New Halo White Dwarf Candidates in the Sloan Digital Sky Survey

Kyra Dame; A. Gianninas; Mukremin Kilic; Jeffrey A. Munn; Warren R. Brown; Kurtis A. Williams; Ted von Hippel; Hugh C. Harris

doi:10.1093/mnras/stw2146

New Halo White Dwarf Candidates in the Sloan Digital Sky Survey

Kyra Dame, A. Gianninas, Mukremin Kilic, Jeffrey A. Munn, Warren R. Brown, Kurtis A. Williams, Ted von Hippel, Hugh C. Harris

Physical Sciences

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Abstract

We present optical spectroscopy and near-infrared photometry of 57 faint (g = 19–22) high proper motion white dwarfs identified through repeat imaging of ≈3100 deg 2 of the Sloan Digital Sky Survey footprint by Munn et al. We use ugriz and JH photometry to perform a model atmosphere analysis, and identify 10 ultracool white dwarfs with T eff < 4000 K, including the coolest pure H atmosphere white dwarf currently known, J1657+2638, with T eff = 3550 ± 100 K. The majority of the objects with cooling ages larger than 9 Gyr display thick disc kinematics and constrain the age of the thick disc to ≥11 Gyr. There are four white dwarfs in our sample with large tangential velocities ( v tan > 120 km s − 1 ) and UVW velocities that are more consistent with the halo than the Galactic disc. For typical 0.6M &odot; white dwarfs, the cooling ages for these halo candidates range from 2.3 to 8.5 Gyr. However, the total mainsequence+ white dwarf cooling ages of these stars would be consistent with the Galactic halo if they are slightly undermassive. Given the magnitude limits of the current large-scale surveys, many of the coolest and oldest white dwarfs remain undiscovered in the solar neighbourhood, but upcoming surveys such as Gaia and the Large Synoptic Survey Telescope should find many of these elusive thick disc and halo white dwarfs.

Original language	American English
Journal	Monthly Notices of the Royal Astronomical Society
Volume	463
DOIs	https://doi.org/10.1093/mnras/stw2146
State	Published - Aug 25 2016

Keywords

techniques: photometric
stars: atmospheres
stars: evolution
white dwarfs

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External Galaxies

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title = "New Halo White Dwarf Candidates in the Sloan Digital Sky Survey",

abstract = " We present optical spectroscopy and near-infrared photometry of 57 faint (g = 19–22) high proper motion white dwarfs identified through repeat imaging of ≈3100 deg 2 of the Sloan Digital Sky Survey footprint by Munn et al. We use ugriz and JH photometry to perform a model atmosphere analysis, and identify 10 ultracool white dwarfs with T eff < 4000 K, including the coolest pure H atmosphere white dwarf currently known, J1657+2638, with T eff = 3550 ± 100 K. The majority of the objects with cooling ages larger than 9 Gyr display thick disc kinematics and constrain the age of the thick disc to ≥11 Gyr. There are four white dwarfs in our sample with large tangential velocities ( v tan > 120 km s − 1 ) and UVW velocities that are more consistent with the halo than the Galactic disc. For typical 0.6M &odot; white dwarfs, the cooling ages for these halo candidates range from 2.3 to 8.5 Gyr. However, the total mainsequence+ white dwarf cooling ages of these stars would be consistent with the Galactic halo if they are slightly undermassive. Given the magnitude limits of the current large-scale surveys, many of the coolest and oldest white dwarfs remain undiscovered in the solar neighbourhood, but upcoming surveys such as Gaia and the Large Synoptic Survey Telescope should find many of these elusive thick disc and halo white dwarfs.",

keywords = "techniques: photometric, stars: atmospheres, stars: evolution, white dwarfs",

author = "Kyra Dame and A. Gianninas and Mukremin Kilic and Munn, {Jeffrey A.} and Brown, {Warren R.} and Williams, {Kurtis A.} and {von Hippel}, Ted and Harris, {Hugh C.}",

year = "2016",

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journal = "Monthly Notices of the Royal Astronomical Society",

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T1 - New Halo White Dwarf Candidates in the Sloan Digital Sky Survey

AU - Dame, Kyra

AU - Gianninas, A.

AU - Kilic, Mukremin

AU - Munn, Jeffrey A.

AU - Brown, Warren R.

AU - Williams, Kurtis A.

AU - von Hippel, Ted

AU - Harris, Hugh C.

PY - 2016/8/25

Y1 - 2016/8/25

N2 - We present optical spectroscopy and near-infrared photometry of 57 faint (g = 19–22) high proper motion white dwarfs identified through repeat imaging of ≈3100 deg 2 of the Sloan Digital Sky Survey footprint by Munn et al. We use ugriz and JH photometry to perform a model atmosphere analysis, and identify 10 ultracool white dwarfs with T eff < 4000 K, including the coolest pure H atmosphere white dwarf currently known, J1657+2638, with T eff = 3550 ± 100 K. The majority of the objects with cooling ages larger than 9 Gyr display thick disc kinematics and constrain the age of the thick disc to ≥11 Gyr. There are four white dwarfs in our sample with large tangential velocities ( v tan > 120 km s − 1 ) and UVW velocities that are more consistent with the halo than the Galactic disc. For typical 0.6M &odot; white dwarfs, the cooling ages for these halo candidates range from 2.3 to 8.5 Gyr. However, the total mainsequence+ white dwarf cooling ages of these stars would be consistent with the Galactic halo if they are slightly undermassive. Given the magnitude limits of the current large-scale surveys, many of the coolest and oldest white dwarfs remain undiscovered in the solar neighbourhood, but upcoming surveys such as Gaia and the Large Synoptic Survey Telescope should find many of these elusive thick disc and halo white dwarfs.

AB - We present optical spectroscopy and near-infrared photometry of 57 faint (g = 19–22) high proper motion white dwarfs identified through repeat imaging of ≈3100 deg 2 of the Sloan Digital Sky Survey footprint by Munn et al. We use ugriz and JH photometry to perform a model atmosphere analysis, and identify 10 ultracool white dwarfs with T eff < 4000 K, including the coolest pure H atmosphere white dwarf currently known, J1657+2638, with T eff = 3550 ± 100 K. The majority of the objects with cooling ages larger than 9 Gyr display thick disc kinematics and constrain the age of the thick disc to ≥11 Gyr. There are four white dwarfs in our sample with large tangential velocities ( v tan > 120 km s − 1 ) and UVW velocities that are more consistent with the halo than the Galactic disc. For typical 0.6M &odot; white dwarfs, the cooling ages for these halo candidates range from 2.3 to 8.5 Gyr. However, the total mainsequence+ white dwarf cooling ages of these stars would be consistent with the Galactic halo if they are slightly undermassive. Given the magnitude limits of the current large-scale surveys, many of the coolest and oldest white dwarfs remain undiscovered in the solar neighbourhood, but upcoming surveys such as Gaia and the Large Synoptic Survey Telescope should find many of these elusive thick disc and halo white dwarfs.

KW - techniques: photometric

KW - stars: atmospheres

KW - stars: evolution

KW - white dwarfs

UR - https://commons.erau.edu/publication/386

U2 - 10.1093/mnras/stw2146

DO - 10.1093/mnras/stw2146

M3 - Article

SN - 1365-2966

VL - 463

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

ER -

New Halo White Dwarf Candidates in the Sloan Digital Sky Survey

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