AGN-Starburst connection in NGC7582: Gemini near-infrared spectrograph integral field unit observations

TL;DR

This study uses near-infrared integral field spectroscopy to analyze the nuclear region of NGC7582, revealing details about dust, star formation, gas kinematics, and outflows, and exploring the connection between the active nucleus and starburst activity.

Contribution

First detailed near-IR IFU analysis of NGC7582's nucleus, revealing dust, star formation, and gas dynamics, and providing insights into AGN-starburst connection.

Findings

Unresolved nuclear source attributed to circumnuclear dust at <25 pc.

Star-forming ring of ~190 pc radius with ~5 Myr age.

Mass outflow rate of ionized gas exceeds accretion rate by an order of magnitude.

Abstract

We analyse two-dimensional near-IR K-band spectra from the inner 660x315 pc^2 of the Seyfert galaxy NGC7582 obtained with the Gemini GNIRS IFU. The nucleus harbors an unresolved source well reproduced by a blackbody of temperature T 1050 K, which we attribute to emission by circumnuclear dust located closer than 25 pc from the nucleus, with total mass of ~3x10^{-3}M_Sun. Surrounding the nucleus, we observe a ring of active star formation with radius of ~190 pc, an age of ~5 Myr. The radiation of the young stars in the ring accounts for at least 80 % of the ionization observed in the Brgamma emitting gas, the remaining being due to radiation emitted by the active nucleus. The stellar kinematics reveals: (1) a distorted rotation pattern in the radial velocity field with kinematic center apparently displaced from the nuclear source by a few tens of parsecs; (2) a high velocity dispersion in the bulge of sigma=170 km/s; (3) a partial ring of sigma=50 km/s interpreted as due to stars formed from cold gas in a previous burst of star formation. The kinematics of the ionized gas shows an additional blueshifted component with velocities > 100 km/s interpreted as due to an outflow along the ionization cone. The mass outflow rate in the ionized gas was estimated as ~0.05 M_Sun/yr, which is one order of magnitude larger than the accretion rate to the AGN. The flux distribution and kinematics of the hot molecular gas, traced by the H2l2.22um emission line, suggests that most of this gas is in the galactic plane. An excess blueshift along PA~-70 can be interpreted as an inflow towards the nucleus. An AGN-Starburst connection in the nucleus of NGC7582 is supported by the ratio between the mass accretion rate and the star formation rate in the circumnuclear region of ~0.26%, which is close to the Magorrian relation.