Spectral index maps of the radio halos in Abell 665 and Abell 2163

Feretti, L.; Orrù, E.; Brunetti, G.; Giovannini, G.; Kassim, N. E.; Setti, G.

doi:10.1051/0004-6361:20040316

Cited by 83 publications

(33 citation statements)

References 30 publications

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“…The observed correlations between extended radio emission and cluster mergers favour electron reacceleration models (e.g. Buote 2001; Feretti et al 2004; Feretti & Giovannini 2008). Recent observations suggest that radio haloes are likely generated by turbulent processes induced by a merger (e.g.…”

Section: Introductionmentioning

confidence: 73%

“…Observational results have so far suggested a strong connection between merging clusters hosting shock fronts and extended radio emission in the form of relics or haloes (e.g. Giovannini, Tordi & Feretti 1999; Govoni et al 2001a; Feretti et al 2004; Venturi et al 2007; Giacintucci et al 2008; Markevitch 2010; van Weeren et al 2009, 2010, 2011). We therefore consider possible explanations for the lack of extended radio emission in Abell 2146.…”

Section: Discussionmentioning

confidence: 99%

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A merger mystery: no extended radio emission in the merging cluster Abell 2146

Russell¹,

Weeren²,

Edge³

et al. 2011

Monthly Notices of the Royal Astronomical Society: Letters

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We present a new 400 ks Chandra X‐ray observation and a Giant Metrewave Radio Telescope (GMRT) radio observation at 325 MHz of the merging galaxy cluster Abell 2146. The Chandra observation reveals detailed structure associated with the major merger event including the Mach M= 2.1 ± 0.2 bow shock located ahead of the dense subcluster core and the first known example of an upstream shock (M= 1.6 ± 0.1). Surprisingly, the deep GMRT observation at 325 MHz does not detect any extended radio emission associated with either shock front. All other merging galaxy clusters with X‐ray‐detected shock fronts, including the Bullet cluster, Abell 520, Abell 754 and Abell 2744, and clusters with candidate shock fronts have detected radio relics or radio halo edges coincident with the shocks. We consider several possible factors which could affect the formation of radio relics, including the shock strength and the presence of a pre‐existing electron population, but do not find a favourable explanation for this result. We calculate a 3σ upper limit of 13 mJy on extended radio emission, which is significantly below the radio power expected by the observed Pradio–LX correlation for merging systems. The lack of an extended radio halo in Abell 2146 maybe due to the low cluster mass relative to the majority of merging galaxy clusters with detected radio haloes.

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Section: Introductionmentioning

confidence: 73%

Section: Discussionmentioning

confidence: 99%

A merger mystery: no extended radio emission in the merging cluster Abell 2146

Russell¹,

Weeren²,

Edge³

et al. 2011

Monthly Notices of the Royal Astronomical Society: Letters

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“…A665 is thus an example of a likely BHOM (see ) missed by the set of diagnostics used by us here because the merger axis is nearly aligned with our line of sight. This merger too is giving rise to non‐thermal emission in the form of a well‐studied synchrotron radio halo (Markevitch & Vikhlinin 2001; Feretti et al 2004; Vacca et al 2010).…”

Section: Resultsmentioning

confidence: 99%

X-ray-optical classification of cluster mergers and the evolution of the cluster merger fraction

Mann

Ebeling

2012

Monthly Notices of the Royal Astronomical Society

218

326

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We present the results of a simple but robust morphological classification of a statistically complete sample of 108 of the most X‐ray‐luminous clusters at 0.15 ≤z≤ 0.7 observed with Chandra. Our aims are to (a) identify the most disturbed massive clusters to be used as gravitational lenses for studies of the distant Universe and as probes of particle acceleration mechanisms resulting in non‐thermal radio emission; (b) find cluster mergers featuring subcluster trajectories that make them suitable for quantitative analyses of cluster collisions; and (c) constrain the evolution with redshift of the cluster merger fraction. Finally, (d) this paper represents the third public release of clusters from the MAssive Cluster Survey sample, adding 24 clusters to the 46 published previously. To classify clusters by the degree of relaxation, we use the projected offset of the brightest cluster galaxy from the peak (or the global centroid) of the X‐ray emission as a measure of the segregation between the intracluster gas and dark matter, and also perform a visual assessment of the optical and X‐ray morphology on all scales. Regarding (a), we identify 10 complex systems likely to have undergone multiple merger events in the recent past. Regarding (b), we identify 11 systems likely to be post‐collision, binary, head‐on mergers (BHOMs), as well as another six mergers that are possible BHOMs but probably harder to interpret because of non‐negligible impact parameters and merger axes closer to our line of sight. Regarding (c), we find a highly significant increase with redshift in the fraction of morphologically disturbed clusters (and thus a clear decrease in the number of fully relaxed systems) starting at z∼ 0.4, in spite of a detection bias in our sample against very disturbed systems at high redshift. Since our morphological diagnostics are all based on imaging data and thus sensitive to projection effects, the measured merger fractions should be considered lower limits and our list of mergers incomplete, as we are likely to miss systems forming along axes close to our line of sight. A larger sample of clusters with high‐quality X‐ray data in particular at high redshift will be needed to trace the evolutionary history of cluster growth and relaxation closer to the primary epoch of cluster formation z∼ 1.

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“…References: (1) Faint Images of the Radio Sky at Twenty centimetres (FIRST; Becker et al ); (2) The NRAO VLA Sky Survey (NVSS) at 1.4 GHz (Condon et al ); (3) The Sydney University Molonglo Sky Survey (SUMSS) at 843 MHz (Bock et al ); (4) TIFR GMRT Sky Survey (TGSS) by S. K. Sirothia, N. G. Kantharia, C. H. Ishwara‐Chandra and Gopal‐Krishna; (5) Andersson & Madejski (); (6) Bagchi et al (); (7) Baldi et al (); (8) Baum & O'Dea (); (9) Belsole et al (); (10) Berrington, Lugger & Cohn (); (11) Bîrzan et al (); (12) Bravo‐Alfaro et al (); (13) Buote, Humphrey & Stocke (); (14) Burgett et al (); (15) Burns (); (16) Burns et al (); (17) Carilli et al (); (18) Carretti et al (); (19) Clarke, Blanton & Sarazin (); (20) Clarke et al (); (21) Clarke & Ensslin ; (22) Clarke et al (); (23) Chatzikos, Sarazin & Kempner (); (24) Churazov et al (); (25) Cortese et al (); (26) Cotton et al (); (27) Davis & Mushotzky (); (28) David et al (); (29) de Plaa et al (); (30) de Ruiter et al (); (31) Dong et al (); (32) Donnelly et al (); (33) Donnelly et al (); (34) Dunn et al (); (35) Dupke et al ; (36) Dupke et al (); (37) Durret, Lima Neto & Forman (); (38) Fabian et al (); (39) Fabian et al (); (40) Feretti et al (); (41) Feretti et al (); (42) Feretti et al (); (43) Finoguenov et al (); (44) Finoguenov et al (); (45) Gastaldello et al (); (46) Ge & Owen (); (47) Gentile et al (); (48) Ghizzardi et al (); (49) Giacintucci et al (); (50) Giacintucci et al (); (51) Giacintucci et al (); (52) Giovannini et al (); (53) Giovannini et al (); (54) Govoni et al (); (55) Govon...…”

Section: Sample Definition and Propertiesmentioning

confidence: 99%

The duty cycle of radio-mode feedback in complete samples of clusters

Bîrzan

Rafferty

Nulsen

et al. 2012

Monthly Notices of the Royal Astronomical Society

104

113

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The Chandra X-ray Observatory has revealed X-ray bubbles in the intracluster medium (ICM) of many nearby cooling flow clusters. The bubbles trace feedback that is thought to couple the central active galactic nucleus (AGN) to the ICM, helping to stabilize cooling flows and govern the evolution of massive galaxies. However, the prevalence and duty cycle of such AGN outbursts is not well understood. To this end, we study how cooling is balanced by bubble heating for complete samples of clusters (the Brightest 55 clusters of galaxies, hereafter B55, and the HIghest X-ray FLUx Galaxy Cluster Sample, HIFLUGCS). We find that the radio luminosity of the central galaxy only exceeds 2.5 x 10^30 erg s^-1 Hz^-1 in cooling flow clusters. This result implies a connection between the central radio source and the ICM, as expected if AGN feedback is operating. Additionally, we find a duty cycle for radio mode feedback, the fraction of time that a system possesses bubbles inflated by its central radio source, of > 69 per cent for B55 and > 63 per cent for HIFLUGCS. These duty cycles are lower limits since some bubbles are likely missed in existing images. We used simulations to constrain the bubble power that might be present and remain undetected in the cooling flow systems without detected bubbles. Among theses systems, almost all could have significant bubble power. Therefore, our results imply that the duty cycle of AGN outbursts with the potential to heat the gas significantly in cooling flow clusters is at least 60 per cent and could approach 100 per cent.Comment: Accepted to MNRAS, 24 pages, 5 figure

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Spectral index maps of the radio halos in Abell 665 and Abell 2163

Cited by 83 publications

References 30 publications

A merger mystery: no extended radio emission in the merging cluster Abell 2146

A merger mystery: no extended radio emission in the merging cluster Abell 2146

X-ray-optical classification of cluster mergers and the evolution of the cluster merger fraction

The duty cycle of radio-mode feedback in complete samples of clusters

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