Intermediate age stars as origin of the low velocity dispersion nuclear ring in Mrk1066

TL;DR

This study uses near-infrared integral field spectroscopy to analyze the stellar populations in the nuclear region of Mrk1066, revealing that intermediate age stars are associated with low velocity dispersion rings, suggesting a formation history linked to past gas inflow events.

Contribution

First two-dimensional stellar population synthesis in the near-infrared of an active galaxy's nucleus, linking intermediate age stars to low-sigma nuclear rings.

Findings

Intermediate age stars (0.3-0.7 Gyr) dominate beyond 160 pc from the nucleus.

Low-sigma nuclear rings are associated with intermediate age stellar populations.

The nucleus contains hot dust and a featureless power-law continuum.

Abstract

We report the first two-dimensional stellar population synthesis in the near-infrared of the nuclear region of an active galaxy, namely Mrk1066. We have used integral field spectroscopy with adaptive optics at the Gemini North Telescope to map the to map the age distribution of the stellar population in the inner 300 pc at a spatial resolution of 35 pc. An old stellar population component (age >5Gyr) is dominant within the inner ~160pc, which we attribute to the galaxy bulge. Beyond this region, up to the borders of the observation field (~300 pc), intermediate age components (0.3-0.7Gyr) dominate. We find a spatial correlation between this intermediate age component and a partial ring of low stellar velocity dispersions (sigma). Low-sigma nuclear rings have been observed in other active galaxies and our result for Mrk1066 suggests that they are formed by intermediate age stars. This age is consistent with an origin for the low-sigma rings in a past event which triggered an inflow of gas and formed stars which still keep the colder kinematics (as compared to that of the bulge) of the gas from which they have formed. At the nucleus proper we detect, in addition, two unresolved components: a compact infrared source, consistent with an origin in hot dust with mass ~1.9x10^{-2} M_Sun, and a blue featureless power-law continuum, which contributes with only ~15% of the flux at 2.12 microns.