PI: Ian Dell'Antonio, Brown University, email@example.com
Address: Physics Department, Box 1843, Brown University, Providence, Rhode Island 02912, USA
CoI: Richard Cook, Brown University
CoI: Hossein Khiabanian, Brown University
CoI: Jeffrey Kubo, Fermilab
Title: The low weak lensing mass of A781 peak four--physics or systematics?
Abstract: The Deep Lens Survey (DLS) has produced a sample of lensing-selected clusters; however, it is important to study the systematic incompleteness of such a sample. In one of the DLS fields, we have also obtained x-ray imaging with XMM-Newton and Chandra. In addition, a spectroscopic survey complete to R=20.5 has been carried out in this field from the SHELS collaboration (Geller \it et al. 2005). In the course of these studies, we have identified a cluster of galaxies that is strongly detected in both the XMM-Newton data and the redshift survey, but which is not significantly detected in the DLS weak lensing data. Although there have long been claims in the literature for clusters of galaxies with abnormally large M/L ratios-``dark clusters" (e.g. Erben \it et al. 2000), there has not been much study of abnormally low weak lensing signal systems. If these turn out to be real, this would have significant consequences for weak lensing-based studies of the cluster mass function. For this reason, it is vital to verify that the measurement is robust. We propose an experiment that will resolve whether the PSF reconstruction errors and/or the intrinsic ellipticities in the background galaxies resolved by the DLS could account for the discrepancy.
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