Magnetic fields in galaxies: I. Radio disks in local late-type galaxies - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




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Abstract: We develop an analytical model to follow the cosmological evolution ofmagnetic fields in disk galaxies. Our assumption is that fields are amplifiedfrom a small seed field via magnetohydrodynamical MHD turbulence. We furtherassume that this process is fast compared to other relevant timescales, andoccurs principally in the cold disk gas. We follow the turbulent energy densityusing the Shabala and Alexander 2009 galaxy formation and evolution model.Three processes are important to the turbulent energy budget: infall of coolgas onto the disk and supernova feedback increase the turbulence; while starformation removes gas and hence turbulent energy from the cold gas. Finally, weassume that field energy is continuously transferred from the incoherent randomfield into an ordered field by differential galactic rotation. Modelpredictions are compared with observations of local late type galaxies by Fittand Alexander 1993 and Shabala et al. 2008. The model reproduces observedmagnetic field strengths and luminosities in low and intermediate-massgalaxies. These quantities are overpredicted in the most massive hosts,suggesting that inclusion of gas ejection by powerful AGNs is necessary inorder to quench gas cooling and reconcile the predicted and observed magneticfield strengths.



Author: Stanislav Shabala, James M. G. Mead, Paul Alexander

Source: https://arxiv.org/







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