Research Note

Spiral galaxies with a central plateau in the gas velocity curve along the major axis

Dipartimento di Astronomia, Università di Padova, vicolo dell'Osservatorio 2, 35122 Padova, Italy e-mail: coccato@astro.rug.nl

Received: 21 October 2004
Accepted: 17 May 2005

Abstract

We present the minor-axis kinematics of ionized gas and stars for a sample of 5 spiral galaxies, which are characterized by either a zero or a shallow gas velocity gradient along their major axis. The asymmetric velocity profiles observed along the minor axis of NGC 4064 and NGC 4189 can be explained as due to the presence of a bar. This is also the case of NGC 4178, where the innermost portion of the gaseous disk is nearly face on. In NGC 4424 and NGC 4941, we measured non-zero gas velocities only in the central regions along the minor axis, and gas velocities drop to zero at larger radii. This kinematic feature is suggestive of the presence of an orthogonally-rotating gaseous component, which is confined in the innermost regions (i.e. an inner polar disk) and needs to be confirmed with integral-field spectroscopy.