The Black Hole and Central Stellar Population of MCG--6-30-15

TL;DR

This study uses near-infrared integral field spectroscopy to analyze the central 500 pc of galaxy MCG--6-30-15, revealing a counter-rotating stellar core, estimating the age of the stellar population, and constraining the black hole mass.

Contribution

First near-infrared integral field spectroscopy of MCG--6-30-15's core, revealing stellar kinematics, population age, and black hole mass constraints.

Findings

Discovery of a counter-rotating stellar core extending to 125 pc.

Estimated age of the central stellar population is about 65 Myr.

Upper limit for black hole mass is 6 x 10^7 solar masses.

Abstract

We present the first near-infrared integral field spectroscopy observations of the galaxy MCG--6-30-15. The H-band data studied in this paper cover the central 500 pc of the galaxy at the best resolution (0".1) so far. The spectra of the innermost regions are dominated by broad brackett series emission lines and non-stellar continuum, under which we are able to trace the distribution and kinematics of the stars and also the [Fe II] line emission. We find that there is a counter-rotating stellar core extending out to 125 pc, which appears to be associated with the [Fe II] emission. Based on the mass-to-light ratio, and the presence of this emission line, we estimate the age of the central stellar population to be of order of 65 Myr. We show that the gas needed to fuel the black hole is, at most, only 1 per cent of that needed to form these stars. We derive independent constraints on the black hole mass using the dynamical information and determine an upper limit for the black hole mass, Mbh < 6e7 Msun, that is consistent with other estimates.