Discovery of a Protocluster Core Associated with an Enormous Lya Nebula at z=2.3

The MAMMOTH-1 nebula at z = 2.317 is an enormous Ly alpha nebula (ELAN) extending to a similar to 440 kpc scale at the center of the extreme galaxy overdensity BOSS 1441. In this paper, we present observations of the CO(3 - 2) and 250 GHz dust-continuum emission from MAMMOTH-1 using the IRAM NOrthern Extended Millimeter Array. Our observations show that CO(3 - 2) emission in this ELAN has not extended widespread emission into the circum- and inter-galactic media. We also find a remarkable concentration of six massive galaxies in CO(3 - 2) emission in the central similar to 100 kpc region of the ELAN. Their velocity dispersions suggest a total halo mass of M (200c ) similar to 10(13.1) M (circle dot), marking a possible protocluster core associated with the ELAN. The peak position of the CO(3 - 2) line emission from the obscured AGN is consistent with the location of the intensity peak of MAMMOTH-1 in the rest-frame UV band. Its luminosity line ratio between the CO(3 - 2) and CO(1 - 0)r (3,1) is 0.61 +/- 0.17. The other five galaxies have CO(3 - 2) luminosities in the range of (2.1-7.1) x 10(9) K km s(-1) pc(2), with the star-formation rates derived from the 250 GHz continuum of (<36)-224 M (circle dot) yr(-1). Follow-up spectroscopic observations will further confirm more member galaxies and improve the accuracy of the halo mass estimation.

Automated summary

The study presents observations of the CO(3 - 2) and 250 GHz dust-continuum emission from the MAMMOTH-1 nebula. It reveals a concentration of six massive galaxies in the central region of the nebula, suggesting a potential protocluster core. Further spectroscopic observations are needed to confirm more member galaxies and improve halo mass estimation accuracy.