A supernova origin for dust in a high-redshift quasar

Abstract

Interstellar dust plays a crucial role in the evolution of the Universe by assisting the formation of molecules, by triggering the formation of the first low-mass stars, and by absorbing stellar ultraviolet-optical light and subsequently re-emitting it at infrared/millimetre wavelengths. Dust is thought to be produced predominantly in the envelopes of evolved (age >1 Gyr), low-mass stars. This picture has, however, recently been brought into question by the discovery of large masses of dust in the host galaxies of quasars at redshift z > 6, when the age of the Universe was less than 1 Gyr. Theoretical studies, corroborated by observations of nearby supernova remnants, have suggested that supernovae provide a fast and efficient dust formation environment in the early Universe. Here we report infrared observations of a quasar at redshift 6.2, which are used to obtain directly its dust extinction curve. We then show that such a curve is in excellent agreement with supernova dust models. This result demonstrates a supernova origin for dust in this high-redshift quasar, from which we infer that most of the dust at high redshifts probably has the same origin.

On the physical properties ofz≈6–8 galaxies

“…2. The possible indication for a 2175 Å dust absorption feature at such a high redshift is in contrast to evidence so far, suggesting the absence of this feature (see e.g., Maiolino et al 2004). …”

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

“…For these seven QSOs (including QSO 5 for which Maiolino et al 2004, claimed SN-origin dust) the required SN dust yields are within the theoretical limits without dust destruction (light blue area) and the values observed for SN remnants Cassiopeia A and Kepler (dashed line). For reasonable assumptions on the dust properties, AGB stars are not efficient enough and SNe would need to be unfeasibly efficient to form dust in these sources suggesting rapid grain grown in the ISM is likely to be responsible for the large dust masses.…”

“…Signatures of SN-origin dust have been claimed in the extinction curves of a z ∼ 6.2 QSO (Maiolino et al 2004; see also Gallerani et al 2010) and of two gamma-ray burst host galaxies, one at z ∼ 6.3 (Stratta et al 2007; but this result was undermined by Zafar et al 2010) and one at z ∼ 5 (Perley et al 2010).…”

Observational Comparison of Star Formation in Different Galaxy Types

“…One of the primary sources for dust in the present-day Universe are low-and intermediate-mass asymptotic giant branch stars, but these need at least some 500 Myr to 1 Gyr to begin generating dust in their envelopes. In quasars in the early Universe, other mechanisms are believed to be responsible, including dust production in supernovae of type II (Maiolino et al 2004) and in quasar winds (Elvis et al 2002). Recently two z ∼ 6 QSOs without dust were detected, which indicates that these objects are probably first-generation QSOs forming in an essentially dust-free environment (Jiang et al 2010).…”