J/A+A/666/A58 Metal-poor stars identification method (Xylakis-Dornbusch+, 2022)
A method for identifying metal-poor stars with Gaia BP/RP spectra.
Xylakis-Dornbusch T., Christlieb N., Lind K., Nordlander T.
<Astron. Astrophys. 666, A58 (2022)>
=2022A&A...666A..58X 2022A&A...666A..58X (SIMBAD/NED BibCode)
ADC_Keywords: Models ; Spectroscopy ; Optical
Keywords: stars: Population III - surveys - stars: Population II -
stars: abundances - stars: late-type
Abstract:
We developed a metal-poor candidate selection method based on
flux-ratios from the BP/RP Gaia spectra, using simulated synthetic
spectra. We found a relation between the relative iron abundance and
the flux-ratio of the Ca H&K region to that of the Hβ line.
This relation is temperature and surface gravity dependent, and it
holds for stars with effective temperature 4800≤Teff≤6300K. We
applied it to noisy simulated synthetic spectra and inferred [Fe/H]
with an uncertainty σ≤0.65dex for -3.0≤[Fe/H]≤0.5 and
G=15-17mag, which is sufficient for reliably identifying stars at
[Fe/H]←2.0.
We predict that by selecting stars with inferred [Fe/H]≤-2.5dex, we
can retrieve 80% of the stars with [Fe/H]≤-3.0, and we have a success
rate of about 50%, i.e. 1 in 2 stars we select has [Fe/H]≤-3.0. We do
not take into account the effect of reddening, so our method should
only be applied to stars which are located in regions of low
extinction.
Description:
We present the flux-ratios and their respective astrophysical
parameters, which we used to construct our method to identify
metal-poor stars with Gaia BP/RP spectra. We also provide the
coefficients of our method, as well as the respective effective
temperatures and surface gravities, for which the coefficients are
applicable.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 41 8211 Flux-ratios and the respective astrophysical
parameters used to construct the method
in the paper
m_coeffs.dat 44 51 Coefficients of the metal-poor star
identification method
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- a/a [0/8210]
6- 13 F8.6 --- G/CaNIR Gaia G to CaNIR flux ratio
15- 22 F8.6 --- CaHK/Hbeta CaHK/Hbeta flux ratio
24- 27 I4 K Teff Effective temperature
29- 31 F3.1 [cm/s2] logg Surface gravity
33- 36 F4.1 [-] [Fe/H] Metallicity
38- 41 F4.1 [-] [C/Fe] Abundance [C/Fe]
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Byte-by-byte Description of file: m_coeffs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- a/a [0/50]
4- 12 F9.6 --- b b coefficient
14- 23 F10.6 --- c c coefficient
25- 33 F9.6 --- d d coefficient
35- 40 F6.1 K Teff Effective temperature
42- 44 F3.1 [cm/s2] logg Surface gravity
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Acknowledgements:
Theodora Xylakis-Dornbusch, txylaki(at)lsw.uni-heidelberg.de
LSW/ZAH, Universitat Heidelberg
(End) Theodora Xylakis-Dornbusch [LSW/ZAH], Patricia Vannier [CDS] 22-Jul-2022