HI in NGC 5433 and its Environment: High-Latitude Emission in a Small Galaxy Group

K. Spekkens, J. A. Irwin, D. J. Saikia

Published 2004-05-13, updated 2004-07-07Version 2

We present HI synthesis maps of the edge-on starburst NGC 5433 and its environment, obtained with the VLA in its C and D configurations. The observations and spectral model residuals of the main disc emission in NGC 5433 reveal 3 extraplanar features. We associate 2 of these features with coherent extraplanar extensions across multiple spectral channels in our data, including a complete loop in position-velocity space. Interpreting the latter as an expanding shell we derive a corresponding input energy of 2 x 10^54 ergs, comparable to that for the largest supershells found in the Galaxy and those in other edge-on systems. NGC 5433 is in a richer environment than previously thought. We confirm that KUG 1359+326 is a physical companion to NGC 5433 and find two new faint companions, both with Minnesota Automated Plate Scanner identifications, that we label SIS-1 and SIS-2. Including the more distant IC 4357, NGC 5433 is the dominant member of a group of at least 5 galaxies, spanning over 750 kpc in a filamentary structure. A variety of evidence suggests that interactions are occurring in this group. While a number of underlying mechanisms are consistent with the morphology of the high-latitude features in NGC 5433, we argue that environmental effects may play a role in their generation.