Photometry and Kinematics of Self-Gravitating Eccentric Nuclear Disks

TL;DR

This paper uses N-body simulations to study the photometric and kinematic signatures of eccentric nuclear disks, explaining features like the double nucleus in galaxies such as Andromeda and exploring effects like mass segregation.

Contribution

It provides simulated maps of eccentric nuclear disks from various perspectives, analyzing their photometric and kinematic properties and the impact of mass segregation.

Findings

Heavier stars concentrate in brighter peaks.

Average line-of-sight velocities are lower in eccentric disks than circular rings.

Velocity dispersion peaks at the black hole, not the photometric peak.

Abstract

The Andromeda Galaxy hosts an elongated nucleus with (at least) two distinct brightness peaks. The double nucleus can be explained by the projection of a thick, apsidally-aligned eccentric nuclear disk of stars in orbit about the central black hole. Several nearby early-type galaxies have similar asymmetric nuclear features, indicating the possible presence of eccentric nuclear disks. We create simulated photometric (surface density) and kinematic (line-of-sight velocity) maps of eccentric nuclear disks using N-body simulations. We image our simulations from various lines of sight in order to classify them as double nuclei, offset nuclei, and centered nuclei. We explore the effects of mass segregation on the photometric maps, finding that heavier stars are concentrated in the brighter peak. The average line-of-sight velocity values are lower in an eccentric nuclear disk than for a circular ring about the supermassive black hole. The velocity dispersion values are higher and peak at the position of the supermassive black hole, which does not typically match the peak in photometry.