Rutgers University Astrophysics Seminar

X-ray emission from star-forming galaxies, consisting primarily of emission from accreting black holes and neutron stars (i.e., X-ray binaries) and the hot interstellar medium, is a key tracer of processes like the physics of accretion onto compact objects and the chemical enrichment and feedback which shape galaxies. In the early Universe, high energy emission from X-ray binaries and/or shocks may provide an important contribution to the ionizing photon budget in extreme emission line galaxies, while the high energy photons that emerge from such galaxies may play a role in heating the intergalactic medium prior to the epoch of reionization. Unfortunately, we cannot directly measure the intrinsic or emergent X-ray spectral energy distributions (SEDs) from the earliest star-forming galaxies; thus, we must rely on galaxies in the local Universe as proxies to provide a window to the key attributes of the X-ray SED and elucidate their importance across cosmic time. I will present work using primarily Chandra, XMM-Newton, and NuSTAR observations of relatively nearby (D < 100 Mpc) star-forming galaxies to characterize the dominant components of the emergent X-ray SED and their scaling with metallicity, stellar population age, and star formation rate. Building on this understanding of the X-ray SED, I will also present recent work using photoionization modeling to predict the nebular emission contribution from composite stellar population and X-ray binary SEDs as a function of starburst age and metallicity. I will discuss this work in the context of future prospects for constraining the demographics of extragalactic compact object populations and the importance of accounting for sources of X-ray emission when considering production of high ionization emission lines and structure formation in the early Universe.