J/A+A/685/A59 VMP stars [Fe/H] estimates in GSP-Spec catalog (Matsuno+, 2024)
Improving metallicity estimates for very metal-poor stars in the Gaia DR3
GSP-Spec catalog.
Matsuno T., Starkenburg E., Balbinot E., Helmi A.
<Astron. Astrophys. 685, A59 (2024)>
=2024A&A...685A..59M 2024A&A...685A..59M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, metal-deficient ; Abundances, [Fe/H] ; Equivalent widths
Keywords: methods: data analysis - catalogs - stars: abundances -
stars: Population II
Abstract:
In the latest Gaia data release (DR3), the GSP-Spec module has
provided stellar parameters and chemical abundances measured from the
RVS spectra alone. However, the GSP-Spec parameters, including
metallicity, for very metal-poor stars (VMP stars; [Fe/H]←2) suffer
from parameter degeneracy due to a lack of information in their
spectra, and hence have large measurement uncertainty and systematic
offset. We aim to provide more precise metallicity estimates for VMP
stars analysed by the GSP-Spec module by taking photometric
information into account in the analysis and breaking the degeneracy.
We reanalyzed FGK type stars in the GSP-Spec catalog by computing the
Ca triplet equivalent widths from the published set of GSP-Spec
stellar parameters. We compare these recovered equivalent widths with
the values directly measured from public Gaia RVS spectra and
investigate the precision of the recovered values and the parameter
range in which the recovered values are reliable. We then convert the
recovered equivalent widths to metallicities adopting photometric
temperatures and surface gravities that we derive based on Gaia and
2MASS catalogs. The recovered equivalent widths agree with the
directly measured values with a scatter of 0.05dex for the stars that
pass the GSP-Spec quality cuts. Among stars that were recommended to
filter out, we observed a similar scatter for FGK-type stars initially
misidentified as hot stars. Contrarily, we found a poorer agreement in
general for stars that the GSP-Spec identified as cool K and M-type
giants, although we can still define subsets that show reasonable
agreement. At the low metallicity end ([Fe/H]←1.5), our metallicity
estimates have a typical uncertainty of 0.18dex, which is about half
of the quoted GSP-Spec metallicity uncertainty at the same
metallicity. Our metallicities also show better agreement with the
high-resolution literature values than the original GSP-Spec
metallicities at low metallicity; the scatter in the comparison
decreases from 0.36-0.46dex to 0.17-0.29dex for stars that satisfy the
GSP-Spec quality cuts. While the GSP-Spec metallicities show
increasing scatter when misidentified "hot" stars and the subsets of
the "cool K and M-type giants" are included (up to 1.06dex), we can
now identify them as FGK-type stars and provide metallicities that
show a small scatter in the comparisons (up to 0.34dex), which helps
us to increase the number of VMP stars with reliable and precise
metallicity. The inclusion of photometric information greatly
contributes to breaking parameter degeneracy, enabling precise
metallicity estimates for VMP stars from Gaia RVS spectra. We produce
a publicly-available catalog of bright metal-poor stars suitable for
high-resolution follow-up. The sample contains about 2345 VMP stars
with an estimated contamination rate of 5%.
Description:
The catalog contains our new metallicity estimates for stars in the
GSP-Spec catalog. Stellar parameters are rederived from photometry and
astrometry. Metallicity estimates are based on these new stellar
parameters and inferred equivalent widths of the Ca triplet lines. See
the paper for details. We also include information about quality flags
and the information used to derive the stellar parameters for
convinience.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 124 4733027 The catalog
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Gaia DR3 source_id
21- 35 F15.11 deg RAdeg Gaia DR3 right ascension (ICRS)
at Ep=2016.0
37- 51 F15.11 deg DEdeg Gaia DR3 declination (ICRS) at Ep=2016.0
53- 58 F6.1 K Teff Effective temperature adopted in this work
60- 65 F6.3 [cm/s2] logg Surface gravity adopted in this work
67- 72 F6.3 [Sun] [Fe/H] Metallicity derived in this work
74- 78 F5.3 [Sun] e_[Fe/H] Metallicity uncertainty derived in
this work
80- 85 F6.3 [0.1nm] log(EW8498) Inferred equivalent width for the
8498Å line
87- 91 F5.3 [0.1nm] log(EW8542) ?=- Inferred equivalent width for the
8542Å line
93- 97 F5.3 [0.1nm] log(EW8662) ?=- Inferred equivalent width for the
8662Å line
99 I1 --- MPp [0/1] MP+ flag defined in the paper (1)
101 I1 --- RMP [0/1] RMP flag defined in the paper (2)
103 I1 --- eRMP1 [0/1] eRMP1 flag defined in the paper (3)
105 I1 --- eRMP2 [0/1] eRMP2 flag defined in the paper (4)
107-108 A2 --- RefPhot Photometry used for the luminosity
110-114 F5.2 mag E(B-V) E(B-V) on the SFD scale
116-118 A3 --- r_E(B-V) Source of E(B-V) (5)
120-124 A5 --- r_Teff Color used to derive Teff
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Note (1): MP+ sample, which is combination of the filters by
Recio-Blanco et al. (2023A&A...674A..29R 2023A&A...674A..29R) and filtering on photometric
parameters:
3500≤Teff,gspspec≤6000
log ggspspec≤4.9
Teff,gspspec≥4150 or logggspspec≤2.4 or logggspspec≥3.8
vbroad[TGM]=0 and vrad[TGM]=0
extrapol≤2
KMgiantPar=0
spectraltype_esphs is not O or B
2dphotogeo,med/(dphotogeo,hi-dphotgeo,lo)>3
E(B-V) < 0.72
Teff,photo<7000
Teff,photo>5000 or log gphoto < 3.0.
Note (2): RMP sample, which relaxes or removes some of the conditions in
the MP+ filtering:
3500≤Teff,gspspec
Teff,gspspec≤6000 or logggspspec≥(Teff,gspspec-6000)/1000+3
Teff,gspspec≥6000 or logggspspec≤4.9
Teff,gspspec≥4150 or logggspspec≤2.4 or logggspspec≥3.8
extrapol≤2
KMgiantPar=0
spectraltype_esphs is not O or B
2dphotogeo,med/(dphotogeo,hi-dphotgeo,lo)>3
E(B-V)<0.72
Teff,photo<7000
Teff,photo>5000 or loggphoto<3.0.
Note (3): eRMP1 sample, which extends the RMP sample by including some stars
with KMgiantPar flagged:
3500≤Teff,gspspec
Teff,gspspec≤6000 or logggspspec≥(Teff,gspspec-6000)/1000+3
Teff,gspspec≥6000 or logggspspec≤4.9
Teff,gspspec≥4150 or logggspspec≤2.4 or logggspspec≥3.8
extrapol≤2
KMgiantPar=0 or (KMgiantPar=1 and log and [M/H]gspspec>-3)
spectraltype_esphsis not O or B
2dphotogeo,med/(dphotogeo,hi-dphotgeo,lo)>3
E(B-V)<0.72
Teff,photo<7000
Teff,photo>5000 or loggphoto<3.0.
Note (4): eRMP2 sample, which further extends the eRMP1 sample by including
more stars with KMgiantPar flagged:
3500≤Teff,gspspec
Teff,gspspec≤6000 or logggspspec≥(Teff,gspspec-6000)/1000+3
Teff,gspspec≥6000 or logggspspec≤4.9
Teff,gspspec≥4150 or log ggspspec≤2.4 or log ggspspec≥3.8
extrapol≤2
KMgiantPar=0 or (KMgiantPar=1 and logxhigspspec2 and [M/H]gspspec>-3)
or (KMgiantPar=1 and [M/H]gspspec=-3.51)
spectraltype_esphs is not O or B
2dphotogeo,med/(dphotogeo,hi-dphotgeo,lo)>3
E(B-V)<0.72
Teff,photo<7000
Teff,photo>5000 or loggphoto<3.0.
Note (5): References as follows:
G19 = Green et al. (2019ApJ...887...93G 2019ApJ...887...93G)
M06 = Marshall et al. (2006A&A...453..635M 2006A&A...453..635M)
SFD = scaled Schlegel et al. (1998ApJ...500..525S 1998ApJ...500..525S)
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Acknowledgements:
Tadafumi Matsuno, matsunouni(at)uni-heildelberg.de
(End) Patricia Vannier [CDS] 07-Feb-2024