Dust formation, evolution, and obscuration effects in the very high-redshift universe

TL;DR

This paper explores dust formation, evolution, and its observational effects in the early universe at redshifts greater than 9, highlighting how dust impacts galaxy observations and redshift identification.

Contribution

It presents a model of dust evolution at high redshift, emphasizing the dominance of silicates and the potential for misidentifying galaxy redshifts due to dust features.

Findings

Silicate dust causes a UV opacity rise near the Lyman break.

Dust production is mainly from core collapse supernovae at z>9.

Dust effects can lead to misclassification of galaxy redshifts.

Abstract

The evolution of dust at redshifts z>9, and consequently the dust properties, differs greatly from that in the local universe. In contrast to the local universe, core collapse supernovae (CCSNe) are the only source of thermally-condensed dust. Because of the low initial dust-to-gas mass ratio, grain destruction rates are low, so that CCSNe are net producers of interstellar dust. Galaxies with large initial gas mass or high mass infall rate will therefore have a more rapid net rate of dust production comported to galaxies with lower gas mass, even at the same star formation rate. The dust composition is dominated by silicates, which exhibit a strong rise in the UV opacity near the Lyman break. This "silicate-UV break" may be confused with the Lyman break, resulting in a misidentification of a galaxies' photometric redshift. In this paper we demonstrate these effects by analyzing the spectral energy distribution (SED) of MACS1149-JD, a lensed galaxy at z=9.6. A potential 2mm counterpart of MACS1149-JD has been identified with GISMO. While additional observations are required to corroborate this identification, we use this possible association to illustrate the physical processes and the observational effects of dust in the very high redshift universe.