Asymmetrical structure of ionization and kinematics in the Seyfert galaxy NGC 5033

¹ Instituto de Astrofísica de Canarias, Tenerife, Spain e-mail: emg@ll.iac.es
² Centro Astronómico Hispano Alemán, Almería, Spain e-mail: aguijarr@urg.es
³ Dpto. Física Teórica y del Cosmos, Universidad de Granada, Spain
⁴ Space Telescope Science Institute, Baltimore, USA

Received: 18 October 2003
Accepted: 29 November 2004

Abstract

We present integral field spectroscopy of NGC 5033, a low luminosity Seyfert galaxy. The observations were made with INTEGRAL, a fiber based system operating at the WHT. The intensity map of the Hβ emission line represents a spiral or ring-like pattern of HII regions. On the contrary, the [OIII] intensity map morphology is markedly anisotropic. The strong morphological differences imply that the [OIII] emitters represent highly ionized gas illuminated by the central source. The [OIII] map morphology is compatible with a biconical structure of ionization induced by strong extinction in the galaxy disc that also obscures half of the spheroidal stellar bulge. We identify the spectrum corresponding to the Seyfert 1 nucleus from the presence of Hβ broad emission lines. This spectrum is located in a region where strong extinction is expected but exhibits the bluest spectral energy distribution. The Seyfert 1 nucleus seems to be offcenter with respect to the stellar rotation center. This result has been also found in other Seyfert galaxies and interpreted in terms of a past merger. The offcentering could indicate the presence of nonsymmetric departures in the gravitational potential which could be fueling the active nucleus. The kinematics of the [OIII] emitters show important deviations at a kpc scale with respect to the stellar velocity field and show features related to the asymmetrical morphology of the high ionization region.