Statistics – Computation
Scientific paper
Dec 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993aas...18311508c&link_type=abstract
American Astronomical Society, 183rd AAS Meeting, #115.08; Bulletin of the American Astronomical Society, Vol. 25, p.1466
Statistics
Computation
Scientific paper
A new, three dimensional, shock capturing, hydrodynamic code (TVD) is utilized to determine the distribution of hot gas in a variety of cosmological models. Periodic boundary conditions are assumed: boxes with size 85h(-1) Mpc having cell size 0.31h(-1) Mpc, are followed in a simulation with 270(3=10(7.3)) cells. We identify the X-ray emitting clusters in the simulation boxes, compute the luminosity functions at several wavelength bands, the temperature functions and estimated sizes as well as the evolution of these quantities with redshift. Different models yield different results with the differences being far larger than the numerical inaccuracies involved. We find that COBE-normalized Omega =1 CDM model pridicts an order of magnitude more bright X-ray clusters than observed, while a COBE-normalized CDM+Lambda model (Omega =0.45, lambda =0.55, h=0.6, Omega_b =0.042, sigma_8 =0.77) and a PBI model (Omega =0.3, lambda =0.0, h=0.65, Omega_b =0.036, sigma_8 =1) both yield cluster luminosity and temperature functions consistent with observations. The CDM+Lambda and PBI models predict an order of magnitude decline in the number density of bright (hnu = 2-10keV) clusters from z=0 to z=2 in contrast to a slight increase in the number density for standard Omega =1 CDM model. We find that the temperatures of clusters in the low Omega models tend to freeze out at later times while in the Omega =1 CDM model there is a steep increase during the same interval of redshift. Equivalently, we find that L(*) of the Schechter fits of cluster luminosity functions peaks at some lower redshift (z ~ 0.3 in the CDM+Lambda model, and z ~ 1.0 in the PBI model) while in the Omega =1 CDM model it is a monotoically decreasing function of redshift. Both trends should be detectable even with a relatively ``soft" X-ray instrument such as ROSAT, providing a powerful discriminant between Omega =1 and Omega <1 models. Detailed computations of the luminosity functions in the range L_x=10(40}-10({44)) erg/s in various energy bands are presented for both cluster cores (r<= 0.5h(-1) Mpc) and total luminosities (r<1h(-1) Mpc) to be used in comparison with ROSAT and other observational data sets. These show the above noted negative evolution for the lower Omega models. We find little dependence of core radius on cluster luminosity and a correlation between temperature on luminosity similar to observations in the lower Omega models. In contrast, the standard Omega =1 model predicted temperatures which were significantly too high. Examining the ratio of gas to total mass in the clusters (which we find to be anti-biased by a factor close to unity in all the models), normalized to Omega_b h(2=0.015) , and comparing to observations, we conclude, in agreement with S. White, that the cluster observations argue for an open universe.
Cen Renyue
Ostriker Jeremiah P.
No associations
LandOfFree
X-ray Clusters as a Discriminant among Cosmological Models 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 X-ray Clusters as a Discriminant among Cosmological Models, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and X-ray Clusters as a Discriminant among Cosmological Models will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-781877