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Title: Data and 2D scaling relations for galaxies in Abell 1689: a hint of size evolution at z~0.2
Authors: R. C. W. Houghton, Roger L. Davies, E. Dalla Bonta, R. Masters

We present imaging and spectroscopy of Abell 1689 (z=0.183) from GEMINI/GMOS-N and HST/ACS. We measure integrated photometry from the GMOS g' and r' images (for 531 galaxies) and surface photometry from the HST F625W image (for 43 galaxies) as well as velocities and velocity dispersions from the GMOS spectra (for 71 galaxies). We construct the Kormendy relation (KR), Faber-Jackson relation (FJR) and colour-magnitude relation (CMR) for early-type galaxies in Abell 1689 using this data and compare them to those of the Coma cluster. We measure the intrinsic scatter of the CMR in Abell 1689 to be 0.054 ±0.004 mag which places degenerate constraints on the ratio of the assembly timescale to the time available (beta) and the age of the population. Making the assumption that galaxies in Abell 1689 will evolve into those of Coma over an interval of 2.26 Gyr breaks this degeneracy and limits beta to be > 0.6 and the age of the red sequence to be > 5.5 Gyr (formed at z > 0.55). Without corrections for size evolution but accounting for magnitude cuts and selection effects, the KR & FJR are inconsistent and disagree at the 2 sigma level regarding the amount of luminosity evolution in the last 2.26 Gyr. However, after correcting for size evolution the KR & FJR show similar changes in luminosity (0.22 ±0.11 mag) that are consistent with the passive evolution of the stellar populations from a single burst of star formation 10.2 ±3.3 Gyr ago (z = 1.8+inf-0.9). Thus the changes in the KR, FJR & CMR of Abell 1689 relative to Coma all agree and suggest old galaxy populations with little or no synchronisation in the star formation histories. Furthermore, the weak evidence for size evolution in the cluster environment in the last 2.26 Gyr places interesting constraints on the possible mechanisms at work, favouring harassment or secular processes over merger scenarios.

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Abell 1689
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New Dark Matter Map Solving Galactic Puzzle?

One of the brilliant things about astrophysics is being able to take pictures of invisible stuff.
Infrared telescopes, for example, allow astronomers to see "dark" nebulas, clouds of dust and gas that weakly reflect light from nearby stars, glowing mostly in thermal emissions.
Similarly, high-energy x-rays and gamma rays let scientists "see" black holes, objects that by definition are so dense not even light can escape their gravitational pull.

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Detailed Dark Matter Map Yields Clues to Galaxy Cluster Growth

Astronomers using NASA's Hubble Space Telescope received a boost from a cosmic magnifying glass to construct one of the sharpest maps of dark matter in the universe. They used Hubble's Advanced Camera for Surveys to chart the invisible matter in the massive galaxy cluster Abell 1689, located 2.2 billion light-years away. The cluster contains about 1,000 galaxies and trillions of stars. Dark matter is an invisible form of matter that accounts for most of the universe's mass. Hubble cannot see the dark matter directly. Astronomers inferred its location by analysing the effect of gravitational lensing, where light from galaxies behind Abell 1689 is distorted by intervening matter within the cluster.
Researchers used the observed positions of 135 lensed images of 42 background galaxies to calculate the location and amount of dark matter in the cluster. They superimposed a map of these inferred dark matter concentrations, tinted blue, on a Hubble image of the cluster. The new dark matter observations may yield new insights into the role of dark energy in the universe's early formative years.

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Fate of Universe revealed by galactic lens

A "galactic lens" has revealed that the Universe will probably expand forever.
Astronomers used the way that light from distant stars was distorted by a huge galactic cluster known as Abell 1689 to work out the amount of dark energy in the cosmos.
Dark energy is a mysterious force that speeds up the expansion of the Universe.

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Title: The galaxy alignment effect in Abell 1689: evolution, radial and luminosity dependence
Authors: Li-Wei Hung (Ohio State University), Eduardo Banados (Pontificia Universidad Catolica de Chile), Roberto De Propris (CTIO), Michael West (ESO, Santiago)

We measure alignments on scales of 1 Mpc h^{-1}_{71} for galaxies in Abell 1689 (z=0.18) from an existing Hubble Space Telescope mosaic. We find evidence of galaxy alignment in the inner 500 h^{-1}_{71} kpc. The alignment appears to be stronger towards the centre and is mostly present among the fainter galaxies, while bright galaxies are unaligned. This is consistent with a model where alignments originate from tidal locking.

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Abell 1689
Credit: X-ray: NASA/CXC/MIT/E.-H Peng et al; Optical: NASA/STScI
JPEG (1.1 MB) Tiff (46.7 MB) PS (7.5 MB)

Abell 1689, shown in this composite image, is a massive cluster of galaxies located about 2.3 billion light years away that shows signs of merging activity. Hundred-million-degree gas detected by NASA's Chandra X-ray Observatory is shown as purple in this image, while galaxies from optical data from the Hubble Space Telescope are colored yellow. The X-ray emission has a smooth appearance, unlike other merging systems such as the Bullet Cluster or MACS J0025.4-1222. The temperature pattern across Abell 1689 is more complicated, however, possibly requiring multiple structures with different temperatures.

Position (2000):     RA 13h 11m 34.20s | Dec -01º 21' 56.00"

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Title: The sizes of galaxy halos in galaxy cluster Abell 1689
Authors: A. Halkola, S. Seitz, M. Pannella

The multiple images observed in galaxy cluster Abell 1689 provide strong constraints not only on the mass distribution of the cluster but also on the ensemble properties of the cluster galaxies. Using parametric strong lensing models for the cluster, and by assuming well motivated scaling laws between the truncation radius s and the velocity dispersion sigma of a cluster galaxy we are able to derive sizes of the dark matter halos of cluster galaxies.
For the scaling law expected for galaxies in the cluster environment (s propto sigma), we obtain s = 64^+15_-14 (sigma / 220 km/s) kpc. For the scaling law used for galaxies in the field with s propto sigma^2 we find s = 66^+18_-16 (sigma / 220 km/s)² kpc. Compared to halos of field galaxies, the cluster galaxy halos in Abell 1689 are strongly truncated. test detector components at 3500 m depth and will allow also a continuous monitoring of the site.

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