TY - JOUR

T1 - SDSS-IV MaStar

T2 - Stellar parameter determination with continuum-supplemented full-spectrum fitting

AU - Lazarz, Daniel

AU - Yan, Renbin

AU - Wilhelm, Ronald

AU - Chen, Yanping

AU - Hill, Lewis

AU - Holtzman, Jon A.

AU - Imig, Julie

AU - Maraston, Claudia

AU - Mészáros, Szabolcs

AU - Stringfellow, Guy S.

AU - Thomas, Daniel

AU - Beers, Timothy C.

AU - Bizyaev, Dmitry

AU - Drory, Niv

AU - Lane, Richard R.

AU - Nitschelm, Christian

N1 - 22 pages, 21 figures. A&A in press

PY - 2022/10/24

Y1 - 2022/10/24

N2 - Aims: We present a stellar parameter catalog built to accompany the MaStar Stellar Library, which is a comprehensive collection of empirical, medium-resolution stellar spectra.Methods: We constructed this parameter catalog by using a multicomponent χ2 fitting approach to match MaStar spectra to models generated by interpolating the ATLAS9-based BOSZ model spectra. The total χ2 for a given model is defined as the sum of components constructed to characterize narrow-band features of observed spectra (e.g., absorption lines) and the broadband continuum shape separately. Extinction and systematics due to flux calibration were taken into account in the fitting. The χ2 distribution for a given region of model space was sampled using a Markov chain Monte Carlo (MCMC) algorithm, the data from which were then used to extract atmospheric parameter estimates (Teff, log g, [Fe/H], and [α/Fe]), their corresponding uncertainties, and direct extinction measurements.Results: Two methods were used to extract parameters and uncertainties: one that accepts the MCMC’s prescribed minimum-χ2 result, and one that uses Bayesian inference to compute a likelihood-weighted mean from the χ2 distribution sampled by the MCMC. Results were evaluated for internal consistency using repeat observations where available and by comparing them with external data sets (e.g., APOGEE-2 and Gaia DR2). Our spectral-fitting exercise reveals possible deficiencies in current theoretical model spectra, illustrating the potential power of MaStar spectra for helping to improve the models. This paper represents an update to the parameters that were originally presented with SDSS-IV DR17. The MaStar parameter catalog containing our BestFit results is available on the SDSS-IV DR17 website as part of version 2 of the MaStar stellar parameter value-added catalog.

AB - Aims: We present a stellar parameter catalog built to accompany the MaStar Stellar Library, which is a comprehensive collection of empirical, medium-resolution stellar spectra.Methods: We constructed this parameter catalog by using a multicomponent χ2 fitting approach to match MaStar spectra to models generated by interpolating the ATLAS9-based BOSZ model spectra. The total χ2 for a given model is defined as the sum of components constructed to characterize narrow-band features of observed spectra (e.g., absorption lines) and the broadband continuum shape separately. Extinction and systematics due to flux calibration were taken into account in the fitting. The χ2 distribution for a given region of model space was sampled using a Markov chain Monte Carlo (MCMC) algorithm, the data from which were then used to extract atmospheric parameter estimates (Teff, log g, [Fe/H], and [α/Fe]), their corresponding uncertainties, and direct extinction measurements.Results: Two methods were used to extract parameters and uncertainties: one that accepts the MCMC’s prescribed minimum-χ2 result, and one that uses Bayesian inference to compute a likelihood-weighted mean from the χ2 distribution sampled by the MCMC. Results were evaluated for internal consistency using repeat observations where available and by comparing them with external data sets (e.g., APOGEE-2 and Gaia DR2). Our spectral-fitting exercise reveals possible deficiencies in current theoretical model spectra, illustrating the potential power of MaStar spectra for helping to improve the models. This paper represents an update to the parameters that were originally presented with SDSS-IV DR17. The MaStar parameter catalog containing our BestFit results is available on the SDSS-IV DR17 website as part of version 2 of the MaStar stellar parameter value-added catalog.

KW - astro-ph.GA

KW - astro-ph.IM

KW - astro-ph.SR

KW - stars: abundances

KW - stars: atmospheres

KW - Hertzsprung–Russell and C–M diagrams

KW - methods: data analysis

U2 - 10.1051/0004-6361/202243701

DO - 10.1051/0004-6361/202243701

M3 - Article

SN - 0004-6361

VL - 688

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A21

ER -