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000002334 0247_ $$2DOI$$a10.1111/j.1365-2966.2008.14153.x
000002334 037__ $$aASTROimport-491
000002334 100__ $$aFerland, G. J.
000002334 245__ $$aCollisional heating as the origin of filament emission in galaxy clusters
000002334 260__ $$c2009
000002334 520__ $$aIt has long been known that photoionization, whether by starlight or other sources, has difficulty in accounting for the observed spectra of the optical filaments that often surround central galaxies in large clusters. This paper builds on the first of this series in which we examined whether heating by energetic particles or dissipative magnetohydrodynamic (MHD) wave can account for the observations. The first paper focused on the molecular regions which produce strong H2 and CO lines. Here we extend the calculations to include atomic and low-ionization regions. Two major improvements to the previous calculations have been made. The model of the hydrogen atom, along with all elements of the H-like iso-electronic sequence, is now fully nl-resolved. This allows us to predict the hydrogen emission-line spectrum including excitation by suprathermal secondary electrons and thermal electrons or nuclei. We show how the predicted HI spectrum differs from the pure-recombination case. The second update is to the rates for H0-H2 inelastic collisions. We now use the values computed by Wrathmall et al. The rates are often much larger and allow the ro-vibrational H2 level populations to achieve a thermal distribution at substantially lower densities than previously thought. We calculate the chemistry, ionization, temperature, gas pressure and emission-line spectrum for a wide range of gas densities and collisional heating rates. We assume that the filaments are magnetically confined. The gas is free to move along field lines so that the gas pressure is equal to that of the surrounding hot gas. A mix of clouds, some being dense and cold and others hot and tenuous, can exist. The observed spectrum will be the integrated emission from clouds with different densities and temperatures but the same pressure P/k = nT. We assume that the gas filling factor is given by a power law in density. The power-law index, the only free parameter in this theory, is set by matching the observed intensities of infrared H2 lines relative to optical HI lines. We conclude that the filaments are heated by ionizing particles, either conducted in from surrounding regions or produced in situ by processes related to MHD waves. Contains material © British Crown copyright 2008/MoD. E-mail: gjferland@gmail.com 
000002334 700__ $$a Fabian, A. C.
000002334 700__ $$a Hatch, N. A.
000002334 700__ $$a Johnstone, R. M.
000002334 700__ $$a Porter, R. L.
000002334 700__ $$a van Hoof, P. A. M.
000002334 700__ $$a Williams, R. J. R.
000002334 773__ $$c1475-1502$$i4$$pMonthly Notices of the Royal Astronomical Society$$v392$$y2009
000002334 85642 $$ahttp://esoads.eso.org/abs/2009MNRAS.392.1475F
000002334 905__ $$apublished in
000002334 980__ $$aREFERD