A stubbornly large mass of cold dust in the ejecta of Supernova 1987A

TL;DR

This study uses Herschel observations to confirm a large mass of cold dust in Supernova 1987A's ejecta, indicating supernovae significantly contribute to cosmic dust budgets.

Contribution

It provides new far-infrared data and refined dust mass estimates, supporting the presence of over half a solar mass of dust, larger than previous predictions.

Findings

Detected approximately 0.8 solar masses of dust in the ejecta.

Confirmed the dominance of cold dust with a temperature near a single value.

Supported supernovae as major dust sources in galaxies.

Abstract

We present new Herschel photometric and spectroscopic observations of Supernova 1987A, carried out in 2012. Our dedicated photometric measurements provide new 70 micron data and improved imaging quality at 100 and 160 micron compared to previous observations in 2010. Our Herschel spectra show only weak CO line emission, and provide an upper limit for the 63 micron [O I] line flux, eliminating the possibility that line contaminations distort the previously estimated dust mass. The far-infrared spectral energy distribution (SED) is well fitted by thermal emission from cold dust. The newly measured 70 micron flux constrains the dust temperature, limiting it to nearly a single temperature. The far-infrared emission can be fitted by 0.5+-0.1 Msun of amorphous carbon, about a factor of two larger than the current nucleosynthetic mass prediction for carbon. The observation of SiO molecules at early and late phases suggests that silicates may also have formed and we could fit the SED with a combination of 0.3 Msun of amorphous carbon and 0.5 Msun of silicates, totalling 0.8 Msun of dust. Our analysis thus supports the presence of a large dust reservoir in the ejecta of SN 1987A. The inferred dust mass suggests that supernovae can be an important source of dust in the interstellar medium, from local to high-redshift galaxies.