The molecular gas in the central region of NGC 7213

TL;DR

This study combines multi-wavelength data to analyze the molecular gas and AGN activity in NGC 7213, revealing a faint, unobscured AGN with minimal impact on the host galaxy's star formation and gas dynamics.

Contribution

It provides a comprehensive multi-wavelength analysis of NGC 7213, including molecular gas kinematics and AGN properties, highlighting the importance of combining different data sets for galaxy studies.

Findings

Molecular gas is rotation-dominated in NGC 7213.

ALMA underestimates gas mass by a factor of ~3 without large-scale emission.

The AGN is faint and does not significantly influence host galaxy properties.

Abstract

We present a multi-wavelength study (from X-ray to millimetre) of the nearby low-luminosity active galactic nucleus (LLAGN) NGC 7213. We combine the information from the different bands to characterize the source in terms of contribution from the AGN and the host-galaxy interstellar medium (ISM). This approach allows us to provide a coherent picture of the role of the AGN and its impact, if any, on the star formation and molecular gas properties of the host galaxy. We focused our study on archival ALMA Cycle 1 observations, where the CO(2-1) emission line has been used as a tracer of the molecular gas. Using the 3DBarolo code on ALMA data, we performed the modelling of the molecular gas kinematics traced by the CO(2-1) emission, finding a rotationally dominated pattern. The host-galaxy molecular gas mass was estimated from the integrated CO(2-1) emission line obtained with APEX data, assuming an $\alpha_{CO}$ conversion factor. By using the ALMA data, we would have underestimated the gas masses by a factor $\sim$3, given the filtering out of the large scale emission in interferometric observations. We also performed a complete X-ray spectral analysis on archival observations, revealing a relatively faint and unobscured AGN. The AGN results to be too faint to significantly affect the properties of the host-galaxy, such as star formation activity and molecular gas kinematics and distribution.