Polarized foregrounds for measuring the cosmic microwave background
Lead Research Organisation:
University of Oxford
Department Name: Oxford Physics
Abstract
Observations of the cosmic microwave background radiation (CMB) have transformed our understanding of the universe over the past twenty years. The next big milestones will be the release of polarization data from the Planck satellite and ground-based CMB B-mode experiments. These give the possibility of detecting the curl-like component of the polarization of the CMB (the 'B-mode'), which will directly probe the physics of Inflation. One of the biggest problems as the sensitivity of CMB experiments gets ever better is removing the effects of foreground radiation, particularly from our Galaxy. This PhD project will use data from the C-Band All-Sky Survey (C-BASS) to definitively measure the synchrotron emission from the Galaxy in intensity and polarization, to improve foreground subtraction and hence significantly improve the sensitivity of current and up-coming CMB experiments.
The project will include the reduction and analysis of raw C-BASS data from both the Northern and Southern surveys with the aim of producing a consistent and well-calibrated all-sky map in both temperature and polarization. This new dataset will then be used in conjunction with Planck, WMAP and other CMB polarization data to provide accurate measurements of the CMB temperature and polarization spectra.
The project will include the reduction and analysis of raw C-BASS data from both the Northern and Southern surveys with the aim of producing a consistent and well-calibrated all-sky map in both temperature and polarization. This new dataset will then be used in conjunction with Planck, WMAP and other CMB polarization data to provide accurate measurements of the CMB temperature and polarization spectra.
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| ST/N504233/1 | 01/10/2015 | 31/03/2021 | |||
| 1804806 | Studentship | ST/N504233/1 | 01/10/2016 | 31/07/2021 | Richard Grumitt |
| Description | STFC Policy Internship |
| Geographic Reach | National |
| Policy Influence Type | Contribution to a national consultation/review |
| Impact | To date, the Science Capability Review resulted in a commitment in the 2018 Budget to create a new £50 million per year fund, to support joint projects between government and industry in areas such as health and cyber security. |
| Title | Novel CMB Component Separation |
| Description | I have developed a novel implementation of cosmic microwave background (CMB) component separation, using the No-U-Turn sampler developed by Hoffman and Gelman. Paper has been submitted to MNRAS, and I am currently working through the referee's report. |
| Type Of Material | Computer model/algorithm |
| Year Produced | 2019 |
| Provided To Others? | Yes |
| Impact | This new method offers significant performance improvements over previous implementations of Bayesian component separation. Whilst previous methods could only feasibly be applied to low resolution maps of the sky, the new method offers the potential to perform a full end-to-end Bayesian analysis of the CMB signal. It also applies hierarchical modelling to CMB component separation, which allows for more realistic modelling of diffuse emission without inflating the statistical uncertainty in the recovered CMB estimates. |
| URL | https://arxiv.org/abs/1910.14170 |
| Title | The C-Band All-Sky Survey (Northern Sky) |
| Description | Our research group has produced a unique dataset covering the northern sky in total intensity and polarisation. This provides vital information on the nature of low-frequency synchrotron emission, which will be key in planned next-generation studies of the CMB polarisation. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2018 |
| Provided To Others? | No |
| Impact | This dataset provides a clean view of the low-frequency sky, which can be reliably extrapolated to higher frequencies where we perform CMB observations. This will prove invaluable in future joint analyses of C-BASS with other CMB datasets, helping to reduce biases in any CMB analysis. This has already been quantified through simulations. |
| URL | https://academic.oup.com/mnras/article-abstract/480/3/3224/5059589?redirectedFrom=fulltext |
| Description | Stargazing Oxford |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Public/other audiences |
| Results and Impact | Assisted in organisation and running of Stargazing Oxford, the astrophysics department's primary outreach event. As such, this involves effort from most of the department. The department was opened to approximately 1000 visitors with a wide range of stalls and activities available. Each event received very positive feedback. |
| Year(s) Of Engagement Activity | 2017,2018,2019 |
| URL | https://www2.physics.ox.ac.uk/events/2019/01/26/stargazing-oxford-2019 |
| Description | Workshop for schoolchildren (Oxford) |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Schools |
| Results and Impact | Approximately 60 pupils attended a visit to the Physics department, where I helped lead a workshop on astrophysics. Students were engaged throughout the workshop, and teachers made requests for copies of the learning materials used in the workshop. |
| Year(s) Of Engagement Activity | 2017,2018 |