41 research outputs found
Not In Our Backyard: Spectroscopic Support for the CLASH z=11 Candidate MACS0647-JD
We report on our first set of spectroscopic Hubble Space Telescope
observations of the z~11 candidate galaxy strongly lensed by the
MACSJ0647.7+7015 galaxy cluster. The three lensed images are faint and we show
that these early slitless grism observations are of sufficient depth to
investigate whether this high-redshift candidate, identified by its strong
photometric break at ~1.5 micron, could possibly be an emission line galaxy at
a much lower redshift. While such an interloper would imply the existence of a
rather peculiar object, we show here that such strong emission lines would
clearly have been detected. Comparing realistic, two-dimensional simulations to
these new observations we would expect the necessary emission lines to be
detected at >5 sigma while we see no evidence for such lines in the dispersed
data of any of the three lensed images. We therefore exclude that this object
could be a low redshift emission line interloper, which significantly increases
the likelihood of this candidate being a bona fide z~11 galaxy.Comment: 14 Pages. 6 Figures. 2nd revised version. Accepted. To appear in ApJ.
Please contact [email protected] for comments on this pape
CLASH: Extreme Emission Line Galaxies and Their Implication on Selection of High-Redshift Galaxies
We utilize the CLASH (Cluster Lensing And Supernova survey with Hubble)
observations of 25 clusters to search for extreme emission-line galaxies
(EELGs). The selections are carried out in two central bands: F105W (Y105) and
F125W (J125), as the flux of the central bands could be enhanced by the
presence of [O III] 4959, 5007 at redshift of about 0.93-1.14 and 1.57-1.79,
respectively. The multi-band observations help to constrain the equivalent
widths of emission lines. Thanks to cluster lensing, we are able to identify 52
candidates down to an intrinsic limiting magnitude of 28.5 and to a rest-frame
[O III] 4959,5007 equivalent width of about 3737 angstrom. Our samples include
a number of EELGs at lower luminosities that are missed in other surveys, and
the extremely high equivalent width can be only found in such faint galaxies.
These EELGs can mimic the dropout feature similar to that of high redshift
galaxies and contaminate the color-color selection of high redshift galaxies
when the S/N ratio is limited or the band coverage is incomplete. We predict
that the fraction of EELGs in the future high redshift galaxy selections cannot
be neglected.Comment: 17 pages, 9 figures, 2 tables, Accepted for publication in AP
The Contribution of Halos with Different Mass Ratios to the Overall Growth of Cluster-Sized Halos
We provide a new observational test for a key prediction of the \Lambda CDM
cosmological model: the contributions of mergers with different
halo-to-main-cluster mass ratios to cluster-sized halo growth. We perform this
test by dynamically analyzing seven galaxy clusters, spanning the redshift
range and caustic mass range M, with an average of 293 spectroscopically-confirmed
bound galaxies to each cluster. The large radial coverage (a few virial radii),
which covers the whole infall region, with a high number of spectroscopically
identified galaxies enables this new study. For each cluster, we identify bound
galaxies. Out of these galaxies, we identify infalling and accreted halos and
estimate their masses and their dynamical states. Using the estimated masses,
we derive the contribution of different mass ratios to cluster-sized halo
growth. For mass ratios between ~0.2 and ~0.7, we find a ~1 agreement
with \Lambda CDM expectations based on the Millennium simulations I and II. At
low mass ratios, , our derived contribution is underestimated
since the detection efficiency decreases at low masses,
M. At large mass ratios, , we do not
detect halos probably because our sample, which was chosen to be quite X-ray
relaxed, is biased against large mass ratios. Therefore, at large mass ratios,
the derived contribution is also underestimated.Comment: 25 pages, 16 figures, 6 tables, 2 machine readable tables, accepted
for publication in ApJ, updated acknowledgements and data table format
modifications mad
CLASH: Precise New Constraints on the Mass Profile of Abell 2261
We precisely constrain the inner mass profile of Abell 2261 (z=0.225) for the
first time and determine this cluster is not "over-concentrated" as found
previously, implying a formation time in agreement with {\Lambda}CDM
expectations. These results are based on strong lensing analyses of new 16-band
HST imaging obtained as part of the Cluster Lensing and Supernova survey with
Hubble (CLASH). Combining this with revised weak lensing analyses of Subaru
wide field imaging with 5-band Subaru + KPNO photometry, we place tight new
constraints on the halo virial mass M_vir = 2.2\pm0.2\times10^15 M\odot/h70
(within r \approx 3 Mpc/h70) and concentration c = 6.2 \pm 0.3 when assuming a
spherical halo. This agrees broadly with average c(M,z) predictions from recent
{\Lambda}CDM simulations which span 5 <~ 8. Our most significant
systematic uncertainty is halo elongation along the line of sight. To estimate
this, we also derive a mass profile based on archival Chandra X-ray
observations and find it to be ~35% lower than our lensing-derived profile at
r2500 ~ 600 kpc. Agreement can be achieved by a halo elongated with a ~2:1 axis
ratio along our line of sight. For this elongated halo model, we find M_vir =
1.7\pm0.2\times10^15 M\odot/h70 and c_vir = 4.6\pm0.2, placing rough lower
limits on these values. The need for halo elongation can be partially obviated
by non-thermal pressure support and, perhaps entirely, by systematic errors in
the X-ray mass measurements. We estimate the effect of background structures
based on MMT/Hectospec spectroscopic redshifts and find these tend to lower
Mvir further by ~7% and increase cvir by ~5%.Comment: Submitted to the Astrophysical Journal. 19 pages, 14 figure
Three Gravitationally Lensed Supernovae Behind CLASH Galaxy Clusters
We report observations of three gravitationally lensed supernovae (SNe) in
the Cluster Lensing And Supernova survey with Hubble (CLASH) Multi-Cycle
Treasury program. These objects, SN CLO12Car (z = 1.28), SN CLN12Did (z =
0.85), and SN CLA11Tib (z = 1.14), are located behind three different clusters,
MACSJ1720.2+3536 (z = 0.391), RXJ1532.9+3021 (z = 0.345), and Abell 383 (z =
0.187), respectively. Each SN was detected in Hubble Space Telescope (HST)
optical and infrared images. Based on photometric classification, we find that
SNe CLO12Car and CLN12Did are likely to be Type Ia supernovae (SNe Ia), while
the classification of SN CLA11Tib is inconclusive. Using multi-color
light-curve fits to determine a standardized SN Ia luminosity distance, we
infer that SN CLO12Car was approximately 1.0 +/- 0.2 mag brighter than field
SNe Ia at a similar redshift and ascribe this to gravitational lens
magnification. Similarly, SN CLN12Did is approximately 0.2 +/- 0.2 mag brighter
than field SNe Ia. We derive independent estimates of the predicted
magnification from CLASH strong+weak lensing maps of the clusters: 0.83 +/-
0.16 mag for SN CLO12Car, 0.28 +/- 0.08 mag for SN CLN12Did, and 0.43 +/- 0.11
mag for SN CLA11Tib. The two SNe Ia provide a new test of the cluster lens
model predictions: we find that the magnifications based on the SN Ia
brightness and those predicted by the lens maps are consistent. Our results
herald the promise of future observations of samples of cluster-lensed SNe Ia
(from the ground or space) to help illuminate the dark-matter distribution in
clusters of galaxies, through the direct determination of absolute
magnifications.Comment: ApJ in pres
CLASH-X: A Comparison of Lensing and X-ray Techniques for Measuring the Mass Profiles of Galaxy Clusters
We present profiles of temperature (Tx), gas mass, and hydrostatic mass
estimated from new and archival X-ray observations of CLASH clusters. We
compare measurements derived from XMM and Chandra observations with one another
and compare both to gravitational lensing mass profiles derived with CLASH HST
and ground-based lensing data. Radial profiles of Chandra and XMM electron
density and enclosed gas mass are nearly identical, indicating that differences
in hydrostatic masses inferred from X-ray observations arise from differences
in Tx measurements. Encouragingly, cluster Txs are consistent with one another
at ~100-200 kpc radii but XMM Tx systematically decline relative to Chandra Tx
at larger radii. The angular dependence of the discrepancy suggests additional
investigation on systematics such as the XMM point spread function correction,
vignetting and off-axis responses. We present the CLASH-X mass-profile
comparisons in the form of cosmology-independent and redshift-independent
circular-velocity profiles. Ratios of Chandra HSE mass profiles to CLASH
lensing profiles show no obvious radial dependence in the 0.3-0.8 Mpc range.
However, the mean mass biases inferred from the WL and SaWLens data are
different. e.g., the weighted-mean value at 0.5 Mpc is = 0.12 for the WL
comparison and = -0.11 for the SaWLens comparison. The ratios of XMM HSE
mass profiles to CLASH lensing profiles show a pronounced radial dependence in
the 0.3-1.0 Mpc range, with a weighted mean mass bias of value rising to
~0.3 at ~1 Mpc for the WL comparison and of 0.25 for SaWLens comparison.
The enclosed gas mass profiles from both Chandra and XMM rise to a value 1/8
times the total-mass profiles inferred from lensing at 0.5 Mpc and remain
constant outside of that radius, suggesting that [8xMgas] profiles may be an
excellent proxy for total-mass profiles at >0.5 Mpc in massive galaxy clusters.Comment: Accepted to ApJ; 24 pages; scheduled to appear in the Oct 10, 2014
issue. This version corrects the typographical error in the superscripts for
Equation (2) to include the square of (r/r_core). The correct version of this
equation was used in the analysi
CLASH: Mass Distribution in and around MACS J1206.2-0847 from a Full Cluster Lensing Analysis
We derive an accurate mass distribution of the galaxy cluster MACS
J1206.2-0847 (z=0.439) from a combined weak-lensing distortion, magnification,
and strong-lensing analysis of wide-field Subaru BVRIz' imaging and our recent
16-band Hubble Space Telescope observations taken as part of the Cluster
Lensing And Supernova survey with Hubble (CLASH) program. We find good
agreement in the regions of overlap between several weak and strong lensing
mass reconstructions using a wide variety of modeling methods, ensuring
consistency. The Subaru data reveal the presence of a surrounding large scale
structure with the major axis running approximately north-west south-east
(NW-SE), aligned with the cluster and its brightest galaxy shapes, showing
elongation with a \sim 2:1 axis ratio in the plane of the sky. Our full-lensing
mass profile exhibits a shallow profile slope dln\Sigma/dlnR\sim -1 at cluster
outskirts (R>1Mpc/h), whereas the mass distribution excluding the NW-SE excess
regions steepens further out, well described by the Navarro-Frenk-White form.
Assuming a spherical halo, we obtain a virial mass M_{vir}=(1.1\pm 0.2\pm
0.1)\times 10^{15} M_{sun}/h and a halo concentration c_{vir} = 6.9\pm 1.0\pm
1.2 (\sim 5.7 when the central 50kpc/h is excluded), which falls in the range
4 <7 of average c(M,z) predictions for relaxed clusters from recent Lambda
cold dark matter simulations. Our full lensing results are found to be in
agreement with X-ray mass measurements where the data overlap, and when
combined with Chandra gas mass measurements, yield a cumulative gas mass
fraction of 13.7^{+4.5}_{-3.0}% at 0.7Mpc/h (\approx 1.7r_{2500}), a typical
value observed for high mass clusters.Comment: Accepted by ApJ (30 pages, 17 figures), one new figure (Figure 10)
added, minor text changes; a version with high resolution figures available
at http://www.asiaa.sinica.edu.tw/~keiichi/upfiles/MACS1206/ms_highreso.pd
A highly magnified candidate for a young galaxy seen when the Universe was 500 Myrs old
The early Universe at redshift z\sim6-11 marks the reionization of the
intergalactic medium, following the formation of the first generation of stars.
However, those young galaxies at a cosmic age of \lesssim 500 million years
(Myr, at z \gtrsim 10) remain largely unexplored as they are at or beyond the
sensitivity limits of current large telescopes. Gravitational lensing by galaxy
clusters enables the detection of high-redshift galaxies that are fainter than
what otherwise could be found in the deepest images of the sky. We report the
discovery of an object found in the multi-band observations of the cluster
MACS1149+22 that has a high probability of being a gravitationally magnified
object from the early universe. The object is firmly detected (12 sigma) in the
two reddest bands of HST/WFC3, and not detected below 1.2 {\mu}m, matching the
characteristics of z\sim9 objects. We derive a robust photometric redshift of z
= 9.6 \pm 0.2, corresponding to a cosmic age of 490 \pm 15Myr (i.e., 3.6% of
the age of the Universe). The large number of bands used to derive the redshift
estimate make it one of the most accurate estimates ever obtained for such a
distant object. The significant magnification by cluster lensing (a factor of
\sim15) allows us to analyze the object's ultra-violet and optical luminosity
in its rest-frame, thus enabling us to constrain on its stellar mass,
star-formation rate and age. If the galaxy is indeed at such a large redshift,
then its age is less than 200 Myr (at the 95% confidence level), implying a
formation redshift of zf \lesssim 14. The object is the first z>9 candidate
that is bright enough for detailed spectroscopic studies with JWST,
demonstrating the unique potential of galaxy cluster fields for finding highly
magnified, intrinsically faint galaxies at the highest redshifts.Comment: Submitted to the Nature Journal. 39 Pages, 13 figure