The Nature of HI-absorption-selected Galaxies at z ≈ 4
Abstract
We report a Karl G. Jansky Very Large Array (JVLA) search for redshifted CO(1-0) or CO(2-1) emission, and a Hubble Space Telescope Wide Field Camera 3 (HST-WFC3) search for rest-frame near-ultraviolet (NUV) stellar emission, from seven HI-selected galaxies associated with high-metallicity ([M/H] ≥ -1.3) damped Lyα absorbers (DLAs) at z ≈ 4. The galaxies were earlier identified by Atacama Large Millimeter/submillimeter Array imaging of their [CII] 158 μm emission. We also used the JVLA to search for CO(2-1) emission from the field of a low-metallicity ([M/H] = -2.47) DLA at z ≈ 4.8. No statistically significant CO emission is detected from any of the galaxies, yielding upper limits of Mmol < (7.4-17.9) × 1010 × (αCO/4.36) M⊙ on their molecular gas mass. We detect rest-frame NUV emission from four of the seven [CII] 158 μm-emitting galaxies, the first detections of the stellar continuum from HI-selected galaxies at z ≳ 4. The HST-WFC3 images yield typical sizes of the stellar continua of ≈2-4 kpc and inferred dust-unobscured star formation rates (SFRs) of ≈5.0-17.5 M⊙ yr-1, consistent with, or slightly lower than, the total SFRs estimated from the far-infrared (FIR) luminosity. We further stacked the CO(2-1) emission signals of six [CII] 158 μm-emitting galaxies in the image plane. Our non-detection of CO(2-1) emission in the stacked image yields the limit Mmol < 4.1 × 1010 × (αCO/4.36) M⊙ on the average molecular gas mass of the six galaxies. Our molecular gas mass estimates and NUV SFR estimates in HI-selected galaxies at z ≈ 4 are consistent with those of main-sequence galaxies with similar [CII] 158 μm and FIR luminosities at similar redshifts. However, the NUV emission in the HI-selected galaxies appears more extended than that in main-sequence galaxies at similar redshifts.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2021
- DOI:
- 10.3847/1538-4357/ac12d2
- arXiv:
- arXiv:2107.05108
- Bibcode:
- 2021ApJ...921...68K
- Keywords:
-
- Galaxies;
- High-redshift galaxies;
- 573;
- 734;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 16 pages, 6 figures, accepted for publication in ApJ