J/MNRAS/482/965 Age of the Galactic stellar halo from Gaia WDs (Kilic+, 2019)
The age of the Galactic stellar halo from Gaia white dwarfs.
Kilic M., Bergeron P., Dame K., Hambly N.C., Rowell N., Crawford C.L.
<Mon. Not. R. Astron. Soc., 482, 965-979 (2019)>
=2019MNRAS.482..965K 2019MNRAS.482..965K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, white dwarf ; Stellar distribution ; Velocity dispersion ;
Photometry
Keywords: stars: evolution - white dwarfs - Galaxy: stellar content
Abstract:
We use 156044 white dwarf candidates with ≥5σ significant
parallax measurements from the Gaia mission to measure the velocity
dispersion of the Galactic disc;
(σU,σV,σW)=(30.8,23.9,20.0)km/s. We identify
142 objects that are inconsistent with disc membership at the
>5σ level. This is the largest sample of field halo white dwarfs
identified to date. We perform a detailed model atmosphere analysis
using optical and near-infrared photometry and parallaxes to constrain
the mass and cooling age of each white dwarf. The white dwarf cooling
ages of our targets range from 7Myr for J1657+2056 to 10.3Gyr for
J1049-7400. The latter provides a firm lower limit of 10.3Gyr for the
age of the inner halo based on the well-understood physics of white
dwarfs. Including the pre-white dwarf evolutionary lifetimes, and
limiting our sample to the recently formed white dwarfs with cooling
ages of <500Myr, we estimate an age of 10.9±0.4Gyr (internal errors
only) for the Galactic inner halo. The coolest white dwarfs in our
sample also give similar results. For example, J1049-7400 has a total
age of 10.9-11.1Gyr. Our age measurements are consistent with other
measurements of the age of the inner halo, including the white dwarf
based measurements of the globular clusters M4, NGC 6397, and 47 Tuc.
Description:
We queried the Gaia data base for objects with plx≥5σplx
significant parallaxes, and followed the recommendations outlined in
Lindegren et al. (2018A&A...616A...2L 2018A&A...616A...2L, Cat. I/345) to remove
non-Gaussian outliers in colour and absolute magnitude. We employed
the astrometric and photometric quality cuts outlined in appendix C of
Lindegren et al. (2018A&A...616A...2L 2018A&A...616A...2L, Cat. I/345). We used a simple
cut in (GBP-GRP, MG) space keeping only those sources fainter than the
line joining (-1,5) and (5,25) to identify the clearly subluminous
stellar objects relative to the main sequence. The query returned
156044 sources.
We take a conservative approach, and select only those objects with
velocities that are more than 5σ away from this boundary as members
of the Galactic halo. There are 142 white dwarfs that are clearly not
compatible with a disc origin. As expected for a halo population, the
majority of these velocity outliers lag behind the disc with V~-200km/s.
Table 1 presents the Gaia Source identifications, spectral types,
positions, parallaxes, proper motions, photometry, and UVW space
velocities for each target. Table 2 presents the preferred
composition, best-fitting effective temperature, mass, surface
gravity, and the cooling age of each white dwarf.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 605 142 Gaia halo white dwarf sample
table2.dat 115 210 Best-fitting parameters for the halo white
dwarf sample
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
II/359 : The VISTA Hemisphere Survey (VHS) catalog DR4.1 (McMahon+, 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR2 Gaia DR2 source ID
21- 39 A19 --- Name Star name (JHHMMSS.ss+DDMMSS.s)
41- 45 A5 --- SpType Spectral type
47- 65 F19.15 deg RAdeg Right Ascension (ICRS) at Ep=2015.5 from
Gaia DR2
67- 79 F13.9 deg DEdeg Declination (ICRS) at Ep=2015.5 from Gaia DR2
81- 92 F12.9 mas plx Parallax from Gaia DR2
94-105 F12.7 --- Rplx Gaia DR2 parallax divided by its error
107-121 F15.9 mas/yr pmRA Proper motion in right ascension from Gaia DR2
123-133 F11.9 mas/yr e_pmRA Error on pmRA
135-149 F15.9 mas/yr pmDE Proper motion in declination from Gaia DR2
151-161 F11.9 mas/yr e_pmDE Error on pmDE
163-171 F9.6 mag Gmag Gaia G band magnitude
173-182 F10.5 --- RFG Mean flux in the G-band divided by its error
184-192 F9.6 mag BPmag Gaia BP magnitude
194-204 F11.7 --- RFBP Integrated BP mean flux divided by its error
206-214 F9.6 mag RPmag Gaia RP magnitude
216-225 F10.6 --- RFRP Integrated RP mean flux divided by its error
227-233 F7.4 mag gPmag ?=99.99 PanSTARRs g-band magnitude
(Kaiser et al. 2010SPIE.7733E..0EK,
Cat. II/349 )
235-241 F7.4 mag e_gPmag ?=99.99 Error on gPmag
243-249 F7.4 mag rPmag ?=99.99 PanSTARRs r-band magnitude
(Kaiser et al. 2010SPIE.7733E..0EK,
Cat. II/349 )
251-257 F7.4 mag e_rPmag ?=99.99 Error on rPmag
259-265 F7.4 mag iPmag ?=99.99 PanSTARRs i-band magnitude
(Kaiser et al. 2010SPIE.7733E..0EK,
Cat. II/349 )
267-273 F7.4 mag e_iPmag ?=99.99 Error on iPmag
275-281 F7.4 mag zPmag ?=99.99 PanSTARRs z-band magnitude
(Kaiser et al. 2010SPIE.7733E..0EK,
Cat. II/349 )
283-289 F7.4 mag e_zPmag ?=99.99 Error on zPmag
291-297 F7.4 mag yPmag ?=99.99 PanSTARRs y-band magnitude
(Kaiser et al. 2010SPIE.7733E..0EK,
Cat. II/349 )
299-305 F7.4 mag e_yPmag ?=99.99 Error on yPmag
307-315 F9.6 mag umag ?=99.99 SDSS u band magnitude
(Ahn et al. 2012ApJS..203...21A 2012ApJS..203...21A, Cat. V/139)
317-328 F12.9 mag e_umag ?=99.99 Error on umag
330-339 F10.7 mag gmag ?=99.99 SDSS g band magnitude
(Ahn et al. 2012ApJS..203...21A 2012ApJS..203...21A, Cat. V/139)
341-352 F12.9 mag e_gmag ?=99.99 Error on gmag
354-362 F9.6 mag rmag ?=99.99 SDSS r band magnitude
(Ahn et al. 2012ApJS..203...21A 2012ApJS..203...21A, Cat. V/139)
364-375 F12.9 mag e_rmag ?=99.99 Error on rmag
377-385 F9.6 mag imag ?=99.99 SDSS i band magnitude
(Ahn et al. 2012ApJS..203...21A 2012ApJS..203...21A, Cat. V/139)
387-398 F12.9 mag e_imag ?=99.99 Error on imag
400-408 F9.6 mag zmag ?=99.99 SDSS z band magnitude
(Ahn et al. 2012ApJS..203...21A 2012ApJS..203...21A, Cat. V/139)
410-421 F12.9 mag e_zmag ?=99.99 Error on xmag
423-430 F8.3 km/s U U component of space velocity
432-437 F6.3 km/s e_U Error on U
439-446 F8.3 km/s V V component of space velocity
448-453 F6.3 km/s e_V Error on V
455-462 F8.3 km/s W W component of space velocity
464-469 F6.3 km/s e_W Error on W
471-478 F8.5 mag YMKOmag ?=0. Y-band magnitude from the UK Infrared
Telescope (UKIRT) on Mauna Kea Observatory
(MKO) (Dye et al. 2018MNRAS.473.5113D 2018MNRAS.473.5113D)
480-486 F7.5 mag e_YMKOmag ?=0. Error on YMKOmag
488-495 F8.5 mag JMKOmag ?=0. J-band magnitude from the UK Infrared
Telescope (UKIRT) on Mauna Kea Observatory
(MKO) (Dye et al. 2018MNRAS.473.5113D 2018MNRAS.473.5113D)
497-503 F7.5 mag e_JMKOmag ?=0. Error on JMKOmag
505-512 F8.5 mag HMKOmag ?=0. H-band magnitude from the UK Infrared
Telescope (UKIRT) on Mauna Kea Observatory
(MKO) (Dye et al. 2018MNRAS.473.5113D 2018MNRAS.473.5113D)
514-520 F7.5 mag e_HMKOmag ?=0. Error on HMKOmag
522-529 F8.5 mag KMKOmag ?=0. K-band magnitude from the UK Infrared
Telescope (UKIRT) on Mauna Kea Observatory
(MKO) (Dye et al. 2018MNRAS.473.5113D 2018MNRAS.473.5113D)
531-537 F7.5 mag e_KMKOmag ?=0. Error on KMKOmag
539-546 F8.5 mag YVIRmag ?=0. Y band magnitude from VISTA Hemisphere
Survey (McMahon et al. 2013Msngr.154...35M 2013Msngr.154...35M,
Cat. II/359)
548-554 F7.5 mag e_YVIRmag ?=0. Error on YVIRmag
556-563 F8.5 mag JVIRmag ?=0. J band magnitude from VISTA Hemisphere
Survey (McMahon et al. 2013Msngr.154...35M 2013Msngr.154...35M,
Cat. II/359)
565-571 F7.5 mag e_JVIRmag ?=0. Error on JVIRmag
573-580 F8.5 mag HVIRmag ?=0. H band magnitude from VISTA Hemisphere
Survey (McMahon et al. 2013Msngr.154...35M 2013Msngr.154...35M,
Cat. II/359)
582-588 F7.5 mag e_HVIRmag ?=0. Error on HVIRmag
590-597 F8.5 mag KsVIRmag ?=0. Ks band magnitude from VISTA Hemisphere
Survey (McMahon et al. 2013Msngr.154...35M 2013Msngr.154...35M,
Cat. II/359)
599-605 F7.5 mag e_KsVIRmag ?=0. Error on KsVIRmag
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name Star name (JHHMMSS.ss+DDMMSS.s)
21- 26 A6 --- SpType ?=- Spectral type
28- 39 A12 --- Comp Preferred composition (1)
41- 45 I5 K Teff Best-fitting effective temperature
47- 50 I4 K e_Teff Error on Teff
52- 56 F5.3 Msun Mstar Best-fitting white dwarf mass
58- 62 F5.3 Msun E_Mstar Upper error on Mstar
64- 68 F5.3 Msun e_Mstar Lower error on Mstar
70- 74 F5.3 [cm/s2] logg Best-fitting surface gravity
76- 80 F5.3 [cm/s2] E_logg Upper error on logg
82- 86 F5.3 [cm/s2] e_logg Lower error on logg
88- 92 I5 Myr cAge Best-fitting cooling age
94- 97 I4 Myr E_cAge Upper error on cAge
99-102 I4 Myr e_cAge Lower error on cAge
104-107 F4.1 Gyr Age ? Total age based on the pre-white dwarf
evolutionary lifetimes (2)
109-111 F3.1 Gyr E_Age ? Upper error on Age
113-115 F3.1 Gyr e_Age ? Lower error on Age
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Note (1): We inspected the model fits for all 142 targets and decided on the
atmospheric composition based on the Hα line profiles (if
available), the quality of the fits for all of the photometric bands,
and the presence or absence of a near-infrared flux deficit due to
molecular hydrogen.
We cannot distinguish between the pure H or pure He atmosphere
solutions for 70 targets, as both sets of models provide acceptable
fits to the observed SEDs. We present both H and He atmosphere
solutions for these 70 objects.
Note (2): Kalirai (2012Natur.486...90K 2012Natur.486...90K) used the recently formed white dwarfs
in the 12.5Gyr old globular cluster M4 and the results from a Hubble
Space Telescope imaging survey of 60 globular clusters
(Sarajedini et al. 2007AJ....133.1658S 2007AJ....133.1658S, Cat. J/AJ/133/1658) to derive
a relation that links the mass of remnants forming today to the parent
population's age: log(Age)=(log(Mstar+0.270)-0.201)/-0.272 Gyr.
Note that this equation overestimates the total ages for the coolest
white dwarfs.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 23-Jun-2022