N_H - N_HI correlation in Gigahertz-peaked-spectrum galaxies

TL;DR

This study reveals a significant positive correlation between total and neutral hydrogen column densities in X-ray emitting GPS/CSO galaxies, indicating a link between their radio and X-ray absorbing gas properties.

Contribution

It provides the first combined radio and X-ray analysis of GPS/CSO galaxies, quantifying the $N_{H} - N_{HI}$ relation with Bayesian methods and revealing its intrinsic spread.

Findings

Significant positive $N_{H} - N_{HI}$ correlation found.

Quantified the relation with Bayesian approach, $b=0.93^{+0.49}_{-0.33}$.

Indicates a physical connection between radio and X-ray absorbing gas.

Abstract

With the Westerbork Synthesis Radio Telescope, we performed HI observations of a sample of known X-ray emitting Gigahertz-peaked-spectrum galaxies with compact-symmetric-object morphology (GPS/CSOs) that lacked an HI absorption detection. We combined radio and X-ray data of the full sample of X-ray emitting GPS/CSOs and found a significant, positive correlation between the column densities of the total and neutral hydrogen ($N_{\rm H}$ and $N_{\rm HI}$, respectively). Using a Bayesian approach, we simultaneously quantified the parameters of the $N_{\rm H} - N_{\rm HI}$ relation and the intrinsic spread of the data set. For a specific subset of our sample, we found $N_{\rm H} \propto N_{\rm HI}^b$, with $b=0.93^{+0.49}_{-0.33}$, and $\sigma_{int} (N_{\rm H})= 1.27^{+1.30}_{-0.40}$. The $N_{\rm H} - N_{\rm HI}$ correlation suggests a connection between the physical properties of the radio and X-ray absorbing gas.