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

R. Pelló; D. Schaerer; J. Richard; J.-F. Le Borgne; J.-P. Kneib

doi:doi:10.1051/0004-6361:20040065

Free access

Issue		A&A Volume 416, Number 3, March IV 2004


Page(s)		L35 - L40
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:20040065

A&A 416, L35-L40 (2004)
DOI: 10.1051/0004-6361:20040065

Letter

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

R. Pelló¹, D. Schaerer^{2, 1}, J. Richard¹, J.-F. Le Borgne¹ and J.-P. Kneib^{3, 1}

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

(Received 20 January 2004 / Accepted 13 February 2004)

Abstract
We report the first likely spectroscopic confirmation of a $z\sim 10.0$ galaxy from our ongoing search for distant galaxies with ISAAC/VLT. Galaxy candidates at $z \ga 7$ 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 Ly $\alpha$ , 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 $\mu$ ranges from 25 to 100. For this object we estimate ${\it SFR}({\rm Ly}\alpha) \sim (0.8{-}2.2)~M _{\odot}$ yr ^-1 and ${\it SFR}({\rm UV}) \sim (47{-}75)~M _{\odot}$ 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 $\mu=25$ ) a lensing corrected stellar mass of $M_\star \sim 8 \times 10^6~M _{\odot}$ , and luminosities of $2 \times 10^{10}~L _{\odot}$ , corresponding to a dark matter halo of a mass of typically $M_{\rm tot} \ga 5 \times 10^8~M _{\odot}$ . 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.

Key words: galaxies: high-redshift -- galaxies: evolution -- galaxies: starburst -- galaxies: active -- infrared: galaxies

Offprint request: R. Pelló, roser@ast.obs-mip.fr

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