Program: GN-2014B-Q-97

We have a tantalising but tentative detection of the weak lensing signal from a single, isolated, intermediate mass (log M* ~ 10) galaxy at low redshift (z ~ 0.06). This unprecedented result comes from a fundamentally new approach to exploiting weak gravitational lensing, based on anaylsis of the velocity field of a background source. In this case, the background source is a log M* ~ 10.7 disk galaxy at z ~ 0.1. Based on available SPIRAL data, we appear to have a marginal detection of the lensing signal, at the 3.5-5.0 sigma level. But we remain concerned that issues with the available SPIRAL data may be influencing this result. In order to confirm and consolidate this exciting result, we propose to use the GMOS IFU to map the stellar and gas velocity fields for this background source, as well as the stellar velocity field for the lens itself. These data will allow us to constrain not only the mass of the dark matter halo, but also its overall shape. This would represent the first direct weak lensing measurements of the distribution of dark matter at large radii (8-20 Re) around a single, isolated, intermediate mass galaxy.