Emission-line galaxy surveys as probes of the spatial distribution of dwarf galaxies. I. The University of Michigan survey

Objective-prism surveys which select galaxies on the basis of line-emission are extremely effective at detecting low-luminosity galaxies and constitut e some of the deepest available samples of dwarfs. In this study, we confir m that emission-line galaxies (ELGs) in the University of Michigan (UM) obj ective-prism survey are reliable tracers of large-scale structure, and we u tilize the depth of the samples to examine the spatial distribution of low- luminosity (M-B > -18.0) dwarfs relative to higher luminosity giant galaxie s (M-B less than or equal to -18.0) in the Updated Zwicky Catalog (UZC). Ne w spectroscopic data are presented for 26 UM survey objects. We analyze the relative clustering properties of the overall starbursting ELG and normal galaxy populations, using nearest neighbor and correlation function statist ics. This allows us to determine whether the activity in ELGs is primarily caused by gravitational interactions. We conclude that galaxy-galaxy encoun ters are not the sole cause of activity in ELGs since ELGs tend to be more isolated and are more often found in the voids when compared to their norma l galaxy counterparts. Furthermore, statistical analyses performed on low-l uminosity dwarf ELGs show that the dwarfs are less clustered when compared to their nonactive giant neighbors. The UM dwarf samples have greater perce ntages of nearest neighbor separations at large values and lower correlatio n function amplitudes relative to the UZC giant galaxy samples. These resul ts are consistent with the expectations of galaxy biasing.