Critical New Constraints on Ulx and Luminous HMXB Populations in Extreme Metal Poor Galaxies

Recent studies have shown that the HMXB X-ray luminosity function scaling with SFR increases with declining metallicity. In the high-redshift Universe, when metallicities were relatively low and galaxies were more actively star-forming, HMXBs are expected to have dominated the X-ray emissivity of the Universe and could have provided an important source of IGM heating. We propose to conduct moderately-deep Chandra imaging of five extreme metal poor galaxies (XMPs), which have gas-phase metallicities in the range of 0.07-0.19 solar. These properties are comparable to those of typical z ~ 8 galaxies. We will increase the number of luminous HMXBs detected in XMPs by a factor of ~5 to significantly improve constraints on the X-ray scaling relations from this critical population.