EDP Sciences
Free access
Issue
A&A
Volume 486, Number 3, August II 2008
Page(s) L31 - L34
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200810179
Published online 16 June 2008


A&A 486, L31-L34 (2008)
DOI: 10.1051/0004-6361:200810179

Letter

A morphological comparison between giant radio halos and radio mini-halos in galaxy clusters

R. Cassano1, M. Gitti2, and G. Brunetti1

1  INAF - Istituto di Radioastronomia, via P. Gobetti 101, 40129 Bologna, Italy
    e-mail: rcassano@ira.inaf.it
2  INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy

Received 12 May 2008 / Accepted 9 June 2008

Abstract
In this letter we present a morphological comparison between giant radio halos and radio mini-halos in galaxy clusters based on radio-X-ray luminosity, P1.4-$L_{\rm X}$, and radio luminosity-size, P1.4-$R_{\rm H}$, correlations. We report evidence that P1.4-$L_{\rm X}$ and P1.4-$R_{\rm H}$ trends may also exist for mini-halos: mini-halo clusters share the same region of giant halo clusters in the $(P_{1.4},L_{\rm X})$ plane, whereas they are clearly separated in the $(P_{1.4},R_{\rm H})$ plane. The synchrotron emissivity of mini-halos is found to be more than 50 times larger than that of giant halos, implying a very efficient process for their origins. By assuming a scenario of sporadical turbulent particle re-acceleration for both giant and mini halos, we discuss basic physical differences between these sources. Regardless of the origin of the turbulence, a more efficient source of injection of particles, which eventually takes part in the re-acceleration process, is required in mini-halos, and this may result from the central radio galaxy or from proton-proton collisions in the dense cool core regions.


Key words: radiation mechanism: non-thermal -- galaxies: clusters: general -- radio continuum: general -- X-rays: general



© ESO 2008