Singular isothermal sphere profile

Abstract: We have run two completely independent weak lensing analysis pipelines on a set of realistic simulated images of a massive galaxy cluster with a singular isothermal sphere profile (galaxy velocity dispersion sigma_v=1250 km/ sec). The suite of images was constructed using the simulation tools developed by the Dark Energy Survey. We find that both weak lensing pipelines can accurately recover the velocity dispersion of our simulated clusters, suggesting that current weak lensing tools are accurate enough for measuring the shear profile of massive clusters in upcoming large photometric surveys. We also demonstrate how choices of some cuts influence the final shear profile and sigma_v measurement. Analogously to the STEP program, we make all of these cluster simulation images publically available for other groups to analyze through their own weak lensing pipelines.

Abstract: We study the effects on the number counts of submillimetre galaxies due to gravitational lensing. We explore the effects on the magnification cross-section due to halo density profiles, ellipticity and cosmological parameter (the power-spectrum normalization sigma(8)). We show that the ellipticity does not strongly affect the magnification cross-section in gravitational lensing while the halo radial profiles do. Since the baryonic cooling effect is stronger in galaxies than clusters, galactic haloes are more concentrated. In light of this, a new scenario of two-halo-population model is explored where galaxies are modelled as a singular isothermal sphere profile and clusters as a Navarro, Frenk and White profile. We find that the transition mass between the two has modest effects on the lensing probability. The cosmological parameter sigma(8) alters the abundance of haloes and therefore affects our results. Compared with other methods, our model is simpler and more realistic. The conclusions of previous works confirm that gravitational lensing is a natural explanation for the number count excess at the bright end.

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.