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Session 7 - Microlensing.
Display session, Monday, June 08
1. Hogg et al (1997) used the incidence of gravitationally lensed radio sources to predict that several clear examples of multiple-imaged galaxies would be found on the Hubble Deep Field. To date, there are no compelling cases. Using a different approach, we use the known redshifts of the brighter galaxies to argue that this is actually consistent with the estimated optical depth to lensing, which is dominated by a few elliptical galaxies. It is suggested that most observed, strong lenses are found in comparatively rare, compact groups.
2. Weak, galaxy-galaxy lensing can be used to analyze the redshift distribution of galaxies far too faint for direct spectroscopy. This technique is described and applied to the measured image ellipticities on the Hubble Deep Field. It is shown that there is a significant lensing signal, consistent with a faint galaxy redshift distribution extending from low to high redshift.
Program listing for Monday