New Constraints on the Molecular Gas in the Prototypical HyLIRGs BRI1202-0725 & BRI1335-0417

TL;DR

This study uses high-resolution VLA observations to analyze the molecular gas in two hyper-luminous infrared galaxies at high redshift, revealing detailed gas distributions and insights into their star formation and galaxy formation processes.

Contribution

It provides unprecedented high-resolution CO(2-1) line and continuum observations of HyLIRGs at z>4, revealing detailed gas morphology and dynamics related to early galaxy formation.

Findings

Detected extended CO emission indicating complex gas structures.

Gas depletion timescales suggest intense starburst activity.

Evidence of merger-driven galaxy formation at high redshift.

Abstract

We present Karl G Jansky Very Large Array (VLA) observations of CO(2-1) line emission and rest-frame 250GHz continuum emission of the Hyper-Luminous IR Galaxies (HyLIRGs) BRI1202-0725 (z=4.69) and BRI1335-0417 (z=4.41), with an angular resolution as high as 0.15". Our low order CO observations delineate the cool molecular gas, the fuel for star formation in the systems, in unprecedented detail. For BRI1202-0725, line emission is seen from both extreme starburst galaxies: the quasar host and the optically obscured submm galaxy (SMG), in addition to one of the Lyman-alpha emitting galaxies in the group. Line emission from the SMG shows an east-west extension of about 0.6". For Lyalpha-2, the CO emission is detected at the same velocity as [CII] and [NII], indicating a total gas mass ~4.0*10^10 solar masses. The CO emission from BRI1335-0417 peaks at the nominal quasar position, with a prominent northern extension (~1", a possible tidal feature). The gas depletion timescales are ~10^7 years for the three HyLIRGs, consistent with extreme starbursts, while that of Lyalpha-2 may be consistent with main sequence galaxies. We interpret these sources as major star formation episodes in the formation of massive galaxies and supermassive black holes (SMBHs) via gas rich mergers in the early Universe.