The Potential of White Dwarf Cosmochronology

In the light of recent significant progress on both the observational and theoretical fronts, we review the status of white dwarf stars as cosmochronometers. These objects represent the end products of stellar evolution for the vast majority of stars and, as such, can be used to constrain the ages of various populations of evolved stars in the Galaxy. For example, the oldest white dwarfs in the solar neighborhood (the remnants of the very first generation of intermediate-mass stars in the Galactic disk) are still visible and can be used, in conjunction with cooling theory, to estimate the age of the disk. More recent observations suggest the tantalizing possibility that a population of very old white dwarfs inhabits the Galactic halo. Such a population may contribute significantly to baryonic "dark" matter in the Milky Way and may be used to obtain an independent estimate of the age of the halo. In addition, white dwarf cosmochronology is likely to play a very significant role in the coming era of giant 8-10 m telescopes when faint white dwarf populations should be routinely discovered and studied in open and globular clusters.

[1]  Martin Schwarzschild,et al.  Structure and evolution of the stars. , 1958 .

[2]  M. Hernanz,et al.  Cooling Theory of Crystallized White Dwarfs , 1994 .

[3]  A survey for cool white dwarfs and the age of the Galactic disc , 1999, astro-ph/9903345.

[4]  G. Gilmore,et al.  The White Dwarf Cooling Age of the Open Cluster NGC 2420 , 2000, astro-ph/0006033.

[5]  M. Hernanz,et al.  THE COOLING OF OXYGEN-NEON WHITE DWARFS , 1997 .

[6]  Didier Saumon,et al.  New model atmospheres for very cool white dwarfs with mixed H/He and pure He compositions , 1995 .

[7]  L. Mestel.  On the Theory of White Dwarf Stars: I. The Energy Sources of White Dwarfs , 1952 .

[8]  Gilles Chabrier,et al.  An Equation of State for Low-Mass Stars and Giant Planets , 1995 .

[9]  R. Larson.  Bimodal star formation and remnant-dominated galactic models , 1986 .

[10]  Pierre Bergeron,et al.  PHOTOMETRIC CALIBRATION OF HYDROGEN- AND HELIUM-RICH WHITE DWARF MODELS , 1995 .

[11]  C. I. O. Technology.,et al.  Stellar forensics — I. Cooling curves , 1997, astro-ph/9708273.

[12]  Gilles Chabrier,et al.  Contribution of Brown Dwarfs and White Dwarfs to Recent Microlensing Observations and to the Halo Mass Budget , 1996, astro-ph/9606083.

[13]  H. Horn,et al.  Some properties of very low temperature, pure helium surface layers of degenerate dwarfs , 1977 .

[14]  H. Iyetomi,et al.  Electrical and thermal conductivities of dense matter in the liquid metal phase. I - High-temperature results , 1983 .

[15]  William A. Fowler,et al.  Thermonuclear Reaction Rates, III , 1967 .

[16]  S. Smartt,et al.  On the parallax of WD 0346++246: a halo white dwarf candidate , 1999 .

[17]  N. Itoh,et al.  Electrical and thermal conductivities of dense matter in the crystalline lattice phase , 1984 .

[18]  M. Hernanz,et al.  THE INFLUENCE OF CRYSTALLIZATION ON THE LUMINOSITY FUNCTION OF WHITE DWARFS , 1994 .

[19]  V. University,et al.  The Ages of Very Cool Hydrogen-rich White Dwarfs , 2000, astro-ph/0007031.

[20]  M. Wood,et al.  Theoretical white dwarf luminosity functions: DA models , 1995 .

[21]  N. Hambly,et al.  WD 0346+246: A Very Low Luminosity, Cool Degenerate in Taurus , 1997 .

[22]  J. Scalo,et al.  History of the Milky Way star formation rate from the white dwarf luminosity function , 1990 .

[23]  W. Hubbard,et al.  THERMAL CONDUCTION BY ELECTRONS IN STELLAR MATTER. , 1969 .

[24]  T. Hippel.  CONTRIBUTION OF WHITE DWARFS TO CLUSTER MASSES , 1998, astro-ph/9802199.

[25]  Garching,et al.  The Cooling of CO White Dwarfs: Influence of the Internal Chemical Distribution , 1997, astro-ph/9704038.

[26]  T. Grenfell,et al.  The effects of differences in composition, equation of state, and mixing length upon the structure of white-dwarf convection zones , 1974 .

[27]  N. Itoh,et al.  Electrical and Thermal Conductivities of Dense Matter in the Crystalline Lattice Phase. II. Impurity Scattering , 1993 .

[28]  COOLING SEQUENCES AND COLOR-MAGNITUDE DIAGRAMS FOR COOL WHITE DWARFS WITH HYDROGEN ATMOSPHERES , 2000, astro-ph/0006363.

[29]  Is Galactic Dark Matter White , 1999, astro-ph/9901145.

[30]  S. O. Kepler,et al.  An independent method for determining the age of the universe , 1987 .

[31]  M. Hernanz,et al.  The Energetics of Crystallizing White Dwarfs Revisited Again , 1999, astro-ph/9907077.

[32]  H. Hayashi,et al.  Neutrino Energy Loss in Stellar Interiors. VII. Pair, Photo-, Plasma, Bremsstrahlung, and Recombination Neutrino Processes , 1996 .

[33]  M. Ruiz,et al.  The Cool White Dwarf Luminosity Function and the Age of the Galactic Disk , 1998 .

[34]  H. Richer,et al.  Isochrones and Luminosity Functions for Old White Dwarfs , 1999, astro-ph/9908337.

[35]  S. Smartt,et al.  Infrared spectrum of an extremely cool white-dwarf star , 2000, Nature.

[36]  G. Fontaine,et al.  Synthetic spectra and atmospheric properties of cool DA white dwarfs , 1991 .

[37]  S. K. Leggett,et al.  Photometric and Spectroscopic Analysis of Cool White Dwarfs with Trigonometric Parallax Measurements , 2000, astro-ph/0011286.

[38]  B. Hansen,et al.  Cooling Models for Old White Dwarfs , 1999, astro-ph/9903025.

[39]  G. Fontaine,et al.  A Critical Look at the Question of Thick vs Thin Hydrogen and Helium Envelopes in White Dwarfs , 1997 .

[40]  D. Lamb,et al.  Evolution of crystallizing pure $sup 12$C white dwarfs , 1975 .

[41]  EVOLUTIONARY CALCULATIONS OF PHASE SEPARATION IN CRYSTALLIZING WHITE DWARF STARS , 1999, astro-ph/9905332.

[42]  G. Fontaine,et al.  Evolutionary models for pulsation studies of white dwarfs , 1990 .

[43]  M. Wood,et al.  Constraints on the age and evolution of the Galaxy from the white dwarf luminosity function , 1992 .

[44]  H. Horn.  15. COOLING OF WHITE DWARFS , 1971 .

[45]  M. Hernanz,et al.  The Physics of Crystallizing White Dwarfs , 1997, astro-ph/9703028.

[46]  D. Saumon,et al.  Pure Hydrogen Model Atmospheres for Very Cool White Dwarfs , 1998, astro-ph/9812107.

[47]  B. Hansen.  Old and blue white-dwarf stars as a detectable source of microlensing events , 1998, Nature.

[48]  D. Monet,et al.  The Luminosity Function of White Dwarfs , 1988 .

[49]  H. Hayashi,et al.  Electrical and thermal conductivities of dense matter in the crystalline lattice phase. III: Inclusion of lower densities , 1993 .

[50]  D. Monet,et al.  The luminosity function of white dwarfs in the local disk and halo , 1989 .

[51]  G. Fontaine,et al.  Diffusion coefficients for stellar plasmas , 1986 .

[52]  D. Minniti,et al.  Faint Blue Objects on the Hubble Deep Field North and South as Possible Nearby Old Halo White Dwarfs , 2000 .

[53]  G. Chabrier.  Quantum effects in dense coulombic matter : application to the cooling of white dwarfs , 1993 .

[54]  Douglas Scott,et al.  Faint, Moving Objects in the Hubble Deep Field: Components of the Dark Halo? , 1999, astro-ph/9908270.

[55]  White Dwarfs in Globular Clusters: Hubble Space Telescope Observations of M4* , 1997, astro-ph/9702169.

[56]  E. Salpeter,et al.  Rosseland and Planck mean opacities of a zero-metallicity gas , 1991 .

[57]  Discovery of High Proper-Motion Ancient White Dwarfs: Nearby Massive Compact Halo Objects? , 2000, The Astrophysical journal.

[58]  I. Iben,et al.  A study of the white dwarf luminosity function , 1989 .

[59]  H. Graboske,et al.  Equations of State for Stellar Partial Ionization Zones , 1977 .

[60]  M. Hernanz,et al.  White dwarfs : proceedings of the 10th European workshop on White Dwarfs, held in Blanes, Spain, 17-21 June 1996 , 1997 .

[61]  F. Rogers,et al.  Radiative atomic Rosseland mean opacity tables , 1992 .

[62]  F. D’Antona,et al.  The relation between initial and minimum final white dwarf mass for population I stars , 1986 .

[63]  J. N. Stewart,et al.  ROSSELAND OPACITY TABLES FOR POPULATION I COMPOSITIONS. , 1970 .

[64]  Forrest J. Rogers,et al.  Updated Opal Opacities , 1996 .

[65]  Maria Teresa Ruiz,et al.  The Chemical Evolution of Cool White Dwarfs and the Age of the Local Galactic Disk , 1997 .

[66]  H. Horn,et al.  Convective white-dwarf envelope model grids for H-, He-, and C-rich compositions , 1976 .

[67]  G. Wegner.  White dwarfs : proceedings of IAU Colloquium no. 114, held at Dartmouth College, Hanover, New Hampshire, USA, August 15-19, 1988 , 1989 .

[68]  L. Althaus,et al.  Evolution of helium white dwarfs with hydrogen envelopes , 1998 .

[69]  F. D’Antona,et al.  Evolution from the main sequence to the white dwarf stage for a 3 solar mass star , 1986 .

[70]  O. G. Benvenuto,et al.  Grids of white dwarf evolutionary models with masses from M=0.1 to 1.2 m⊙ , 1998 .

[71]  G. Chabrier.  Cool White Dwarfs: Cooling Theory and Galactic Implications , 1997, astro-ph/9705062.

[72]  M. Schmidt.  The Rate of Star Formation , 1959 .

[73]  R. Ibata,et al.  Received; accepted Submitted to the Astrophysical Journal Letters. , 1998 .

[74]  D. Winget,et al.  A variational approach to understanding white dwarf evolution , 1989 .