    The emission of the white dwarf-M dwarf binary AR Sco is driven by the rapid synchronization of its white dwarf, rather than by accretion. This requires a comparatively large magnetic field $\\sim 100$ gauss at the M dwarf and $\\sim 10^8$ gauss on the white dwarf, larger than the fields of most intermediate polars but within the range of fields of known magnetic white dwarfs. The spindown power is dissipated in the atmosphere of the M dwarf by magnetic reconnection, accelerating particles that produce the observed synchrotron radiation. The displacement of the optical maximum from conjunction may be explained either by dissipation in a bow wave as the white dwarf's magnetic field sweeps past the M dwarf or by a misaligned white dwarf's rotation axis and oblique magnetic moment. In the latter case the rotation axis precesses with a period of decades, predicting a drift in the orbital phase of maximum. Binaries whose emission is powered by synchronization may be termed synchronars, in analogy to magnetars.

  16. Identifying the Young Low-mass Stars within 25 pc. II. Distances, Kinematics, and Group Membership

    Science.gov (United States)

    Shkolnik, Evgenya L.; Anglada-Escudé, Guillem; Liu, Michael C.; Bowler, Brendan P.; Weinberger, Alycia J.; Boss, Alan P.; Reid, I. Neill; Tamura, Motohide

    2012-10-01

    We have conducted a kinematic study of 165 young M dwarfs with ages of lsim300 Myr. Our sample is composed of stars and brown dwarfs with spectral types ranging from K7 to L0, detected by ROSAT and with photometric distances of lsim25 pc assuming that the stars are single and on the main sequence. In order to find stars kinematically linked to known young moving groups (YMGs), we measured radial velocities for the complete sample with Keck and CFHT optical spectroscopy and trigonometric parallaxes for 75 of the M dwarfs with the CAPSCam instrument on the du Pont 2.5 m Telescope. Due to their youthful overluminosity and unresolved binarity, the original photometric distances for our sample underestimated the distances by 70% on average, excluding two extremely young (lsim3 Myr) objects found to have distances beyond a few hundred parsecs. We searched for kinematic matches to 14 reported YMGs and identified 10 new members of the AB Dor YMG and 2 of the Ursa Majoris group. Additional possible candidates include six Castor, four Ursa Majoris, two AB Dor members, and one member each of the Her-Lyr and β Pic groups. Our sample also contains 27 young low-mass stars and 4 brown dwarfs with ages lsim150 Myr that are not associated with any known YMG. We identified an additional 15 stars that are kinematic matches to one of the YMGs, but the ages from spectroscopic diagnostics and/or the positions on the sky do not match. These warn against grouping stars together based only on kinematics and that a confluence of evidence is required to claim that a group of stars originated from the same star-forming event. Based on observations collected at the W. M. Keck Observatory, the Canada-France-Hawaii Telescope, the du Pont Telescope at Las Campanas Observatory, and the Subaru Telescope. The Keck Observatory is operated as a scientific partnership between the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial

  17. Sub-stellar objects with habitable-zone temperatures: A new search for Y dwarfs in WISE

    Directory of Open Access Journals (Sweden)

    Day-Jones Avril

    2013-04-01

    Full Text Available A method is defined for using the maximum sensitivity of WISE to find late T and Y dwarfs. This requires a WISE detection only in the W2-band and uses the statistical properties of the WISE multi-frame measurements and profile fit photometry to reject contamination resulting from non-point-like objects, variables and moving sources. To trace our desired parameter space we use a control sample of isolated non-moving non-variable point sources from the SDSS, and identify a sample of 158 WISE W2-only candidates down to a signal-to-noise limit of 8. For signal-to-noise ranges >10 and 8-10 respectively, ∼45% and ∼90% of our sample fall outside the criteria published by the WISE team (Kirkpatrick et al. 2012, due mainly to the type of constraints placed on the number of individual W2 detections. We present some early follow-up of our sample and identify two new very late objects with high proper motion (∼1.3 and ∼1.8 arcsec yr−1. Based on colour, brightness and proper motion, these object are either ∼T9 dwarfs with thick-disk/halo kinematics, or Y dwarfs with more disk-like kinematics. Reduced proper motion diagrams are also presented which suggest that late T and Y dwarfs may have a much higher thick-disk/halo population fraction than earlier objects.

  18. The most metal-poor damped Lyman alpha systems: An insight into dwarf galaxies at high redshift

    CERN Document Server

    Cooke, Ryan; Jorgenson, Regina A

    2014-01-01

    In this paper, we analyze the kinematics, chemistry, and physical properties of a sample of the most metal-poor damped Lyman alpha systems (DLAs), to uncover their links to modern-day galaxies. We present evidence that the DLA population as a whole exhibits a `knee' in the relative abundances of the alpha-capture and Fe-peak elements when the metallicity is [Fe/H] ~ -2.0. In this respect, the chemical evolution of DLAs is clearly different from that experienced by Milky Way halo stars, but resembles that of dwarf spheroidal galaxies in the Local Group. We also find a close correspondence between the kinematics of Local Group dwarf galaxies and of high redshift metal-poor DLAs, which further strengthens this connection. On the basis of such similarities, we propose that the most metal-poor DLAs provide us with a unique opportunity to directly study the dwarf galaxy population more than ten billion years in the past, at a time when many dwarf galaxies were forming the bulk of their stars. To this end, we have m...

  19. The Chromospheric Activity-Age Relation for M Dwarf Stars

    Science.gov (United States)

    Silvestri, N. M.; Oswalt, T. D.; Hawley, S. L.

    2000-12-01

    We present preliminary results from our study in which we use moderate resolution spectroscopy to determine the correlation between the chromospheric activity and age of M dwarf stars in wide binary systems. We have observed ~50 M dwarf stars from our sample with the Apache Point Observatory 3.5-m telescope. We measure the ratio of Hα luminosity to the bolometric luminosity (LHα /Lbol) of the M dwarf---a measure of activity that is proven to correlate well with age. This project is unique in that it will extend the chromospheric activity-age relation of low-mass main sequence stars beyond the ages provided by cluster methods. The ages so determined are also independent of the uncertainties in cluster age determinations. The technique has the potential to improve by at least a factor of two the precision and the range over which ages can currently be determined for main sequence stars. Work on this project is supported by the NASA Graduate Student Researchers Program grant NGT-50290 (N.M.S.).

  20. SDSS-IV MaNGA: Properties of galaxies with kinematically decoupled stellar and gaseous components

    CERN Document Server

    Jin, Yifei; Shi, Yong; Tremonti, C A; Bershady, M A; Merrifield, M; Emsellem, E; Fu, Hai; Wake, D; Bundy, K; Lin, Lihwai; Argudo-Fernandez, M; Huang, Song; Stark, D V; Storchi-Bergmann, T; Bizyaev, D; Brownstein, J; Chisholm, J; Guo, Qi; Hao, Lei; Hu, Jian; Li, Cheng; Li, Ran; Masters, K L; Malanushenko, E; Pan, Kaike; Riffel, R A; Roman-Lopes, A; Simmons, A; Thomas, D; Wang, Lan; Westfall, K; Yan, Renbin

    2016-01-01

    We study the properties of 66 galaxies with kinematically misaligned gas and stars from MaNGA survey. The fraction of kinematically misaligned galaxies varies with galaxy physical parameters, i.e. M*, SFR and sSFR. According to their sSFR, we further classify these 66 galaxies into three categories, 10 star-forming, 26 "Green Valley" and 30 quiescent ones. The properties of different types of kinematically misaligned galaxies are different in that the star-forming ones have positive gradient in D4000 and higher gas-phase metallicity, while the green valley/quiescent ones have negative D4000 gradients and lower gas-phase metallicity on average. There is evidence that all types of the kinematically misaligned galaxies tend to live in more isolated environment. Based on all these observational results, we propose a scenario for the formation of star forming galaxies with kinematically misaligned gas and stars - the progenitor accretes misaligned gas from a gas-rich dwarf or cosmic web, the cancellation of angula...

  1. Pan-Planets: Searching for hot Jupiters around cool dwarfs

    Science.gov (United States)

    Obermeier, C.; Koppenhoefer, J.; Saglia, R. P.; Henning, Th.; Bender, R.; Kodric, M.; Deacon, N.; Riffeser, A.; Burgett, W.; Chambers, K. C.; Draper, P. W.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E. A.; Metcalfe, N.; Price, P. A.; Sweeney, W.; Wainscoat, R. J.; Waters, C.

    2016-03-01

    The Pan-Planets survey observed an area of 42 sq deg. in the galactic disk for about 165 h. The main scientific goal of the project is the detection of transiting planets around M dwarfs. We establish an efficient procedure for determining the stellar parameters Teff and log g of all sources using a method based on SED fitting, utilizing a three-dimensional dust map and proper motion information. In this way we identify more than 60 000 M dwarfs, which is by far the largest sample of low-mass stars observed in a transit survey to date. We present several planet candidates around M dwarfs and hotter stars that are currently being followed up. Using Monte Carlo simulations we calculate the detection efficiency of the Pan-Planets survey for different stellar and planetary populations. We expect to find 3.0+3.3-1.6 hot Jupiters around F, G, and K dwarfs with periods lower than 10 days based on the planet occurrence rates derived in previous surveys. For M dwarfs, the percentage of stars with a hot Jupiter is under debate. Theoretical models expect a lower occurrence rate than for larger main sequence stars. However, radial velocity surveys find upper limits of about 1% due to their small sample, while the Kepler survey finds a occurrence rate that we estimate to be at least 0.17b(+0.67-0.04) %, making it even higher than the determined fraction from OGLE-III for F, G and K stellar types, 0.14 (+0.15-0.076) %. With the large sample size of Pan-Planets, we are able to determine an occurrence rate of 0.11 (+0.37-0.02) % in case one of our candidates turns out to be a real detection. If, however, none of our candidates turn out to be true planets, we are able to put an upper limit of 0.34% with a 95% confidence on the hot Jupiter occurrence rate of M dwarfs. This limit is a significant improvement over previous estimates where the lowest limit published so far is 1.1% found in the WFCAM Transit Survey. Therefore we cannot yet confirm the theoretical prediction of a lower

  2. COMPARING THE OBSERVABLE PROPERTIES OF DWARF GALAXIES ON AND OFF THE ANDROMEDA PLANE

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Michelle L. M.; Martin, Nicolas F. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Rich, R. M. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States); Ibata, Rodrigo A. [Observatoire de Strasbourg, 11, Rue de l' Université, F-67000 Strasbourg (France); Chapman, Scott C. [Department of Physics and Atmospheric Science, Dalhousie University, Coburg Road, Halifax B3H1A6 (Canada); McConnachie, Alan W. [NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, British Columbia, Victoria V9E 2E7 (Canada); Ferguson, Annette M. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Irwin, Michael J. [Institute of Astronomy, Madingley Rise, Cambridge CB3 0HA (United Kingdom); Lewis, Geraint F., E-mail: michelle.collins@yale.edu [Sydney Institute for Astronomy, School of Physics, A28, University of Sydney, NSW 2006 (Australia)

    2015-01-20

    The thin, extended planes of satellite galaxies detected around both the Milky Way and Andromeda are not a natural prediction of the Λ-cold dark matter paradigm. Galaxies in these distinct planes may have formed and evolved in a different way (e.g., tidally) from their off-plane neighbors. If this were the case, one would expect the on- and off-plane dwarf galaxies in Andromeda to have experienced different evolutionary histories, which should be reflected by the chemistries, dynamics, and star formation histories of the two populations. In this work, we present new, robust kinematic observations for two on-plane M31 dwarf spheroidal galaxies (And XVI and XVII) and compile and compare all available observational metrics for the on- and off-plane dwarfs to search for a signal that would corroborate such a hypothesis. We find that, barring their spatial alignment, the on- and off-plane Andromeda dwarf galaxies are indistinguishable from one another, arguing against vastly different formative and evolutionary histories for these two populations.

  3. A supermassive black hole in an ultra-compact dwarf galaxy.

    Science.gov (United States)

    Seth, Anil C; van den Bosch, Remco; Mieske, Steffen; Baumgardt, Holger; den Brok, Mark; Strader, Jay; Neumayer, Nadine; Chilingarian, Igor; Hilker, Michael; McDermid, Richard; Spitler, Lee; Brodie, Jean; Frank, Matthias J; Walsh, Jonelle L

    2014-09-18

    Ultra-compact dwarf galaxies are among the densest stellar systems in the Universe. These systems have masses of up to 2 × 10(8) solar masses, but half-light radii of just 3-50 parsecs. Dynamical mass estimates show that many such dwarfs are more massive than expected from their luminosity. It remains unclear whether these high dynamical mass estimates arise because of the presence of supermassive black holes or result from a non-standard stellar initial mass function that causes the average stellar mass to be higher than expected. Here we report adaptive optics kinematic data of the ultra-compact dwarf galaxy M60-UCD1 that show a central velocity dispersion peak exceeding 100 kilometres per second and modest rotation. Dynamical modelling of these data reveals the presence of a supermassive black hole with a mass of 2.1 × 10(7) solar masses. This is 15 per cent of the object's total mass. The high black hole mass and mass fraction suggest that M60-UCD1 is the stripped nucleus of a galaxy. Our analysis also shows that M60-UCD1's stellar mass is consistent with its luminosity, implying a large population of previously unrecognized supermassive black holes in other ultra-compact dwarf galaxies.

  4. HOW THE FIRST STARS SHAPED THE FAINTEST GAS-DOMINATED DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Verbeke, R.; Vandenbroucke, B.; Rijcke, S. De, E-mail: robbert.verbeke@UGent.be [Sterrenkundig Observatorium, Ghent University, Krijgslaan 281, S9, 9000 Gent (Belgium)

    2015-12-20

    Low-mass dwarf galaxies are very sensitive test-beds for theories of cosmic structure formation since their weak gravitational fields allow the effects of the relevant physical processes to clearly stand out. Up to now, no unified account has existed of the sometimes seemingly conflicting properties of the faintest isolated dwarfs in and around the Local Group, such as Leo T and the recently discovered Leo P and Pisces A systems. Using new numerical simulations, we show that this serious challenge to our understanding of galaxy formation can be effectively resolved by taking into account the regulating influence of the ultraviolet radiation of the first population of stars on a dwarf’s star formation rate while otherwise staying within the standard cosmological paradigm for structure formation. These simulations produce faint, gas-dominated, star-forming dwarf galaxies that lie on the baryonic Tully–Fisher relation and that successfully reproduce a broad range of chemical, kinematical, and structural observables of real late-type dwarf galaxies. Furthermore, we stress the importance of obtaining properties of simulated galaxies in a manner as close as possible to the typically employed observational techniques.

  5. Discovery of a Bright, Extremely Low-Mass White Dwarf in a Close Double Degenerate System

    CERN Document Server

    Vennes, S; Kawka, A; Nemeth, P; Skinner, J N; Pigulski, A; Steslicki, M; Kolaczkowski, Z; Srodka, P; 10.1088/2041-8205/737/1/L16

    2011-01-01

    We report the discovery of a bright (V ~ 13.7), extremely low-mass white dwarf in a close double degenerate system. We originally selected GALEX J171708.5+675712 for spectroscopic follow-up among a group of white dwarf candidates in an ultraviolet-optical reduced proper-motion diagram. The new white dwarf has a mass of 0.18 M_solar and is the primary component of a close double degenerate system (P=0.246137 d, K_1 = 288 km/s) comprising a fainter white dwarf secondary with M_2 ~ 0.9 M_solar. Light curves phased with the orbital ephemeris show evidence of relativistic beaming and weaker ellipsoidal variations. The light curves also reveal secondary eclipses (depth ~ 8 mmag) while the primary eclipses appear partially compensated by the secondary gravitational deflection and are below detection limits. Photospheric abundance measurements show a nearly solar composition of Si, Ca, and Fe (0.1-1 solar), while the normal kinematics suggest a relatively recent formation history. Close binary evolutionary scenarios ...

  6. A Near-Infrared Spectroscopic Study of Young Field Ultracool Dwarfs

    CERN Document Server

    Allers, K N

    2013-01-01

    We present a near-infrared (0.9-2.4 microns) spectroscopic study of 73 field ultracool dwarfs having spectroscopic and/or kinematic evidence of youth (~10-300 Myr). Our sample is composed of 48 low-resolution (R~100) spectra and 41 moderate-resolution spectra (R>~750-2000). First, we establish a method for spectral typing M5-L7 dwarfs at near-IR wavelengths that is independent of gravity. We find that both visual and index-based classification in the near-IR provide consistent spectral types with optical spectral types, though with a small systematic offset in the case of visual classification at J and K band. Second, we examine features in the spectra of ~10 Myr ultracool dwarfs to define a set of gravity-sensitive indices based on FeH, VO, K, Na and H-band continuum shape. We then create an index-based method for classifying the gravities of M6-L5 dwarfs that provides consistent results with gravity classifications from optical spectroscopy. Our index-based classification can distinguish between young and d...

  7. Theoretical lower limits on sizes of ultrafaint dwarf galaxies from dynamical friction

    Science.gov (United States)

    Hernandez, X.

    2016-11-01

    Dwarf spheroidal galaxies (dSphs) are the smallest known stellar systems where under Newtonian interpretations, a significant amount of dark matter is required to explain observed kinematics. In fact, they are, in this sense, the most heavily dark matter-dominated objects known. That, plus the increasingly small sizes of the newly discovered ultrafaint dwarfs, puts these systems in the regime where dynamical friction on individual stars starts to become relevant. We calculate the dynamical friction time-scales for pressure-supported isotropic spherical dark matter-dominated stellar systems, yielding τDF = 0.93(rh/10 pc)2(σ/km s-1) Gyr, where rh is the half-light radius. For a stellar velocity dispersion value of 3 km s-1, as typical for the smallest of the recently detected ultrafaint dwarf spheroidals, dynamical friction time-scales become smaller than the 10 Gyr typical of the stellar ages for these systems, for rh present a comparison with structural parameters of the smallest ultrafaint dwarf spheroidals known, showing that these are already close to the stability limit derived, any future detection of yet smaller such systems would be inconsistent with a particle dark matter hypothesis.

  8. Dark influences II: gas and star formation in minor mergers of dwarf galaxies with dark satellites

    CERN Document Server

    Starkenburg, Tjitske K; Sales, Laura V

    2015-01-01

    Mergers have been proposed to induce starbursts and to lead to important morphological changes in galaxies. Most studies so far have focused on large galaxies, but dwarfs might also experience such events, since the halo mass function is scale-free in the concordance cosmological model. Notably, because of their low mass, most of their interactions will be with dark satellites. In this paper we follow the evolution of gas-rich disky dwarf galaxies as they experience a minor merger with a dark satellite. We aim to characterize the effects of such an interaction on the dwarf's star formation, morphology and kinematical properties. We perform a suite of carefully set-up hydrodynamical simulations of dwarf galaxies that include dark matter, gas, and stars, merging with a satellite consisting solely of dark matter. For the host system we vary the gas fraction, disk size and thickness, halo mass and concentration, while for the satellite we explore different masses, concentrations and orbits. We find that the inter...

  9. Mg II & C IV Kinematics vs. Stellar Kinematics in Galaxies

    CERN Document Server

    Churchill, C W; Churchill, Chris; Steidel, Chuck

    2002-01-01

    Comparisons of the kinematics of Mg II absorbing gas and the stellar rotation curves in 0.5 < z < 1.0 spiral galaxies suggests that, at least in some cases, the extended gaseous envelopes may be dynamically coupled to the stellar matter. A strong correlation exists between the overall kinematic spread of Mg II absorbing gas and C IV absorption strength, and therefore kinematics of the higher-ionization gas. Taken together, the data may suggest a "halo/disk connection" between z~1 galaxies and their extended gaseous envelopes. Though the number of galaxies in our sample are few, there are no clear examples that suggest the gas is accreting/infalling isotropically about the galaxies from the intergalactic medium.

  10. New Low Surface Brightness Dwarf Galaxies Detected Around Nearby Spirals

    CERN Document Server

    Karachentsev, I D; Zilch, T; Blauensteiner, M; Elvov, M; Hochleitner, P; Hubl, B; Kerschhuber, G; Küppers, S; Neyer, F; Pölzl, R; Remmel, P; Schneider, O; Sparenberg, R; Trulson, U; Willems, G; Ziegler, H

    2015-01-01

    We conduct a survey of low surface brightness (LSB) satellite galaxies around the Local Volume massive spirals using long exposures with small amateur telescopes. We identified 27 low and very low surface brightness objects around the galaxies NGC,672, 891, 1156, 2683, 3344, 4258, 4618, 4631, and 5457 situated within 10 Mpc from us, and found nothing new around NGC,2903, 3239, 4214, and 5585. Assuming that the dwarf candidates are the satellites of the neighboring luminous galaxies, their absolute magnitudes are in the range of -8.6 > M_B > -13.3, their effective diameters are 0.4-4.7 kpc, and the average surface brightness is 26.1 mag/sq arcsec. The mean linear projected separation of the satellite candidates from the host galaxies is 73 kpc. Our spectroscopic observations of two LSB dwarfs with the Russian 6-meter telescope confirm their physical connection to the host galaxies NGC,891 and NGC,2683.

  11. A VIRIAL CORE IN THE SCULPTOR DWARF SPHEROIDAL GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Agnello, A.; Evans, N. W., E-mail: aagnello@ast.cam.ac.uk, E-mail: nwe@ast.cam.ac.uk [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)

    2012-08-01

    The projected virial theorem is applied to the case of multiple stellar populations in the nearby dwarf spheroidal galaxies. As each population must reside in the same gravitational potential, this provides strong constraints on the nature of the dark matter halo. We derive necessary conditions for two populations with Plummer or exponential surface brightnesses to reside in a cusped Navarro-Frenk-White (NFW) halo. We apply our methods to the Sculptor dwarf spheroidal, and show that there is no NFW halo compatible with the energetics of the two populations. The dark halo must possess a core radius of {approx}120 pc for the virial solutions for the two populations to be consistent. This conclusion remains true, even if the effects of flattening or self-gravity of the stellar populations are included.

  12. Jeans Analysis for Dwarf Spheroidal Galaxies in Wave Dark Matter

    CERN Document Server

    Chen, Shu-Rong; Chiueh, Tzihong

    2016-01-01

    Observations suggest that dwarf spheroidal (dSph) galaxies exhibit large constant-density cores in the centers, which can hardly be explained by dissipationless cold dark matter simulations. Wave dark matter (${\\psi {\\rm DM}}$), characterized by a single parameter, the dark matter particle mass $m_{\\psi}$, predicts a central soliton core in every galaxy arising from quantum pressure against gravity. Here we apply Jeans analysis to the kinematic data of eight classical dSphs so as to constrain $m_{\\psi}$, and obtain $m_{\\psi}=1.18_{-0.24}^{+0.28}\\times10^{-22}{\\,\\rm eV}$ and $m_{\\psi}=1.79_{-0.33}^{+0.35}\\times10^{-22}{\\,\\rm eV}~(2\\sigma)$ using the observational data sets of Walker et al. (2007) and Walker et al. (2009b), respectively. We show that the estimate of $m_{\\psi}$ is sensitive to the dSphs kinematic data sets and is robust to various models of stellar density profile. We also consider multiple stellar subpopulations in dSphs and find consistent results. This mass range of $m_{\\psi}$ is in good agre...

  13. Magnetic fields in Local Group dwarf irregulars

    CERN Document Server

    Chyzy, Krzysztof T; Beck, Rainer; Bomans, Dominik J

    2011-01-01

    We clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and what is the role of dwarf galaxies in the magnetization of the Universe. We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100m Effelsberg telescope at 2.64 and 4.85GHz. Magnetic fields in LG dwarfs are three times weaker than in the normal spirals (6muG) are observed only in dwarfs of extreme characteristics while typical LG dwarfs are not suitable objects for efficient supply of magnetic fields to the intergalactic medium.

  14. Missing dark matter in dwarf galaxies?

    Science.gov (United States)

    Oman, Kyle A.; Navarro, Julio F.; Sales, Laura V.; Fattahi, Azadeh; Frenk, Carlos S.; Sawala, Till; Schaller, Matthieu; White, Simon D. M.

    2016-08-01

    We use cosmological hydrodynamical simulations of the APOSTLE project along with high-quality rotation curve observations to examine the fraction of baryons in ΛCDM haloes that collect into galaxies. This `galaxy formation efficiency' correlates strongly and with little scatter with halo mass, dropping steadily towards dwarf galaxies. The baryonic mass of a galaxy may thus be used to place a lower limit on total halo mass and, consequently, on its asymptotic maximum circular velocity. A number of observed dwarfs seem to violate this constraint, having baryonic masses up to 10 times higher than expected from their rotation speeds, or, alternatively, rotating at only half the speed expected for their mass. Taking the data at face value, either these systems have formed galaxies with extraordinary efficiency - highly unlikely given their shallow potential wells - or their dark matter content is much lower than expected from ΛCDM haloes. This `missing dark matter' is reminiscent of the inner mass deficit of galaxies with slowly rising rotation curves, but cannot be explained away by star formation-induced `cores' in the dark mass profile, since the anomalous deficit applies to regions larger than the luminous galaxies themselves. We argue that explaining the structure of these galaxies would require either substantial modification of the standard ΛCDM paradigm or else significant revision to the uncertainties in their inferred mass profiles, which should be much larger than reported. Systematic errors in inclination may provide a simple resolution to what would otherwise be a rather intractable problem for the current paradigm.

  15. KINEMATIC DESIGN OF A RECONFIGURABLE MINIATURE PARALLEL KINEMATIC MACHINE

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The kinematic design of a reconfigurable miniature parallel kinematic machine is dealt with. It shows that the reconfigurability may be realized by packaging a tripod-based parallel mechanism with fixed length struts into a compact and rigid frame with which the different configurations can be formed. Utilizing a dual parameter model, the influences of the geometrical parameters on the dexterous performance and the workspace/machine volume ratio are investigated. A novel global performance index for the dimensional synthesis is proposed and optimized, resulting in a set of dimensionless geometrical parameters.

  16. Parametric Dwarf Spheroidal Tidal Interaction

    CERN Document Server

    Fleck, J J; Fleck, Jean-Julien; Kuhn, Jeff R.

    2003-01-01

    The time dependent tidal interaction of the Local Group Dwarf Spheroidal (dS) Galaxies with the Milky Way (MW) can fundamentally affect their dynamical properties. The model developed here extends earlier numerical descriptions of dS-MW tidal interactions. We explore the dynamical evolution of dS systems in circular or elliptical MW orbits in the framework of a parametric oscillator. An analytic model is developed and compared with more general numerical solutions and N-body simulation experiments.

  17. Dark matter in dwarf galaxies

    OpenAIRE

    Roos, Matts

    2017-01-01

    Although the cusp-core controversy for dwarf galaxies is seen as a problem, I argue that the cored central profiles can be explained by flattened cusps because they suffer from conflicting measurements and poor statistics and because there is a large number of conventional processes that could have flattened them since their creation, none of which requires new physics. Other problems, such as "too big to fail", are not discussed.

  18. pynoddy 1.0: an experimental platform for automated 3-D kinematic and potential field modelling

    Science.gov (United States)

    Florian Wellmann, J.; Thiele, Sam T.; Lindsay, Mark D.; Jessell, Mark W.

    2016-03-01

    We present a novel methodology for performing experiments with subsurface structural models using a set of flexible and extensible Python modules. We utilize the ability of kinematic modelling techniques to describe major deformational, tectonic, and magmatic events at low computational cost to develop experiments testing the interactions between multiple kinematic events, effect of uncertainty regarding event timing, and kinematic properties. These tests are simple to implement and perform, as they are automated within the Python scripting language, allowing the encapsulation of entire kinematic experiments within high-level class definitions and fully reproducible results. In addition, we provide a link to geophysical potential-field simulations to evaluate the effect of parameter uncertainties on maps of gravity and magnetics. We provide relevant fundamental information on kinematic modelling and our implementation, and showcase the application of our novel methods to investigate the interaction of multiple tectonic events on a pre-defined stratigraphy, the effect of changing kinematic parameters on simulated geophysical potential fields, and the distribution of uncertain areas in a full 3-D kinematic model, based on estimated uncertainties in kinematic input parameters. Additional possibilities for linking kinematic modelling to subsequent process simulations are discussed, as well as additional aspects of future research. Our modules are freely available on github, including documentation and tutorial examples, and we encourage the contribution to this project.

  19. pynoddy 1.0: an experimental platform for automated 3-D kinematic and potential field modelling

    Directory of Open Access Journals (Sweden)

    J. F. Wellmann

    2015-11-01

    Full Text Available We present a novel methodology for performing experiments with subsurface structural models using a set of flexible and extensible Python modules. We utilise the ability of kinematic modelling techniques to describe major deformational, tectonic, and magmatic events at low computational cost to develop experiments testing the interactions between multiple kinematic events, effect of uncertainty regarding event timing, and kinematic properties. These tests are simple to implement and perform, as they are automated within the Python scripting language, allowing the encapsulation of entire kinematic experiments within high-level class definitions and fully reproducible results. In addition, we provide a~link to geophysical potential-field simulations to evaluate the effect of parameter uncertainties on maps of gravity and magnetics. We provide relevant fundamental information on kinematic modelling and our implementation, and showcase the application of our novel methods to investigate the interaction of multiple tectonic events on a pre-defined stratigraphy, the effect of changing kinematic parameters on simulated geophysical potential-fields, and the distribution of uncertain areas in a full 3-D kinematic model, based on estimated uncertainties in kinematic input parameters. Additional possibilities for linking kinematic modelling to subsequent process simulations are discussed, as well as additional aspects of future research. Our modules are freely available on github, including documentation and tutorial examples, and we encourage the contribution to this project.

  20. The Structure of Brown Dwarf Circumstellar Disks

    OpenAIRE

    Walker, Christina; Wood, Kenneth; Lada, C. J.; Robitaille, Thomas; Bjorkman, J. E.; Whitney, Barbara

    2004-01-01

    We present synthetic spectra for circumstellar disks that are heated by radiation from a central brown dwarf. Under the assumption of vertical hydrostatic equilibrium, our models yield scaleheights for brown dwarf disks in excess of three times those derived for classical T Tauri (CTTS) disks. If the near-IR excess emission observed from brown dwarfs is indeed due to circumstellar disks, then the large scaleheights we find could have a significant impact on the optical and near-IR detectabili...

  1. Magnetars and White Dwarf Pulsars

    CERN Document Server

    Lobato, Ronaldo V; Coelho, Jaziel G

    2016-01-01

    The Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) are a class of pulsars understood as neutron stars (NSs) with super strong surface magnetic fields, namely $B\\gtrsim10^{14}$ G, and for that reason are known as Magnetars. However, in the last years some SGRs/AXPs with low surface magnetic fields $B\\sim(10^{12}-10^{13})$ G have been detected, challenging the Magnetar description. Moreover, some fast and very magnetic white dwarfs (WDs) have also been observed, and at least one showed X-Ray energy emission as an ordinary pulsar. Following this fact, an alternative model based on white dwarfs pulsars has been proposed to explain this special class of pulsars. In this model, AXPs and SGRs as dense and magnetized white dwarfs can have surface magnetic field $B\\sim 10^{7}-10^{10}$ G and rotate very fast with frequencies $\\Omega\\sim 1$ rad/s, consistent with the observed rotation periods $P\\sim (2-12)$ s.

  2. Microlensing, Brown Dwarfs and GAIA

    CERN Document Server

    Evans, N W

    2014-01-01

    The GAIA satellite can precisely measure the masses of nearby brown dwarfs and lower main sequence stars by the microlensing effect. The scientific yield is maximised if the microlensing event is also followed with ground-based telescopes to provide densely sampled photometry. There are two possible strategies. First, ongoing events can be triggered by photometric or astrometric alerts by GAIA. Second, events can be predicted using known high proper motion stars as lenses. This is much easier, as the location and time of an event can be forecast. Using the GAIA source density, we estimate that the sample size of high proper motion ($>300$ mas yr$^{-1}$) brown dwarfs needed to provide predictable events during the 5 year mission lifetime is surprisingly small, only of the order of a hundred. This is comparable to the number of high proper motion brown dwarfs already known from the work of the UKIDSS Large Area Survey and the all-sky WISE satellite. Provided the relative parallax of the lens and the angular Ein...

  3. Lopsidedness in dwarf irregular galaxies

    CERN Document Server

    Heller, A B; Almoznino, E; Van Zee, L; Salzer, J J; Heller, Ana B.; Brosch, Noah; Almoznino, Elchanan; Zee, Liese van; Salzer, John J.

    2000-01-01

    We quantify the amplitude of the lopsidedness, the azimuthal angular asymmetry index, and the concentration of star forming regions, as represented by the distribution of the H$\\alpha$ emission, in a sample of 78 late-type irregular galaxies. We bin the observed galaxies in two groups representing blue compact galaxies (BCDs) and low surface brightness dwarf galaxies (LSBs). The light distribution is analysed with a novel algorithm, which allows detection of details in the light distribution pattern. We find that while the asymmetry of the underlying continuum light, representing the older stellar generations, is relatively small, the H$\\alpha$ emission is very asymmetric and is correlated in position angle with the continuum light. We test a model of random star formation over the extent of a galaxy by simulating HII regions in artificial dwarf galaxies. The implication is that random star formation over the full extent of a galaxy may be generated in LSB dwarf-irregular galaxies but not in BCD galaxies.

  4. White Dwarf Critical Tests for Modified Gravity

    CERN Document Server

    Jain, Rajeev Kumar; Nielsen, Niklas Grønlund

    2015-01-01

    Scalar-tensor theories of gravity can lead to modifications of the gravitational force inside astrophysical objects. We exhibit that compact stars such as white dwarfs provide a unique set-up to test such deviations from Newtonian gravitational physics inside the stars. We obtain stringent and independent constraints on the parameter $\\Upsilon$ characterizing the deviations from gravity using the mass-radius relation, the Chandrasekhar mass limit and the maximal rotational frequency of white dwarfs. We find that white dwarfs impose stronger constraints on $\\Upsilon$ than the red and brown dwarfs.

  5. White dwarf cooling sequences and cosmochronology

    CERN Document Server

    Isern, J; Garcia-Berro, E

    2012-01-01

    The evolution of white dwarfs is a simple gravothermal process. This means that their luminosity function, i.e. the number of white dwarfs per unit bolometric magnitude and unit volume as a function of bolometric magnitude, is a monotonically increasing function that decreases abruptly as a consequence of the finite age of the Galaxy. The precision and the accuracy of the white dwarf luminosity functions obtained with the recent large surveys together with the improved quality of the theoretical models of evolution of white dwarfs allow to feed the hope that in a near future it will be possible to reconstruct the history of the different Galactic populations.

  6. The Blue Straggler Population in Dwarf Galaxies

    CERN Document Server

    Momany, Yazan

    2014-01-01

    In this chapter I review the recent developments regarding the study of Blue Stragglers (BSS) in dwarf galaxies. The loose density environment of dwarf galaxies resembles that of the Galactic Halo, hence it is natural to compare their common BSS properties. At the same time, it is unescapable to compare with the BSS properties in Galactic Globular clusters, which constitute the reference point for BSS studies. Admittedly, the literature on BSS in dwarf galaxies is not plentiful. The limitation is mostly due to the large distance to even the closest dwarf galaxies. Nevertheless, recent studies have allowed a deeper insight on the BSS photometric properties that are worth examining.

  7. Dynamical Masses of Accreting White Dwarfs

    Science.gov (United States)

    Pala, A. F.; Gänsckie, B. T.

    2017-03-01

    The mass retention efficiency is a key question in both the theoretical and observational study of accreting white dwarfs in interacting binaries, with important implications for their potential as progenitors for type Ia supernovae (SNe Ia). Canonical wisdom is that classical nova eruptions erode the white dwarf mass, and consequently, cataclysmic variables (CVs) have been excluded from the SN Ia progenitor discussion. However the average mass of white dwarfs in CVs is substantially higher (≃ 0.83 M⊙) than that of single white dwarfs (≃ 0.64 M ⊙), in stark contrast to expectations based on current classical nova models. This finding is based on a sample of ≃ 30 CV white dwarfs with accurate mass measurements, most of them in eclipsing systems. Given the fundamental importance of the mass evolution of accreting white dwarfs, it is necessary to enlarge this sample and to diversify the methods used for measuring masses. We have begun a systematic study of 27 CVs to almost double the number of CV white dwarfs with an accurate mass measurement. Using VLT/X-shooter phase-resolved observations, we can measure the white dwarf masses to a few percent, and will be able to answer the question whether accreting CV white dwarfs grow in mass.

  8. Kinematics in galactic tidal tails - A source for Hypervelocity stars?

    CERN Document Server

    Piffl, Tilmann; Steinmetz, Matthias

    2011-01-01

    [abridged] In this work we study in detail the kinematics of tidal debris stars to investigate the implications of the new scenario that the observed sample of Hypervelocity stars could partly originate from a dwarf-host galaxy collision. We use a suite of N-body simulations following the encounter of a satellite galaxy with its Milky Way-type host galaxy to gather statistics on the properties of stripped-off stars. We study especially the orbital energy distribution of this population. We quantify the typical pattern in angular and phase space formed by the debris stars. We further develop a simple stripping model predicting the kinematics of stripped-off stars. We show that the distribution of orbital energies in the tidal debris has a typical form which can be described quite accurately by a simple function. Based on this we develop a method to predict the energy distribution which allows us to evaluate the significance and the implications of high velocity stars in satellite tidal debris. Generally tidal ...

  9. Clifford Fibrations and Possible Kinematics

    Directory of Open Access Journals (Sweden)

    Alan S. McRae

    2009-07-01

    Full Text Available Following Herranz and Santander [Herranz F.J., Santander M., Mem. Real Acad. Cienc. Exact. Fis. Natur. Madrid 32 (1998, 59-84, physics/9702030] we will construct homogeneous spaces based on possible kinematical algebras and groups [Bacry H., Levy-Leblond J.-M., J. Math. Phys. 9 (1967, 1605-1614] and their contractions for 2-dimensional spacetimes. Our construction is different in that it is based on a generalized Clifford fibration: Following Penrose [Penrose R., Alfred A. Knopf, Inc., New York, 2005] we will call our fibration a Clifford fibration and not a Hopf fibration, as our fibration is a geometrical construction. The simple algebraic properties of the fibration describe the geometrical properties of the kinematical algebras and groups as well as the spacetimes that are derived from them. We develop an algebraic framework that handles all possible kinematic algebras save one, the static algebra.

  10. Clifford Fibrations and Possible Kinematics

    Science.gov (United States)

    McRae, Alan S.

    2009-07-01

    Following Herranz and Santander [Herranz F.J., Santander M., Mem. Real Acad. Cienc. Exact. Fis. Natur. Madrid 32 (1998), 59-84, physics/9702030] we will construct homogeneous spaces based on possible kinematical algebras and groups [Bacry H., Levy-Leblond J.-M., J. Math. Phys. 9 (1967), 1605-1614] and their contractions for 2-dimensional spacetimes. Our construction is different in that it is based on a generalized Clifford fibration: Following Penrose [Penrose R., Alfred A. Knopf, Inc., New York, 2005] we will call our fibration a Clifford fibration and not a Hopf fibration, as our fibration is a geometrical construction. The simple algebraic properties of the fibration describe the geometrical properties of the kinematical algebras and groups as well as the spacetimes that are derived from them. We develop an algebraic framework that handles all possible kinematic algebras save one, the static algebra.

  11. Discovery of a brown dwarf companion to the A3V star β Circini

    Science.gov (United States)

    Smith, L. C.; Lucas, P. W.; Contreras Peña, C.; Kurtev, R.; Marocco, F.; Jones, H. R. A.; Beamin, J. C.; Napiwotzki, R.; Borissova, J.; Burningham, B.; Faherty, J.; Pinfield, D. J.; Gromadzki, M.; Ivanov, V. D.; Minniti, D.; Stimson, W.; Villanueva, V.

    2015-12-01

    We report the discovery of an L dwarf companion to the A3V star β Circini. VVV J151721.49-585131.5, or β Cir B, was identified in a proper motion and parallax catalogue of the VISTA Variables in the Vía Láctea survey as having near-infrared luminosity and colour indicative of an early L dwarf, and a proper motion and parallax consistent with that of β Cir. The projected separation of ˜3.6 arcmin corresponds to 6656 au, which is unusually wide. The most recent published estimate of the age of the primary combined with our own estimate based on newer isochrones yields an age of 370-500 Myr. The system therefore serves as a useful benchmark at an age greater than that of the Pleiades brown dwarfs and most other young L dwarf benchmarks. We have obtained a medium resolution echelle spectrum of the companion which indicates a spectral type of L1.0 ± 0.5 and lacks the typical signatures of low-surface gravity seen in younger brown dwarfs. This suggests that signs of low-surface gravity disappear from the spectra of early L dwarfs by an age of ˜370-500 Myr, as expected from theoretical isochrones. The mass of β Cir B is estimated from the BHAC15 isochrones as 0.056 ± 0.007 M⊙.

  12. Antlia B: A faint dwarf galaxy member of the NGC 3109 association

    CERN Document Server

    Sand, D J; Crnojević, D; Hargis, J R; Willman, B; Strader, J; Grillmair, C J

    2015-01-01

    We report the discovery of Antlia B, a faint dwarf galaxy at a projected distance of $\\sim$72 kpc from NGC 3109 ($M_{V}$$\\sim$$-$15 mag), the primary galaxy of the NGC 3109 dwarf association at the edge of the Local Group. The tip of the red giant branch distance to Antlia B is $D$=1.29$\\pm$0.10 Mpc, which is consistent with the distance to NGC 3109. A qualitative analysis indicates the new dwarf's stellar population has both an old, metal poor red giant branch ($\\gtrsim$10 Gyr, [Fe/H]$\\sim$$-$2), and a younger blue population with an age of $\\sim$200-400 Myr, analogous to the original Antlia dwarf, another likely satellite of NGC 3109. Antlia B has \\ion{H}{1} gas at a velocity of $v_{helio,HI}$=376 km s$^{-1}$, confirming the association with NGC 3109 ($v_{helio}$=403 km s$^{-1}$). The HI gas mass (M$_{HI}$=2.8$\\pm$0.2$\\times$10$^{5}$ M$_{\\odot}$), stellar luminosity ($M_{V}$=$-$9.7$\\pm$0.6 mag) and half light radius ($r_{h}$=273$\\pm$29 pc) are all consistent with the properties of dwarf irregular and dwarf ...

  13. Latest Advances in Robot Kinematics

    CERN Document Server

    Husty, Manfred

    2012-01-01

    This book is  of interest to researchers inquiring about modern topics and methods in the kinematics, control and design of robotic manipulators. It considers the full range of robotic systems, including serial, parallel and cable driven manipulators, both planar and spatial. The systems range from being less than fully mobile to kinematically redundant to overconstrained. In addition to recognized areas, this book also presents recent advances in emerging areas such as the design and control of humanoids and humanoid subsystems, and the analysis, modeling and simulation of human body motions, as well as the mobility analysis of protein molecules and the development of machines which incorporate man.

  14. 2MASS J035523.37+113343.7: A YOUNG, DUSTY, NEARBY, ISOLATED BROWN DWARF RESEMBLING A GIANT EXOPLANET

    Energy Technology Data Exchange (ETDEWEB)

    Faherty, Jacqueline K. [Department of Astronomy, Universidad de Chile Cerro Calan, Las Condes (Chile); Rice, Emily L.; Cruz, Kelle L.; Nunez, Alejandro [Department of Astrophysics , American Museum of Natural History, Central Park West at 79th Street, New York, NY 10034 (United States); Mamajek, Eric E., E-mail: jfaherty17@gmail.com, E-mail: jfaherty@amnh.org [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile)

    2013-01-01

    We present parallax and proper motion measurements, near-infrared spectra, and Wide-field Infrared Survey Explorer photometry for the low surface gravity L5{gamma} dwarf 2MASS J035523.37+113343.7 (2M0355). We use these data to evaluate photometric, spectral, and kinematic signatures of youth as 2M0355 is the reddest isolated L dwarf yet classified. We confirm its low-gravity spectral morphology and find a strong resemblance to the sharp triangular shaped H-band spectrum of the {approx}10 Myr planetary-mass object 2M1207b. We find that 2M0355 is underluminous compared to a normal field L5 dwarf in the optical and Mauna Kea Observatory J, H, and K bands and transitions to being overluminous from 3 to 12 {mu}m, indicating that enhanced photospheric dust shifts flux to longer wavelengths for young, low-gravity objects, creating a red spectral energy distribution. Investigating the near-infrared color-magnitude diagram for brown dwarfs confirms that 2M0355 is redder and underluminous compared to the known brown dwarf population, similar to the peculiarities of directly imaged exoplanets 2M1207b and HR8799bcd. We calculate UVW space velocities and find that the motion of 2M0355 is consistent with young disk objects (<2-3 Gyr) and it shows a high likelihood of membership in the AB Doradus association.

  15. a Faint and Lonely Brown Dwarf in the Solar Vicinity

    Science.gov (United States)

    1997-04-01

    Discovery of KELU-1 Promises New Insights into Strange Objects Brown Dwarfs are star-like objects which are too small to become real stars, yet too large to be real planets. Their mass is too small to ignite those nuclear processes which are responsible for the large energies and high temperatures of stars, but it is much larger than that of the planets we know in our solar system. Until now, very few Brown Dwarfs have been securely identified as such. Two are members of double-star systems, and a few more are located deep within the Pleiades star cluster. Now, however, Maria Teresa Ruiz of the Astronomy Department at Universidad de Chile (Santiago de Chile), using telescopes at the ESO La Silla observatory, has just discovered one that is all alone and apparently quite near to us. Contrary to the others which are influenced by other objects in their immediate surroundings, this new Brown Dwarf is unaffected and will thus be a perfect object for further investigations that may finally allow us to better understand these very interesting celestial bodies. It has been suggested that Brown Dwarfs may constitute a substantial part of the unseen dark matter in our Galaxy. This discovery may therefore also have important implications for this highly relevant research area. Searching for nearby faint stars The story of this discovery goes back to 1987 when Maria Teresa Ruiz decided to embark upon a long-term search (known as the Calan-ESO proper-motion survey ) for another type of unusual object, the so-called White Dwarfs , i.e. highly evolved, small and rather faint stars. Although they have masses similar to that of the Sun, such stars are no larger than the Earth and are therefore extremely compact. They are particularly interesting, because they most probably represent the future end point of evolution of our Sun, some billions of years from now. For this project, the Chilean astronomer obtained large-field photographic exposures with the 1-m ESO Schmidt telescope at

  16. A brown dwarf orbiting an M-dwarf

    DEFF Research Database (Denmark)

    Bachelet, E.; Fouqué, P.; Albrow, M.D.

    2012-01-01

    -Collaboration. Alerted as a high-magnification event, it was sensitive to planets. Suspected anomalies in the light curve were not confirmed by a real-time model, but further analysis revealed small deviations from a single lens extended source fit. Methods. Thanks to observations by all the collaborations, this event...... gives two local minima, which correspond to the theoretical degeneracy s ≡ s-1. We find that the lens is composed of a brown dwarf secondary of mass MS = 0.05 M⊙ orbiting a primary M-star of mass MP = 0.18 M⊙. We also reveal a new mass-ratio degeneracy for the central caustics of close binaries...

  17. Chemical composition of stars in kinematical substructures of the galactic disk

    Directory of Open Access Journals (Sweden)

    Gorbaneva T.I.

    2012-02-01

    Full Text Available The Y, Zr, La, Ce, Nd , Sm and Eu abundances were found in LTE approach, and the abundance of Ba was computed in NLTE approximation for 280 FGK dwarfs in the region of metallicity of − 1<[Fe]< + 0.3. The selection of stars belonging to thin and thick disks and the stream Hercules was made on kinematic criteria. The analysis of enrichment of the different substructures of the Galaxy with α-element (Mg, Si, the iron peak (Ni and neutron-capture elements was carried out.

  18. Top quark mass and kinematics

    Energy Technology Data Exchange (ETDEWEB)

    Barberis, Emanuela; /Northeastern U.

    2006-05-01

    A summary of the results on the measurement of the Top Quark mass and the study of the kinematics of the t{bar t} system at the Tevatron collider is presented here. Results from both the CDF and D0 collaborations are reported.

  19. Analyzing the Formation of Ultra-compact Dwarfs through Stellar Populations

    Science.gov (United States)

    Seshadri, Anish; Wang, Carolyn; Romanowsky, Aaron J.; Martin-navarro, Ignacio

    2017-01-01

    Since their discovery in 1999, ultra-compact dwarfs (UCDs) have been the subjects of intense study. Their small size, yet tremendous mass, brings into question their place among celestial objects. Are they galaxies or globular clusters? The answer to this question could come from analyzing how they formed. Thus, the goal of this project is to test one of the theories for the formation of UCDs, the theory of tidal stripping.This project approaches the issue by looking at dwarf galaxies currently in the process of stripping to understand formation history. Over twenty such dwarf galaxies were identified and their stellar populations analyzed. Using modeling techniques on spectroscopic and photometric data, the age, metallicity, and color of each object was identified. By objectively categorizing each object into a stage of evolution in the process of tidal stripping, a virtual timeline was built for the formation of UCDs. Data for each object were plotted vs. stage of formation, with pristine dwarfs and UCDs signifying the endpoints. Trends in the data revealed a natural progression over all stages of evolution, showing that tidally stripped dwarfs likely represent an intermediate stage in the formation of UCDs.This research was supported by NSF Grant AST-1515084. Most of this work was carried out by high school students working under the auspices of the Science Internship Program at UC Santa Cruz.

  20. AR Sco: A Precessing White Dwarf Synchronar?

    Science.gov (United States)

    Katz, J. I.

    2017-02-01

    The emission of the white dwarf–M dwarf binary AR Sco is driven by the rapid synchronization of its white dwarf, rather than by accretion. Synchronization requires a magnetic field ∼100 Gauss at the M dwarf and ∼ {10}8 Gauss at the white dwarf, larger than the fields of most intermediate polars but within the range of fields of known magnetic white dwarfs. The spindown power is dissipated in the atmosphere of the M dwarf, within the near zone of the rotating white dwarf’s field, by magnetic reconnection, accelerating particles that produce the observed synchrotron radiation. The displacement of the optical maximum from conjunction may be explained either by dissipation in a bow wave as the white dwarf’s magnetic field sweeps past the M dwarf or by a misaligned white dwarf rotation axis and oblique magnetic moment. In the latter case the rotation axis precesses with a period of decades, predicting a drift in the orbital phase of the optical maximum. Binaries whose emission is powered by synchronization may be termed synchronars, in analogy to magnetars.

  1. Stars at Low Metallicity in Dwarf Galaxies

    NARCIS (Netherlands)

    Tolstoy, Eline; Battaglia, Giuseppina; Cole, Andrew; Hunt, LK; Madden, S; Schneider, R

    2008-01-01

    Dwarf galaxies offer an opportunity to understand the properties of low metallicity star formation both today and at the earliest times at the, epoch of the formation of the first stars. Here we concentrate on two galaxies in the Local Group: the dwarf irregular galaxy Leo A, which has been the rece

  2. Radial Velocity Variability of Field Brown Dwarfs

    CERN Document Server

    Prato, L; Rice, E L; McLean, I S; Kirkpatrick, J D; Burgasser, A J; Kim, S S

    2015-01-01

    We present paper six of the NIRSPEC Brown Dwarf Spectroscopic Survey, an analysis of multi-epoch, high-resolution (R~20,000) spectra of 25 field dwarf systems (3 late-type M dwarfs, 16 L dwarfs, and 6 T dwarfs) taken with the NIRSPEC infrared spectrograph at the W. M. Keck Observatory. With a radial velocity precision of ~2 km/s, we are sensitive to brown dwarf companions in orbits with periods of a few years or less given a mass ratio of 0.5 or greater. We do not detect any spectroscopic binary brown dwarfs in the sample. Given our target properties, and the frequency and cadence of observations, we use a Monte Carlo simulation to determine the detection probability of our sample. Even with a null detection result, our 1 sigma upper limit for very low mass binary frequency is 18%. Our targets included 7 known, wide brown dwarf binary systems. No significant radial velocity variability was measured in our multi-epoch observations of these systems, even for those pairs for which our data spanned a significant ...

  3. Metals and ionizing photons from dwarf galaxies

    NARCIS (Netherlands)

    Salvadori, S.; Tolstoy, E.; Ferrara, A.; Zaroubi, S.

    2014-01-01

    We estimate the potential contribution of M <10(9)M(circle dot) dwarf galaxies to the reionization and early metal enrichment of the Milky Way environment, or circum-Galactic medium. Our approach is to use the observed properties of ancient stars ()under tilde>12 Gyr old) measured in nearby dwarf ga

  4. Magnetic White Dwarfs with Heavy Elements

    CERN Document Server

    Hardy, François; Jordan, Stefan

    2016-01-01

    Using our newly developed model atmosphere code appropriate for magnetic white dwarfs with metal lines in the Paschen-Back regime, we study various magnetic white dwarfs and explore the effects of various parameters such as the field geometry and the convective efficiency

  5. Microlensing Binaries with Candidate Brown Dwarf Companions

    DEFF Research Database (Denmark)

    Shin, I.-G; Han, C.; Gould, A.;

    2012-01-01

    Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation histories. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing ...

  6. Equilibrium figures of dwarf planets

    Science.gov (United States)

    Rambaux, Nicolas; Chambat, Frederic; Castillo-Rogez, Julie; Baguet, Daniel

    2016-10-01

    Dwarf planets including transneptunian objects (TNO) and Ceres are >500 km large and display a spheroidal shape. These protoplanets are left over from the formation of the solar System about 4.6 billion years ago and their study could improve our knowledge of the early solar system. They could be formed in-situ or migrated to their current positions as a consequence of large-scale solar system dynamical evolution. Quantifying their internal composition would bring constraints on their accretion environment and migration history. That information may be inferred from studying their global shapes from stellar occultations or thermal infrared imaging. Here we model the equilibrium shapes of isolated dwarf planets under the assumption of hydrostatic equilibrium that forms the basis for interpreting shape data in terms of interior structure. Deviations from hydrostaticity can shed light on the thermal and geophysical history of the bodies. The dwarf planets are generally fast rotators spinning in few hours, so their shape modeling requires numerically integration with Clairaut's equations of rotational equilibrium expanded up to third order in a small parameter m, the geodetic parameter, to reach an accuracy better than a few kilometers depending on the spin velocity and mean density. We also show that the difference between a 500-km radius homogeneous model described by a MacLaurin ellipsoid and a stratified model assuming silicate and ice layers can reach several kilometers in the long and short axes, which could be measurable. This type of modeling will be instrumental in assessing hydrostaticity and thus detecting large non-hydrostatic contributions in the observed shapes.

  7. A white dwarf with an oxygen atmosphere

    Science.gov (United States)

    Kepler, S. O.; Koester, Detlev; Ourique, Gustavo

    2016-04-01

    Stars born with masses below around 10 solar masses end their lives as white dwarf stars. Their atmospheres are dominated by the lightest elements because gravitational diffusion brings the lightest element to the surface. We report the discovery of a white dwarf with an atmosphere completely dominated by oxygen, SDSS J124043.01+671034.68. After oxygen, the next most abundant elements in its atmosphere are neon and magnesium, but these are lower by a factor of ≥25 by number. The fact that no hydrogen or helium are observed is surprising. Oxygen, neon, and magnesium are the products of carbon burning, which occurs in stars at the high-mass end of pre-white dwarf formation. This star, a possible oxygen-neon white dwarf, will provide a rare observational test of the evolutionary paths toward white dwarfs.

  8. Disks, accretion and outflows of brown dwarfs

    CERN Document Server

    Joergens, V; Liu, Y; Pascucci, I; Whelan, E; Alcala, J; Biazzo, K; Costigan, G; Gully-Santiago, M; Henning, Th; Natta, A; Rigliaco, E; Rodriguez-Ledesma, V; Sicilia-Aguilar, A; Tottle, J; Wolf, S

    2012-01-01

    Characterization of the properties of young brown dwarfs are important to constraining the formation of objects at the extreme low-mass end of the IMF. While young brown dwarfs share many properties with solar-mass T Tauri stars, differences may be used as tests of how the physics of accretion/outflow and disk chemistry/dissipation depend on the mass of the central object. This article summarizes the presentations and discussions during the splinter session on 'Disks, accretion and outflows of brown dwarfs' held at the CoolStars17 conference in Barcelona in June 2012. Recent results in the field of brown dwarf disks and outflows include the determination of brown dwarf disk masses and geometries based on Herschel far-IR photometry (70-160 um), accretion properties based on X-Shooter spectra, and new outflow detections in the very low-mass regime.

  9. The Brown Dwarf-Exoplanet Connection

    CERN Document Server

    Burgasser, Adam J

    2009-01-01

    Brown dwarfs are commonly regarded as easily-observed templates for exoplanet studies, with comparable masses, physical sizes and atmospheric properties. There is indeed considerable overlap in the photospheric temperatures of the coldest brown dwarfs (spectral classes L and T) and the hottest exoplanets. However, the properties and processes associated with brown dwarf and exoplanet atmospheres can differ significantly in detail; photospheric gas pressures, elemental abundance variations, processes associated with external driving sources, and evolutionary effects are all pertinent examples. In this contribution, I review some of the basic theoretical and empirical properties of the currently known population of brown dwarfs, and detail the similarities and differences between their visible atmospheres and those of extrasolar planets. I conclude with some specific results from brown dwarf studies that may prove relevant in future exoplanet observations.

  10. Double White Dwarf Merger Rates

    Science.gov (United States)

    Toonen, Silvia; Nelemans, Gijs; Portegies Zwart, Simon

    2013-01-01

    Type Ia supernovae (SNe Ia) are very successfully used as standard candles on cosmological distance scales, but so far the nature of the progenitor(s) is unclear. A possible scenario for SNe Ia are merging carbon/oxygen white dwarfs with a combined mass exceeding the Chandrasekhar mass. We determine the theoretical rates and delay time distribution of these mergers for two different common envelope prescriptions and metallicities. The shape of the delay time distributions is rather insensitive to the assumptions. The normalization is a factor ~3-13 too low compared to observations.

  11. Our Robertson-Walker Universe: Kinematics vs. Dynamics

    CERN Document Server

    Bludman, Sidney

    2007-01-01

    This phenomenological review stresses the distinction between kinematics, the description of the recently inflationary universe (cosmography), and dynamics, the mechanism driving this accelerating expansion. Because the homogeneous expansion history H(z) of the universe measures only kinematic variables, it cannot fix the underlying dynamics: cosmographic measurements of the homogeneous universe, are consistent with both a static finely-tuned cosmological constant and a dynamic 'dark energy', which itself may be material Dark Energy or modified gravity (Dark Gravity). Resolving the dynamics of either kind of `dark energy', will require complementing the homogeneous expansion observations with observations of the growth of cosmological fluctuations. Projected observations potentially distinguish static from dynamic `dark energy', but distinguishing dynamic Dark Energy from Dark Gravity will require a weak lensing shear survey more ambitious than any now projected. Low-curvature modifications of Einstein gravit...

  12. H I observations of two new dwarf galaxies: Pisces A and B with the SKA Pathfinder KAT-7

    Science.gov (United States)

    Carignan, C.; Libert, Y.; Lucero, D. M.; Randriamampandry, T. H.; Jarrett, T. H.; Oosterloo, T. A.; Tollerud, E. J.

    2016-03-01

    Context. Pisces A and Pisces B are the only two galaxies found via optical imaging and spectroscopy out of 22 Hi clouds identified in the GALFAHI survey as dwarf galaxy candidates. Aims: We derive the Hi content and kinematics of Pisces A and B. Methods: Our aperture synthesis Hi observations used the seven-dish Karoo Array Telescope (KAT-7), which is a pathfinder instrument for MeerKAT, the South African precursor to the mid-frequency Square Kilometre Array (SKA-MID). Results: The low rotation velocities of ~5 km s-1 and ~10 km s-1 in Pisces A and B, respectively, and their Hi content show that they are really dwarf irregular galaxies (dIrr). Despite that small rotation component, it is more the random motions ~9-11 km s-1 that provide most of the gravitational support, especially in the outer parts. The study of their kinematics, especially the strong gradients of random motions, suggest that those two dwarf galaxies are not yet in equilibrium. Conclusions: These Hi- rich galaxies may be indicative of a large population of dwarfs at the limit of detectability. However, such gas-rich dwarf galaxies will most likely never be within the virial radius of MW-type galaxies and become subhalo candidates. Systems such as Pisces A and B are more likely to be found at a few Mpc s from MW-type galaxies. The final FITS cube is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/587/L3

  13. Age distributions of Greenlandic dwarf shrubs support concept of negligible actuarial senescence

    DEFF Research Database (Denmark)

    Dahlgren, Johan; Rizzi, Silvia; Schweingruber, Fritz

    2016-01-01

    Many plants and sessile animals may not show actuarial senescence, the increase in mortality with age predicted to be ubiquitous by classic evolutionary theories of aging. Age-structured demographic information is, however, limited for most organisms. We assessed the age distributions of nine dwarf...... to be an important variable for making population projections and determining extinction risks....

  14. The Solar Neighborhood. XXI. Parallax Results from the CTIOPI 0.9m Program: 20 New Members of the 25 Parsec White Dwarf Sample

    CERN Document Server

    Subasavage, John P; Henry, Todd J; Bergeron, P; Dufour, P; Ianna, Philip A; Costa, Edgardo; Mendez, Rene A

    2009-01-01

    We present accurate trigonometric parallaxes for 20 new members of the 25 pc white dwarf sample as part of the DENSE project (Discovery and Evalution of Nearby Stellar Embers, http://www.DenseProject.com). Previously, there were a total of 112 white dwarf systems with trigonometric parallaxes placing them within 25 pc and of these, 99 have trigonometric parallaxes known to better than 10%. Thus, the 20 new members presented in this work represent a 20% increase in the number of white dwarfs accurately known to be within 25 pc. In addition, we present updated parallaxes for seven known white dwarfs within 10 pc that have been observed as part of the ASPENS initiative (Astrometric Search for Planets Encircling Nearby Stars) to monitor nearby southern red and white dwarfs for astrometric perturbations from unseen companions. Including a few white dwarf companions and white dwarfs beyond 25 pc, we present a total of 33 trigonometric parallaxes. We perform atmospheric modeling for white dwarfs to determine physica...

  15. Formation of ultra-compact blue dwarf galaxies and their evolution into nucleated dwarfs

    CERN Document Server

    Bekki, Kenji

    2015-01-01

    We propose that there is an evolutionary link between ultra-compact blue dwarf galaxies (UCBDs) with active star formation and nucleated dwarfs based on the results of numerical simulations of dwarf-dwarf merging. We consider the observational fact that low-mass dwarfs can be very gas-rich, and thereby investigate the dynamical and chemical evolution of very gas-rich, dissipative dwarf-dwarf mergers. We find that the remnants of dwarf-dwarf mergers can be dominated by new stellar populations formed from the triggered starbursts and consequently can have blue colors and higher metallicities (Z~[0.2-1]Z_sun). We also find that the remnants of these mergers can have rather high mass-densities (10^4 M_sun pc^-3) within the central 10 pc and small half-light radii (40-100 pc). The radial stellar structures of some merger remnants are similar to those of nucleated dwarfs. Star formation can continue in nuclear gas disks (R<100 pc) surrounding stellar galactic nuclei (SGNs) so that the SGNs can finally have multi...

  16. Characterizing dw1335-29, a recently discovered dwarf satellite of M83

    Science.gov (United States)

    Carrillo, Andreia; Bell, Eric F.; Bailin, Jeremy; Monachesi, Antonela; de Jong, Roelof S.; Harmsen, B2enjamin; Slater, Colin T.

    2017-03-01

    The number, distribution and properties of dwarf satellites are crucial probes of the physics of galaxy formation at low masses and the response of satellite galaxies to the tidal and gas dynamical effects of their more massive parent. To make progress, it is necessary to augment and solidify the census of dwarf satellites of galaxies outside the Local Group. Müller et al. presented 16 dwarf galaxy candidates near M83, but lacking reliable distances, it is unclear which candidates are M83 satellites. Using red-giant-branch stars from the HST/GHOSTS survey in conjunction with ground-based images from VLT/VIMOS, we confirm that one of the candidates, dw1335-29 - with a projected distance of 26 kpc from M83 and a distance modulus of (m-M)_0 = 28.5^{+0.3}_{-0.1} - is a satellite of M83. We estimate an absolute magnitude MV = -10.1 ± 0.4, an ellipticity of 0.40^{+0.14}_{-0.22}, a half-light radius of 656^{+121}_{-170} pc and [Fe/H] = -1.3^{+0.3}_{-0.4}. Owing to dw1335-29's somewhat irregular shape and possible young stars, we classify this galaxy as a dwarf irregular or transition dwarf. This is curious, as with a projected distance of 26 kpc from M83, dw1335-29 is expected to lack recent star formation. Further study of M83's dwarf population will reveal if star formation in its satellites is commonplace (suggesting a lack of a hot gas envelope for M83 that would quench star formation) or rare (suggesting that dw1335-29 has a larger M83-centric distance, and is fortuitously projected to small radii).

  17. Exploring MaNGA's kinematic maps

    Science.gov (United States)

    Weijmans, Anne-Marie; MaNGA Team

    2016-01-01

    Different galaxy formation processes leave different imprints on the gas and stellar kinematic patterns for a galaxy. With MaNGA, we now have after one year of observations an unprecedented sample of 1400 nearby galaxies for which we can study gas and stellar kinematics in much detail, based on integral-field spectroscopy. We are measuring kinematic quantities such as LambdaR (angular momentum) and their (possible) correlations with other galaxy properties such as mass, morphology and environment. By quantifying the kinematic (sub)structures in velocity and dispersion maps, we will construct a kinematic galaxy classification that can be linked to their formation processes.

  18. Throwing Icebergs at White Dwarfs

    Science.gov (United States)

    Stephan, Alexander P.; Naoz, Smadar; Zuckerman, B.

    2017-08-01

    White dwarfs (WDs) have atmospheres that are expected to consist nearly entirely of hydrogen and helium, since heavier elements will sink out of sight on short timescales. However, observations have revealed atmospheric pollution by heavier elements in about a quarter to a half of all WDs. While most of the pollution can be accounted for with asteroidal or dwarf planetary material, recent observations indicate that larger planetary bodies, as well as icy and volatile material from Kuiper belt analog objects, are also viable sources of pollution. The commonly accepted pollution mechanisms, namely scattering interactions between planetary bodies orbiting the WDs, can hardly account for pollution by objects with large masses or long-period orbits. Here we report on a mechanism that naturally leads to the emergence of massive body and icy and volatile material pollution. This mechanism occurs in wide binary stellar systems, where the mass loss of the planets’ host stars during post main sequence stellar evolution can trigger the Eccentric Kozai-Lidov mechanism. This mechanism leads to large eccentricity excitations, which can bring massive and long-period objects close enough to the WDs to be accreted. We find that this mechanism readily explains and is consistent with observations.

  19. The Complex Kinematics of the Neutral Hydrogen Associated with I Zw 18

    CERN Document Server

    Van Zee, L; Haynes, M P; Salzer, J J

    1997-01-01

    We present the results of high velocity and high spatial resolution HI synthesis observations of the blue compact dwarf galaxy IZw18 to investigate the link between its unique evolutionary history and the neutral gas distribution and kinematics. The HI distribution is extensive, with diffuse neutral gas extending to the northwest and south of the main component. This diffuse gas may be a remnant of the nascent HI cloud. The kinematics of the IZw18 system are complex, with 4 components identified: HI-A, HI-C, HI-I, and HI-SX. The gas associated with the main body, HI-A, has a steep velocity gradient; although our analysis is hindered by poor spatial resolution relative to the extent of the system, the main body appears to be undergoing solid body rotation. The optical condensation to the northwest of IZw18 is embedded in the common HI envelope, and is found to be kinematically separate from the main body (HI-C). The interbody gas, HI-I, connects HI-A and HI-C. Finally, a large diffuse, kinematically distinct, ...

  20. A New M Dwarf Debris Disk Candidate in a Young Moving Group Discovered with Disk Detective

    CERN Document Server

    Silverberg, Steven M; Wisniewski, John P; Gagne, Jonathan; Bans, Alissa S; Bhattacharjee, Shambo; Currie, Thayne R; Debes, John R; Biggs, Joseph R; Bosch, Milton; Doll, Katharina; Durantini-Luca, Hugo A; Enachioaie, Alexandru; Griffith,, Philip; Hyogo, Michiharu; Piniero, Fernanda

    2016-01-01

    We used the Disk Detective citizen science project and the BANYAN II Bayesian analysis tool to identify a new candidate member of a nearby young association with infrared excess. WISE J080822.18-644357.3, an M5.5-type debris disk system with significant excess at both 12 and 22 $\\mu$m, is a likely member ($\\sim 90\\%$ BANYAN II probability) of the $\\sim 45$ Myr-old Carina association. Since this would be the oldest M dwarf debris disk detected in a moving group, this discovery could be an important constraint on our understanding of M dwarf debris disk evolution.

  1. [Study of the central representation of the posterior nerve of the lateral line in dwarf sheatfish].

    Science.gov (United States)

    Volkova, N K; Andrianov, Iu N

    1977-05-01

    Applying the axon-terminal degeneration method, the representation of the lateral line posterior nerve in acustico-lateral area of the dwarf sheatfish medulla oblongata was studied. The connections of the lateral line posterior nerve were demonstrated to be topically organized within the medial nucleus of the acustico-lateral area, however, within the limits of the nucleus the projections were not evenly distributed. The greatest degree of localization of the degenerated terminals was revealed in the dorsolateral area of the medial nucleus on the ipsilateral side, where previously, under adequate stimulation of the organs on the lateral line of the dwarf sheatfish, the greatest amount of responses was registered.

  2. A New M Dwarf Debris Disk Candidate in a Young Moving Group Discovered with Disk Detective

    Science.gov (United States)

    Silverberg, Steven M.; Kuchner, Marc J.; Wisniewski, John P.; Gagne, Jonathan; Bans, Alissa S.; Bhattacharjee, Shambo; Currie, Thayne R.; Debes, John R.; Biggs, Joseph R; Bosch, Milton

    2016-01-01

    We used the Disk Detective citizen science project and the BANYAN II Bayesian analysis tool to identify a new candidate member of a nearby young association with infrared excess. WISE J080822.18-644357.3, an M5.5-type debris disk system with significant excess at both 12 and 22 microns, is a likely member (approx.90% BANYAN II probability) of the approx.45 Myr old Carina association. Since this would be the oldest M dwarf debris disk detected in a moving group, this discovery could be an important constraint on our understanding of M dwarf debris disk evolution.

  3. Measurement of reed valve kinematics

    Directory of Open Access Journals (Sweden)

    Fenkl Michael

    2016-01-01

    Full Text Available The measurement of key kinematic parameters of a reed valve movement is necessary for the further development of the reed valve system. These parameters are dependent on the geometry and material properties of the valve. As they directly affect the quantity of air flowing around the valve, a simple and easy to implement measurement of various valve configuration based on the air flow has been devised and is described in this paper, along with its technical parameters and drawbacks when evaluating reed valves used in reciprocating air compressors. Results are presented for a specimen of a compressor under examination. All kinematic parameters, and timing of the opening and closing of the valve, obtained from the measurement are presented and discussed.

  4. Kinematic Fitting of Detached Vertices

    Energy Technology Data Exchange (ETDEWEB)

    Mattione, Paul [Rice Univ., Houston, TX (United States)

    2007-05-01

    The eg3 experiment at the Jefferson Lab CLAS detector aims to determine the existence of the $\\Xi_{5}$ pentaquarks and investigate the excited $\\Xi$ states. Specifically, the exotic $\\Xi_{5}^{--}$ pentaquark will be sought by first reconstructing the $\\Xi^{-}$ particle through its weak decays, $\\Xi^{-}\\to\\pi^{-}\\Lambda$ and $\\Lambda\\to\\pi^{-}$. A kinematic fitting routine was developed to reconstruct the detached vertices of these decays, where confidence level cuts on the fits are used to remove background events. Prior to fitting these decays, the exclusive reaction $\\gamma D\\rightarrow pp\\pi^{-}$ was studied in order to correct the track measurements and covariance matrices of the charged particles. The $\\Lambda\\rightarrow p\\pi^{-}$ and $\\Xi^{-}\\to\\pi^{-}\\Lambda$ decays were then investigated to demonstrate that the kinematic fitting routine reconstructs the decaying particles and their detached vertices correctly.

  5. Measurement of reed valve kinematics

    Science.gov (United States)

    Fenkl, Michael; Dvořák, Václav; Vít, Tomáš

    2016-03-01

    The measurement of key kinematic parameters of a reed valve movement is necessary for the further development of the reed valve system. These parameters are dependent on the geometry and material properties of the valve. As they directly affect the quantity of air flowing around the valve, a simple and easy to implement measurement of various valve configuration based on the air flow has been devised and is described in this paper, along with its technical parameters and drawbacks when evaluating reed valves used in reciprocating air compressors. Results are presented for a specimen of a compressor under examination. All kinematic parameters, and timing of the opening and closing of the valve, obtained from the measurement are presented and discussed.

  6. Sex Differences in Tibiocalcaneal Kinematics

    Directory of Open Access Journals (Sweden)

    Sinclair Jonathan

    2014-08-01

    Full Text Available Purpose. Female runners typically suffer more from chronic running injuries than age-matched males, although the exact biome-chanical mechanisms behind the increased susceptibility of female runners are unknown. This study aimed to compare sex differences in tibiocalcaneal kinematics during the stance phase of running. Methods. Twenty male and twenty female participants ran at 4.0 m · s–1. Tibiocalcaneal kinematics were measured using an eight-camera motion analysis system and compared using independent samples t tests. Results. Peak eversion and tibial internal rotation angles were shown to be significantly greater in female runners. Conclusions. based on these observations, it was determined that female runners may be at increased risk from chronic injury development in relation to excessive tibiocalcaneal motions in the coronal and transverse planes.

  7. Cusp-core transformations in dwarf galaxies: observational predictions

    Science.gov (United States)

    Teyssier, Romain; Pontzen, Andrew; Dubois, Yohan; Read, Justin I.

    2013-03-01

    The presence of a dark matter core in the central kiloparsec of many dwarf galaxies has been a long-standing problem in galaxy formation theories based on the standard cold dark matter paradigm. Recent simulations, based on smooth particle hydrodynamics and rather strong feedback recipes, have shown that it was indeed possible to form extended dark matter cores using baryonic processes related to a more realistic treatment of the interstellar medium. Using adaptive mesh refinement, together with a new, stronger supernova feedback scheme that we have recently implemented in the RAMSES code, we show that it is also possible to form a prominent dark matter core within the well-controlled framework of an isolated, initially cuspy, 1010 M⊙ dark matter halo. Although our numerical experiment is idealized, it allows a clean and unambiguous identification of the dark matter core formation process. Our dark matter inner profile is well fitted by a pseudo-isothermal profile with a core radius of 800 pc. The core formation mechanism is consistent with the one proposed by Pontzen & Governato. We highlight two key observational predictions of all simulations that find cusp-core transformations: (i) a bursty star formation history with a peak-to-trough ratio of 5 to 10 and a duty cycle comparable to the local dynamical time and (ii) a stellar distribution that is hot with v/σ ˜ 1. We compare the observational properties of our model galaxy with recent measurements of the isolated dwarf Wolf-Lundmark-Mellote (WLM). We show that the spatial and kinematical distribution of stars and H I gas are in striking agreement with observations, supporting the fundamental role played by stellar feedback in shaping both the stellar and dark matter distribution.

  8. SDSS DR7 White Dwarf Catalog

    CERN Document Server

    Kleinman, S J; Koester, D; Pelisoli, Ingrid; Peçanha, Viviane; Nitta, A; Costa, J E S; Krzesinski, J; Dufour, P; Lachapelle, F -R; Bergeron, P; Yip, Ching-Wa; Harris, Hugh C; Eisenstein, Daniel J; Althaus, L; Córsico, A

    2012-01-01

    We present a new catalog of spectroscopically-confirmed white dwarf stars from the Sloan Digital Sky Survey Data Release 7 spectroscopic catalog. We find 20,407 white dwarf spectra, representing 19,712 stars, and provide atmospheric model fits to 14,120 DA and 1011 DB white dwarf spectra from 12,843 and 923 stars, respectively. These numbers represent a more than factor of two increase in the total number of white dwarf stars from the previous SDSS white dwarf catalog based on DR4 data. Our distribution of subtypes varies from previous catalogs due to our more conservative, manual classifications of each star in our catalog, supplementing our automatic fits. In particular, we find a large number of magnetic white dwarf stars whose small Zeeman splittings mimic increased Stark broadening that would otherwise result in an overestimated log(g) if fit as a non-magnetic white dwarf. We calculate mean DA and DB masses for our clean, non-magnetic sample and find the DB mean mass is statistically larger than that for...

  9. SDSS DR7 WHITE DWARF CATALOG

    Energy Technology Data Exchange (ETDEWEB)

    Kleinman, S. J.; Nitta, A. [Gemini Observatory, 670 North A' ohoku Place, Hilo, HI 96720 (United States); Kepler, S. O.; Pelisoli, Ingrid; Pecanha, Viviane; Costa, J. E. S. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil); Koester, D. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Kiel, D-24098 Kiel (Germany); Krzesinski, J. [Mt. Suhora Observatory, Pedagogical University of Cracow, ul. Podchorazych 2, 30-084 Cracow (Poland); Dufour, P.; Lachapelle, F.-R.; Bergeron, P. [Departement de Physique, Universite de Montreal, C. P. 6128, Succ. Centre-Ville, Montreal, Quebec H3C 3J7 (Canada); Yip, Ching-Wa [Department of Physics and Astronomy, The Johns Hopkins University, 3701 San Martin Drive, Baltimore, MD 21218 (United States); Harris, Hugh C. [United States Naval Observatory, Flagstaff Station, 10391 West Naval Observatory Road, Flagstaff, AZ 86001-8521 (United States); Eisenstein, Daniel J. [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, MS 20, Cambridge, MA 02138 (United States); Althaus, L.; Corsico, A., E-mail: hch@nofs.navy.mil [Facultad de Ciencias Astronomicas y Geofisicas, Paseo del Bosque S/N, (1900) La Plata (Argentina)

    2013-01-15

    We present a new catalog of spectroscopically confirmed white dwarf stars from the Sloan Digital Sky Survey (SDSS) Data Release 7 spectroscopic catalog. We find 20,407 white dwarf spectra, representing 19,712 stars, and provide atmospheric model fits to 14,120 DA and 1011 DB white dwarf spectra from 12,843 and 923 stars, respectively. These numbers represent more than a factor of two increase in the total number of white dwarf stars from the previous SDSS white dwarf catalogs based on DR4 data. Our distribution of subtypes varies from previous catalogs due to our more conservative, manual classifications of each star in our catalog, supplementing our automatic fits. In particular, we find a large number of magnetic white dwarf stars whose small Zeeman splittings mimic increased Stark broadening that would otherwise result in an overestimated log g if fit as a non-magnetic white dwarf. We calculate mean DA and DB masses for our clean, non-magnetic sample and find the DB mean mass is statistically larger than that for the DAs.

  10. White dwarf constraints on a varying $G$

    CERN Document Server

    García-Berro, Enrique; Althaus, Leandro G; Córsico, Alejandro H; Lorén-Aguilar, Pablo; Romero, Alejandra D; Isern, Jordi

    2013-01-01

    A secular variation of $G$ modifies the structure and evolutionary time scales of white dwarfs. Using an state-of-the-art stellar evolutionary code, an up-to-date pulsational code, and a detailed population synthesis code we demonstrate that the effects of a running $G$ are obvious both in the properties of individual white dwarfs, and in those of the white dwarf populations in clusters. Specifically, we show that the white dwarf evolutionary sequences depend on both the value of $\\dot G/G$, and on the value of $G$ when the white dwarf was born. We show as well that the pulsational properties of variable white dwarfs can be used to constrain $\\dot G/G$. Finally, we also show that the ensemble properties of of white dwarfs in clusters can also be used to set upper bounds to $\\dot G/G$. Precisely, the tightest bound --- $\\dot G/G \\sim -1.8 10^{-12}$ yr$^{-1}$ --- is obtained studying the population of the old, metal-rich, well populated, open cluster NGC 6791. Less stringent upper limits can be obtained compari...

  11. The Luminosities of the Coldest Brown Dwarfs

    CERN Document Server

    Tinney, C G; Kirkpatrick, J Davy; Cushing, Mike; Morley, Caroline V; Wright, Edward L

    2014-01-01

    In recent years brown dwarfs have been extended to a new Y-dwarf class with effective temperatures colder than 500K and masses in the range 5-30 Jupiter masses. They fill a crucial gap in observable atmospheric properties between the much colder gas-giant planets of our own Solar System (at around 130K) and both hotter T-type brown dwarfs and the hotter planets that can be imaged orbiting young nearby stars (both with effective temperatures of in the range 1500-1000K). Distance measurements for these objects deliver absolute magnitudes that make critical tests of our understanding of very cool atmospheres. Here we report new distances for nine Y dwarfs and seven very-late T dwarfs. These reveal that Y dwarfs do indeed represent a continuation of the T dwarf sequence to both fainter luminosities and cooler temperatures. They also show that the coolest objects display a large range in absolute magnitude for a given photometric colour. The latest atmospheric models show good agreement with the majority of these ...

  12. Kinematics of the Danakil microplate

    OpenAIRE

    2002-01-01

    A refinement and extrapolation of recent motion estimates for the Danakilmicroplate, based on ancient kinematic indicators in the Afar region, describesthe evolution of a microplate in the continental realm. The Danakil horst is anelevated part of this microplate, exposing Precambrian basement within theAfar depression, site of the Nubia-Somalia-Arabia triple junction. We compareevidence for strike- or oblique-slip faults in data from the Afar depression andsouthern Red Sea to small circles a...

  13. Pythagoras Theorem and Relativistic Kinematics

    Science.gov (United States)

    Mulaj, Zenun; Dhoqina, Polikron

    2010-01-01

    In two inertial frames that move in a particular direction, may be registered a light signal that propagates in an angle with this direction. Applying Pythagoras theorem and principles of STR in both systems, we can derive all relativistic kinematics relations like the relativity of simultaneity of events, of the time interval, of the length of objects, of the velocity of the material point, Lorentz transformations, Doppler effect and stellar aberration.

  14. 2D kinematic signatures of boxy/peanut bulges

    CERN Document Server

    Iannuzzi, Francesca

    2015-01-01

    We study the imprints of boxy/peanut structures on the 2D line-of-sight kinematics of simulated disk galaxies. The models under study belong to a family with varying initial gas fraction and halo triaxiality, plus few other control runs with different structural parameters; the kinematic information was extracted using the Voronoi-binning technique and parametrised up to the fourth order of a Gauss-Hermite series. Building on a previous work for the long-slit case, we investigate the 2D kinematic behaviour in the edge-on projection as a function of the boxy/peanut strength and position angle; we find that for the strongest structures the highest moments show characteristic features away from the midplane in a range of position angles. We also discuss the masking effect of a classical bulge and the ambiguity in discriminating kinematically this spherically-symmetric component from a boxy/peanut bulge seen end-on. Regarding the face-on case, we extend existing results to encompass the effect of a second bucklin...

  15. Kinematic Downsizing at z~2

    CERN Document Server

    Simons, Raymond C; Trump, Jonathan R; Weiner, Benjamin J; Heckman, Timothy M; Barro, Guillermo; Koo, David C; Guo, Yicheng; Pacifici, Camilla; Koekemoer, Anton; Stephens, Andrew W

    2016-01-01

    We present results from a survey of the internal kinematics of 49 star-forming galaxies at z$\\,\\sim\\,$2 in the CANDELS fields with the Keck/MOSFIRE spectrograph (SIGMA, Survey in the near-Infrared of Galaxies with Multiple position Angles). Kinematics (rotation velocity $V_{rot}$ and integrated gas velocity dispersion $\\sigma_g$) are measured from nebular emission lines which trace the hot ionized gas surrounding star-forming regions. We find that by z$\\,\\sim\\,$2, massive star-forming galaxies ($\\log\\,M_*/M_{\\odot}\\gtrsim10.2$) have assembled primitive disks: their kinematics are dominated by rotation, they are consistent with a marginally stable disk model, and they form a Tully-Fisher relation. These massive galaxies have values of $V_{rot}/\\sigma_g$ which are factors of 2-5 lower than local well-ordered galaxies at similar masses. Such results are consistent with findings by other studies. We find that low mass galaxies ($\\log\\,M_*/M_{\\odot}\\lesssim10.2$) at this epoch are still in the early stages of disk...

  16. New Light on Dark Stars Red Dwarfs, Low-Mass Stars, Brown Dwarfs

    CERN Document Server

    Reid, I. Neill

    2005-01-01

    There has been very considerable progress in research into low-mass stars, brown dwarfs and extrasolar planets during the past few years, particularly since the fist edtion of this book was published in 2000. In this new edtion the authors present a comprehensive review of both the astrophysical nature of individual red dwarf and brown dwarf stars and their collective statistical properties as an important Galactic stellar population. Chapters dealing with the observational properies of low-mass dwarfs, the stellar mass function and extrasolar planets have been completely revised. Other chapters have been significantly revised and updated as appropriate, including important new material on observational techniques, stellar acivity, the Galactic halo and field star surveys. The authors detail the many discoveries of new brown dwarfs and extrasolar planets made since publication of the first edition of the book and provide a state-of-the-art review of our current knowledge of very low-mass stars, brown dwarfs a...

  17. The Gobbling Dwarf that Exploded

    Science.gov (United States)

    2007-07-01

    A unique set of observations, obtained with ESO's VLT, has allowed astronomers to find direct evidence for the material that surrounded a star before it exploded as a Type Ia supernova. This strongly supports the scenario in which the explosion occurred in a system where a white dwarf is fed by a red giant. ESO PR Photo 31a/07 ESO PR Photo 31a/07 Evolution of SN 2006X Spectrum Because Type Ia supernovae are extremely luminous and quite similar to one another, these exploding events have been used extensively as cosmological reference beacons to trace the expansion of the Universe. However, despite significant recent progress, the nature of the stars that explode and the physics that governs these powerful explosions have remained very poorly understood. In the most widely accepted models of Type Ia supernovae the pre-explosion white dwarf star orbits another star. Due to the close interaction and the strong attraction produced by the very compact object, the companion star continuously loses mass, 'feeding' the white dwarf. When the mass of the white dwarf exceeds a critical value, it explodes. The team of astronomers studied in great detail SN 2006X, a Type Ia supernova that exploded 70 million light-years away from us, in the splendid spiral Galaxy Messier 100 (see ESO 08/06). Their observations led them to discover the signatures of matter lost by the normal star, some of which is transferred to the white dwarf. The observations were made with the Ultraviolet and Visual Echelle Spectrograph (UVES), mounted at ESO's 8.2-m Very Large Telescope, on four different occasions, over a time span of four months. A fifth observation at a different time was secured with the Keck telescope in Hawaii. The astronomers also made use of radio data obtained with NRAO's Very Large Array as well as images extracted from the NASA/ESA Hubble Space Telescope archive. ESO PR Photo 31b/07 ESO PR Photo 31b/07 SN 2006X, before and after the Type Ia Supernova explosion "No Type Ia

  18. 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.

  19. Young Brown Dwarfs as Giant Exoplanet Analogs

    CERN Document Server

    Faherty, Jacqueline K; Rice, Emily L; Riedel, Adric

    2013-01-01

    Young brown dwarfs and directly-imaged exoplanets have enticingly similar photometric and spectroscopic characteristics, indicating that their cool, low gravity atmospheres should be studied in concert. Similarities between the peculiar shaped H band, near and mid-IR photometry as well as location on color magnitude diagrams provide important clues about how to extract physical properties of planets from current brown dwarf observations. In this proceeding we discuss systems newly assigned to 10-150 Myr nearby moving groups, highlight the diversity of this uniform age-calibrated brown dwarf sample, and reflect on their implication for understanding current and future planetary data.

  20. FORMATION OF ULTRA-COMPACT BLUE DWARF GALAXIES AND THEIR EVOLUTION INTO NUCLEATED DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Bekki, Kenji [ICRAR, M468, The University of Western Australia 35 Stirling Highway, Crawley Western Australia, 6009 (Australia)

    2015-10-10

    We propose that there is an evolutionary link between ultra-compact blue dwarf galaxies (UCBDs) with active star formation and nucleated dwarfs based on the results of numerical simulations of dwarf–dwarf merging. We consider the observational fact that low-mass dwarfs can be very gas-rich, and thereby investigate the dynamical and chemical evolution of very gas-rich, dissipative dwarf–dwarf mergers. We find that the remnants of dwarf–dwarf mergers can be dominated by new stellar populations formed from the triggered starbursts and consequently can have blue colors and higher metallicities (Z ∼ [0.2–1]Z{sub ⊙}). We also find that the remnants of these mergers can have rather high mass densities (10{sup 4} M{sub ⊙} pc{sup −3}) within the central 10 pc and small half-light radii (40−100 pc). The radial stellar structures of some merger remnants are similar to those of nucleated dwarfs. Star formation can continue in nuclear gas disks (R < 100 pc) surrounding stellar galactic nuclei (SGNs) so that the SGNs can finally have multiple stellar populations with different ages and metallicities. These very compact blue remnants can be identified as UCBDs soon after merging and as nucleated dwarfs after the young stars fade. We discuss these results in the context of the origins of metal-rich ultra-compact dwarfs and SGNs.

  1. Evolutionary calculations of carbon dredge-up in helium envelope white dwarfs

    CERN Document Server

    MacDonald, J; José, J; Donald, James Mac; Hernanz, Margarita; José, Jordi; Physics, Department of; Delaware, University of; Catalunya, Institut d'Estudis Espacials de; Unit, CSIC Research; Nexus-201, Edifici; Nuclear, Departament de Fí sica i Enginyeria; Balaguer, Avda. Ví ctor

    1998-01-01

    We investigate the evolution of cooling helium atmosphere white dwarfs using a full evolutionary code, specifically developed for following the effects of element diffusion and gravitational settling on white dwarf cooling. The major difference between this work and previous work is that we use more recent opacity data from the OPAL project. Since, in general, these opacities are higher than those available ten years ago, at a given effective temperature, convection zones go deeper than in models with older opacity data. Thus convective dredge-up of observationally detectable carbon in helium atmosphere white dwarfs can occur for thicker helium layers than found by Pelletier et al (1986). We find that the range of observed C to He ratios in different DQ white dwarfs of similar effective temperature is well explained by a range of initial helium layer mass between $10^{-3}$ and $10^{-2} M_{\\odot}$, in good agreement with stellar evolution theory, assuming a typical white dwarf mass of $0.6 M_{\\odot}$. We also ...

  2. Discovery of a brown dwarf companion to the A3V star \\beta{} Circini

    CERN Document Server

    Smith, L C; Peña, C Contreras; Kurtev, R; Marocco, F; Jones, H R A; Beamin, J C; Napiwotzki, R; Borissova, J; Burningham, B; Faherty, J; Pinfield, D J; Gromadzki, M; Ivanov, V D; Minniti, D; Stimson, W; Villanueva, V

    2015-01-01

    We report the discovery of an L dwarf companion to the A3V star \\beta{} Circini. VVV J151721.49-585131.5, or \\beta{} Cir B, was identified in a proper motion and parallax catalogue of the Vista Variables in the V\\'{i}a L\\'{a}ctea survey as having near infrared luminosity and colour indicative of an early L dwarf, and a proper motion and parallax consistent with that of \\beta{} Cir. The projected separation of $\\sim$3.6' corresponds to $6656$ au, which is unusually wide. The most recent published estimate of the age of the primary combined with our own estimate based on newer isochrones yields an age of $370-500$ Myr. The system therefore serves as a useful benchmark at an age greater than that of the Pleiades brown dwarfs and most other young L dwarf benchmarks. We have obtained a medium resolution echelle spectrum of the companion which indicates a spectral type of L1.0$\\pm$0.5 and lacks the typical signatures of low surface gravity seen in younger brown dwarfs. This suggests that signs of low surface gravit...

  3. Accretion-ejection connection in the young brown dwarf candidate ISO-Cha1 217

    CERN Document Server

    Whelan, E T; Bacciotti, F; Nisini, B; Bonito, R; Antoniucci, S; Stelzer, B; Biazzo, K; D'Elia, V; Ray, T P

    2014-01-01

    As the number of observed brown dwarf outflows is growing it is important to investigate how these outflows compare to the well studied jets from young stellar objects. A key point of comparison is the relationship between outflow and accretion activity and in particular the ratio between the mass outflow and accretion rates ($\\dot{M}_{out}$/$\\dot{M}_{acc}$). The brown dwarf candidate ISO-ChaI 217 was discovered by our group, as part of a spectro-astrometric study of brown dwarfs, to be driving an asymmetric outflow with the blue-shifted lobe having a position angle of $\\sim$ 20$^{\\circ}$. The aim here is to further investigate the properties of ISO-ChaI 217, the morphology and kinematics of its outflow, and to better constrain ($\\dot{M}_{out}$/$\\dot{M}_{acc}$). The outflow is spatially resolved in the $[SII]\\lambda \\lambda 6716,6731$ lines and is detected out to $\\sim$ 1\\farcs6 in the blue-shifted lobe and ~ 1" in the red-shifted lobe. The asymmetry between the two lobes is confirmed although the velocity as...

  4. Discovery of the young L dwarf wise J174102.78-464225.5

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Adam C.; Cushing, Michael C. [Department of Physics and Astronomy, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 (United States); Kirkpatrick, J. Davy; Mace, Gregory N.; Gelino, Christopher R.; Fajardo-Acosta, Sergio [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Faherty, Jacqueline K. [Department of Astronomy, University of Chile, Camino El Observatorio 1515, Casilla 36-D, Santiago (Chile); Sheppard, Scott S., E-mail: Adam.Schneider@Utoledo.edu [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015 (United States)

    2014-02-01

    We report the discovery of the L dwarf WISE J174102.78–464225.5, which was discovered as part of a search for nearby L dwarfs using the Wide-field Infrared Survey Explorer (WISE). The distinct triangular peak of the H-band portion of its near-infrared spectrum and its red near-infrared colors (J – K{sub S} = 2.35 ± 0.08 mag) are indicative of a young age. Via comparison to spectral standards and other red L dwarfs, we estimate a near-infrared spectral type of L7 ± 2 (pec). From a comparison to spectral and low-mass evolutionary models, we determine self-consistent effective temperature, log g, age, and mass values of 1450 ± 100 K, 4.0 ± 0.25 (cm s{sup –2}), 10-100 Myr, and 4-21 M {sub Jup}, respectively. With an estimated distance of 10-30 pc, we explore the possibility that WISE J174102.78–464225.5 belongs to one of the young nearby moving groups via a kinematic analysis and we find potential membership in the β Pictoris or AB Doradus associations. A trigonometric parallax measurement and a precise radial velocity can help to secure its membership in either of these groups.

  5. Theoretical lower limits on sizes of ultra faint dwarf galaxies from dynamical friction

    CERN Document Server

    Hernandez, X

    2016-01-01

    Dwarf spheroidal galaxies are the smallest known stellar systems where under Newtonian interpretations, a significant amount of dark matter is required to explain observed kinematics. In fact, they are in this sense the most heavily dark matter dominated objects known. That, plus the increasingly small sizes of the newly discovered ultra faint dwarfs, puts these systems in the regime where dynamical friction on individual stars starts to become relevant. We calculate the dynamical friction timescales for pressure supported isotropic spherical dark matter dominated stellar systems, yielding $\\tau_{DF} =0.93 (r_{h}/10 pc)^{2} (\\sigma/ kms^{-1}) Gyr$. For a stellar velocity dispersion value of $3 km/s$, as typical for the smallest of the recently detected ultra faint dwarf spheroidals, dynamical friction timescales becomes smaller than the $10 Gyr$ typical of the stellar ages for these systems, for half-light radii $r_{h}<19 pc$. Thus, this becomes a theoretical lower limit below which dark matter dominated s...

  6. Discovery of the Young L Dwarf WISE J1741102.78-464225.5

    CERN Document Server

    Schneider, Adam C; Kirkpatrick, J Davy; Mace, Gregory N; Gelino, Christopher R; Faherty, Jacqueline K; Fajardo-Acosta, Sergio; Sheppard, Scott S

    2013-01-01

    We report the discovery of the L dwarf WISE J174102.78$-$464225.5, that was discovered as part of a search for nearby L dwarfs using the Wide-field Infrared Survey Explorer (WISE). The distinct triangular peak of the H-band portion of its near-infrared spectrum and its red near-infrared colors ($J-K_S$ = 2.35$\\pm$0.08 mag) are indicative of a young age. Via comparison to spectral standards and other red L dwarfs, we estimate a near-infrared spectral type to be L7$\\pm$2 (pec). From a comparison to spectral and low-mass evolutionary models, we determine self-consistent effective temperature, log $g$, age, and mass values of 1450$\\pm$100 K, 4.0$\\pm$0.25 (cm s$^{-2}$), 10-100 Myr, and 4-21 M$_{Jup}$, respectively. With an estimated distance of 10-30 pc, we explore the possibility that WISE J174102.78-464225.5 belongs to one of the young nearby moving groups via a kinematic analysis and we find potential membership in the $\\beta$ Pictoris or AB Doradus associations. A trigonometric parallax measurement and a preci...

  7. A Model of Parallel Kinematics for Machine Calibration

    DEFF Research Database (Denmark)

    Pedersen, David Bue; Bæk Nielsen, Morten; Kløve Christensen, Simon

    2016-01-01

    Parallel kinematics have been adopted by more than 25 manufacturers of high-end desktop 3D printers [Wohlers Report (2015), p.118] as well as by research projects such as the WASP project [WASP (2015)], a 12 meter tall linear delta robot for Additive Manufacture of large-scale components...... developed in order to decompose the different types of geometrical errors into 6 elementary cases. Deliberate introduction of errors to the virtual machine has subsequently allowed for the generation of deviation plots that can be used as a strong tool for the identification and correction of geometrical...... errors on a physical machine tool....

  8. Implications for the origin of early-type dwarf galaxies - the discovery of rotation in isolated, low-mass early-type galaxies

    Science.gov (United States)

    Janz, Joachim; Penny, Samantha J.; Graham, Alister W.; Forbes, Duncan A.; Davies, Roger L.

    2017-07-01

    We present the discovery of rotation in quenched, low-mass early-type galaxies that are isolated. This finding challenges the claim that (all) rotating dwarf early-type galaxies in clusters were once spiral galaxies that have since been harassed and transformed into early-type galaxies. Our search of the Sloan Digital Sky Survey data within the Local Volume (z half-light radius Re in the best cases, and beyond Re/2 for all. They reveal a variety of behaviours similar to those of a comparison sample of early-type dwarf galaxies in the Virgo cluster observed by Toloba et al. Both samples have similar frequencies of slow and fast rotators, as well as kinematically decoupled cores. This, and especially the finding of rotating quenched low-mass galaxies in isolation, reveals that the early-type dwarfs in galaxy clusters need not be harassed or tidally stirred spiral galaxies.

  9. Magnetars and white dwarf pulsars

    Science.gov (United States)

    Lobato, Ronaldo V.; Malheiro, Manuel; Coelho, Jaziel G.

    2016-07-01

    The anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are a class of pulsars understood as neutron stars (NSs) with super strong surface magnetic fields, namely B ≳ 1014G, and for that reason are known as magnetars. However, in the last years, some SGRs/AXPs with low surface magnetic fields B ˜ (1012-1013)G have been detected, challenging the magnetar description. Moreover, some fast and very magnetic white dwarfs (WDs) have also been observed, and at least one showed X-ray energy emission as an ordinary pulsar. Following this fact, an alternative model based on WDs pulsars has been proposed to explain this special class of pulsars. In this model, AXPs and SGRs as dense and magnetized WDs can have surface magnetic field B ˜ 107-1010 G and rotate very fast with frequencies Ω ˜ 1rad/s, consistent with the observed rotation periods P ˜ (2-12)s.

  10. Dyson Spheres around White Dwarfs

    CERN Document Server

    Semiz, İbrahim

    2015-01-01

    A Dyson Sphere is a hypothetical structure that an advanced civilization might build around a star to intercept all of the star's light for its energy needs. One usually thinks of it as a spherical shell about one astronomical unit (AU) in radius, and surrounding a more or less Sun-like star; and might be detectable as an infrared point source. We point out that Dyson Spheres could also be built around white dwarfs. This type would avoid the need for artificial gravity technology, in contrast to the AU-scale Dyson Spheres. In fact, we show that parameters can be found to build Dyson Spheres suitable --temperature- and gravity-wise-- for human habitation. This type would be much harder to detect.

  11. Pluto: Planet or "Dwarf Planet"?

    Science.gov (United States)

    Voelzke, M. R.; de Araújo, M. S. T.

    2010-09-01

    In August 2006 during the XXVI General Assembly of the International Astronomical Union (IAU), taken place in Prague, Czech Republic, new parameters to define a planet were established. According to this new definition Pluto will be no more the ninth planet of the Solar System but it will be changed to be a "dwarf planet". This reclassification of Pluto by the academic community clearly illustrates how dynamic science is and how knowledge of different areas can be changed and evolves through the time, allowing to perceive Science as a human construction in a constant transformation, subject to political, social and historical contexts. These epistemological characteristics of Science and, in this case, of Astronomy, constitute important elements to be discussed in the lessons, so that this work contributes to enable Science and Physics teachers who perform a basic education to be always up to date on this important astronomical fact and, thereby, carry useful information to their teaching.

  12. The First Substellar Subdwarf? Discovery of a Metal-poor L Dwarf with Halo Kinematics

    CERN Document Server

    Burgasser, A J; Burrows, A; Liebert, J; Reid, I N; Gizis, J E; McGovern, M R; Prato, L; McLean, I S; Burgasser, Adam J.; Burrows, Adam; Liebert, James; Gizis, John E.; Govern, Mark R. Mc; Lean, Ian S. Mc

    2003-01-01

    We present the discovery of the first L-type subdwarf, 2MASS J05325346+8246465. This object exhibits enhanced collision-induced H$_2$ absorption, resulting in blue NIR colors ($J-K_s = 0.26{\\pm}0.16$). In addition, strong hydride bands in the red optical and NIR, weak TiO absorption, and an optical/J-band spectral morphology similar to the L7 DENIS 0205$-$1159AB imply a cool, metal-deficient atmosphere. We find that 2MASS 0532+8246 has both a high proper motion, $\\mu$ = 2$\\farcs60\\pm0\\farcs$15 yr$^{-1}$, and a substantial radial velocity, $v_{rad} = -195{\\pm}11$ km s$^{-1}$, and its probable proximity to the Sun (d = 10--30 pc) is consistent with halo membership. Comparison to subsolar-metallicity evolutionary models strongly suggests that 2MASS 0532+8246 is substellar, with a mass of 0.077 $\\lesssim$ M $\\lesssim$ 0.085 M$_{\\sun}$ for ages 10--15 Gyr and metallicities $Z = 0.1-0.01$ $Z_{\\sun}$. The discovery of this object clearly indicates that star formation occurred below the Hydrogen burning mass limit at...

  13. A nearby young M dwarf with a wide, possibly planetary-mass companion

    Science.gov (United States)

    Deacon, N. R.; Schlieder, J. E.; Murphy, S. J.

    2016-04-01

    We present the identification of two previously known young objects in the solar neighbourhood as a likely very wide binary. TYC 9486-927-1, an active, rapidly rotating early-M dwarf, and 2MASS J21265040-8140293, a low-gravity L3 dwarf previously identified as candidate members of the ˜45 Myr old Tucana-Horologium association (TucHor). An updated proper motion measurement of the L3 secondary, and a detailed analysis of the pair's kinematics in the context of known nearby, young stars, reveals that they share common proper motion and are likely bound. New observations and analyses reveal the primary exhibits Li 6708 Å absorption consistent with M dwarfs younger than TucHor but older than the ˜10 Myr TW Hydra association yielding an age range of 10-45 Myr. A revised kinematic analysis suggests the space motions and positions of the pair are closer to, but not entirely in agreement with, the ˜24 Myr old β Pictoris moving group. This revised 10-45 Myr age range yields a mass range of 11.6-15 MJ for the secondary. It is thus likely 2MASS J2126-8140 is the widest orbit planetary-mass object known (>4500 au) and its estimated mass, age, spectral type, and Teff are similar to the well-studied planet β Pictoris b. Because of their extreme separation and youth, this low-mass pair provide an interesting case study for very wide binary formation and evolution.

  14. Unveiling the Secret of a Virgo Dwarf Galaxy

    Science.gov (United States)

    2000-05-01

    case of the seemingly inconspicuous dwarf galaxy IC 3382 , the astronomers made an amazing discovery. When the best fitting model was removed from the observed image, a neat and regular spiral structure appeared in the residual image, cf. PR Photo 11/00 ! Nothing like this has ever been seen before in a dwarf elliptical galaxy. The light associated with the spiral constitutes a 3% modulation of the surface brightness. To see this effect at all, requires the excellent image quality of FORS1 and ANTU. The origin of the spiral structure What is the cause for this faintest and smallest spiral ever discovered in a galaxy? Two possible explanations have been proposed by the astronomers. It has been known for several decades that the spiral patterns seen in disk galaxies, like for instance in the Milky Way galaxy, are "density waves". The patterns are due to collective oscillations in the gravitational field that moves the stars and gas back and forth. The presence of a spiral pattern in IC3328 implies that it harbours a thin disk. The available data do not allow to distinguish between a pure disk galaxy, or a disk embedded in a spheroidal mass distribution. Both configurations are known to exist. Transient spiral patterns, as that seen in the well-known, nearby galaxy Messier 51, can be generated by tidal interactions . In the present case, there are two close and faint dwarf galaxies which may have disturbed IC3328 in the past and thereby produced the spiral pattern we now see. If what we see is a pure disk galaxy, the exceptionally small amplitude of the spiral pattern suggests another possibility: it could be swing-amplified noise . A modest amount of cold lumpy gas in the disk may have provided some initial "graininess" which was then gradually amplified by a shearing effect of the stellar orbits in the disk to produce the striking spiral pattern we now see. More information about this project A research article about this discovery is being published in the European

  15. Shell Galaxies, Dynamical Friction, and Dwarf Disruption

    CERN Document Server

    Ebrova, Ivana; Canalizo, Gabriela; Bennert, Nicola; Jilkova, Lucie

    2009-01-01

    Using N-body simulations of shell galaxies created in nearly radial minor mergers, we investigate the error of collision dating, resulting from the neglect of dynamical friction and of gradual disruption of the cannibalized dwarf.

  16. Merging White Dwarfs and Thermonuclear Supernovae

    CERN Document Server

    van Kerkwijk, Marten H

    2012-01-01

    Thermonuclear supernovae result when interaction with a companion reignites nuclear fusion in a carbon-oxygen white dwarf, causing a thermonuclear runaway, a catastrophic gain in pressure, and the disintegration of the whole white dwarf. It is usually thought that fusion is reignited in near-pycnonuclear conditions when the white dwarf approaches the Chandrasekhar mass. I briefly describe two long-standing problems faced by this scenario, and our suggestion that these supernovae instead result from mergers of carbon-oxygen white dwarfs, including those that produce sub-Chandrasekhar mass remnants. I then turn to possible observational tests, in particular those that test the absence or presence of electron captures during the burning.

  17. Magnetic white dwarfs with debris disks

    CERN Document Server

    Külebi, Baybars; Lorén-Aguilar, Pablo; Isern, Jordi; García-Berro, Enrique

    2012-01-01

    It has long been accepted that a possible mechanism for explaining the existence of magnetic white dwarfs is the merger of a binary white dwarf system, as there are viable mechanisms for producing sustainable magnetism within the merger product. However, the lack of rapid rotators in the magnetic white dwarf population has been always considered a problematic issue of this scenario. In order to explain this discrepancy we build a model in which the interaction between the magnetosphere of the star and the disk induces angular momentum transfer. Our model predicts that the magnetospheric interaction of magnetic white dwarfs with their disks results in a significant spin down, and we show that the observed rotation period of REJ 0317-853, which is suggested to be a product of a double degenerate merger, can be reproduced.

  18. Building Magnetic Fields in White Dwarfs

    Science.gov (United States)

    Kohler, Susanna

    2017-03-01

    White dwarfs, the compact remnants left over at the end of low- and medium-mass stars lifetimes, are often found to have magnetic fields with strengths ranging from thousands to billions of times that of Earth. But how do these fields form?MultiplePossibilitiesAround 1020% of white dwarfs have been observed to have measurable magnetic fields with a wide range of strengths. There are several theories as to how these fields might be generated:The fields are fossil.The original weak magnetic fields of the progenitor stars were amplified as the stars cores evolved into white dwarfs.The fields are caused by binary interactions.White dwarfs that formed in the merger of a binary pair might have had a magnetic field amplified as a result of a dynamo that was generated during the merger.The fields were produced by some other internal physical mechanism during the cooling of the white dwarf itself.In a recent publication, a team of authors led by Jordi Isern (Institute of Space Sciences, CSIC, and Institute for Space Studies of Catalonia, Spain) explored this third possibility.Dynamos from CrystallizationThe inner and outer boundaries of the convective mantle of carbon/oxygen white dwarfs of two different masses (top vs. bottom panel) as a function of luminosity. As the white dwarf cools (toward the right), the mantle grows thinner due to the crystallization and settling of material. [Isern et al. 2017]As white dwarfs have no nuclear fusion at their centers, they simply radiate heat and gradually cool over time. The structure of the white dwarf undergoes an interesting change as it cools, however: though the object begins as a fluid composed primarily of an ionized mixture of carbon and oxygen (and a few minor species like nickel and iron), it gradually crystallizes as its temperature drops.The crystallized phase of the white dwarf is oxygen-rich which is denser than the liquid, so the crystallized material sinks to the center of the dwarf as it solidifies. As a result, the

  19. Giant planet and brown dwarf formation

    CERN Document Server

    Chabrier, G; Janson, M; Rafikov, R

    2014-01-01

    Understanding the dominant brown dwarf and giant planet formation processes, and finding out whether these processes rely on completely different mechanisms or share common channels represents one of the major challenges of astronomy and remains the subject of heated debates. It is the aim of this review to summarize the latest developments in this field and to address the issue of origin by confronting different brown dwarf and giant planet formation scenarios to presently available observational constraints. As examined in the review, if objects are classified as "Brown Dwarfs" or "Giant Planets" on the basis of their formation mechanism, it has now become clear that their mass domains overlap and that there is no mass limit between these two distinct populations. Furthermore, while there is increasing observational evidence for the existence of non-deuterium burning brown dwarfs, some giant planets, characterized by a significantly metal enriched composition, might be massive enough to ignite deuterium bur...

  20. White Dwarfs, Neutron Stars and Black Holes

    Science.gov (United States)

    Szekeres, P.

    1977-01-01

    The three possible fates of burned-out stars: white dwarfs, neutron stars and black holes, are described in elementary terms. Characteristics of these celestial bodies, as provided by Einstein's work, are described. (CP)

  1. Pulsating White Dwarf Stars and Precision Asteroseismology

    CERN Document Server

    Winget, D E

    2008-01-01

    Galactic history is written in the white dwarf stars. Their surface properties hint at interiors composed of matter under extreme conditions. In the forty years since their discovery, pulsating white dwarf stars have moved from side-show curiosities to center stage as important tools for unraveling the deep mysteries of the Universe. Innovative observational techniques and theoretical modeling tools have breathed life into precision asteroseismology. We are just learning to use this powerful tool, confronting theoretical models with observed frequencies and their time rate-of-change. With this tool, we calibrate white dwarf cosmochronology; we explore equations of state; we measure stellar masses, rotation rates, and nuclear reaction rates; we explore the physics of interior crystallization; we study the structure of the progenitors of Type Ia supernovae, and we test models of dark matter. The white dwarf pulsations are at once the heartbeat of galactic history and a window into unexplored and exotic physics.

  2. Pulsating White Dwarf Stars and Precision Asteroseismology

    Science.gov (United States)

    Winget, D. E.; Kepler, S. O.

    2008-09-01

    Galactic history is written in the white dwarf stars. Their surface properties hint at interiors composed of matter under extreme conditions. In the forty years since their discovery, pulsating white dwarf stars have moved from side-show curiosities to center stage as important tools for unraveling the deep mysteries of the Universe. Innovative observational techniques and theoretical modeling tools have breathed life into precision asteroseismology. We are just learning to use this powerful tool, confronting theoretical models with observed frequencies and their time rate-of-change. With this tool, we calibrate white dwarf cosmochronology; we explore equations of state; we measure stellar masses, rotation rates, and nuclear reaction rates; we explore the physics of interior crystallization; we study the structure of the progenitors of Type Ia supernovae, and we test models of dark matter. The white dwarf pulsations are at once the heartbeat of galactic history and a window into unexplored and exotic physics.

  3. Identifying Dwarfs Workloads in Big Data Analytics

    OpenAIRE

    Gao, Wanling; Luo, Chunjie; Zhan, Jianfeng; Ye, Hainan; He, Xiwen; Wang, Lei; Zhu, Yuqing; Tian, Xinhui

    2015-01-01

    Big data benchmarking is particularly important and provides applicable yardsticks for evaluating booming big data systems. However, wide coverage and great complexity of big data computing impose big challenges on big data benchmarking. How can we construct a benchmark suite using a minimum set of units of computation to represent diversity of big data analytics workloads? Big data dwarfs are abstractions of extracting frequently appearing operations in big data computing. One dwarf represen...

  4. Abundance analysis of DAZ white dwarfs

    CERN Document Server

    Kawka, Adela; Dinnbier, Frantisek; Cibulkova, Helena; Nemeth, Peter

    2010-01-01

    We present an abundance analysis of a sample of 33 hydrogen-rich (DA) white dwarfs. We have used archival high-resolution spectra to measure abundances of calcium, magnesium and iron in a set of 30 objects. In addition, we present preliminary calcium abundances in three new white dwarfs based on low-dispersion spectra. We investigate some abundance ratios (Mg/Ca, Fe/Ca) that may help uncover the composition of the accretion source.

  5. Morphological transformations of Dwarf Galaxies in the Local Group

    CERN Document Server

    Carraro, Giovanni

    2014-01-01

    In the Local Group there are three main types of dwarf galaxies: Dwarf Irregulars, Dwarf Spheroidals, and Dwarf Ellipticals. Intermediate/transitional types are present as well. This contribution reviews the idea that the present day variety of dwarf galaxy morphologies in the Local Group might reveal the existence of a transformation chain of events, of which any particular dwarf galaxy represents a manifestation of a particular stage. In other words, all dwarf galaxies that now are part of the Local Group would have formed identically in the early universe, but then evolved differently because of morphological transformations induced by dynamical processes like galaxy harassment, ram pressure stripping, photo-evaporation, and so forth. We start describing the population of dwarf galaxies and their spatial distribution in the LG. Then, we describe those phenomena that can alter the morphology of a dwarf galaxies, essentially by removing, partially or completely, their gas content. Lastly, we discuss morpholo...

  6. A radio pulsing white dwarf binary star

    CERN Document Server

    Marsh, T R; Hümmerich, S; Hambsch, F -J; Bernhard, K; Lloyd, C; Breedt, E; Stanway, E R; Steeghs, D T; Parsons, S G; Toloza, O; Schreiber, M R; Jonker, P G; van Roestel, J; Kupfer, T; Pala, A F; Dhillon, V S; Hardy, L K; Littlefair, S P; Aungwerojwit, A; Arjyotha, S; Koester, D; Bochinski, J J; Haswell, C A; Frank, P; Wheatley, P J

    2016-01-01

    White dwarfs are compact stars, similar in size to Earth but ~200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions, and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf / cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a delta-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56 hr period close binary, pulsing in brightness on a period of 1.97 min. The pulses are so intense that AR Sco's optical flux can increase by a factor of four within 30 s, and they are detectable a...

  7. Comparison of theoretical white dwarf cooling timescales

    CERN Document Server

    Salaris, Maurizio; García-Berro, Enrique

    2013-01-01

    An accurate assessment of white dwarf cooling times is paramount to place white dwarf cosmochronology of Galactic populations on more solid grounds. This issue is particularly relevant in view of the enhanced observational capabilities provided by the next generation of Extremely Large Telescopes, that will offer more avenues to employ white dwarfs as probes of Galactic evolution and test-beds of fundamental physics. We estimate for the first time the consistency of results obtained from two independent and widely used evolutionary codes (BaSTI and LPCODE) for white dwarf models with fixed mass and chemical stratification, when the same input physics is employed in both codes. We considered 0.55Msun white dwarf models with both pure carbon and uniform carbon-oxygen (50/50 mass fractions) core. We have assessed for the first time the maximum possible accuracy in the current estimates of white dwarf cooling times, resulting only from the different implementations of the stellar evolution equations and homogeneo...

  8. ON THE EVOLUTION OF MAGNETIC WHITE DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Tremblay, P.-E. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Fontaine, G.; Brassard, P. [Département de Physique, Université de Montréal, C. P. 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7 (Canada); Freytag, B. [Department of Physics and Astronomy at Uppsala University, Regementsvägen 1, Box 516, SE-75120 Uppsala (Sweden); Steiner, O. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany); Ludwig, H.-G. [Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, D-69117 Heidelberg (Germany); Steffen, M. [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Wedemeyer, S., E-mail: tremblay@stsci.edu [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway)

    2015-10-10

    We present the first radiation magnetohydrodynamic simulations of the atmosphere of white dwarf stars. We demonstrate that convective energy transfer is seriously impeded by magnetic fields when the plasma-β parameter, the thermal-to-magnetic-pressure ratio, becomes smaller than unity. The critical field strength that inhibits convection in the photosphere of white dwarfs is in the range B = 1–50 kG, which is much smaller than the typical 1–1000 MG field strengths observed in magnetic white dwarfs, implying that these objects have radiative atmospheres. We have employed evolutionary models to study the cooling process of high-field magnetic white dwarfs, where convection is entirely suppressed during the full evolution (B ≳ 10 MG). We find that the inhibition of convection has no effect on cooling rates until the effective temperature (T{sub eff}) reaches a value of around 5500 K. In this regime, the standard convective sequences start to deviate from the ones without convection due to the convective coupling between the outer layers and the degenerate reservoir of thermal energy. Since no magnetic white dwarfs are currently known at the low temperatures where this coupling significantly changes the evolution, the effects of magnetism on cooling rates are not expected to be observed. This result contrasts with a recent suggestion that magnetic white dwarfs with T{sub eff} ≲ 10,000 K cool significantly slower than non-magnetic degenerates.

  9. Spectroscopy of Hyades L dwarf candidates

    CERN Document Server

    Lodieu, N; Bejar, V J S

    2014-01-01

    We present the results of photometric, astrometric, and spectroscopic follow-up of L dwarf candidates identified in the Hyades cluster by Hogan et al. (2008). We obtained low-resolution optical spectroscopy with the OSIRIS spectrograph on the Gran Telescopio de Canarias for all 12 L dwarf candidates as well as new J-band imaging for a subsample of eight to confirm their proper motion. We also present mid-infrared photometry from the Wise Field Infrared Survey Explorer (WISE) for the Hyades L and T dwarf candidates and estimate their spectroscopic distances, effective temperatures, and masses. We confirm the cool nature of several L dwarf candidates and confirm astrometrically their membership, bridging the gap between the coolest M dwarfs and the two T dwarfs previously reported in the Hyades cluster. These members represent valuable spectral templates at an age of 625 Myr and slightly super solar metallicity (Fe/H=+0.13). We update the Hyades mass function across the hydrogen-burning limit and in the substel...

  10. An assessment of the "too big to fail" problem for field dwarf galaxies in view of baryonic feedback effects

    CERN Document Server

    Papastergis, Emmanouil

    2015-01-01

    Recent studies have established that extreme dwarf galaxies --whether satellites or field objects-- suffer from the so called "too big to fail" (TBTF) problem. Put simply, the TBTF problem consists of the fact that it is difficult to explain both the measured kinematics of dwarfs and their observed number density within the LCDM framework. The most popular proposed solutions to the problem involve baryonic feedback processes. For example, reionization and baryon depletion can decrease the abundance of halos that are expected to host dwarf galaxies. Moreover, feedback related to star formation can alter the dark matter density profile in the central regions of low-mass halos. In this article we assess the TBTF problem for field dwarfs, taking explicitly into account the baryonic effects mentioned above. We find that 1) reionization feedback cannot resolve the TBTF problem on its own, because the halos in question are too massive to be affected by it, and that 2) the degree to which profile modification can be ...

  11. 2MASSJ035523.51+113337.4: A Young, Dusty, Nearby, Isolated Brown Dwarf Resembling A Giant Exoplanet

    CERN Document Server

    Faherty, Jacqueline K; Cruz, Kelle L; Mamajek, Eric E; Núñez, Alejandro

    2012-01-01

    We present parallax and proper motion measurements, near-infrared spectra, and WISE photometry for the low surface gravity L5gamma dwarf 2MASSJ035523.51+113337.4 (2M0355). We use these data to evaluate photometric, spectral, and kinematic signatures of youth. We confirm low-gravity spectral morphology and find a strong resemblance to the sharp triangular shaped H-band spectrum of the ~10 Myr planetary-mass object 2MASSJ1207b. We find that 2M0355 is underluminous compared to a normal field L5 dwarf in the optical and MKO J,H, and K bands and transitions to being overluminous from 3-12 microns indicating that enhanced photospheric dust shifts flux to longer wavelengths for young, low-gravity objects, creating a red spectral energy distribution. Investigating the near-infrared color magnitude diagram for brown dwarfs confirms that 2M0355 is redder and underluminous compared to the known brown dwarf population, similar to the peculiarities of directly imaged exoplanets 2MASSJ1207b and HR8799bcd. We calculate UVW ...

  12. Influence of shoulder kinematic estimate on joint and muscle mechanics predicted by musculoskeletal model.

    Science.gov (United States)

    Blache, Yoann; Begon, Mickael

    2017-06-15

    Little information is available in the existing literature regarding the influence of the scapular kinematic estimate method on musculoskeletal analysis. This study aimed to assess the propagation of errors due to the method used for scapular kinematics reconstruction in the workflow of musculoskeletal modeling (joint kinematics, joint torques, muscle force and joint reaction force) in shoulder and upper-limb movements. Two participants performed functional (arm elevation and rotation), daily life (eating and reaching pants pockets) and sports movements (a simulated throwing maneuver). Shoulder kinematics were obtained with five multibody kinematics methods: intra-cortical pins (Pins, reference method), International Society of Biomechanics (ISB), Jackson (Jack), Projection (Proj) and Ellipsoid (Ell) methods. For the five kinematics methods, joint torques, muscle forces and glenohumeral joint reaction forces were computed with the Delft Shoulder and Elbow musculoskeletal model. Differences up to 30° in glenohumeral joint kinematics, compared to the Pins method, resulted in differences less than 3 N.m in joint torque estimation. However, these also resulted in differences up to 50 N and 831 N in the muscle force and joint reaction force estimate, respectively, in comparison to the reference method (Pins). No method yielded the worst or best results in comparison to the Pins method but the differences were task-specific. We concluded that shoulder biomechanical studies based on skin markers should be completed with caution when assessing joint angles, muscle forces and glenohumeral joint reaction forces, while researchers may be more confident with the evaluation of shoulder joint torques.

  13. Calibration of a Parallel Kinematic Machine Tool

    Institute of Scientific and Technical Information of China (English)

    HE Xiao-mei; DING Hong-sheng; FU Tie; XIE Dian-huang; XU Jin-zhong; LI Hua-feng; LIU Hui-lin

    2006-01-01

    A calibration method is presented to enhance the static accuracy of a parallel kinematic machine tool by using a coordinate measuring machine and a laser tracker. According to the established calibration model and the calibration experiment, the factual 42 kinematic parameters of BKX-I parallel kinematic machine tool are obtained. By circular tests the comparison is made between the calibrated and the uncalibrated parameters and shows that there is 80% improvement in accuracy of this machine tool.

  14. Kinematically complete chemical reaction dynamics

    Science.gov (United States)

    Trippel, S.; Stei, M.; Otto, R.; Hlavenka, P.; Mikosch, J.; Eichhorn, C.; Lourderaj, U.; Zhang, J. X.; Hase, W. L.; Weidemüller, M.; Wester, R.

    2009-11-01

    Kinematically complete studies of molecular reactions offer an unprecedented level of insight into the dynamics and the different mechanisms by which chemical reactions occur. We have developed a scheme to study ion-molecule reactions by velocity map imaging at very low collision energies. Results for the elementary nucleophilic substitution (SN2) reaction Cl- + CH3I → ClCH3 + I- are presented and compared to high-level direct dynamics trajectory calculations. Furthermore, an improved design of the crossed-beam imaging spectrometer with full three-dimensional measurement capabilities is discussed and characterization measurements using photoionization of NH3 and photodissociation of CH3I are presented.

  15. Kinematics and Mass Modeling of Messier 33: Halpha observations

    CERN Document Server

    Kam, Zacharie Sie; Chemin, Laurent; Amram, Philippe; Epinat, Benoit

    2015-01-01

    As part of a long-term project to revisit the kinematics and dynamics of the large disc galaxies of the Local Group, we present the first deep, wide-field (42' x 56') 3D-spectroscopic survey of the ionized gas disc of Messier 33. Fabry-Perot interferometry has been used to map its Ha distribution and kinematics at unprecedented angular resolution ( 6.5 kpc. The reason for this discrepancy is not well understood. The velocity dispersion profile is relatively flat around 16 km/s, which is at the low end of velocity dispersions of nearby star-forming galactic discs. A strong relation is also found between the Ha velocity dispersion and the Ha intensity. Mass models were obtained using the Ha rotation curve but, as expected, the dark matter halo's parameters are not very well constrained since the optical rotation curve only extends out to 8 kpc.

  16. Investigating The Kinematics of Canids and Felids

    Science.gov (United States)

    Sur, D.

    2016-12-01

    For all organisms, metabolic energy is critical for survival. While moving efficiently is a necessity for large carnivores, the influence of kinematics on energy demand remains poorly understood. We measured the kinematics of dogs, wolves, and pumas to detect any differences in their respective energy expenditures. Using 22 kinematic parameters measured on 78 videos, we used one-way ANOVAs and paired T-tests to compare 5 experimental treatments among gaits in dogs (n=11 in 3 breed groups), wolves (n=2), and pumas (n=2). Across the measured parameters, we found greater kinematic similarity than expected among dog breeds and no trend in any of the 22 parameters regarding the effect of steepness on locomotion mechanics. Similarly, treadmill kinematics were nearly identical to those measured during outdoor movement. However, in 3 inches of snow, we observed significant differences (pwolves and dogs) to a felid (pumas), we found that pumas and dogs are the most kinematically distinct (differing in 13 of 22 parameters, compared with 5 of 22 for wolves and pumas). Lastly, compared with wolves, walking pumas had larger head angles (p=0.0025), forelimb excursion angles (p=0.0045), and hindlimb excursion angles (p=0.0327). After comparing the energetics of pumas and dogs with their respective kinematics, we noted that less dynamic kinematics result in energy savings. Through tracking the locations and gait behavior of large carnivores, novel sensor technology can reveal how indoor kinematics applies to wild animals and improve the conservation of these species.

  17. Response of dwarf mistletoe-infested ponderosa pine to thinning: 2. Dwarf mistletoe propagation.

    Science.gov (United States)

    Lewis F. Roth; James W. Barrett

    1985-01-01

    Propagation of dwarf mistletoe in ponderosa pine saplings is little influenced by thinning overly dense stands to 250 trees per acre. Numerous plants that appear soon after thinning develop from formerly latent plants in the suppressed under-story. Subsequently, dwarf mistletoe propagates nearly as fast as tree crowns enlarge but the rate differs widely among trees....

  18. Follow-up Observations of SPY White Dwarf + M-Dwarf Binaries

    NARCIS (Netherlands)

    Maxted, P.F.L.; Napiwotzki, R.; Marsh, T.R.; Burleigh, M.R.; Dobbie, P.D.; Hogan, E.; Nelemans, G.A.

    2007-01-01

    We present the results of follow-up observations of white-dwarf + M-dwarf binaries identified using spectra obtained as part of the SPY survey. Spectra of the Halpha region were obtained with the SPIRAL spectrograph on the AAT telescope. Of the eleven stars observed, seven are binaries with periods

  19. Unbiased constraints on ultralight axion mass from dwarf spheroidal galaxies

    CERN Document Server

    Gonzáles-Morales, Alma X; Peñarrubia, Jorge; Ureña-López, Luis

    2016-01-01

    It has been suggested that the internal dynamics of dwarf spheroidal galaxies (dSphs) can be used to test whether or not ultralight axions with $m_a\\sim 10^{-22}\\text{eV}$ are a preferred dark matter candidate. However, comparisons to theoretical predictions tend to be inconclusive for the simple reason that while most cosmological models consider only dark matter, one observes only baryons. Here we use realistic kinematic mock data catalogs of Milky Way dSph's to show that the "mass-anisotropy degeneracy" in the Jeans equations leads to biased bounds on the axion mass in galaxies with unknown dark matter halo profiles. In galaxies with multiple chemodynamical components this bias can be partly removed by modelling the mass enclosed within each subpopulation. However, analysis of the mock data reveals that the least-biased constraints on the axion mass result from fitting the luminosity-averaged velocity dispersion of the individual chemodynamical components directly. Applying our analysis to two dSph's with ...

  20. The Origin of Dwarf Early-Type Galaxies

    CERN Document Server

    Toloba, Elisa

    2012-01-01

    Abridge. We have conducted a spectrophotometric study of dwarf early-type galaxies (dEs) in the Virgo cluster and in regions of lower density. We have found that these galaxies show many properties in common with late-type galaxies but not with more massive early-types (E/S0). The properties of the dEs in Virgo show gradients within the cluster. dEs in the outer parts of the Virgo cluster are kinematically supported by rotation, while those in the center are supported by the random motions of their stars (i.e. pressure supported). The rotationally supported dEs have disky isophotes and faint underlying spiral/irregular substructures, they also show younger ages than those pressure supported, which have boxy isophotes and are smooth and regular, without any substructure. We compare the position of these dEs with massive early-type galaxies in the Faber-Jackson and Fundamental Plane relations, and we find that, although there is no difference between the position of rotationally and pressure supported dEs, both...

  1. Magnetic fields in Local Group dwarf irregulars

    Science.gov (United States)

    Chyży, K. T.; Weżgowiec, M.; Beck, R.; Bomans, D. J.

    2011-05-01

    Aims: We wish to clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and to assess the role of dwarf galaxies in the magnetization of the Universe. Methods: We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100-m Effelsberg telescope at 2.64 GHz. Three galaxies were detected. A higher frequency (4.85 GHz) was used to search for polarized emission in five dwarfs that are the most luminous ones in the infrared domain, of which three were detected. Results: Magnetic fields in LG dwarfs are weak, with a mean value of the total field strength of regulated mainly by the star-formation surface density (with the power-law exponent of 0.30 ± 0.04) or by the gas surface density (with the exponent 0.47 ± 0.09). In addition, we find systematically stronger fields in objects of higher global star-formation rate. The dwarf galaxies follow a similar far-infrared relationship (with a slope of 0.91 ± 0.08) to that determined for high surface brightness spiral galaxies. The magnetic field strength in dwarf galaxies does not correlate with their maximum rotational velocity, indicating that a small-scale rather than a large-scale dynamo process is responsible for producting magnetic fields in dwarfs. If magnetization of the Universe by galactic outflows is coeval with its metal enrichment, we show that more massive objects (such as Lyman break galaxies) can efficiently magnetize the intergalactic medium with a magnetic field strength of about 0.8 nG out to a distance of 160-530 kpc at redshifts 5-3, respectively. Magnetic fields that are several times weaker and shorter magnetization distances are expected for primordial dwarf galaxies. We also predict that most star-forming local dwarfs might have magnetized their surroundings up to a field strength about 0.1 μG within about a 5 kpc distance. Conclusions: Strong magnetic

  2. Building an Unusual White-Dwarf Duo

    Science.gov (United States)

    Kohler, Susanna

    2016-09-01

    A new study has examined how the puzzling wide binary system HS 2220+2146 which consists of two white dwarfs orbiting each other might have formed. This system may be an example of a new evolutionary pathway for wide white-dwarf binaries.Evolution of a BinaryMore than 100 stellar systems have been discovered consisting of two white dwarfs in a wide orbit around each other. How do these binaries form? In the traditional picture, the system begins as a binary consisting of two main-sequence stars. Due to the large separation between the stars, the stars evolve independently, each passing through the main-sequence and giant branches and ending their lives as white dwarfs.An illustration of a hierarchical triple star system, in which two stars orbit each other, and a third star orbits the pair. [NASA/JPL-Caltech]Because more massive stars evolve more quickly, the most massive of the two stars in a binary pair should be the first to evolve into a white dwarf. Consequently, when we observe a double-white-dwarf binary, its usually a safe bet that the more massive of the two white dwarfs will also be the older and cooler of the pair, since it should have formed first.But in the case of the double-white-dwarf binary HS 2220+2146, the opposite is true: the more massive of the two white dwarfs appears to be the younger and hotter of the pair. If it wasnt created in the traditional way, then how did this system form?Two From Three?Led by Jeff Andrews (Foundation for Research and Technology-Hellas, Greece and Columbia University), a team of scientists recently examined this system more carefully, analyzing its spectra to confirm our understanding of the white dwarfs temperatures and masses.Based on their observations, Andrews and collaborators determined that there are no hidden additional companions that could have caused the unusual evolution of this system. Instead, the team proposed that this unusual binary might be an example of an evolutionary channel that involves three

  3. Desert Dwellers and Dynamic Duos: Short-Period Brown Dwarf Companions and Binary Science with Exoplanet Surveys

    Science.gov (United States)

    Fleming, Scott W.; Ge, J.

    2011-01-01

    Exoplanet transit and Doppler surveys detect many binary stars and brown dwarf companions with relative ease because the observational signatures are 1-2 orders of magnitude larger than planets. These objects allow for studies of several ancillary science topics, such as the two brown dwarf deserts and the mass-radius relationship of stars. In this dissertation talk, I will present my thesis work on conducting these studies using data from the MARVELS survey and several transit survey databases. I will present the discovery of two short-period (P MARVELS survey and its Pilot Project. Although I will focus on these two brown dwarfs, the MARVELS survey has already discovered a dozen brown dwarf companions that will serve to characterize the dryness of the brown dwarf deserts. These discoveries are needed to better understand brown dwarf formation and dynamical evolution histories. I will then present results from my work on cross-referencing spectroscopic binaries found in the MARVELS survey with archival photometry to conduct studies of the mass-radius relationship. Finally, I will present spectroscopic observations of known eclipsing binaries from transit surveys using the EXPERT instrument at the KPNO 2.1m telescope.

  4. KINEMATICS OF OUTER HALO GLOBULAR CLUSTERS IN M31

    Energy Technology Data Exchange (ETDEWEB)

    Veljanoski, J.; Ferguson, A. M. N.; Bernard, E. J.; Penarrubia, J. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Mackey, A. D. [Research School of Astronomy and Astrophysics, Australian National University, Mt Stromlo Observatory, Weston Creek, ACT 2611 (Australia); Huxor, A. P. [Astronomisches Rechen-Institut, Zentrum fur Astronomie der Universitat Heidelberg, Monchhofstr. 12-14, D-69120 Heidelberg (Germany); Irwin, M. J.; Chapman, S. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Cote, P. [NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, British Columbia V9E 2E7 (Canada); Tanvir, N. R.; McConnachie, A. [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Ibata, R. A.; Martin, N. F. [Observatoire de Strasbourg, 11 rue de l' Universite, F-67000 Strasbourg (France); Fardal, M. [University of Massachusetts, Department of Astronomy, LGRT 619-E, 710 N. Pleasant Street, Amherst, MA 01003-9305 (United States); Lewis, G. F. [Institute of Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia)

    2013-05-10

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

  5. Chemical Compositions of Kinematically Selected Outer Halo Stars

    CERN Document Server

    Zhang, Lan; Aoki, Wako; Zhao, Gang; Chiba, Masashi

    2009-01-01

    Chemical abundances of 26 metal-poor dwarfs and giants are determined from high-resolution and high signal-to-noise ratio spectra obtained with Subaru/HDS. The sample is selected so that most of the objects have outer-halo kinematics. Self-consistent atmospheric parameters were determined by an iterative procedure based on spectroscopic analysis. Abundances of 13 elements, including $\\alpha$-elements (Mg, Si, Ca, Ti), odd-Z light elements (Na, Sc), iron-peak elements (Cr, Mn, Fe, Ni, Zn) and neutron-capture elements (Y, Ba), are determined by two independent data reduction and LTE analysis procedures, confirming the consistency of the stellar parameters and abundances results. We find a decreasing trend of [$\\alpha$/Fe] with increasing [Fe/H] for the range of $-3.5 <$ [Fe/H]$ < -1$, as found by Stephens and Boesgaard (2002). [Zn/Fe] values of most objects in our sample are slightly lower than the bulk of halo stars previously studied. These results are discussed as possible chemical properties of the ou...

  6. Metallic Winds in Dwarf Galaxies

    Science.gov (United States)

    Robles-Valdez, F.; Rodríguez-González, A.; Hernández-Martínez, L.; Esquivel, A.

    2017-02-01

    We present results from models of galactic winds driven by energy injected from nuclear (at the galactic center) and non-nuclear starbursts. The total energy of the starburst is provided by very massive young stellar clusters, which can push the galactic interstellar medium and produce an important outflow. Such outflow can be a well or partially mixed wind, or a highly metallic wind. We have performed adiabatic 3D N-Body/Smooth Particle Hydrodynamics simulations of galactic winds using the gadget-2 code. The numerical models cover a wide range of parameters, varying the galaxy concentration index, gas fraction of the galactic disk, and radial distance of the starburst. We show that an off-center starburst in dwarf galaxies is the most effective mechanism to produce a significant loss of metals (material from the starburst itself). At the same time, a non-nuclear starburst produces a high efficiency of metal loss, in spite of having a moderate to low mass loss rate.

  7. Manganese in dwarf spheroidal galaxies

    CERN Document Server

    North, P; Jablonka, P; Hill, V; Shetrone, M; Letarte, B; Lemasle, B; Venn, K A; Battaglia, G; Tolstoy, E; Irwin, M J; Primas, F; Francois, P

    2012-01-01

    We provide manganese abundances (corrected for the effect of the hyperfine structure) for a large number of stars in the dwarf spheroidal galaxies Sculptor and Fornax, and for a smaller number in the Carina and Sextans dSph galaxies. Abundances had already been determined for a number of other elements in these galaxies, including alpha and iron-peak ones, which allowed us to build [Mn/Fe] and [Mn/alpha] versus [Fe/H] diagrams. The Mn abundances imply sub-solar [Mn/Fe] ratios for the stars in all four galaxies examined. In Sculptor, [Mn/Fe] stays roughly constant between [Fe/H]\\sim -1.8 and -1.4 and decreases at higher iron abundance. In Fornax, [Mn/Fe] does not vary in any significant way with [Fe/H]. The relation between [Mn/alpha] and [Fe/H] for the dSph galaxies is clearly systematically offset from that for the Milky Way, which reflects the different star formation histories of the respective galaxies. The [Mn/alpha] behavior can be interpreted as a result of the metal-dependent Mn yields of type II and ...

  8. Cleaning spectroscopic samples of stars in nearby dwarf galaxies: The use of the nIR MgI line to weed out Milky Way contaminants

    CERN Document Server

    Battaglia, Giuseppina

    2012-01-01

    Dwarf galaxies provide insights on the processes of star formation and chemical enrichment at the low end of the galaxy mass function, as well as on the clustering of dark matter on small scales. In studies of Local Group dwarf galaxies, spectroscopic samples of individual stars are used to derive the internal kinematics and abundance properties of these galaxies. It is therefore important to clean these samples from Milky Way stars, not related to the dwarf galaxy, since they can contaminate the analysis of the properties of these objects. Here we introduce a new diagnostic for separating Milky Way contaminant stars -- that mainly constitute of dwarf stars -- and red giant branch stars targeted in dwarf galaxies. As discriminator we use the trends in the equivalent width of the nIR MgI line at 8806.8 \\AA\\ as a function of the equivalent width of CaII triplet lines. This method is particularly useful for works dealing with multi-object intermediate resolution spectroscopy focusing in the region of the nIR CaI...

  9. Kinematics of the free throw in basketball

    Science.gov (United States)

    Tan, A.; Miller, G.

    1981-06-01

    The kinematics of the two basic styles of free throw in basketball are discussed. It is shown that from a purely kinematic and trajectory point of view, the overhand push shot is preferable to the underhand loop shot. The advantages of the underhand shot lie in the actual execution of the shot.

  10. Kinematics of Stars in Kapteyn Selected Area 71: Sampling the Monoceros and Sagittarius Tidal Streams

    CERN Document Server

    Casetti-Dinescu, Dana I; Girard, Terrence M; Majewski, Steven R; Peñarrubia, Jorge; Patterson, Richard J

    2008-01-01

    We present a 3D kinematical analysis of stars located in Kapteyn Selected Area 71 (l = 167.1, b = -34.7), where previously a stellar excess was found (Dinescu et al. 2002, Newberg et al. 2002). Previous findings indicated that the stellar excess has a cold kinematical signature as inferred from proper motions, and was initially associated with debris from the Sagittarius dwarf galaxy (Sgr) -- namely the southern trailing tail. We have obtained radial velocities using the Hydra multiobject spectrograph on the WIYN 3.5 m telescope. Results for 183 proper-motion selected stars indicate that the dominant population in this stellar excess is not debris from Sgr, but rather a population that kinematically belongs to the ring-like stream that is now known as the Monoceros stream. The orbit determined for this population agrees very well with the predictions for the Monoceros stream from Penarrubia et al. (2005). The radial-velocity dispersion of this population is between 20 and 30 km/s, lower than that of the Galac...

  11. Automated kinematic generator for surgical robotic systems.

    Science.gov (United States)

    Jung, David L; Dixon, Warren E; Pin, François G

    2004-01-01

    Unlike traditional assembly line robotic systems that have a fixed kinematic structure associated with a single tool for a structured task, next-generation robotic surgical assist systems will be required to use an array of end-effector tools. Once a robot is connected with a tool, the kinematic equations of motion are altered. Given the need to accommodate evolving surgical challenges and to alleviate the restrictions imposed by the confined minimally invasive environment, new surgical tools may resemble small flexible snakes rather than rigid, cable driven instruments. Connecting to these developing articulated tools will significantly alter the overall kinematic structure of a robotic system. In this paper we present a technique for real-time automated generation and evaluation of manipulator kinematic equations that exhibits the combined advantages of existing methods-speed and flexibility to kinematic change--without their disadvantages.

  12. Off-shell Color-Kinematics Duality

    CERN Document Server

    Mastrolia, Pierpaolo; Schubert, Ulrich; Bobadilla, William J Torres

    2015-01-01

    We elaborate on the color-kinematics duality for off-shell diagrams in gauge theories coupled to matter, by investigating the scattering process $gg\\to ss, q\\bar q, gg$, and show that the Jacobi relations for the kinematic numerators of off-shell diagrams, built with Feynman rules in axial gauge, reduces to a color-kinematics violating term due to the contributions of sub-graphs only. Such anomaly vanishes when the four particles connected by the Jacobi relation are on their mass shell with vanishing squared momenta, being either external or cut particles, where the validity of the color-kinematics duality is recovered. We discuss the role of this off-shell decomposition in the direct construction of higher-multiplicity numerators satisfying color-kinematics identity, providing an explicit example for the QCD process $gg\\to q\\bar{q}g$.

  13. Tidal Dwarf Galaxies and Missing Baryons

    Directory of Open Access Journals (Sweden)

    Frederic Bournaud

    2010-01-01

    Full Text Available Tidal dwarf galaxies form during the interaction, collision, or merger of massive spiral galaxies. They can resemble “normal” dwarf galaxies in terms of mass, size, and become dwarf satellites orbiting around their massive progenitor. They nevertheless keep some signatures from their origin, making them interesting targets for cosmological studies. In particular, they should be free from dark matter from a spheroidal halo. Flat rotation curves and high dynamical masses may then indicate the presence of an unseen component, and constrain the properties of the “missing baryons,” known to exist but not directly observed. The number of dwarf galaxies in the Universe is another cosmological problem for which it is important to ascertain if tidal dwarf galaxies formed frequently at high redshift, when the merger rate was high, and many of them survived until today. In this paper, “dark matter” is used to refer to the nonbaryonic matter, mostly located in large dark halos, that is, CDM in the standard paradigm, and “missing baryons” or “dark baryons” is used to refer to the baryons known to exist but hardly observed at redshift zero, and are a baryonic dark component that is additional to “dark matter”.

  14. New cooling sequences for old white dwarfs

    CERN Document Server

    Renedo, Isabel; Bertolami, Marcelo M Miller; Romero, Alejandra D; Corsico, Alejandro H; Rohrmann, Rene D; Garcia-Berro, Enrique

    2010-01-01

    We present full evolutionary calculations appropriate for the study of hydrogen-rich DA white dwarfs. This is done by evolving white dwarf progenitors from the zero age main sequence, through the core hydrogen burning phase, the helium burning phase and the thermally pulsing asymptotic giant branch phase to the white dwarf stage. Complete evolutionary sequences are computed for a wide range of stellar masses and for two different metallicities: Z=0.01, which is representative of the solar neighborhood, and Z=0.001, which is appropriate for the study of old stellar systems, like globular clusters. During the white dwarf cooling stage we compute self-consistently the phase in which nuclear reactions are still important, the diffusive evolution of the elements in the outer layers and, finally, we also take into account all the relevant energy sources in the deep interior of the white dwarf, like the release of latent heat and the release of gravitational energy due to carbon-oxygen phase separation upon crystall...

  15. Water Clouds in Y Dwarfs and Exoplanets

    CERN Document Server

    Morley, Caroline V; Fortney, Jonathan J; Lupu, Roxana; Saumon, Didier; Greene, Tom; Lodders, Katharina

    2014-01-01

    The formation of clouds affects brown dwarf and planetary atmospheres of nearly all effective temperatures. Iron and silicate condense in L dwarf atmospheres and dissipate at the L/T transition. Minor species such as sulfides and salts condense in mid-late T dwarfs. For brown dwarfs below Teff=450 K, water condenses in the upper atmosphere to form ice clouds. Currently over a dozen objects in this temperature range have been discovered, and few previous theoretical studies have addressed the effect of water clouds on brown dwarf or exoplanetary spectra. Here we present a new grid of models that include the effect of water cloud opacity. We find that they become optically thick in objects below Teff=350-375 K. Unlike refractory cloud materials, water ice particles are significantly non-gray absorbers; they predominantly scatter at optical wavelengths through J band and absorb in the infrared with prominent features, the strongest of which is at 2.8 microns. H2O, NH3, CH4, and H2 CIA are dominant opacity source...

  16. The Observational Signature of Old White Dwarfs

    CERN Document Server

    Hansen, B M S

    1998-01-01

    The recent discovery of microlensing of stars in the Large Magellanic Cloud has excited much interest in the nature of the lensing population. Detailed analyses indicate that the mass of these objects ranges from 0.3-0.8 solar masses, suggesting that they might be white dwarfs, the faint remnants of stellar evolution. The confirmation of such an hypothesis would yield profound insights into the early history of our galaxy and the early generations of stars in the universe. Previous attempts have been made to place theoretical constraints on this scenario, but were unduly pessimistic because they relied on inadequate evolutionary models. Here we present the first results from detailed evolutionary models appropriate for the study of white dwarfs of truly cosmological vintage. We find that the commonly held notion that old white dwarfs are red to hold only for helium atmosphere dwarfs and that hydrogen atmosphere dwarfs will be blue, with colours similar to those of the faint point sources found in the Hubble D...

  17. Inclusive distributions near kinematic thresholds

    CERN Document Server

    Gardi, E

    2006-01-01

    The main challenge in computing inclusive cross sections and decay spectra in QCD is posed by kinematic thresholds. The threshold region is characterized by stringent phase-space constraints that are reflected in large perturbative corrections due to soft and collinear radiation as well as large non-perturbative effects. Major progress in addressing this problem was made in recent years by Dressed Gluon Exponentiation (DGE), a formalism that combines Sudakov and renormalon resummation in moment space. DGE has proven effective in extending the range of applicability of perturbation theory well into the threshold region and in identifying the relevant non-perturbative corrections. Here we review the method from a general perspective using examples from deep inelastic structure functions, event-shape distributions, heavy-quark fragmentation and inclusive decay spectra. A special discussion is devoted to the applications of DGE to radiative and semileptonic B decays that have proven valuable for the interpretatio...

  18. Bayesian kinematic earthquake source models

    Science.gov (United States)

    Minson, S. E.; Simons, M.; Beck, J. L.; Genrich, J. F.; Galetzka, J. E.; Chowdhury, F.; Owen, S. E.; Webb, F.; Comte, D.; Glass, B.; Leiva, C.; Ortega, F. H.

    2009-12-01

    Most coseismic, postseismic, and interseismic slip models are based on highly regularized optimizations which yield one solution which satisfies the data given a particular set of regularizing constraints. This regularization hampers our ability to answer basic questions such as whether seismic and aseismic slip overlap or instead rupture separate portions of the fault zone. We present a Bayesian methodology for generating kinematic earthquake source models with a focus on large subduction zone earthquakes. Unlike classical optimization approaches, Bayesian techniques sample the ensemble of all acceptable models presented as an a posteriori probability density function (PDF), and thus we can explore the entire solution space to determine, for example, which model parameters are well determined and which are not, or what is the likelihood that two slip distributions overlap in space. Bayesian sampling also has the advantage that all a priori knowledge of the source process can be used to mold the a posteriori ensemble of models. Although very powerful, Bayesian methods have up to now been of limited use in geophysical modeling because they are only computationally feasible for problems with a small number of free parameters due to what is called the "curse of dimensionality." However, our methodology can successfully sample solution spaces of many hundreds of parameters, which is sufficient to produce finite fault kinematic earthquake models. Our algorithm is a modification of the tempered Markov chain Monte Carlo (tempered MCMC or TMCMC) method. In our algorithm, we sample a "tempered" a posteriori PDF using many MCMC simulations running in parallel and evolutionary computation in which models which fit the data poorly are preferentially eliminated in favor of models which better predict the data. We present results for both synthetic test problems as well as for the 2007 Mw 7.8 Tocopilla, Chile earthquake, the latter of which is constrained by InSAR, local high

  19. MOA-2007-BLG-197: Exploring the brown dwarf desert

    CERN Document Server

    Ranc, C; Albrow, M D; Kubas, D; Bond, I A; Batista, V; Beaulieu, J -P; Bennett, D P; Dominik, M; Dong, Subo; Fouqué, P; Gould, A; Greenhill, J; Jørgensen, U G; Kains, N; Menzies, J; Sumi, T; Bachelet, E; Coutures, C; Dieters, S; Prester, D Dominis; Donatowicz, J; Gaudi, B S; Han, C; Hundertmark, M; Horne, K; Kane, S R; Lee, C -U; Marquette, J -B; Park, B -G; Pollard, K R; Sahu, K C; Street, R; Tsapras, Y; Wambsganss, J; Williams, A; Zub, M; Abe, F; Fukui, A; Itow, Y; Masuda, K; Matsubara, Y; Muraki, Y; Ohnishi, K; Rattenbury, N; Saito, To; Sullivan, D J; Sweatman, W L; Tristram, P J; Yock, P C M; Yonehara, A

    2015-01-01

    We present the analysis of MOA-2007-BLG-197Lb, the first brown dwarf companion to a Sun-like star detected through gravitational microlensing. The event was alerted and followed-up photometrically by a network of telescopes from the PLANET, MOA, and uFUN collaborations, and observed at high angular resolution using the NaCo instrument at the VLT. From the modelling of the microlensing light curve, we derived the binary lens separation in Einstein radius units (s~1.13) and a mass ratio of (4.732+/-0.020)x10^{-2}. Annual parallax, lens orbital motion and finite source effects were included in the models. To recover the lens system's physical parameters, we combined the resulting light curve best-fit parameters with (J,H,Ks) magnitudes obtained with VLT NaCo and calibrated using IRSF and 2MASS data. We derived a lens total mass of 0.86+/-0.04 Msun and a lens distance of 4.2+/-0.3 kpc. We find that the companion of MOA-2007-BLG-197L is a brown dwarf of 41+/-2 Mjup observed at a projected separation of 4.3+/-0.1 A...

  20. The unexpected diversity of dwarf galaxy rotation curves

    CERN Document Server

    Oman, Kyle A; Fattahi, Azadeh; Frenk, Carlos S; Sawala, Till; White, Simon D M; Bower, Richard; Crain, Robert A; Furlong, Michelle; Schaller, Matthieu; Schaye, Joop; Theuns, Tom

    2015-01-01

    We examine the circular velocity profiles of galaxies in {\\Lambda}CDM cosmological hydrodynamical simulations from the EAGLE and LOCAL GROUPS projects and compare them with a compilation of observed rotation curves of galaxies spanning a wide range in mass. The shape of the circular velocity profiles of simulated galaxies varies systematically as a function of galaxy mass, but shows remarkably little variation at fixed maximum circular velocity. This is especially true for low-mass dark matter-dominated systems, reflecting the expected similarity of the underlying cold dark matter haloes. This is at odds with observed dwarf galaxies, which show a large diversity of rotation curve shapes, even at fixed maximum rotation speed. Some dwarfs have rotation curves that agree well with simulations, others do not. The latter are systems where the inferred mass enclosed in the inner regions is much lower than expected for cold dark matter haloes and include many galaxies where previous work claims the presence of a con...

  1. Searching for benchmark systems containing ultra-cool dwarfs and white dwarfs

    Directory of Open Access Journals (Sweden)

    Pinfield D.J.

    2013-04-01

    Full Text Available We have used the 2MASS all-sky survey and WISE to look for ultracool dwarfs that are part of multiple systems containing main sequence stars. We cross-matched L dwarf candidates from the surveys with Hipparcos and Gliese stars, finding two new systems. We consider the binary fraction for L dwarfs and main sequence stars, and further assess possible unresolved multiplicity within the full companion sample. This analysis shows that some of the L dwarfs in this sample might actually be unresolved binaries themselves. We have also identified a sample of common proper motion systems in which a main sequence star has a white dwarf as wide companion. These systems can help explore key issues in star evolution theory, as the initial-final mass relationship of white dwarfs, or the chromospheric activity-age relationship for stars still in the main sequence. Spectroscopy for 50 white dwarf candidates, selected from the SuperCOSMOS Science Archive, was obtained. We have also observed 6 of the main sequence star companions, and have estimated their effective temperatures, rotational and microturbulent velocities and metallicities.

  2. Shaping the Brown Dwarf Desert: Predicting the Primordial Brown Dwarf Binary Distributions from Turbulent Fragmentation

    CERN Document Server

    Jumper, Peter H

    2013-01-01

    The formation of brown dwarfs (BDs) poses a key challenge to star formation theory. The observed dearth of nearby ($\\leq 5$ AU) brown dwarf companions to solar-mass stars, known as the brown dwarf desert, as well as the tendency for low-mass binary systems to be more tightly-bound than stellar binaries, have been cited as evidence for distinct formation mechanisms for brown dwarfs and stars. In this paper, we explore the implications of the minimal hypothesis that brown dwarfs in binary systems originate via the same fundamental fragmentation mechanism as stars, within isolated, turbulent giant molecular cloud cores. We demonstrate analytically that the scaling of specific angular momentum with turbulent core mass naturally gives rise to the brown dwarf desert, as well as wide brown-dwarf binary systems. Further, we demonstrate analytically that the turbulent core fragmentation model also naturally predicts that very low-mass (VLM) binary and BD/BD systems are more tightly-bound than stellar systems. In addit...

  3. An observer's guide to the (Local Group) dwarf galaxies: predictions for their own dwarf satellite populations

    CERN Document Server

    Dooley, Gregory A; Yang, Tianyi; Willman, Beth; Griffen, Brendan F; Frebel, Anna

    2016-01-01

    A recent surge in the discovery of new ultrafaint dwarf satellites of the Milky Way has inspired the idea of searching for faint satellites, $10^3\\, \\mathrm{M_{\\odot}}99\\%$ chance that at least one satellite with stellar mass $M_*> 10^5 \\, \\mathrm{M_{\\odot}}$ exists around the combined five Local Group field dwarf galaxies with the largest stellar mass. When considering satellites with $M_*> 10^4 \\, \\mathrm{M_{\\odot}}$, we predict a combined $5-25$ satellites for the five largest field dwarfs, and $10-50$ for the whole Local Group field dwarf population. Because of the relatively small number of predicted dwarfs, and their extended spatial distribution, a large fraction each Local Group dwarf's virial volume will need to be surveyed to guarantee discoveries. We compute the predicted number of satellites in a given field of view of specific Local Group galaxies, as a function of minimum satellite luminosity, and explicitly obtain such values for the Solitary Local dwarfs survey. Uncertainties in abundance matc...

  4. Infrared Photometry of Late-M, L, and T Dwarfs

    CERN Document Server

    Leggett, S K; Fan, X; Geballe, T R; Knapp, G R

    2002-01-01

    We present ZJHKL'M' photometry of a sample of 58 late-M, L, and T dwarfs, most of which are identified from the Sloan Digital Sky Survey and the Two Micron All-Sky Survey. Near-infrared spectra and spectral classifications for most of this sample are presented in a companion paper by Geballe et al. We derive the luminosities of 18 dwarfs in the sample and the results imply that the effective temperature range for the L dwarfs in our sample is approximately 2200-1300 K and for the T dwarfs 1300-800 K. We obtained new photometric data at the United Kingdom Infrared Telescope for: 42 dwarfs at Z, 34 dwarfs at JHK, 21 dwarfs at L', as well as M' data for two L dwarfs and two T dwarfs. The M' data provide the first accurate photometry for L and T dwarfs in this bandpass - for a T2 and a T5 dwarf, we find K-M'=1.2 and 1.6, respectively. These colors are much bluer than predicted by models suggesting that CO may be more abundant in these objects than expected, as has been found for the T6 dwarf Gl 229B. We also find...

  5. Virgo Early-Type Dwarfs in ALFALFA

    CERN Document Server

    Koopmann, Rebecca A

    2007-01-01

    Early-type dwarf galaxies dominate cluster populations, but their formation and evolutionary histories are poorly understood. The ALFALFA (Arecibo Legacy Fast ALFA) survey has completed observations of the Virgo Cluster in the declination range of 6 - 16 degrees. Less than 2% of the early-type dwarf population is detected, a significantly lower fraction than reported in previous papers based on more limited samples. In contrast ~30 of the irregular/BCD dwarf population is detected. The detected early-type galaxies tend to be located in the outer regions of the cluster, with a concentration in the direction of the M Cloud. Many show evidence for ongoing/recent star formation. Galaxies such as these may be undergoing morphological transition due to cluster environmental effects.

  6. Mystery of a Dimming White Dwarf

    Science.gov (United States)

    Kohler, Susanna

    2015-12-01

    In the wake of the recent media attention over an enigmatic, dimming star, another intriguing object has been discovered: J1529+2928, a white dwarf that periodically dims. This mystery, however, may have a simple solution with interesting consequences for future surveys of white dwarfs.Unexpected VariabilityJ1529+2928 is an isolated white dwarf that appears to have a mass of slightly more than the Sun. But rather than radiating steadily, J1529+2928 dims once every 38 minutes almost as though it were being eclipsed.The team that discovered these variations, led by Mukremin Kilic (University of Oklahoma), used telescopes at the Apache Point Observatory and the McDonald Observatory to obtain follow-up photometric data of J1529+2928 spread across 66 days. The team also took spectra of the white dwarf with the Gemini North telescope.Kilic and collaborators then began, one by one, to rule out possible causes of this objects variability.Eliminating OptionsThe period of the variability is too long for J1529+2928 to be a pulsating white dwarf with luminosity variation caused by gravity-wave pulsations.The variability cant be due to an eclipse by a stellar or brown-dwarf companion, because there isnt any variation in J1529+2928s radial velocity.Its not due to the orbit of a solid-body planetary object; such a transit would be too short to explain observations.It cant be due to the orbit of a disintegrated planet; this wouldnt explain the light curves observed in different filters plus the light curve doesnt change over the 66-day span.Spotty SurfaceTop and middle two panels: light curves from three different nights observing J1529+2928s periodic dimming. Bottom panel: The Fourier transform shows a peak at 37.7 cycles/day (and another, smaller peak at its first harmonic). [Kilic et al. 2015]So what explanation is left? The authors suggest that J1529+2928s variability is likely caused by a starspot on the white dwarfs surface that rotates into and out of our view. Estimates

  7. Charged Condensate and Helium Dwarf Stars

    CERN Document Server

    Gabadadze, Gregory

    2008-01-01

    White dwarf stars composed of carbon, oxygen or heavier elements are expected to crystallize as they cool down below certain temperatures. Yet, simple arguments suggest that the helium white dwarf cores may not solidify, mostly because of zero-point oscillations of the helium ions that would dissolve the crystalline structure. We argue that the interior of the helium dwarfs may instead form a macroscopic quantum state in which the charged helium-4 nuclei are in a Bose-Einstein condensate, while the relativistic electrons form a neutralizing degenerate Fermi liquid. We discuss the electric charge screening, and the spectrum of this substance, showing that the bosonic long-wavelength fluctuations exhibit a mass gap. Hence, there is a suppression at low temperatures of the boson contribution to the specific heat -- the latter being dominated by the specific heat of the electrons near the Fermi surface. This state of matter may have observational signatures.

  8. Towards understanding dynamo action in M dwarfs

    CERN Document Server

    Shulyak, D; Kitchatinov, L; Moss, D

    2015-01-01

    Recent progress in observational studies of magnetic activity in M dwarfs urgently requires support from ideas of stellar dynamo theory. We propose a strategy to connect observational and theoretical studies. In particular, we suggest four magnetic configurations that appear relevant to dwarfs from the viewpoint of the most conservative version of dynamo theory, and discuss observational tests to identify the configurations observationally. As expected, any such identification contains substantial uncertainties. However the situation in general looks less pessimistic than might be expected. Several identifications between the phenomenology of individual stars and dynamo models are suggested. Remarkably, all models discussed predict substantial surface magnetic activity at rather high stellar latitudes. This prediction looks unexpected from the viewpoint of our experience observing the Sun (which of course differs in some fundamental ways from these late-type dwarfs). We stress that a fuller understanding of t...

  9. Understanding dwarf galaxies as galactic building blocks

    CERN Document Server

    Tosi, M P

    2003-01-01

    This is a summary of a general discussion held during the third EuroConference on galaxy evolution. Various observational features of the stellar populations in present--day dwarf galaxies were presented to introduce the discussion on the possibility that these systems be the main building blocks of spiral and elliptical galaxies. Many people in the audience turned out to think that the inconsistencies among the observed properties of large and dwarf galaxies are too many to believe that the former are built up only by means of successive accretions of the latter. However, theorists of hierarchical galaxy formation suggested that present--day dwarfs are not representative of the galactic building blocks, which may be completely invisible nowadays. Some of them suggested that, contrary to what is usually assumed in hierarchical modelling, the actual building blocks were still fully gaseous systems when their major mergers occurred. If this is the case, then most of the inconsistencies can be overcome, and the ...

  10. A Nearby Survey of M-Dwarfs

    Science.gov (United States)

    Ray, Amy Elaine

    2017-01-01

    We present the results of a survey of 913 M-dwarf stars from the Lepine and Shara Proper Motion(LSPM) catalog within 25 parsecs of the Sun. Data for these targets was collected with the Robo-AO camera on the Palomar 60-in telescope. Separation and position angles were measured and compared for two epochs of the images, separated by two years, containing multiple stars to look for changes. We analyzed these positional data, combined with available 2MASS photometric data, to try to determine which stars are in gravitationally bound systems. This research was conducted measure the statistics of multiple M-dwarf systems within 25pc. Identifying and confirming higher ordered systems at both wide and small separations will help improve understanding of M-dwarf formation by comparing these results to star formation models.

  11. Hubble Space Telescope Studies of Exposed White Dwarfs in Dwarf Novae

    Science.gov (United States)

    Sion, Edward M.

    Coordinated AAVSO optical observations and Hubble Space Telescope (HST) far ultraviolet (UV) spectroscopic observations of cataclysmic variables, during dwarf nova quiescence when the underlying white dwarf is exposed in the far UV, have yielded a number of new insights into accretional heating, photospheric abundances of the accreted atmosphere, and rotational velocities of the underlying degenerates. Recent results of synthetic spectral analyses of HST spectra are highlighted. Their impact on our understanding of accretion physics and the effect of accretion on the white dwarf are discussed.

  12. A Panchromatic View of Brown Dwarf Aurorae

    Science.gov (United States)

    Pineda, J. Sebastian; Hallinan, Gregg; Kao, Melodie M.

    2017-09-01

    Stellar coronal activity has been shown to persist into the low-mass star regime, down to late M-dwarf spectral types. However, there is now an accumulation of evidence suggesting that at the end of the main sequence, there is a transition in the nature of the magnetic activity from chromospheric and coronal to planet-like and auroral, from local impulsive heating via flares and MHD wave dissipation to energy dissipation from strong large-scale magnetospheric current systems. We examine this transition and the prevalence of auroral activity in brown dwarfs through a compilation of multiwavelength surveys of magnetic activity, including radio, X-ray, and optical. We compile the results of those surveys and place their conclusions in the context of auroral emission as a consequence of large-scale magnetospheric current systems that accelerate energetic electron beams and drive the particles to impact the cool atmospheric gas. We explore the different manifestations of auroral phenomena, like Hα, in brown dwarf atmospheres and define their distinguishing characteristics. We conclude that large-amplitude photometric variability in the near-infrared is most likely a consequence of clouds in brown dwarf atmospheres, but that auroral activity may be responsible for long-lived stable surface features. We report a connection between auroral Hα emission and quiescent radio emission in electron cyclotron maser instability pulsing brown dwarfs, suggesting a potential underlying physical connection between quiescent and auroral emissions. We also discuss the electrodynamic engines powering brown dwarf aurorae and the possible role of satellites around these systems both to power the aurorae and seed the magnetosphere with plasma.

  13. Managing piezoelectric sensor jitter: kinematic position tracking applications

    Science.gov (United States)

    Khomo, Malome T.

    2016-02-01

    Piezo-acoustic distance tracking sensors have challenges of reporting true distance readings. Challenges include directional anisotropy signal loss in transmission power and in receiver sensitivity, distance-related attenuation of signal and the phase shifts that result in jittery values, some preceding, and others succeeding the expected distance readings. There also exist signal time losses arising from dead time associated with processor latency, with carrier signal pulse length and with voltage rise-time delays in pulse detection. Together these factors cause distance under-reporting, and more critically, makes each reported value uncertain, which is unacceptable in distance-critical applications. Piezo-inertial accelerometers have equivalent if not more severe challenges in tri-axial configurations, for instance where a rotational tilt may happen under linear accelerative force. In the absence of tensor component adaptation to change of orientation, signal is lost until the next axial sensor detects it. Study paper focusses on piezo-acoustic transducers UCD1007 and 400SR160 (40kHz), used in a face-to-face configuration over a 600mm range. Within that range 10 successive phase shift wave fronts were identified, but it took 15 reconstructed wave fronts to uniquely identify a continuous end-to-end jitter-free and slippage-free kinematic data stream from the jittery sensor data. The additional 5 degrees of freedom were consumed by the 5-stage filter applied. The technique has remarkable combinatorial and projective geometry implications for digital sensor design. It is possible for the procedure to be applicable in 3-axis accelerometers and adapted into firmware for truly kinematic device driver interfaces so long as the reporting rates are matched with the user interface refresh rates. It is shown that acoustic transducer sensors require phase loop locking for kinematic continuity whereas gravimetric accelerometers demand better measurement time consistence in

  14. Lumbar spine visualisation based on kinematic analysis from videofluoroscopic imaging.

    Science.gov (United States)

    Zheng, Y; Nixon, M S; Allen, R

    2003-04-01

    Low back pain is a significant problem and its cost is enormous to society. However, diagnosis of the underlying causes remains problematic despite extensive study. Reasons for this arise from the deep-rooted situation of the spine and also from its structural complexity. Clinicians have to mentally convert 2-D image information into a 3-D form to gain a better understanding of structural integrity. Therefore, visualisation and animation may be helpful for understanding, diagnosis and for guiding therapy. Some low back pain originates from mechanical disorders, and study of the spine kinematics may provide an insight into the source of the problem. Digital videofluoroscopy was used in this study to provide 2-D image sequences of the spine in motion, but the images often suffer due to noise, exacerbated by the very low radiation dosage. Thus determining vertebrae position within the image sequence presents a considerable challenge. This paper describes a combination of spine kinematic measurements with a solid model of the human lumbar spine for visualisation of spine motion. Since determination of the spine kinematics provides the foundation and vertebral extraction is at the core, this is discussed in detail. Edge detection is a key feature of segmentation and it is shown that phase congruency performs better than most established methods with the rather low-grade image sequences from fluoroscopy. The Hough transform is then applied to determine the positions of vertebrae in each frame of a motion sequence. In the Hough transform, Fourier descriptors are used to represent the vertebral shapes. The results show that the Hough transform is a very promising technique for vertebral extraction from videofluoroscopic images. A dynamic visualisation package has been developed in order to view the moving lumbar spine from any angle and viewpoint. Wire frame models of the vertebrae were built by using CT images from the Visible Human Project and these models are scaled to

  15. Magnetic White Dwarf Stars in the SDSS

    CERN Document Server

    Kepler, S O; Jordan, Stefan; Kleinman, Scot J; Kulebi, Baybars; Koester, Detlev; Peçanha, Viviane; Castanheira, Bárbara G; Nitta, Atsuko; Costa, José Eduardo da Silveira; Winget, Don Earl; Kanaan, Antonio; Fraga, Luciano

    2012-01-01

    To obtain a better statistics on the occurrence of magnetism among white dwarfs, we searched the spectra of the hydrogen atmosphere white dwarf stars (DAs) in the Data Release 7 of the Sloan Digital Sky Survey (SDSS) for Zeeman splittings and estimated the magnetic fields. We found 521 DAs with detectable Zeeman splittings, with fields in the range from around 1 MG to 733 MG, which amounts to 4% of all DAs observed. As the SDSS spectra have low signal-to-noise ratios, we carefully investigated by simulations with theoretical spectra how reliable our detection of magnetic field was.

  16. Pulsating White Dwarfs in Globular Clusters

    Science.gov (United States)

    Kanaan, A.; Zabot, A.; Fraga, L.

    2012-09-01

    We present our current efforts to detect pulsating white dwarfs in globular clusters and analyze the future of this area when the Extremely Large Telescope (ELT), the Giant Magellan Telescope (GMT) and the Thirty-Meter Telescope (TMT) all become operational. Today we are able to detect pulsating white dwarfs in M 4, NGC 6397 and NGC 6752. When ELT comes on line we should be able to improve the quality of data for the nearby clusters and push the limit to at least 3 magnitudes further, up to NGC 6626, increasing the number of observable clusters from 3 to 20.

  17. White Dwarf Pulsational Constraints on Stellar Evolution

    Science.gov (United States)

    Dunlap, Bart H.; Clemens, J. Christopher; O'Brien, Patrick C.; Hermes, J. J.; Fuchs, Joshua T.

    2017-01-01

    The complex processes that convert a protostellar cloud into a carbon/oxygen-core white dwarf star are distilled and modeled in state of the art stellar evolution codes. Many of these processes are well-constrained, but several are uncertain or must be parameterized in the models because a complete treatment would be computationally prohibitive—turbulent motions such as convective overshoot cannot, for example, be modeled in 1D. Various free parameters in the models must therefore be calibrated. We will discuss how white dwarf pulsations can inform such calibrations. The results of all prior evolution are cemented into the interiors of white dwarf stars and, so, hidden from view. However, during certain phases of their cooling, pulsations translate the star's evolutionary history into observable surface phenomena. Because the periods of a pulsating white dwarf star depend on an internal structure assembled as it evolved to its final state, white dwarf pulsation periods can be viewed as observable endpoints of stellar evolution. For example, the thickness of the helium layer in a white dwarf directly affects its pulsations; the observed periods are, therefore, a function of the number of thermal pulses during which the star converts helium into core material on the asymptotic giant branch. Because they are also a function of several other significant evolutionary processes, several pulsation modes are necessary to tease all of these apart. Unfortunately, white dwarf pulsators typically do not display enough oscillation modes to constrain stellar evolution. To avoid this limitation, we consider the pulsations of the entire collection of hot pulsating hydrogen-atmosphere white dwarf stars (DAVs). Though any one star may not have sufficient information to place interesting constraints on its evolutionary history, taken together, the stars show a pattern of modes that allows us to test evolutionary models. For an example set of published evolutionary models, we show a

  18. The Onset of Methane in L Dwarfs

    CERN Document Server

    Noll, K S; Leggett, S K; Marley, M S; Noll, Keith S.; Marley, Mark S.

    2000-01-01

    We have detected weak absorption features produced by the strong nu(3) methane band at 3.3 microns in two L dwarfs, 2MASSW J1507476-162738 and 2MASSI J0825196+211552, classified by Kirkpatrick et al. (2000) as spectral types L5 and L7.5 respectively. These absorptions occur in objects warmer than any in which methane previously has been detected, and mark the first appearance of methane in the ultracool star-to-brown dwarf spectral sequence.

  19. Are disappearing dwarfs just lying low ?

    CERN Document Server

    Phillipps, S; Phillipps, Steven; Driver, Simon P

    1995-01-01

    Recent redshift surveys have shown that the excess galaxies seen in faint galaxy number counts (above those expected given the local galaxy luminosity function) are not evolved giants at high redshifts, but low to moderate luminosity objects at more modest redshifts. This has led to the suggestion that there was once an additional population of dwarf galaxies which has since disappeared, ie. there is non-conservation of galaxy number. Here we investigate the possibility that these disappearing dwarfs have actually evolved to become the population of very low surface brightness galaxies which is now being detected in nearby clusters.

  20. Isolated patellofemoral arthroplasty reproduces natural patellofemoral joint kinematics when the patella is resurfaced.

    Science.gov (United States)

    Vandenneucker, Hilde; Labey, Luc; Vander Sloten, Jos; Desloovere, Kaat; Bellemans, Johan

    2016-11-01

    The objectives of this in vitro project were to compare the dynamic three-dimensional patellofemoral kinematics, contact forces, contact areas and contact pressures of a contemporary patellofemoral prosthetic implant with those of the native knee and to measure the influence of patellar resurfacing and patellar thickness. The hypothesis was that these designs are capable to reproduce the natural kinematics but result in higher contact pressures. Six fresh-frozen specimens were tested on a custom-made mechanical knee rig before and after prosthetic trochlear resurfacing, without and with patellar resurfacing in three different patellar thicknesses. Full three-dimensional kinematics were analysed during three different motor tasks, using infrared motion capture cameras and retroflective markers. Patellar contact characteristics were registered using a pressure measuring device. The patellofemoral kinematic behaviour of the patellofemoral arthroplasty was similar to that of the normal knee when the patella was resurfaced, showing only significant (p patella was resurfaced. From a kinematic point of view, patellar resurfacing may be advisable. However, the substantially elevated patellar contact pressures remain a point of concern in the decision whether or not to resurface the patella. This study therefore not only adds a new point in the discussion whether or not to resurface the patella, but also supports the claimed advantage that a patellofemoral arthroplasty is capable to reproduce the natural knee kinematics.

  1. Inverse Kinematics With Closed Form Solution For Denso Robot Manipulator

    Directory of Open Access Journals (Sweden)

    Ikhsan Eka Prasetia

    2015-03-01

    Full Text Available In this paper, the forward kinematics and inverse kinematics used on the Denso robot manipulator which has a 6-DOF. The forward kinematics will result in the desired position by end-effector, while inverse kinematics produce angel on each joint. Inverse kinematics problem are very difficult, therefor to obtain the solution of inverse kinematics using closed form solution with geometry approach. The simulation result obtained from forward kinematics and inverse kinematics is determining desired position by Denso robot manipulator. Forward kinematics produce the desired position by the end-effector. Inverse kinematics produce joint angle, where the inverse kinematics produce eight conditions obtained from closed form solution with geometry approach to reach the desired position by the end-effector.

  2. The DODO survey - II. A Gemini direct imaging search for substellar and planetary mass companions around nearby equatorial and Northern hemisphere white dwarfs

    Science.gov (United States)

    Hogan, E.; Burleigh, M. R.; Clarke, F. J.

    2009-07-01

    The aim of the Degenerate Objects around Degenerate Objects (DODO) survey is to search for very low-mass brown dwarfs and extrasolar planets in wide orbits around white dwarfs via direct imaging. The direct detection of such companions would allow the spectroscopic investigation of objects with temperatures much lower (T8.5, and so could belong to the proposed Y dwarf spectral sequence. The detection of a planet around a white dwarf would prove that such objects can survive the final stages of stellar evolution and place constraints on the frequency of planetary systems around their progenitors (with masses between 1.5 and 8Msolar, i.e. early B to mid-F). This paper presents the results of a multi epoch J band common proper motion survey of 23 nearby equatorial and Northern hemisphere white dwarfs. We rule out the presence of any common proper motion companions, with limiting masses determined from the completeness limit of each observation, to 18 white dwarfs. For the remaining five targets, the motion of the white dwarf is not sufficiently separated from the non-moving background objects in each field. These targets require additional observations to conclusively rule out the presence of any common proper motion companions. From our completeness limits, we tentatively suggest that ~ 500 K between projected physical separations of 60-200 au.

  3. DIRECT SPECTRUM OF THE BENCHMARK T DWARF HD 19467 B

    Energy Technology Data Exchange (ETDEWEB)

    Crepp, Justin R.; Matthews, Christopher T. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Rice, Emily L.; Giorla, Paige [College of Staten Island, CUNY, 2800 Victory Boulevard, Staten Island, NY 10314 (United States); Veicht, AAron; Nilsson, Ricky; Luszcz-Cook, Statia H.; Oppenheimer, Rebecca; Brenner, Douglas [American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024 (United States); Aguilar, Jonathan; Pueyo, Laurent; Sivaramakrishnan, Anand; Soummer, Remi [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Hinkley, Sasha; Hillenbrand, Lynne A. [Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Vasisht, Gautam; Cady, Eric; Lockhart, Thomas; Roberts, Lewis C. Jr. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Beichman, Charles A., E-mail: jcrepp@nd.edu [NASA Exoplanet Science Institute, California Institute of Technology, Pasadena, CA 91125 (United States); and others

    2015-01-10

    HD 19467 B is presently the only directly imaged T dwarf companion known to induce a measurable Doppler acceleration around a solar-type star. We present spectroscopy measurements of this important benchmark object taken with the Project 1640 integral field unit at Palomar Observatory. Our high-contrast R ≈ 30 observations obtained simultaneously across the JH bands confirm the cold nature of the companion as reported from the discovery article and determine its spectral type for the first time. Fitting the measured spectral energy distribution to SpeX/IRTF T dwarf standards and synthetic spectra from BT-Settl atmospheric models, we find that HD 19467 B is a T5.5 ± 1 dwarf with effective temperature T{sub eff}=978{sub −43}{sup +20} K. Our observations reveal significant methane absorption affirming its substellar nature. HD 19467 B shows promise to become the first T dwarf that simultaneously reveals its mass, age, and metallicity independent from the spectrum of light that it emits.

  4. Self-consistent photometric and spectroscopic Star Formation Histories in Dwarf Galaxies

    Science.gov (United States)

    García-Benito, R.; Pérez, E.; Pérez-Montero, E.; González Delgado, R.; Vílchez, J. M.

    2016-06-01

    This project aims to unify the spectroscopic and stellar photometric views by performing a comprehensive study of a sample of the nearest Blue Compact Dwarf Galaxies (BCDs). We plan to derive Star Formation Histories (SFH) both by means of Color-Magnitude Diagrams (CMDs) from extant Hubble Space Telescope (HST) optical imaging and with spectral fitting methods techniques using MUSE, allowing us to obtain state-of-the-art 2D stellar properties and abundances of the gas in BCDs.

  5. Anisotropic superconductivity driven by kinematic interaction

    Science.gov (United States)

    Ivanov, V. A.

    2000-11-01

    We have analysed the effect of kinematic pairing on the symmetry of superconducting order parameter for a square lattice in the frame of the strongly correlated Hubbard model. It is argued that in the first perturbation order the kinematic interaction renormalizes the Hubbard-I dispersions and provides at low doping the mixed singlet (s + s*)-wave superconductivity, giving way at higher doping to the triplet p-wave superconductivity. The obtained phase diagram depends only on the hopping integral parameter. The influence of the Coulomb repulsion on the kinematic superconducting pairing has been estimated. The (s + s*)-wave gap and the thermodynamic critical magnetic field have been derived.

  6. Dark Matter in $\\gamma$ lines: Galactic Center vs dwarf galaxies

    CERN Document Server

    Lefranc, Valentin; Panci, Paolo; Sala, Filippo; Silk, Joseph

    2016-01-01

    We provide CTA sensitivities to Dark Matter (DM) annihilation in $\\gamma$-ray lines, from the observation of the Galactic Center (GC) as well as, for the first time, of dwarf Spheroidal galaxies (dSphs). We compare the GC reach with that of dSphs as a function of a putative core radius of the DM distribution, which is itself poorly known. We find that the currently best dSph candidates constitute a more promising target than the GC, for core radii of one to a few kpc. We use the most recent instrument response functions and background estimations by CTA, on top of which we add the diffuse photon component. Our analysis is of particular interest for TeV-scale electroweak multiplets as DM candidates, such as the supersymmetric Wino and the Minimal Dark Matter fiveplet, whose predictions we compare with our projected sensitivities.

  7. TIDAL STIRRING OF DISKY DWARFS WITH SHALLOW DARK MATTER DENSITY PROFILES: ENHANCED TRANSFORMATION INTO DWARF SPHEROIDALS

    Energy Technology Data Exchange (ETDEWEB)

    Kazantzidis, Stelios [Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States); Lokas, Ewa L. [Nicolaus Copernicus Astronomical Center, 00-716 Warsaw (Poland); Mayer, Lucio, E-mail: stelios@mps.ohio-state.edu [Institute for Theoretical Physics, University of Zuerich, CH-8057 Zuerich (Switzerland)

    2013-02-20

    According to the tidal stirring model, late type, rotationally supported dwarfs resembling present day dwarf irregular (dIrr) galaxies can transform into dwarf spheroidals (dSphs) via interactions with Milky-Way-sized hosts. We perform collisionless N-body simulations to investigate for the first time how tidal stirring depends on the dark matter (DM) density distribution in the central stellar region of the progenitor disky dwarf. Specifically, we explore various asymptotic inner slopes {gamma} of the dwarf DM density profiles ({rho}{proportional_to}r {sup -{gamma}}). For a given orbit inside the primary galaxy, rotationally supported dwarfs embedded in DM halos with core-like distributions ({gamma} = 0.2) and mild density cusps ({gamma} = 0.6) demonstrate a substantially enhanced likelihood and efficiency of transformation into dSphs compared to their counterparts with steeper DM density profiles ({gamma} = 1). Such shallow DM distributions are akin to those of observed dIrrs highlighting tidal stirring as a plausible model for the Local Group (LG) morphology-density relation. When {gamma} < 1, a single pericentric passage can induce dSph formation and disky dwarfs on low-eccentricity or large-pericenter orbits are able to transform; these new results allow tidal stirring to explain virtually all known dSphs across a wide range of distances from their hosts. A subset of disky dwarfs initially embedded in DM halos with shallow density profiles are eventually disrupted by the primary; those that survive as dSphs are generally on orbits with lower eccentricities and/or larger pericenters compared to those of typical cold dark matter satellites. The latter could explain the peculiar orbits of several LG dSphs such as Fornax, Leo I, Tucana, and Cetus.

  8. Kinematic alignment of non-interacting CALIFA galaxies: Quantifying the impact of bars on stellar and ionised gas velocity field orientations

    CERN Document Server

    Barrera-Ballesteros, J K; García-Lorenzo, B; van de Ven, G; Aguerri, J A L; Mendez-Abreu, J; Spekkens, K; Sánchez, S F; Husemann, B; Mast, D; García-Benito, R; Iglesias-Paramo, J; del Olmo, A; Márquez, I; Masegosa, J; Kehrig, C; Marino, R A; Verdes-Montenegro, L; Ziegler, B; MacIntosh, D H; Bland-Hawthorn, J; Walcher, C J

    2014-01-01

    We present 80 stellar and ionised gas velocity maps from the Calar Alto Legacy Integral Field Area (CALIFA) survey in order to characterize the kinematic orientation of non-interacting galaxies. The study of galaxies in isolation is a key step towards understanding how fast-external processes, such as major mergers, affect kinematic properties in galaxies. We derived the global and individual (projected approaching and receding sides) kinematic position angles (PAs) for both the stellar and ionised gas line-of-sight velocity distributions. When compared to the photometric PA, we find that morpho-kinematic differences are smaller than 22 degrees in 90% of the sample for both components; internal kinematic misalignments are generally smaller than 16 degrees. We find a tight relation between the global stellar and ionised gas kinematic PA consistent with circular-flow pattern motions in both components. This relation also holds generally in barred galaxies across the bar and galaxy disk scales. Our findings sugg...

  9. The effect of gravitational tides on dwarf spheroidal galaxies

    CERN Document Server

    Nichols, Matthew; Jablonka, Pascale

    2014-01-01

    The effect of the local environment on the evolution of dwarf spheroidal galaxies is poorly understood. We have undertaken a suite of simulations to investigate the tidal impact of the Milky Way on the chemodynamical evolution of dwarf spheroidals that resemble present day classical dwarfs using the SPH code GEAR. After simulating the models through a large parameter space of potential orbits the resulting properties are compared with observations from both a dynamical point of view, but also from the, often neglected, chemical point of view. In general, we find that tidal effects quench the star formation even inside gas-endowed dwarfs. Such quenching, may produce the radial distribution of dwarf spheroidals from the orbits seen within large cosmological simulations. We also find that the metallicity gradient within a dwarf is gradually erased through tidal interactions as stellar orbits move to higher radii. The model dwarfs also shift to higher $\\langle$[Fe/H]$\\rangle$/L ratios, but only when losing $>$$20...

  10. Kinematics of the Hercules Supercluster

    CERN Document Server

    Barmby, P; Barmby, Pauline; Huchra, John P.

    1997-01-01

    The Hercules Supercluster consists of the Abell clusters 2147, 2151, and 2152. Previous studies of the kinematics have been confounded by the difficulty of correctly assigning galaxies to the individual clusters, which are not well-separated. Our study has a total of 468 available velocities for galaxies in the region, 175 of them new. 414 galaxies are in the supercluster, about three times the number used in the previous supercluster study. We verify the existence of the three individual clusters and compute their individual dynamical parameters. We investigate several techniques for assigning galaxy membership to clusters in this crowded field. We use the KMM mixture-modeling algorithm to separate the galaxies into clusters; we find that A2152 has a higher mean velocity than previous studies have reported. A2147 and A2152 also have lower velocity dispersions: 821(+68)(-55) and 715(+81)(-61) km/s. The assignment of galaxies to either A2152 or A2147 requires velocity and position information. We study the kin...

  11. Edge-driven microplate kinematics

    Science.gov (United States)

    Schouten, Hans; Klitgord, Kim D.; Gallo, David G.

    1993-01-01

    It is known from plate tectonic reconstructions that oceanic microplates undergo rapid rotation about a vertical axis and that the instantaneous rotation axes describing the microplate's motion relative to the bounding major plates are frequently located close to its margins with those plates, close to the tips of propagating rifts. We propose a class of edge-driven block models to illustrate how slip across the microplate margins, block rotation, and propagation of rifting may be related to the relative motion of the plates on either side. An important feature of these edge-driven models is that the instantaneous rotation axes are always located on the margins between block and two bounding plates. According to those models the pseudofaults or traces of disrupted seafloor resulting from the propagation of rifting between microplate and major plates may be used independently to approximately trace the continuous kinematic evolution of the microplate back in time. Pseudofault geometries and matching rotations of the Easter microplate show that for most of its 5 m.y. history, block rotation could be driven by the drag of the Nazca and Pacific plates on the microplate's edges rather than by a shear flow of mantle underneath.

  12. Dark matter annihilation and decay profiles for the Reticulum II dwarf spheroidal galaxy

    CERN Document Server

    Bonnivard, V; Maurin, D; Geringer-Sameth, A; Koushiappas, S M; Walker, M G; Mateo, M; Olszewski, E; Bailey, J I

    2015-01-01

    The dwarf spheroidal galaxies (dSph) of the Milky Way are among the most attractive targets for indirect searches of dark matter. In this work, we reconstruct the dark matter annihilation (J-factor) and decay profiles for the newly discovered dSph Reticulum~II. This is done using an optimized spherical Jeans analysis of kinematic data obtained from the Michigan/Magellan Fiber System (M2FS). We find Reticulum~II to have one of the highest J-factor when compared to the other Milky Way dSphs. We have also checked the robustness of this result against several ingredients of the analysis. Unless it suffers from tidal disruption or significant inflation of its velocity dispersion from binary stars, Reticulum~II may provide a unique window on dark matter particle properties.

  13. Dark Matter Annihilation and Decay Profiles for the Reticulum II Dwarf Spheroidal Galaxy

    Science.gov (United States)

    Bonnivard, Vincent; Combet, Céline; Maurin, David; Geringer-Sameth, Alex; Koushiappas, Savvas M.; Walker, Matthew G.; Mateo, Mario; Olszewski, Edward W.; Bailey, John I., III

    2015-08-01

    The dwarf spheroidal galaxies (dSph) of the Milky Way are among the most attractive targets for indirect searches of dark matter (DM). In this work, we reconstruct the DM annihilation (J-factor) and decay profiles for the newly discovered dSph Reticulum II. Using an optimized spherical Jeans analysis of kinematic data obtained from the Michigan/Magellan Fiber System, we find Reticulum II’s J-factor to be among the largest of any Milky Way dSph. We have checked the robustness of this result against several ingredients of the analysis. Unless it suffers from tidal disruption or significant inflation of its velocity dispersion from binary stars, Reticulum II may provide a unique window on DM particle properties.

  14. M-dwarf binaries as tracers of star and brown dwarf formation

    CERN Document Server

    Marks, Michael; Kroupa, Pavel; Leigh, Nathan; Thies, Ingo

    2015-01-01

    The separation distribution for M-dwarf binaries in the ASTRALUX survey is narrower and peaking at smaller separations than the distribution for solar-type binaries. This is often interpreted to mean that M-dwarfs constitute a continuous transition from brown dwarfs (BDs) to stars. Here a prediction for the M-dwarf separation distribution is presented, using a dynamical population synthesis (DPS) model in which "star-like" binaries with late-type primaries ($\\lesssim1.5 M_{\\rm sun}$) follow universal initial distribution functions and are dynamically processed in their birth embedded clusters. A separate "BD-like" population has both its own distribution functions for binaries and initial mass function (IMF), which overlaps in mass with the IMF for stars. Combining these two formation modes results in a peak on top of a wider separation distribution for late M-dwarfs consistent with the late ASTRALUX sample. The DPS separation distribution for early M-dwarfs shows no such peak and is in agreement with the M-d...

  15. The White Dwarf Binary Pathways Survey I: A sample of FGK stars with white dwarf companions

    CERN Document Server

    Parsons, S G; Schreiber, M R; Gansicke, B T; Zorotovic, M; Ren, J J

    2016-01-01

    The number of white dwarf plus main-sequence star binaries has increased rapidly in the last decade, jumping from only ~30 in 2003 to over 3000. However, in the majority of known systems the companion to the white dwarf is a low mass M dwarf, since these are relatively easy to identify from optical colours and spectra. White dwarfs with more massive FGK type companions have remained elusive due to the large difference in optical brightness between the two stars. In this paper we identify 934 main-sequence FGK stars from the Radial Velocity Experiment (RAVE) survey in the southern hemisphere and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey in the northern hemisphere, that show excess flux at ultraviolet wavelengths which we interpret as the likely presence of a white dwarf companion. We obtained Hubble Space Telescope ultraviolet spectra for nine systems which confirmed that the excess is indeed caused, in all cases, by a hot compact companion, eight being white dwarfs and one ...

  16. Star formation history in forming dwarf galaxies

    Science.gov (United States)

    Berczik, P.; Kravchuk, S. G.

    The processes of formation and evolution of isolated dwarf galaxies over the Hubble timescale is followed by means of SPH techniques. As an initial protogalaxy perturbation we consider an isolated, uniform, solid -- body rotated sphere involved into the Hubble flow and made of dark and baryonic matter in a 10:1 ratio. The simulations are carried out for the set of models having spin parameters lambda in the range from 0.01 to 0.08 and the total mass of dark matter 1011 M_odot . Our model includes gasdynamics, radiative processes, star formation, supernova feedback and simplified chemistry. The application of modified star formation criterion which accounts for chaotic motions and the time lag between initial development of suitable conditions for star formation and star formation itself (Berczik P.P, Kravchuk S.G. 1997, Ap.Sp.Sci.) provides the realistic description of the process of galaxy formation and evolution. Two parameters: total mass and initial angular momentum of the dwarf protogalaxy play the crucial role in its star formation activity. After the 15 Gyr of the evolution the rapidly rotated dwarf galaxies manifest themselves as an extremly gasrich, heavy element deficient objects showing the initial burst of star formation activity in several spatially separated regions. Slowly rotating objects manifest themselves finally as typical evolved dwarf galaxies.

  17. DA white dwarfs in the Kepler field

    Science.gov (United States)

    Doyle, T. F.; Howell, S. B.; Petit, V.; Lépine, S.

    2017-01-01

    We present 16 new, and confirm 7 previously identified, DA white dwarfs in the Kepler field through ground-based spectroscopy with the Hale 200″, Kitt Peak 4-m, and Bok 2.3-m telescopes. Using atmospheric models, we determine their effective temperatures and surface gravities to constrain their position with respect to the ZZ Ceti (DA pulsator) instability strip, and look for the presence or absence of pulsation with Kepler's unprecedented photometry. Our results are as follows. (i) From our measurements of temperature and surface gravity, 12 of the 23 DA white dwarfs from this work fall well outside of the instability strip. The Kepler photometry available for 11 of these WDs allows us to confirm that none are pulsating. One of these 11 happens to be a presumed binary, KIC 11604781, with a period of ˜5 d. (ii) The remaining 11 DA white dwarfs are instability strip candidates, potentially falling within the current, empirical instability strip, after accounting for uncertainties. These WDs will help constrain the strip's location further, as eight are near the blue edge and three are near the red edge of the instability strip. Four of these WDs do not have Kepler photometry, so ground-based photometry is needed to determine the pulsation nature of these white dwarfs. The remaining seven have Kepler photometry available, but do not show any periodicity on typical WD pulsation time-scales.

  18. A dominant semi dwarf mutant in rice

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    @@ In the winter of 1997, a semi dwarf mutant was found in the F6 population of M9056/ R8018 xuan in Hainan Province. In the spring of 1998, the seeds were sown in Hefei, Anhui Province and the plant height of the population was measured at maturity.

  19. The "Living with a Red Dwarf" Program

    CERN Document Server

    Guinan, Edward F

    2009-01-01

    Red Dwarfs (main-sequence / dwarf M or dM) stars are the most common stars in the Galaxy. These cool, faint, low mass stars comprise over 75% of all stars. Because of their low luminosities (~0.0008-0.06 of the Sun's luminosity), the circumstellar habitable zones (HZs) of dM stars are located within ~0.05-0.4 AU of the host star. Nevertheless, the prospect of life on a planet located within the HZ of a red dwarf is moderately high, based on the longevity of these stars (>50 Gyr), their constant luminosities and high space densities. Here we describe the aims and early results of the "Living with a Red Dwarf" Program - a study of dM stars that we have been carrying out over the last few years. The primary focus of our research on dM stars is the study of their magnetic dynamos and resulting star spots & coronal X-ray and chromospheric UV emissions as a function of age, rotation and spectral type. This program will provide datasets that can be used as inputs for the study of all aspects of dM stars, along w...

  20. Magnetic white dwarfs with debris discs

    CERN Document Server

    Külebi, Baybars; Lorén-Aguilar, Pablo; Isern, Jordi; García-Berro, Enrique

    2013-01-01

    It has long been accepted that a possible mechanism for explaining the existence of magnetic white dwarfs is the merger of a binary white dwarf system, as there are viable mechanisms for producing sustainable magnetic fields within the merger product. However, the lack of rapid rotators in the magnetic white dwarf population has been always considered a problematic issue of this scenario. Smoothed Particle Hydrodynamics simulations show that in mergers in which the two white dwarfs have different masses a disc around the central compact object is formed. If the central object is magnetized it can interact with the disc through its magnetosphere. The torque applied by the disc changes the spin of the star, whereas the transferred angular momentum from the star to the disc determines the properties of the disc. In this work we build a model for the disc evolution under the effect of magnetic accretion, and for the angular momentum evolution of the star, which can be compared with the observations. Our model pre...

  1. The 25 parsec local white dwarf population

    Science.gov (United States)

    Holberg, J. B.; Oswalt, T. D.; Sion, E. M.; McCook, G. P.

    2016-11-01

    We have extended our detailed survey of the local white dwarf population from 20 to 25 pc, effectively doubling the sample volume, which now includes 232 stars. In the process, new stars within 20 pc have been added, a more uniform set of distance estimates as well as improved spectral and binary classifications are available. The present 25 pc sample is estimated to be about 68 per cent complete (the corresponding 20 pc sample is now 86 per cent complete). The space density of white dwarfs is unchanged at 4.8 ± 0.5 × 10-3 pc-3. This new study includes a white dwarf mass distribution and luminosity function based on the 232 stars in the 25 pc sample. We find a significant excess of single stars over systems containing one or more companions (74 per cent versus 26 per cent). This suggests mechanisms that result in the loss of companions during binary system evolution. In addition, this updated sample exhibits a pronounced deficiency of nearby `Sirius-like' systems. 11 such systems were found within the 20 pc volume versus only one additional system found in the volume between 20 and 25 pc. An estimate of white dwarf birth rates during the last ˜8 Gyr is derived from individual remnant cooling ages. A discussion of likely ways new members of the local sample may be found is provided.

  2. The surprising inefficiency of dwarf satellite quenching

    CERN Document Server

    Wheeler, Coral; Cooper, Michael C; Boylan-Kolchin, Mike; Bullock, James S

    2014-01-01

    We study dwarf satellite galaxy quenching using observations from the Geha et al. (2012) NSA/SDSS catalog together with LCDM cosmological simulations to facilitate selection and interpretation. We show that fewer than 30% of dwarfs (M* ~ 10^8.5-10^9.5 Msun) identified as satellites within massive host halos (Mhost ~ 10^12.5-10^14 Msun) are quenched, in spite of the expectation from simulations that half of them should have been accreted more than 6 Gyr ago. We conclude that whatever the action triggering environmental quenching of dwarf satellites, the process must be highly inefficient. We investigate a series of simple, one-parameter quenching models in order understand what is required to explain the low quenched fraction and conclude that either the quenching timescale is very long (> 9.5 Gyr, a "slow starvation" scenario) or that the environmental trigger is not well matched to accretion within the virial volume. We discuss these results in light of the fact that most of the low mass dwarf satellites in ...

  3. Differential rotation on early G dwarfs

    NARCIS (Netherlands)

    Jeffers, S.V.; Donati, J.F.

    2007-01-01

    In this paper we present the latest results in our long-term program to understand how differential rotation depends on fundamental stellar parameters such as spectral type, mass and radius. In this paper we focus on early G dwarf spectral types by presenting our latest surface brightness image and

  4. Blue straggler stars in dwarf spheroidal galaxies

    NARCIS (Netherlands)

    Mapelli, M.; Ripamonti, E.; Tolstoy, E.; Sigurdsson, S.; Irwin, M. J.; Battaglia, G.

    2007-01-01

    Blue straggler star (BSS) candidates have been observed in all old dwarf spheroidal galaxies (dSphs), however whether or not they are authentic BSSs or young stars has been a point of debate. To both address this issue and obtain a better understanding of the formation of BSSs in different environme

  5. 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

  6. On The Evolution of Magnetic White Dwarfs

    CERN Document Server

    Tremblay, P -E; Freytag, B; Steiner, O; Ludwig, H -G; Steffen, M; Wedemeyer, S; Brassard, P

    2015-01-01

    We present the first radiation magnetohydrodynamics simulations of the atmosphere of white dwarf stars. We demonstrate that convective energy transfer is seriously impeded by magnetic fields when the plasma-beta parameter, the thermal to magnetic pressure ratio, becomes smaller than unity. The critical field strength that inhibits convection in the photosphere of white dwarfs is in the range B = 1-50 kG, which is much smaller than the typical 1-1000 MG field strengths observed in magnetic white dwarfs, implying that these objects have radiative atmospheres. We have then employed evolutionary models to study the cooling process of high-field magnetic white dwarfs, where convection is entirely suppressed during the full evolution (B > 10 MG). We find that the inhibition of convection has no effect on cooling rates until the effective temperature (Teff) reaches a value of around 5500 K. In this regime, the standard convective sequences start to deviate from the ones without convection owing to the convective cou...

  7. Massive Star Clusters in Dwarf Galaxies

    CERN Document Server

    Larsen, Soeren S

    2015-01-01

    Dwarf galaxies can have very high globular cluster specific frequencies, and the GCs are in general significantly more metal-poor than the bulk of the field stars. In some dwarfs, such as Fornax, WLM, and IKN, the fraction of metal-poor stars that belong to GCs can be as high as 20%-25%, an order of magnitude higher than the 1%-2% typical of GCs in halos of larger galaxies. Given that chemical abundance anomalies appear to be present also in GCs in dwarf galaxies, this implies severe difficulties for self-enrichment scenarios that require GCs to have lost a large fraction of their initial masses. More generally, the number of metal-poor field stars in these galaxies is today less than what would originally have been present in the form of low-mass clusters if the initial cluster mass function was a power-law extending down to low masses. This may imply that the initial GC mass function in these dwarf galaxies was significantly more top-heavy than typically observed in present-day star forming environments.

  8. Evolution of dwarf galaxies : A dynamical perspective

    NARCIS (Netherlands)

    Lelli, Federico; Fraternali, Filippo; Verheijen, Marc

    2014-01-01

    For a rotating galaxy, the inner circular-velocity gradient dRV(0) provides a direct estimate of the central dynamical mass density, including gas, stars, and dark matter. We consider 60 low-mass galaxies with high-quality H I and/or stellar rotation curves (including starbursting dwarfs, irregulars

  9. Evolution of dwarf galaxies: a dynamical perspective

    NARCIS (Netherlands)

    Lelli, Federico; Fraternali, Filippo; Verheijen, Marc

    2014-01-01

    For a rotating galaxy, the inner circular-velocity gradient dRV(0) provides a direct estimate of the central dynamical mass density, including gas, stars, and dark matter. We consider 60 low-mass galaxies with high-quality H I and/or stellar rotation curves (including starbursting dwarfs, irregulars

  10. DA White Dwarfs in the Kepler Field

    Science.gov (United States)

    Doyle, T. F.; Howell, S. B.; Petit, V.; Lépine, S.

    2016-10-01

    We present 16 new, and confirm 7 previously identified, DA white dwarfs in the Kepler field through ground-based spectroscopy with the Hale 200″, Kitt Peak 4-meter, and Bok 2.3-meter telescopes. Using atmospheric models we determine their effective temperatures and surface gravities to constrain their position with respect to the ZZ Ceti (DA pulsator) instability strip, and look for the presence or absence of pulsation with Kepler's unprecedented photometry. Our results are as follows: i) From our measurements of temperature and surface gravity, 12 of the 23 DA white dwarfs from this work fall well outside of the instability strip. The Kepler photometry available for 11 of these WDs allows us to confirm that none are pulsating. One of these eleven happens to be a presumed binary, KIC 11604781, with a period of ˜5 days. ii) The remaining 11 DA white dwarfs are instability strip candidates, potentially falling within the current, empirical instability strip, after accounting for uncertainties. These WDs will help constrain the strip's location further, as eight are near the blue edge and three are near the red edge of the instability strip. Four of these WDs do not have Kepler photometry, so ground-based photometry is needed to determine the pulsation nature of these white dwarfs. The remaining seven have Kepler photometry available, but do not show any periodicity on typical WD pulsation timescales.

  11. EROS 2 proper motion survey a field brown dwarf and an L dwarf companion to LHS 102

    CERN Document Server

    Goldman, B; Forveille, T; Afonso, C; Alard, C; Albert, J N; Andersen, J; Ansari, R; Aubourg, E; Bareyre, P; Bauer, F; Beaulieu, J P; Borsenberger, J; Bouquet, A; Char, S; Charlot, X; Couchot, F; Coutures, C; Derue, F; Ferlet, R; Fouqué, P; Glicenstein, J F; Gould, A; Graff, D S; Gros, M H; Haïssinski, J; Hamilton, J C; Hardin, D P; De Kat, J; Kim, A; Lasserre, T; Lesquoy, E; Loup, C; Magneville, C; Mansoux, B; Marquette, J B; Martín, E L; Maurice, E; Milshtein, A I; Moniez, M; Palanque-Delabrouille, Nathalie; Perdereau, O; Prévôt, L; Regnault, N; Rich, J; Spiro, Michel; Vidal-Madjar, A; Virgoux, L; Zylberajch, S

    1999-01-01

    We report the discovery of two L dwarfs (the new spectral class defined for dwarfs cooler than the M type) in a two-epoch CCD proper motion survey of 413 square degrees, complemented by infrared photometry from DENIS. One of them has a strong lithium line and is therefore a brown dwarf. The other is a common proper motion companion to the mid-M dwarf LHS 102 (GJ 1001), which has a well determined trigonometric parallax. LHS 102B is thus the coolest L dwarf of known distance and luminosity. Its infrared absolute photometry are very well reproduced by the Allard et al DUSTY models.

  12. Interactive inverse kinematics for human motion estimation

    DEFF Research Database (Denmark)

    Engell-Nørregård, Morten Pol; Hauberg, Søren; Lapuyade, Jerome

    2009-01-01

    We present an application of a fast interactive inverse kinematics method as a dimensionality reduction for monocular human motion estimation. The inverse kinematics solver deals efficiently and robustly with box constraints and does not suffer from shaking artifacts. The presented motion...... estimation system uses a single camera to estimate the motion of a human. The results show that inverse kinematics can significantly speed up the estimation process, while retaining a quality comparable to a full pose motion estimation system. Our novelty lies primarily in use of inverse kinematics...... to significantly speed up the particle filtering. It should be stressed that the observation part of the system has not been our focus, and as such is described only from a sense of completeness. With our approach it is possible to construct a robust and computationally efficient system for human motion estimation....

  13. Kinematic analysis of movement imitation in apraxia

    National Research Council Canada - National Science Library

    Hermsdörfer, J; Mai, N; Spatt, J; Marquardt, C; Veltkamp, R; Goldenberg, G

    1996-01-01

    Accuracy of the final position and kinematics of movement were analysed during the imitation of meaningless gestures in patients with unilateral brain lesions who performed with the hand ipsilateral...

  14. Kinematics analysis of a novel planar parallel manipulator with kinematic redundancy

    Energy Technology Data Exchange (ETDEWEB)

    Qu, Haibo; Guo, Sheng [Beijing Jiaotong University, Beijing (China)

    2017-04-15

    In this paper, a novel planar parallel manipulator with kinematic redundancy is proposed. First, the Degrees of freedom (DOF) of the whole parallel manipulator and the Relative DOF (RDOF) between the moving platform and fixed base are studied. The results indicate that the proposed mechanism is kinematically redundant. Then, the kinematics, Jacobian matrices and workspace of this proposed parallel manipulator with kinematic redundancy are analyzed. Finally, the statics simulation of the proposed parallel manipulator is performed. The obtained stress and displacement distribution can be used to determine the easily destroyed place in the mechanism configurations.

  15. Morphologic and Kinematic Characteristics of Elite Sprinters

    OpenAIRE

    Čoh, M.; Milanović, D; Kampmiller, T.

    2001-01-01

    The purpose of the study was to ascertain the basic morphologic and kinematic characteristics of elite sprinters. The sample included 24 sprinters, with times over a 100 m distance between 10.21 s and 11.19 s. Morphologic characteristics of the sprinters were measured with a test battery of 17 measures, obtained according to the methodology prescribed by the International Biologic Programme (IBP). The kinematic variables were obtained from a flying start 20 m run and a 20 m run...

  16. Dynamic Control of Kinematically Redundant Robotic Manipulators

    Directory of Open Access Journals (Sweden)

    Erling Lunde

    1987-07-01

    Full Text Available Several methods for task space control of kinematically redundant manipulators have been proposed in the literature. Most of these methods are based on a kinematic analysis of the manipulator. In this paper we propose a control algorithm in which we are especially concerned with the manipulator dynamics. The algorithm is particularly well suited for the class of redundant manipulators consisting of a relatively small manipulator mounted on a larger positioning part.

  17. DIDACTIC AUTOMATED STATION OF COMPLEX KINEMATICS

    Directory of Open Access Journals (Sweden)

    Mariusz Sosnowski

    2014-03-01

    Full Text Available The paper presents the design, control system and software that controls the automated station of complex kinematics. Control interface and software has been developed and manufactured in the West Pomeranian University of Technology in Szczecin in the Department of Automated Manufacturing Systems Engineering and Quality. Conducting classes designed to teach programming and design of structures and systems for monitoring the robot kinematic components with non-standard structures was the reason for installation of the control system and software.

  18. Kinematical coincidence method in transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Acosta, L.; Amorini, F. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Auditore, L. [INFN Gruppo Collegato di Messina and Dipartimento di Fisica, Università di Messina (Italy); Berceanu, I. [Institute for Physics and Nuclear Engineering, Bucharest (Romania); Cardella, G., E-mail: cardella@ct.infn.it [INFN—Sezione di Catania, Via S. Sofia, 95123 Catania (Italy); Chatterjiee, M.B. [Saha Institute for Nuclear Physics, Kolkata (India); De Filippo, E. [INFN—Sezione di Catania, Via S. Sofia, 95123 Catania (Italy); Francalanza, L.; Gianì, R. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia, Catania (Italy); Grassi, L. [INFN—Sezione di Catania, Via S. Sofia, 95123 Catania (Italy); Rudjer Boskovic Institute, Zagreb (Croatia); Grzeszczuk, A. [Institut of Physics, University of Silesia, Katowice (Poland); La Guidara, E. [INFN—Sezione di Catania, Via S. Sofia, 95123 Catania (Italy); Centro Siciliano di Fisica Nucleare e Struttura della Materia, Catania (Italy); Lanzalone, G. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Facoltà di Ingegneria e Architettura, Università Kore, Enna (Italy); Lombardo, I. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Dipartimento di Scienze Fisiche, Università Federico II and INFN Sezione di Napoli (Italy); Loria, D.; Minniti, T. [INFN Gruppo Collegato di Messina and Dipartimento di Fisica, Università di Messina (Italy); Pagano, E.V. [INFN—Laboratori Nazionali del Sud, Via S. Sofia, Catania (Italy); Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia, Catania (Italy); and others

    2013-07-01

    A new method to extract high resolution angular distributions from kinematical coincidence measurements in binary reactions is presented. Kinematics is used to extract the center of mass angular distribution from the measured energy spectrum of light particles. Results obtained in the case of {sup 10}Be+p→{sup 9}Be+d reaction measured with the CHIMERA detector are shown. An angular resolution of few degrees in the center of mass is obtained. The range of applicability of the method is discussed.

  19. Chiral quark model with relativistic kinematics

    CERN Document Server

    Garcilazo, H

    2003-01-01

    The non-strange baryon spectrum is studied within a three-body model that incorporates relativistic kinematics. We found that the combined effect of relativistic kinematics together with the pion exchange between quarks is able to reverse the order of the first positive- and negative-parity nucleon excited states as observed experimentally. Including the chiral partner of the pion (the $\\sigma$ meson) leads to an overall good description of the spectrum.

  20. Three New Eclipsing White-dwarf - M-dwarf Binaries Discovered in a Search for Transiting Planets Around M-dwarfs

    CERN Document Server

    Law, Nicholas M; Street, Rachel; Fulton, Benjamin J; Hillenbrand, Lynne A; Shporer, Avi; Lister, Tim; Baranec, Christoph; Bloom, Joshua S; Bui, Khanh; Burse, Mahesh P; Cenko, S Bradley; Das, H K; Davis, Jack T C; Dekany, Richard G; Filippenko, Alexei V; Kasliwal, Mansi M; Kulkarni, S R; Nugent, Peter; Ofek, Eran O; Poznanski, Dovi; Quimby, Robert M; Ramaprakash, A N; Riddle, Reed; Silverman, Jeffrey M; Sivanandam, Suresh; Tendulkar, Shriharsh

    2011-01-01

    We present three new eclipsing white-dwarf / M-dwarf binary systems discovered during a search for transiting planets around M-dwarfs. Unlike most known eclipsing systems of this type, the optical and infrared emission is dominated by the M-dwarf components, and the systems have optical colors and discovery light curves consistent with being Jupiter-radius transiting planets around early M-dwarfs. We detail the PTF/M-dwarf transiting planet survey, part of the Palomar Transient Factory (PTF). We present a Graphics Processing Unit (GPU)-based box-least-squares search for transits that runs approximately 8X faster than similar algorithms implemented on general purpose systems. For the discovered systems, we decompose low-resolution spectra of the systems into white-dwarf and M-dwarf components, and use radial velocity measurements and cooling models to estimate masses and radii for the white dwarfs. The systems are compact, with periods between 0.35 and 0.45 days and semimajor axes of approximately 2 solar radi...

  1. Fluid Atmospheres of Cool White Dwarfs

    Science.gov (United States)

    Kowalski, P.

    2004-05-01

    We investigate quantitatively for the first time the dense fluid effects in the surface layers of very cool white dwarf stars. In general, the gas is so tenuous in stellar atmospheres that non-ideal gas effects are negligible. One important exception are the atmospheres of cool white dwarfs, especially those rich in helium, where temperature varies from 1000K to 10000K, the densities reach values as large as 2 \\ g/cm3, and pressure is as high as 1 \\ Mbar. Under such conditions, the atmosphere is no longer an ideal gas, but must be treated as a dense fluid. New physical effects occur. Helium atoms become strongly correlated and refraction effects are present. Opacity sources, such as He- free-free absorption, require different treatment from diluted gases. The refractive index departs from unity and can be as large as 1.35. We present the first solution of the radiative transfer in refractive atmospheres of cool white dwarfs. The importance of total internal reflection is discussed. We find that through the constraint of the radiative equilibrium, the total internal reflection warms the white dwarf atmosphere in optically thin surface regions. Strong curvature of rays results in a much weakened limb darkening effect. This preliminary result suggests that dense fluid effects may have a significant impact on studies of very cool white dwarf stars. This research was supported by NSF grant AST97-31438, NASA grant NAG5-8906, and by the United States Department of Energy under contract W-7405-ENG-36.

  2. Youngest Brown Dwarf Yet in a Multiple Stellar System

    Science.gov (United States)

    2000-07-01

    to an atmospheric temperature of "only" ~2200 °C (2500 K). For comparison, that of the Sun is ~ 6000 °C. The hydrogen (H-alpha) emission line indicates strong activity in the upper atmospheric layers (the chromosphere), as normally found in young stars and young Brown Dwarfs. Moreover, the comparatively weak sodium (Na) absorption line shows that this object must be relatively large for its low mass, and that it is still in the early stage of contraction. These are clear signs of young age and fully consistent with TWA-5 B being a bona-fide companion to the young star TWA-5 A . In fact, the possibility that an object as cold as TWA-5 B is located within 2 arcsec from TWA-5 A by chance is less than 10 -8. The motion of TWA-5 B ESO PR Photo 17d/00 ESO PR Photo 17d/00 [Preview - JPEG: 400 x 463 pix - 64k] [Normal - JPEG: 800 x 925 pix - 140k] Caption : The diagramme shows the relative positions of TWA-5 A and TWA-5 B , as measured on the sky by the HST in 1998 (points 1 and 2) and the VLT in 2000 (3 and 4). The ellipses indicate the measurement uncertainties. It is obvious that the two objects move in nearly the same direction and with the same speed. This greatly strengthens the conclusion that they are physically connected in the same multiple stellar system. When comparing the HST positional observations from 1998 and those with the VLT in 2000 ( PR Photo 17d/00 ), it is obvious that TWA-5 A and TWA-5 B move with very nearly the same speed and in the same direction on the sky. There is therefore no doubt that the two objects are physically connected within a stellar multiple system. At the distance of about 180 light-years, the angular separation (2 arcsec) corresponds to a projected distance of 110 AU (about 2.75 times the mean distance between the Sun and the outermost planet in the solar system, Pluto). From this and the mass of TWA-5 A , it is possible to conclude that one full orbit of TWA-5 B around TWA-5 A will last about 900 years. Mass, temperature and age

  3. Calibration of the MEarth Photometric System: Optical Magnitudes and Photometric Metallicity Estimates for 1802 Nearby M-dwarfs

    CERN Document Server

    Dittmann, Jason A; Charbonneau, David; Newton, Elisabeth R

    2015-01-01

    The MEarth Project is a photometric survey systematically searching the smallest stars nearest to the Sun for transiting rocky planets. Since 2008, MEarth has taken approximately two million images of 1844 stars suspected to be mid-to-late M dwarfs. We have augmented this survey by taking nightly exposures of photometric standard stars and have utilized this data to photometrically calibrate the $MEarth$ system, identify photometric nights, and obtain an optical magnitude with $1.5\\%$ precision for each M dwarf system. Each optical magnitude is an average over many years of data, and therefore should be largely immune to stellar variability and flaring. We combine this with trigonometric distance measurements, spectroscopic metallicity measurements, and 2MASS infrared magnitude measurements in order to derive a color-magnitude-metallicity relation across the mid-to-late M dwarf spectral sequence that can reproduce spectroscopic metallicity determinations to a precision of 0.1 dex. We release optical magnitude...

  4. The First Brown Dwarf/Planetary-Mass Object in the 32 Orionis Group

    CERN Document Server

    Burgasser, Adam J; Mamajek, Eric E; Gagne, Jonathan; Faherty, Jacqueline K; Tallis, Melisa; Choban, Caleb; Escala, Ivanna; Aganze, Christian

    2016-01-01

    The 32 Orionis group is a co-moving group of roughly 20 young (24 Myr) M3-B5 stars 100 pc from the Sun. Here we report the discovery of its first substellar member, WISE J052857.69+090104.2. This source was previously reported to be an M giant star based on its unusual near-infrared spectrum and lack of measurable proper motion. We re-analyze previous data and new moderate-resolution spectroscopy from Magellan/FIRE to demonstrate that this source is a young near-infrared L1 brown dwarf with very low surface gravity features. Spectral model fits indicate T$_{eff}$ = 1880$^{+150}_{-70}$ K and $\\log{g}$ = 3.8$^{+0.2}_{-0.2}$ (cgs), consistent with a 15-22 Myr object with a mass near the deuterium-burning limit. Its sky position, estimated distance, kinematics (both proper motion and radial velocity), and spectral characteristics are all consistent with membership in 32 Orionis, and its temperature and age imply a mass (M = 14$^{+4}_{-3}$ M$_{Jup}$) that straddles the brown dwarf/planetary-mass object boundary. T...

  5. Spitzer Trigonometric Parallaxes of the Solar Neighborhood's Coldest Brown Dwarfs, Part 2

    Science.gov (United States)

    Kirkpatrick, J. Davy; Gelino, Christopher; Beichman, Charles; Martin, Emily; Smart, Richard; Faherty, Jacqueline; Tinney, Christopher; Cushing, Michael; Schneider, Adam; Wright, Edward; Lowrance, Patrick

    2016-08-01

    Objects in the immediate solar neighborhood serve as touchstones of stellar populations throughout the rest of the Milky Way and the Universe in general. A detailed accounting and characterization of these objects is therefore of fundamental importance to many fields of astrophysics. One of the most fundamental properties is distance, which directly determines absolute luminosity and space density and aids in the decipherment of radius, kinematics, age, the mass function, etc. The Gaia mission is soon poised to revolutionize our understanding of the solar neighborhood through micro-arcsecond astrometric monitoring. Its sensitivity, however, is limited to objects that emit strongly at wavelengths shorter than 1 micron; Gaia will be unable to detect any objects as cool as late-T and Y dwarfs (250-1100K). Nevertheless, these very cold objects are critically important not only to our understanding of the star formation process at the lowest masses, but also in our comprehension of the physical mechanisms present in cold, exoplanet-like atmospheres. In this proposal, we extend our distance determinations to objects colder than those Gaia can probe by continuing to measure parallaxes, as begun in our Cycle 9-10 program 90007, for all T6 and later brown dwarfs within 20 pc of the Sun.

  6. A deep Large Binocular Telescope view of the Canes Venatici I dwarf galaxy

    CERN Document Server

    Martin, Nicolas F; De Jong, Jelte T A; Rix, Hans-Walter; Bell, Eric F; Sand, David J; Hill, John M; Kochanek, Christopher S; Thompson, David; Burwitz, Vadim; Giallongo, Emanuele; Ragazzoni, Roberto; Diolaiti, Emiliano; Gasparo, Federico; Grazian, Andrea; Pedichini, Fernando; Bechtold, Jill

    2007-01-01

    We present the first deep color-magnitude diagram of the Canes Venatici I (CVnI) dwarf galaxy from observations with the wide field Large Binocular Camera of the Large Binocular Telescope. Reaching down to the main-sequence turnoff of the oldest stars, it reveals a dichotomy in the stellar populations of CVnI: it harbors an old (>~ 10 Gyr), metal-poor ([Fe/H] ~ -2.0) and spatially extended population along with a much younger (~1.4-2.0 Gyr), 0.5 dex more metal-rich, and spatially more concentrated population. These young stars are also offset by ~100 pc to the East of the center of the galaxy. The data suggest that this young population should be identified with the kinematically cold stellar component found by Ibata et al. (2006). CVnI therefore follows the behavior of the other remote MW dwarf spheroidals which all contain intermediate age and/or young populations: a complex star formation history is possible in extremely low-mass galaxies.

  7. Dark matter annihilation and decay from non-spherical dark halos in the Galactic dwarf satellites

    CERN Document Server

    Hayashi, Kohei; Matsumoto, Shigeki; Ibe, Masahiro; Ishigaki, Miho N; Sugai, Hajime

    2016-01-01

    The dwarf spheroidal (dSph) galaxies in the Milky Way are the primary targets for the indirect searches for particle dark matter. In order to set robust constraints on candidates of dark matter particle, understanding of the dark halo structure of these systems is of substantial importance. In this paper, we first evaluate the astrophysical factor for dark matter annihilation and decay in 24 dSphs with taking into account non-spherical dark halo, using generalized axisymmetric mass models based on axisymmetric Jeans equations. First, from fitting analysis of the most recent kinematic data available, our axisymmetric mass models are so much better fit than previous spherical ones, thus our work should be the most realistic and reliable estimator for astrophysical factors. Second, we find that among analyzed dSphs, Triangulum 2 and Ursa Major II ultra faint dwarf galaxies are the most promising but large uncertain targets for dark matter annihilation while Draco classical dSph is the most robust and detectable ...

  8. Constraints on MACHO Dark Matter from the Star Cluster in the Dwarf Galaxy Eridanus II

    CERN Document Server

    Brandt, Timothy D

    2016-01-01

    I show that a recently discovered star cluster near the center of the ultra-faint dwarf galaxy Eridanus II provides strong constraints on massive compact halo objects (MACHOs) of >~5 M_sun as the main component of dark matter. MACHO dark matter will dynamically heat the cluster, driving it to larger sizes and higher velocity dispersions until it dissolves into its host galaxy. The star cluster has a luminosity of just ~2000 L_sun and is relatively puffy, with a half-light radius of 13 pc, making it much more fragile than other known clusters in dwarf galaxies. For a wide range of plausible dark matter halo properties, Eri II's star cluster combines with existing constraints from microlensing, wide binaries, and disk kinematics to rule out dark matter composed entirely of MACHOs from ~10$^{-7}$ M_sun up to arbitrarily high masses. The cluster in Eri II closes the ~20--100 M_sun window of allowed MACHO dark matter and provides much stronger constraints than wide Galactic binaries for MACHOs of up to thousands o...

  9. An upper limit on the mass of the black hole in Ursa Minor dwarf galaxy

    CERN Document Server

    Lora, V; Raga, A; Esquivel, A

    2009-01-01

    The well-established correlations between the mass of massive black holes (BHs) in the nuclei of most studied galaxies and various global properties of their hosting galaxy lend support to the idea that dwarf galaxies and globular clusters could also host a BH in their centers. Direct kinematic detection of BHs in dwarf spheroidal (dSph) galaxies are seriously hindered by the small number of stars inside the gravitational influence region of the BH. The aim of this Letter is to establish an upper dynamical limit on the mass of the putative BH in the Ursa Minor (UMi) dSph galaxy. We present direct N-body simulations of the tidal disruption of the dynamical fossil observed in UMi, with and without a massive BH. We find that the observed substructure is incompatible with the presence of a massive BH of (2-3)x10^4 Msun within the core of UMi. These limits are consistent with the extrapolation of the M_{BH}-sigma relation to the M_{BH}<10^6 Msun regime. We also show that the BH may be off-center with respect to...

  10. An extended star formation history in an ultra-compact dwarf

    Science.gov (United States)

    Norris, Mark A.; Escudero, Carlos G.; Faifer, Favio R.; Kannappan, Sheila J.; Forte, Juan Carlos; van den Bosch, Remco C. E.

    2015-08-01

    There has been significant controversy over the mechanisms responsible for forming compact stellar systems like ultra-compact dwarfs (UCDs), with suggestions that UCDs are simply the high-mass extension of the globular cluster population, or alternatively, the liberated nuclei of galaxies tidally stripped by larger companions. Definitive examples of UCDs formed by either route have been difficult to find, with only a handful of persuasive examples of stripped-nucleus-type UCDs being known. In this paper, we present very deep Gemini/GMOS spectroscopic observations of the suspected stripped-nucleus UCD NGC 4546-UCD1 taken in good seeing conditions (<0.7 arcsec). With these data we examine the spatially resolved kinematics and star formation history of this unusual object. We find no evidence of a rise in the central velocity dispersion of the UCD, suggesting that this UCD lacks a massive central black hole like those found in some other compact stellar systems, a conclusion confirmed by detailed dynamical modelling. Finally, we are able to use our extremely high signal-to-noise spectrum to detect a temporally extended star formation history for this UCD. We find that the UCD was forming stars since the earliest epochs until at least 1-2 Gyr ago. Taken together these observations confirm that NGC 4546-UCD1 is the remnant nucleus of a nucleated dwarf galaxy that was tidally destroyed by NGC 4546 within the last 1-2 Gyr.

  11. Faint dwarfs as a test of DM models: WDM vs. CDM

    CERN Document Server

    Governato, Fabio; Pontzen, Andrew; Loebman, Sarah; Reed, Darren; Brooks, Alyson M; Behroozi, Peter; Christensen, Charlotte; Madau, Piero; Mayer, Lucio; Shen, Sijing; Walker, Matthew; Quinn, Thomas; Wadsley, James

    2014-01-01

    We use high resolution Hydro$+$N-Body cosmological simulations to compare the assembly and evolution of a small field dwarf (stellar mass ~ 10$^{6-7}$ M$\\odot$, total mass 10$^{10}$ M$\\odot$ in $\\Lambda$ dominated CDM and 2keV WDM cosmologies. We find that star formation (SF) in the WDM model is reduced and delayed by 1-2 Gyr relative to the CDM model, independently of the details of SF and feedback. Independent of the DM model, but proportionally to the SF efficiency, gas outflows lower the central mass density through `dynamical heating', such that all realizations have circular velocities $<$ 20kms at 500$~$pc, in agreement with local kinematic constraints. As a result of dynamical heating, older stars are less centrally concentrated than younger stars, similar to stellar population gradients observed in nearby dwarf galaxies. We translate our simulations into artificial color-magnitude diagrams and star formation histories in order to directly compare to available observations. The simulated galaxies f...

  12. The Herschel Virgo Cluster Survey XIV: transition-type dwarf galaxies in the Virgo cluster

    CERN Document Server

    De Looze, Ilse; Boselli, Alessandro; Cortese, Luca; Fritz, Jacopo; Auld, Robbie; Bendo, George J; Bianchi, Simone; Boquien, Médéric; Clemens, Marcel; Ciesla, Laure; Davies, Jonathan; Alighieri, Sperello di Serego; Grossi, Marco; Jones, Anthony; Madden, Suzanne C; Pappalardo, Ciro; Pierini, Daniele; Smith, Matthew W L; Verstappen, Joris; Vlahakis, Catherine; Zibetti, Stefano

    2013-01-01

    We use dust scaling relations to investigate the hypothesis that Virgo cluster transition-type dwarfs are infalling star-forming field galaxies, which is argued based on their optical features (e.g. disks, spiral arms, bars) and kinematic properties similar to late-type galaxies. After their infall, environmental effects gradually transform them into early-type galaxies through the removal of their interstellar medium and quenching of all star formation activity. In this paper, we aim to verify whether this hypothesis holds using far-infrared diagnostics based on Herschel observations of the Virgo cluster taken as part of the Herschel Virgo Cluster Survey (HeViCS). We select transition-type objects in the nearest cluster, Virgo, based on spectral diagnostics indicative for their residual or ongoing star formation. We detect dust Md ~ 10^{5-6} Msun in 36% of the transition-type dwarfs located on the high end of the stellar mass distribution. This suggests that the dust reservoirs present in non-detections fall...

  13. Elucidating the True Binary Fraction of VLM Stars and Brown Dwarfs with Spectral Binaries

    Science.gov (United States)

    Bardalez Gagliuffi, Daniella; Burgasser, Adam J.; Gelino, Christopher R.; SAHLMANN, JOHANNES; Schmidt, Sarah J.; Gagne, Jonathan; Skrzypek, Nathalie

    2017-01-01

    The very lowest-mass (VLM) stars and brown dwarfs are found in abundance in nearly all Galactic environments, yet their formation mechanism(s) remain an open question. One means of testing current formation theories is to use multiplicity statistics. The majority of VLM binaries have been discovered through direct imaging, and current angular resolution limits (0.05”-0.1") are coincident with the 1-4 AU peak in the projected separation distribution of known systems, suggesting an observational bias. I have developed a separation-independent method to detect T dwarf companions to late-M/early-L dwarfs by identifying methane absorption in their unresolved, low-resolution, near-infrared spectra using spectral indices and template fitting. Over 60 spectral binary candidates have been identified with this and comparable methods. I discuss follow-up observations, including laser-guide star adaptive optics imaging with Keck/NIRC2, which have confirmed 9 systems; and radial velocity and astrometric monitoring observations that have confirmed 7 others. The direct imaging results indicate a resolved binary fraction of 18%, coincident with current estimates of the VLM binary fraction; however, our sample contained 5 previously confirmed binaries, raising its true binary fraction to 47%. To more accurately measure the true VLM binary fraction, I describe the construction of an unbiased, volume-limited, near-infrared spectral sample of M7-L5 dwarfs within 25 pc, of which 4 (1%) are found to be spectral binary candidates. I model the complex selection biases of this method through a population simulation, set constraints on the true binary fraction as traced by these systems, and compare to the predictions of current formation theories. I also describe how this method may be applied to conduct a separation-unbiased search for giant exoplanets orbiting young VLM stars and brown dwarfs.

  14. DE0823-49 is a juvenile binary brown dwarf at 20.7 pc

    Science.gov (United States)

    Sahlmann, J.; Burgasser, A. J.; Martín, E. L.; Lazorenko, P. F.; Bardalez Gagliuffi, D. C.; Mayor, M.; Ségransan, D.; Queloz, D.; Udry, S.

    2015-07-01

    Astrometric monitoring of the nearby early-L dwarf DE0823-49 has revealed a low-mass companion in a 248-day orbit that was announced in an earlier work. Here, we present new astrometric and spectroscopic observations that allow us to characterise the system in detail. The optical spectrum shows Li i-absorption indicative of a young age and/or substellar mass for the primary component. The near-infrared spectrum is best reproduced by a binary system of brown dwarfs with spectral types of L1.5 + L5.5 and effective temperatures of 2150 ± 100 K and 1670 ± 140 K. To conform with the photocentric orbit size measured with astrometry and the current understanding of substellar evolution, the system must have an age in the 80-500 Myr range. Evolutionary models predict component masses in the ranges of M1 ≃ 0.028-0.063 M⊙ and M2 ≃ 0.018-0.045 M⊙ with a mass ratio of q ≃ 0.64-0.74. Multi-epoch radial velocity measurements unambiguously establish the three-dimensional orbit of the system and allow us to investigate its kinematic properties. DE0823-49 emerges as a rare example of a nearby brown dwarf binary with orbit, component properties, and age that are characterised well. It is a juvenile resident of the solar neighbourhood, but does not appear to belong to a known young association or moving group. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programme IDs 086.C-0680, 088.C-0679, 090.C-0786, and 092.C-0202.

  15. Discovery of a young planetary mass companion to the nearby M dwarf VHS J125601.92-125723.9

    CERN Document Server

    Gauza, Bartosz; Pérez-Garrido, Antonio; Osorio, Maria Rosa Zapatero; Lodieu, Nicolas; Rebolo, Rafael; Pallé, Enric; Nowak, Grzegorz

    2015-01-01

    In a search for common proper motion companions using the VISTA Hemisphere Survey and 2MASS catalogs we have identified a very red (J-Ks=2.47 mag) late-L dwarf companion of a previously unrecognized M dwarf VHS J125601.92-125723.9, located at a projected angular separation of 8.06"+/-0.03". From low-resolution optical and near-IR spectroscopy we classified the primary and the companion as an M7.5+/-0.5 and L7+/-1.5, respectively. The primary shows weaker alkali lines than field dwarfs of similar spectral type, but still consistent with either a high-gravity dwarf or a younger object of hundreds of millions of years. The secondary shows spectral features characteristic for low surface gravity objects at ages below several hundred Myr, like the triangular shape of the H-band continuum and alkali lines weaker than in field dwarfs of the same spectral type. The absence of lithium in the atmosphere of the primary and the likely membership to the Local Association allowed us to constrain the age of the system to th...

  16. Kinematics of the Danakil microplate

    Science.gov (United States)

    Eagles, Graeme; Gloaguen, Richard; Ebinger, Cynthia

    2002-10-01

    A refinement and extrapolation of recent motion estimates for the Danakil microplate, based on ancient kinematic indicators in the Afar region, describes the evolution of a microplate in the continental realm. The Danakil horst is an elevated part of this microplate, exposing a Precambrian basement within the Afar depression, the site of the Nubia-Somalia-Arabia triple junction. We compare evidence for strike- or oblique-slip faults in data from the Afar depression and southern Red Sea to small circles about published poles of rotation for the Danakil microplate with respect to Nubia. A reconstruction about the preferred pole reunites lengths of a Precambrian shear zone on the Nubia and Danakil sides and preserves a uniform basement fabric strike through Nubia, Danakil and Yemen. Since at least magnetic chron C5 (˜11 Ma) Danakil rotated about a different pole with respect to Nubia than either Somalia or Arabia, but between chrons C5 and C2A Nubia-Danakil motion was a close approximation to Nubia-Somalia motion. Since C2A relative motions of the Danakil microplate have been independent of movements on any of the neighbouring plate boundaries. We relate this to the onset of oceanic-type accretion within Afar. The resulting eastwards acceleration of Danakil was accommodated by westwards propagation of the Gulf of Aden rift that became the new, discrete, plate boundary between the Danakil microplate and the Somalia plate. Present-day activity suggests that the Red Sea and Aden rifts will link through Afar, thereby isolating the Danakil horst as a microcontinent on the Arabian margin.

  17. Constraining the nature of dark matter with the star formation history of the faintest Local Group dwarf galaxy satellites

    CERN Document Server

    Chau, Alice; Governato, Fabio

    2016-01-01

    $\\Lambda$-Warm Dark Matter (WDM) has been proposed as alternative scenario to $\\Lambda$ cold dark matter (CDM), motivated by discrepancies at the scale of dwarf galaxies, with less small-scale power and realized by collisionless particles with energies in the range $1-3$ keV. We present a new approach to constrain the viability of such WDM models using star formation histories of the dwarf spheroidal galaxies (dSphs) in the Local Group. We compare their high time-resolution star formation histories (SFHs) obtained with HST-based color magnitude diagrams with the range of possible collapse redshifts of their dark matter halos expected in CDM and in different WDM scenarios. The collapse redshift is inferred after determining a plausible infall mass of the subhalo. This is based on the current mass of individual dwarf inferred from stellar kinematics combined with results of cosmological simulations providing information on the subhalo evolution. Since WDM subhalos close to the filtering mass scale form signific...

  18. Zodiacal Exoplanets in Time (ZEIT) II. A "Super-Earth" Orbiting a Young K Dwarf in the Pleiades Neighborhood

    CERN Document Server

    Gaidos, E; RIzzuto, A; Nofi, L; Mace, G; Vanderburg, A; Feiden, G; Narita, N; Takeda, Y; Esposito, T M; De Rosa, R J; Ansdell, M; Hirano, T; Graham, J R; Kraus, A; Jaffe, D

    2016-01-01

    We describe a "super-Earth"-size ($2.30\\pm0.15R_{\\oplus}$) planet transiting an early K-type dwarf star in the Campaign 4 field observed by the K2 mission. The host star, EPIC 210363145, was identified as a member of the approximately 120-Myr-old Pleiades cluster based on its kinematics and photometric distance. It is rotationally variable and exhibits near-ultraviolet emission consistent with a Pleiades age, but its rotational period is ~20 d and its spectrum contains no H$\\alpha$ emission nor the Li I absorption expected of Pleiades K dwarfs. Instead, the star is probably an interloper that is unaffiliated with the cluster, but younger (< 1 Gyr) than the typical field dwarf. We ruled out a false positive transit signal produced by confusion with a background eclipsing binary by adaptive optics imaging and a statistical calculation. Doppler radial velocity measurements limit the companion mass to <2 times that of Jupiter. Screening of the lightcurves of 1014 potential Pleiades candidate stars uncovered...

  19. Zodiacal Exoplanets in Time (ZEIT) II. A "Super-Earth" Orbiting a Young K Dwarf in the Pleiades Neighborhood

    Science.gov (United States)

    Gaidos, E.; Mann, A. W.; Rizzuto, A.; Nofi, L.; Mace, G.; Vanderburg, A.; Feiden, G.; Narita, N.; Takeda, Y.; Esposito, T. M.; De Rosa, R. J.; Ansdell, M.; Hirano, T.; Graham, J. R.; Kraus, A.; Jaffe, D.

    2016-09-01

    We describe a "super-Earth"-size (2.30 ± 0.16R⊕) planet transiting an early K-type dwarf star in the Campaign 4 field observed by the K2 mission. The host star, EPIC 210363145, was identified as a candidate member of the approximately 120-Myr-old Pleiades cluster based on its kinematics and photometric distance. It is rotationally variable and exhibits near-ultraviolet emission consistent with a Pleiades age, but its rotational period is ≈ 20 d and its spectrum contains no Hα emission nor the Li I absorption expected of Pleiades K dwarfs. Instead, the star is probably an interloper that is unaffiliated with the cluster, but younger (≲ 1.3 Gyr) than the typical field dwarf. We ruled out a false positive transit signal produced by confusion with a background eclipsing binary by adaptive optics imaging and a statistical calculation. Doppler radial velocity measurements limit the companion mass to years), increased measurement noise due to spacecraft motion, and the intrinsic noisiness of the stars.

  20. Visualization of redundancy resolution for kinematically redundant robots through the Jacobian null space

    Science.gov (United States)

    Chen, Yu-Che; Walker, Ian D.; Cheatham, John B., Jr.

    1992-01-01

    We present a unified formulation for the inverse kinematics of redundant arms, based on a special formulation of the null space of the Jacobian. By extending (appropriately re-scaling) previously used null space parameterizations, we obtain, in a unified fashion, the manipulability measure, the null space projector, and particular solutions for the joint velocities. We obtain the minimum norm pseudo-inverse solution as a projection from any particular solution, and the method provides an intuitive visualization of the self-motion. The result is a computationally efficient, consistent approach to computing redundant robot inverse kinematics.