## The Distance and Mass of the Galaxy Cluster Abell 1995 Derived from Sunyaev-Zel'dovich Effect and X-ray Measurements''

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Abstract

We present multi-wavelength observations of the Abell 1995 galaxy cluster. From analysis of x-ray spectroscopy and imaging data we derive the electron temperature, cluster core radius, and central electron number density. Using optical spectroscopy of 15 cluster members, we derive an accurate cluster redshift and velocity dispersion. Finally, the interferometric imaging of the SZE toward Abell 1995 at 28.5 GHz provides a measure of the integrated pressure through the cluster.

The x-ray and SZE observations are combined to determine the angular diameter distance to the cluster of D_A=1294(+297-286) (+438-459) Mpc (statistical followed by systematic uncertainty), implying a Hubble constant of H_0=52(+/-12)(+/-18)km/s/Mpc for OmegaM=0.3 and OmegaL=0.7. We find a best fit H0 of 46km/s/Mpc for the OmegaM=1 cosmology, and 48km/s/Mpc for OmegaM=0.3.

The x-ray data are also used to derive a total cluster mass of M_tot^HSE=5.18(+0.62-0.48)x10^{14} h^{-1}M_o; the optical velocity dispersion yields an independent and consistent estimate of M_{tot}^{virial}(\rad)=6.35^{+1.51}_{-1.19}x10^{14} h^{-1}M_o$. Both of the total mass estimates are evaluated at a fiducial radius of 830 h^{-1}$ kpc, where the overdensity is 500 times the critical density. The total cluster mass is then combined with gas mass measurements to determine a cluster gas mass fraction of $f_g=0.056^{+0.010}_{-0.013} h^{-3/2}$. In combination with recent baryon density constraints, the measured gas mass fraction yields an upper limit on the mass density parameter Omega_M h^{1/2} \leq 0.34 ^{+0.06}_{-0.05}.