X-ray Photons in the CO 2-1 'Lacuna' of NGC 2110

TL;DR

This study investigates the role of X-ray photons in exciting the molecular clouds around NGC 2110's AGN, revealing an X-ray induced feature that correlates with optical and H2 emissions, and explaining the lack of CO 2-1 emission.

Contribution

It provides new evidence linking X-ray excitation to molecular cloud properties and explains the CO emission deficiency in NGC 2110's circumnuclear region.

Findings

Detection of an X-ray feature aligned with optical and H2 emissions.

Correlation between X-ray emission and molecular cloud excitation.

Support for X-ray driven excitation of a multi-phase circumnuclear medium.

Abstract

A recent ALMA study of the Seyfert 2 Active Galactic Nucleus (AGN) NGC 2110 by Rosario et al. (2019) has reported a remarkable lack of CO 2-1 emission from the circumnuclear region, where optical lines and H2 emission are observed, leading to the suggestion of excitation of the molecular clouds by the AGN. Since interaction with X-ray photons could be the cause of this excitation, we have searched the archival Chandra data for corroborating evidence. We report an extra-nuclear ~1'' (~170 pc) feature found in the soft (<1.0 keV) Chandra data of the Seyfert 2 Active Galactic Nucleus (AGN) NGC 2110. This feature is elongated to the north of the nucleus and its shape matches well that of the optical lines and H2 emission observed in this region, which is devoid of CO 2-1 emission. The Chandra image completes the emerging picture of a multi-phase circumnuclear medium excited by the X-rays from the AGN, with dense warm molecular clouds emitting in H2 but depleted of CO 2-1 emission.