J/MNRAS/494/3342 Stellar parameters from GALANTE (Lorenzo-Gutierrez+, 2020)
Deriving stellar parameters from GALANTE photometry: bias and precision.
Lorenzo-Gutierrez A., Alfaro E.J., Maiz Apellaniz J., Barba R.H.,
Marin-Franch A., Ederoclite A., Cristobal-Hornillos D., Varela J.,
Vazquez Ramio H., Cenarro A.J., Lennon D.J., Garcia-Lario P., Daflon S.,
Borges Fernandes M.
<Mon. Not. R. Astron. Soc., 494, 3342-3357 (2020)>
=2020MNRAS.494.3342L 2020MNRAS.494.3342L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, fundamental ; Milky Way ; Effective temperatures ;
Abundances, [Fe/H] ; Extinction ; Optical ; Models
Keywords: techniques: photometric; stars: formation
stars: fundamental parameters; galaxies: star formation
Abstract:
In this paper, we analyse how to extract the physical properties from
the GALANTE photometry of a stellar sample. We propose a direct
comparison between the observational colours (photometric bands
normalized to the 515nm central wavelength) and the synthetic colours
derived from different stellar libraries. We use the reduced χ2
as the figure of merit for selecting the best fitting between both
colour sets. The synthetic colours of the Next Generation Spectral
Library (NGSL) provide a valuable sample for testing the uncertainty
and precision of the stellar parameters derived from observational
data. Reddening, as an extrinsic stellar physical parameter becomes a
crucial variable for accounting for the errors and bias in the derived
estimates: the higher the reddenings, the larger the errors and
uncertainties in the derived parameters. NGSL colours also enable us
to compare different theoretical stellar libraries for the same set of
physical parameters, where we see how different catalogues of models
can provide very different solutions in a, sometimes, non-linear way.
This peculiar behaviour makes us to be cautious with the derived
physical parameters obtained from GALANTE photometry without previous
detailed knowledge of the theoretical libraries used to this end. In
addition, we carry out the experiment of deriving physical stellar
parameters from some theoretical libraries, using some other libraries
as observational data. In particular, we use the Kurucz and Coelho
libraries, as input observational data, to derive stellar parameters
from Coelho + TLUSTY and Kurucz + TLUSTY stellar libraries,
respectively, for different photometric errors and colour excesses.
Description:
The GALANTE project is mainly designed for the study of the Galactic
disc (Maiz Apellaniz 2017edrs.confE..15M; Lorenzo-Gutierrez et al.
2019MNRAS.486..966L 2019MNRAS.486..966L; Maiz Apellaniz et al. 2019hsax.conf..346M). Thus,
the set of theoretical models that will be used to determine the
physical parameters of the sample objects should be focused mainly on
the most characteristic stars of this Galactic subsystem. To this end,
we select the Coelho low-resolution (Coelho 2014MNRAS.440.1027C 2014MNRAS.440.1027C),
Kurucz (Castelli, Gratton & Kurucz 1997A&A...318..841C 1997A&A...318..841C), and TLUSTY
OSTAR2002 (Lanz & Hubeny 2003ApJS..146..417L 2003ApJS..146..417L) theoretical libraries.
We have chosen the NGSL library (Gregg et al. 2006hstc.conf..209G),
which comprises spectra for 378 stars, covering the spectral range
from 0.2 to 1.0µm well calibrated in flux. This catalogue covers a
range of 3100=<Teff=<32900K, 0.4=<logg=<5.4dex, and -2.0=<[Fe/H]=<0.5
and E(B-V) from 0 to 0.75. One can see how the physical stellar
parameters of this observational library are representative of the
three major subsystems of the Galaxy.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 60 291 NGSL table
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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- 9 A9 --- Name Star name
11- 15 I5 K iTeff Input effective temperature
17- 21 I5 K oTeff Output effective temperature
23- 26 F4.2 [cm/s2] ilogg Input surface gravity
28- 31 F4.2 [cm/s2] ologg Output surface gravity
33- 37 F5.2 [-] i[Fe/H] Input Fe/H abundance ratio
39- 43 F5.2 [-] o[Fe/H] Output Fe/H abundance ratio
45- 48 F4.2 mag iE(B-V) Input (B-V) color excess
50- 53 F4.2 mag oE(B-V) Output (4405-5495) color excess
55- 60 F6.2 --- chi2 Reduced chi-squared
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 31-May-2023