COSMOS/AzTEC-3 submillimeter galaxy datacube

We identified ten Ly{alpha} emitting sources, including two regions with extended emission: one embedding AzTEC-3 and LBG-3, which is a star-forming galaxy located 2" (12kpc) north of the SMG and another toward LBG-1, which is a star-forming galaxy located 15" (90kpc) to the southeast. The two regions extend for ~27x38kpc^2^ (~170x240ckpc^2^) and ~20x20kpc^2^ (~125x125ckpc^2^), respectively. The sources appear distributed in an elongated configuration of about 70" (430kpc) in extent.

The number of sources confirms the overdensity around AzTEC-3. We study the MUSE spectra of the AzTEC-3+LBG-3 system and LBG-1 in detail. For the AzTEC-3+LBG-3 system, the Ly{alpha} emission appears redshifted and more spatially extended than the [CII] line emission.

Similarly, the Ly{alpha} line spectrum is broader in velocity than [CII] for LBG-1. In the former spectrum, the Ly{alpha} emission is elongated to the north of LBG-3 and to the south of AzTEC-3, where a faint Ly{alpha} emitting galaxy is also located. The elongated structures could resemble tidal features due to the interaction of the two galaxies with AzTEC-3.

Also, we find a bridge of gas, revealed by the Ly{alpha} emission between AzTEC-3 and LBG-3. The Ly{alpha} emission toward LBG-1 embeds its three components. The HI kinematics support the idea of a merger of the three components.

Given the availability of CO and [CII] observations from previous campaigns, and the Ly{alpha} information from our MUSE dataset, we find evidence of starburst-driven phenomena and interactions around AzTEC-3. The stellar mass of the galaxies of the overdensity and the Ly{alpha} luminosity of the HI nebula associated with AzTEC-3 imply a dark matter halo of ~10^12^M_{sun}_ at z=5.3. By comparing this with semi-analytical models, the dark matter halo mass indicates that the region could evolve into a cluster of 2x10^13^M_{sun}_ by z=2 and into a Fornax-type cluster at z=0 with a typical mass of 2x10^14^M_{sun}_.