The origin of cosmic dust in galaxies

Informations projet

DustOrigin

N° de convention de subvention: 851622

DOI

10.3030/851622

Date de signature de la CE 19 Septembre 2019

Date de début 1 Septembre 2020

Date de fin 31 Août 2026

Financé au titre de

• EXCELLENT SCIENCE - European Research Council (ERC)

Coût total

€ 1 500 000,00

Contribution de l’UE

€ 1 500 000,00

Coordonné par

UNIVERSITEIT GENT
Belgium

Periodic Reporting for period 3 - DustOrigin (The origin of cosmic dust in galaxies)

Période du rapport: 2023-09-01 au 2025-02-28

Résumé du contexte et des objectifs généraux du projet

Cosmic dust grains (i.e. particles built up from heavy elements such as carbon, silicon, magnesium, iron) are responsible for the obscuration of roughly half of the starlight in the Universe. They also play a privileged role in regulating the conditions for future star formation, and can instigate massive flows of galactic material out into the intergalactic medium. So far, we lack the knowledge on how the majority of cosmic dust forms in galaxies, which impedes our understanding of how these galaxies evolve through time. With this ERC project, my group hopes to solve the ``origin of cosmic dust” problem.

Stars, as the engines that produce metals in the Universe, are considered to be an obvious site for dust formation. This ``stardust” is currently thought to be insufficient to account for all cosmic dust in the Universe. The build-up and growth of dust grains from metals available in the space in between the stars in galaxies has been proposed as an alternative dust production channel, but has not (yet) been backed up with a viable chemical formation route.

In this project we will study the origin of interstellar dust through a combination of different methods. With dust particles playing an important role in regulating the heating and cooling balance in interstellar clouds, and obscuring a large fraction of the light of young stars in these clouds, we want to understand how dust is formed in galaxies. A surprising result is the detection of large quantities of dust already present in the earliest generations of galaxies which is challenging in the current framework of galaxy formation and evolution.
Finally, since every human-being is made up of “stardust”, this project is tracing the very origins of life on Earth.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

Our DustOrigin ERC team is studying how interstellar dust is formed and destroyed in galaxies through various methods.
1. We perform laboratory tests at the LERMA (Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères) in Paris to study how the building blocks of dust grains (oxygen, carbon, …) interact with grain surfaces, which allows us to study how grains can grow in mass in interstellar clouds outside of the typical stellar environments where we already know that dust grains can form.
2. We study an extensive set of infrared observations to quantify the size and mass of dust present in the interstellar medium, and freshly formed dust in supernova remnants. Polarisation measurements of the dust emission - which trace the alignment and orientation of grains in the presence of magnetic fields - are particularly helpful to constrain the composition and size of dust grains, since dust particles will respond differently to the presence of a magnetic field depending on their size, shape and composition.
3. Supernova explosions are cataclysmic events, and their energetic shock waves propagate through a vast mass of interstellar material, in which the dust becomes prone to destruction upon passage of the supernova shock front. We model how efficiently interstellar dust is destroyed by the supernova forward shock under different circumstances, and what the impact is of the supernova reverse shock processing on the survival of freshly formed supernova dust in the ejecta.
4. We run an extensive set of sophisticated models that track the build-up of metals and dust in galaxies, and apply it to galaxies across cosmic time to study how the formation and destruction of dust properties varies with environment and time.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

Our DustOrigin team has already made significant progress beyond the state of the art on several fronts:
1. We have developed a new methodology that constrains the composition of grains based on polarisation measurements in multiple bands, which allowed us to infer that carbonaceous and silicate grains co-exist in a supernova remnant.
2. We have studied how the presence of magnetic fields influences the destruction of supernova dust in clumpy ejecta by the reverse shock. We found that - depending on the orientation of the shock front relative to the ejecta velocity - the presence of magnetic fields can boost the dust destruction efficiency due to the accelerated motion of grains around magnetic field lines.
3. Our team has analysed whether oxygen can be incorporated in grain surfaces under idealised circumstances in the laboratory. While we need some further tests to fully understand what is happening to the oxygen, we have inferred that small hydrocarbon grain surfaces are ideal catalysts for the formation of molecular hydrogen at dust temperatures above 20K, even up to 250K. This result was completely unexpected, and has important implications for the formation of molecular hydrogen as fuel for star formation in the first generations galaxies forming in the early Universe where dust temperatures are significantly higher than 20K.

In the second half of the project, we look forward to new exciting results on the following topics:
1. We are currently analysing several new JWST observations that have allowed us to identify new dusty structures in supernova remnant environments, which will give us new insights into how dust is forming in supernova remnants.
2. Laboratory insights into the incorporation of elements in grain surfaces under typical interstellar cloud conditions, and what species could form to account for the missing oxygen problem in the gas phase. Observations show that oxygen is significantly depleted from the gas phase, but known solid forms that contain O only account for ~60% of the oxygen missing from the gas phase.
3. Modelling of elemental abundances and scaling relations of dust mass, stellar mass, star formation rate for galaxies in the nearby and more distant Universe will give us unprecedented insights into the build-up of stars and metals in these galaxies, and how the dominant dust sources and sinks vary across cosmic time.