Fabian Walter, R. Decarli, C. Carilli, F. Bertoldi, P. Cox, E. Da Cunha, E. Daddi, M. Dickinson, D. Downes, D. Elbaz, R. Ellis, J. Hodge, R. Neri, D. Riechers, A. Weiss, E. Bell, H. Dannerbauer, M. Krips, M. Krumholz, L. Lentati, R. Maiolino, K. Menten, H. -W. Rix, B. Robertson, H. Spinrad, D. Stark, D. Stern
The Hubble Deep Field (HDF) is a region in the sky that provides one of the deepest multi-wavelength views of the distant universe and has led to the detection of thousands of galaxies seen throughout cosmic time. An early map of the HDF at a wavelength of 850 microns that is sensitive to dust emission powered by star formation revealed the brightest source in the field, dubbed HDF850.1. For more than a decade, this source remained elusive and, despite significant efforts, no counterpart at shorter wavelengths, and thus no redshift, size or mass, could be identified. Here we report, using a millimeter wave molecular line scan, an unambiguous redshift determination for HDF850.1 of z=5.183. This places HDF850.1 in a galaxy overdensity at z~5.2 in the HDF, corresponding to a cosmic age of only 1.1 Gyr after the Big Bang. This redshift is significantly higher than earlier estimates and higher than most of the >100 sub-millimeter bright galaxies identified to date. The source has a star formation rate of 850 M_sun/yr and is spatially resolved on scales of 5 kpc, with an implied dynamical mass of ~1.3x10^11 M_sun, a significant fraction of which is present in the form of molecular gas. Despite our accurate redshift and position, a counterpart arising from starlight remains elusive.
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http://arxiv.org/abs/1206.2641
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