We carried out a detailed strong lensing analysis of a sub-sample of eight galaxy clusters of the Cluster Lensing And Supernova survey with Hubble (CLASH) in the redshift range of zcluster = 0.23 − ...0.59 using extensive spectroscopic information, primarily from the Multi Unit Spectroscopic Explorer (MUSE) archival data and complemented with CLASH-VLT redshift measurements. The observed positions of the multiple images of strongly lensed background sources were used to constrain parametric models describing the cluster total mass distributions. Different models were tested in each cluster depending on the complexity of its mass distribution and on the number of detected multiple images. Four clusters show more than five spectroscopically confirmed multiple image families. In this sample, we did not make use of families that are only photometrically identified in order to reduce model degeneracies between the values of the total mass of a cluster source redshifts, in addition to systematics due to the potential misidentifications of multiple images. For the remaining four clusters, we used additional families without any spectroscopic confirmation to increase the number of strong lensing constraints up to the number of free parameters in our parametric models. We present spectroscopic confirmation of 27 multiply lensed sources, with no previous spectroscopic measurements, spanning over the redshift range of zsrc = 0.7 − 6.1. Moreover, we confirm an average of 48 galaxy members in the core of each cluster thanks to the high efficiency and large field of view of MUSE. We used this information to derive precise strong lensing models, projected total mass distributions, and magnification maps. We show that, despite having different properties (i.e. number of mass components, total mass, redshift, etc.), the projected total mass and mass density profiles of all clusters have very similar shapes when rescaled by independent measurements of M200c and R200c. Specifically, we measured the mean value of the projected total mass of our cluster sample within 10 (20)% of R200c to be 0.13 (0.32) of M200c, with a remarkably small scatter of 5 (6)%. Furthermore, the large number of high-z sources and the precise magnification maps derived in this work for four clusters add up to the sample of high-quality gravitational telescopes to be used to study the faint and distant Universe.
Aims. We aim constrain the assembly history of clusters by studying the intracluster light (ICL) properties, estimating its contribution to the fraction of baryons in stars, f∗, and understanding ...possible systematics or bias using different ICL detection techniques. Methods. We developed an automated method, GALtoICL, based on the software GALAPAGOS, to obtain a refined version of typical BCG+ICL maps. We applied this method to our test case MACS J1206.2-0847, a massive cluster located at z ~ 0.44, which is part of the CLASH sample. Using deep multiband Subaru images, we extracted the surface brightness (SB) profile of the BCG+ICL and studied the ICL morphology, color, and contribution to f∗ out to R500. We repeated the same analysis using a different definition of the ICL, SBlimit method, i.e., a SB cut-off level, to compare the results. Results. The most peculiar feature of the ICL in MACS1206 is its asymmetric radial distribution, with an excess in the SE direction and extending toward the second brightest cluster galaxy, which is a post starburst galaxy. This suggests an interaction between the BCG and this galaxy that dates back to τ ≤ 1.5 Gyr. The BCG+ICL stellar content is ~8% of M∗,500, and the (de-) projected baryon fraction in stars is f∗ = 0.0177(0.0116), in excellent agreement with recent results. The SBlimit method provides systematically higher ICL fractions and this effect is stronger at lower SB limits. This is due to the light from the outer envelopes of member galaxies that contaminate the ICL. Though more time consuming, the GALtoICL method provides safer ICL detections that are almost free of this contamination. This is one of the few ICL study at redshift z > 0.3. At completion, the CLASH/VLT program will allow us to extend this analysis to a statistically significant cluster sample spanning a wide redshift range: 0.2 ≲ z ≲ 0.6.
We present a detailed mass reconstruction and a novel study on the substructure properties in the core of the Cluster Lensing And Supernova survey with Hubble (CLASH) and Frontier Fields galaxy ...clusterMACS J0416.1-2403. We reproduce the measured positions of a set of 30 multiple images with a remarkable median offset of only 0.3 by means of a comprehensive strong lensing model comprised of two cluster dark-matter halos, represented by cored elliptical pseudo-isothermal mass distributions, and the cluster member components, parameterized with dual pseudo-isothermal total mass profiles. We investigate the galaxy contribution, both in terms of total and stellar mass, to the total mass budget of the cluster. Our findings of the location and shape of the cluster dark-matter halo density profiles and on the cluster substructures provide intriguing tests of the assumed collisionless, cold nature of dark matter and of the role played by baryons in the process of structure formation.
ABSTRACT
We present spectroscopic observations obtained at the Large Binocular Telescope in the field of the cluster XLSSJ0223−0436 at z = 1.22. We confirm 12 spheroids cluster members and determine ...stellar velocity dispersion for 7 of them. We combine these data with those in the literature for clusters RXJ0848+4453 at z = 1.27 (8 galaxies) and XMMJ2235−2557 at z = 1.39 (7 galaxies) to determine the Fundamental Plane (FP) of cluster spheroids. We find that the FP at z ∼ 1.3 is offset and rotated (∼3σ) with respect to the local FP. The offset corresponds to a mean evolution Δlog(Mdyn/LB) = (−0.5 ± 0.1)z. High-redshift galaxies follow a steeper mass-dependent Mdyn/LB–Mdyn relation than local ones. Assuming Δ log(Mdyn/LB) = Δ log(M*/LB), higher mass galaxies log(Mdyn/M⊙) ≥ 11.5 have a higher formation redshift (zf ≥ 6.5) than lower mass ones zf ≤2 for log(Mdyn/M⊙ ≤ 10), with a median zf ≃ 2.5 for the whole sample. Also, galaxies with higher stellar mass density host stellar populations formed earlier than those in lower density galaxies. At fixed initial mass function, Mdyn/M* varies systematically with mass and mass density. It follows that the evolution of the stellar populations (M*/LB) accounts for the observed evolution of Mdyn/LB for Mdyn > 1011 M⊙ galaxies, while accounts for ∼85 per cent of the evolution at Mdyn < 1011 M⊙. We find no evidence in favour of structural evolution of individual galaxies, while we find evidences that spheroids later added to the population may account for the observed discrepancy between Δlog(Mdyn/LB) and Δ log(M*/LB) at masses <1011 M⊙. Thus, the evolution of the FP of cluster spheroids is consistent with the mass-dependent and mass density-dependent evolution of their stellar populations superimposed to a minor contribution of spheroids joining the population at later times.
We present a multiwavelength study of the massive ( M 200 c ( 1 - 2 ) × 10 15 M ) galaxy clusters RXC J2248.7−4431, MACS J0416.1−2403, and MACS J1206.2−0847 at z 0.4. Using the X-ray surface ...brightness of the clusters from the deep Chandra data to model their hot gas, we are able to disentangle this mass term from the diffuse dark matter (DM) in our new strong-lensing analysis, with approximately 50-100 secure multiple images per cluster, effectively separating the collisional and collisionless mass components of the clusters. At a radial distance of 10% of R200c (approximately 200 kpc), we measure a projected total mass of (0.129 0.001), (0.131 0.001) and (0.137 0.001) × M200c, for RXC J2248, MACS J0416 and MACS J1206, respectively. These values are surprisingly similar considering the large differences in the merging configurations and, consequently, in the mass models of the clusters. Interestingly, at the same radii, the hot gas over total mass fractions differ substantially, ranging from 0.082 0.001 to 0.133 0.001, which reflects the various dynamical states of the clusters. Moreover, we do not find a statistically significant offset between the positions of the peak of the diffuse DM component and of the BCG in the more complex clusters of the sample. We extend the previous findings of a number of massive sub-halos that are higher than in numerical simulations to this sample of clusters. Our results highlight the importance of a proper separation of the different mass components to study the properties of DM in galaxy clusters in detail.
Context. The analysis of galaxy properties, such as stellar masses, colors, sizes and morphologies, and the relations among them and the environment, in which the galaxies reside, can be used to ...investigate the physical processes driving galaxy evolution. Aims. We conduct a thorough study of the cluster A209 with a new large spectro-photometric dataset to investigate possible environmental effects on galaxy properties that can provide information on galaxy evolution in cluster hostile environments. Methods. We use the dataset obtained as part of the CLASH-VLT spectroscopic survey, supplemented with Subaru/SuprimeCam high-quality imaging in BVRIz-bands, which yields 1916 cluster members (50% of them spectroscopically confirmed) down to a stellar mass M⋆ = 108.6 M⊙. We determine the stellar mass function of these galaxies in different regions of the cluster, by separating the sample into star-forming and passive cluster members. We then determine the intra-cluster light and its properties. We also derive the orbits of low- (M⋆ ≤ 1010.0 M⊙) and high-mass (M⋆ > 1010.0 M⊙) passive galaxies and study the effect of the environment on the mass-size relation of early-type galaxies, selected according to their Sérsic index; the effects are studied separately for the galaxies in each mass range. Finally, we compare the cluster stellar mass density profile with the number density and total-mass density profiles. Results. The stellar mass function of the star-forming cluster galaxies does not depend on the environment. The slope found for passive galaxies becomes flatter in the densest cluster region, which implies that the low-mass component starts to dominate when moving away from the cluster center. The color distribution of the intra-cluster light is consistent with the color of passive cluster members. The analysis of the dynamical orbits of passive galaxies shows that low-mass galaxies have tangential orbits, avoiding small pericenters around the BCG. The mass-size relation of low-mass passive early-type galaxies is flatter than that of high-mass galaxies, and its slope is consistent with the slope of the relation of field star-forming galaxies. Low-mass galaxies are also more compact within the scale radius of 0.65 Mpc. The ratio between the stellar and number density profiles shows a mass segregation effect in the cluster center. The comparative analysis of the stellar and total density profiles indicates that this effect is due to dynamical friction. Conclusions. Our results are consistent with a scenario in which the “environmental quenching” of low-mass galaxies is due to mechanisms such as harassment out to r200, starvation, and ram-pressure stripping at smaller radii. This scenario is supported by the analysis of the mass function, of the dynamical orbits and of the mass-size relation of passive early-type galaxies in different cluster regions. Moreover, our analyses support the idea that the intra-cluster light is formed through the tidal disruption of subgiant (M⋆ ~ 109.5−10.0 M⊙) galaxies. In fact, our results suggest that low-mass galaxies are destroyed by tidal interactions, and that those that avoid small pericenters around the BCG are influenced by tidal interactions that reduce their sizes. We suggest dynamical friction as the process responsible for the observed mass segregation.
Aims. We perform a comprehensive study of the total mass distribution of the galaxy cluster RXC J2248.7−4431 (z = 0.348) with a set of high-precision strong lensing models, which take advantage of ...extensive spectroscopic information on many multiply lensed systems. In the effort to understand and quantify inherent systematics in parametric strong lensing modelling, we explore a collection of 22 models in which we use different samples of multiple image families, different parametrizations of the mass distribution and cosmological parameters. Methods. As input information for the strong lensing models, we use the Cluster Lensing And Supernova survey with Hubble (CLASH) imaging data and spectroscopic follow-up observations, with the VIsible Multi-Object Spectrograph (VIMOS) and Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT), to identify and characterize bona fide multiple image families and measure their redshifts down to mF814W ≃ 26. A total of 16 background sources, over the redshift range 1.0−6.1, are multiply lensed into 47 images, 24 of which are spectroscopically confirmed and belong to ten individual sources. These also include a multiply lensed Lyman-α blob at z = 3.118. The cluster total mass distribution and underlying cosmology in the models are optimized by matching the observed positions of the multiple images on the lens plane. Bayesian Markov chain Monte Carlo techniques are used to quantify errors and covariances of the best-fit parameters. Results. We show that with a careful selection of a large sample of spectroscopically confirmed multiple images, the best-fit model can reproduce their observed positions with a rms scatter of 0.̋3 in a fixed flat ΛCDM cosmology, whereas the lack of spectroscopic information or the use of inaccurate photometric redshifts can lead to biases in the values of the model parameters. We find that the best-fit parametrization for the cluster total mass distribution is composed of an elliptical pseudo-isothermal mass distribution with a significant core for the overall cluster halo and truncated pseudo-isothermal mass profiles for the cluster galaxies. We show that by adding bona fide photometric-selected multiple images to the sample of spectroscopic families, one can slightly improve constraints on the model parameters. In particular, we find that the degeneracy between the lens total mass distribution and the underlying geometry of the Universe, which is probed via angular diameter distance ratios between the lens and sources and the observer and sources, can be partially removed. Allowing cosmological parameters to vary together with the cluster parameters, we find (at 68% confidence level) Ωm = 0.25+ 0.13-0.16 and w = −1.07+ 0.16-0.42 for a flat ΛCDM model, and Ωm = 0.31+ 0.12-0.13 and ΩΛ = 0.38+ 0.38-0.27 for a Universe with w = −1 and free curvature. Finally, using toy models mimicking the overall configuration of multiple images and cluster total mass distribution, we estimate the impact of the line-of-sight mass structure on the positional rms to be 0.̋3 ± 0. We argue that the apparent sensitivity of our lensing model to cosmography is due to the combination of the regular potential shape of RXC J2248, a large number of bona fide multiple images out to z = 6.1, and a relatively modest presence of intervening large-scale structure, as revealed by our spectroscopic survey.
We present a high-resolution dissection of the two-dimensional total mass distribution in the core of the Hubble Frontier Fields galaxy cluster MACS J0416.1−2403, at z = 0.396. We exploit HST/WFC3 ...near-IR (F160W) imaging, VLT/Multi Unit Spectroscopic Explorer spectroscopy, and Chandra data to separate the stellar, hot gas, and dark-matter mass components in the inner 300 kpc of the cluster. We combine the recent results of our refined strong lensing analysis, which includes the contribution of the intracluster gas, with the modeling of the surface brightness and stellar mass distributions of 193 cluster members, of which 144 are spectroscopically confirmed. We find that, moving from 10 to 300 kpc from the cluster center, the stellar to total mass fraction decreases from 12% to 1% and the hot gas to total mass fraction increases from 3% to 9%, resulting in a baryon fraction of approximatively 10% at the outermost radius. We measure that the stellar component represents ∼30%, near the cluster center, and 15%, at larger clustercentric distances, of the total mass in the cluster substructures. We subtract the baryonic mass component from the total mass distribution and conclude that within 30 kpc (∼3 times the effective radius of the brightest cluster galaxy) from the cluster center the surface mass density profile of the total mass and global (cluster plus substructures) dark-matter are steeper and that of the diffuse (cluster) dark-matter is shallower than an NFW profile. Our current analysis does not point to a significant offset between the cluster stellar and dark-matter components. This detailed and robust reconstruction of the inner dark-matter distribution in a larger sample of galaxy clusters will set a new benchmark for different structure formation scenarios.
Abstract
We make use of JWST medium-band and broadband NIRCam imaging, along with ultradeep MIRI 5.6
μ
m imaging, in the Hubble eXtreme Deep Field to identify prominent line emitters at
z
≃ 7–8. Out ...of a total of 58 galaxies at
z
≃ 7–8, we find 18 robust candidates (≃31%) for (H
β
+ O
iii
) emitters, based on their enhanced fluxes in the F430M and F444W filters, with EW
0
(H
β
+O
iii
) ≃87–2100 Å. Among these emitters, 16 lie in the MIRI coverage area and 12 exhibit a clear flux excess at 5.6
μ
m, indicating the simultaneous presence of a prominent H
α
emission line with EW
0
(H
α
) ≃200–3000 Å. This is the first time that H
α
emission can be detected in individual galaxies at
z
> 7. The H
α
line, when present, allows us to separate the contributions of H
β
and O
iii
to the (H
β
+O
iii
) complex and derive H
α
-based star formation rates (SFRs). We find that in most cases O
iii
/H
β
> 1. Instead, two galaxies have O
iii
/H
β
< 1, indicating that the NIRCam flux excess is mainly driven by H
β
. Most prominent line emitters are very young starbursts or galaxies on their way to/from the starburst cloud. They make for a cosmic SFR density
log
10
(
ρ
SFR
H
α
/
(
M
⊙
yr
−
1
Mpc
−
3
)
)
≃
−
2.35
, which is about a quarter of the total value (
log
10
(
ρ
SFR
tot
/
(
M
⊙
yr
−
1
Mpc
−
3
)
)
≃
−
1.76
) at
z
≃ 7–8. Therefore, the strong H
α
emitters likely had a significant role in reionization.
We present a novel approach for a combined analysis of X-ray and gravitational lensing data and apply this technique to the merging galaxy cluster MACS J0416.1-2403. The method exploits the ...information on the intracluster gas distribution that comes from a fit of the X-ray surface brightness and then includes the hot gas as a fixed mass component in the strong-lensing analysis. With our new technique, we can separate the collisional from the collision-less diffuse mass components, thus obtaining a more accurate reconstruction of the dark matter distribution in the core of a cluster. We introduce an analytical description of the X-ray emission coming from a set of dual pseudo-isothermal elliptical mass distributions, which can be directly used in most lensing softwares. By combining Chandra observations with Hubble Frontier Fields imaging and Multi Unit Spectroscopic Explorer spectroscopy in MACS J0416.1-2403, we measure a projected gas-to-total mass fraction of approximately 10% at 350 kpc from the cluster center. Compared to the results of a more traditional cluster mass model (diffuse halos plus member galaxies), we find a significant difference in the cumulative projected mass profile of the dark matter component and that the dark matter over total mass fraction is almost constant, out to more than 350 kpc. In the coming era of large surveys, these results show the need of multiprobe analyses for detailed dark matter studies in galaxy clusters.
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