Stellar population models based on the SDSS-IV MaStar library of stellar spectra. I. Intermediate-age/old models

TL;DR

This paper introduces new stellar population models based on the SDSS-IV MaStar library, covering a broad range of ages and metallicities, validated against globular clusters and galaxy spectra, enhancing spectral modeling accuracy.

Contribution

The study presents the first models using MaStar spectra with expanded parameter coverage, including low-metallicity and young populations, and introduces a novel on-the-fly parameter reliability testing method.

Findings

Models recover globular cluster ages and metallicities with low systematics.

Fitted a MaNGA galaxy spectrum with residuals of a few percent.

Extended wavelength coverage improves spectral fitting accuracy.

Abstract

We use the first release of the SDSS/MaStar stellar library comprising ~9000, high S/N spectra, to calculate integrated spectra of stellar population models. The models extend over the wavelength range 0.36-1.03 micron and share the same spectral resolution (R~1800) and flux calibration as the SDSS-IV/MaNGA galaxy data. The parameter space covered by the stellar spectra collected thus far allows the calculation of models with ages and chemical composition in the range t>200 Myr, -2 <=[Z/H]<= + 0.35, which will be extended as MaStar proceeds. Notably, the models include spectra for dwarf Main Sequence stars close to the core H-burning limit, as well as spectra for cold, metal-rich giants. Both stellar types are crucial for modelling lambda>0.7 micron absorption spectra. Moreover, a better parameter coverage at low metallicity allows the calculation of models as young as 500 Myr and the full account of the Blue Horizontal Branch phase of old populations. We present models adopting two independent sets of stellar parameters (T_eff, logg, [Z/H]). In a novel approach, their reliability is tested 'on the fly' using the stellar population models themselves. We perform tests with Milky Way and Magellanic Clouds globular clusters, finding that the new models recover their ages and metallicities remarkably well, with systematics as low as a few per cent for homogeneous calibration sets. We also fit a MaNGA galaxy spectrum, finding residuals of the order of a few per cent comparable to the state-of-art models, but now over a wider wavelength range.