2025/02/10 by Hideki Umehata, Umehata, Hideki, Mariko Kubo +3 · 4 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2502.06538
openalex publication_date 2025/02/10 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present a study of the molecular gas reservoirs and dust contents in three quiescent galaxies (QGs) located in the core of the z=3.09 SSA22 proto-cluster. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we detect CO(3--2) emission in one galaxy, ADF22-QG1, marking the first direct detection of molecular gas in a quiescent galaxy from the early universe. The detected galaxy, ADF22-QG1, has a molecular gas mass of logM\rm H2/M_\odot = 10.26 ± 0.07 assuming a CO-to-H2 conversion factor α\rm CO = 4.4 (logM\rm H2/M_\odot = 9.52 ± 0.07 for α\rm CO = 0.8), corresponding to a gas mass fraction of f\rm gas ≈ 14% (2.5%). The gas-to-dust ratio δ\rm gdr\gtrsim170 (δ\rm gdr\gtrsim30) for α\rm CO = 4.4 (α\rm CO =0.8) is also derived for the first time for a QG at the epoch. For the other two galaxies, ADF22-QG2 and ADF22-QG3, non detections of CO(3--2) emission provide upper limits, f\rm gas ≈ 17% (3.1%) and f\rm gas ≈ 13% (2.4%), respectively. The inferred gas-consumption history of ADF22-QG1, based on its star-formation history, suggests that (i) dusty star-forming galaxies (DSFGs) at z = 4--6 are plausible progenitors, and (ii) the cessation of gas accretion from cosmic web filaments plays an important role in their evolution to quenched systems. Furthermore, the presence of a detectable molecular gas reservoir in ADF22-QG1 indicates that additional mechanisms, such as morphological quenching, may be required to fully explain its quiescent nature.