http://arxiv.org/abs/2205.15388
We determine the bright end of the rest-frame UV luminosity function at $z=8-10$ by selecting bright $z\gtrsim 8$ photometric candidates from the largest systematic compilation of HST (pure-)parallel observations to date, the Super-Brightest-of-Reionizing-Galaxies (SuperBoRG) data set. The data set includes $\sim300$ independent sightlines distributed across the sky with WFC3 observations, totalling $800-1300$ arcmin$^2$ (depending on redshift). We identify 31 $z\gtrsim8$ candidates via colour selection and photo-$z$ analysis with observed magnitude ($24.1< H_{160} <26.6$). Following detailed completeness and source recovery simulations in each independent field, as well as modelling of interloper contamination, we derive rest-frame UV luminosity functions at $z=8-10$ down to UV magnitude $\simeq-23$. We find that the bright-end of the galaxy luminosity function can be described both by a Schechter and by a double power-law function, with our space-based large area determination showing some tentative discrepancies with the luminosity functions derived from ground-based observations at the same redshifts. Interestingly, the UV luminosity function we derived at $z=8$ is consistent with no evolution of the bright end from $z=6-7$, suggesting a substantial contribution from AGNs at magnitude $M_{UV}<-22$. On the other hand, our derived UVLFs at all redshifts are still consistent with a scenario where the UV light originates from stars, but there is a vanishing dust content at $z\gtrsim 7.5$. Both scenarios raise interesting prospects to further understand galaxy formation in extreme objects during the epoch of reionization thanks to upcoming James Webb Space Telescope spectroscopic observations.
N. Leethochawalit, G. Roberts-Borsani, T. Morishita, et. al.
Wed, 1 Jun 22
64/65
Comments: Submitted to MNRAS on 4 May 2022. 11 pages, 9 figures
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