the stellar component of this quasar host galaxy.

The stellar mass limits of five of our six quasars are consistent with the local @kormendy_2013 $M_\ast-M_{\mathrm{BH}}$ relation. SDSS-J0203+0012, however, has a stellar mass of $M_\ast<1.89\times10^{11}M_\odot$, lower than expected by the local relation, given its extremely large black hole mass of $M_{\mathrm{BH}}=5.2\times10^{10}M_\odot$ [Table \[tab\_targets\], @Shen2019]. However, we note that this black hole mass is determined by the C IV line, as the more robust Mg II line is not covered by ground-based observations. SDSS-J0203+0012 is a broad absorption line (BAL) quasar [@mortlock_2009] and so the dynamics probed by the C IV line are likely affected by the outflows. Hence we place no significance on our black hole–stellar mass relation limit for this object.

The $M_\ast-M_{\mathrm{UV}}$ relation is derived from observations of UV-selected galaxies, and might not apply if our hosts were dusty star-forming or quiescent galaxies; as these galaxies may be particularly dusty, our mass limits would be underestimates. Mid-infrared observations to allow for detailed SED fitting, using the upcoming James Webb Space Telescope (JWST), for example, are necessary to accurately determine the stellar masses of these potentially dusty host galaxies.

![The black hole–stellar mass relation for our $z\simeq6$ quasar host galaxies, 