  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$\mu$m, [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 $z\sim8.31$ 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
($\rm\log_{10}(M_D/M_{\odot})\sim5$), and an abnormally high dust temperature
($\rm T_D\gtrsim90K$) that may indicate a recent starburst. Assuming a low
metallicity ($Z/Z_{\odot}\sim0.25$), we find evidence for $M_{\rm
H_2,CO}\lesssim10^{10}$M$_{\odot}$, in agreement with previous [CII]
investigations ($M_{\rm H_2,[CII]}\sim10^{9.6}$M$_{\odot}$). 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.

Astrophysics of Galaxies