Dust grain growth in the interstellar medium of 5<z<6.5 quasars

TL;DR

This study examines whether stellar sources like AGB stars and supernovae can explain the dust in high-redshift quasars, finding that supernovae and interstellar grain growth are likely contributors.

Contribution

It provides a quantitative analysis of dust production from stellar sources and suggests interstellar grain growth as a significant mechanism in early quasars.

Findings

AGB stars are insufficient for dust production in most z>5 QSOs.

Supernovae could account for dust in some QSOs but require high yields.

Interstellar dust grain growth is necessary in at least three QSOs.

Abstract

We investigate whether stellar dust sources i.e. asymptotic giant branch (AGB) stars and supernovae (SNe) can account for dust detected in 5<z<6.5 quasars (QSOs). We calculate the required dust yields per AGB star and per SN using the dust masses of QSOs inferred from their millimeter emission and stellar masses approximated as the difference between the dynamical and the H_2 gas masses of these objects. We find that AGB stars are not efficient enough to form dust in the majority of the z>5 QSOs, whereas SNe may be able to account for dust in some QSOs. However, they require very high dust yields even for a top-heavy initial mass function. This suggests additional non-stellar dust formation mechanism e.g. significant dust grain growth in the interstellar medium of at least three out of nine z>5 QSOs. SNe (but not AGB stars) may deliver enough heavy elements to fuel this growth.