Wide-field Weak Lensing Mass Reconstructions of Merging Galaxy Clusters

1. Introduction Abell 1758 Wide-field Weak Lensing Mass Reconstructions of Merging Galaxy Clusters Brett Ragozzine, Douglas Clowe Ohio University, Department of Physics & Astronomy, Athens, OH 45701 • Current cosmological models show that baryonic matter comprises 4.5% of the total mass distribution of the universe and that dark matter comprises 23%. Thus the dark matter component is approximately 5 times more abundant than baryonic matter. • Alternative gravity models have been proposed which replace the need for dark matter with gravity being stronger than Newtonian on Mpc scales. • Dark matter follows the distribution of baryonic matter in the universe. In order to test its existence, the dark matter component must be separated from the baryonic component. • Galaxy clusters are permeated by x-ray gas, which outweighs the remaining baryonic matter by a factor of 10. By showing the offset of the cluster’s gravitational potential from the x-ray plasma, one can infer the existence of dark matter. • Merging clusters provide a unique view where the dark matter component is separated from x-ray gas. X-ray gas is slowed through ram pressure while the galaxies themselves move nearly uninterrupted. • Weak lensing reveals the total mass distribution. comparing the x-ray gas distribution with the mass reconstruction of weak lensing reveals an x-ray gas offset from the dominant mass doing the lensing. • It has been previously shown that merging clusters have a baryonic mass distribution that is offset from the majority of the mass in the lens. • Results are needed from additional merging clusters to avoid conspiracy models. • Data taken with Subaru Suprime Cam in April 2008. Images included exposures in B (30 minutes) and V (80 minutes). • Mass contours are aligned with the Brightest Cluster Galaxies of the merging components. • This weak lensing analysis on Abell 1758 was performed using the KSB method. The preliminary results are as follows. • X-ray contours are offset from one of the merging cluster components.     Figure 2. Abell 1758, the northeastern cluster’s dark matter component follows the optical component more closely than does the x-ray gas in Figure 3. The gray-scale image is the 80-minute V band Subaru exposure. The blue contours are the  reconstruction coming from 24,774 galaxies (33.2 galaxies per sq arcmin), outer contour is 0.03 and increasing in steps of 0.02. Figure 3. Abell 1758, contours follow the x-ray gas distribution. The gray-scale image is from the DSS. The x-ray contours are from a 58 ksec XMM exposure. The northern cluster is an ongoing merger between two 7 keV clusters, the southern cluster is an ongoing merger between two 5 keV clusters (from David and Kempner, 2004). Both figures cover an area of 16’ x 15’ (4.07 x 3.82 Mpc at z=0.279). Figure 1. Bullet Cluster (Clowe et al, 2006). Colors follow x-ray gas. Green contours follow mass component. This work is funded in part by Space Telescope Science Institute, AURA, grant HST-GO-11194.01-A.