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Supernova dust: production and survival rates

Periodic Reporting for period 4 - SNDUST (Supernova dust: production and survival rates)

Reporting period: 2020-12-01 to 2022-05-31

The problem addressed by 694520 SNDUST was the origin of the dust component of the Universe, and specifically whether core-collapse supernovae (CCSNe), produced by massive stars, are the main sources of the interstellar dust found in galaxies.

The relevance of the SNDUST project for society is that interstellar dust is the source of the solid material that is incorporated into planets during the star formation process, as well as into lifeforms found on planets. Just as the origin of the elements is relevant to society, so also is the origin of the dust component of the Universe out of which life formed.

The objectives of the project were (A) (Theme 1) to determine observationally the quantities of dust formed by CCSNe, via optical and infrared observations of the gas and dust in supernova ejecta having ages ranging from a few hundred days to a few hundred years after the supernova events that produced them; (B) (Theme 2) to study theoretically the survivability of dust particles formed in supernova ejecta against destruction in reverse shocks caused by sputtering by gas particles and by grain-grain collisions, with the aim of determining the fraction of newly formed supernova dust particles that are injected into the interstellar medium of galaxies.

Conclusions: (1) We used the DAMOCLES code to analyse red-blue asymmetries in CCSN optical emission line profiles in order to measure their dust masses decades after outburst. For a sample of over 30 supernovae we showed that dust masses grow steadily with time, saturating at a mean value of 0.4 solar masses after 30 years. This value is sufficiently large to imply that CCSNe are the major stellar sources of dust in the Universe. (2) Our studies of the physics of dust destruction by supernova reverse shocks showed that grain sputtering and grain-grain collisions act together synergistically to destroy grains and that the survivability of dust particles is a strong function of grain radius. Larger grains, of the type deduced observationally to dominate in young remnants, have the highest survival rates.
Theme 1 (To determine observationally the quantities of dust formed by supernovae):
(1) Determination of the dust mass in the 340-yr old supernova remnant Cassiopeia A:
(a) from a multi-component dust analysis that used Herschel, Planck and Spitzer space
telescope infrared and submillimetre data (De Looze et al. 2017, MNRAS), and
(b) from a separate analysis of the dust content of Cas A by Bevan et al. (2017, MNRAS) that utilised the Monte Carlo dust radiative transfer code DAMOCLES to model the red-blue emission line asymmetries in the integrated optical spectra of the remnant. Satisfying agreement was found between the dust mass estimates obtained using these two entirely different methods (between 0.5-1.0 solar masses of dust in Cas A).
(c) A third independent method to determine the dust mass in Cas A was introduced by Niculescu-Duvaz et al. (2021, MNRAS), based on a comparison between far-IR forbidden line fluxes (unaffected by dust) with optical forbidden line fluxes (affected by dust obscuration) from the same ionic species. A dust mass between 0.5 and 1.0 solar masses was again obtained.

(2) Studies of dust and molecules in Supernova 1987A:
In Matsuura et al. (2017, MNRAS) we reported the detection in the 30-year old ejecta of Supernova 1987A of several cold molecular species, including CO, SiO and HCO+. Cigan et al. (2019, ApJ) showed that the dust in the ejecta was clumpy and asymmetrically distributed, filling the spaces where the distribution of CO line emission is fainter. The ALMA data showed a dust peak spatially coincident with a molecular hole seen in the ALMA CO J = 2 to 1 and SiO J = 5 to 4 images, consistent with a compact object (e.g. a pulsar) providing an additional source of heating at that location.

(3) Observations and modelling of supernova red-blue emission line asymmetries:
The analysis of red-blue emission line asymmetries seen in our spectra pf CCSNe up to 50 years after outburst was undertaken using the Monte Carlo dust radiative transfer code DAMOCLES (Bevan & Barlow 2016, MNRAS) in order to derive the quantities of dust present in the ejecta at each epoch of observation. This work culminated in a large paper by Niculescu-Duvaz et al. (2022), which presented dust masses measured at multiple epochs for 31 CCSNe and found that CCSN dust masses increased steadily over a 30-year timescale, saturating at a dust mass of 0.42 solar masses per supernova. This large mass implies that core-collapse supernovae are likely to be the dominant sources of dust in the early Universe, and may also be the most important stellar sources of dust in our local Universe today.

Theme 2: (SNR dust destruction):
For our calculations of dust grain destruction and growth in supernova remnant shocks, we decided to adopt and adapt for our use the AstroBEAR 3D hydrodynamic code( Team member F. Schmidt has introduced extensive enhancements to the AstroBEAR code, enabling it to treat a wide range of dust physics that had not been previously treated. Additionally, team member F. Kirchschlager wrote a post-processing code called Paperboats (Kirchschlager et al. 2019, MNRAS) which can take outputs from fluid-only hydrodynamic shock codes and use them to calculate dust destruction rates within shocks due to sputtering and grain-grain collisions, as well as dust grain growth rates due to gas accretion. In their comprehensive 2019 MNRAS paper Kirchschlager et al. used AstroBEAR and Paperboats to determine dust destruction rates in the reverse shock of the oxygen-rich supernova remnant Cassiopeia A. Our results showed that grain-grain collisions and sputtering are synergistic and that grain-grain collisions can play a crucial role in determining the surviving dust budget in supernova remnants. Kirchschlager et al. (in preparation) have since revised the treatment of grain-grain collisions, showing that an energy-based formulation is more appropriate than the standard velocity-based treatment that has been used by many previous workers. The implementation of this revised treatment of grain-grain collisions has the effect of reducing overall grain destruction rate, thus increasing dust survival rates.

A novel dust growth mechanism, namely the trapping within grains of impacting heavy element ions, had not previously been treated in any astrophysical calculations. This process was incorporated by us into the AstroBEAR and Paperboats codes by Kirchschlager et al. (2020, ApJ) who showed, compared to cases where the effect is neglected, that ion trapping increased the surviving masses of silicate dust by factors of up to two to four, depending on initial grain radii.
In her paper "Measuring dust in core-collapse supernovae with a Bayesian approach to line profile modelling" (MNRAS, 2018), A. Bevan applied Bayesian methods to the DAMOCLES Monte Carlo line radiative transfer code, which models the extent and shape of dust-affected supernova line profiles to determine the dust mass that has condensed, in addition to other properties of the dusty ejecta. Specifically, the paper presents the application of an affine invariant Markov Chain Monte Carlo ensemble sampler (EMCEE) to the DAMOCLES code in order to investigate the multidimensional parameter space rigorously and characterize the posterior probability distribution.
A plot of measured supernova ejecta dust masses as a function of time (days since explosion)