[ITAL]Chandra[/ITAL] Observations of the Evolving Core of the Starburst Galaxy NGC 253

Abstract

Chandra observations of the core of the nearby starburst galaxy NGC 253 reveal a heavily absorbed source of hard X-rays embedded within the nuclear starburst region. The source has an unabsorbed, 2-10 keV luminosity of ≥10 39 ergs s and photoionizes the surrounding gas. We observe this source through a dusty torus with a neutral 1 absorbing column density of cm. The torus is hundreds of parsecs across and collimates the 23 2 N ∼ 2 # 10 H starburst-driven nuclear outflow. We suggest that the ionizing source is an intermediate-mass black hole or a weakly accreting supermassive black hole, which may signal the beginnings or endings of active galactic nucleus activity.