becomes small relative to the point spread function (PSF) of current telescopes, and so the bright quasar entirely conceals the host galaxy emission [e.g. @Mechtley2012]. Surface brightness dimming also causes the host galaxies and any tidal features to be more difficult to detect at high redshift.

In an attempt to detect the underlying UV emission from the host of the redshift $z = 6.42$ quasar SDSS J114816.64+525150.3 (hereafter SDSS J1148+5251), @Mechtley2012 used GALFIT [@peng_2010] to model the quasar contribution to the emission in Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) images. This quasar model was subtracted to obtain upper limits on the brightness of the host galaxy, of $m_J>22.8$ and $m_H>23.0$ mag. To improve the fitting method, @Mechtley2014 developed a Markov-Chain Monte-Carlo (MCMC) simultaneous fitting software, [^1]. While this technique allows for host detections at lower redshifts [$z=2$, @Mechtley2016; @Marian2019], the smaller angular sizes of the hosts at higher redshifts make this significantly more challenging.

In this paper, we present deep near-infrared F125W (J) and F160W (H) HST WFC3 images of six $z\simeq6$ quasars. We describe our efforts to detect rest-frame near-UV emission from the hosts, and present the most robust upper limits to date on the rest-frame 