Multi-Phase ISM in the z = 5.7 Hyperluminous Starburst SPT0346-52

TL;DR

This study investigates the complex multi-phase interstellar medium in the hyperluminous galaxy SPT0346-52 at redshift 5.7, revealing dominant molecular gas, supersolar metallicity, and line deficits through ALMA observations and modeling.

Contribution

It provides detailed spatially-resolved analysis of the multi-phase ISM in a high-redshift starburst galaxy using new ALMA data and advanced modeling techniques.

Findings

Molecular gas mass is about 4 times higher than neutral atomic gas.

Ionized gas density is less than 32 cm^-3.

Line deficits observed in all five studied emission lines.

Abstract

SPT0346-52 (z=5.7) is the most intensely star-forming galaxy discovered by the South Pole Telescope, with Sigma_SFR ~ 4200 Msol yr^-1 kpc^-2. In this paper, we expand on previous spatially-resolved studies, using ALMA observations of dust continuum, [NII]205 micron, [CII]158 micron, [OI]146 micron, and undetected [NII]122 micron and [OI]63 micron emission to study the multi-phase interstellar medium (ISM) in SPT0346-52. We use pixelated, visibility-based lens modeling to reconstruct the source-plane emission. We also model the source-plane emission using the photoionization code CLOUDY and find a supersolar metallicity system. We calculate T_dust = 48.3 K and lambda_peak = 80 micron, and see line deficits in all five lines. The ionized gas is less dense than comparable galaxies, with n_e < 32 cm^-3, while ~20% of the [CII]158 emission originates from the ionized phase of the ISM. We also calculate the masses of several phases of the ISM. We find that molecular gas dominates the mass of the ISM in SPT0346-52, with the molecular gas mass ~4x higher than the neutral atomic gas mass and ~100x higher than the ionized gas mass.