NGC 2276: a remarkable galaxy with a large number of ULXs

TL;DR

This study uses Chandra X-ray data to analyze NGC 2276, revealing numerous ULXs, a high star formation rate, and the effects of ram pressure and viscous transfer on its disturbed morphology.

Contribution

It provides the first detailed Chandra analysis of NGC 2276's X-ray sources, clarifies the nature of ULXs, and links galaxy interactions to its morphology and star formation.

Findings

Detected 16 X-ray sources, including 8 ULXs.

Constructed the galaxy's X-ray luminosity function.

Estimated the star formation rate to be 5-15 Msun/yr.

Abstract

The starbusting, nearby (D = 32.9 Mpc) spiral (Sc) galaxy NGC2276 belongs to the sparse group dominated by the elliptical galaxy NGC2300. NGC2276 is a remarkable galaxy, as it displays a disturbed morphology at many wavelengths. This is possibly due to gravitational interaction with the central elliptical galaxy of the group. Previous ROSAT and XMM-Newton observations resulted in the detection of extended hot gas emission and of a single very bright (~1.e41 erg/s) ultraluminous X-ray source (ULX) candidate. Here we report on a study of the X-ray sources of NGC2276 based on CHANDRA data taken in 2004. CHANDRA was able to resolve 16 sources, 8 of which are ULXs, and to reveal that the previous ULX candidate is actually composed of a few distinct objects. We construct the luminosity function of NGC2276, which can be interpreted as dominated by high mass X-ray binaries, and estimate the star formation rate (SFR) to be ~5-15 Msun/yr, consistent with the values derived from optical and infrared observations. By means of numerical simulations, we show that both ram pressure and viscous transfer effects are necessary to produce the distorted morphology and the high SFR observed in NGC2276, while tidal interaction have a marginal effect.