Stellar populations in the outskirts of M31: the mid-infrared view

TL;DR

This study uses mid-infrared observations from Spitzer/IRAC to analyze the stellar populations in the outskirts of M31, revealing insights into the galaxy's structure and individual dusty stars.

Contribution

It provides the first extensive mid-infrared survey of M31's outskirts, combining surface brightness and star count profiles with a catalog of individual sources.

Findings

Surface brightness profile is difficult to trace in outskirts.

Star count profile reveals disk/halo transition.

Catalog of mid-infrared properties of individual objects.

Abstract

The mid-infrared provides a unique view of galaxy stellar populations, sensitive to both the integrated light of old, low-mass stars and to individual dusty mass-losing stars. We present results from an extended Spitzer/IRAC survey of M31 with total lengths of 6.6 and 4.4 degrees along the major and minor axes, respectively. The integrated surface brightness profile proves to be surprisingly diffcult to trace in the outskirts of the galaxy, but we can also investigate the disk/halo transition via a star count profile, with careful correction for foreground and background contamination. Our point-source catalog allows us to report on mid-infrared properties of individual objects in the outskirts of M31, via cross-correlation with PAndAS, WISE, and other catalogs.