Abstract
We study the sizes of galaxies in the Epoch of Reionization using a sample of
~100,000 galaxies from the BlueTides cosmological hydrodynamical simulation
from z=7 to 11. We find an inverse relationship between stellar mass and the
size measured from stellar mass maps, suggesting that the most massive galaxies
are more compact and dense than lower mass galaxies, which have flatter mass
distributions. We find a mildly negative relation between intrinsic
far-ultraviolet luminosity and size, while we find a positive size--luminosity
relation when measured from dust-attenuated images. This suggests that dust is
the predominant cause of the observed positive size--luminosity relation, with
dust preferentially attenuating bright sight lines resulting in a flatter
emission profile and thus larger measured sizes. We study the size--luminosity
relation across the rest-frame ultraviolet and optical, and find that the slope
decreases at longer wavelengths; this is a consequence of the relation being
caused by dust, which produces less attenuation at longer wavelengths. We find
that the far-ultraviolet size--luminosity relation shows mild evolution from
z=7 to 11, and galaxy size evolves with redshift as $R\propto(1+z)^-m$, where
$m=0.559\pm0.008$. Finally, we investigate the sizes of z=7 quasar host
galaxies, and find that while the intrinsic sizes of quasar hosts are small
relative to the overall galaxy sample, they have comparable sizes when measured
from dust-attenuated images.
Description
The Impact of Dust on the Sizes of Galaxies in the Epoch of Reionization
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