J/A+A/651/A79 TO stars metallicity estimate (Bonifacio+, 2021)
TOPoS VI. The metal-weak tail of the metallicity distribution functions of the
Milky Way and the Gaia-Sausage-Enceladus structure.
Bonifacio P., Monaco L., Salvadori S., Caffau E., Spite M., Sbordone L.,
Spite F., Ludwig H.-G., Di Matteo P., Haywood M., Francois P.,
Koch-Hansen A.J., Christlieb N.C., Zaggia S.
<Astron. Astrophys. 651, A79 (2021)>
=2021A&A...651A..79B 2021A&A...651A..79B (SIMBAD/NED BibCode)
+2022A&A...666C...1B 2022A&A...666C...1B
ADC_Keywords: Milky Way ; Spectroscopy ; Abundances, [Fe/H]
Keywords: stars: Population II - stars: abundances - Galaxy: abundances -
Galaxy: halo
Abstract:
The goal of the Turn-Off Primordial Stars survey (TOPoS) project is to
find and analyse turn-off (TO) stars of extremely low metallicity. To
select the targets for spectroscopic follow-up at high spectral
resolution, we relied on low-resolution spectra from the Sloan Digital
Sky Survey (SDSS).
In this paper, we use the metallicity estimates we obtained from our
analysis of the SDSS spectra to construct the metallicity distribution
function (MDF) of the Milky Way, with special emphasis on its
metal-weak tail. The goal is to provide the underlying distribution
out of which the TOPoS sample was extracted.
We made use of SDSS photometry, Gaia photometry, and distance
estimates derived from the Gaia parallaxes to derive a metallicity
estimate for a large sample of over 24 million TO stars. This sample
was used to derive the metallicity bias of the sample for which SDSS
spectra are available.
We determined that the spectroscopic sample is strongly biased in
favour of metal-poor stars, as intended. A comparison with the
unbiased photometric sample allows us to correct for the selection
bias. We selected a sub-sample of stars with reliable parallaxes for
which we combined the SDSS radial velocities with Gaia proper motions
and parallaxes to compute actions and orbital parameters in the
Galactic potential. This allowed us to characterise the stars
dynamically, and in particular to select a sub-sample that belongs to
the Gaia-Sausage-Enceladus (GSE) accretion event. We are thus also
able to provide the MDF of GSE.
The metal-weak tail derived in our study is very similar to that
derived in the H3 survey and in the Hamburg/ESO Survey. This allows us
to average the three MDFs and provide an error bar for each
metallicity bin. Inasmuch as the GSE structure is representative of
the progenitor galaxy that collided with the Milky Way, that galaxy
appears to be strongly deficient in metal-poor stars compared to the
Milky Way, suggesting that the metal-weak tail of the latter has been
largely formed by accretion of low-mass galaxies rather than massive
galaxies, such as the GSE progenitor.
Description:
We made use of SDSS photometry, Gaia photometry, and distance
estimates derived from the Gaia parallaxes to derive a metallicity
estimate for a large sample of over 24 million TO stars. This sample
was used to derive the metallicity bias of the sample for which SDSS
spectra are available.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
photmet.dat 171 12894443 Stars of the photometric sample
(corrected version, 22-Aug-2022,
2022A&A...666C...1B 2022A&A...666C...1B)
specmet.dat 280 139493 Stars of the spectroscopic sample
actions.dat 252 57386 Sub-sample of the spectroscopic sample for which
orbital parameters have been computed
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See also:
J/A+A/579/A28 : Abundances of 3 CEMP stars (Bonifacio+, 2015)
J/A+A/620/A187 : Very metal-poor turn-off stars abundances (Francois+, 2018)
Byte-by-byte Description of file: photmet.dat
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Bytes Format Units Label Explanations
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1- 15 F15.11 deg RAdeg SDSS right ascension (J2000) (ra_SDSS)
17- 31 F15.11 deg DEdeg SDSS declination (J2000) (dec_SDSS)
33- 47 F15.11 deg GLON Galactic longitude (l)
49- 63 F15.11 deg GLAT Galactic latitude (b)
65- 75 F11.5 pc rgc Distance from the Galactic Centre (rgc)
77- 87 F11.5 pc zh Height above the Galactic plane (zh)
89- 97 F9.6 mag (g-z)0 Dereddened g-z SDSS colour (gz0)
99-106 F8.6 mag BP-RP0 Gaia DR2 (GBP-GRP) dereddened colour (bp_rp0)
108-116 F9.6 mag Gmag0 Gaia DR2 G dereddened magnitude (G0 )
118-126 F9.6 mag GMAG0 Absolute G magnitude (G0abs)
128-146 I19 --- GaiaDR2 Gaia DR2 identification (source_id)
148-154 F7.2 K Teff Effective temperature from (g-z)0 (teff)
156-159 F4.2 [cm/s2] logg Surface gravity (glog)
161-165 F5.2 [-] photmet Photometric metallicity estimated from
p, Teff (photmet) and log g
167-171 F5.2 [-] photmetc Corrected photometric metallicity see Fig. 6
in paper and related text (photmet_c)
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Byte-by-byte Description of file: specmet.dat
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1- 15 F15.11 deg RAdeg SDSS right ascension (J2000) (ra_SDSS)
17- 31 F15.11 deg DEdeg SDSS declination (J2000) (dec_SDSS)
33- 40 F8.5 mag umag SDSS u magnitude (UMAG)
42- 49 F8.5 mag gmag SDSS g magnitude (GMAG)
51- 58 F8.5 mag zmag SDSS z magnitude (ZMAG)
60- 68 F9.6 mag (g-z)0 (g-z)0 dereddened SDSS colour (GZ0)
70- 84 F15.11 deg RAGdeg Gaia DR2 Right ascension (J2000)
(ra_epoch2000)
86-100 F15.11 deg DEGdeg Gaia DR2 Declination (J2000)
(dec_epoch2000)
102-109 F8.4 mas plx ?=- Gaia DR2 parallax corrected for global
zero point (parallax)
111-116 F6.4 mas e_plx ?=- Gaia DR2 parallax error (parallax_error)
118-124 F7.5 mas pest Parallax estimated from rest
(Expression: 1000./rest) (pest)
126-135 F10.5 pc rest Estimated distance (Bailer Jones et al.,
2018AJ....156...58B 2018AJ....156...58B, Cat. I/347) (rest)
137-145 F9.6 mag Gmag0 Gaia DR2 G dereddened magnitude (G0 )
147-154 F8.6 mag BP-RP0 Gaia DR2 (GBP-GRP) dereddened colour (bp_rp0)
156-165 F10.6 mag GMAG0029 ?=- Absolute G magnitude using Gaia parallax
and global zero point -0.029 (G0absp029)
167-175 F9.6 mag GMAG0absd Absolute G magnitude using pest (G0absd)
177-182 F6.1 K Teff Effective temperature from (g-z)0 (TEFF)
184-187 F4.2 [cm/s2] logg Surface gravity (glog)
189-193 F5.2 --- [Fe/H]mygi Metallicity [Fe/H] from MyGIsFOS (FeH_mygi)
195-199 F5.2 --- e_[Fe/H]mygi ?=- Estimated error on [Fe/H]mygi (FE_ERR)
201-203 I3 --- Nspect ?=- Number of spectra coadded (NUMSPEC)
205-212 F8.6 mag p Reddening free index
p=(u-g)-0.5885914(g-z) (p)
214-218 F5.2 --- photmet Photometric metallicity estimated from p,
Teff and log g (photmet)
220-224 F5.2 --- photmetc Corrected photometric metallicity see Fig. 6
in paper and related text (photmet_c)
226-240 F15.11 deg GLON Galactic longitude (l)
242-256 F15.11 deg GLAT Galactic latitude (b)
258-268 F11.5 pc rgc Distance from the Galactic Centre (rgc)
270-280 F11.5 pc zh Height above the Galactic plane (zh)
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Byte-by-byte Description of file: actions.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- GaiaDR2 Gaia DR2 unique source identifier (source_id)
21- 35 F15.11 deg RAdeg Right ascension (J2000) (ra_epoch2000)
37- 51 F15.11 deg DEdeg Declination (J2000) (dec_epoch2000)
53- 58 F6.4 mas plx Gaia DR2 parallax corrected for global
zero point (plx)
60- 65 F6.4 mas e_plx Gaia DR2 parallax error (parallax_error)
67- 75 F9.3 mas/yr pmRA Gaia DR2 proper motion in RA (pmra)
77- 81 F5.3 mas/yr e_pmRA Gaia DR2 Standard error of proper motion
in RA (pmra_error)
83- 91 F9.3 mas/yr pmDE Gaia DR2 proper motion in DE(pmdec)
93- 97 F5.3 mas/yr e_pmDE Gaia DR2 Standard error of proper motion
in DE (pmdec_error)
99-106 F8.3 km/s RV SDSS DR12 radial velocity (VRAD)
108-114 F7.4 km/s e_RV SDSS DR12 error on radial velocity (VERR)
116-124 F9.5 kpc rap Galactic distance at apocentre (rap)
126-133 F8.5 kpc rperi Galactic distance at pericentre (rperi)
135-141 F7.5 --- e2 Eccentricity (e_2)
143-151 F9.5 kpc zmax Maximum distance from Galactic plane (zmax)
153-161 F9.1 km2/s2 E2a Energy per unit mass (E_2a)
163-170 F8.2 kpc.km/s Lz Angular momentum per unit mass (Lz)
172-182 E11.6 kpc.km/s Jr Radial action (Jr)
184-193 F10.6 kpc e_rap Error on rap (erap)
195-202 F8.6 kpc e_rperi Error on rperi (erperi)
204-211 F8.6 --- e_e2 Error on e2 (ee_2)
213-222 F10.6 kpc e_zmax Error on zmax (ezmax)
224-231 F8.2 km2/s2 e_E2a Error on E2a (eE_2a)
233-240 F8.3 kpc.km/s e_Lz Error on Lz (eLz)
242-252 E11.6 kpc.km/s e_Jr Error on Jr (eJr)
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Acknowledgements:
Piercarlo Bonifacio, piercarlo.bonifacio(at)obspm.fr
References:
Caffau et al., Paper I 2013A&A...560A..71C 2013A&A...560A..71C
Bonifacio et al., Paper II 2015A&A...579A..28B 2015A&A...579A..28B, Cat. J/A+A/579/A28
Caffau et al., Paper III 2016A&A...595L...6C 2016A&A...595L...6C
Bonifacio et al., Paper IV 2018A&A...612A..65B 2018A&A...612A..65B
Francois et al., Paper V 2018A&A...620A.187F 2018A&A...620A.187F, Cat. J/A+A/620/A187
History:
22-Jul-2021: on-line version
22-Aug-2022: corrected photmet.dat file
(End) Patricia Vannier [CDS] 15-Jun-2021