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

Abstract

Aims. We present observations aimed at exploring both the nature of Lyα emitting nebulae (Lyα 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' × 10' map at 870 μm}, 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 μm flux densities in the range 3-21 mJy, rms noise ~0.8-2.4 mJy, and far-IR luminosities probably in the range ~5-20 x 10^(12) L_⊙. Only one of the four 50 kpc-extended Lyα blobs has a secure 870 μm counterpart. The 870 μm 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 μm SEDs of the submillimeter sources indicate they are starburst dominated, with redshifts mostly ≳2. However, there is evidence of a high-z AGN in ~30% of the sources.