Imperial College Astrophysics Consolidated Grant 2016-2019

Lead Research Organisation: Imperial College London
Department Name: Dept of Physics

Abstract

Our research in Astrophysics includes the
areas of cosmology (the study of the Universe), the most distant
galaxies, exoplanets (planets around other stars), and gravitational
waves (distortion of space-time predicted by Einstein but so far not
detected). This work will make a contribution towards answering some
of the greatest questions that can be posed, including: can we find
signs of life outside the solar system? and what is the fate of the
Universe? Our work involves a combination of theory and
observations. We use cutting-edge facilities such as the Planck and
Herschel satellites, and LISA Pathfinder (to be launched in 2015), and
we also develop the theory and technology that will lead to proposals for the
development of the next generation of satellites and experiments.

Our understanding of the nature of the Universe has changed profoundly
over the past 20 years, since it was discovered that the expansion of
the Universe is accelerating, and as experiments, primarily those
observing the cosmic microwave background, have allowed the accurate
measurement of the parameters describing the Universe - the
proportions of ordinary matter (atoms), dark matter, and dark energy,
and the current rate of expansion. Dark matter clumps gravitationally
and outweighs ordinary matter by a factor 5, but what it consists of
is unknown. The even greater mystery is dark energy, which is causing
the acceleration of the Universe, and which dominates the mass-energy
budget. Our work in cosmology takes different approaches to answering
these problems. But the common theme in our research is the
understanding that advances will come through improved experiments
that measure quantities (cosmological distances, the rate of
expansion) more accurately. The experiments rely on better technology
(e.g. measurements of polarisation of the cosmic microwave
background), better understanding of the physics under study (the
properties of supernovae used to measure cosmological distances), and
better data analysis techniques that improve the precision and
accuracy of the results (applying rigorously the Bayesian formalism to
complex large datasets).

No less profound for humankind has been the discovery, again over the
past 20 years, of planets around many of the nearest stars in our
galaxy, and the first characterisation of other stellar
systems. If the ultimate goal is to discover life on other planets
this will be achieved through successive advances in understanding
how different types of planet (rocky/gaseous, large/small) form around
different types of star (old/young, active/inactive, hot/cool) at
different radial separations, and of how the star over its lifetime
can affect the conditions on its planets. Our work in this area
includes theoretical work to understand the mechanisms by which
planets form, as well as developing a deeper understanding of stellar
variability and how this can subtly bias measurements of the
atmospheres of planets (possibly leading to eroneous conclusions), as
well as influence the habitability of planets.

A consequence of Einstein's 1915 theory of general relativity, which
describes the curvature of space-time due to mass, is that massive
objects undergoing acceleration radiate energy in the form of
gravitational waves, propagating the signal of the change of curvature
at the speed of light. Gravitational waves have yet to be detected,
but their detection is one of the great goals of physics. The effect
is extremely subtle, so measurements in space away from sources of
vibration and the influence of the Earth are called for. Our research
on gravitational waves centres on contributing to the development of
technologies for use in the planned European Space Agency mission LISA
(not expected to launch before 2030), and analysis of data from the
LISA Pathfinder mission, to be launched in 2015, that will test
prototypes of these technologies.

Planned Impact

ATOMIC SPECTROSCOPY

Pickering provides atomic data needed in industrial analytical
applications. We were part of a 4 year EU Marie Curie Research
Training Network GLADNET for studies of glow discharge (GD). GD
spectroscopy is used by industry to analyse very thin (few nm) layers
found in manufacturing processes and the development of new
materials. Interested industrial sectors include life sciences, automobile
manufacturing, nano-technology and thin films. Collaborations
continue.

Fourier Transform spectroscopy has applications in non-STFC domains,
providing a rich opportunity for Knowledge Transfer. Pickering runs
the Tropospheric Airborne Fourier Transform Spectrometer (TAFTS)
instrument. TAFTS is the first far-infrared spectrometer capable of
high resolution far IR tropospheric in situ measurements. These data
are revealing the role of water vapour and cirrus clouds in the
regulation of the Earth's climate. This ongoing work is led by
Pickering.

APPLICATION OF ASTRONOMICAL ALGORITHMS

Roberto Trotta is working toward applying statistical
and data analysis methods developed for astrophysical research to the
problem of road security. In collaboration with an industrial partner,
he is engaged in translating those tools for the analysis of
in-vehicle monitoring systems data. Such data constitute a unique
testbed for a novel data analysis technology aimed at improving road
safety, refining car manufacturers' understanding of the actual
behaviour and performance of their vehicles often in challenging,
off-road conditions or poorly mapped areas, evaluating drivers'
behaviour and improving their safety. This work is funded under a
STFC/EPSRC Impact Acceleration Award.

Blackford Analysis (Alan Heavens) is a spin-off company that has
patented and markets astronomical algorithms involving the handling of
large datasets for imaging and other applications. Applications
include medical and security sectors.

OUTREACH

We engage in a wide range of public activities, including school
visits, exhibits, public lectures, a blog (by Andrew Jaffe), and media
appearances and interviews. For example, we had a lead role in the
Herschel (2012) and Planck (2013) stands at the Royal Society Summer
Exhibition, and the Astrophysics group has hosted two recent
large public-engagement activities: the ''Big Question'' series of
debates, and a series of talks "The sensual Universe - astrophysics
for the five senses''. Two members of the Astrophysics group
published popular science books in the last year. Dave Clements
published "Infrared Astronomy - seeing the heat" drawing on his
research work using Herschel satellite data. Roberto Trotta published
"The Edge of the Sky: All you Need to Know about the
All-There-Is". The book was named one of the "Best Science Books
2014" (by brainpickings.org, Scientific American Cocktail Party
Physics blog and The Huffington Post book blog). The "Edge of the
Sky" endeavours to explain the beauty and mystery of the Universe
(the "All-There-Is") using only the most common thousand words in
English. For his book Trotta was named one of the 100 Global
Thinkers 2014 (Foreign Policy, Nov/Dec 2014) for "junking astronomy
jargon".

We will continue to engage a wide cross section of the public with
follow-up series to our successful "Big Questions'' and "The sensual Universe" series.
In the last year, group members
have given about 30 public talks to an estimated total audience of 4500. We
will expand these activities through involvement with other bodies
such as the Hay Festival, the Royal Observatory Greenwich (ROG), the
Science Museum, the Dana Centre and the Royal Institution.

Publications

10 25 50

publication icon
Ding M (2020) Measurements of the Hyperfine Structure of Atomic Energy Levels in Co ii in The Astrophysical Journal Supplement Series

publication icon
Duivenvoorden S (2019) Have we seen all the galaxies that comprise the cosmic infrared background at 250 µm =? = 500 µm? in Monthly Notices of the Royal Astronomical Society

publication icon
Eales S (2018) The causes of the red sequence, the blue cloud, the green valley, and the green mountain in Monthly Notices of the Royal Astronomical Society

publication icon
GAMBIT Collaboration: (2017) Status of the scalar singlet dark matter model. in The European physical journal. C, Particles and fields

publication icon
GAMBIT Collaboration: (2019) Global analyses of Higgs portal singlet dark matter models using GAMBIT. in The European physical journal. C, Particles and fields

publication icon
Greaves J (2021) Addendum: Phosphine gas in the cloud deck of Venus in Nature Astronomy

 
Description 1. Astronomical observations over several decades have led to the conclusion that most of the matter in the universe is not ordinary atoms, but some unknown 'dark matter'. The exact nature of the dark matter is unknown, and pinning down its nature is extremely difficult. Scott leads the GAMBIT collaboration which employs sophisticated statistical methods to the narrow the possibilities. The idea is that the particle that makes up dark matter must simultaneously satisfy all the searches made to identify it, including for example the results of particle collider experiments at CERN, and the results of astronomical observations. In particular Scott led the most comprehensive analyses of 'supersymmetric and scalar singlet' dark matter models to date as well as an analysis with the IceCube Collaboration that produced the most sensitive tests yet of 'spin-dependent scattering' of dark matter.

2. Pickering makes measurements of the fundamental properties of atoms of different elements. These are used to compare against astronomical observations of stars, to help to infer the history of the formation and evolution of the Milky Way. Her team provided new atomic data for the Gaia-ESO survey (GES) leading to new understanding of Galactic Evolution, reported in over 75 papers by GES.

3. A recent approach to understanding dark matter is to use gravitational lensing. The path of photons (light particles) is bent by gravity, rather like refraction by glass, and so pictures of distant galaxies are subtly distorted by matter, including dark matter. By quantifying the distortion it is possible to infer the amount and properties of the dark matter. So this provides clues to what dark matter is. The effect is so subtle that to measure it accurately a new satellite called Euclid is being built. And the analysis requires new levels of statistical sophistication to tease out all the details. Heavens has been developing a new powerful method to achieve this. This is a long-term programme and the first stages were completed under this grant. This work is continuing in order to be ready for when Euclid is lunched in 2022 or 2023.

4. Astronomers are interested in making a complete census of all the different types of stars that exist, which will lead to a more complete understanding of how they form and evolve. Stars form from the gravitational collapse of clouds of gas. Their properties depend on their mass in a fundamental way (more massive = hotter). Below a certain mass the collapse balls of gas don't get hot enough for the nuclear burning of hydrogen (fusion), and the warm collapse clouds of gas are called brown dwarfs. These are very faint and difficult to find, so creating a large sample of brown dwarfs gives the possibility of studying this population of objects in detail. In this grant,
Warren created the first large homogeneous sample of L and T brown dwarfs, with 1361 members, with spectral types accurate to one sub-type, complete from L0 to T8.

5. At the interface between particle physics and pure mathematics lies the intriguing notion of cosmic topology, which gives rise to some very counterintuitive ideas. The universe could be smaller than it appears, and our picture could be analogous to the 'barber shop' phenomenon where with back to back mirrors you see repeated images of yourself receding into the distance. The study of cosmic topology aims to test whether we live in such a Universe. Using observations from the European Space Agency Planck satellite, Jaffe led the analysis of the geometry and topology of the large-scale structure of spacetime, putting the strongest limits to date on deviations from a homogeneous and isotropic cosmological model.
Exploitation Route The results of this research have been published in over 100 journal papers. These are well cited meaning that they are well read and are impacting on future research directions.

The impact beyond astronomy is dealt with elsewhere in this submission.
Sectors Digital/Communication/Information Technologies (including Software),Culture, Heritage, Museums and Collections

 
Description Blackford Analysis is a spin-out company co-founded in 2010 by Heavens using a statistical algorithm he invented for astronomy. It employs around 45 people in Edinburgh. Applications include medical and aerospace sectors. Heavens acts as technical advisor, providing continuous input directly related to algorithmic development undertaken under this grant. Pickering's spectroscopic research provides atomic data needed in industrial analytical applications in particular to analyse very thin (few nm) layers found in manufacturing processes and the development of new materials. Professor Trotta is an experienced science communicator, who develops novel ways of making abstract concepts in cosmology more tangible for the public at large, and seeks to make astronomy communication more inclusive. He has collaborated with chefs and human-machine interaction experts to design immersive experiences that convey cosmological ideas in a multi-sensory fashion. He has worked with the RNIB to develop new ways of bringing astronomy to the community of people with visual impairment. Between 2013-2017, he was an STFC Public Engagement Fellow, and he developed in this capacity the "Hands-on Universe" public outreach programme, which was long-listed for the National Co-ordinating Centre for Public Engagement Engage Awards 2016. His award-winning first book for the public, 'The Edge of the Sky' explains the Universe using only the most common 1,000 words in English. Professor Trotta was awarded the Annie Maunder Medal of the Royal Astronomical Society 2020 for his work in public engagement with cosmology.
First Year Of Impact 2016
Sector Aerospace, Defence and Marine,Healthcare,Manufacturing, including Industrial Biotechology,Culture, Heritage, Museums and Collections
Impact Types Cultural,Economic