Astronomy and Astrophysics – Astronomy
Scientific paper
Jul 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995aj....110...21c&link_type=abstract
Astronomical Journal v.110, p.21
Astronomy and Astrophysics
Astronomy
22
Galaxies: Clustering, Galaxies: Interactions
Scientific paper
In view of recent and forthcoming surveys of distant clusters of galaxies, we investigate cluster evolution for a suite of N-body simulations. We examine Einstein-deSitter, open ({OMEGA} = 0.2) and flat, low density ({OMEGA} = 0.2, λ =0.8) models with power-law initial density distribution P is proportional to K^n^, n = - 2, - 1, and 0. We emphasize the effects of force resolution and the subtleties of cluster identification. We develop a physical picture of the evolution of velocity dispersions of individual clusters as a function of redshift. By studying simulated clusters individually we show that mergers and accretions change dispersions in a characteristic way. Dispersions reach their maximum (an increase of ~20%) when the accreted object first swings into the center of the cluster; at this time the distribution of matter does not necessarily exhibit obvious substructure. For all the clusters in a particular simulation, the scatter in σ(M) is about 10%, consistent with that predicted from merger activity. Although the abundance of cluster masses in the models is not consistent with Press- Schechter theory, the sense and degree of evolution is. Over the entire mass range in our simulations, the abundance of collapsed objects increases with time. Dispersions as a function of mass, on the other hand, decrease with time, consistent with spherical theory. For most models, the velocity dispersion function produced by these effects reflects a cluster population which increases with time and a group population which decreases with time. We predict, therefore, that redshift observations of distant groups will yield larger abundances than at z = 0.0. To use n (> σ) to distinguish among cosmological models a volume of ~> 2 x 10^6^h^-3^ Mpc must be simulated. We extend our analysis to x-ray luminosities in order to compare our models with already existing data. Unbiased Einstein-deSitter models produce too many clusters to be consistent with the data. None of our other models is ruled out by either the observed local abundances or the observed evolution. To check consistency with the models further, one could compare x-ray and optical observations of a single sample of distant galaxies. Over the range of dispersions in our simulations (about 300- 1200 km/s for a flat, unbiased model) our optical evolution is negligible, while for the same sample there are significantly more low- L_x_ clusters (L_x_ <~ 5 x 10^44^ erg/s) at z ~ 0.3 than at the present time.
Crone Mary M.
Geller Margaret J.
No associations
LandOfFree
Recent Evolution in Cluster Velocity Dispersions does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Recent Evolution in Cluster Velocity Dispersions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Recent Evolution in Cluster Velocity Dispersions will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1169595