Circumnuclear HI disks in radio galaxies: The case of Cen A and B2 0258+35

TL;DR

This study presents new HI observations of Cen A and B2 0258+35, revealing broad absorption features indicative of circumnuclear disks, and suggests these disks are key to understanding AGN fueling mechanisms.

Contribution

It provides evidence for circumnuclear HI disks in two radio galaxies, linking atomic and molecular gas structures and highlighting the need for higher resolution data.

Findings

Detection of broad HI absorption in both galaxies.

Evidence for circumnuclear disks in Cen A and B2 0258+35.

Implication of these disks in AGN fueling processes.

Abstract

New HI observations of the nearby radio-loud galaxies Centaurus A and B2 0258+35 show broad absorption (Delta_v=400km/s) against the unresolved nuclei. Both sources belong to the cases where blue- and redshifted absorption is observed at the same time. In previous Cen A observations only a relative narrow range of redshifted absorption was detected. We show that the data suggest in both cases the existence of a circumnuclear disk. For Cen A the nuclear absorption might be the atomic counterpart of the molecular circumnuclear disk that is seen in CO and H_2. Higher resolution observations are now needed to locate the absorption and to further investigate the structure and kinematics of the central region of the AGN and the way the AGN are fueled.