2004A&A...416L..35P

We report the first likely spectroscopic confirmation of a z∼10.0 galaxy from our ongoing search for distant galaxies with ISAAC/VLT. Galaxy candidates at z>7 are selected from ultra-deep JHKs images in the core of gravitational lensing clusters for which deep optical imaging is also available, including HST data. The object reported here, found behind Abell 1835, exhibits a faint emission line detected in the J band, leading to z=10.0 when identified as Lyα, in excellent agreement with the photometric redshift determination. Redshifts z<7 are very unlikely for various reasons we discuss. The object is located on the critical lines corresponding to z=9 to 11. The magnification factor µ ranges from 25 to 100. For this object we estimate SFR(Lyα)~(0.8-2.2)M _☉/yr and SFR(UV)~(47-75)M _☉/yr, both uncorrected for lensing. The steep UV slope indicates a young object with negligible dust extinction. SED fits with young low-metallicity stellar population models yield (adopting µ=25) a lensing corrected stellar mass of M_*∼8x10⁶M _☉, and luminosities of 2x10¹⁰L _☉, corresponding to a dark matter halo of a mass of typically M_tot>5x10⁸M _☉. In general our observations show that under excellent conditions and using strong gravitational lensing direct observations of galaxies close to the ``dark ages'' are feasible with ground-based 8-10m class telescopes.