X-ray emission from the supergiant shell in IC2574

Abstract

The M81 group member dwarf galaxy IC2574 hosts a supergiant shell of current and recent star formation activity surrounding a 1000 × 500 pc hole in the ambient H I gas distribution. Chandra X-ray Observatory imaging observations reveal a luminous, L X 6.5 × 1038 erg s-1 in the 0.3-8.0 keV band, point-like source within the hole but offset from its center and fainter diffuse emission extending throughout and beyond the hole. The star formation history at the location of the point source indicates a burst of star formation beginning 25 Myr ago and currently weakening and there is a young nearby star cluster, at least 5 Myr old, bracketing the likely age of the X-ray source at between 5 and 25 Myr. The source is thus likely a bright high-mass X-ray binary - either a neutron star or black hole accreting from an early B star undergoing thermal-timescale mass transfer through Roche lobe overflow. The properties of the residual diffuse X-ray emission are consistent with those expected from hot gas associated with the recent star formation activity in the region. © © 2012 The American Astronomical Society. All rights reserved.