Discovery of a Dissociative Galaxy Cluster Merger With Large Physical Separation

Dawson, William A.; Wittman, David; Jee, M. James; Gee, Perry M.; Hughes, John P.; Tyson, J. A.; Schmidt, Samuel J.; Thorman, Paul; Bradač, Maruša; Miyazaki, Satoshi; Lemaux, B. C.; Utsumi, Yousuke; Margoniner, V. E.

doi:10.1088/2041-8205/747/2/l42

Cited by 134 publications

(156 citation statements)

References 51 publications

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“…Cluster mergers have been used by many studies to constrain SIDM (see e.g., Randall et al 2008;Dawson et al 2012;Kahlhoefer et al 2014;Massey et al 2015;Schaller et al 2015;Kim et al 2017;Robertson et al 2017), with typical limits of m 1 cm g 2 1  s -on the self-interaction cross-section. However, recent work by Kim et al (2017) showed that constraints based on the displacement of the stellar and DM centroids are overly stringent, weakening previous constraints.…”

Section: Properties Of Viable Sidm Modelsmentioning

confidence: 99%

A Testable Conspiracy: Simulating Baryonic Effects on Self-interacting Dark Matter Halos

Elbert

Bullock

Kaplinghat

et al. 2018

ApJ

109

116

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We investigate the response of self-interacting dark matter (SIDM) halos to the growth of galaxy potentials using idealized simulations, with each run in tandem with collisionless cold dark matter (CDM). We find that if the stellar potential strongly dominates in the central parts of a galaxy, then SIDM halos can be as dense as CDM halos on observable scales. For extreme cases, core collapse can occur, leading to SIDM halos that are denser and cuspier than their CDM counterparts. If the stellar potential is not dominant, then SIDM halos retain isothermal cores with densities far below CDM predictions. When a disk is present, the inner SIDM halo becomes more flattened in the disk plane than the CDM halo.  s -is disfavored for DM collision velocities above about 1500 km s −1 . More generally, the interaction between baryonic potentials and SIDM densities offers new directions for constraining SIDM cross-sections in galaxies where baryons are dynamically important.

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Section: Properties Of Viable Sidm Modelsmentioning

confidence: 99%

A Testable Conspiracy: Simulating Baryonic Effects on Self-interacting Dark Matter Halos

Elbert

Bullock

Kaplinghat

et al. 2018

ApJ

109

116

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“…If the merger is not in the plane of the sky, mergers can be detected in optical observations based on multiple peaks in the radial velocity distribution and in the spatial galaxy distribution. Furthermore, comparison of X-ray and optical/ lensing data also reveals signatures of merging events, most notably as offsets between the dark matter (DM) and the gas components of the colliding clusters (e.g., Markevitch et al 2004;Clowe et al 2006;Randall et al 2008b;Merten et al 2011;Dawson et al 2012).…”

Section: Introductionmentioning

confidence: 99%

FRONTIER FIELDS CLUSTERS:CHANDRAAND JVLA VIEW OF THE PRE-MERGING CLUSTER MACS J0416.1-2403

Ogrean

Weeren

Jones

et al. 2015

ApJ

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Merging galaxy clusters leave long-lasting signatures on the baryonic and non-baryonic cluster constituents, including shock fronts, cold fronts, X-ray substructure, radio halos, and offsets between the dark matter (DM) and the gas components. Using observations from Chandra, the Jansky Very Large Array, the Giant Metrewave Radio Telescope, and the Hubble Space Telescope, we present a multiwavelength analysis of the merging Frontier Fields cluster MACS J0416.1-2403 (z = 0.396), which consists of NE and SW subclusters whose cores are separated on the sky by ∼250 kpc. We find that the NE subcluster has a compact core and hosts an X-ray cavity, yet it is not a cool core. Approximately 450 kpc south-southwest of the SW subcluster, we detect a density discontinuity that corresponds to a compression factor of ∼1.5. The discontinuity was most likely caused by the interaction of the SW subcluster with a less massive structure detected in the lensing maps SW of the subclusterʼs center. For both the NE and the SW subclusters, the DM and the gas components are well-aligned, suggesting that MACS J0416.1-2403 is a pre-merging system. The cluster also hosts a radio halo, which is unusual for a pre-merging system. The halo has a 1.4 GHz power of (1.3 ± 0.3) × 10 24 W Hz −1 , which is somewhat lower than expected based on the X-ray luminosity of the cluster if the spectrum of the halo is not ultra-steep. We suggest that we are either witnessing the birth of a radio halo, or have discovered a rare ultra-steep spectrum halo.

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“…Musket Ball is a dissociative merger during which the primary baryonic and non-baryonic components have become detached, so we largely attribute the gas offset to the cluster merger. The WL-galaxy density offset of 145 h −1 70 kpc (Table 2) can also be largely attributed to the merger (Dawson et al 2012). An irregular North cluster is consistent with morphology and spectral results indicating several late-type galaxy mergers and enhanced star formation activity (Cohen et al 2014(Cohen et al , 2015.…”

Section: Resultsmentioning

confidence: 90%

“…It was first identified by its Weak Lensing (WL) shear signal, using the Deep Lens Survey (DLS) (Wittman et al 2002). The system was confirmed to be at z=0.53 using redshifts attained with the Low Resolution Imaging Spectrometer (LRIS) on the Keck I (2007 January 16), and two clusters were identified to be at the same redshift using the DEep Imaging Multi-Object Spectrograph (DEIMOS; Faber et al 2003) on Keck II (2011 March 2-3) (Dawson et al 2012).…”

Section: Targetmentioning

confidence: 99%

“…The systemic redshift of each cluster centroid is given as input for the TSC simulation (Dawson et al 2012;Dawson 2013b), and was calculated using the biweight statistic from Beers et al (1990) to downweight tails of the distribution, applied to 100,000 bootstrap samples of each cluster's spectroscopic redshifts. Results are found in Table 2 and seen as dotted lines in the lower redshift histogram of Fig.…”

Section: Isodensity Contoursmentioning

confidence: 99%

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Star Formation in the Cluster Merger DLSCL J0916.2+2953

Mansheim

Lemaux

Dawson

et al. 2017

ApJ

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We investigate star formation in DLSCL J0916.2+2953, a dissociative merger of two clusters at z=0.53 that has progressed 1.1 +1.3 −0.4 Gyr since first pass-through. We attempt to reveal the effects a collision may have had on the evolution of the cluster galaxies by tracing their star formation history. We probe current and recent activity to identify a possible star formation event at the time of the merger using EW(Hδ), EW([OII]), and D n (4000) measured from the composite spectra of 64 cluster and 153 coeval field galaxies. We supplement Keck DEIMOS spectra with DLS and HST imaging to determine the color, stellar mass, and morphology of each galaxy and conduct a comprehensive study of the populations in this complex structure. Spectral results indicate the average cluster and cluster red sequence galaxies experienced no enhanced star formation relative to the surrounding field during the merger, ruling out a predominantly merger-quenched population. We find that the average blue galaxy in the North cluster is currently active and in the South cluster is currently post-starburst having undergone a recent star formation event. While the North activity could be latent or longterm merger effects, a young blue stellar population and irregular geometry suggest the cluster was still forming prior the collision. While the South activity coincides with the time of the merger, the blue early-type population could be a result of secular cluster processes. The evidence suggests that the dearth or surfeit of activity is indiscernible from normal cluster galaxy evolution.

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Discovery of a Dissociative Galaxy Cluster Merger With Large Physical Separation

Cited by 134 publications

References 51 publications

A Testable Conspiracy: Simulating Baryonic Effects on Self-interacting Dark Matter Halos

A Testable Conspiracy: Simulating Baryonic Effects on Self-interacting Dark Matter Halos

FRONTIER FIELDS CLUSTERS:CHANDRAAND JVLA VIEW OF THE PRE-MERGING CLUSTER MACS J0416.1-2403

Star Formation in the Cluster Merger DLSCL J0916.2+2953

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