Collaborator: Steve Maddox (IoA-Cambridge)
Recent morphological studies (Telles, Melnick & Terlevich 1997) have indicated that luminous HII galaxies tend to show distorted morphology suggestive of tidal interactions triggering the present starburst while low luminosity HII galaxies tend to be instead symmetric and regular. Surprisingly, isolated HII galaxies tend to be of high luminosity and disturbed morphology while HII galaxies with neighbours tend to be low luminosity regular HII galaxies. Furthermore, the metal abundance and the equivalent width of the emission lines in HII galaxies do not depend on the presence of a bright companion. These results are opposed to simple expectations if interaction with a bright companion is the main mechanism triggering the starbursts.
The Spectrophotometric catalogue of HII galaxies presents over 300 HII galaxies, mostly selected from the equatorial Univ. of Michigan survey and the southern Tololo survey of emission line galaxies. Very few morphological studies have been made of this class of objects. I would like to obtain images of a large number of these objects for statistical study of their morphology, their links with other types of dwarfs and their immediate environment.
We wish to carry out an investigation of the galaxy environments of low redshift HII galaxies by cross-correlating their positions on the sky with those of faint field galaxies in the Automatic Plate Measuring Machine catalogues. We address the question of whether violent star formation in HII galaxies is induced by low mass companions by describing statistically their local environment. Our motivation is that even if low mass companions were mainly intergalactic HI clouds, their optical counterparts should be detectable at faint limits of the APM scans. Our preliminary results are all consistent with HII galaxies being a randomly selected sample of normal faint field galaxy with no extra clustering. This suggests that at least in these dwarf starburst galaxies star formation is not triggered by tidal interactions and may have a different origin. A more comprehensive analysis is underway.