The NGC 5775/4 Interacting System

Summary

ABSTRACT

We have made the first neutral hydrogen maps of the galaxy pair, NGC 5775, and NGC 5774, as well as a number of radio continuum maps from several independent observing runs at 6 and 20 cm. Although the galaxies are not strongly distorted, optically, we have discovered clear evidence for an interaction in the form of two connecting H I bridges through which gas is travelling from NGC 5774 to NGC 5775. Along the southern bridge, we have also detected non-thermal radio continuum emission, suggesting (but not requiring) that star formation may also be occuring between the galaxies. In addition, we have discovered H I arcs and extensions away from the plane of the IR-bright, edge-on galaxy, NGC 5775, and can confirm previous detections of arcs and plumes in the radio continuum. In this respect, NGC 5775 appears to be very similar to NGC 891.

INTRODUCTION

NGC 5775 is an edge-on, spiral galaxy with a face-on companion, NGC 5774, 4.3′ to the NW. It belongs to a small group (Group #148; Geller and Huchra 1983) which, in addition, includes IC 1070, only 3.9′ to the SW of NGC 5775. NGC 5775 is the dominant galaxy in the group, it is an IR bright galaxy (Soifer et al. 1987), and has a nuclear HII region spectrum (Giuricin et al. 1990). NGC 5774 is a barred “low surface brightness” (LSB) galaxy (Romanishin et al. 1983); however, its central surface brightness is more than a factor of 5 brighter than the brightest LSB galaxies studied by G. Bothun (these proceedings). Neither galaxy appears strongly tidally disturbed on the POSS prints.