Journal Article

The radio properties of a complete, X-ray selected sample of nearby, massive elliptical galaxies

R. J. H. Dunn, S. W. Allen, G. B. Taylor, K. F. Shurkin, G. Gentile, A. C. Fabian and C. S. Reynolds

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 404, issue 1, pages 180-197
Published in print May 2010 | ISSN: 0035-8711
Published online April 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16314.x
The radio properties of a complete, X-ray selected sample of nearby, massive elliptical galaxies

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We investigate the radio properties of a complete sample of nearby, massive, X-ray bright elliptical and S0 galaxies. Our sample contains 18 galaxies with ROSAT All-Sky Survey X-ray fluxes FX, 0.1−2.4 keV > 3 × 10−12 erg s−1 cm−2, within a distance of 100 Mpc. For these galaxies, we have completed (18/18) Very Large Array (VLA) radio and Chandra X-ray coverage. Nuclear radio emission is detected from 17/18 of the galaxies. Ten of the galaxies exhibit extended radio emission; of these 10, all but one also exhibit clear evidence of interaction of the radio source with the surrounding, X-ray emitting gas. Among the seven galaxies with unresolved radio sources, one has clear, and one has small, cavity-like features in the Chandra X-ray images; a third has a disturbed X-ray morphology. Using a radio luminosity limit equivalent to L1.4 GHz > 1023 W Hz−1 to calculate the radio-loud fraction, we find that this misses the majority of the radio detected galaxies in the sample. We determine integrated radio-to-X-ray flux ratios for the galaxies, , which are shown to span a large range (a factor of 100). We calculate the mass-weighted cooling times within 1 kpc, and find hints for an anticorrelation with the radio luminosity. We also calculate limits on k/f, where k is the ratio of the total particle energy to that of relativistic electrons radiating in the range 10 MHz–10 GHz and f is the volume filling factor of the plasma in the cavity. The k/f distribution is also broad, reflecting previous results for larger galaxy clusters. Lowering the X-ray flux limit, at the expense of less complete VLA and Chandra coverage, increases the size of our sample to 42 galaxies. Nuclear radio activity is detected in at least 34/42 of this extended sample.

Keywords: galaxies: active; galaxies: elliptical and lenticular, cD; galaxies: jets

Journal Article.  13109 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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