A deep Chandra observation of the interacting star-forming galaxy Arp 299

TL;DR

This study uses a deep Chandra X-ray observation to analyze the X-ray sources in the interacting galaxy system Arp 299, revealing numerous high-mass X-ray binaries, a hot gaseous component, and insights into ULX populations and galaxy outflows.

Contribution

First detailed X-ray analysis of Arp 299 revealing the nature and distribution of X-ray sources, hot gas, and outflows in this interacting galaxy system.

Findings

25 discrete X-ray sources detected, including ULXs.

Identification of 20 off-nuclear sources, 14 point-like.

Observed deficit in ULX numbers possibly due to confusion effects.

Abstract

We present results from a 90 ks Chandra ACIS-S observation of the X-ray luminous interacting galaxy system Arp 299 (NGC 3690/IC 694). We detect 25 discrete X-ray sources with luminosities above 4.0x10^38 erg s^-1 covering the entire Ultra Luminous X-ray source (ULX) regime. Based on the hard X-ray spectra of the non-nuclear discrete sources identified in Arp 299, and their association with young, actively star-forming region of Arp 299 we identify them as HMXBs. We find in total 20 off-nuclear sources with luminosities above the ULX limit, 14 of which are point-like sources. Furthermore we observe a marginally significant deficit in the number of ULXs, with respect to the number expected from scaling relations of X-ray binaries with the star formation rate (SFR). Although the high metalicity of the galaxy could result in lower ULX numbers, the good agreement between the observed total X-ray luminosity of ULXs, and that expected from the relevant scaling relation indicates that this deficit could be the result of confusion effects. The integrated spectrum of the galaxy shows the presence of a hot gaseous component with kT = 0.72+-0.03 keV, contributing 20% of the soft (0.1-2.0 keV) unabsorbed luminosity of the galaxy. A plume of soft X-ray emission in the west of the galaxy indicates a large scale outflow. We find that the AGN in NGC 3690 contributes only 22% of the observed broad-band X-ray luminosity of Arp 299.