Identification of metal-poor stars using the artificial neural network

TL;DR

This paper presents a method using artificial neural networks to identify metal-poor stars and determine their properties from medium-resolution spectra, improving accuracy and enabling better galactic structure studies.

Contribution

The study introduces a neural network approach trained on a new spectral library to accurately estimate stellar parameters and absolute magnitudes, including for metal-poor stars.

Findings

Achieved 0.3 dex accuracy in [Fe/H] estimation

Extended neural network application to calibrate absolute magnitudes

Identified new metal-poor stars in the survey

Abstract

Identification of metal-poor stars among field stars is extremely useful for studying the structure and evolution of the Galaxy and of external galaxies. We search for metal-poor stars using the artificial neural network (ANN) and extend its usage to determine absolute magnitudes. We have constructed a library of 167 medium-resolution stellar spectra (R ~ 1200) covering the stellar temperature range of 4200 to 8000 K, log g range of 0.5 to 5.0, and [Fe/H] range of -3.0 to +0.3 dex. This empirical spectral library was used to train ANNs, yielding an accuracy of 0.3 dex in [Fe/H], 200 K in temperature, and 0.3 dex in log g. We found that the independent calibrations of near-solar metallicity stars and metal-poor stars decreases the errors in T_eff and log g by nearly a factor of two. We calculated T_eff, log g, and [Fe/H] on a consistent scale for a large number of field stars and candidate metal-poor stars. We extended the application of this method to the calibration of absolute magnitudes using nearby stars with well-estimated parallaxes. A better calibration accuracy for M_V could be obtained by training separate ANNs for cool, warm, and metal-poor stars. The current accuracy of M_V calibration is (+-)0.3 mag. A list of newly identified metal-poor stars is presented. The M_V calibration procedure developed here is reddening-independent and hence may serve as a powerful tool in studying galactic structure.