Galaxy Dark Matter: Galaxy-Galaxy Lensing in the Hubble Deep Field

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Abstract
In this Letter we present calibrated observations of the average mass of galaxies with 22 < I < 25 in the Hubble Deep Field. We measure the mean mass profile using the statistical gravitational lens distortion of faint blue background galaxies, based on 2221 foreground-background pairs. The observed weak lensing distortion is calibrated via full three-dimensional simulations and other Hubble Space Telescope data on a foreground cluster of known mass. Inside a projected radius of 5'' we find a 3 σ detection of shear. Fitting to an isothermal mass distribution, we find a distortion of 0.066+ 0.018−0.019 at a radius of 2'' (~8 h-1 kpc). The (1σ) limits on the parameters for the truncated isothermal model are σ = 185+ 30−35 km s-1, router ≥ 15 h-1 kpc, and rcore = 0.6+ 1.3−0.6 h-1 kpc. This corresponds to an average galaxy mass interior to 20 h-1 kpc of 5.9+ 2.5−2.7 × 1011 h-1 M☉. Inside 10 h-1 kpc, we find an average rest-frame V-band mass-to-light ratio of 11.4+ 6.0−6.7 h (M/LV)☉.
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