New constraints on the molecular gas content of a z ∼ 8 galaxy from JVLA CO(J = 2–1) observations

Journal article

As the primary fuel for star formation, molecular gas plays a key role in galaxy evolution. A number of techniques have been used for deriving the mass of molecular reservoirs in the early Universe (e.g., [CII]158 𝜇m, [CI], dust continuum), but the standard approach of CO-based estimates has been limited to a small number of galaxies due to the intrinsic faintness of the line. We present Jansky Very Large Array (JVLA) observations of the 𝑧 ∼ 8.31 galaxy MACS0416_Y1, targeting CO(2-1) and rest-frame radio continuum emission, which result in upper limits on both quantities. Adding our continuum limit to the published far-infrared (FIR) spectral energy distribution (SED), we find a small non-thermal contribution to the FIR emission, a low dust mass (log10 (MD/M⊙) ∼ 5), and an abnormally high dust temperature (TD ≳ 90 K) that may indicate a recent starburst. Assuming a low metallicity (𝑍/𝑍⊙ ∼ 0.25), we find evidence for 𝑀H2,CO ≲ 1010 M⊙, in agreement with previous [CII] investigations (𝑀H2,[CII] ∼ 109.6 M⊙). Upcoming JWST observations of this source will result in a precise determination of 𝑍, enabling better constraints and an unprecedented view of the gaseous reservoir in this primordial starburst galaxy.

Authors: Jones, G; Witstok, J; Concas, A; Laporte, N

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Wiley
• Journal: Monthly Notices of the Royal Astronomical Society: Letters
• Volume: 529
• Issue: 1
• Pages: L1–L6
• Publication date: 2023-12-09
• Acceptance date: 2023-12-07
• DOI: 10.1093/mnrasl/slad189
• EISSN: 1745-3933
• ISSN: 1745-3925
• Language: English
• Keywords: galaxies: ISM; radio continuum: galaxies; galaxies: high-redshift