Speaker
Description
We present comprehensive insights into the hydrogen density distribution from the local interstellar medium (ISM) to the intergalactic medium (IGM) using X-ray absorption techniques facilitated by the eROSITA all-sky survey (eRASS1). For the ISM, we precisely measured hydrogen column densities from X-ray spectra of coronal sources, matched with Gaia DR3 distance data, revealing a significant correlation with Galactic latitude and indicating a vertical decrease in ISM density away from the Galactic plane. Employing various density models, we constrained vertical height scales and created a 3D density map through Gaussian processing, uncovering small-scale structures and larger density regions, particularly around the Galactic Perseus arm and star-forming regions such as Orion and the Chamaeleon molecular complex. Moreover, such analysis allow us to probe the potential habitability of exoplanets orbiting such distant stars. Extending our analysis to the IGM, we examined blazar spectra from eRASS1 and XMM-Newton, fitting the continuum spectra with a log-parabolic model and an IONeq model for IGM absorption. This study of 147 SRG and 10 XMM-Newton sources found a clear trend of IGM-N(H) scaling with blazar redshift, with a mean hydrogen density at z = 0 of n0 = (2.75 ± 0.63)×10^−7 cm^−3, an average temperature of log(T/K) = 5.6 ± 0.6, and a mean metallicity of Z = 0.16 ± 0.09. These results underscore the substantial contribution of the IGM to the total absorption observed in blazar spectra, thereby enriching our understanding of the distribution and physical characteristics of baryonic matter across the cosmos.
