Galaxy Cluster Virial Masses and Omega

Abstract

To re-examine the rich cluster $\Omega$ value the CNOC Cluster Survey has observed 16 high X-ray luminosity clusters in the redshift range 0.17 to 0.55, obtaining approximately 2600 velocities in their fields. Directly adding all the K and evolution corrected $r$ band light to $M_r(0)=-18.5$, about $0.2L_\ast$, and correcting for the light below the limit, the average mass-to-light ratio of the clusters is $283\pm27h\msun/\lsun$ and the average mass per galaxy is $3.5\pm0.4\times10^{12}h^{-1}\msun$. The clusters are consistent with having a universal $M_v/L$ value (within the errors of about 20\%) independent of their velocity dispersion, mean color of their galaxies, blue galaxy content, redshift, or mean interior density. Using field galaxies within the same data set, with the same corrections, we find that the closure mass-to-light, $\rho_c/j$, is $1160\pm130h\msun/\lsun$ and the closure mass per galaxy, $\rho_c/\phi(>0.2L_\ast)$, is $13.2\pm1.9\times10^{12}h^{-1}\msun$. Under the assumptions that the galaxies are distributed like the mass and that the galaxy luminosities and numbers are statistically conserved, which these data indirectly support, $\Omega_0=0.20\pm0.04\pm0.09$ where the errors are, respectively, the $1\sigma$ internal and an estimate of the $1\sigma$ systematic error resulting from the luminosity normalization.Comment: 34 page Latex document (no figures) requiring AAS macros. Postscript document (or uufile) availble at http://manaslu.astro.utoronto.ca/~carlberg/cnoc/general.htm

A Measurement of the Density Parameter Derived from the Evolution of Cluster X-Ray Temperatures

“…We are impressed that all recent cluster measurements of , including the traditional M/L anal-Q 0 ysis (Carlberg et al 1996), a PS analysis of velocity dispersions (Carlberg et al 1997), and the baryon fraction (White et al 1993b), yield consistent results. Whether the prediction of the simplest inflation models that the universe is spatially flat will suffer the same fate as the closed model is not yet known.…”

The z=2.72 galaxy cB58: a gravitational fold arc lensed by the cluster MS 1512+36

“…Since the cluster velocity dispersion is in agreement with the value of Carlberg et al (1996 a&b), this is also the case for the total mass estimate and the mass to light ratio of the cluster: i) if we consider only the velocity dispersions σ cl ≈ 600km/s and σ dyn = (690 ± 100)km/s derived from lensing and peculiar velocities and ignore the asymmetry for the mass estimate within the virial radius, the lensing mass is 75% of the dynamical mass, but of course compatible to it within the error bars. ii) Including all galaxies considered for the light deflection, we obtain (for a Einstein-de Sitter cosmology) a mass within chip-3 of ≈ 8 * 10 13 h −1 50 Mø, which transfers to a mass of 1 * 10 15 h −1 50 Mø within the virial radius of 1.803h −1 100 Mpc (Carlberg et al 1996b), if the combined mass profile of the cluster and its galaxies is isothermal out to the virial radius. The Carlberg et al (1996a) value is 5.5 * 10 14 h −1 100 Mø (for Ω = 0.2) and this estimate decreases by about 10 percent if one uses Ω = 1.…”

Measuring Omega0 using cluster evolution

“…Donahue 1996;Mushotzky & Scharf 1997;Henry 1997) and ROSAT (Ebeling et al 1997, Burke et al 1997, Rosati et al 1998) measurements of the X-ray emitting intracluster plasma now complement the low-redshift studies carried out by Edge et al (1990) and David et al (1993). In addition, the CNOC survey provides galaxy velocity dispersions for a well-defined sample of high-redshift clusters (Carlberg et al 1996) and further information on mass distributions is coming from weak gravitational lensing measurements (e.g. Luppino & Kaiser 1997;Smail et al 1997).…”