ALMA Observations of Lyman-alpha Blob 1: Multiple major-mergers and widely distributed interstellar media

TL;DR

This study uses ALMA to observe a giant Lyman-alpha blob at z=3.1, revealing complex morphology, multiple merging galaxies, and extended interstellar media likely powered by star formation and gravitational interactions.

Contribution

First detailed ALMA observations of LAB1 showing multiple mergers and widespread interstellar media, advancing understanding of galaxy formation in proto-clusters.

Findings

Detected dust continuum, [C II], and CO(4-3) emissions with complex morphology.

Identified seven galaxies around LAB1, indicating multiple mergers.

Extended interstellar media likely originate from star formation, not shocks.

Abstract

We present observations of a giant Lyman-alpha blob in the SSA22 proto-cluster at z=3.1, SSA22-LAB1, taken with the Atacama Large Millimeter/submillimeter Array (ALMA). Dust continuum, along with [C II]158um, and CO(4-3) line emission have been detected in LAB1, showing complex morphology and kinematics across a ~100 kpc central region. Seven galaxies at z=3.0987-3.1016 in the surroundings are identified in [C II] and dust continuum emission, with two of them potential companions or tidal structures associated with the most massive galaxies. Spatially resolved [C II] and infrared luminosity ratios for the widely distributed media (L[C II]/LIR~0.01-0.001) suggest that the observed extended interstellar media are likely to have originated from star-formation activity and the contribution from shocked gas is probably not dominant. LAB1 is found to harbour a total molecular gas mass Mmol=(8.7+/-2.0)e+10 Msun, concentrated in the core region of the Ly-alpha-emitting area. While (primarily obscured) star-formation activity in the LAB1 core is one of the most plausible power sources for the Ly-alpha emission, multiple major-mergers found in the core may also play a role in making LAB1 exceptionally bright and extended in Ly-alpha as a result of cooling radiation induced by gravitational interactions.