Letter to the Editor
A morphological comparison between giant radio halos and radio mini-halos in galaxy clusters
INAF - Istituto di Radioastronomia, via P. Gobetti 101, 40129 Bologna, Italy e-mail: email@example.com
2 INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
Accepted: 9 June 2008
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-LX, and radio luminosity-size, P1.4-RH, correlations. We report evidence that P1.4-LX and P1.4-RH trends may also exist for mini-halos: mini-halo clusters share the same region of giant halo clusters in the plane, whereas they are clearly separated in the 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