CLASH-VLT: spectroscopic confirmation of a z = 6.11 quintuply lensed galaxy in the Frontier Fields cluster RXC J2248.7-4431^⋆

¹ INAF Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
e-mail: italobale@gmail.com
² INAF Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
³ INAF Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁴ Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, via Saragat 1, 44122 Ferrara, Italy
⁵ University Observatory Munich, Scheinerstrasse 1, 81679 München, Germany
⁶ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
⁷ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁸ INAF/IASF-Milano, via Bassini 15, 20133 Milano, Italy
⁹ INAF Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
¹⁰ Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, Giessenbachstr., 85741 Garching, Germany
¹¹ Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
¹² University of Vienna, Department of Astrophysics, Türkenschanzstr. 17, 1180 Wien, Austria
¹³ Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany
¹⁴ Dipartimento di Fisica, Università degli Studi di Trieste, via Tiepolo 11, 34143 Trieste, Italy
¹⁵ Instituto de Astrofísica de Andalucía (CSIC), C/Camino Bajo de Huétor 24, 18008 Granada, Spain
¹⁶ Department of Theoretical Physics, University of the Basque Country, PO Box 644, 48080 Bilbao, Spain
¹⁷ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
¹⁸ Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
¹⁹ Observatories of the Carnegie Institution of Washington, Pasadena, CA 91 101, USA
²⁰ INFN Bologna, via Ranzani 1, 40127 Bologna, Italy
²¹ Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milan, Italy
²² Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
²³ Institut de Ciències de l’Espai (IEEC-CSIC), 08193 Bellaterra ( Barcelona), Spain
²⁴ Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, V. Mackenna 4860, 22 Santiago, Chile
²⁵ Department of Physics, The Ohio State University, Columbus, OH, USA
²⁶ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr, Pasadena, CA 91109, USA
²⁷ Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, 10617 Taipei, Taiwan

Received: 6 September 2013
Accepted: 17 October 2013

Abstract

We present VIsible Multi-Object Spectrograph (VIMOS) observations of a galaxy quintuply imaged by the Frontier Fields galaxy cluster RXC J2248.7-4431 . This sub-, high- galaxy has been recently discovered by Monna et al. (2013) using dropout techniques with the 16-band HST photometry acquired as part of the Cluster Lensing And Supernova survey with Hubble (CLASH). Obtained as part of the CLASH-VLT survey, the VIMOS medium-resolution spectra of this source show a very faint continuum between 8700 Å and 9300 Å and a prominent emission line at 8643 , which can be readily identified with Lyman- at . The emission line exhibits an asymmetric profile, with a more pronounced red wing. The rest-frame equivalent width of the line is , relatively well constrained thanks to the detection of the UV continuum, which is rarely achieved for a sub- galaxy at this redshift. After correcting formagnification, the star formation rate (SFR) estimated from the Ly line is SFRLyyr and that estimated from the UV data is SFRUVyr. We estimate that the effective radius of the source is kpc, which implies a star formation surface mass density yrkpc and, using the Kennicutt-Schmidt relation, a gas surface mass density pc. Our results support the idea that this magnified, distant galaxy is a young and compact object with luminosity at , when the Universe was just 1 Gyr old, with a similar amount of mass in gas and stars. In the spirit of the Frontier Fields initiative, we also publish the redshifts of several multiply imaged sources and other background objects, which will help improving the strong-lensing model of this galaxy cluster.