A STUDY OF THE DARK CORE IN A520 WITH THE<i>HUBBLE SPACE TELESCOPE</i>: THE MYSTERY DEEPENS

Jee, M. James; Mahdavi, Andisheh; Hoekstra, Henk; Babul, Arif; Dalcanton, Julianne J.; Carroll, P.; Capak, P.

doi:10.1088/0004-637x/747/2/96

Cited by 93 publications

(97 citation statements)

References 36 publications

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“…These authors suggested that this cluster is a dynamically young system and that the extensions are related to clumps of galaxies that collide on a darkmatter gravitational well that is located at the center of the X-ray emission region. This insight has been confirmed by the analysis of Jee et al (2012). By means of high-resolution weaklensing studies carried out with Hubble Space Telescope data, they mapped a filamentary structure 1.5 Mpc in size elongated in the NE-SW direction and confirmed the dark-matter core with a significance higher than 10σ.…”

Section: Galaxy Cluster Abell 520mentioning

confidence: 63%

Spectral index image of the radio halo in the cluster Abell 520, which hosts the famous bow shock

Vacca

Feretti

Giovannini

et al. 2013

A&A

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Context. Synchrotron-radio emission has been detected from an increasing number of galaxy clusters. Spectral index images are a powerful tool for investigating the origin and nature of these sources, and their connection with the dynamical state of the cluster. Aims. The aim of this work is to investigate the spectral index distribution of the radio halo in the galaxy cluster A520, known to be a complex system from an optical, radio, and X-ray point of view. Methods. We present deep Very Large Array observations in total intensity at 325 and 1400 MHz. We produced and analyzed spectral index images of the radio halo in this frequency range at a resolution of 39 and 60 and determined possible correlations with the thermal properties of the cluster. Results. We found an integrated radio-halo spectral index α 1400 325 ∼ 1.12. No strong radial steepening is present and the spectral index distribution is intrinsically complex with fluctuations only partially due to measurement errors. The radio-halo-integrated spectral index and the cluster temperature follow the general trend observed in other galaxy clusters, although a strong point-to-point correlation between the spectral index and the thermal gas temperature has not been observed. Conclusions. The complex morphology in the spectral index image of the radio halo in A520 agrees with the primary models for radio-halo formation. The flatness of the radial profile suggests that the merger is still ongoing and is uniformly and continuously (re-) accelerating the population of relativistic electrons responsible of the radio emission even at large (∼1 Mpc) distances from the cluster center.

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Section: Galaxy Cluster Abell 520mentioning

confidence: 63%

Spectral index image of the radio halo in the cluster Abell 520, which hosts the famous bow shock

Vacca

Feretti

Giovannini

et al. 2013

A&A

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“…luminous matter, which is the opposite behaviour to the Bullet Cluster (Failure 17 above, Jee et al 2012, see also Mahdavi et al 2007).…”

Section: Generic Failures Of Inflationary Bb Models?mentioning

confidence: 95%

“…They write 'we conclude that it is intriguing that the minimum mass of SN particle that can match the CMB is the same as the minimum mass found here to be consistent with equilibrium configurations of Milgromian clusters of galaxies.' 16 The Train-Wreck Cluster (Abell 520) has been shown to be incompatible with the SMoC because the putative C/WDM particles have separated from the galaxies such that a core of DM is left (Mahdavi et al 2007;Jee et al 2012). While these authors speculate on a possible solution such as DM possibly having a self-interaction property (but see Section 15.2), in a Milgromian cosmological model with HDM it is conceivable for the selfbound galaxy-cluster-sized HDM core to dissociate itself from the baryonic matter in galaxies, which individually would remain on the BTF relation.…”

Section: The Bullet and Train-wreck Clustersmentioning

confidence: 99%

The Dark Matter Crisis: Falsification of the Current Standard Model of Cosmology

Kroupa¹

2012

Publ. – Astron. Soc. Aust

243

275

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Abstract:The current standard model of cosmology (SMoC) requires The Dual Dwarf Galaxy Theorem to be true according to which two types of dwarf galaxies must exist: primordial dark-matter (DM) dominated (type A) dwarf galaxies, and tidal-dwarf and ram-pressure-dwarf (type B) galaxies void of DM. Type A dwarfs surround the host approximately spherically, while type B dwarfs are typically correlated in phasespace. Type B dwarfs must exist in any cosmological theory in which galaxies interact. Only one type of dwarf galaxy is observed to exist on the baryonic Tully-Fisher plot and in the radius-mass plane. The Milky Way satellite system forms a vast phase-space-correlated structure that includes globular clusters and stellar and gaseous streams. Other galaxies also have phase-space correlated satellite systems. Therefore, The Dual Dwarf Galaxy Theorem is falsified by observation and dynamically relevant cold or warm DM cannot exist. It is shown that the SMoC is incompatible with a large set of other extragalactic observations. Other theoretical solutions to cosmological observations exist. In particular, alone the empirical mass-discrepancyacceleration correlation constitutes convincing evidence that galactic-scale dynamics must be Milgromian. Major problems with inflationary big bang cosmologies remain unresolved.

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“…All these studies show a picture of two sub-clusters observed after the core passage and currently separated by ∼4.5 on the sky (∼0.8Mpc) along a NE-SW axis. These sub-clusters are named P2 and P4 by Jee et al (2012) and we use these names throughout this article. Their positions are indicated on Fig. 14.…”

Section: The Merging Cluster Abell 520mentioning

confidence: 99%

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

Deshev¹,

Finoguenov²,

Verdugo³

et al. 2017

A&A

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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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A STUDY OF THE DARK CORE IN A520 WITH THEHUBBLE SPACE TELESCOPE: THE MYSTERY DEEPENS

Cited by 93 publications

References 36 publications

Spectral index image of the radio halo in the cluster Abell 520, which hosts the famous bow shock

Spectral index image of the radio halo in the cluster Abell 520, which hosts the famous bow shock

The Dark Matter Crisis: Falsification of the Current Standard Model of Cosmology

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

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