Measuring feedback using the intergalactic medium state and evolution inferred from the soft X-ray background

We explore the intergalactic medium (IGM) as a potential source of the unresolved soft X-ray background (XRB) and the feasibility of extracting the IGM state and evolution from XRB observations. We build two analytical models, the continuum field model and the halo model, to calculate the IGM XRB mean flux, angular autocorrelation, and cross-correlation with galaxies. Our results suggest that the IGM may contribute a significant fraction to the unresolved soft XRB flux and correlations. We calibrated non-Gaussian errors estimated against our 512(3) moving mesh hydro simulation and estimate that the ROSAT All-Sky Survey plus Sloan Galaxy Photometric Redshift Survey would allow a similar to10% accuracy in the IGM XRB-galaxy cross-correlation power spectrum measurement for 800<l<5000 and a similar to20% accuracy in the redshift-resolved X-ray emissivity-galaxy cross-correlation power spectrum measurement for zless than or similar to0.5. At small scales, nongravitational heating, i.e., feedback, dominates over gravity and leaves unique signatures in the IGM XRB, which allows a comparable accuracy in the measurement of the amount of nongravitational heating and the length scales where nongravitational energy balances gravity.