N_H - N_HI correlation in Gigahertz-peaked-spectrum galaxies
  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.
