Gas Accretion in the M32 Nucleus: Past & Present

TL;DR

This study investigates current and past gas accretion in M32's nucleus using high-resolution infrared data, revealing dust emission linked to black hole activity and complex stellar kinematics indicative of multiple components.

Contribution

It provides the first high-quality kinematic analysis of M32's nucleus and demonstrates that infrared dust emission can effectively trace low-luminosity black hole accretion.

Findings

Detection of unresolved dust emission indicating black hole accretion.

Identification of two stellar components: a disk and a pressure-supported structure.

Kinematic patterns similar to those in larger elliptical galaxies and merger simulations.

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 BH accretion. With a luminosity of ~2e38 erg/s, this dust emission appears to be the most luminous tracer of current BH accretion, two 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.