Weak Lensing Analysis of Cl 1358+62 UsingHubble Space TelescopeObservations

Abstract

We report on the detection of weak gravitational lensing of faint, distant background objects by Cl 1358]62, a rich cluster of galaxies at a redshift of z \ 0.33. The observations consist of a large, multicolor mosaic of Hubble Space T elescope WFPC2 images. The number density of approximately 50 background objects arcmin~2 allows us to do a detailed weak lensing analysis of this cluster. We detect a weak lensing signal out toD1.5 Mpc from the cluster center. The observed distortion is consistent with a singular isothermal sphere model with a velocity dispersion of 780^50 km s~1. The total projected mass within a radius of 1 Mpc corresponding to this model is (4.4^0.6) ] 1014The errors given M _ . here represent the random error due to the ellipticities of the background galaxies. The uncertainty in the redshift distribution introduces an additional systematic error of D10% in the weak lensing mass. The weak lensing mass is slightly lower than dynamical estimates and agrees well with X-ray mass estimates. The mass distribution is elongated in a similar way as the light. The axis ratio of 0.30^0.15 and position angle of [21¡^7¡ were measured directly from the observations and agree very well with a previous strong lensing determination. A two-dimensional reconstruction of the cluster mass surface density shows that the peak of the mass distribution coincides with the peak of the light distribution. We Ðnd a value of for the mass-to-light ratio, consistent with being constant with (90^13)h 50 M _ L V_ 1 radius. The point-spread function of HST is highly anisotropic at the edges of the individual chips. This systematically perturbs the shapes of objects, and we present a method for applying the appropriate correction.

Observational probes of cosmic acceleration

“…The prototype moments-based method was that of Kaiser, Squires, and Broadhurst (KSB;Kaiser et al 1995; improved by Luppino and Kaiser 1997;Hoekstra et al 1998). Many improvements of these methods have been made -e.g., in computing better conversion factors from shear to quadrupole moments 50 (Semboloni et al, 2006b).…”

Evidence of the accelerated expansion of the Universe from weak lensing tomography with COSMOS

“…For the latter, we use the KSB+ formalism (Kaiser et al 1995;Luppino & Kaiser 1997;Hoekstra et al 1998), see Erben et al (2001), Schrabback et al (2007) and Appendix B.1 for details on our implementation. As found with simulations of ground-based weak lensing data, KSB+ can significantly underestimate gravitational shear (Erben et al 2001;Bacon et al 2001;Heymans et al 2006a;Massey et al 2007a), where the calibration bias m and possible PSF anisotropy residuals c, defined via…”

“…We measure galaxy shapes using the Erben et al (2001) implementation of the KSB+ formalism (Kaiser et al 1995;Luppino & Kaiser 1997;Hoekstra et al 1998), as done in the earlier ACS weak lensing analysis of Schrabback et al (2007). Object ellipticities 16 e = e 1 + ie 2 = Q 11 − Q 22 + 2iQ 12 Q 11 + Q 22 (B.1) are measured from weighted second-order brightness moments…”

Planckintermediate results

“…Thirdly, the weak lensing distortion measurements of Okabe & Umetsu (2008) and Okabe et al (2010) are based on an implementation of the KSB+ method (Kaiser et al 1995;Luppino & Kaiser 1997;Hoekstra et al 1998). Tests against simulated lensing data (Heymans et al 2006;Massey et al 2007) indicate that this method is generally affected by a multiplicative calibration bias, underestimating the true lensing signal by up to 15 percent, depending on details in the implementation of the method.…”