Correlation between X-Ray and Radio Absorption in Compact Radio Galaxies

• Published in: The Astrophysical journal Vol. 849; no. 1; pp. 34 - 51
• Main Authors: Ostorero, Luisa, Morganti, Raffaella, Diaferio, Antonaldo, Siemiginowska, Aneta, Stawarz, ukasz, Moderski, Rafal, Labiano, Alvaro
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.11.2017; IOP Publishing
• Subjects: Absorbers; ABSORPTION; Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Compact galaxies; COMPARATIVE EVALUATIONS; Correlation; Data acquisition; DENSITY; EMISSION; Emission analysis; Galaxies; galaxies: active; galaxies: ISM; galaxies: jets; HYDROGEN; Morphology; RADIO GALAXIES; radio lines: galaxies; radio lines: ISM; Radio sources (astronomy); RADIO TELESCOPES; SPECTRA; Spin temperature; Stars & galaxies; SYMMETRY; SYNTHESIS; Variation; X-ray emissions; X-RAY GALAXIES; X-rays: galaxies
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aa8ef6

Compact radio galaxies with a GHz-peaked spectrum (GPS) and/or compact-symmetric-object (CSO) morphology (GPS/CSOs) are increasingly detected in the X-ray domain. Their radio and X-ray emissions are affected by significant absorption. However, the locations of the X-ray and radio absorbers are still debated. We investigated the relationship between the column densities of the total ( ) and neutral ( ) hydrogen to statistically constrain the picture. We compiled a sample of GPS/CSOs including both literature data and new radio data that we acquired with the Westerbork Synthesis Radio Telescope for sources whose X-ray emission was either established or under investigation. In this sample, we compared the X-ray and radio hydrogen column densities, and found that and display a significant positive correlation with ∝ b, where b = 0.47 and b = 0.35, depending on the subsample. The - correlation suggests that the X-ray and radio absorbers are either co-spatial or different components of a continuous structure. The correlation displays a large intrinsic spread that we suggest to originate from fluctuations, around a mean value, of the ratio between the spin temperature and the covering factor of the radio absorber, .