Probing the physical properties of the intergalactic medium using blazars

Understand

We use Swift blazar spectra to estimate the key intergalactic medium (IGM) properties of hydrogen column density(Nhxigm), metallicity and temperature over a redshift range of 0.03 leq z leq 4.7, using a collisional ionisation equilibrium(CIE) model for the ionised plasma.

• We adopted a conservative approach to the blazar continuum model given its intrinsic variability and use a range of power law models.
• We subjected our results to a number of tests and found that the Nhxigm parameter was robust with respect to individual exposure data and co-added spectra for each source, and between Swift and XMM-Newton source data.
• We also found no relation between Nhxigm and variations in source flux or intrinsic power laws.