Einstein, and have compiled an additional 543 redshifts from the literature. There is a correlation between galaxy surface density and group velocity dispersion, with μ is proportional to σ^1.6+/- 0.6^, but the scatter about this relation is large. We examine the relationship between the group x-ray luminosity in the 0.3-3.5 keV band and the measured velocity dispersion. Richer groups follow the same relation as rich clusters [cf. Quintana & Melnick, Al, 87,972 (1982)] with L_x_ is proportional to σ^4.0+/-0.6^, but the relation flattens for lower luminosity systems which have velocity dispersions below 300 km s^-1^. We suggest that the L_x_-σ relation arises from a combination of extended cluster emission and emission associated with individual galaxies. The x-ray emission for the richer groups is dominated by emission from the intragroup medium, as for the richer clusters; emission from the poorer clusters is dominated by less extended emission associated with the individual group galaxies.
No takes yet. Share an insight, caveat, or question.
Dell’Antonio et al. (1994) studied this question.