3D spectroscopy of local luminous compact blue galaxies: kinematics of NGC 7673

Abstract

The kinematic properties of the ionized gas of local luminous compact blue galaxy NGC 7673 are presented using three-dimensional data taken with the PPAK integral field unit at the 3.5-m telescope in the Centro Astronomico Hispano Aleman. Our data reveal an asymmetric rotating velocity field with a peak-to-peak difference of 60 km s(-1). The kinematic centre is found to be at the position of a central velocity width maximum (sigma = 54 +/- 1 kms(-1)), which is consistent with the position of the luminosity-weighted centroid of the entire galaxy. The position angle of the minor rotation axis is 168 degrees as measured from the orientation of the velocity field contours. At least two decoupled kinematic components are found. The first one is compact and coincides with the position of the second most active star formation region (clump B). The second one is extended and does not have a clear optical counterpart. No evidence of active galactic nuclei activity or supernovae galactic winds powering any of these two components has been found. Our data, however, show evidence in support of a previously proposed minor merger scenario in which a dwarf galaxy, tentatively identified with clump B, is falling into NGC 7673 and triggers the starburst. Finally, it is shown that the dynamical mass of this galaxy may be severely underestimated when using the derived rotation curve or the integrated velocity width, under the assumption of virialization.