The Sources of Extreme Ultraviolet and Soft X-ray Backgrounds

摘要: Radiation in the extreme ultraviolet (EUV) and soft X-ray holds clues to location of missing baryons, energetics stellar feedback processes, cosmic enrichment history. Additionally, EUV photons help determine ionization state most intergalactic circumgalactic metals, shaping rate at which gas cools. Unfortunately, this band is extremely difficult probe observationally due absorption from Galaxy. In paper, we model contributions various sources backgrounds. We bracket contribution (1) quasars, (2) binaries, (3) hot interstellar gas, (4) (5) virialized developing models that extrapolate into these bands using both empirical theoretical inputs. While quasars are traditionally assumed dominate backgrounds, discuss substantial uncertainty their contribution. Furthermore, find intrahalo gases likely emit an O(1) fraction radiation low redshifts, emission potentially contribute tens percent backgrounds all redshifts. estimate uncertainties angular-averaged background intensity impact corrections for common metal lines by ~0.3-1 dex, show local emissions comparable only r_prox = 10-100 kpc Milky Way-like galaxies.