Candidate red supergiants from Gaia DR3 BPRP spectra: From the Perseus to the Scutum-Crux spiral arms

¹ Dipartimento di Fisica e Astronomia “Augusto Righi”, Alma Mater Studiorum, Università di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
² INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy

^★ Corresponding author: maria.messineo@inaf.it

Received: 25 January 2025
Accepted: 23 April 2025

Abstract

Context. Our position within the Galactic plane and the dust obscuration make it challenging to retrieve a true picture of the Milky Way’s morphology. While the Milky Way has been recognized as a barred spiral galaxy since the 1960s, there is still uncertainty about the exact number of spiral arms it contains. Currently, our understanding of the Galaxy is evolving thanks to the unprecedented detail provided by Gaia’s parallactic distances.

Aims. To shed light on the spatial distribution of red supergiants (RSGs) on the Disk and their uniformity of parameters across it, a census of Galactic RSGs detected by Gaia is needed.

Methods. Candidate RSGs were extracted from the combined Gaia DR3 and 2MASS catalogs using color criteria and parallactic distances. The sample includes 335 stars that were not included in catalogs of previously known RSGs detected by Gaia DR3. Interstellar and circumstellar extinction values were estimated from the infrared bands. Spectral types were collected from Simbad or VIZIER databases and, for 135 candidates, were inferred from the Gaia DR3 BPRP spectra. Stellar luminosities were inferred using photometric measurements and the Gaia DR3 distances.

Results. The analysis yielded a genuine sample of O-rich late-type stars, and the calculated luminosities confirm that the sample is mostly made of stars brighter than M_bol = −5 mag. This new sample represents a 40% increase in the number of highly probable RSGs compared to previous studies. When looking at the X and Y distribution on the Galactic plane, beside the populous Perseus associations of RSGs and the Sagittarius group of RSGs, a novel population of highly probable RSGs populating the more distant Scutum-Centaurus arm appears.