A Strong Merger Shock in Abell 665

Dasadia, Sarthak; Sun, Ming; Sarazin, Craig L.; Morandi, Andrea; Markevitch, M.; Wik, Daniel R.; Feretti, L.; Giovannini, G.; Govoni, F.; Vacca, V.

doi:10.3847/2041-8205/820/1/l20

Cited by 48 publications

(50 citation statements)

References 43 publications

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“…The temperature and Fe abundance distributions along the merging axis show the presence of the two cold fronts as described by previous X-ray studies Govoni et al 2004;Dasadia et al 2016a). We see a slight temperature decrease across them towards the center.…”

Section: Resultssupporting

confidence: 84%

Iron abundance distribution in the hot gas of merging galaxy clusters

Urdampilleta

Mernier

Kaastra

et al. 2019

A&A

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We present XMM-Newton/EPIC observations of six merging galaxy clusters and study the distributions of their temperature, iron (Fe) abundance and pseudo-entropy along the merging axis. For the first time, we focus simultaneously, and in a comprehensive way, on the chemical and thermodynamic properties of the freshly collided intracluster medium (ICM). The Fe distribution of these clusters along the merging axis is found to be in good agreement with the azimuthally-averaged Fe abundance profile in typical non-cool-core clusters out to r 500 . In addition to showing a moderate central abundance peak, though less pronounced than in relaxed systems, the Fe abundance flattens at large radii towards ∼0.2-0.3 Z . Although this shallow metal distribution is in line with the idea that disturbed, non-cool-core clusters originate from the merging of relaxed, cool-core clusters, we find that in some cases, remnants of metal-rich and low entropy cool cores can persist after major mergers. While we obtain a mild anti-correlation between the Fe abundance and the pseudo-entropy in the (lower entropy, K = 200-500 keV cm 2 ) inner regions, no clear correlation is found at (higher entropy, K = 500-2300 keV cm 2 ) outer radii. The apparent spatial abundance uniformity that we find at large radii is difficult to explain through an efficient mixing of freshly injected metals, particularly in systems for which the time since the merger is short. Instead, our results provide important additional evidence in favour of the early enrichment scenario -in which the bulk of the metals are released outside galaxies at z > 2-3 -and extend it from cool-core and (moderate) non-cool-core clusters to a few of the most disturbed merging clusters as well. These results constitute a first step towards a deeper understanding of the chemical history of merging clusters.

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Section: Resultssupporting

confidence: 84%

Iron abundance distribution in the hot gas of merging galaxy clusters

Urdampilleta

Mernier

Kaastra

et al. 2019

A&A

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“…Possible exceptions are A2390 and A665, where the main peak of the density of passive galaxies does not have a corresponding peak in the density of star forming galaxies. Neither of these clusters appear relaxed on Fig.15 confirming earlier suggestions of their unsettled nature by Abraham et al (1996) and Markevitch & Vikhlinin (2001); Dasadia et al (2016), respectively. This supports the idea that star formation is being rapidly quenched in galaxies within merging clusters, out to R 500 .…”

Section: Distribution Of Passive Star Forming and Recently Quenchedsupporting

confidence: 75%

Galaxy evolution in merging clusters: The passive core of the “Train Wreck” cluster of galaxies, A 520

Deshev¹,

Finoguenov²,

Verdugo³

et al. 2017

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Aims. The mergers of galaxy clusters are the most energetic events in the universe after the Big Bang. With the increased availability of multi-object spectroscopy and X-ray data, an ever increasing fraction of local clusters are recognised as exhibiting signs of recent or past merging events on various scales. Our goal is to probe how these mergers affect the evolution and content of their member galaxies. We specifically aim to answer the following questions: Is the quenching of star formation in merging clusters enhanced when compared with relaxed clusters? Is the quenching preceded by a (short-lived) burst of star formation? Methods. We obtained optical spectroscopy of > 400 galaxies in the field of the merging cluster Abell 520. We combine these observations with archival data to obtain a comprehensive picture of the state of star formation in the members of this merging cluster. Finally, we compare these observations with a control sample of ten non-merging clusters at the same redshift from The Arizona Cluster Redshift Survey (ACReS). We split the member galaxies into passive, star forming or recently quenched depending on their spectra. Results. The core of the merger shows a decreased fraction of star forming galaxies compared to clusters in the non-merging sample. This region, dominated by passive galaxies, is extended along the axis of the merger. We find evidence of rapid quenching of the galaxies during the core passage with no signs of a star burst on the time scales of the merger ( 0.4 Gyr). Additionally, we report the tentative discovery of an infalling group along the main filament feeding the merger, currently at ∼2.5 Mpc from the merger centre. This group contains a high fraction of star forming galaxies as well as approximately two thirds of all the recently quenched galaxies in our survey.

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“…Additionally, to best study the shocks it is preferable to minimise the mixing of different populations of electrons along the line of sight and large spherical shocks are preferred, since for these shocks the de-projection is more accurate. As merger induced shocks in clusters are rare because the systems must be caught within a limited stage of the overall merging event, there are only a handful of known strong shocks (M X ∼ 2 − 3) that meet these conditions, namely those in Abell 520 (Markevitch et al 2005), Abell 2146 Russell et al (2011Russell et al ( , 2012, Abell 665 (Dasadia et al 2016), Abell 115 (e.g. Botteon et al 2016a), and El Gordo (Botteon et al 2016b).…”

Section: Introductionmentioning

confidence: 99%

Radio observations of the merging galaxy cluster Abell 520

Hoang

Shimwell

Weeren

et al. 2019

A&A

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Context. Extended synchrotron radio sources are often observed in merging galaxy clusters. Studies of the extended emission help us to understand the mechanisms in which the radio emitting particles gain their relativistic energies. Aims. We examine the possible acceleration mechanisms of the relativistic particles that are responsible for the extended radio emission in the merging galaxy cluster Abell 520. Methods. We performed new 145 MHz observations with the LOw Frequency ARay (LOFAR) and combined these with archival Giant Metrewave Radio Telescope (GMRT) 323 MHz and Very Large Array (VLA) 1.5 GHz data to study the morphological and spectral properties of extended cluster emission. The observational properties are discussed in the framework of particle acceleration models associated with cluster merger turbulence and shocks. Results. In Abell 520, we confirm the presence of extended (760 × 950 kpc 2 ) synchrotron radio emission that has been classified as a radio halo. The comparison between the radio and X-ray brightness suggests that the halo might originate in a cocoon rather than from the central X-ray bright regions of the cluster. The halo spectrum is roughly uniform on the scale of 66 kpc. There is a hint of spectral steepening from the SW edge towards the cluster centre. Assuming diffusive shock acceleration (DSA), the radio data are suggestive of a shock Mach number of M SW = 2.6 +0.3 −0.2 that is consistent with the X-ray derived estimates. This is in agreement with the scenario in which relativistic electrons in the SW radio edge gain their energies at the shock front via acceleration of either thermal or fossil electrons. We do not detect extended radio emission ahead of the SW shock that is predicted if the emission is the result of adiabatic compression. An X-ray surface brightness discontinuity is detected towards the NE region that may be a counter shock of Mach number M X NE = 1.52 ± 0.05. This is lower than the value predicted from the radio emission which, assuming DSA, is consistent with M NE = 2.1 ± 0.2. Conclusions. Our observations indicate that the radio emission in the SW of Abell 520 is likely effected by the prominent X-ray detected shock in which radio emitting particles are (re-)accelerated through the Fermi-I mechanism. The NE X-ray discontinuity that is approximately collocated with an edge in the radio emission hints at the presence of a counter shock.

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A Strong Merger Shock in Abell 665

Cited by 48 publications

References 43 publications

Iron abundance distribution in the hot gas of merging galaxy clusters

Iron abundance distribution in the hot gas of merging galaxy clusters

Galaxy evolution in merging clusters: The passive core of the “Train Wreck” cluster of galaxies, A 520

Radio observations of the merging galaxy cluster Abell 520

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