Detection of a Compact Nuclear Radio Source in the Local Group Elliptical Galaxy M32

Abstract

The Local Group compact elliptical galaxy M32 hosts one of the nearest candidate supermassive black holes (SMBHs), which has a previously suggested X-ray counterpart. Based on sensitive observations taken with the Karl G. Jansky Very Large Array (VLA), we detect for the first time a compact radio source coincident with the nucleus of M32, which exhibits an integrated flux density of ∼ 47.3+/- 6.1 μ {Jy} at 6.6 GHz. We discuss several possibilities for the nature of this source, favoring an origin of the long-sought radio emission from the central SMBH, for which we also revisit the X-ray properties based on recently acquired Chandra and XMM-Newton data. Our VLA observations also discover radio emission from three previously known optical planetary nebulae in the inner region of M32.