Uncertainty in the mass-observable scaling relations is currently the limiting factor for galaxy cluster based cosmology. Weak gravitational lensing can provide a direct mass calibration and reduce ...the mass uncertainty. We present new ground-based weak lensing observations of 19 South Pole Telescope (SPT) selected clusters and combine them with previously reported space-based observations of 13 galaxy clusters to constrain the cluster mass scaling relations with the Sunyaev-Zel'dovich effect (SZE), the cluster gas mass $M_\mathrm{gas}$, and $Y_\mathrm{X}$, the product of $M_\mathrm{gas}$ and X-ray temperature. We extend a previously used framework for the analysis of scaling relations and cosmological constraints obtained from SPT-selected clusters to make use of weak lensing information. Here, we introduce a new approach to estimate the effective average redshift distribution of background galaxies and quantify a number of systematic errors affecting the weak lensing modelling. These errors include a calibration of the bias incurred by fitting a Navarro-Frenk-White profile to the reduced shear using $N$-body simulations. We blind the analysis to avoid confirmation bias. We are able to limit the systematic uncertainties to 6.4% in cluster mass (68% confidence). Our constraints on the mass-X-ray observable scaling relations parameters are consistent with those obtained by earlier studies, and our constraints for the mass-SZE scaling relation are consistent with the the simulation-based prior used in the most recent SPT-SZ cosmology analysis. We can now replace the external mass calibration priors used in previous SPT-SZ cosmology studies with a direct, internal calibration obtained on the same clusters.
This is the second in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. The data set employed here consists of Chandra observations of 40 ...such clusters, identified in a comprehensive search of the Chandra archive for hot (kT ... 5 keV), massive, morphologically relaxed systems, as well as high-quality weak gravitational lensing data for a subset of these clusters. Here we present cosmological constraints from measurements of the gas mass fraction, ..., for this cluster sample. By incorporating a robust gravitational lensing calibration of the X-ray mass estimates, and restricting our measurements to the most self-similar and accurately measured regions of clusters, we significantly reduce systematic uncertainties compared to previous work. Our data for the first time constrain the intrinsic scatter in fgas, 7.4 ± 2.3 per cent in a spherical shell at radii 0.8-1.2 ... (~1/4 of the virial radius), consistent with the expected level of variation in gas depletion and non-thermal pressure for relaxed clusters. From the lowest redshift data in our sample, five clusters at z < 0.16, we obtain a constraint on a combination of the Hubble parameter and cosmic baryon fraction, ... = 0.089 ± 0.012, that is insensitive to the nature of dark energy. Combining this with standard priors on h and ... provides a tight constraint on the cosmic matter density, ... = 0.27 ± 0.04, which is similarly insensitive to dark energy. Using the entire cluster sample, extending to z > 1, we obtain consistent results for ... and interesting constraints on dark energy: ... for non-flat ...CDM (cosmological constant) models, and w = -0.98 ± 0.26 for flat models with a constant dark energy equation of state. Our results are both competitive and consistent with those from recent cosmic microwave background, Type Ia supernova and baryon acoustic oscillation data. We present constraints on more complex models of evolving dark energy from the combination of fgas data with these external data sets, and comment on the possibilities for improved fgas constraints using current and next-generation X-ray observatories and lensing data. (ProQuest: ... denotes formulae/symbols omitted.)
This paper is the second in a series in which we perform an extensive comparison of various galaxy-based cluster mass estimation techniques that utilize the positions, velocities and colours of ...galaxies. Our aim is to quantify the scatter, systematic bias and completeness of cluster masses derived from a diverse set of 25 galaxy-based methods using two contrasting mock galaxy catalogues based on a sophisticated halo occupation model and a semi-analytic model. Analysing 968 clusters, we find a wide range in the rms errors in log M
200c delivered by the different methods (0.18–1.08 dex, i.e. a factor of ∼1.5–12), with abundance-matching and richness methods providing the best results, irrespective of the input model assumptions. In addition, certain methods produce a significant number of catastrophic cases where the mass is under- or overestimated by a factor greater than 10. Given the steeply falling high-mass end of the cluster mass function, we recommend that richness- or abundance-matching-based methods are used in conjunction with these methods as a sanity check for studies selecting high-mass clusters. We see a stronger correlation of the recovered to input number of galaxies for both catalogues in comparison with the group/cluster mass, however, this does not guarantee that the correct member galaxies are being selected. We do not observe significantly higher scatter for either mock galaxy catalogues. Our results have implications for cosmological analyses that utilize the masses, richnesses, or abundances of clusters, which have different uncertainties when different methods are used.
ABSTRACT We present cosmological parameter constraints obtained from galaxy clusters identified by their Sunyaev-Zel'dovich effect signature in the 2500 square-degree South Pole Telescope Sunyaev ...Zel'dovich (SPT-SZ) survey. We consider the 377 cluster candidates identified at with a detection significance greater than five, corresponding to the 95% purity threshold for the survey. We compute constraints on cosmological models using the measured cluster abundance as a function of mass and redshift. We include additional constraints from multi-wavelength observations, including Chandra X-ray data for 82 clusters and a weak lensing-based prior on the normalization of the mass-observable scaling relations. Assuming a spatially flat ΛCDM cosmology, we combine the cluster data with a prior on H0 and find and , with the parameter combination . These results are in good agreement with constraints from the cosmic microwave background (CMB) from SPT, WMAP, and Planck, as well as with constraints from other cluster data sets. We also consider several extensions to ΛCDM, including models in which the equation of state of dark energy w, the species-summed neutrino mass, and/or the effective number of relativistic species ( ) are free parameters. When combined with constraints from the Planck CMB, H0, baryon acoustic oscillation, and SNe, adding the SPT cluster data improves the w constraint by 14%, to .
This is the fourth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Here, we use measurements of weak gravitational lensing from the ...Weighing the Giants project to calibrate Chandra X-ray measurements of total mass that rely on the assumption of hydrostatic equilibrium. This comparison of X-ray and lensing masses measures the combined bias of X-ray hydrostatic masses from both astrophysical and instrumental sources. While we cannot disentangle the two sources of bias, only the combined bias is relevant for calibrating cosmological measurements using relaxed clusters. Assuming a fixed cosmology, and within a characteristic radius (r
2500) determined from the X-ray data, we measure a lensing to X-ray mass ratio of 0.96 ± 9 per cent (stat) ± 9 per cent (sys). We find no significant trends of this ratio with mass, redshift or the morphological indicators used to select the sample. Our results imply that any departures from hydrostatic equilibrium at these radii are offset by calibration errors of comparable magnitude, with large departures of tens-of-percent unlikely. In addition, we find a mean concentration of the sample measured from lensing data of
$c_{200} = 3.0_{-1.8}^{+4.4}$
. Anticipated short-term improvements in lensing systematics, and a modest expansion of the relaxed lensing sample, can easily increase the measurement precision by 30–50 per cent, leading to similar improvements in cosmological constraints that employ X-ray hydrostatic mass estimates, such as on Ωm from the cluster gas mass fraction.
ABSTRACT We give an overview of the Grism Lens Amplified Survey from Space (GLASS), a large Hubble Space Telescope program aimed at obtaining grism spectroscopy of the fields of 10 massive clusters ...of galaxies at redshift z = 0.308-0.686, including the Hubble Frontier Fields (HFF). The Wide Field Camera 3 (WFC3) yields near-infrared spectra of the cluster cores covering the wavelength range 0.81-1.69 m through grisms G102 and G141, while the Advanced Camera for Surveys in parallel mode provides G800L spectra of the infall regions of the clusters. The WFC3 spectra are taken at two almost orthogonal position angles in order to minimize the effects of confusion. After summarizing the scientific drivers of GLASS, we describe the sample selection as well as the observing strategy and data processing pipeline. We then utilize MACS J0717.5+3745, a HFF cluster and the first one observed by GLASS, to illustrate the data quality and the high-level data products. Each spectrum brighter than is visually inspected by at least two co-authors and a redshift is measured when sufficient information is present in the spectra. Furthermore, we conducted a thorough search for emission lines through all of the GLASS WFC3 spectra with the aim of measuring redshifts for sources with continuum fainter than We provide a catalog of 139 emission-line-based spectroscopic redshifts for extragalactic sources, including three new redshifts of multiple image systems (one probable, two tentative). In addition to the data itself, we also release software tools that are helpful to navigate the data.
The nature and origin of the cold interstellar medium (ISM) in early-type galaxies are still a matter of debate, and understanding the role of this component in galaxy evolution and in fuelling the ...central supermassive black holes requires more observational constraints. Here, we present a multiwavelength study of the ISM in eight nearby, X-ray and optically bright, giant elliptical galaxies, all central dominant members of relatively low-mass groups. Using far-infrared spectral imaging with the Herschel Photodetector Array Camera & Spectrometer, we map the emission of cold gas in the cooling lines of C iiλ157 μm, O i λ63 μm and O ib λ145 μm. Additionally, we present Hα+N ii imaging of warm ionized gas with the Southern Astrophysical Research (SOAR) telescope, and a study of the thermodynamic structure of the hot X-ray emitting plasma with Chandra. All systems with extended Hα emission in our sample (6/8 galaxies) display significant C ii line emission indicating the presence of reservoirs of cold gas. This emission is cospatial with the optical Hα+N ii emitting nebulae and the lowest entropy soft X-ray emitting plasma. The entropy profiles of the hot galactic atmospheres show a clear dichotomy, with the systems displaying extended emission-line nebulae having lower entropies beyond r 1 kpc than the cold-gas-poor systems. We show that while the hot atmospheres of the cold-gas-poor galaxies are thermally stable outside of their innermost cores, the atmospheres of the cold-gas-rich systems are prone to cooling instabilities. This provides considerable weight to the argument that cold gas in giant ellipticals is produced chiefly by cooling from the hot phase. We show that cooling instabilities may develop more easily in rotating systems and discuss an alternative condition for thermal instability for this case. The hot atmospheres of cold-gas-rich galaxies display disturbed morphologies indicating that the accretion of clumpy multiphase gas in these systems may result in variable power output of the AGN jets, potentially triggering sporadic, larger outbursts. In the two cold-gas-poor, X-ray morphologically relaxed galaxies of our sample, NGC 1399 and NGC 4472, powerful AGN outbursts may have destroyed or removed most of the cold gas from the cores, allowing the jets to propagate and deposit most of their energy further out, increasing the entropy of the hot galactic atmospheres and leaving their cores relatively undisturbed.
The primary difficulty in measuring dynamical masses of galaxy clusters from galaxy data lies in the separation between true cluster members from interloping galaxies along the line of sight. We ...study the impact of membership contamination and incompleteness on cluster mass estimates obtained with 25 commonly used techniques applied to nearly 1000 mock clusters with precise spectroscopic redshifts. We show that all methods overestimate or underestimate cluster masses when applied to contaminated or incomplete galaxy samples, respectively. This appears to be the main source of the intrinsic scatter in the mass scaling relation. Applying corrections based on a prior knowledge of contamination and incompleteness can reduce the scatter to the level of shot noise expected for poorly sampled clusters. We establish an empirical model quantifying the effect of imperfect membership on cluster mass estimation and discuss its universal and method-dependent features. We find that both imperfect membership and the response of the mass estimators depend on cluster mass, effectively causing a flattening of the estimated–true mass relation. Imperfect membership thus alters cluster counts determined from spectroscopic surveys, hence the cosmological parameters that depend on such counts.
Abstract
We present an HST/Advanced Camera for Surveys (ACS) weak gravitational lensing analysis of 13 massive high-redshift (zmedian = 0.88) galaxy clusters discovered in the South Pole Telescope ...(SPT) Sunyaev–Zel'dovich Survey. This study is part of a larger campaign that aims to robustly calibrate mass–observable scaling relations over a wide range in redshift to enable improved cosmological constraints from the SPT cluster sample. We introduce new strategies to ensure that systematics in the lensing analysis do not degrade constraints on cluster scaling relations significantly. First, we efficiently remove cluster members from the source sample by selecting very blue galaxies in V − I colour. Our estimate of the source redshift distribution is based on Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) data, where we carefully mimic the source selection criteria of the cluster fields. We apply a statistical correction for systematic photometric redshift errors as derived from Hubble Ultra Deep Field data and verified through spatial cross-correlations. We account for the impact of lensing magnification on the source redshift distribution, finding that this is particularly relevant for shallower surveys. Finally, we account for biases in the mass modelling caused by miscentring and uncertainties in the concentration–mass relation using simulations. In combination with temperature estimates from Chandra
we constrain the normalization of the mass–temperature scaling relation ln (E(z)M500c/1014 M⊙) = A + 1.5ln (kT/7.2 keV) to $A=1.81^{+0.24}_{-0.14}(\mathrm{stat.})\,{\pm }\,0.09(\mathrm{sys.})$, consistent with self-similar redshift evolution when compared to lower redshift samples. Additionally, the lensing data constrain the average concentration of the clusters to $c_\mathrm{200c}=5.6^{+3.7}_{-1.8}$.
ABSTRACT In Hubble Space Telescope (HST) imaging taken on 2014 November 10, four images of supernova (SN) "Refsdal" (redshift z = 1.49) appeared in an Einstein-cross-like configuration (images S1-S4) ...around an early-type galaxy in the cluster MACS J1149.5+2223 (z = 0.54). Almost all lens models of the cluster have predicted that the SN should reappear within a year in a second host-galaxy image created by the cluster's potential. In HST observations taken on 2015 December 11, we find a new source at the predicted position of the new image of SN Refsdal approximately from the previous images S1-S4. This marks the first time the appearance of a SN at a particular time and location in the sky was successfully predicted in advance! We use these data and the light curve from the first four observed images of SN Refsdal to place constraints on the relative time delay and magnification of the new image (SX) compared to images S1-S4. This enables us, for the first time, to test "blind" lens model predictions of both magnifications and time delays for a lensed SN. We find that the timing and brightness of the new image are consistent with the blind predictions of a fraction of the models. The reappearance illustrates the discriminatory power of this blind test and its utility to uncover sources of systematic uncertainty. From planned HST photometry, we expect to reach a precision of 1%-2% on the time delay between S1-S4 and SX.