Radio Emission from Young Supernovae and Supernova Remnants in Arp 299

TL;DR

This study used high-resolution radio imaging to identify numerous young supernovae and remnants in Arp 299, revealing a rich population of compact sources and evidence of recent supernova activity in the galaxy's nuclei.

Contribution

First detailed milliarcsecond radio survey of Arp 299's nuclei, identifying hundreds of compact sources and linking supernova activity to galaxy merger dynamics.

Findings

Detected 30 compact radio sources in Arp 299's nuclei.

Identified a recent supernova with power 2000 times Cas A.

Estimated 500-1000 supernova remnants in nucleus A.

Abstract

We have made sensitive milliarcsecond-resolution radio images of the nearby merger galaxy Arp 299 at four epochs spread over 18 months between 2003 and 2005. The combined data revealed a total of 30 point sources in the two primary merger nuclei. Twenty-five of these are found in the northeastern nucleus (component "A"=IC 694) over a region ~100 pc in diameter, while five are in the southwestern nucleus (component "B1"=NGC 3690) within a region ~30 pc in size. These objects are interpreted as young supernovae and supernova remnants; the ratio of the source counts in nuclei A and B1 is approximately equal to the ratio of their predicted supernova rates. An approximate luminosity function has been derived for nucleus A, and indicates that it might contain as many as 500-1000 compact radio sources more powerful than Cas A; the integrated flux density of these sources would be about 20% of the total flux density seen at lower resolution. A new supernova occurred in nucleus B1 in the first half of 2005, having a peak radio power at least 2,000 times the present power of Cassiopeia A. This supernova is located within 0.4 pc (projected distance) of an apparently older supernova remnant, making it very likely that this indicates the presence of a massive super star cluster within nucleus B1. Comparison of the typical radio flux densities of our compact radio sources to the observed X-ray luminosities of nuclei A and B1 indicates that it is possible that one radio source in each nucleus actually could be associated with an active galactic nucleus rather than being a supernova remnant.