X-ray Binaries, Metallicity, and Stochasticity: A Case Study of NGC 300

We present an analysis of the X-ray binary (XRB) population of the nearby galaxy NGC 300. Using a new Chandra/ACIS-I observation in conjunction with archival Chandra observations, and Hubble ACS and WFC, GALEX FUV, and Spitzer 24 micron imaging, we identify XRB candidates in NGC 300 and estimate the most probable metallicity of each XRB based on the measured metallicity gradient across the star-forming disk. The XRBs are then sorted into subsamples based on galactocentric distance, and X-ray luminosity functions down to ~10³⁶ erg/s are calculated and decomposed into high-mass (HMXB) and low-mass (LMXB) components. We find a pronounced increase in the integrated HMXB X-ray luminosity LX per unit SFR with decreasing metallicity that is steeper than reported in prior studies. We explore the possibility that galaxy-integrated studies “smear out” the true effects of metallicity on XRB scaling relations and assess the role that stochasticity may play in low-SFR, low-stellar mass host galaxies and sub-galactic regions.