2024/11/10 by Matus Rybak, Rybak, Matus, Jasper Jansen +33 · 1 citation
Chemistry · Engineering · #Advanced Thermodynamic Systems and Engines #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Phase Equilibria and Thermodynamics #Spectroscopy and Laser Applications
paper · pdf · doi:10.48550/arxiv.2411.06474
openalex publication_date 2024/11/10 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Massive, intensely star-forming galaxies at high redshift require a supply of molecular gas from their gas reservoirs, replenished by infall from the surrounding circumgalactic medium, to sustain their immense star-formation rates. However, our knowledge of the extent and morphology of their cold-gas reservoirs is still in its infancy. We present the results of stacking 80 hours of JVLA observations of CO(1--0) emission -- which traces the cold molecular gas -- in nineteen z=2.0-4.5 dusty, star-forming galaxies from the AS2VLA survey. The visibility-plane stack reveals extended emission with a half-light radius of 3.8±0.5~kpc, 2--3× more extended than the dust-obscured star formation and 1.4±0.2× more extended than the stellar emission revealed by JWST. Stacking the [CI](1--0) observations for ten galaxies from our parent sample yields a half-light radius ≤2.6~kpc, marginally smaller than CO(1--0). The CO(1--0) size is also comparable to the [CII] halos detected around high-redshift star-forming galaxies, suggesting these arise from molecular gas. Photo-dissociation region modelling indicates that the extended CO(1--0) emission arises from clumpy, dense clouds rather than smooth, diffuse gas. Our results show that the bulk (up to 80%) of molecular gas resides outside the star-forming region; with only a small part directly contributing to their current star formation.