Gas accretion in the M32 nucleus: Past and present

Abstract

Using adaptive optics assisted Gemini/NIFS data, I study the present and past gas accretion in the central 3″ of the M32 nucleus. From changes in the spectral slope and CO line depths near the center, I find evidence for unresolved dust emission resulting from black hole (BH) accretion. With a luminosity of∼2×1038 erg s-1, this dust emission appears to be the most luminous tracer of current BH accretion, 2 orders of magnitude more luminous than previously detected X-ray emission. These observations suggest that using high-resolution infrared data to search for dust emission may be an effective way to detect other nearby, low-luminosity BHs, such as those in globular clusters. I also examine the fossil evidence of gas accretion contained in the kinematics of the stars in the nucleus. The higher order moments (h3 and h4) of the line-of-sight velocity distribution show patterns that are remarkably similar to those seen on larger scales in elliptical galaxies and in gas-rich merger simulations. The kinematics suggests the presence of two components in the M32 nucleus, a dominant disk overlying a pressure supported component. I discuss possible formation scenarios for the M32 nucleus in the context of the kinematic data as well as previous stellar population studies. The kinematic measurements presented here are the highest quality available for the nucleus of M32, and may be useful for any future dynamical models of this benchmark system.© 2010. The American Astronomical Society.