2026ApJ...998..248B -
Astrophys. J., 998, 248 (2026/February-3)
CHILES. XI. Resolved H I Morphologies and the Evolution of the H2/H I Ratio over the Last Five Billion Years.
BLUE BIRD J., LUBER N., GIM H.B., VAN GORKOM J.H., PISANO D.J., YUN M.S., MOMJIAN E., HESS K.M., LUCERO D., MEYER J.D. and CHUNG A.
Abstract (from CDS):
We present the neutral gas morphology of four galaxies from z = 0.22 to 0.47 obtained with the COSMOS HI Large Extragalactic Survey (CHILES). The H I is resolved at the highest redshift with the 7$\mathop{.}\limits^{\unicode{x02033}}$5 beam of CHILES and 43 kpc linear scale, with all four galaxies having extended H I. Three are massive galaxies (M* > 3 × 1010M⊙), with H I masses of (1.6-6.7) × 1010M⊙ and active star formation (3-30 M⊙ yr–1). The morphology and kinematics of the galaxies vary from regular to disturbed, including an asymmetric H I disk surrounding the fourth smaller galaxy (M* ∼ 109M⊙). CO (1-0) observations of the sample, obtained with the Large Millimeter Telescope, confirm the redshifts of three of the four galaxies, and we derive H2 masses of (0.4-5.2) × 1010M⊙. JWST imaging with four combined NIRCam filters reveals disturbed stellar components with compact knots in two of the galaxies. We combine our new higher-redshift galaxies with previously published observations to conduct a more complete study of H I and H2 evolution in the redshift range 0-0.5. With our H I flux-limited observations compared to similar lower-redshift galaxies with high stellar mass (M* > 1010M⊙), the results show that the mean H2/H I ratio at the highest redshift is 10.3 ± 3.4, larger than the mean H2/H I ratio in the local Universe.
Abstract Copyright:
© 2026. The Author(s). Published by the American Astronomical Society.
Journal keyword(s):
Galaxy evolution
Simbad objects:
5
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