The Multifrequency Behavior of Sagittarius A*

TL;DR

This paper examines the multi-frequency emission characteristics of Sagittarius A* at the Galactic Center, comparing it with low luminosity active galactic nuclei, and discusses radiation mechanisms, flare models, and star formation near supermassive black holes.

Contribution

It provides a comprehensive analysis of SgrA*'s multi-frequency behavior and explores its implications for galaxy evolution, radiation processes, and star formation in the vicinity of supermassive black holes.

Findings

SgrA* exhibits weak activity across radio, infrared, and X-ray regimes.

The hot-spot model is considered for explaining flare profiles.

Star formation may occur near supermassive black holes in low-luminosity nuclei.

Abstract

The Galactic Center is the closest galactic nucleus that allows us to determine the multi-frequency behavior of the supermassive black hole counterpart Sagittarius A* in great detail. We put SgrA*, as a nucleus with weak activity, into the context of nearby low luminosity nuclei. Possible hints for galaxy evolution of these sources across the [NII]-based diagnostic diagram can be inferred from dependencies on the masses, excitation ratios, and radio luminosities within this diagram. For SgrA* we also discuss responsible radiation mechanisms covering results from the radio, infrared, and X-ray regime. We also address the question of justifying the hot-spot model for describing flare profiles in light curves. Since the brightness of LLAGN is also linked to star formation we briefly discuss the possibility of having stars formed in the immediate vicinity of supermassive black holes and possibly even in a mildly relativistic environment.