Lighting up the dark - the evolution of dust throughout cosmic time

Project Information

CosmicDust

Grant agreement ID: 647939

DOI

10.3030/647939

Project closed

EC signature date 7 April 2015

Start date 1 September 2015

End date 28 February 2021

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 789 713,75

EU contribution

€ 1 789 713,75

Coordinated by

CARDIFF UNIVERSITY
United Kingdom

Periodic Reporting for period 4 - CosmicDust (Lighting up the dark - the evolution of dust throughout cosmic time)

Reporting period: 2020-03-01 to 2021-02-28

Summary of the context and overall objectives of the project

After more than two decades of infrared astronomy, we still know very little about the origin and evolution of cosmic dust in galaxies, responsible for obscuring half of all starlight since the Big Bang. This obscured starlight is re-radiated in a region of the electromagnetic spectrum that is still relatively unexplored. Our view of the universe has been biased: we lack vital knowledge about the origin of cosmic dust, its evolution, and therefore the fuel for star formation of galaxies over recent cosmic history. The Herschel Space Observatory provides a unique opportunity to resolve this by revealing the 90% of dust too cold to be detected before, yet only a tiny fraction of the largest survey of the sky carried out with Herschel has been exploited.

This project will produce the first statistical census of cosmic dust in galaxies, the raw material of rocky planets and building blocks for life, and provide key insights into the quantity and properties of dust formed in exploding stars using datasets, tools and techniques that our group has developed, tested and has unique access to. Dust contains roughly half the heavy elements in the interstellar medium today, up to 70% at early epochs [77], and is responsible for obscuring almost half of the energy emitted by stars since the Big Bang. This light is re-emitted in the infrared (IR) and submillimetre (submm) regime, a region of the electromagnetic spectrum that was, until recently, relatively unexplored. After more than two decades of space-based IR astronomy, we arguably still know very little about the local Universe at these wavelengths. We lack vital knowledge about the evolution of the dust and gas content and therefore the fuel for star formation of galaxies over recent cosmic history; furthermore, the long-standing controversy over the origin of cosmic dust is still unsolved. Consequently, we cannot even begin to match our understanding of the visible universe with the little information we have on obscured, dusty galaxies over cosmic time.

CosmicDust aims to build the largest catalogue of dusty galaxies (a ‘census' of dust) and help uncover mysterious new classes of galaxies that appear dust-poor in visible light images, but actually contain huge quantities of dust. This project will ensure the the full potential of Herschel is realised, well in advance of the next generation of space telescopes.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Our team have released Herschel ATLAS data covering 1/80th of the entire sky to the community, consisting of hundreds and thousands of galaxies observed in a new wavelength regime. We have used this data to measure how much dust exists in galaxies in time slices looking back over the past billion years. We created a census of dust in over 15,000 galaxies finding fewer galaxies with high dust mass than predicted by models. This represents the largest measure of its kind.

We discovered a remarkable overdensity of actively-star forming galaxies (10-100x more than the Milky Way) located close to galaxies that existed a few billion years ago. Although a surprise, this finding is predicted by some galaxy formation theories. We also discovered two CO-dark galaxies with such extreme properties that they present a challenge to our understanding of the inner workings of galaxies. Herschel's ability to detect dust at all temperatures revealed the odd BADGR galaxies. These galaxies are odd in many different ways and appear to be similar to the first galaxies formed in the early universe; but crucially this population is close enough to study in detail. We used Earth and ground based telescopes to obtain the detailed images and spectra. We discovered that the dust and gas in these galaxies are indeed very different – they require heating rates that are 10-20 times lower than one would expect using their starlight alone, and have cold gas temperatures are lower than seen in other nearby galaxies.

We discovered dust in the aftermath of 39 stellar explosions, with a special subset containing a significant amount. We used a powerful statistical tool developed at Cardiff University and found the dust appears different to the typical dust seen in galaxies, the first time such a measurement has been attempted. We detected silica in two remnants: the material we use for concrete and glass was created in the explosions of massive stars. Using the clearest image of dust and gas in SN1987A with ALMA, we discovered hints that the hidden neutron star in the SN1987A system could be enshrouded within a dust cloud.

The CosmicDust team has produced 78 peer reviewed publications. We have reached ~150,000 members of the academic community via presentations, posters, invited talks, review articles and meetings/workshops. As recognition of the PI's standing, she was invited to a breakfast with the Welsh Science Minister, to discuss the role of academic researchers in addressing the skills shortage in the UK and Europe and was awarded an Ordinary Member of the British Empire (MBE) by Her Majesty The Queen. Press releases on our H-ATLAS data and potentially detecting the hidden neutron star in SN1987A reached more than 2M people, appearing in Nature Research Highlights.

This project has enabled academics and students funded by the EU to reach 2.5M+ members of the public. This has the following benefits (i) inspiring next generation of STEM enthusiasts/workers (ii) raising aspirations and profile of STEM to families and the public (iii) raising the profile of the EU and blue skies research around the World.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

We produced the largest statistical dust census of 15,000 plus galaxies and have released catalogues and maps including almost half a million galaxies. Using the Herschel data to peer back 8 billion years to the early universe, our team found initial indications that the universe may have been much dustier in the past than today. We obtained detailed images and spectra of enigmatic blue and dusty gas rich galaxies, discovering that these galaxies are very different. We created a new bayesian statistical model to follow the evolution of dust, metals, star formation and gas in galaxies to interpret our findings.

Our team are also aiming to resolve a long-standing controversy over the origin of cosmic dust: whether it is made by sun-like stars in their quiet death throes, or if it is much more violent, instead originating from massive stars that tear themselves apart at the end of their lives. We discovered 39 exploding stellar remnants containing lots of dust. Interestingly, a subset of these all contain rapidly rotating neutron stars resulting from massive star explosions, hinting that these may be important dust-producing systems. We showed that the dust properties in this subset are potentially different to dust observed in the space between stars in the Milky Way. We detected silica in two supernova remnants confirming that the materials for concrete and glass we use on Earth was originally created in the explosions of massive stars.

We used ALMA to produce the sharpest view ever taken of a supernova to search for where the dust is located, and compared it with other important ingredients including carbon and silicon, to trace the coolest debris after the explosion that occurred over 30 years ago. In doing so we discovered hints that a hidden neutron star in the SN1987A system could be enshrouded within a dust cloud, tantalising evidence that the neutron star exists.

Multiwavelength view of SN1987A created by our team appeared in Nature Astronomy by Alak 2016

Discovery: violent death of a supernova creates silica - the chemical found in sand and glass.