650 research outputs found
The SPTPoL extended cluster survey
ArtĂculo escrito por un elevado nĂșmero de autores, sĂłlo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboraciĂłn, si lo hubiereWe describe the observations and resultant galaxy cluster catalog from the 2770 deg2 SPTpol Extended Cluster Survey (SPT-ECS). Clusters are identified via the Sunyaev-Zel'dovich (SZ) effect and confirmed with a combination of archival and targeted follow-up data, making particular use of data from the Dark Energy Survey (DES). With incomplete follow-up we have confirmed as clusters 244 of 266 candidates at a detection significance Ο â„ 5 and an additional 204 systems at 4 4 threshold, and 10% of their measured SZ flux. We associate SZ-selected clusters, from both SPT-ECS and the SPT-SZ survey, with clusters from the DES redMaPPer sample, and we find an offset distribution between the SZ center and central galaxy in general agreement with previous work, though with a larger fraction of clusters with significant offsets. Adopting a fixed Planck-like cosmology, we measure the optical richness-SZ mass (l - M) relation and find it to be 28% shallower than that from a weak-lensing analysis of the DES data-a difference significant at the 4Ï level-with the relations intersecting at λ = 60. The SPT-ECS cluster sample will be particularly useful for studying the evolution of massive clusters and, in combination with DES lensing observations and the SPT-SZ cluster sample, will be an important component of future cosmological analysesThe DES data management system is supported by the National Science Foundation under grant Nos. AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2015-71825, ESP2015-66861, FPA2015-68048, SEV2016-0588, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Unionâs Seventh Framework Program (FP7/2007-2013), including ERC grant agreements 240672, 291329, and 30647
Measuring galaxy cluster masses with CMB lensing using a Maximum Likelihood estimator: Statistical and systematic error budgets for future experiments
We develop a Maximum Likelihood estimator (MLE) to measure the masses of
galaxy clusters through the impact of gravitational lensing on the temperature
and polarization anisotropies of the cosmic microwave background (CMB). We show
that, at low noise levels in temperature, this optimal estimator outperforms
the standard quadratic estimator by a factor of two. For polarization, we show
that the Stokes Q/U maps can be used instead of the traditional E- and B-mode
maps without losing information. We test and quantify the bias in the recovered
lensing mass for a comprehensive list of potential systematic errors. Using
realistic simulations, we examine the cluster mass uncertainties from
CMB-cluster lensing as a function of an experiment's beam size and noise level.
We predict the cluster mass uncertainties will be 3 - 6% for SPT-3G, AdvACT,
and Simons Array experiments with 10,000 clusters and less than 1% for the
CMB-S4 experiment with a sample containing 100,000 clusters. The mass
constraints from CMB polarization are very sensitive to the experimental beam
size and map noise level: for a factor of three reduction in either the beam
size or noise level, the lensing signal-to-noise improves by roughly a factor
of two.Comment: 28 pages, 5 figures: figs 2, 3 updated, references added: accepted
for publication in JCA
Dissecting the Thermal SZ Power Spectrum by Halo Mass and Redshift in SPT-SZ Data and Simulations
We explore the relationship between the thermal Sunyaev-Zel'dovich (tSZ)
power spectrum amplitude and the halo mass and redshift of galaxy clusters in
South Pole Telescope (SPT) data, in comparison with three -body simulations
combined with semi-analytical gas models of the intra-cluster medium.
Specifically, we calculate both the raw and fractional power contribution to
the full tSZ power spectrum amplitude at from clusters as a
function of halo mass and redshift. We use nine mass bins in the range ,
and two redshift bins defined by and . We
additionally divide the raw power contribution in each mass bin by the number
of clusters in that bin, as a metric for comparison of different gas models. At
lower masses, the SPT data prefers a model that includes a mass-dependent bound
gas fraction component and relatively high levels of AGN feedback, whereas at
higher masses there is a preference for a model with a lower amount of feedback
and a complete lack of non-thermal pressure support. The former provides the
best fit to the data overall, in regards to all metrics for comparison. Still,
discrepancies exist and the data notably exhibits a steep mass-dependence which
all of the simulations fail to reproduce. This suggests the need for additional
mass- and redshift-dependent adjustments to the gas models of each simulation,
or the potential presence of contamination in the data at halo masses below the
detection threshold of SPT-SZ. Furthermore, the data does not demonstrate
significant redshift evolution in the per-cluster tSZ power spectrum
contribution, in contrast to most model predictions
Galaxy Clusters Discovered via the Sunyaev-Zel'dovich Effect in the 2500-Square-Degree SPT-SZ Survey
We present a catalog of galaxy clusters selected via their Sunyaev-Zel'dovich (SZ) effect signature from 2500 deg^2 of South Pole Telescope (SPT) data. This work represents the complete sample of clusters detected at high significance in the 2500 deg^2 SPT-SZ survey, which was completed in 2011. A total of 677 (409) cluster candidates are identified above a signal-to-noise threshold of Ο = 4.5 (5.0). Ground- and space-based optical and near-infrared (NIR) imaging confirms overdensities of similarly colored galaxies in the direction of 516 (or 76%) of the Ο > 4.5 candidates and 387 (or 95%) of the Ο > 5 candidates; the measured purity is consistent with expectations from simulations. Of these confirmed clusters, 415 were first identified in SPT data, including 251 new discoveries reported in this work. We estimate photometric redshifts for all candidates with identified optical and/or NIR counterparts; we additionally report redshifts derived from spectroscopic observations for 141 of these systems. The mass threshold of the catalog is roughly independent of redshift above z ~ 0.25 leading to a sample of massive clusters that extends to high redshift. The median mass of the sample is M_(500c(Ïcrit)) ~ 3.5 x 10^(14)M_â h_(70)^(-1), the median redshift is z_(med) = 0.55, and the highest-redshift systems are at z > 1.4. The combination of large redshift extent, clean selection, and high typical mass makes this cluster sample of particular interest for cosmological analyses and studies of cluster formation and evolution
Core Mass Estimates in Strong Lensing Galaxy Clusters Using a Single-halo Lens Model
The core mass of galaxy clusters is an important probe of structure formation. Here we evaluate the use of a singlehalo model (SHM) as an efficient method to estimate the strong lensing cluster core mass, testing it with ray-traced images from the Outer Rim simulation. Unlike detailed lens models, the SHM represents the cluster mass distribution with a single halo and can be automatically generated from the measured lensing constraints. We find that the projected core mass estimated with this method, MSHM, has a scatter of 8.52% and a bias of 0.90% compared to the âtrueâ mass within the same aperture. Our analysis shows no systematic correlation between the scatter or bias and the lens-source system properties. The bias and scatter can be reduced to 3.26% and 0.34%, respectively, by excluding models that fail a visual inspection test. We find that the SHM success depends on the lensing geometry, with single giant arc configurations accounting for most of the failed cases due to their limiting constraining power. When excluding such cases, we measure a scatter and bias of 3.88% and 0.84%, respectively. Finally, we find that when the source redshift is unknown, the model-predicted redshifts are overestimated, and the MSHM is underestimated by a few percent, highlighting the importance of securing spectroscopic redshifts of background sources. Our analysis provides a quantitative characterization of MSHM, enabling its efficient use as a tool to estimate the strong lensing cluster core masses in the large samples, expected from current and future surveys
Strong Lensing Model of SPT-CLJ0356-5337, a Major Merger Candidate at Redshift 1.0359
We present an analysis of the mass distribution inferred from strong lensing
by SPT-CL J0356-5337, a cluster of galaxies at redshift z = 1.0359 revealed in
the follow-up of the SPT-SZ clusters. The cluster has an Einstein radius of
Erad=14 for a source at z = 3 and a mass within 500 kpc of M_500kpc =
4.0+-0.8x10^14Msol. Our spectroscopic identification of three multiply-imaged
systems (z = 2.363, z = 2.364, and z = 3.048), combined with HST F606W-band
imaging allows us to build a strong lensing model for this cluster with an rms
of <0.3'' between the predicted and measured positions of the multiple images.
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 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.Comment: 19 pages, 11 figures. Submitted to Ap
Modeling the Galaxy Distribution in Clusters using Halo Cores
The galaxy distribution in dark matter-dominated halos is expected to
approximately trace the details of the underlying dark matter substructure. In
this paper we introduce halo `core-tracking' as a way to efficiently follow the
small-scale substructure in cosmological simulations and apply the technique to
model the galaxy distribution in observed clusters. The method relies on
explicitly tracking the set of particles identified as belonging to a halo's
central density core, once a halo has attained a certain threshold mass. The
halo cores are then followed throughout the entire evolution of the simulation.
The aim of core-tracking is to simplify substructure analysis tasks by avoiding
the use of subhalos and, at the same time, to more easily account for the
so-called ``orphan'' galaxies, which have lost substantial dark mass due to
tidal stripping. We show that simple models based on halo cores can reproduce
the number and spatial distribution of galaxies found in optically-selected
clusters in the Sloan Digital Sky Survey. We also discuss future applications
of the core-tracking methodology in studying the galaxy-halo connection.Comment: 17 pages, 20 figures, 1 Appendix; version accepted by OJ
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