Dust Obscured Star Forming Galaxies in the Early Universe

Abstract

Motivated by recent observational constraints on dust reprocessed emission in star forming galaxies at $z\sim 6$ and above we use the very-large cosmological hydrodynamical simulation \bluetides\ to explore predictions for the amount of dust obscured star formation in the early Universe ($z>8$). \bluetides\ matches current observational constraints on both the UV luminosity function and galaxy stellar mass function and predicts that approximately $90\%$ of the star formation in high-mass ($M_{\ast }>10^{10}{\mathrm{M}}_{\odot }$) galaxies at $z=8$ is already obscured by dust. The relationship between dust attenuation and stellar mass predicted by \bluetides\ is consistent with that observed at lower redshift. However, observations of several individual objects at $z>6$ are discrepant with the predictions, though it is possible their uncertainties may have been underestimated. We find that the predicted surface density of $z\ge 8$ sub-mm sources is below that accessible to current {\em Herschel}, SCUBA-2, and ALMA sub-mm surveys. However, as ALMA continues to accrue additional surface area the population of $z>8$ dust-obscured galaxies may become accessible in the near future.

8 pages, accepted for publication in MNRAS