The IR- and X-Radiation of the Starburst Dwarf Galaxy UGCA 86

Summary

UGCA 86 (= VII Zw 009) is a companion of IC 342 and is one of the nearest starburst galaxies. It contains at least two starbursts, of which the central one is heavily obscured by dust. The IR radiation (IRAS has a relatively steep (cool) spectrum. The X-radiation (ROSAT pointed observation) seems to come from supernovae.

Introduction

In our optical observations of UGCA 86 (Richter et al. 1991) we found it to be a low surface brightness dwarf galaxy which contains two star formation regions, a central one and one near the southern border. Whereas the southern burst seems relatively normal, the central one is heavily reddened and has also a “softer” appearance (cf. Saha & Hoessel 1991). Together with the finding of an IR source in the IRAS catalog these facts fit very well the assumption that the central burst contains a large amount of dust.

Because the catalogued IRAS position did not fit the optical position well, we reprocessed the IRAS observation and observed the galaxy with a ROSAT pointing.

Observations

We have reprocessed the IRAS data using the GIPSY-IRAS system developed by the Laboratory for Space Research at Groningen (see Wesselius et al. 1992). High-resolution IRAS images were processed in Groningen using a maximum entropy method. While the IRAS Point Source Catalog shows only one source at the area of UGCA 86, the high-resolution images clearly reveal four sources.