Astron. Astrophys. 324, 449-456 (1997)

Alfvén heating in optical filaments in cooling flows

A.C.S Friaça ¹, D.R. Gonçalves ¹, L.C. Jafelice ², V. Jatenco-Pereira ¹ and R. Opher <sup>1

1</sup> Instituto Astronômico e Geofísico, USP, Caixa Postal 9638, 01065-970, São Paulo - SP, Brazil
² Departamento de Física Teórica e Experimental, CCE-UFRN, Caixa Postal 1641, 59072-970, Natal - RN, Brazil

Received 18 March 1996 / Accepted 21 November 1996

Abstract

One of the major problems concerning cooling flows is the nature of the mechanism powering the emission lines of the optical filaments seen in the inner regions of cooling flows. In this work we investigate the plausibility of Alfvén heating (AH) as a heating/excitation mechanism of optical filaments in cooling flows. We use a time-dependent hydrodynamical code to follow the evolution of cooling condensations arising from the K cooling flow. The filaments contain magnetic fields and AH is at work at several degrees of efficiency (including no AH at all). We consider two damping mechanisms of Alfvén waves: nonlinear and turbulent. We calculate the optical line emission associated with the filaments and compare our results to the observations. We find that AH can be an important ionizing and heating source for class I filaments in the line-ratio scheme of Heckman et al. In addition, AH can be an important contributor to [OI] emission even for the more luminous class II systems.

Key words: magnetic fields turbulence galaxies: clusters cooling flows intergalactic medium X-ray: galaxies waves

Send offprint requests to: A.C.S. Friaça

© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998

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