Kavli Affiliate: George Efstathiou
| First 5 Authors: Luke Conaboy, Ilian T. Iliev, Anastasia Fialkov, Keri L. Dixon, David Sullivan
| Summary:
Supersonic relative motion between baryons and dark matter due to the
decoupling of baryons from the primordial plasma after recombination affects
the growth of the first small-scale structures. Large box sizes (greater than a
few hundred Mpc) are required to sample the full range of scales pertinent to
the relative velocity, while the effect of the relative velocity is strongest
on small scales (less than a few hundred kpc). This separation of scales
naturally lends itself to the use of `zoom’ simulations, and here we present
our methodology to self-consistently incorporate the relative velocity in zoom
simulations, including its cumulative effect from recombination through to the
start time of the simulation. We apply our methodology to a large-scale
cosmological zoom simulation, finding that the inclusion of relative velocities
suppresses the halo baryon fraction by $46$–$23$ per cent between $z=13.6$ and
$11.2$, in qualitative agreement with previous works. In addition, we find that
including the relative velocity delays the formation of star particles by $sim
20 {~rm Myr}$ Myr on average (of the order of the lifetime of a $sim 9~{rm
M}_odot$ Population III star) and suppresses the final stellar mass by as much
as $79$ per cent at $z=11.2$.
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