Abstract

We present millimeter observations of the host galaxy of the most distant blazar known, VLASS J041009.05-013919.88 (hereafter J0410-0139) at z = 7, using Atacama Large Millimeter/submillimeter Array (ALMA) and NOrthern Extended Millimeter Array (NOEMA) observations. The ALMA data reveal a (2.02 +/- 0.36) x 10(42) erg s(-1) [C II] 158 mu m emission line at z = 6.9964 with a [C II]-inferred star formation rate (SFR) of 58 +/- 9 M-circle dot yr(-1). We estimate a dynamical mass of M-dyn,[C II(]) = (4.6 +/- 2.0) x 10(9)M(circle dot), implying a black hole mass to host a dynamical mass ratio of 0.15(-0.05)(+0.08). The 238 GHz continuum (rest-frame IR) decreased by similar to 33% from the NOEMA to the ALMA observations taken similar to 10 months apart. The Very Large Array 3-10 GHz radio flux densities showed a similar to 37% decrease in a similar time frame, suggesting a causal connection. At face value, J0410-0139 would have the lowest [CII]-to-IR luminosity ratio of a z > 5.7 quasar reported to date (similar to 10(-4)). However, if only <20% of the measured IR luminosity was due to thermal emission from dust, the [C II]-to-IR luminosity ratio would be typical of (U)LIRGs, and the SFRs derived from [C II] and IR luminosities would be consistent. These results provide further evidence that synchrotron emission significantly contributes to the observed rest-frame IR emission of J0410-0139, similar to what has been reported in some radio-loud active galactic nuclei at z < 1.