Research in astrophysics and cosmology at the University of Bristol
Lead Research Organisation:
University of Bristol
Department Name: Physics
Abstract
This proposal is for a grant to researchers in the HH Wills Physics Laboratory of the University of Bristol to investigate important questions in astrophysics and cosmology.
Much cosmology over the past few years has been based on investigations of clusters of galaxies, and the first project is to ensure the usefulness of clusters by making reliable measurements of their masses. This involves statistically rigorous investigations using several methods on samples of clusters derived from X-ray surveys. The clusters span a wide mass range and are seen over half the age of the Universe, so we also have to take into account how clusters change in time. The X-rays come from hot gas atmospheres held by the clusters - though low in density these atmospheres account for much of the mass of normal matter, and have other detectable effects, for example on the microwave background radiation. Cross-checks with non-X-ray techniques of mass measurement will ensure the reliability of our results.
On a smaller scale, we know that individual galaxies also change in time, but there is currently little understanding of how these changes depend on galaxy mass and environment: galaxies of different masses change at different rates, for example. How these processes act with and against one another to build the population of galaxies that we see today is unclear, but the multi-band optical data that we have accumulated allows tests of how galaxies change, and how star formation is fuelled, in the low-redshift Universe. At higher redshift we will look for proto-clusters, which contain the fastest-evolving galaxies, to understand how galaxies evolve during the early growth of the first massive structures.
Essentially all massive galaxies contain massive black holes at, or near, their centres, and a third project will investigate how such black holes are able to create intense central radiation sources, and will use the changing brightness and spectrum of X-rays from the inner parts of these systems to study black hole physics and the gas held close to the black hole.
A fourth project looks at how the tiny regions in the centres of individual galaxies, near the central black holes, can affect gas on the large scale - by stopping catastrophic cooling of the atmospheres of clusters of galaxies, and by gradually making cluster atmospheres more magnetic over cosmic time. It is widely believed that a feedback process, in which gas in clusters is reheated by the ejection of very hot, fast, gas from the regions near black holes is involved, at least in one heating mode. Our calculations have identified the population of sources responsible for this heating, and now want to understand how the process works for these objects.
The fifth project involves the maintenance and improvement of codes used to work with catalogues of astronomical objects. These codes are essential when dealing with modern astronomical data, and are used world-wide, so are of great importance to many astronomers, but require development to deal with the increasing size and complexity of astronomical data. Some of the codes have even found their way into public products like the Microsoft World-Wide Telescope, and others are finding creative uses beyond astronomy.
The final project is theoretical, and investigates the nature of the gas/dust disks around young stars in which planets form. As young pieces of planets collide and assemble into larger planets they can also destroy one another. Some of the dusty disks we see around young stars may show evidence of this destructive side of planet formation. The purpose of the high-performance computer calculations to be done in this project is to interpret the extreme examples of dusty disks to see if they are changing because of giant impacts between young planets. The results from the calculations will be compared with continuing observations of changing disk emission.
Much cosmology over the past few years has been based on investigations of clusters of galaxies, and the first project is to ensure the usefulness of clusters by making reliable measurements of their masses. This involves statistically rigorous investigations using several methods on samples of clusters derived from X-ray surveys. The clusters span a wide mass range and are seen over half the age of the Universe, so we also have to take into account how clusters change in time. The X-rays come from hot gas atmospheres held by the clusters - though low in density these atmospheres account for much of the mass of normal matter, and have other detectable effects, for example on the microwave background radiation. Cross-checks with non-X-ray techniques of mass measurement will ensure the reliability of our results.
On a smaller scale, we know that individual galaxies also change in time, but there is currently little understanding of how these changes depend on galaxy mass and environment: galaxies of different masses change at different rates, for example. How these processes act with and against one another to build the population of galaxies that we see today is unclear, but the multi-band optical data that we have accumulated allows tests of how galaxies change, and how star formation is fuelled, in the low-redshift Universe. At higher redshift we will look for proto-clusters, which contain the fastest-evolving galaxies, to understand how galaxies evolve during the early growth of the first massive structures.
Essentially all massive galaxies contain massive black holes at, or near, their centres, and a third project will investigate how such black holes are able to create intense central radiation sources, and will use the changing brightness and spectrum of X-rays from the inner parts of these systems to study black hole physics and the gas held close to the black hole.
A fourth project looks at how the tiny regions in the centres of individual galaxies, near the central black holes, can affect gas on the large scale - by stopping catastrophic cooling of the atmospheres of clusters of galaxies, and by gradually making cluster atmospheres more magnetic over cosmic time. It is widely believed that a feedback process, in which gas in clusters is reheated by the ejection of very hot, fast, gas from the regions near black holes is involved, at least in one heating mode. Our calculations have identified the population of sources responsible for this heating, and now want to understand how the process works for these objects.
The fifth project involves the maintenance and improvement of codes used to work with catalogues of astronomical objects. These codes are essential when dealing with modern astronomical data, and are used world-wide, so are of great importance to many astronomers, but require development to deal with the increasing size and complexity of astronomical data. Some of the codes have even found their way into public products like the Microsoft World-Wide Telescope, and others are finding creative uses beyond astronomy.
The final project is theoretical, and investigates the nature of the gas/dust disks around young stars in which planets form. As young pieces of planets collide and assemble into larger planets they can also destroy one another. Some of the dusty disks we see around young stars may show evidence of this destructive side of planet formation. The purpose of the high-performance computer calculations to be done in this project is to interpret the extreme examples of dusty disks to see if they are changing because of giant impacts between young planets. The results from the calculations will be compared with continuing observations of changing disk emission.
Planned Impact
Direct beneficiaries from the research will be our academic colleagues and interested members of the public, who will be exposed to the research results through our lectures, talks in schools, podcasts, press releases, WWW pages, appearances on radio and TV, and exhibits in and around Bristol. More indirectly, the public may be affected by advice given to local MPs or City Councillors (such as Mark Wright, who did a PhD in the Astrophysics Group a few years ago).
Commercial benefits have already been had from the TOPCAT work (projects with Microsoft Research). Spin-offs from the Fourier Transform spectrometer constructed for the radio telescope have benefitted BEAM and AlphaData. Research associated with the study of variability in active galaxies (Section 5) has formed the basis of a commercial contract, and provides some support for algorithm development relevant to LSST and SKA, as well as being of commercial benefit. This led recently to the company being awarded two major contracts, ensuring a flow of income for the next five to ten years, and also providing work for a local SME with whom we work on commercial-quality coding of our algorithms.
More generically, the sophisticated image and time-series analysis techniques used in our research can be applied to many problems. We will continue to work with the Atomic Force Microscopy group in the University to improve their imaging (as in recent imaging of moving DNA molecules), and are exploring the application of our techniques to medical imaging through the Clinical Research and Imaging Centre of the University.
Finally, the major economic output of this work will continue to be trained PhDs and PDRAs who mostly go into non-academic areas for their later careers. These careers have included local Government, the defence and security sector, plasma fusion research, meteorology, teaching, and finance.
Commercial benefits have already been had from the TOPCAT work (projects with Microsoft Research). Spin-offs from the Fourier Transform spectrometer constructed for the radio telescope have benefitted BEAM and AlphaData. Research associated with the study of variability in active galaxies (Section 5) has formed the basis of a commercial contract, and provides some support for algorithm development relevant to LSST and SKA, as well as being of commercial benefit. This led recently to the company being awarded two major contracts, ensuring a flow of income for the next five to ten years, and also providing work for a local SME with whom we work on commercial-quality coding of our algorithms.
More generically, the sophisticated image and time-series analysis techniques used in our research can be applied to many problems. We will continue to work with the Atomic Force Microscopy group in the University to improve their imaging (as in recent imaging of moving DNA molecules), and are exploring the application of our techniques to medical imaging through the Clinical Research and Imaging Centre of the University.
Finally, the major economic output of this work will continue to be trained PhDs and PDRAs who mostly go into non-academic areas for their later careers. These careers have included local Government, the defence and security sector, plasma fusion research, meteorology, teaching, and finance.
Organisations
- University of Bristol (Lead Research Organisation)
- University of Manchester (Collaboration)
- HARVARD UNIVERSITY (Collaboration)
- National Institute for Astrophysics (Collaboration)
- National Institute for Nuclear Physics (Collaboration)
- ESA - ESTEC (Collaboration)
- Max Planck Society (Collaboration)
- University of Turin (Collaboration)
- University of Toulouse (Collaboration)
- Sorbonne Universités (Collaboration)
- Western Washington University (Collaboration)
- Saclay Nuclear Research Centre (Collaboration)
- UNIVERSITY OF LEEDS (Collaboration)
- University of Arizona (Project Partner)
- Science Centre for Education Bangkok (Project Partner)
Publications
Selwood M
(2023)
Efficient analysis routines for single and double peaked Type 2 AGN spectra
in Monthly Notices of the Royal Astronomical Society
Phillipps S
(2023)
Galaxy And Mass Assembly (GAMA): the dependence of star formation on surface brightness in low-redshift galaxies
in Monthly Notices of the Royal Astronomical Society
Duggal Chetna
(2023)
Tracing jet-mode feedback in the wake of galaxy-sized radio sources
in American Astronomical Society Meeting Abstracts
Hancock S
(2023)
Extended corona models of X-ray reverberation in the AGN 1H 0707-495 and IRAS 13224-3809
in Monthly Notices of the Royal Astronomical Society
Pratt G
(2023)
Linking a universal gas density profile to the core-excised X-ray luminosity in galaxy clusters up to z ~1.1 (Corrigendum)
in Astronomy & Astrophysics
Mace M
(2023)
A chance of rain: investigating the effects of stochastic charging on the orbital dynamics and precipitation of nanodust in Saturn's rings
in Monthly Notices of the Royal Astronomical Society
Homan D
(2023)
The long-term broad-line responsivity in MKN 110
in Monthly Notices of the Royal Astronomical Society
Webbe R
(2023)
Variability in a low-mass active galactic nucleus: oscillation or eruption?
in Monthly Notices of the Royal Astronomical Society
Lewis T
(2023)
Isolating the extreme debris disc signature - explorations of eccentric extreme debris discs formed by giant impacts
in Monthly Notices of the Royal Astronomical Society
Giles P
(2022)
The XXL Survey. XLII. The LX - s v relation of galaxy groups and clusters detected in the XXL and GAMA surveys
in Monthly Notices of the Royal Astronomical Society
Nikolov N
(2022)
Solar-to-supersolar sodium and oxygen absolute abundances for a 'hot Saturn' orbiting a metal-rich star
in Monthly Notices of the Royal Astronomical Society
Crossett J
(2022)
The XXL Survey XLV. Linking the ages of optically selected groups to their X-ray emission
in Astronomy & Astrophysics
Logan C
(2022)
Chandra follow-up of the Hectospec Cluster Survey: Comparison of caustic and hydrostatic masses and constraints on the hydrostatic bias
in Astronomy & Astrophysics
Wilkes BJ
(2022)
X-ray astronomy comes of age.
in Nature
Smith D
(2022)
Galaxy And Mass Assembly: galaxy morphology in the green valley, prominent rings, and looser spiral arms
in Monthly Notices of the Royal Astronomical Society
De Propris R
(2022)
The ultraviolet upturn in field luminous red galaxies at 0.3 < z < 0.7
in Monthly Notices of the Royal Astronomical Society
Lovisari Lorenzo
(2022)
Scaling relations of clusters and groups, and their evolution
in arXiv e-prints
Garcia L
(2022)
HST/WFC3 transmission spectroscopy of the cold rocky planet TRAPPIST-1h
in Astronomy & Astrophysics
Andonie C
(2022)
A panchromatic view of infrared quasars: excess star formation and radio emission in the most heavily obscured systems
in Monthly Notices of the Royal Astronomical Society
Driver S
(2022)
Galaxy And Mass Assembly (GAMA): Data Release 4 and the z < 0.1 total and z < 0.08 morphological galaxy stellar mass functions
in Monthly Notices of the Royal Astronomical Society
Denman T
(2022)
Atmosphere loss in oblique Super-Earth collisions
in Monthly Notices of the Royal Astronomical Society
Campitiello M
(2022)
CHEX-MATE: Morphological analysis of the sample
in Astronomy & Astrophysics
Chainakun P
(2022)
Mapping the X-Ray Corona Evolution of IRAS 13224-3809 with the Power Spectral Density
in The Astrophysical Journal
Hasan P
(2022)
THE IAU-WOMEN IN ASTRONOMY WORKING GROUP AND INCLUSIVITY
in Revista Mexicana de Astronomía y Astrofísica Serie de Conferencias
Pratt G
(2022)
Linking a universal gas density profile to the core-excised X-ray luminosity in galaxy clusters up to z ~ 1.1
in Astronomy & Astrophysics
Wallbank A
(2022)
A systematic comparison of galaxy cluster temperatures measured with NuSTAR and Chandra
in Monthly Notices of the Royal Astronomical Society
Driver S
(2022)
An empirical measurement of the halo mass function from the combination of GAMA DR4, SDSS DR12, and REFLEX II data
in Monthly Notices of the Royal Astronomical Society
Akino D
(2022)
HSC-XXL: Baryon budget of the 136 XXL groups and clusters
in Publications of the Astronomical Society of Japan
Mikal-Evans T
(2022)
Diurnal variations in the stratosphere of the ultrahot giant exoplanet WASP-121b
in Nature Astronomy
Thorne J
(2022)
DEVILS: cosmic evolution of SED-derived metallicities and their connection to star formation histories
in Monthly Notices of the Royal Astronomical Society
Hashemizadeh A
(2022)
Deep extragalactic visible legacy survey (DEVILS): the emergence of bulges and decline of disc growth since z = 1
in Monthly Notices of the Royal Astronomical Society
Logan Crispin H. A.
(2022)
Chandra follow up of the Hectospec Cluster Survey: Comparison of Caustic and Hydrostatic Masses and Constraints on the Hydrostatic Bias
in arXiv e-prints
Phillipps S
(2022)
Centenary of a Centenary
in Astronomy & Geophysics
Davies L
(2022)
Deep Extragalactic VIsible Legacy Survey (DEVILS): evolution of the sSFR- M ? relation and implications for self-regulated star formation
in Monthly Notices of the Royal Astronomical Society
Thorne J
(2022)
Deep Extragalactic VIsible Legacy Survey (DEVILS): identification of AGN through SED fitting and the evolution of the bolometric AGN luminosity function
in Monthly Notices of the Royal Astronomical Society
Missaglia V
(2022)
Powerful Yet Lonely: Is 3C 297 a High-redshift Fossil Group?
in The Astrophysical Journal Supplement Series
Chainakun P
(2022)
Effects of the refractive index of the X-ray corona on the emission lines in AGNs
in Monthly Notices of the Royal Astronomical Society
Karademir G
(2022)
Galaxy And Mass Assembly (GAMA): z ~ 0 galaxy luminosity function down to L ~ 106 L? via clustering based redshift inference
in Monthly Notices of the Royal Astronomical Society
Lothringer JD
(2022)
UV absorption by silicate cloud precursors in ultra-hot Jupiter WASP-178b.
in Nature
Chainakun P
(2022)
Predicting the black hole mass and correlations in X-ray reverberating AGNs using neural networks
in Monthly Notices of the Royal Astronomical Society
Fu Guangwei
(2022)
The Hubble PanCET program: Emission spectrum of hot Jupiter HAT-P-41b
in arXiv e-prints
Wong I
(2022)
The Hubble PanCET Program: A Featureless Transmission Spectrum for WASP-29b and Evidence of Enhanced Atmospheric Metallicity on WASP-80b
in The Astronomical Journal
Guy Leanne P.
(2022)
Rubin-Euclid Derived Data Products: Initial Recommendations
in Zenodo id. 5836022
Alderson L
(2022)
A comprehensive analysis of WASP-17b's transmission spectrum from space-based observations
in Monthly Notices of the Royal Astronomical Society
Snios B.
(2022)
VizieR Online Data Catalog: Chandra & VLA obs. of 14 high-redshift QSOs (Snios+, 2021)
in VizieR Online Data Catalog
Duffy R
(2022)
The XXL Survey - XLVIII. X-ray follow-up of distant XXL clusters: masses, scaling relations, and AGN contamination
in Monthly Notices of the Royal Astronomical Society
Wethers C
(2022)
Galaxy and Mass Assembly (GAMA): The Weak Environmental Dependence of Quasar Activity at 0.1 < z < 0.35
in The Astrophysical Journal
Willis J
(2021)
Understanding X-ray and optical selection of galaxy clusters: a comparison of the XXL and CAMIRA cluster catalogues obtained in the common XXL-HSC SSP area
in Monthly Notices of the Royal Astronomical Society
Description | Some effects quantifying and explaining the differences in mass measurements of clusters of galaxies, made using different methods, have been reported. These have the potential to resolve some of the inconsistencies in cluster mass data. Issues arising in the understanding of relativistic flows from supermassive black holes in active galaxies have been exposed via a comparison of radio, infra-red, and X-ray data. A number of atmospheres of planets around distant stars have been studied, with implications for how the atmospheres behave. Extensive preparations for the upcoming launch of the Euclid satellite, in terms of preparing for science analysis of the data, have been published. |
Exploitation Route | All the results are available for use for research and education. Some of the software tools have other implications. Several members of the Group, supported by this grant, have been advising STFC, UKRI, ESA, and the Research Councils of Norway on science policy. |
Sectors | Education |
Description | Results from the award have been used in outreach events and for preparing podcasts. |
First Year Of Impact | 2020 |
Sector | Education |
Impact Types | Cultural,Societal |
Description | Research in Astrophysics at The University of Bristol |
Amount | £1,174,289 (GBP) |
Funding ID | ST/V000454/1 |
Organisation | Science and Technologies Facilities Council (STFC) |
Sector | Public |
Country | United Kingdom |
Start | 04/2021 |
End | 03/2024 |
Title | TOPCAT |
Description | TOPCAT is the most-used astronomical catalogue handling tool. It is extensively used to handle Gaia data and to create exploration plots of stellar populations, as well as in many other astronomical applications. It is also used for education in astronomical methods in the UK, Africa, and elsewhere. The underlying libraries are also used extensively for software developments. |
Type Of Material | Improvements to research infrastructure |
Provided To Others? | Yes |
Impact | Extensively used world-wide. |
URL | http://www.star.bris.ac.uk/~mbt/topcat/ |
Title | STILTS |
Description | Starlink Tables Infrastructure Library Tool Set: software for handling tabular data in many formats, including methods compliant with Virtual Observatory protocols. |
Type Of Material | Data handling & control |
Year Produced | 2010 |
Provided To Others? | Yes |
Impact | Used in many astronomical databases; potential uses for other complicated databases. |
Title | TOPCAT |
Description | Tool for operations on catalogues and tables: general catalogue comparison/selection tool, much used by astronomers world-wide. |
Type Of Material | Data handling & control |
Year Produced | 2011 |
Provided To Others? | Yes |
Impact | Extensible to many table-based datasets where matching of entries is required. Has been used on experimental basis for medical work, for example. |
Description | CHeCS |
Organisation | Harvard University |
Department | Harvard-Smithsonian Center for Astrophysics |
Country | United States |
Sector | Academic/University |
PI Contribution | Working together on cluster sample |
Collaborator Contribution | Working together on cluster sample |
Impact | Publications |
Start Year | 2018 |
Description | CHeCS |
Organisation | University of Turin |
Country | Italy |
Sector | Academic/University |
PI Contribution | Working together on cluster sample |
Collaborator Contribution | Working together on cluster sample |
Impact | Publications |
Start Year | 2018 |
Description | CHeCS |
Organisation | Western Washington University |
Country | United States |
Sector | Academic/University |
PI Contribution | Working together on cluster sample |
Collaborator Contribution | Working together on cluster sample |
Impact | Publications |
Start Year | 2018 |
Description | DARA |
Organisation | University of Leeds |
Department | School of Physics and Astronomy |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Birkinshaw was the Unit 1 leader (Zambia) for DARA courses from 2019 onwards, with the 2021 instruction being given entirely online. |
Collaborator Contribution | U. Leeds was the primary grant-holder for the series of awards maintaining this activity. Many national and international universities were and are involved. |
Impact | Many African students introduced to radio astronomy techniques, leading a number on to advanced education in astronomy and roles in the SKA and other major projects. Some spinoff companies (e.g., iDAM, in Ghana, from Bristol students) created by students from the DARA programme. |
Start Year | 2019 |
Description | GAIA team |
Organisation | ESA - ESTEC |
Country | Netherlands |
Sector | Public |
PI Contribution | Taylor has written much of the database access code for end-users, including major graphical display improvements. |
Collaborator Contribution | ESA satellite project to map star positions in the Galaxy: highly successful at generating vast database, requiring our database access methodology |
Impact | Extensive database for studies of structure of Galaxy. |
Start Year | 2009 |
Description | SKA Magnetism SWG |
Organisation | Max Planck Society |
Department | Max Planck Institute for Radio Astronomy |
Country | Germany |
Sector | Academic/University |
PI Contribution | Working with the team on issues to do with source populations, calibration across wide fields, radio galaxies |
Collaborator Contribution | Studies on wide-field polarisation imaging - paper submitted (Eyles et al.), and Big Data CDT student (Allotey) working on issues. |
Impact | Publications submitted and in preparation. |
Start Year | 2016 |
Description | XMM Heritage programme on Planck clusters |
Organisation | Harvard University |
Department | Harvard-Smithsonian Center for Astrophysics |
Country | United States |
Sector | Academic/University |
PI Contribution | Analysis of X-ray data; statistics |
Collaborator Contribution | Combination with other datasets |
Impact | Publications will be forthcoming |
Start Year | 2018 |
Description | XMM Heritage programme on Planck clusters |
Organisation | Max Planck Society |
Department | Max Planck Institute For Extraterrestrial Physics (MPE) |
Country | Germany |
Sector | Academic/University |
PI Contribution | Analysis of X-ray data; statistics |
Collaborator Contribution | Combination with other datasets |
Impact | Publications will be forthcoming |
Start Year | 2018 |
Description | XMM Heritage programme on Planck clusters |
Organisation | National Institute for Astrophysics |
Department | Bologna Observatory |
Country | Italy |
Sector | Public |
PI Contribution | Analysis of X-ray data; statistics |
Collaborator Contribution | Combination with other datasets |
Impact | Publications will be forthcoming |
Start Year | 2018 |
Description | XMM Heritage programme on Planck clusters |
Organisation | National Institute for Nuclear Physics |
Department | National Institute for Nuclear Physics - Milano |
Country | Italy |
Sector | Academic/University |
PI Contribution | Analysis of X-ray data; statistics |
Collaborator Contribution | Combination with other datasets |
Impact | Publications will be forthcoming |
Start Year | 2018 |
Description | XMM Heritage programme on Planck clusters |
Organisation | Saclay Nuclear Research Centre |
Department | Service d'Astrophysique |
Country | France |
Sector | Academic/University |
PI Contribution | Analysis of X-ray data; statistics |
Collaborator Contribution | Combination with other datasets |
Impact | Publications will be forthcoming |
Start Year | 2018 |
Description | XMM Heritage programme on Planck clusters |
Organisation | Sorbonne Universités |
Country | France |
Sector | Academic/University |
PI Contribution | Analysis of X-ray data; statistics |
Collaborator Contribution | Combination with other datasets |
Impact | Publications will be forthcoming |
Start Year | 2018 |
Description | XMM Heritage programme on Planck clusters |
Organisation | University of Manchester |
Department | School of Physics and Astronomy Manchester |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Analysis of X-ray data; statistics |
Collaborator Contribution | Combination with other datasets |
Impact | Publications will be forthcoming |
Start Year | 2018 |
Description | XMM Heritage programme on Planck clusters |
Organisation | University of Toulouse |
Country | France |
Sector | Academic/University |
PI Contribution | Analysis of X-ray data; statistics |
Collaborator Contribution | Combination with other datasets |
Impact | Publications will be forthcoming |
Start Year | 2018 |
Title | TOPCAT and related software |
Description | TOPCAT and related libraries provide means of accessing, displaying, and comparing catalogue data from remote or local databases. The software is the predominant astronomical catalogue manipulation package. |
Type Of Technology | Software |
Year Produced | 2018 |
Open Source License? | Yes |
Impact | Used for Gaia and many other projects. New versions are frequently released. The most recent public release of TOPCAT is version 4.6-2, released 2 November 2018. |
URL | http://www.star.bris.ac.uk/~mbt/topcat/ |
Description | Radio interviews |
Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | Variety of radio interviews: BBC Radio 4, BBC Radio Bristol, Local radio |
Year(s) Of Engagement Activity | 2019 |