The temperature and distribution of gas in CL 0016 + 16 measured with

We present results of a 37 ks observation of CL 0016+16 with the XMM-Newton EPIC instrument. Within 1.5 arcmin of the cluster centre we measure a gas temperature of kT = 9.13 +0.24 −0.22 keV and an abundance of 0.22 +0.04 −0.03 times the solar value (1σ uncertainties). This significant improvement over previous measurements has allowed us to revise the estimate of the Hubble constant based on CL 0016+16 to 68 ± 8 km s −1 Mpc −1 (random error only), close to the value from the Hubble Space Telescope distance-scale project. The total gravitating mass within a radius of 248 kpc of the cluster centre is in good agreement with that found from gravitational lensing over the same region, supporting the assumption of isother-mal gas in hydrostatic equilibrium. The gas mass fraction of 0.13 ± 0.02 is in remarkable agreement with that given by cosmological parameters for the Universe as a whole, suggesting that CL 0016+16 is a fair sample of the matter content of the Universe. While there is no spectral or spatial evidence to suggest a cooling flow in CL 0016+16, we find an asymmetrical central X-ray structure which may have a harder spectrum than the cluster as a whole, and be evidence for some merger activity, in addition to a previously reported asymmetry to the west of the cluster. The nearest companion cluster to CL 0016+16 is measured to have a gas temperature of kT = 3.8 −0.2 times the solar value (1σ uncertainties). We also present spectral data for the companion quasar whose spectrum was confused with CL 0016+16 in previous ASCA data.