Abstract
The thermodynamic properties of the hot plasma in galaxy clusters retain information on the processes leading to the formation and evolution of the gas in their deep, dark matter potential ...wells. These processes are dictated not only by gravity but also by gas physics, e.g., active galactic nucleus feedback and turbulence. In this work, we study the thermodynamic properties, e.g., density, temperature, pressure, and entropy, of the most massive and the most distant (seven clusters at
z
> 1.2) clusters selected by the South Pole Telescope and compare them with those of the nearby clusters (13 clusters at
z
< 0.1) to constrain their evolution as a function of time and radius. We find that thermodynamic properties in the outskirts of high-redshift clusters are remarkably similar to the low-redshift clusters, and their evolution follows the prediction of the self-similar model. Their intrinsic scatter is larger, indicating that the physical properties that lead to the formation and virialization of cluster outskirts show evolving variance. On the other hand, thermodynamic properties in the cluster cores deviate significantly from self-similarity, indicating that the processes that regulate the core are already in place in these very high redshift clusters. This result is supported by the unevolving physical scatter of all thermodynamic quantities in cluster cores.
Abstract
Strong gravitational lensing provides unique opportunities to investigate the mass distribution at the cores of galaxy clusters and to study high-redshift galaxies. Using 110 strong-lensing ...models of 74 cluster fields from the Hubble Frontier Fields (HFF), Reionization Lensing Cluster Survey (RELICS), and Sloan Giant Arcs Survey (SGAS), we evaluate the lensing strength of each cluster (area with ∣
μ
∣ ≥ 3 for
z
s
= 9, normalized to a lens redshift of
z
= 0.5). We assess how large-scale mass, projected inner-core mass, and the inner slope of the projected mass-density profile relate to lensing strength. While we do identify a possible trend between lensing strength and large-scale mass (Kendall
τ
= 0.26 and Spearman
r
= 0.36), we find that the inner slope (50 kpc ≤
r
≤ 200 kpc) of the projected mass-density profile has a higher probability of correlation with lensing strength and can set an upper bound on the possible lensing strength of a cluster (Kendall
τ
= 0.53 and Spearman
r
= 0.71). As anticipated, we find that the lensing strength correlates with the effective Einstein area and that a large ( ≳ 30.″0) radial extent of lensing evidence is a strong indicator of a powerful lens. We attribute the spread in the relation to the complexity of individual lensing clusters, which is well captured by the lensing-strength estimator. These results can help us to more efficiently design future observations to use clusters as cosmic telescopes.
We present an analysis of the mass distribution inferred from strong lensing by SPT-CL J0356−5337, a cluster of galaxies at redshift revealed in the follow-up of the SPT-SZ clusters. The cluster has ...an Einstein radius of 14″ for a source at z = 3 and a mass within 500 kpc of . Our spectroscopic identification of three multiply imaged systems ( , , and ), combined with HSTF606W-band imaging allows us to build a strong lensing model for this cluster with an rms of . Our modeling reveals a two-component mass distribution in the cluster. One mass component is dominated by the brightest cluster Galaxy and the other component, separated by ∼170 kpc, contains a group of eight red elliptical galaxies confined in a ∼9″ (∼70 kpc) diameter circle. We estimate the mass ratio between the two components to be between 1:1.25 and 1:1.58. In addition, spectroscopic data reveal that these two near-equal mass cores have only a small velocity difference of ∼300 km s−1 between the two components. This small radial velocity difference suggests that most of the relative velocity takes place in the plane of the sky, and implies that SPT-CL J0356−5337 is a major merger with a small impact parameter seen face-on. We also assess the relative contributions of Galaxy-scale halos to the overall mass of the core of the cluster and find that within 800 kpc from the brightest cluster Galaxy about 27% of the total mass can be attributed to visible and dark matter associated with galaxies, whereas only 73% of the total mass in the core comes from cluster-scale dark matter halos.
Abstract
In the third paper from the COOL–LAMPS Collaboration, we report the discovery of COOL J0542-2125, a gravitationally lensed quasar at
z
= 1.84, observed as three images due to an intervening ...massive galaxy cluster at
z
= 0.61. The lensed quasar images were identified in a search for lens systems in recent public optical imaging data and have separations on the sky up to 25.″9, wider than any previously known lensed quasar. The galaxy cluster acting as a strong lens appears to be in the process of merging, with two subclusters separated by ∼1 Mpc in the plane of the sky, and their central galaxies showing a radial velocity difference of ∼1000 km s
−1
. Both cluster cores show strongly lensed images of an assortment of background sources, as does the region between them. A preliminary strong lens model implies masses of
M
<
250
k
p
c
=
1.79
−
0.01
+
0.16
×
10
14
M
⊙
and
M
<
250
k
p
c
=
1.48
−
0.10
+
0.04
×
10
14
M
⊙
for the east and west subclusters, respectively. This line of sight is also coincident with an ROSAT ALL-sky Survey source, centered between the two confirmed cluster halos reminiscent of other major cluster-scale mergers. Archival and new follow-up imaging show flux variability in the quasar images of up to 0.4 mag within ∼1 yr, and new multicolor imaging data reveal a 2
σ
detection of the underlying quasar host. A lens system with this configuration offers rare opportunities for a range of future studies of both the lensed quasar and its host and the foreground cluster merger causing the lensing.
Abstract
We present a strong-lensing analysis of the cluster PSZ1 G311.65−18.48, based on Hubble Space Telescope imaging, archival VLT/MUSE spectroscopy, and Chandra X-ray data. This cool-core ...cluster (
z
= 0.443) lenses the brightest lensed galaxy known, dubbed the “Sunburst Arc” (
z
= 2.3703), a Lyman continuum (LyC) emitting galaxy multiply imaged 12 times. We identify in this field 14 additional strongly lensed galaxies to constrain a strong-lens model and report secure spectroscopic redshifts of four of them. We measure a projected cluster core mass of
M
(<250 kpc) =
2.93
−
0.02
+
0.01
×
10
14
M
⊙
. The two least magnified but complete images of the Sunburst Arc’s source galaxy are magnified by ∼13×, while the LyC clump is magnified by ∼4–80×. We present time delay predictions and conclusive evidence that a discrepant clump in the Sunburst Arc, previously claimed to be a transient, is not variable, thus strengthening the hypothesis that it results from an exceptionally high magnification. A source plane reconstruction and analysis of the Sunburst Arc finds its physical size to be 1 × 2 kpc and that it is resolved in three distinct directions in the source plane, 0°, 40°, and 75° (east of north). We place an upper limit of
r
≲ 50 pc on the source plane size of unresolved clumps and
r
≲ 32 pc for the LyC clump. Finally, we report that the Sunburst Arc is likely in a system of two or more galaxies separated by ≲6 kpc in projection. Their interaction may drive star formation and could play a role in the mechanism responsible for the leaking LyC radiation.
Abstract
We report the discovery of five bright, strong gravitationally lensed galaxies at 3 <
z
< 4: COOL J0101+2055 (
z
= 3.459), COOL J0104−0757 (
z
= 3.480), COOL J0145+1018 (
z
= 3.310), COOL ...J0516−2208 (
z
= 3.549), and COOL J1356+0339 (
z
= 3.753). These galaxies have magnitudes of
r
AB
,
z
AB
< 21.81 mag and are lensed by galaxy clusters at 0.26 <
z
< 1. This sample nearly doubles the number of known bright lensed galaxies with extended arcs at 3 <
z
< 4. We characterize the lensed galaxies using ground-based
grz
/
giy
imaging and optical spectroscopy. We report model-based magnitudes and derive stellar masses, dust content, and star formation rates via stellar population synthesis modeling. Building lens models based on ground-based imaging, we estimate source magnifications ranging from ∼29 to ∼180. Combining these analyses, we derive demagnified stellar masses in the range
log
10
(
M
*
/
M
⊙
)
∼
9.69
−
10.75
and star formation rates in the youngest age bin in the range
log
10
(
SFR
/
(
M
⊙
yr
−
1
)
)
∼
0.39
−
1.46
, placing the sample galaxies on the massive end of the star-forming main sequence in this redshift interval. In addition, three of the five galaxies have strong Ly
α
emissions, offering unique opportunities to study Ly
α
emitters at high redshift in future work.
Abstract
We present strong gravitational lensing models for 37 galaxy clusters from the Sloan Digital Sky Survey Giant Arcs Survey. We combine data from multi-band
Hubble Space Telescope
Wide Field ...Camera 3 (WFC3) imaging, with ground-based imaging and spectroscopy from
Magellan
, Gemini, Apache Point Observatory, and the Multiple Mirror Telescope, in order to detect and spectroscopically confirm new multiply imaged lensed background sources behind the clusters. We report spectroscopic or photometric redshifts of sources in these fields, including cluster galaxies and background sources. Based on all available lensing evidence, we construct and present strong-lensing mass models for these galaxy clusters. The clusters span a redshift range of 0.176 <
z
< 0.66 with a median redshift of
z
= 0.45, and sample a wide range of dynamical masses, 1.5 <
M
200
< 35 × 10
14
, as estimated from their velocity dispersions. As these clusters were selected as lenses primarily owing to a fortuitous alignment with background galaxies that results in giant arcs, they exhibit a wide range in Einstein radii, 1.″3 <
θ
E
< 23.″1 for a source at
z
= 2, with a median
θ
E
= 10.″8. The reduced
HST
images and lens model outputs are made available to the scientific community as high-level data products with this publication.
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