# SDSS-IV MaStar -- A Large and Comprehensive Empirical Stellar Spectral Library: First Release

## TL;DR

The MaStar library is a large, high-quality empirical stellar spectral library covering a broad range of stellar types, designed to improve stellar population analysis in galaxy surveys, with the first release containing 8,646 spectra of 3,321 stars.

## Contribution

This work introduces the first release of MaStar, a comprehensive stellar spectral library with extensive stellar-parameter coverage, optimized for stellar population synthesis and galaxy analysis.

## Key findings

- Contains 8,646 spectra of 3,321 stars.
- Achieves flux calibration accuracy within a few percent.
- Provides broad stellar-parameter coverage, especially for cool dwarfs and low-metallicity stars.

## Abstract

We present the first release of the MaNGA Stellar Library (MaStar), which is a large, well-calibrated, high-quality empirical library covering the wavelength range of 3,622-10,354A at a resolving power of R~1800. The spectra were obtained using the same instrument as used by the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) project, by piggybacking on the SDSS-IV/APOGEE-2N observations. Compared to previous empirical libraries, the MaStar library will have a higher number of stars and a more comprehensive stellar-parameter coverage, especially of cool dwarfs, low-metallicity stars, and stars with different [alpha/Fe], achieved by a sophisticated target selection strategy that takes advantage of stellar-parameter catalogs from the literature. This empirical library will provide a new basis for stellar population synthesis, and is particularly well-suited for stellar-population analysis of MaNGA galaxies. The first version of the library contains 8646 high-quality per-visit spectra for 3321 unique stars. Compared to photometry, the relative flux calibration of the library is accurate to 3.9% in g-r, 2.7% in r-i, and 2.2% in i-z. The data are released as part of Sloan Digital Sky Survey Data Release 15. We expect the final release of the library to contain more than 10,000 stars.