Quasi-hydrostatic intracluster gas under radiative cooling

¹ Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
² Department of Physics, Toho University, Miyama, Funabashi, Chiba 274-8510, Japan e-mail: kitayama@ph.sci.toho-u.ac.jp

Corresponding author: K. Masai, masai@phys.metro-u.ac.jp

Received: 19 February 2004
Accepted: 23 March 2004

Abstract

Quasi-hydrostatic cooling of the intracluster gas is studied. In the quasi-hydrostatic model, work done by gravity on the inflow gas with , where P is the gas pressure, is taken into account in the thermal balance. The gas flows in from the outer part so as to compensate the pressure loss of the gas undergoing radiative cooling, but the mass flow is so moderate and smooth that the gas is considered to be quasi-hydrostatic. The temperature of the cooling gas decreases toward the cluster center, but, unlike cooling flows with , approaches a constant temperature of ~ the temperature of the non-cooling ambient gas. This does not mean that gravitational work cancels out radiative cooling, but means that the temperature of the cooling gas appears to approach a constant value toward the cluster center if the gas maintains the quasi-hydrostatic balance. We discuss the mass flow in quasi-hydrostatic cooling, and compare it with the standard isobaric cooling flow model. We also discuss the implication of  for the standard cooling flow model.