Dust in the early Universe: Evidence for non-stellar dust production or observational errors?

TL;DR

This paper investigates the origin of large dust quantities in high-redshift galaxies, questioning stellar production sufficiency and proposing non-stellar dust formation, but finds observational uncertainties may explain the discrepancies.

Contribution

It introduces a model with metallicity-dependent, non-stellar dust formation to explain high dust masses, highlighting potential issues with current observational interpretations.

Findings

Stellar dust production alone is likely insufficient in high-redshift galaxies.

Non-stellar dust formation would require an unrealistically high dust-to-metals ratio.

Observational uncertainties may account for the large dust-to-gas ratios observed.

Abstract

Observations have revealed unexpectedly large amounts of dust in high-redshift galaxies and its origin is still much debated. Valiante et al. (2009, MNRAS, 397, 1661) suggested the net stellar dust production of the quasar host galaxy SDSS J1148+5251 may be sufficient to explain the large dust mass detected in this galaxy, albeit under some very special assumptions (e.g., 'closed box' evolution and a rather high gas mass). Here it is shown that since accretion of essentially pristine material may lower the efficiency of dust formation significantly, and the observationally derived dust-to-gas ratios for these high-redshift galaxies are remarkably high, stellar dust production is likely insufficient. A model including metallicity-dependent, non-stellar dust formation ('secondary dust') is presented. The required contribution from this non-stellar dust component appears too large, however. If all observational constraints are to be met, the resultant dust-to-metals ratio is close to unity, which means that almost all interstellar metals exist in the form dust. This is a very unlikely situation and suggests the large dust-to-gas ratios at high-redshifts may be due to observational uncertainties and/or or incorrect calibration of conversion factors for gas and dust tracers.