The feasibility of constraining DM interactions with high-redshift
  observations by JWST
  Observations of the high redshift universe provide a promising avenue for
constraining the nature of the dark matter (DM). This will be even more true
following the now successful launch of the James Webb Space Telescope (JWST).
We run cosmological simulations of galaxy formation as a part of the Effective
Theory of Structure Formation (ETHOS) project to compare the properties of high
redshift galaxies in Cold (CDM) and alternative DM models which have varying
relativistic coupling and self-interaction strengths. Phenomenologically, the
interacting DM scenarios result in a cutoff in the linear power spectrum on
small-scales, followed by a series of "dark acoustic oscillations" (DAOs). We
find that DM interactions suppress the abundance of galaxies below $M_\star
\sim 10^8\, M_\odot$ for the models considered. The cutoff in the linear power
spectrum generally causes a delay in structure formation relative to CDM.
Objects in ETHOS that end up at the same final masses as their CDM counterparts
are characterised by a more vigorous phase of early star formation. While
galaxies with $M_\star \lesssim 10^6\,{M_\odot}$ make up more than 60 per cent
of star formation in CDM at $z\approx 10$, they contribute only about half the
star formation density in ETHOS. These differences in star formation diminish
with decreasing redshift. We find that the effects of DM self-interactions are
negligible compared to effects of relativistic coupling (i.e. the effective
initial conditions for galaxy formation) in all properties of the galaxy
population we examine. Finally, we show that the clustering strength of
galaxies at high redshifts depends sensitively on DM physics, although these
differences are manifest on scales that may be too small to be measurable by
JWST.
