The Environment of HII Galaxies revisited

We present a study of the close (∼ 200h −1 75 kpc) environment of 110 relatively local (z∼ 0.16) HII galaxies, selected from the Sloan Digital Sky Survey (SDSS; DR7). We use available spectroscopic and photometric redshifts in order to investigate the pr esence of a close and possibly interacting companion galaxy. Our aim is to compare the physical properties of isolated and interacting HII galaxies and investigate possible systematic effects in their use as cosmological probes. We find that interac ting HII galaxies tend to be more compact, less luminous and have a lower velocity dispersion than isolated ones, in agreement with previous studies on smaller samples. However, as we verified, these environmental di fferences do not affect the cosmologically important LH�− � correlation of the HII galaxies.