We report on a Hubble Space Telescope search for rest-frame ultraviolet emission from the host galaxies of five far-infrared-luminous z \simeq { } 6 quasars and the z = 5.85 hot-dust free quasar SDSS J0005-0006 .
We perform 2D surface brightness modeling for each quasar using a Markov-Chain Monte-Carlo estimator , to simultaneously fit and subtract the quasar point source in order to constrain the underlying host galaxy emission .
We measure upper limits for the quasar host galaxies of m _ { J } > 22.7 mag and m _ { H } > 22.4 mag , corresponding to stellar masses of M _ { \ast } < 2 \times 10 ^ { 11 } M _ { \odot } .
These stellar mass limits are consistent with the local M _ { \textrm { BH } } - M _ { \ast } relation .
Our flux limits are consistent with those predicted for the UV stellar populations of z \simeq 6 host galaxies , but likely in the presence of significant dust ( \langle A _ { \mathrm { UV } } \rangle \simeq 2.6 mag ) .
We also detect a total of up to 9 potential z \simeq 6 quasar companion galaxies surrounding five of the six quasars , separated from the quasars by 1 \farcs 4 – 3 \farcs 2 , or 8.4–19.4 kpc , which may be interacting with the quasar hosts .
These nearby companion galaxies have UV absolute magnitudes of -22.1 to -19.9 mag , and UV spectral slopes \beta of -2.0 to -0.2 , consistent with luminous star-forming galaxies at z \simeq 6 .
These results suggest that the quasars are in dense environments typical of luminous z \simeq 6 galaxies .
However , we can not rule out the possibility that some of these companions are foreground interlopers .
Infrared observations with the James Webb Space Telescope will be needed to detect the z \simeq 6 quasar host galaxies and better constrain their stellar mass and dust content .