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A&A 421, 815-819 (2004)
DOI: 10.1051/0004-6361:20040224
Quasi-hydrostatic intracluster gas under radiative cooling
K. Masai1 and T. Kitayama21 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
(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 ~
1/3 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.
Key words: galaxies: clusters: general -- cooling flows
Offprint request: K. Masai, masai@phys.metro-u.ac.jp
© ESO 2004