On the Origin of Radio Halos in Galaxy Clusters

By D. Buote. 2001

155 citations recorded by the source corpus.

Previously, it has been recognized that radio halos in galaxy clusters are preferentially associated with merging systems, as indicated by substructure in the X-ray images and temperature maps. Since, however, many clusters without radio halos also possess substructure, the role of mergers in the formation of radio halos has remained unclear. By using power ratios to relate gravitational potential fluctuations to substructure in X-ray images, we provide the first quantitative comparison of the dynamical states of clusters possessing radio halos. A correlation between the 1.4 GHz power (P1.4) of the radio halo (or relic) and the magnitude of the dipole power ratio (P1/P0) is discovered such that approximately P1.4 ∝ P1/P0; i.e., the strongest radio halos appear only in those clusters currently experiencing the largest departures from a virialized state. From the additional consideration of a small number of highly disturbed clusters without radio halos detected at 1.4 GHz and recalling that radio halos are more common in clusters with high X-ray luminosity (Giovannini, Tordi, & Feretti), we argue that radio halos form preferentially in massive (LX ≳ 0.5 × 1045 ergs s-1) clusters experiencing violent mergers (P1/P0 ≳ 0.5 × 10-4) that have seriously disrupted the cluster core. The association of radio halos with massive, large-P1/P0, core-disrupted clusters can account for both the vital role of mergers in accelerating the relativistic particles responsible for the radio emission as well as the rare occurrence of radio halos in cluster samples.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/b1e3048d5d32544599965fa0735eabf15f365ccc

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Citations in the corpus

Turbulent gas motions in galaxy cluster simulations: the role of smoothed particle hydrodynamics viscosity (2005, background): “In addition, the occurrence of non–thermal phenomena is found to be related to the dynamical state and mass of the parent cluster (Giovannini et al. 1999; Buote 2001; Schuecker et al. 2001; Feretti 2002), which suggests a connection between cluster mergers and non–thermal activity.”
Radio and X-ray diffuse emission in six clusters of galaxies (2001, background): “The cluster mass is a logical candidate for a fundamental parameter since the energy available to accelerate relativistic particles in a merger scales as ≃ M2 as discussed by Buote (2001).”
Bow Shock and Radio Halo in the Merging Cluster A520 (2004, background): “The close relation between halos and mergers has been extensively discussed (e.g., Feretti 2002; Buote 2001; Markevitch & Vikhlinin 2001; Govoni et al. 2004, hereafter G04).”
Massive and refined - II. The statistical properties of turbulent motions in massive galaxy clusters with high spatial resolution (2010, background): “These emissions are found preferentially in X-ray luminous galaxy clusters (e.g. Giovannini, Tordi & Feretti 1999; Venturi et al. 2008; Giovannini et al. 2009) and only in systems with a X-ray perturbed morphology, showing indications of merger activity (Buote 2001).”
Diffuse Radio Emission from Galaxy Clusters (2019, methodology): “Giant Mpc-size radio halos are mostly found in massive dynamically disturbed clusters (Giovannini et al. 1999; Buote 2001; Cassano et al. 2010b).”
GMRT radio halo survey in galaxy clusters at z = 0.2–0.4 - II. The eBCS clusters and analysis of the complete sample (2008, background): “…phenomena, and indeed there is observational evidence that radio halos are found in clusters with signatures of ongoing merging processes (e.g. Buote 2001; Schuecker et al. 2001), and that the occurrence of radio halos increases with the X–ray luminosity of the parent clusters (Giovannini…”
ON THE CONNECTION BETWEEN GIANT RADIO HALOS AND CLUSTER MERGERS (2010, background): “In particular, in a seminal paper Buote (2001) provided the first quantitative comparison of the dynamical states of clusters with RH discovering a correlation between the RH luminosity at 1.4 GHz and the magnitude of the dipole power ratio P1/P0.”
Cosmic ray transport in galaxy clusters: implications for radio halos, gamma-ray signatures, and cool core heating (2010, background): “11 Buote (2001); Schuecker et al. (2001); Markevitch & Vikhlinin (2001); Govoni et al. (2004); Venturi et al. (2008); Cassano et al. (2010). clusters, as the re-accelerated CRe could be injected by hadronic CRp-gas interactions (Brunetti & Blasi 2005).”
Cluster Magnetic Fields (2001, background): “…images of the hot cluster atmosphere, indicative of merging clusters, and a corresponding anti-correlation between cluster radio halos and clusters with relaxed morphologies, e.g., cooling flows (Govoni et al. 2001a), although these correlations are just beginning to be quantified (Buote 2001).”