Adaptive optics near infrared integral field spectroscopy of NGC 2992^*

¹ Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany e-mail: sfriedrich@mpe.mpg.de
² Instituto de Astrofísica de Canarias, 38205 La Laguna (Tenerife), Spain
³ Department of Physics, Le Conte Hall, University of California, Berkeley, CA 94720, USA

Received: 21 December 2009
Accepted: 12 May 2010

Abstract

Aims. NGC 2992 is an intermediate Seyfert 1 galaxy showing outflows on kilo parsec scales which might be due either to AGN or starburst activity. We therefore aim at investigating its central region for a putative starburst in the past and its connection to the AGN and the outflows.

Methods. Observations were performed with the adaptive optics near infrared integral field spectrograph SINFONI on the VLT, complemented by longslit observations with ISAAC on the VLT, as well as N- and Q-band data from the Spitzer archive. The spatial and spectral resolutions of the SINFONI data are 50 pc and 83 km s^-1, respectively. The field of view of × corresponds to 450 pc × 450 pc. Brγ equivalent width and line fluxes from PAHs were compared to stellar population models to constrain the age of the putative recent star formation. A simple geometric model of two mutually inclined disks and an additional cone to describe an outflow was developed to explain the observed complex velocity field in H₂ 1–0S(1).

Results. The morphologies of the Brγ and the stellar continuum are different suggesting that at least part of the Brγ emission comes from the AGN. This is confirmed by PAH emission lines at 6.2 μm and 11.2 μm and the strength of the silicon absorption feature at 9.7 μm, which point to dominant AGN activity with a relatively minor starburst contribution. We find a starburst age of 40–50 Myr from Brγ line diagnostics and the radio continuum; ongoing star formation can be excluded. Both the energetics and the timescales indicate that the outflows are driven by the AGN rather than the starburst. The complex velocity field observed in H₂ 1–0S(1) in the central 450 pc can be explained by the superposition of the galaxy rotation and an outflow.