EDP Sciences
Free access
Volume 485, Number 3, July III 2008
Page(s) 645 - 655
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:200809500
Published online 11 March 2008

A&A 485, 645-655 (2008)
DOI: 10.1051/0004-6361:200809500

Submillimeter observations of the J2142-4423 Ly$\sf\alpha$ protocluster at z = 2.38

A. Beelen1, A. Omont2, N. Bavouzet1, A. Kovács3, G. Lagache1, C. De Breuck4, A. Weiss3, K. M. Menten3, J. W. Colbert5, H. Dole1, G. Siringo3, and E. Kreysa3

1  Institut d'Astrophysique Spatiale, Bât. 121, Université Paris-Sud, 91405 Orsay Cedex, France
    e-mail: alexandre.beelen@ias.u-psud.fr
2  Institut d'Astrophysique de Paris, CNRS and Université Pierre et Marie Curie, 98bis Bd Arago, 75014 Paris, France
3  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
4  European Southen Observatory, Karl Schwarzschild Straße 2, 85748 Garching, Germany
5  Science Center, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125-0600, USA

Received 2 February 2008 / Accepted 4 March 2008

Aims. We present observations aimed at exploring both the nature of Ly$\alpha$ emitting nebulae ("Ly$\alpha$ blobs") at z=2.38 and the way they trace large scale structure (LSS), by exploring their proximity to "maximum starbursts" through submillimeter emission. Our most important objectives are to make a census of associated submillimeter galaxies (SMGs), check their properties, and look for a possible overdensity in the protocluster J2142-4426 at z=2.38.
Methods. We used the newly commissioned Large APEX Bolometer Camera (LABoCa) on the Atacama Pathfinder EXperiment (APEX) telescope, in its Science Verification phase, to carry out a deep $10\arcmin \times 10\arcmin$ map at 870  ${\mu {\rm m}}$, and we performed multiple checks of the quality of data processing and source extraction.
Results. Our map, the first published deep image, confirms the capabilities of APEX/LABoCa as the most efficient current equipment for wide and deep submm mapping. Twenty-two sources were securely extracted with 870  ${\mu {\rm m}}$ flux densities in the range 3-21 mJy, rms noise ~0.8-2.4 mJy, and far-IR luminosities probably in the range ${\sim}$5- $20\times 10^{12}$ $L_\odot$. Only one of the four 50 kpc-extended Ly$\alpha$ blobs has a secure 870  ${\mu {\rm m}}$ counterpart. The 870  ${\mu {\rm m}}$ source counts in the whole area are marginally higher than in the SHADES SCUBA survey, with a possible over-density around this blob. The majority of the 3.6-24  ${\mu {\rm m}}$SEDs of the submillimeter sources indicate they are starburst dominated, with redshifts mostly $\gtrsim$2. However, there is evidence of a high-z AGN in ~30% of the sources.

Key words: galaxies: starburst -- galaxies: high-redshift -- submillimeter -- infrared: galaxies -- ultraviolet: galaxies -- large-scale structure of Universe

© ESO 2008