The LAMOST Spectroscopic Survey of Supergiants in M31 and M33

TL;DR

This study systematically identifies supergiants in M31 and M33 using LAMOST spectroscopic data, providing a large, well-characterized sample that aids understanding of stellar evolution and star formation in different galactic environments.

Contribution

The paper presents one of the largest spectroscopic samples of supergiants in M31 and M33, with detailed classification and contamination removal, based on LAMOST data and Gaia measurements.

Findings

Identified 199 supergiants in M31 and 84 in M33.

Classified supergiants into blue, yellow, and red types.

Provided a comprehensive catalog for future stellar evolution studies.

Abstract

We present systematic identifications of supergiants of M31/M33 based on massive LAMOST spectroscopic survey. Radial velocities of nearly 5000 photometrically selected M31/M33 supergiant candidates have been properly derived from the qualified spectra released in LAMOST DR10. By comparing their radial velocities with those predicted from the rotation curves of M31, as well as utilizing {\it Gaia} astrometric measurements to exclude foreground contaminations, 199 supergiant members in M31, including 168 `Rank1' and 31 `Rank2', have been successfully identified. This sample contains 62 blue supergiants (BSGs, all `Rank1'), 134 yellow supergiants (YSGs, 103 `Rank1' and 31 `Rank2') and 3 red supergiants (RSGs, all `Rank1'). For M33, we identify 84 supergiant members (56 `Rank1' and 28 `Rank2'), which includes 28 BSGs (all `Rank1'), 53 YSGs (25 `Rank1' and 28 `Rank2') and 3 RSGs (all `Rank1'). So far, this is one of the largest supergiant sample of M31/M33 with full optical wavelength coverage (3700 \textless $\lambda$ \textless 9100 \AA). This sample is valuable for understanding the star formation and stellar evolution under different environments.