Stellar populations in a standard ISOGAL field in the Galactic disk

TL;DR

This study characterizes stellar populations, including red giants and young stars, in a specific Galactic disk field using ISOGAL, 2MASS, and GLIMPSE data, establishing a standard analysis method and identifying over-densities related to spiral arms.

Contribution

It introduces a standard approach for analyzing ISOGAL disk observations and combines multi-survey data to identify and characterize stellar populations in the Galactic plane.

Findings

Identified several hundred RGB/AGB stars and 22 candidate young stellar objects.

Detected over-density of sources at the distance of the Scutum-Crux spiral arm.

Estimated mass-loss rates of AGB stars using dust radiative transfer models.

Abstract

We aim to identify the stellar populations (mostly red giants and young stars) detected in the ISOGAL survey at 7 and 15micron towards a field (LN45) in the direction l=-45, b=0.0. The sources detected in the survey of the Galactic plane by the Infrared Space Observatory are characterized based on colour-colour and colour-magnitude diagrams. We combine the ISOGAL catalog with the data from surveys such as 2MASS and GLIMPSE. Interstellar extinction and distance are estimated using the red clump stars detected by 2MASS in combination with the isochrones for the AGB/RGB branch. Absolute magnitudes are thus derived and the stellar populations are identified based on their absolute magnitudes and their infrared excess. A standard approach to the analysis of ISOGAL disk observations has been established. We identify several hundred RGB/AGB stars and 22 candidate young stellar objects in the direction of this field in an area of 0.16 deg^2. An over-density of stellar sources is found at distances corresponding to the distance of the Scutum-Crux spiral arm. In addition, we determine mass-loss rates of AGB-stars using dust radiative transfer models from the literature.