DARK MATTER MAY NOT BE SO DARK: Testing Massive Primordial Black Hole Dark Matter with Galactic X-Ray Emission

Abstract

Were primordial black holes (PBHs) to exist, they could constitute a significant portion of dark matter in our universe which could be explored through gravitational wave emission, gravitational lensing, and electromagnetic observations. Assuming PBHs as a dark matter candidate, we determine the X-ray emission they would radiate from accreting gas in their host galaxy by modeling the dark matter particles in the Romulus25 cosmological simulation as clusters of PBHs. Upon simulating such emission, we compare our X-Ray luminosity functions to those derived from observations with the Chandra X-Ray Telescope to constrain the abundance of PBHs compared to dark matter as a function of PBH mass spanning 10^-2 − 10^5 M . Our results highly constrain the most massive PBHs but leave a vast sea of stellar and sub-stellar mass PBHs unscathed by falling under the flux limitations of Chandra. Therefore, further studies are needed in such a mass regime to explore the possibility of PBHs as a considerable source of dark matter and black holes in our universe. The implications of such could have drastic impacts on our understanding of the composition, machinations, and evolution of our universe.