10 research outputs found
The unrelaxed dynamical structure of the galaxy cluster Abell 85
For the first time, we explore the dynamics of the central region of a galaxy
cluster within ~kpc from its center by combining optical
and X-ray spectroscopy. We use (1) the caustic technique that identifies the
cluster substructures and their galaxy members with optical spectroscopic data,
and (2) the X-ray redshift fitting procedure that estimates the redshift
distribution of the intracluster medium (ICM). We use the spatial and redshift
distributions of the galaxies and of the X-ray emitting gas to associate the
optical substructures to the X-ray regions. When we apply this approach to
Abell 85 (A85), a complex dynamical structure of A85 emerges from our analysis:
a galaxy group, with redshift is passing through the
cluster center along the line of sight dragging part of the ICM present in the
cluster core; two additional groups, at redshift and
, are going through the cluster in opposite directions,
almost perpendicularly to the line of sight, and have substantially perturbed
the dynamics of the ICM. An additional group in the outskirts of A85, at
redshift , is associated to a secondary peak of the X-ray
emission, at redshift . Although our analysis and
results on A85 need to be confirmed by high-resolution spectroscopy, they
demonstrate how our new approach can be a powerful tool to constrain the
formation history of galaxy clusters by unveiling their central and surrounding
structures.Comment: 12 pages, 11 figures, accepted by Ap
RELICS: Strong Lensing analysis of the galaxy clusters Abell S295, Abell 697, MACS J0025.4-1222, and MACS J0159.8-0849
We present a strong-lensing analysis of four massive galaxy clusters imaged
with the Hubble Space Telescope in the Reionization Lensing Cluster Survey. We
use a Light-Traces-Mass technique to uncover sets of multiply images and
constrain the mass distribution of the clusters. These mass models are the
first published for Abell S295 and MACS J0159.8-0849, and are improvements over
previous models for Abell 697 and MACS J0025.4-1222. Our analysis for MACS
J0025.4-1222 and Abell S295 shows a bimodal mass distribution supporting the
merger scenarios proposed for these clusters. The updated model for MACS
J0025.4-1222 suggests a substantially smaller critical area than previously
estimated. For MACS J0159.8-0849 and Abell 697 we find a single peak and
relatively regular morphology, revealing fairly relaxed clusters. Despite being
less prominent lenses, three of these clusters seem to have lensing strengths,
i.e. cumulative area above certain magnification, similar to the Hubble
Frontier Fields clusters (e.g., A() arcmin, A()
arcmin), which in part can be attributed to their merging
configurations. We make our lens models publicly available through the Mikulski
Archive for Space Telescopes. Finally, using Gemini-N/GMOS spectroscopic
observations we detect a single emission line from a high-redshift
galaxy candidate lensed by Abell 697. While we cannot rule
out a lower-redshift solution, we interpret the line as Ly at
, in agreement with its photometric redshift and dropout
nature. Within this scenario we measure a Ly rest-frame equivalent
width of \AA, and an observed Gaussian width of km/s.Comment: 23 pages, 16 figures; V2, accepted for publication in Ap
RELICS: Reionization Lensing Cluster Survey
Large surveys of galaxy clusters with the Hubble and Spitzer Space
Telescopes, including CLASH and the Frontier Fields, have demonstrated the
power of strong gravitational lensing to efficiently deliver large samples of
high-redshift galaxies. We extend this strategy through a wider, shallower
survey named RELICS, the Reionization Lensing Cluster Survey. This survey,
described here, was designed primarily to deliver the best and brightest
high-redshift candidates from the first billion years after the Big Bang.
RELICS observed 41 massive galaxy clusters with Hubble and Spitzer at 0.4-1.7um
and 3.0-5.0um, respectively. We selected 21 clusters based on Planck PSZ2 mass
estimates and the other 20 based on observed or inferred lensing strength. Our
188-orbit Hubble Treasury Program obtained the first high-resolution
near-infrared images of these clusters to efficiently search for lensed
high-redshift galaxies. We observed 46 WFC3/IR pointings (~200 arcmin^2) with
two orbits divided among four filters (F105W, F125W, F140W, and F160W) and ACS
imaging as needed to achieve single-orbit depth in each of three filters
(F435W, F606W, and F814W). As previously reported by Salmon et al., we
discovered 322 z ~ 6 - 10 candidates, including the brightest known at z ~ 6,
and the most distant spatially-resolved lensed arc known at z ~ 10. Spitzer
IRAC imaging (945 hours awarded, plus 100 archival) has crucially enabled us to
distinguish z ~ 10 candidates from z ~ 2 interlopers. For each cluster, two HST
observing epochs were staggered by about a month, enabling us to discover 11
supernovae, including 3 lensed supernovae, which we followed up with 20 orbits
from our program. We delivered reduced HST images and catalogs of all clusters
to the public via MAST and reduced Spitzer images via IRSA. We have also begun
delivering lens models of all clusters, to be completed before the JWST GO call
for proposals.Comment: 29 pages, 6 figures, submitted to ApJ. For reduced images, catalogs,
lens models, and more, see relics.stsci.ed
Utilisation sous Multics de la bibliotheque LTSM (Logiciel de Traitements Statistiques Multidimensionnels)
SIGLECNRS-CDST / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
RELICS: Strong-lensing Analysis of the Massive Clusters MACS J0308.9+2645 and PLCK G171.9−40.7
Strong gravitational lensing by galaxy clusters has become a powerful tool for probing the high-redshift universe, magnifying distant and faint background galaxies. Reliable strong-lensing (SL) models are crucial for determining the intrinsic properties of distant, magnified sources and for constructing their luminosity function. We present here the first SL analysis of MACS J0308.9+2645 and PLCK G171.9-40.7, two massive galaxy clusters imaged with the Hubble Space Telescope, in the framework of the Reionization Lensing Cluster Survey (RELICS). We use the light-traces-mass modeling technique to uncover sets of multiply imaged galaxies and constrain the mass distribution of the clusters. Our SL analysis reveals that both clusters have particularly large Einstein radii (theta(E) > 30 '' for a source redshift of z(s) = 2), providing fairly large areas with high magnifications, useful for high-redshift galaxy searches (similar to 2 arcmin(2) with mu > 5 to similar to 1 arcmin(2) with mu > 10, similar to a typical Hubble Frontier Fields cluster). We also find that MACS J0308.9+2645 hosts a promising, apparently bright (J similar to 23.2-24.6 AB), multiply imaged high-redshift candidate at z similar to 6.4. These images are among the brightest high-redshift candidates found in RELICS. Our mass models, including magnification maps, are made publicly available for the community through the Mikulski Archive for Space Telescopes.NASA/ESA HST [GO-14096]; NASA through a Space Telescope Science Institute [GO-14096]; NASA [NAS5-26555]; U.S. Department of Energy by Lawrence Livermore National Laboratory [DE-AC52-07NA27344]; Australian Research Council Discovery Early Career Researcher Award [DE180101240]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]