VLBA Observations of HI in the Archetype Compact Symmetric Object B2352+495

TL;DR

This study uses VLBA observations of 21 cm HI absorption to analyze the circumnuclear environment of the archetype Compact Symmetric Object B2352+495, providing insights into its structure and the nature of its radio emission.

Contribution

First VLBA HI absorption study of B2352+495, confirming multiple absorption features and supporting the presence of circumnuclear material around the AGN.

Findings

Detected two HI absorption features, including a broad and a narrow component.

The broad absorption is likely associated with circumnuclear material.

Results support the presence of clumpy HI structures around the supermassive black hole.

Abstract

B2352+495 is a prototypical example of a Compact Symmetric Object (CSO). It has a double radio lobe symmetrically located with respect to a central flat spectrum radio core (the location of the AGN) and has a physical extent of less than 200 pc. In this work we report VLBA observation of 21 cm HI absorption toward B2352+495 to investigate the properties of this remarkable radio source, in particular, to explore whether the radio emission can be confined by circumnuclear material (frustration scenario) or whether the source is likely to be young. We confirmed the two HI absorption features previously detected toward B2352+495 - a broad line nearly centered at the systemic velocity of the galaxy and a narrow redshifted component. The atomic gas from the broad absorption component is likely associated with circumnuclear material, consistent with the current paradigm of clumpy HI distribution in toroidal structures around supermassive black holes.