A lower limit of 9.5 Gyr on the age of the Galactic disk from the oldest white dwarf stars

Oswalt, Terry D.; Smith, J. Allyn; Wood, M. A.; Hintzen, P.

doi:10.1038/382692a0

Cited by 232 publications

(224 citation statements)

References 37 publications

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“…Liebert et al 1988;Evans 1992;Oswalt et al 1996, and others). For our relatively bright, therefore distant stars, this approach is less likely to work, since many are simply too far away to have measurable proper motions.…”

Section: Introductionmentioning

confidence: 92%

A hot white dwarf luminosity function from the Sloan Digital Sky Survey

Krzesiński¹,

Kleinman²,

Nitta³

et al. 2009

A&A

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Aims. We present a hot white dwarf (WD) luminosity function (LF) using data taken from the Sloan Digital Sky Survey (SDSS) Data Release 4. We present and discuss a combined LF, along with separate DA and non-DA as LFs. We explore the completeness of our LFs and interpret a sudden drop in the non-DA LF near 2 M bol as a transition of the non-DA WD atmosphere into the DA one during WD evolution. Our LF extends roughly between −0.5 < M bol < 7 or equivalently, ∼120 000 K > T eff > ∼25 000 K. Our LF should now be useful for estimates of recent star formation and for studies of neutrino and other potential particle emission losses in hot WDs. Methods. To create a sample whose completeness can be characterized fully, we used stars whose spectra were obtained via the SDSS's "hot standard" target selection criteria. The hot standard stars were purposefully targeted to a high level of completeness by the SDSS for calibration purposes. We are fortunate that many of them are hot white dwarfs stars. We further limited the sample to stars with fitted temperatures exceeding 23 500 K and log g > 7.0. We determined stellar distances for our sample based on their absolute SDSS g filter magnitudes, derived from WD stellar atmosphere model fits to the SDSS stellar spectra. Results. We compared our LF with those of other researchers where overlap occurs; however, our LFs are unique in their extension to the most luminous/hottest WDs. The cool end of our LF connects with the hot end of previously determined SDSS WD LFs and agreement here is quite good. It is also good with previous non-SDSS WD LFs. We note distinct differences between the DA and non-DA LFs and discuss the reliability of the DA LF at its hot end. We have extended the range of luminosities covered in the most recent WD LFs. The SDSS sample is understood quite well and its exploration should contribute to a number of new insights into early white dwarf evolution.

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Section: Introductionmentioning

confidence: 92%

A hot white dwarf luminosity function from the Sloan Digital Sky Survey

Krzesiński¹,

Kleinman²,

Nitta³

et al. 2009

A&A

View full text Add to dashboard Cite

show abstract

“…During the last few decades both observations and theory have improved to a level that has made it possible to employ white dwarf (WD) stars for estimating ages of stellar populations in the solar neighbourhood (i.e., Winget et al 1987;García-Berro et al 1988;Oswalt et al 1996), open (i.e., Richer et al 1998;von Hippel 2005;Bedin et al 2008aBedin et al , 2010 and globular (i.e., Hansen et al 2004Hansen et al , 2007Bedin et al 2009) clusters.…”

Section: Introductionmentioning

confidence: 99%

Hubble Space Telescope observations of the Kepler-field cluster NGC 6819 – I. The bottom of the white dwarf cooling sequence★

Bedin

Salaris

Anderson

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We use Hubble Space Telescope (HST ) to reach the end of the white dwarf (WD) cooling sequence (CS) in the solar-metallicity open cluster NGC 6819. Our photometry and completeness tests show a sharp drop in the number of WDs along the CS at magnitudes fainter than m F606W = 26.050 ± 0.075. This implies an age of 2.25 ± 0.20 Gyr, consistent with the age of 2.25 ± 0.30 Gyr obtained from fits to the main-sequence turn-off. The use of different WD cooling models and initial-final-mass relations have a minor impact the WD age estimate, at the level of ∼0.1 Gyr. As an important by-product of this investigation we also release, in electronic format, both the catalogue of all the detected sources and the atlases of the region (in two filters). Indeed, this patch of sky studied by HST (of size ∼70 arcmin 2 ) is entirely within the main Kepler-mission field, so the high-resolution images and deep catalogues will be particularly useful.

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“…In fact, the disk white dwarf luminosity function has become an important tool to determine some properties of the local neighborhood, such as its age (Winget et al 1987;García-Berro et al 1988;Hernanz et al 1994), or the past history of the star formation rate (Noh & Scalo 1990;Díaz-Pinto et al 1994;Isern et al 1995a,b). This has been possible because now we have improved observational luminosity functions (Liebert et al 1988;Oswalt et al 1996;Leggett et al 1998) and because we have reliable cooling sequences -see, for instance, Salaris et al (2000), and references therein.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo simulations of the halo white dwarf population

Garcı́a–Berro

Torres

Isern

et al. 2004

A&A

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Abstract. The interpretation of microlensing results towards the Large Magellanic Cloud (LMC) still remains controversial. While white dwarfs have been proposed to explain these results and, hence, to contribute significantly to the mass budget of our Galaxy, there are also several constraints on the role played by white dwarfs. In this paper we analyze self-consistently and simultaneously four different results, namely, the local halo white dwarf luminosity function, the microlensing results reported by the MACHO team towards the LMC, the results of Hubble Deep Field (HDF) and the results of the EROS experiment, for several initial mass functions and halo ages. We find that the proposed log-normal initial mass functions do not contribute to solve the problem posed by the observed microlensing events and, moreover, they overproduce white dwarfs when compared to the results of the HDF and of the EROS survey. We also find that the contribution of hydrogen-rich white dwarfs to the dynamical mass of the halo of the Galaxy cannot be more than ∼4%.

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A lower limit of 9.5 Gyr on the age of the Galactic disk from the oldest white dwarf stars

Cited by 232 publications

References 37 publications

A hot white dwarf luminosity function from the Sloan Digital Sky Survey

A hot white dwarf luminosity function from the Sloan Digital Sky Survey

Hubble Space Telescope observations of the Kepler-field cluster NGC 6819 – I. The bottom of the white dwarf cooling sequence★

Monte Carlo simulations of the halo white dwarf population

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