An X-ray and optical study of matter distribution in the galaxy cluster A2319

A new analysis of velocity distribution, optical photometry, and X-ray surf ace brightness from ROSAT Position Sensitive Proportional Counter data of t he galaxy cluster A2319 is presented. The temperature profile recently deri ved from ASCA data by Markevitch is taken into account. A method to check t he hydrostatic model in the presence of a temperature gradient is proposed. Consistency of the hydrostatic isothermal model and the explanation of the "beta-discrepancy" are discussed. Galaxy and gas density profiles of the m ain component A2319A are derived, allowing for the effect of the secondary component A2319B. The inadequacy of a polytropic model, which would produce a binding mass decrease with respect to the isothermal beta-model, is disc ussed. A simple interpolation of the temperature profile provides instead a n increase of the binding mass and a lower baryon fraction, thus mitigating the "baryon catastrophe." Assuming as typical the value f(b) approximate t o 0.2, a comparison with the most recent estimate of Omega(b)(nucl) implies for the cosmological parameter Omega(0) less than or similar to 0.4.