Submillimeter observations of the J2142-4423 Lya protocluster at z = 2.38

TL;DR

This study uses submillimeter observations to explore the nature of Lya blobs and their connection to large-scale structures at z=2.38, identifying associated galaxies and potential overdensities in a protocluster.

Contribution

First deep submillimeter map of the J2142-4423 protocluster, revealing associated SMGs, their properties, and evidence of overdensity and high-z AGN presence.

Findings

22 submillimeter sources detected with fluxes 3-21 mJy

One Lya blob has a secure submm counterpart

Possible overdensity of sources around the blob

Abstract

We present observations aimed at exploring both the nature of Lya emitting nebulae (Lya 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. 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'x10' map at 870 micron, and we performed multiple checks of the quality of data processing and source extraction. 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 micron 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) Lo. Only one of the four 50 kpc-extended Lya blobs has a secure 870 micron counterpart. The 870 micron 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 micron 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.