58 research outputs found
Probing coherence in metal absorption towards multiple images of strong gravitationally lensed quasars
We present a tomographic analysis of metal absorption lines arising from the
circumgalactic medium (CGM) of galaxies at z~0.5-2, using Multi Unit
Spectroscopic Explorer (MUSE) observations of two background quasars at z~2.2
and 2.8, which are two of the few currently known quasars with multiple images
due to strong gravitational lensing by galaxy clusters at z~0.6 and 0.5,
respectively. The angular separations between different pairs of quasar
multiple images enable us to probe the absorption over transverse physical
separations of ~0.4-150 kpc, which are based on strong lensing models
exploiting MUSE observations. The fractional difference in rest-frame
equivalent width (Delta Wr) of MgII, FeII, CIV absorption increases on average
with physical separation, indicating that the metal-enriched gaseous structures
become less coherent with distance, with a likely coherence length scale of ~10
kpc. However, Delta Wr for all the ions vary considerably over ~0.08-0.9,
indicating a clumpy CGM over the full range of length scales probed. At the
same time, paired MgII absorption is detected across ~100-150 kpc at similar
line-of-sight velocities, which could be probing cool gas clouds within the
same halo. No significant dependence of Delta Wr is found on the equivalent
width and redshift of the absorbing gas and on the galaxy environment
associated with the absorption. The high-ionization gas phase traced by CIV
shows a higher degree of coherence than the low-ionization gas phase traced by
MgII, with ~90 percent of CIV systems exhibiting Delta Wr <=0.5 at separations
<=10 kpc compared to ~50 percent of MgII systems.Comment: 9 pages + appendix, 8 figures, accepted in MNRA
Stellar Properties of z ~ 8 Galaxies in the Reionization Lensing Cluster Survey
Measurements of stellar properties of galaxies when the universe was less
than one billion years old yield some of the only observational constraints of
the onset of star formation. We present here the inclusion of
\textit{Spitzer}/IRAC imaging in the spectral energy distribution fitting of
the seven highest-redshift galaxy candidates selected from the \emph{Hubble
Space Telescope} imaging of the Reionization Lensing Cluster Survey (RELICS).
We find that for 6/8 \textit{HST}-selected sources, the
solutions are still strongly preferred over 1-2 solutions after the
inclusion of \textit{Spitzer} fluxes, and two prefer a solution,
which we defer to a later analysis. We find a wide range of intrinsic stellar
masses ( -- ), star formation
rates (0.2-14 ), and ages (30-600 Myr) among our sample.
Of particular interest is Abell1763-1434, which shows evidence of an evolved
stellar population at , implying its first generation of star formation
occurred just Myr after the Big Bang. SPT0615-JD, a spatially resolved
candidate, remains at its high redshift, supported by deep
\textit{Spitzer}/IRAC data, and also shows some evidence for an evolved stellar
population. Even with the lensed, bright apparent magnitudes of these candidates (H = 26.1-27.8 AB mag), only the \textit{James Webb Space
Telescope} will be able further confirm the presence of evolved stellar
populations early in the universe.Comment: 8 pages, 3 figures, 2 table
RELICS: High-Resolution Constraints on the Inner Mass Distribution of the z=0.83 Merging Cluster RXJ0152.7-1357 from strong lensing
Strong gravitational lensing (SL) is a powerful means to map the distribution
of dark matter. In this work, we perform a SL analysis of the prominent X-ray
cluster RXJ0152.7-1357 (z=0.83, also known as CL 0152.7-1357) in \textit{Hubble
Space Telescope} images, taken in the framework of the Reionization Lensing
Cluster Survey (RELICS). On top of a previously known galaxy multiply
imaged by RXJ0152.7-1357, for which we identify an additional multiple image,
guided by a light-traces-mass approach we identify seven new sets of multiply
imaged background sources lensed by this cluster, spanning the redshift range
[1.79-3.93]. A total of 25 multiple images are seen over a small area of ~0.4
, allowing us to put relatively high-resolution constraints on the
inner matter distribution. Although modestly massive, the high degree of
substructure together with its very elongated shape make RXJ0152.7-1357 a very
efficient lens for its size. This cluster also comprises the third-largest
sample of z~6-7 candidates in the RELICS survey. Finally, we present a
comparison of our resulting mass distribution and magnification estimates with
those from a Lenstool model. These models are made publicly available through
the MAST archive.Comment: 15 Pages, 7 Figures, 4 Tables Accepted for publication in Ap
A persistent excess of galaxy-galaxy strong lensing observed in galaxy clusters
Previous studies have revealed that the estimated probability of
galaxy-galaxy strong lensing in observed galaxy clusters exceeds the
expectations from the Cold Dark Matter cosmological model by one
order of magnitude. We aim to understand the origin of this excess by analyzing
a larger set of simulated galaxy clusters and investigating how the theoretical
expectations vary under different adopted prescriptions and numerical
implementations of star formation and feedback in simulations. We perform a
ray-tracing analysis of 324 galaxy clusters from the Three Hundred project,
comparing the Gadget-X and Gizmo-Simba runs. These simulations, which start
from the same initial conditions, are performed with different implementations
of hydrodynamics and galaxy formation models tailored to match different
observational properties of the Intra-Cluster-Medium and cluster galaxies. We
find that galaxies in the Gizmo-Simba simulations develop denser stellar cores
than their Gadget-X counterparts. Consequently, their probability for
galaxy-galaxy strong lensing is higher by a factor of . This increment
is still insufficient to fill the gap with observations, as a discrepancy by a
factor still persists. In addition, we find that several simulated
galaxies have Einstein radii that are too large compared to observations. We
conclude that a persistent excess of galaxy-galaxy strong lensing exists in
observed galaxy clusters. The origin of this discrepancy with theoretical
predictions is still unexplained in the framework of the cosmological
hydrodynamical simulations. This might signal a hitherto unknown issue with
either the simulation methods or our assumptions regarding the standard
cosmological model.Comment: 6 pages, 2 figures, accepted for publication on A&A Letters. See
companion paper Srivastava et al. (2023
Beyond the Ultra-deep Frontier Fields And Legacy Observations (BUFFALO): a high-resolution strong + weak-lensing view of Abell 370
The HST treasury program BUFFALO provides extended wide-field imaging of the
six Hubble Frontier Fields galaxy clusters. Here we present the combined strong
and weak-lensing analysis of Abell 370, a massive cluster at z=0.375. From the
reconstructed total projected mass distribution in the 6arcmin x 6arcmin
BUFFALO field-of-view, we obtain the distribution of massive substructures
outside the cluster core and report the presence of a total of seven
candidates, each with mass . Combining the
total mass distribution derived from lensing with multi-wavelength data, we
evaluate the physical significance of each candidate substructure, and conclude
that 5 out of the 7 substructure candidates seem reliable, and that the mass
distribution in Abell 370 is extended along the North-West and South-East
directions. While this finding is in general agreement with previous studies,
our detailed spatial reconstruction provides new insights into the complex mass
distribution at large cluster-centric radius. We explore the impact of the
extended mass reconstruction on the model of the cluster core and in
particular, we attempt to physically explain the presence of an important
external shear component, necessary to obtain a low root-mean-square separation
between the model-predicted and observed positions of the multiple images in
the cluster core. The substructures can only account for up to half the
amplitude of the external shear, suggesting that more effort is needed to fully
replace it by more physically motivated mass components. We provide public
access to all the lensing data used as well as the different lens models.Comment: 29 pages, 17 figures, 3 table
The production of ionizing photons in UV-faint z~3-7 galaxies
The demographics of the production and escape of ionizing photons from
UV-faint early galaxies is a key unknown in discovering the primary drivers of
reionization. With the advent of JWST it is finally possible to observe the
rest-frame optical nebular emission from individual sub-L z>3 galaxies to
measure the production of ionizing photons, . Here we study a
sample of 380 z~3-7 galaxies spanning -23 <M < -15.5 (median
M -18) with deep multi-band HST and JWST/NIRCam photometry
covering the rest-UV to optical from the GLASS and UNCOVER JWST surveys. Our
sample includes 109 galaxies with Lyman-alpha emission detected in MUSE
spectroscopy. We use H-alpha fluxes inferred from NIRCam photometry to estimate
the production rate of ionizing photons which do not escape these galaxies
. We find median
, with a broad
intrinsic scatter 0.42 dex, implying a broad range of galaxy properties and
ages in our UV-faint sample. Galaxies detected with Lyman-alpha have ~0.1 dex
higher , which is explained by their higher
H-alpha EW distribution, implying younger ages, higher sSFR and thus more O/B
stars. We find significant trends of increasing
with increasing H-alpha EW, decreasing UV
luminosity, and decreasing UV slope, implying the production of ionizing
photons is enhanced in young, low metallicity galaxies. We find no significant
evidence for sources with very high ionizing escape fraction
(>0.5) in our sample, based on their photometric properties,
even amongst the Lyman-alpha selected galaxies. This work demonstrates that
considering the full distribution of across galaxy
properties is important for assessing the primary drivers of reionization.Comment: 10 pages, 7 figures, submitted to A&
A Strong-Lensing Model for the WMDF JWST/GTO Very Rich Cluster Abell 1489
We present a first strong-lensing model for the galaxy cluster RM
J121218.5+273255.1 (; hereafter RMJ1212; also known as Abell 1489).
This cluster is amongst the top 0.1\% richest clusters in the redMaPPer
catalog; it is significantly detected in X-ray and through the
Sunyaev-Zel'dovich effect in ROSAT and \emph{Planck} data, respectively; and
its optical luminosity distribution implies a very large lens, following
mass-to-light scaling relations. Based on these properties it was chosen for
the Webb Medium Deep Fields (WMDF) JWST/GTO program. In preparation for this
program, RMJ1212 was recently imaged with GMOS on Gemini North and in seven
optical and near-infrared bands with the \emph{Hubble Space Telescope}. We use
these data to map the inner mass distribution of the cluster, uncovering
various sets of multiple images. We also search for high-redshift candidates in
the data, as well as for transient sources. We find over a dozen high-redshift
() candidates based on both photometric redshift and the dropout
technique. No prominent () transients were found in the data
between the two HST visits. Our lensing analysis reveals a relatively large
lens with an effective Einstein radius of
(), in broad agreement with the scaling-relation expectations. RMJ1212
demonstrates that powerful lensing clusters can be selected in a robust and
automated way following the light-traces-mass assumption.Comment: 17 pages, 6 figures, 2 tables; To be submitte
Pilot-WINGS: An extended MUSE view of the structure of Abell 370
We investigate the strong-lensing cluster Abell 370 (A370) using a wide Integral Field Unit (IFU) spectroscopic mosaic from the Multi-Unit Spectroscopic Explorer (MUSE). IFU spectroscopy provides significant insight into the structure and mass content of galaxy clusters, yet IFU-based cluster studies focus almost exclusively on the central Einstein-radius region. Covering over 14 arcmin2, the new MUSE mosaic extends significantly beyond the A370 Einstein radius, providing, for the first time, a detailed look at the cluster outskirts. Combining these data with wide-field, multi-band Hubble Space Telescope (HST) imaging from the BUFFALO project, we analyse the distribution of objects within the cluster and along the line of sight. Identifying 416 cluster galaxies, we use kinematics to trace the radial mass profile of the halo, providing a mass estimate independent from the lens model. We also measure radially averaged properties of the cluster members, tracking their evolution as a function of infall. Thanks to the high spatial resolution of our data, we identify six cluster members acting as galaxy–galaxy lenses, which constrain localized mass distributions beyond the Einstein radius. Finally, taking advantage of MUSE’s 3D capabilities, we detect and analyse multiple spatially extended overdensities outside of the cluster that influence lensing-derived halo mass estimates. We stress that much of this work is only possible thanks to the robust, extended IFU coverage, highlighting its importance even in less optically dense cluster regions. Overall, this work showcases the power of combining HST + MUSE, and serves as the initial step towards a larger and wider program targeting several clusters
The probability of galaxy-galaxy strong lensing events in hydrodynamical simulations of galaxy clusters
Meneghetti et al. (2020) recently reported an excess of galaxy-galaxy strong
lensing (GGSL) in galaxy clusters compared to expectations from the LCDM
cosmological model. Theoretical estimates of the GGSL probability are based on
the analysis of numerical hydrodynamical simulations in the LCDM cosmology. We
quantify the impact of the numerical resolution and AGN feedback scheme adopted
in cosmological simulations on the predicted GGSL probability and determine if
varying these simulation properties can alleviate the gap with observations. We
repeat the analysis of Meneghetti et al. (2020) on cluster-size halos simulated
with different mass and force resolutions and implementing several independent
AGN feedback schemes. We find that improving the mass resolution by a factor of
ten and twenty-five, while using the same galaxy formation model that includes
AGN feedback, does not affect the GGSL probability. We find similar results
regarding the choice of gravitational softening. On the contrary, adopting an
AGN feedback scheme that is less efficient at suppressing gas cooling and star
formation leads to an increase in the GGSL probability by a factor between
three and six. However, we notice that such simulations form overly massive
subhalos whose contribution to the lensing cross-section would be significant
while their Einstein radii are too large to be consistent with the
observations. The primary contributors to the observed GGSL cross-sections are
subhalos with smaller masses, that are compact enough to become critical for
lensing. The population with these required characteristics appears to be
absent in simulations.Comment: 13 pages, 11 figures. Submitted for publication on Astronomy and
Astrophysic
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