Support of the Astronomical Research of the Cavendish Astrophysics Group

Lead Research Organisation: University of Cambridge
Department Name: Physics

Abstract

This proposal requests support for the Cavendish Astrophysics (CA) group in Cambridge. Our research has a strong emphasis on observational astrophysics, backed by fundamental theoretical work, a substantial track-record in Bayesian data analysis, and extensive expertise in technologies that span the spectrum from radio to near-infrared wavelengths. We aim to work in a number of thematic areas where we have contributed significantly either experimentally or via leadership roles, or where we will be developing new technologies for next generation experiments in astrophysics.

Theme 1 - Galaxy formation and Evolution: we will exploit our access to new proprietary data from JWST's NIRSpec instrument and the MOONS multi-object
spectrograph to investigate the chemical enrichment of galaxies from the time they were formed, at Cosmic Dawn, through to more recent epochs. This will use new measurements of
galactic metallicities from redshifts 9 through 0.7, and will explore the impact of the galactic environment on the chemical evolution of galaxies and the extent to which
different feedback mechanisms, e.g., accretion from the intergalactic medium, play a role in this process.

Theme 2 - Optical/infrared technology and instrumentation: we will use our expertise in interferometric methods and precision motion control to
investigate methods for enhancing the scientific potential of high-resolution spectrographs. In one project we will prototype and test a new method for ultra-precise wavelength
calibration where long-term stability is crucial, and in a second we will test a new method for producing large diffraction gratings by combining lithography and wet etching of
single-crystal Silicon with a precision-guided laser head.

Theme 3 - Exoplanet discovery: we will build on our expertise in precision radial-velocity measurement to lead the search for Earth-like exoplanets.
We will perform the first analysis of data from the Terra Hunting Experiment, a 10-year survey of nearby stars with the HARPS-3 spectrograph at the Isaac
Newton Telescope using an in-depth characterisation of the instrument and new statistical techniques to reduce false detections arising from instrumental effects.
In a parallel study, we will combine data from the HARPS-N spectrograph with new data from the TESS satellite to fully characterise potential planets around nearby K dwarfs, using
new methods to remove spurious detections resulting from stellar instabilities which can easily mimic the signatures of low-mass planets.

Theme 4 - Bayesian methods: we will exploit our extensive heritage in Bayesian data analysis in two different arenas. On the theoretical front, we will investigate a new method for inference (``likelihood-free'' inference) in astrophysics where existing methods can be too compute-intensive. This combines Machine Learning with computational simulation and has the potential to revolutionise the analysis of massive next-generation datasets. Another study will use Bayesian methods for image reconstruction from data collected with optical/infrared synthesis arrays, where
it can be difficulty to imaging relatively large objects: we aim to develop new imaging algorithms to solve this problem.

Theme 5 - Epoch of Re-ionization: we will be working on two projects related to our technology leadership in low-frequency radio astronomy. First, we will develop the
data analysis pipeline and analyse the first data from REACH, an experiment designed to make the first reliable detection of neutral hydrogen (the 21cm signal) from the Cosmic Dawn and Epoch of Re-ionization. A second project will develop a new digitization platform for low frequency radio astronomy. This will exploit low cost hardware and timing protocols developed for other applications
to support the next generation of radio telescopes comprising many thousands of antenna distributed over very large areas.

Planned Impact

As well as our scientific colleagues (immediate, nationally and internationally), our research will benefit a much wider community,
spanning the commercial sector, policy makers in science and technology, and the public through our participation in specific
educational outreach projects as well as more general engagement activities for the interested public.

Impact to commercial and Industry sector:

Our experience in developing novel experimental techniques to address challenging astrophysical problems has frequently led to take-up by the
commercial sector. For example, our expertise in Bayesian data analysis (in particular for understanding microwave background datasets) has been
adopted by the Oil and Gas exploration sector for geophysical inversion and by the finance sector for market data analysis. Any company who has to
deal with inferential problems from massive data will likely benefit from our work in this area. Similarly, our
proposed work on a low cost digitization platform will likely reach a much wider community of radio-frequency engineers than those focused on astronomy alone.

Our research in optical/infrared instrumentation has two potential commercial ramifications. A new method for grating fabrication, if extendable to metre-class
dimensions, would have immediate commercial impact. Quite separately, the novel scheme for wavelength calibration of spectrographs we are proposing, might
be of interest for specialists in high precision metrology.

Commerce and industry also benefit more generally from the skilled and talented researchers that we train and develop. Many of our graduate students
and post-docs pursue careers outside the academic sector, where they bring advanced technical skills, as well as other ``softer'' transferable skills associated
with data assimilation, model-building, team-work, and presentation.

Public impact of proposed science programme:

Our work on exo-planetary systems is an area of particular public interest (both technically and socially) and our proposed programmes searching for Earth-like planets
will undoubtedly have very significant impact. This type of research resonates with deep questions as to our place in the Universe, and so has a unique tie to
policy makers in science and beyond.

Our work on the Epoch of Reionization via the REACH experiment represents a different type of societal impact. Here, the location of the experiment in South Africa has the
potential to impacts the local technical, economic and social climate. This fostering of South African colleagues, and concomitant knowledge exchange, is a
particularly powerful consequence of our international links.

Outreach and engagement activities:

A core strand of our research programme is support for educational and outreach activities. This has multiple foci. Tours of our observatory site allow
students and post-docs to inform the general public on both what we do, but also to explain the value of skilled research scientists
in the non-academic environment as key players in the UKs knowledge base and innovation community. Another strand prioritises high school students, where the
benefits range from a better understanding of the world we live in, through a stronger engagement in education (through science), to the development of technical
skills and broader career prospects. A key event which the Cavendish organises, and where our work features strongly is the annual ``Physics of Work'' exhibition at which
several thousand attend. This three-day event aims to stimulate interest and encourage wider participation in physics amongst 14- to 16-year-olds
by showcasing the many and varied ways in which physics is used in the wider world (http://outreach.phy.cam.ac.uk/programme/physicsatwork).

Publications

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