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TOPIC: MACSJ0717.5+3745
Blobrana


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Title: CLASH: Complete Lensing Analysis of the Largest Cosmic Lens MACS J0717.5+3745 and Surrounding Structures
Authors: Elinor Medezinski (JHU), Keiichi Umetsu, Mario Nonino, Julian Merten, Adi Zitrin, Tom Broadhurst, Megan Donahue, Jack Sayers, Jean-Claude Waizmann, Anton Koekemoer, Dan Coe, Alberto Molino, Peter Melchior, Tony Mroczkowski, Nicole Czakon, Marc Postman, Massimo Meneghetti, Doron Lemze, Holland Ford, Claudio Grillo, Daniel Kelson, Larry Bradley, John Moustakas, Matthias Bartelmann, Narciso Benítez, Andrea Biviano, Rychard Bouwens, Sunil Golwala, Genevieve Graves, Leopoldo Infante, Yolanda Jiménez-Teja, Stephanie Jouvel, Ofer Lahav, Leonidas Moustakas, Sara Ogaz, Piero Rosati, Stella Seitz, Wei Zheng

The galaxy cluster MACS J0717.5+3745 (z=0.55) is the largest known cosmic lens, with complex internal structures seen in deep X-ray, Sunyaev-Zel'dovich effect and dynamical observations. We perform a combined weak and strong lensing analysis with wide-field BVRi'z' Subaru/Suprime-Cam observations and 16-band Hubble Space Telescope observations taken as part of the Cluster Lensing And Supernova survey with Hubble (CLASH). We find consistent weak distortion and magnification measurements of background galaxies, and combine these signals to construct an optimally estimated radial mass profile of the cluster and its surrounding large-scale structure out to 5 Mpc/h. We find consistency between strong-lensing and weak-lensing in the region where these independent data overlap, <500 kpc/h. The two-dimensional weak-lensing map reveals a clear filamentary structure traced by distinct mass halos. We model the lensing shear field with 9 halos, including the main cluster, corresponding to mass peaks detected above 2.5\sigma_\kappa. The total mass of the cluster as determined by the different methods is M_{vir}=(2.8±0.4) x 10^15 solar masses. Although this is the most massive cluster known at z>0.5, in terms of extreme value statistics we conclude that the mass of MACS J0717.5+3745 by itself is not in serious tension with LambdaCDM, representing only a ~2{\sigma} departure above the maximum simulated halo mass at this redshift.

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Dark Matter Filament Studied in 3D for the First Time

Astronomers using the NASA/ESA Hubble Space Telescope have studied a giant filament of dark matter in 3D for the first time. Extending 60 million light-years from one of the most massive galaxy clusters known, the filament is part of the cosmic web that constitutes the large-scale structure of the Universe, and is a leftover of the very first moments after the Big Bang. If the high mass measured for the filament is representative of the rest of the Universe, then these structures may contain more than half of all the mass in the Universe.
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Blobrana


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MACS J0717.5+3745
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Title: The strongest gravitational lenses: II. Is the large Einstein radius of MACS J0717.5+3745 in conflict with LCDM?
Authors: Jean-Claude Waizmann, Matthias Redlich, Matthias Bartelmann

Can the standard cosmological model be questioned on the basis of a single observed extreme galaxy cluster? Usually, the word extreme refers directly to cluster mass, which is not a direct observable and thus subject to substantial uncertainty. Hence, it is desirable to extend studies of extreme clusters to direct observables such as the Einstein radius (ER). We aim to evaluate the occurrence probability of the large observed ER of MACS J0717.5 within the standard LCDM cosmology. In particular, we want to model the distribution function of the single largest ER in a given cosmological volume and to study which underlying assumptions and effects have the strongest impact on the results. We obtain this distribution by a Monte Carlo approach, based on the semi-analytic modelling of the halo population on the past lightcone. After sampling the distribution, we fit the results with the general extreme value (GEV) distribution which we use for the subsequent analysis. We find that the distribution of the maximum ER is particularly sensitive to the precise choice of the halo mass function, lens triaxiality, the inner slope of the halo density profile and the mass-concentration relation. Using the distributions so obtained, we study the occurrence probability of the large ER of MACS J0717.5, finding that this system is not in tension with LCDM. We also find that the GEV distribution can be used to fit very accurately the sampled distributions and that all of them can be described by a Frechet distribution. With a multitude of effects that strongly influence the distribution of the single largest ER, it is more than doubtful that the standard LCDM cosmology can be ruled out on the basis of a single observation. If, despite the large uncertainties in the underlying assumptions, one wanted to do so, a much larger ER (> 100 arcsec) than that of MACS J0717.5 would have to be observed.

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Blobrana


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Title: Diffuse radio emission in the merging cluster MACS J0717.5+3745: the discovery of the most powerful radio halo
Authors: R.J. van Weeren, H.J.A. Rottgering, M. Bruggen, A. Cohen

Hierarchical models of structure formation predict that galaxy clusters grow via mergers of smaller clusters and galaxy groups, as well as through continuous accretion of gas. MACS J0717.5+3745 is an X-ray luminous and complex merging cluster, located at a redshift of 0.55. Here we present Giant Metrewave Radio Telescope (GMRT) radio observations at 610 MHz of this cluster. The main aim of the observations is to search for diffuse radio emission within the galaxy cluster MACS J0717.5+3745 related to the ongoing merger. These GMRT observations are complemented by Very Large Array (VLA) archival observations at 1.4, 4.9 and 8.5 GHz. We have discovered a radio halo in the cluster MACS J0717.5+3745 with a size of about 1.2 Mpc. The radio power P_1.4 GHz is 5 x 10^25 W/Hz, which makes it the most powerful radio halo known till date. A 700 kpc radio structure, which we classify as a radio relic, is located in between the merging substructures of the system. The location of this relic roughly coincides with regions of the intra-cluster medium (ICM) that have a significant enhancement in temperature as shown by Chandra. The major axis of the relic is also roughly perpendicular to the merger axis. This shows that the relic might be the result of a merger-related shock wave, where particles are accelerated via the diffuse shock acceleration (DSA) mechanism. Alternatively, the relic might trace an accretion shock of a large-scale galaxy filament to the south-west. The global spectral index of radio emission within the cluster is found to be -1.24 ±0.05 between 4.9 GHz and 610 MHz. We derive a value of 1.1 microGauss for the equipartition magnetic field strength at the location of the radio halo.

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Chandra X-ray & HST Optical Images of MACSJ0717.5+3745
This image contains one of the most complex galaxy clusters known, which is located about 5.4 billion light years from Earth. In this system known as MacsJ0717 for short, 4 separate galaxy clusters have collided. This is the first time such a complex crash of galaxy clusters has been documented. In this composite image, data from the Chandra X-ray Observatory reveal the cluster's hot gas, while an optical image from the Hubble Space Telescope shows the individual galaxies in the system. The gas in this image is colour-coded to show temperature, just like a weather map for Earth. In this case however, the temperatures range from millions to tens of millions of degrees, where the coolest gas here is coloured red, the hottest gas is blue, and the temperatures in between are purple.

MACSJ0717.5+3745
MACSJ0717.5+3745
MACSJ0717.5+3745



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University of Hawaii-Manoa astronomers have documented a collision of four galaxy clusters 5.4 billion light years from Earth.
Using data from space and ground-based telescopes, graduate student Cheng-Jiun Ma and astronomer Harald Ebeling of the Institute for Astronomy determined the three-dimensional geometry and motion of galaxies in the MACSJO717 cluster system.

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Blobrana


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MACS J0717.5+3745
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An interstellar pileup involving four galaxy clusters has become the most crowded cluster collision ever detected.
Astronomers spotted the galaxy clusters involved in a triple merger, the first time that such a phenomenon has been recorded. NASA's Chandra X-Ray Observatory and Hubble Space Telescope joined the Keck Observatory in Hawaii to safely observe the mess from 5.4 billion light years away.

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Blobrana


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The most crowded collision of galaxy clusters has been identified by combining information from three different telescopes. This result gives scientists a chance to learn what happens when some of the largest objects in the universe go at each other in a cosmic free-for-all. Using data from NASA's Chandra X-ray Observatory, Hubble Space Telescope, and the Keck Observatory in Hawaii, astronomers were able to determine the three-dimensional geometry and motion in the system MACS J0717.5+3745 (or MACS J0717, for short), located about 5.4 billion light-years from Earth.

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Blobrana


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Posts: 131433
Date:
MACSJ0717.5+3745
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The most crowded collision of galaxy clusters has been identified by combining information from three different telescopes. This result gives scientists a chance to learn what happens when some of the largest objects in the Universe go at each other in a cosmic free-for-all.
Using data from NASA's Chandra X-ray Observatory, Hubble Space Telescope and the Keck Observatory on Mauna Kea, Hawaii, astronomers were able to determine the three-dimensional geometry and motion in the system MACSJ0717.5+3745 (or MACSJ0717 for short) located about 5.4 billion light years from Earth.
The researchers found that four separate galaxy clusters are involved in a triple merger, the first time such a phenomenon has been documented.

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Position(2000): RA 07h 17m 31.00s, Dec +37° 45' 39.60

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