Journal Article

The energy source of the filaments around the giant galaxy NGC 1275

A. C. Fabian, J. S. Sanders, R. J. R. Williams, A. Lazarian, G. J. Ferland and R. M. Johnstone

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 417, issue 1, pages 172-177
Published in print October 2011 | ISSN: 0035-8711
Published online October 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19034.x
The energy source of the filaments around the giant galaxy NGC 1275

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The brightest galaxy in the nearby Perseus cluster, NGC 1275, is surrounded by a network of filaments. These were first observed through their Hα emission but are now known to have a large molecular component with a total mass approaching 1011 M of gas. The filaments are embedded in hot intracluster gas and stretch over 80 kpc. They have an unusually low excitation spectrum which is well modelled by collisional heating and ionization by secondary electrons. Here we note that the surface radiative flux from the outer filaments is close to the energy flux impacting on them from particles in the hot gas. We propose that the secondary electrons within the cold filaments, which excite the observed submillimetre through ultraviolet emission, are due to the hot surrounding gas efficiently penetrating the cold gas through reconnection diffusion. Some of the soft X-ray emission seen from the filaments is then due to charge exchange, although this is insufficient to account for all the observed X-ray flux. The filaments are complex with multiphase gas. Interpenetration of hot and cold gases leads to the filaments growing in mass, at a rate of up to 100 M yr−1. The lack of soft X-ray cooling emission in cool core clusters is then due to the non-radiative cooling of hot gas on mixing with cold gas around and within the central galaxy.

Keywords: galaxies: clusters: intracluster medium; galaxies: individual: NGC 1275; intergalactic medium; X-rays: galaxies

Journal Article.  5391 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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