Letter to the Editor

Discovery of six Lyα emitters near a radio galaxy at z ~ 5.2^*

¹ Sterrewacht Leiden, PO Box 9513, 2300 RA, Leiden, The Netherlands e-mail: venemans@strw.leidenuniv.nl
² European Southern Observatory, Karl Schwarzschild Straße 2, 85748 Garching, Germany
³ INAF Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125, Firenze, Italy
⁴ Lawrence Livermore National Laboratory, PO Box 808, Livermore CA, 94550, USA
⁵ National Radio Astronomy Observatory, PO Box 0, Socorro, NM 87801, USA
⁶ Dept. of Physics & Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore MD, 21218–2686, USA
⁷ The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena CA, 91101, USA
⁸ Dipartimento di Fisica, Università degli studi Roma Tre, via della Vasca Navale 84, Roma, 00146, Italy

Received: 10 May 2004
Accepted: 17 July 2004

Abstract

We present the results of narrow-band and broad-band imaging with the Very Large Telescope of the field surrounding the radio galaxy TN J0924–2201 at . Fourteen candidate Lyα emitters with a rest-frame equivalent width of >20 Å were detected. Spectroscopy of 8 of these objects showed that 6 have redshifts similar to that of the radio galaxy. The density of emitters at the redshift of the radio galaxy is estimated to be a factor 1.5–6.2 higher than in the field, and comparable to the density of Lyα emitters in radio galaxy protoclusters at and 2.2. The Lyα emitters near TN J0924–2201 could therefore be part of a structure that will evolve into a massive cluster. These observations confirm that substantial clustering of Lyα emitters occurs at and support the idea that radio galaxies pinpoint high density regions in the early Universe.