Letter to the Editor

ISAAC/VLT observations of a lensed galaxy at z = 10.0^*

¹ Laboratoire d'Astrophysique, UMR 5572, Observatoire Midi-Pyrénées, 14 Avenue E. Belin, 31400 Toulouse, France
² Observatoire de Genève, 51, Ch. des Maillettes, 1290 Sauverny, Switzerland
³ Caltech Astronomy, MC105-24, Pasadena, CA 91125, USA

Corresponding author: R. Pelló, roser@ast.obs-mip.fr

Received: 20 January 2004
Accepted: 13 February 2004

Abstract

We report the first likely spectroscopic confirmation of a  galaxy from our ongoing search for distant galaxies with ISAAC/VLT. Galaxy candidates at  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 when identified as Lyα, in excellent agreement with the photometric redshift determination. Redshifts are very unlikely for various reasons we discuss. The object is located on the critical lines corresponding to  to 11. The magnification factor μ ranges from 25 to 100. For this object we estimate  yr^-1 and  yr^-1, 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 ) a lensing corrected stellar mass of , and luminosities of , corresponding to a dark matter halo of a mass of typically . 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 8-10 m class telescopes.