HSTImages of the Extremely Clumpy Radio Galaxy 1138−262 atz= 2.2

Abstract
We present and discuss optical continuum images made with the Hubble Space Telescope of the radio galaxy 1138-262 at z = 2.2. This object possesses one of the clumpiest optical morphologies of all known high-redshift radio galaxies, consisting of a bright nucleus aligned along the radio axis and a number of smaller components distributed over a region as large as the radio source (130 kpc). The clumps have sizes ranging from 3 to 13 kpc and absolute visual magnitudes between MV = -21.8 and MV = -19.4. On the basis of HST and previous observations, we claim that these clumps are star-forming galaxies that will be accreted by the host galaxy of 1138-262. We compare this radio galaxy with other high-redshift objects and with the predictions of current scenarios of galaxy formation.

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