GALEX Catalog of UV Point Sources in M33

TL;DR

This paper updates the UV point source catalog of M33 using GALEX data, providing a comprehensive multi-wavelength dataset that includes photometry from UV to optical for thousands of sources, including known Wolf-Rayet stars.

Contribution

It introduces an improved UV catalog of M33 with PSF photometry and expanded wavelength coverage, enhancing the identification and analysis of hot, massive stars in the galaxy.

Findings

Recovered 114 of 206 known Wolf-Rayet stars with UV counterparts.

Created a catalog of 24,738 sources with multi-band photometry.

Identified sources with unique colors and well-studied objects in M33.

Abstract

The hottest stars ($>$10,000 K), and by extension typically the most massive ones, are those that will be prevalent in the ultraviolet (UV) portion of the electromagnetic spectrum, and we expect numerous B, O, and Wolf-Rayet stars to be bright in UV data. In this paper, we update the previous UV catalog of M33, created using the Ultraviolet Imaging Telescope (UIT), using data from the Galaxy Evolution Explorer (GALEX). We utilize PSF photometry to better handle the crowded regions in the galaxy, and benefit from GALEX's increased sensitivity compared to UIT. We match our detections with data from the Local Group Galaxies Survey (LGGS) to create a catalog with photometry spanning from the far-UV through the optical for a final list of 24738 sources. All of these sources have far-UV (FUV; 1516A), near-UV (NUV; 2267A), and V data, and a significant fraction also have U, B, R, and I data as well. We compare these sources to a catalog of known Wolf-Rayet stars in M33 and find that we recover 114 of 206 stars with spatially-coincident UV objects. Additionally, we highlight and investigate those sources with unique colors as well as a selection of other well-studied sources in M33.