Multiwavelength View of the Inner Spiral of NGC 1365

TL;DR

This study provides a multiwavelength analysis of NGC 1365's nuclear region, revealing the interplay of a weak obscured AGN, starburst activity, and outflows across X-ray, optical, infrared, and radio observations.

Contribution

It offers a detailed spatially resolved view of the nuclear structures and their multiwavelength characteristics, including the first X-ray spectroscopy of a serendipitously detected BL Lac object.

Findings

Ultrasoft X-ray emission aligns with nuclear outflows.

Starburst dominates 0.5-1.5 keV emission in the circumnuclear ring.

Hard X-ray emission is primarily from the obscured AGN.

Abstract

We study the extended nuclear emission of the starburst galaxy NGC 1365. A weak obscured AGN and a strong starburst both contribute to the observed X-ray, optical, infrared, and radio emission in the inner 2kpc. The X-ray emission is spatially resolved, allowing comparison with multiwavelength data that highlights the structures dominating the nuclear region: the AGN, the nuclear spiral, the circumnuclear starburst ring, and nuclear outflow. The ultrasoft X-ray emission below 0.5keV is spatially coincident with the conical outflow traced by higher excitation optical emission lines like [O III] and [Ne III]. The strong starburst concentrated in super-star clusters in a circumnuclear ring with radius ~1kpc dominates the 0.5-1.5keV emission and is visible in radio, molecular CO, and infrared maps of the central kiloparsec. The hard (2-10keV) emission is dominated by the obscured AGN, but also contributes to the emission from relatively old (~7Myr) but still enshrouded in dust and extremely massive (10^7Msun) super-star clusters (Galliano 2008), hidden from view in the optical and soft X-ray bands. In the Appendix we present the X-ray spectroscopy and photometry of BL Lac MS 0331.3-3629, a high-energy peaked BL Lac candidate at z=0.308, serendipitously detected in one Chandra and five XMM-Newton observations of NGC1365.