Astrophys. J., 518, 69-93 (1999/June-2)
The dynamics of poor systems of galaxies.
MAHDAVI A., GELLER M.J., BOHRINGER H., KURTZ M.J. and RAMELLA M.
Abstract (from CDS):
We assemble and observe a sample of poor galaxy systems that is suitable for testing N-body simulations of hierarchical clustering and other dynamical halo models. We (1) determine the parameters of the density profile ρ(r) and the velocity dispersion profile σp(R), (2) separate emission-line galaxies from absorption-line galaxies, examining the model parameters and as a function of spectroscopic type, and (3) for the best-behaved subsample, constrain the velocity anisotropy parameter, β, which determines the shapes of the galaxy orbits. Our sample consists of 20 systems, 12 of which have extended X-ray emission in the ROSAT All-Sky Survey. We measure the 877 optical spectra of galaxies brighter than mR~15.4 within 1.5 h–1 Mpc of the system centers (we take H0=100 h km.s–1.Mpc–1). Thus, we sample the system membership to a radius typically three times larger than other recent optical group surveys. The average system population is 30 galaxies, and the average line-of-sight velocity dispersion is ~300 km.s–1. The Navarro, Frenk, & White universal profile and the Hernquist model both provide good descriptions of the spatial data. In most cases an isothermal sphere is ruled out. Systems with declining σp(R) are well-matched by theoretical profiles in which the star-forming galaxies have predominantly radial orbits (β>0); many of these galaxies are probably falling in for the first time. There is significant evidence for spatial segregation of the spectroscopic classes regardless of σp(R).
Galaxies: Clusters: General - Galaxies: Fundamental Parameters - X-Rays: Galaxies
VizieR on-line data:
<Available at CDS (J/ApJ/518/69): table1.dat table2.dat>
Table 1: DOC SRGaNNN, DOC NRGaNNN, N=20. Table 2: DOC SRGaNNN.NN, DOC NRGaNNN.NN, N=877.
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