The environment of star-forming dwarf galaxies - The role of dwarf companion objects

We are currently performing a new analysis of the close environment of star -forming dwarf galaxies and its effects on their star-forming activity. For a sample of 142 thoroughly studied objects, we search the NASA Extragalact ic Database for possible companion galaxies of any apparent luminosity and angular size. From a first analysis of a part of our sample, we find only a bout 50% of our objects to be isolated in the sense that no companion objec t was detected within a redshift difference of 500 km s(-1) and an angular separation corresponding to a projected distance of 1 Mpc, assuming H-0=75 km s(-1) Mpc(-1). By splitting the sample into different redshift intervals , we demonstrate an observational bias against low-luminosity companion obj ects which implies that a large fraction of star-forming dwarf galaxies, al though lacking bright companions, might possess dwarf companion objects. Si milarly to other authors, we find no evidence for a difference in star-form ing activity due to the presence or absence of possible companions.