Central Image Searches in Five Gravitational Lenses

Central images in gravitational lenses probe the matter profiles in the inner 100 pc of the lens galaxies, providing information on galactic structure at cosmological distances (z ∼ 0.5). We present Very Long Baseline Array and High Sensitivity Array observations of J1838-3427, B0739+366, B1152+199, B0445+123 and B0850+054: 5 gravitational lenses that are good central image candidates. We model the mass profiles of the lens galaxies, finding that the limits on the central image flux densities imply near-isothermal central profiles. Galaxy centers are steeper than pure dark matter haloes.

This work was partly supported by National Science Foundation grant AST 00-71181. Work by E. R. B. was partly supported by the pre-doctoral fellowship program of the National Radio Astronomy Observatory, a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Work by J. N. W. was supported by NASA through Hubble Fellowship grant HST-HF-01180.02-A, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555.