Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userWeak Gravitational Lensing by a Sample of X-Ray Luminous Clusters of Galaxies -- II. Comparison with Virial Masses
65
0
0.0
(
0
)
Authors
Ragnvald J. Irgens
Ask ChatGPT about the research
No Arabic abstract
Dynamic velocity dispersion and mass estimates are given for a sample of five X-ray luminous rich clusters of galaxies at intermediate redshifts (z~0.3) drawn from a sample of 39 clusters for which we have obtained gravitational lens mass estimates. The velocity dispersions are determined from between 9 and 20 redshifts measured with the LDSS spectrograph of the William Herschel Telescope, and virial radii are determined from imaging using the UH8K mosaic CCD camera on the University of Hawaii 2.24m telescope. Including clusters with velocity dispersions taken from the literature, we have velocity dispersion estimates for 12 clusters in our gravitational lensing sample. For this sample we compare the dynamical velocity dispersion estimates with our estimates of the velocity dispersions made from gravitational lensing by fitting a singular isothermal sphere profile to the observed tangential weak lensing distortion as a function of radius. In all but two clusters, we find a good agreement between the velocity dispersion estimates based on spectroscopy and on weak lensing.
rate research
Read More
Gravitational lensing by clusters of galaxies affects the cosmic X-ray background (XRB) by altering the observed density and flux distribution of background X-ray sources. At faint detection flux thresholds, the resolved X-ray sources appear brighter and diluted, while the unresolved component of the XRB appears dimmer and more anisotropic, due to lensing. The diffuse X-ray intensity in the outer halos of clusters might be lower than the sky-averaged XRB, after the subtraction of resolved sources. Detection of the lensing signal with a wide-field X-ray telescope could probe the mass distribution of a cluster out to its virialization boundary. In particular, we show that the lensing signature imprinted on the resolved component of the XRB by the cluster A1689, should be difficult but possible to detect out to 8 at the 2-4 sigma level, after 10^6 seconds of observation with the forthcoming AXAF satellite. The lensing signal is fairly insensitive to the lens redshift in the range 0.1<z<0.6. The amplitude of the lensing signal is however sensitive to the faint end slope of the number-flux relation for unresolved X-ray sources, and can thus help constrain models of the XRB. A search for X-ray arcs or arclets could identify the fraction of all faint sources which originate from extended emission of distant galaxies. The probability for a 3 sigma detection of an arclet which is stretched by a factor of about 3 after a 10^6 seconds observation of A1689 with AXAF, is roughly comparable to the fraction of all background X-ray sources that have an intrinsic size of order 1.
In the standard model of non-linear structure formation, a cosmic web of dark-matter dominated filaments connects dark matter halos. In this paper, we stack the weak lensing signal of an ensemble of filaments between groups and clusters of galaxies. Specifically, we detect the weak lensing signal, using CFHTLenS galaxy ellipticities, from stacked filaments between SDSS-III/BOSS luminous red galaxies (LRGs). As a control, we compare the physical LRG pairs with projected LRG pairs that are more widely separated in redshift space. We detect the excess filament mass density in the projected pairs at the $5sigma$ level, finding a mass of $(1.6 pm 0.3) times 10^{13} M_{odot}$ for a stacked filament region 7.1 $h^{-1}$ Mpc long and 2.5 $h^{-1}$ Mpc wide. This filament signal is compared with a model based on the three-point galaxy-galaxy-convergence correlation function, as developed in Clampitt, Jain & Takada (2014), yielding reasonable agreement.
Aims: We present a wide-field multi-color survey of a homogeneous sample of eleven clusters of galaxies for which we measure total masses and mass distributions from weak lensing. Methods: The eleven clusters in our sample are all X-ray luminous and span a narrow redshift range at z=0.21 +/- 0.04. The weak lensing analysis of the sample is based on ground-based wide-field imaging obtained with the CFH12k camera on CFHT. We use the methodology developed and applied previously on the massive cluster Abell 1689. A Bayesian method, implemented in the Im2shape software, is used to fit the shape parameters of the faint background galaxies and to correct for PSF smearing. With the present data, shear profiles are measured in all clusters out to at least 2 Mpc (more than 15arcmin from the center) with high confidence. The radial shear profiles are fitted with different parametric mass profiles and the virial mass M_200 is estimated for each cluster and then compared to other physical properties. Results: Scaling relations between mass and optical luminosity indicate an increase of the M/L ratio with luminosity and a L_X-M_200 relation scaling as L_X propto M_200^(0.83 +/- 0.11) while the normalization of the M_200 propto T_X^{3/2} relation is close to the one expected from hydrodynamical simulations of cluster formation as well as previous X-ray analyses. We suggest that the dispersion in the M_200-T_X and M_200-L_X relations reflects the different merging and dynamical histories for clusters of similar X-ray luminosities and intrinsic variations in their measured masses. Improved statistics of clusters over a wider mass range are required for a better control of the intrinsic scatter in scaling relations.
Due to the finite amount of observational data, the best-fit parameters corresponding to the reconstructed cluster mass have uncertainties. In turn, these uncertainties affect the inferences made from these mass models. Following our earlier work, we have studied the effect of such uncertainties on the singularity maps in simulated and actual galaxy clusters. The mass models for both simulated and real clusters have been constructed using grale. The final best-fit mass models created using grale give the simplest singularity maps and a lower limit on the number of point singularities that a lens has to offer. The simple nature of these singularity maps also puts a lower limit on the number of three image (tangential and radial) arcs that a cluster lens has. Hence, we estimate the number of galaxy sources giving rise to the three image arcs, which can be observed with the James Webb Space Telescope (JWST). We find that we expect to observe at least 20-30 tangential and 5-10 radial three-image arcs in the Hubble Frontier Fields cluster lenses with the JWST.
We present the first three galaxy clusters of a larger sample of the most X-ray luminous galaxy clusters selected from the ROSAT Bright Survey. This project, which is a systematic search for strong lensing, aims at arc statistics, mass determinations and studies of distant lensed galaxies. The three galaxy clusters presented here have been observed with the Wide Field Imager at the ESO2.2m in the R- and V-band. The images show lensing features like distinct distorted galaxies and arcs. Mass distributions of the lensing galaxy clusters and photometric properties of some arc candidates are presented. In addition we report the discovery of three giant arcs.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
