Fabry-Perot observations of the ionized gas in the spiral galaxy NGC 6951

¹ Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Canarias, Spain
² Observatorio Astronómico Nacional (UNAM), Ensenada, B.C., México
³ Consejo Superior de Investigaciones Cientificas, Spain

Corresponding author: M. Rozas, maite@astrosen.unam.mx

Received: 27 November 2000
Accepted: 2 January 2002

Abstract

We present two dimensional kinematic observations at high angular and velocity resolution measured via the Hα  emission line in the active barred spiral NGC 6951, obtained using the TAURUS II Fabry-Perot system on the 4.2 m William Herschel Telescope. From the radial velocity map we produced the rotation curve, which has a rapidly rising inner portion, and then remains remarkably flat to large radii. Subtracting a two-dimensional projected model of this rotation from the observed map yields a residual velocity map which shows significant non-circular motions, above all in the circumnuclear zone, where they reach projected values of 45 km s^-1. The kinematic and morphological properties of this zone, a narrow well-defined annular region, point to inflow of gas resulting from perturbation in the stream-lined gas flow due to the bar, as predicted in dynamical models. The overall gas kinematics leads us to infer the presence of an inner disc within the main galactic disc, whose presence is marked by two inner Lindblad resonances at 180 pc and 900 pc from the centre respectively. Our map of the Hα velocity dispersion shows characteristic values of 20 km s^-1 for the Hii regions, and an obvious correlation between higher values and the brightest Hii regions. The value rises to >100 km s^-1 as the nucleus is approached.