73 research outputs found
The Cluster Lensing and Supernova Survey with Hubble (CLASH): Strong Lensing Analysis of Abell 383 from 16-Band HST WFC3/ACS Imaging
We examine the inner mass distribution of the relaxed galaxy cluster Abell
383 in deep 16-band HST/ACS+WFC3 imaging taken as part of the CLASH multi-cycle
treasury program. Our program is designed to study the dark matter distribution
in 25 massive clusters, and balances depth with a wide wavelength coverage to
better identify lensed systems and generate precise photometric redshifts. This
information together with the predictive strength of our strong-lensing
analysis method identifies 13 new multiply-lensed images and candidates, so
that a total of 27 multiple-images of 9 systems are used to tightly constrain
the inner mass profile, (r<160 kpc).
We find consistency with the standard distance-redshift relation for the full
range spanned by the lensed images, 1.01<z<6.03, with the higher redshift
sources deflected through larger angles as expected. The inner mass profile
derived here is consistent with the results of our independent weak-lensing
analysis of wide-field Subaru images, with good agreement in the region of
overlap. The overall mass profile is well fitted by an NFW profile with
M_{vir}=(5.37^{+0.70}_{-0.63}\pm 0.26) x 10^{14}M_{\odot}/h and a relatively
high concentration, c_{vir}=8.77^{+0.44}_{-0.42}\pm 0.23, which lies above the
standard c-M relation similar to other well-studied clusters. The critical
radius of Abell 383 is modest by the standards of other lensing clusters,
r_{E}\simeq16\pm2\arcsec (for z_s=2.55), so the relatively large number of
lensed images uncovered here with precise photometric redshifts validates our
imaging strategy for the CLASH survey. In total we aim to provide similarly
high-quality lensing data for 25 clusters, 20 of which are X-ray selected
relaxed clusters, enabling a precise determination of the representative mass
profile free from lensing bias. (ABRIDGED)Comment: 15 pages, 14 figures, 2 tabels; V3 matches the submitted version
later published in Ap
RELICS: The Reionization Lensing Cluster Survey and the Brightest High-z Galaxies
Massive foreground galaxy clusters magnify and distort the light of objects behind them, permitting a view into both the extremely distant and intrinsically faint galaxy populations. We present here the z ~ 6-8 candidate high-redshift galaxies from the Reionization Lensing Cluster Survey (RELICS), a Hubble and Spitzer Space Telescope survey of 41 massive galaxy clusters spanning an area of â200 arcminÂČ. These clusters were selected to be excellent lenses, and we find similar high-redshift sample sizes and magnitude distributions as the Cluster Lensing And Supernova survey with Hubble (CLASH). We discover 257, 57, and eight candidate galaxies at z ~ 6, 7, and 8 respectively, (322 in total). The observed (lensed) magnitudes of the z ~ 6 candidates are as bright as AB mag ~23, making them among the brightest known at these redshifts, comparable with discoveries from much wider, blank-field surveys. RELICS demonstrates the efficiency of using strong gravitational lenses to produce high-redshift samples in the epoch of reionization. These brightly observed galaxies are excellent targets for follow-up study with current and future observatories, including the James Webb Space Telescope
Type Ia Supernova Distances at z > 1.5 from the Hubble Space Telescope Multi-Cycle Treasury Programs: The Early Expansion Rate
We present an analysis of 15 Type Ia supernovae (SNe Ia) at redshift z > 1 (9
at 1.5 < z < 2.3) recently discovered in the CANDELS and CLASH Multi-Cycle
Treasury programs using WFC3 on the Hubble Space Telescope. We combine these
SNe Ia with a new compilation of 1050 SNe Ia, jointly calibrated and corrected
for simulated survey biases to produce accurate distance measurements. We
present unbiased constraints on the expansion rate at six redshifts in the
range 0.07 < z < 1.5 based only on this combined SN Ia sample. The added
leverage of our new sample at z > 1.5 leads to a factor of ~3 improvement in
the determination of the expansion rate at z = 1.5, reducing its uncertainty to
~20%, a measurement of H(z=1.5)/H0=2.67 (+0.83,-0.52). We then demonstrate that
these six measurements alone provide a nearly identical characterization of
dark energy as the full SN sample, making them an efficient compression of the
SN Ia data. The new sample of SNe Ia at z > 1 usefully distinguishes between
alternative cosmological models and unmodeled evolution of the SN Ia distance
indicators, placing empirical limits on the latter. Finally, employing a
realistic simulation of a potential WFIRST SN survey observing strategy, we
forecast optimistic future constraints on the expansion rate from SNe Ia.Comment: 14 pages, 5 figures, 7 tables; submitted to Ap
CLASH: New Multiple-Images Constraining the Inner Mass Profile of MACS J1206.2-0847
We present a strong-lensing analysis of the galaxy cluster MACS J1206.2-0847
(=0.44) using UV, Optical, and IR, HST/ACS/WFC3 data taken as part of the
CLASH multi-cycle treasury program, with VLT/VIMOS spectroscopy for some of the
multiply-lensed arcs. The CLASH observations, combined with our mass-model,
allow us to identify 47 new multiply-lensed images of 12 distant sources. These
images, along with the previously known arc, span the redshift range 1\la
z\la5.5, and thus enable us to derive a detailed mass distribution and to
accurately constrain, for the first time, the inner mass-profile of this
cluster. We find an inner profile slope of (in the range [1\arcsec, 53\arcsec], or 5\la r \la300 kpc), as
commonly found for relaxed and well-concentrated clusters. Using the many
systems uncovered here we derive credible critical curves and Einstein radii
for different source redshifts. For a source at , the critical
curve encloses a large area with an effective Einstein radius of
\theta_{E}=28\pm3\arcsec, and a projected mass of . From the current understanding of structure formation in
concordance cosmology, these values are relatively high for clusters at
, so that detailed studies of the inner mass distribution of clusters
such as MACS J1206.2-0847 can provide stringent tests of the CDM
paradigm.Comment: 7 pages, 1 table, 4 figures; submitted to ApJ Letters; V3: minor
correction
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