Chemical Properties of the Local Disk and Halo. II. Abundances of 3745 M dwarfs and Subdwarfs from Improved Model Fitting of Low-Resolution Spectra

TL;DR

This study improves a model-fit pipeline to analyze low-resolution spectra of 3745 M dwarfs/subdwarfs, revealing detailed stellar parameters, chemical abundances, and kinematic properties, enhancing understanding of their distribution in the Galaxy.

Contribution

The paper introduces an improved pipeline for stellar parameter estimation from low-resolution spectra, enabling detailed chemical and kinematic analysis of a large M dwarf/subdwarf sample.

Findings

Clear stratification of temperature and chemical parameters in the HR diagram.

Distribution of stars in [alpha/Fe] vs. [M/H] aligns with previous studies.

Identification of substructure in abundance-velocity diagrams.

Abstract

We present a model-fit pipeline to determine the stellar parameters of M-type dwarfs, which is an improvement upon our previous work described in Hejazi et al. 2020. We apply this pipeline to analyze the low-resolution (R~2000) spectra of 3745 M dwarfs/subdwarfs, collected at the MDM Observatory, Lick Observatory, Kitt Peak National Observatory, and Cerro Tololo Interamerican Observatory. We examine the variation of the inferred parameter values in the HR diagram constructed from their Gaia Early Data Release 3 (EDR3) parallaxes and optical magnitudes. We also study the distribution of our stars in the abundance diagram of [alpha/Fe] versus [M/H] and inspect the variation of their metallicity class, effective temperature, and surface gravity as well as their Galactic velocity components U, V, and W in this diagram. In addition, the analyses of the stars' projected motions in the two-dimensional UV, VW, and UW planes and the variation of their chemical parameters in these planes, and also their distribution in the abundance-velocity diagrams are important parts of this study. The precision of our model-fit pipeline is confirmed by the clear stratification of effective temperature and chemical parameters in the HR diagram, the similarity of the stars' distribution in the [alpha/Fe] versus [M/H] diagram and in the metallicity-velocity planes with those from other studies, revealing substructure in the abundance-velocity diagrams, and chemical homogeneity between the components of a set of binary systems.