THE TAXONOMY OF BLUE AMORPHOUS GALAXIES .1. H-ALPHA AND UBVI DATA

Dwarf galaxies play an important role in our understanding of galaxy f ormation and evolution. We have embarked on a systematic study of 12 n earby dwarf galaxies (most of which have been classified as amorphous) selected preferentially by their blue colors. The properties of the g alaxies in the sample suggest that they are in a burst or postburst st ate. It seems likely that these amorphous galaxies are closely related to other ''starburst'' dwarfs such as blue compact dwarfs (BCDs) and H II galaxies but are considerably closer and therefore easier to stud y. If so, these galaxies may offer important insights into dwarf galax y evolution. In an effort to clarify the role of starbursts in evoluti onary scenarios for dwarf galaxies, we present Ha and UBVI data for ou r sample. Blue amorphous galaxies, like BCDs and H II galaxies, have s urface brightness profiles that are exponential in the outer regions ( r greater than or similar to 1.5r(e)) but have a predominantly blue ce ntral excess, which suggests a young burst in an order, redder galaxy. Seven of the galaxies have the bubble or filamentary Ho: morphology a nd double-peaked emission lines that are the signature of superbubbles or superwind activity. These galaxies are typically the ones with the strongest central excesses. The underlying exponential galaxies are v ery similar to those found in BCDs and H II galaxies. How amorphous ga laxies fit into the dwarf irregular-''starburst dwarf''-dwarf elliptic al evolutionary debate is less clear. In this paper, we present our da ta and make some preliminary comparisons between amorphous galaxies an d other classes of dwarf galaxies. In a future companion paper, we wil l compare this sample more quantitatively with other dwarf galaxy samp les in an effort to determine if amorphous galaxies are a physically d ifferent class of object from other starburst dwarfs such as BCDs and H II galaxies and also investigate their place in dwarf galaxy evoluti on scenarios.