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Astron. Astrophys. 345, 723-732 (1999)

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Thermal equilibrium of molecular clouds in cooling flow clusters

Denis Puy, Lukas Grenacher and Philippe Jetzer

1 Paul Scherrer Institute, Laboratory for Astrophysics, CH-5232 Villigen PSI, Switzerland
2 Institute of Theoretical Physics, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland

Received 3 August 1998 / Accepted 18 February 1999


In many clusters of galaxies there is evidence for cooling flows in the central regions. The ultimate fate of the gas which cools is still unknown. A possibility is that a fraction of the gas forms cold molecular clouds. We investigate the minimum temperature which can be reached by clouds in cooling flows by computing the cooling function due to [FORMULA], HD and CO molecules. As an example, we determine the minimum temperature achievable by clouds in the cooling flows of the Centaurus, Hydra and PKS 0745-191 clusters. Our results suggest that clouds can reach very low temperatures - less than [FORMULA] K - which would explain the non-detection of CO in these clusters.

Key words: molecular processes – galaxies: clusters: general – galaxies: cooling flows – X-rays: general

Send offprint requests to: puy@physik.unizh.ch

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© European Southern Observatory (ESO) 1999

Online publication: April 28, 1999