Kavli Affiliate: Mark Vogelsberger
| First 5 Authors: Desika Narayanan, Desika Narayanan, , ,
| Summary:
A combination of JWST observations at z~12-14 and ALMA observations of
extremely dust-rich systems at z~6 has demonstrated that dust grows extremely
fast in the early Universe, with galaxies amassing up to 10^7 Msun of dust in
just 500 Myr between z=12->6. In this paper we demonstrate, via a series of
numerical experiments conducted in cosmological zoom-in simulations, that a
likely pathway for this dust accumulation in the first formed galaxies is
through production at early times via supernovae, followed by the rapid growth
on ultrasmall dust grains. Our main results follow. The stellar production of
dust dominates until z ~ 10-11 at which point galaxies transition to a
growth-dominated regime. We employ a Shapley analysis to demonstrate that the
local density is the dominant factor driving dust growth, followed by the grain
size distribution. A rapid rise in the small-to-large grain ratio with
decreasing redshift (owing to grain-grain shattering) drives growth through
increased dust surface area per unit mass. Growth models are necessary to match
the dust content of ALMA detected sources at z ~ 6. Finally, we demonstrate
that “blue monsters”, massive, UV-bright galaxies at $z>10$ with extremely
blue continuum slopes likely have dust-to stellar mass ratios 10^-4-10^-3, but
their top-heavy grain size distributions render them optically thin in the UV,
providing a natural explanation for their observed properties without requiring
exotic dust geometries.
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