A Multi-Wavelength Analysis of NGC 4178: A Bulgeless Galaxy with an AGN

TL;DR

This study combines optical, radio, infrared, and X-ray observations to confirm the presence of a deeply buried active galactic nucleus (AGN) in the bulgeless galaxy NGC 4178, highlighting the importance of multi-wavelength approaches.

Contribution

It provides multi-wavelength evidence supporting an AGN in a bulgeless galaxy and emphasizes the necessity of IR and X-ray data to detect obscured AGNs.

Findings

The galaxy's dynamical center coincides with the X-ray source.

Optical spectrum shows no AGN evidence, indicating obscuration.

Radio flux upper limit supports a deeply buried, high-accretion AGN.

Abstract

We present {\it Gemini} longslit optical spectroscopy and VLA radio observations of the nuclear region of NGC 4178, a late-type bulgeless disk galaxy recently confirmed to host an AGN through infrared and X-ray observations. Our observations reveal that the dynamical center of the galaxy is coincident with the location of the {\it Chandra} X-ray point source discovered in a previous work, providing further support for the presence of an AGN. While the X-ray and IR observations provide robust evidence for an AGN, the optical spectrum shows no evidence for the AGN, underscoring the need for the penetrative power of mid-IR and X-ray observations in finding buried or weak AGNs in this class of galaxy. Finally, the upper limit to the radio flux, together with our previous X-ray and IR results, is consistent with the scenario in which NGC 4178 harbors a deeply buried AGN accreting at a high rate.