Enabling the next generation of cm-wavelength studies of high-redshift molecular gas with the SKA

TL;DR

The paper discusses how the Square Kilometre Array (SKA) will revolutionize high-redshift molecular gas studies, complementing existing telescopes like ALMA and VLA, especially for dense gas tracers linked to star formation.

Contribution

It outlines the potential of SKA1 and SKA2 to advance molecular emission line studies at cm wavelengths, focusing on dense gas tracers in the early universe.

Findings

SKA will detect and image atomic 21 cm HI in distant galaxies.

SKA will complement ALMA in observing high-J CO and [CII] lines.

Enhanced sensitivity of SKA will enable detailed studies of star-forming regions at high redshift.

Abstract

The Square Kilometre Array will be a revolutionary instrument for the study of gas in the distant Universe. SKA1 will have sufficient sensitivity to detect and image atomic 21 cm HI in individual galaxies at significant cosmological distances, complementing ongoing ALMA imaging of redshifted high-J CO line emission and far-infrared interstellar medium lines such as [CII] 157.7 um. At frequencies below ~50 GHz, observations of redshifted emission from low-J transitions of CO, HCN, HCO+, HNC, H2O and CS provide insight into the kinematics and mass budget of the cold, dense star-forming gas in galaxies. In advance of ALMA band 1 deployment (35 to 52 GHz), the most sensitive facility for high-redshift studies of molecular gas operating below 50~GHz is the Karl G. Jansky Very Large Array (VLA). Here, we present an overview of the role that the SKA could play in molecular emission line studies during SKA1 and SKA2, with an emphasis on studies of the dense gas tracers directly probing regions of active star-formation.