0 Assigned ID: 1188 ----- Attempting Submission 1 (Thu Feb 28 02:44:17 GMT 2013) ----- HST Phase I Proposal 1188 (cyc21.apt) successfully submitted. ----- Attempting Submission 2 (Fri Mar 01 22:44:04 GMT 2013) ----- ----- Attempting Submission 3 (Fri Mar 01 22:59:17 GMT 2013) ----- HST Phase I Proposal 1188 (cyc21.apt) successfully submitted. ----- Attempting Submission 4 (Sat Mar 02 00:57:43 GMT 2013) ----- While it is well established that clusters of galaxies reside in dark matter haloes, simulations lead us to believe that there is substantial residual dark matter substructure in those halos. Weak gravitational lensing is well suited to to studying the large scale properties of these halos but less so for studying substructure. Gravitational lensing flexion, the next-higher order lensing effect after shear, is extremely well-suited to measuring substructure, both because it acts at shorter range and because fewer background objects are needed to get a significant signal. We propose to apply a gravitational lensing analysis and mass reconstruction particularly suited to detecting substructure to a sample of 20 massive galaxy clusters, complementing strong lensing and weak lensing measurements with flexion in the mass reconstructions. Because flexion is a sensitive probe of mass gradients, we will detect structure on smaller spatial scales than are accessible to shear analyses, and will do so over a larger area than is possible with strong lensing analyses alone. Our strong+weak+flexion lensing approach will make a census of substructures down to M~3x10^12 solar masses over an entire HST/ACS field of view. Using our detailed mapping of the cluster mass distributions we will measure the normalization of the subhalo mass function (which is equivalent to the substructure mass fraction) to 10% error, and place an empirical constraint on its slope as well. COSMOLOGY Default Medium false false false false false SUPPORTED