Mid-Infrared Imaging of Active Galaxies: Active Nuclei and Embedded Star Clusters

TL;DR

This study presents high-resolution mid-infrared images of nine nearby active galaxies, revealing nuclear and star-forming regions, and providing new insights into their structures and embedded star clusters.

Contribution

The paper offers the first high-resolution MIR imaging of these galaxies, identifying previously unknown sources and morphological features, including embedded star clusters and dust structures.

Findings

Resolved MIR emission in four galaxies, revealing star clusters.

Identified a new MIR counterpart to the radio nucleus in NGC253.

Detected a dust-rich micro-bar in NGC7469.

Abstract

High resolution, mid-infrared (MIR) images of a set of nine nearby active galaxies are presented. The data were obtained with the TIMMI2 instrument mounted at the ESO 3.6m telescope using a set of N-band narrow filters. The resulting images have an angular resolution of 0.6"-1". The MIR emission has been resolved in four galaxies: NGC253, NGC1365, NGC1808 and NGC7469. The images unveil a circumnuclear population of unknown MIR sources in NGC1365 and NGC1808, coincident with radio sources. These MIR/radio sources are interpreted in terms of embedded young star clusters. A high-resolution MIR map of NGC253 is also presented, and enables the identification of a previously unknown MIR counterpart to the radio nucleus. Extended MIR emission is detected in NGC7469, and concurs with previous observations in the NIR and radio. For this source, an interesting morphological difference between the 10.4mic and the 11.9mic emission is observed, suggesting the presence of a dust-rich micro-bar. Our MIR images of Circinus do not show resolved emission from the nucleus down to an angular scale of 0.5". In the case of NGC2992, an upper limit to the extended MIR emission can be set. Finally, we provide new MIR flux measurements for the unresolved AGN in NGC5995, IZw1 and IIZw136.