About Me.

I'm currently a Reader in Cosmology at the Jodrell Bank Centre for Astrophysics at the University of Manchester. Before that, I was a lecturer and then a Reader at Queen Mary University of London from 2018 - 2022. I was a postdoc in the Radio Astronomy Lab and BCCP at UC Berkeley from 2017 - 2018, a NASA Postdoctoral Program fellow at JPL/Caltech from 2015 - 2017, and a postdoc in theoretical astrophysics at the University of Oslo from 2013 - 2015. I did my DPhil (PhD) in Astrophysics at the University of Oxford from 2010 - 2013, and my undergraduate degree in Physics with Astrophysics at the University of Manchester from 2006 - 2010. I'm originally from Stoke-on-Trent in the UK.

I'm also a Visiting Academic at the Centre for Radio Cosmology at the University of the Western Cape, a member of the SKA Cosmology Science Working Group (Core Team) and the HERA collaboration (Executive Board and lead of the Stats working group), a Full Member of the LSST Dark Energy Science Collaboration (where I was formerly co-convener of the Theory and Joint Probes working group), a member of the MeerKLASS radio cosmology collaboration, and was previously a member of the Planck Collaboration as part of the LFI Core Team while in Oslo. I am also a member of the Institute of Applied Data Science at Queen Mary.

Aside from my research interests in theoretical cosmology, I've also been involved in the open source movement. I began contributing to Ubuntu around 2005, before moving on to work on documentation for the GNOME project. My roles have included coordinating the writing of user and developer documentation, training new contributors, and supervising students for the project's Women's Outreach Program. I've also co-authored a couple of books on Ubuntu, published by No Starch Press in 2010 and 2012.

Research.

My area of expertise is in theoretical cosmology and general relativity. I'm fascinated by the lumpy, inhomogeneous nature of the Universe that we live in, and how structures evolve and interact on large scales. One of the biggest puzzles in this area is the (relatively) recent finding that the expansion of the Universe appears to be accelerating. This is a very curious result, and I'd like to get to the bottom of it!

Research interests

My technical interests are quite broad, and include:

• Cosmology with intensity maps of the redshifted hydrogen 21cm line

• General relativistic effects in large-scale structure observations and light propagation

• Using secondary anisotropies and spectral distortions of the CMB as cosmological probes

• Long-range peculiar velocity surveys and tests of gravity using the kinematic Sunyaev-Zel'dovich effect

• Observational tests of the Cosmological Principle, and the averaging and backreaction problems

• Bayesian statistics, stochastic processes, and computational physics

Publications.

This is a list of my scientific publications to date. You can also find listings on SPIRES, Google Scholar, and arXiv. My ORCID is 0000-0001-5668-3101. Some of the computer code used in these papers is available online.

Published and submitted papers are listed below, or you can skip to the list of white papers or conference proceedings .

1. Search for the Epoch of Reionisation with HERA: Upper Limits on the Closure Phase Delay Power Spectrum
   P. M. Keller et al.
   arXiv:2302.07969
2. The foreground transfer function for HI intensity mapping signal reconstruction: MeerKLASS and precision cosmology applications
   S. Cunnington, L. Wolz, P. Bull et al.
   arXiv:2302.07034
3. MeerKLASS simulations: Mitigating 1/f noise for auto-correlation intensity mapping measurements
   M. O. Irfan, Y. Li, M. G. Santos, P. Bull, J. Gu, S. Cunnington, K. Grainge, J. Wang
   arXiv:2302.02683
4. Statistical recovery of 21cm visibilities and their power spectra with Gaussian constrained realisations and Gibbs sampling
   F. Kennedy, P. Bull, M. J. Wilensky, S. Choudhuri
   arXiv:2211.05088
5. Bayesian jackknife tests with a small number of subsets: Application to HERA 21cm power spectrum upper limits
   M. J. Wilensky, F. Kennedy, P. Bull, J. S. Dillon, The HERA Collaboration
   arXiv:2210.17351
6. Characterization Of Inpaint Residuals In Interferometric Measurements of the Epoch Of Reionization
   M. Pagano et al.
   arXiv:2210.14927
7. Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations
   HERA Collaboration
   arXiv:2210.04912
8. What does an interferometer really measure? Including instrument and data characteristics in the reconstruction of the 21cm power spectrum
   A. Gorce et al.
   arXiv:2210.03721
9. Characterizing line-of-sight variability of polarized dust emission with future CMB experiments
   L. McBride, P. Bull, B. S. Hensley
   arXiv:2207.14213
10. HI intensity mapping with MeerKAT: power spectrum detection in cross-correlation with WiggleZ galaxies
    S. Cunnington, Y. Li et al.
    arXiv:2206.01579
11. Direct Optimal Mapping for 21cm Cosmology: A Demonstration with the Hydrogen Epoch of Reionization Array
    Z. Xu et al.
    ApJ 938, 128 (2022); arXiv:2204.06021
12. Measurements of the diffuse Galactic synchrotron spectral index and curvature from MeerKLASS pilot data
    M. O. Irfan, P. Bull, M. G. Santos et al.
    MNRAS 509, 4 (2022); arXiv:2111.08517
13. First Results from HERA Phase I: Upper Limits on the Epoch of Reionization 21 cm Power Spectrum
    HERA Collaboration et al.
    ApJ 925, 2 (2022); arXiv:2108.02263
14. HERA Phase I Limits on the Cosmic 21-cm Signal: Constraints on Astrophysics and Cosmology During the Epoch of Reionization
    HERA Collaboration et al.
    ApJ 924, 51 (2022); arXiv:2108.07282
15. Automated Detection of Antenna Malfunctions in Large-N Interferometers: A Case Study with the Hydrogen Epoch of Reionization Array
    D. Storer et al.
    Radio Science 57, 007376 (2021); arXiv:2109.12733
16. Spin-based removal of instrumental systematics in 21cm intensity mapping surveys
    N. McCallum, D. B. Thomas, P. Bull, M. L. Brown
    MNRAS 508, 4 (2021); arXiv:2107.08058
17. Cleaning foregrounds from single-dish 21cm intensity maps with Kernel Principal Component Analysis
    M. O. Irfan, P. Bull
    MNRAS 508, 3 (2021); arXiv:2107.02267
18. Effects of model incompleteness on the drift-scan calibration of radio telescopes
    B. K. Gehlot, D. C. Jacobs, J. D. Bowman et al.
    MNRAS 506, 3 (2021); arXiv:2104.12240
19. A Real Time Processing System for Big Data in Astronomy: Applications to HERA
    P. La Plante, P. K. G. Williams, M. Kolopanis et al.
    Astron. Comput. 36 (2021) 100489; arXiv:2104.03990
20. Validation of the HERA Phase I Epoch of Reionization 21 cm Power Spectrum Software Pipeline
    HERA Collaboration (J. E. Aguirre et al.)
    ApJ 924, 85 (2022); arXiv:2104.09547
21. Methods of Error Estimation for Delay Power Spectra in 21cm Cosmology
    J. Tan, A. Liu, N. Kern et al.
    ApJS 255, 26 (2021); arXiv:2103.09941
22. Statistical recovery of the BAO scale from multipoles of the beam-convolved 21cm correlation function
    F. Kennedy, P. Bull
    MNRAS 506, 2 (2021); arXiv:2103.08568
23. Patterns of primary beam non-redundancy in close-packed 21cm array observations
    S. Choudhuri, P. Bull, H. Garsden
    MNRAS 506, 2 (2021); arXiv:2101.02684
24. HI intensity mapping with MeerKAT: Calibration pipeline for multi-dish autocorrelation observations
    J. Wang, M.G. Santos, P. Bull et al.
    MNRAS 505, 3 (2021); arXiv:2011.13789
25. Searching for dark energy in the matter-dominated era
    P. Bull, M. White, A. Slosar
    MNRAS 505, 2 (2021); arXiv:2007.02865
26. Observing relativistic features in large-scale structure surveys -- II: Doppler magnification in an ensemble of relativistic simulations
    L. Coates, J. Adamek, P. Bull, C. Guandalin, C. Clarkson
    MNRAS 504, 3 (2021); arXiv:2011.12936
27. Observing relativistic features in large-scale structure surveys -- I: Multipoles of the power spectrum
    C. Guandalin, J. Adamek, P. Bull, C. Clarkson, L.R. Abramo, L. Coates
    MNRAS 501, 2 (2021); arXiv:2009.02284
28. DAYENU: A Simple Filter of Smooth Foregrounds for Intensity Mapping Power Spectra
    A. Ewall-Wice et al.
    MNRAS 500, 4 (2021); arXiv:2004.11397
29. Understanding the HERA Phase I receiver system with simulations and its impact on the detectability of the EoR delay power spectrum
    HERA Collaboration (N. Fagnoni et al.)
    MNRAS 500, 1 (2021); arXiv:1908.02383
30. Imaging and Modeling Data from the Hydrogen Epoch of Reionization Array
    C. Carilli et al.
    ApJS 247, 2 (2020)
31. Redundant-Baseline Calibration of the Hydrogen Epoch of Reionization Array
    J.S. Dillon et al.
    MNRAS 499, 4 (2020); arXiv:2003.08399
32. Absolute Calibration for the Hydrogen Epoch of Reionization Array and Its Impact on the 21 cm Power Spectrum
    HERA Collaboration (N.S. Kern et al.)
    ApJ 890, 122 (2020); arXiv:1910.12943
33. Mitigating Internal Instrument Coupling II: A Method Demonstration with the Hydrogen Epoch of Reionization Array
    HERA Collaboration (N.S. Kern et al.)
    ApJ 888, 70 (2020); arXiv:1909.11733
34. The HERA-19 Commissioning Array: Direction-dependent Effects
    HERA Collaboration (S. Kohn et al.)
    ApJ 882, 58 (2019); arXiv:1802.04151
35. Core Cosmology Library: Precision Cosmological Predictions for LSST
    LSST Dark Energy Science Collaboration (incl. P. Bull)
    ApJS 242, 2 (2019); arXiv:1812.05995
36. Cosmology with Phase 1 of the Square Kilometre Array; Red Book 2018: Technical specifications and performance forecasts
    Square Kilometre Array Cosmology Science Working Group (incl. P. Bull)
    PASA 37, E007; arXiv:1811.02743
37. Testing General Relativity with the Doppler magnification effect
    S. Andrianomena, C. Bonvin, D. Bacon, P. Bull, C. Clarkson, R. Maartens, T. Moloi
    MNRAS 488, 3759 (2019); arXiv:1810.12793
38. Fundamental Physics with the Square Kilometre Array
    A. Weltman, P. Bull, S. Camera et al.
    PASA 37, E002 (2020); arXiv:1810.02680
39. Model-independent curvature determination with 21cm intensity mapping experiments
    A. Witzemann, P. Bull, C. Clarkson, M. G. Santos, M. Spinelli, A. Weltman
    MNRAS 477, 1 (2018); arXiv:1711.02179
40. Mitigating complex dust foregrounds in future CMB polarization experiments
    B. Hensley, P. Bull
    ApJ 853, 127 (2018); arXiv:1709.07897
41. Priors on the effective Dark Energy equation of state in scalar-tensor theories
    Marco Raveri, Philip Bull, Alessandra Silvestri, Levon Pogosian
    Phys. Rev. D 96, 083509 (2017); arXiv:1703.05297
42. A Galaxy-Halo Model for Multiple Cosmological Tracers
    Philip Bull
    MNRAS 471, 12 (2017); arXiv:1610.08948
43. Dipolar modulation in the size of galaxies: The effect of Doppler magnification
    Camille Bonvin, Sambatra Andrianomena, David Bacon, Chris Clarkson, Roy Maartens, Teboho Moloi, Philip Bull
    MNRAS 472, 4 (2017); arXiv:1610.05946
44. Spatial curvature endgame: Reaching the limit of curvature determination
    C. Danielle Leonard, Philip Bull, Rupert Allison
    Phys. Rev. D 94, 023502 (2016); arXiv:1604.01410
45. Reconstructing cosmic growth with kSZ observations in the era of Stage IV experiments
    David Alonso, Thibaut Louis, Philip Bull, Pedro G. Ferreira
    Phys. Rev. D 94, 043522 (2016); arXiv:1604.01382
46. Distinguishing screening mechanisms with environment-dependent velocity statistics
    Magnus Fagernes Ivarsen, Philip Bull, Claudio Llinares, David Mota
    Astron. Astrophys. 595 (2016) A40; arXiv:1603.03072
47. Beyond ΛCDM: Problems, solutions, and the road ahead
    Philip Bull, Yashar Akrami (Eds.) et al.
    Phys. Dark. Univ. 12, 56 (2016); arXiv:1512.05356
48. Extending cosmological tests of General Relativity with the Square Kilometre Array
    Philip Bull
    Astrophys. J 817 (2016) 26; arXiv:1509.07562
49. Weighing neutrinos with cosmic neutral hydrogen
    Francisco Villaescusa-Navarro, Philip Bull, and Matteo Viel
    Astrophys. J 814 (2015) 146; arXiv:1507.05102
50. A systematic study of Lyman-Alpha transfer through outflowing shells: Model parameter estimation
    Max Gronke, Philip Bull, and Mark Dijkstra
    Astrophys. J 812 (2015) 123; arXiv:1506.03836
51. Observational signatures of modified gravity on ultra-large scales
    Tessa Baker and Philip Bull
    Astrophys. J 811 (2015) 2, 116; arXiv:1506.00641
52. Ultra-large scale cosmology with next-generation experiments
    David Alonso, Philip Bull, Pedro G. Ferreira, Roy Maartens, and Mario G. Santos
    Astrophys. J 814 (2015) 145; arXiv:1505.07596
53. Cosmological performance of SKA HI galaxy surveys
    Sahba Yahya, Philip Bull, Mario G. Santos, Marta Silva, Roy Maartens, Patrice Okouma, and Bruce Bassett
    MNRAS 450, 2251 (2015); arXiv:1412.4700
54. Cross-correlating 21cm intensity maps with Lyman Break Galaxies in the post-reionization era
    Francisco Villaescusa-Navarro, Matteo Viel, David Alonso, Kanan K. Datta, Philip Bull, and Mario G. Santos
    JCAP 1503 (2015) 03, 034; arXiv:1410.7393
55. A CMB Gibbs sampler for localized secondary anisotropies
    Philip Bull, Ingunn K. Wehus, Hans Kristian Eriksen, Pedro G. Ferreira, Unni Fuskeland, Krzysztof M. Gorski, and Jeffrey B. Jewell
    ApJS 219, 10 (2015); arXiv:1410.2544
56. Blind foreground subtraction for intensity mapping experiments
    David Alonso, Philip Bull, Pedro G. Ferreira, and Mario G. Santos.
    MNRAS 447, 400 (2015); arXiv:1409.8667
57. Quintessence in a quandary: On prior dependence in dark energy models
    David J. E. Marsh, Philip Bull, Pedro G. Ferreira, and Andrew Pontzen
    Phys. Rev. D 90 (2014) 10, 105023; arXiv:1406.2301
58. Late-time cosmology with 21cm intensity mapping experiments
    Philip Bull, Pedro G. Ferreira, Prina Patel, and Mario Santos
    Astrophys. J. 803 (2015) 1, 21; arXiv:1405.1452
59. A multi-level solver for Gaussian constrained CMB realizations
    D. S. Seljebotn, K. A. Mardal, J. B. Jewell, H. K. Eriksen, and P. Bull
    ApJS 210, 24 (2014); arXiv:1308.5299
60. What if Planck's Universe isn't flat?
    Philip Bull and Marc Kamionkowski
    Phys. Rev. D 87, 081301(R) (2013); arXiv:1302.1617
61. Local and non-local measures of acceleration in cosmology
    Philip Bull and Timothy Clifton
    Phys. Rev. D 85, 103512 (2012); arXiv:1203.4479
62. The isotropic blackbody CMB as evidence for a homogeneous universe
    Timothy Clifton, Chris Clarkson and Philip Bull
    Phys. Rev. Lett. 109, 051303 (2012); arXiv:1111.3794
63. The kSZ effect as a test of general radial inhomogeneity in LTB cosmology
    Philip Bull, Timothy Clifton and Pedro G. Ferreira
    Phys. Rev. D 85, 024002 (2012); arXiv:1108.2222

White Papers etc.

This is a list of (unpublished) white papers and technical reports that I have contributed to.

1. Modified Gravity and Dark Energy models Beyond w(z)CDM Testable by LSST
   LSST Dark Energy Science Collaboration (M. Ishak, T. Baker, P. Bull et al.)
   arXiv:1905.09687
2. Inflation and Early Dark Energy with a Stage II Hydrogen Intensity Mapping experiment
   Cosmic Visions 21 cm Collaboration (incl. P. Bull)
   arXiv:1810.09572
3. Line-Intensity Mapping: 2017 Status Report
   E. Kovetz et al.
   arXiv:1709.09066
4. MeerKLASS: MeerKAT Large Area Synoptic Survey
   Mario G. Santos (Ed.) et al.
   arXiv:1709.06099
5. Science Impacts of the SPHEREx All-Sky Optical to Near-Infrared Spectral Survey
   Olivier Doré, Michael W. Werner (Eds.) et al.
   arXiv:1606.07039

Conference Proceedings

This is a list of my conference proceedings.

1. Weak gravitational lensing with CO galaxies
   P. Bull, I. Harrison, E. Huff
   ASP Conf. Ser. 517 (2018) 803; arXiv:1806.08339
2. Cosmology from HI galaxy surveys with the SKA
   F. B. Abdalla, P. Bull, S. Camera, A. Benoit-Levy et al.
   PoS AASKA14 (2015) 017; arXiv:1501.04035
3. Cosmology from a SKA HI intensity mapping survey
   M. Santos, P. Bull, D. Alonso et al.
   PoS AASKA14 (2015) 019; arXiv:1501.03989
4. Cross correlation surveys with the Square Kilometre Array
   D. Kirk, F. B. Abdalla, A. Benoit-Levy, P. Bull, B. Joachimi
   PoS AASKA14 (2015) 020; arXiv:1501.03848
5. HI galaxy simulations for the SKA: number counts and bias
   M. Santos, D. Alonso, P. Bull, M. Silva, S. Yahya
   PoS AASKA14 (2015) 021; arXiv:1501.03990
6. Measuring baryon acoustic oscillations with future SKA surveys
   P. Bull, S. Camera, A. Raccanelli et al.
   PoS AASKA14 (2015) 024; arXiv:1501.04088
7. Cosmology on the Largest Scales with the SKA
   S. Camera, A. Raccanelli, P. Bull, D. Bertacca et al.
   PoS AASKA14 (2015) 025; arXiv:1501.03851
8. Measuring redshift-space distortion with future SKA surveys
   A. Raccanelli, P. Bull, S. Camera, C. Blake et al.
   PoS AASKA14 (2015) 031; arXiv:1501.03821
9. Foreground Subtraction in Intensity Mapping with the SKA
   L. Wolz, F. B. Abdalla, D. Alonso, C. Blake, P. Bull et al.
   PoS AASKA14 (2015) 035; arXiv:1501.03823
10. Synergy between the Large Synoptic Survey Telescope and the Square Kilometre Array
    D. Bacon, S. Bridle, F. B. Abdalla, M. Brown, P. Bull et al.
    PoS AASKA14 (2015) 145; arXiv:1501.03977
11. Euclid & SKA Synergies
    T. Kitching, D. Bacon, M. Brown, P. Bull et al.
    PoS AASKA14 (2015) 146; arXiv:1501.03978
12. 21cm Cosmology
    M. G. Santos, D. Alonso, P. Bull et al.
    Proc. IAU 306, CUP (2015)

Code.

I try to make all of my scientific code, or at least a substantial fraction of it, publicly available. This enables other people to reproduce and check my work if they want to. It also allows them to build off my code and do cool new things, rather than having to spend months solving problems that I may have already solved. That's the theory, anyway. Much of the code is written in Python, C++, and/or Fortran 90, and housed on GitHub or Gitlab.

Here are some of my publicly-available scientific codes:

Research Group.

I lead the HERA research group at JBCA, which focuses on statistical analysis of the HERA data, including power spectrum estimation and simulations. I also co-lead research groups in 21cm cosmology at UWC (with Prof. Mario Santos) and relativistic large-scale structure at QMUL (with Dr Chris Clarkson). The following is a list of current group members:

• Chris Addis

• Dr Jacob Burba

• Dr Hugh Garsden

• Katrine Glasscock

• Dr Carol Guandalin

• Dr Melis Irfan

• Fraser Kennedy

• Dr Piyanat Kittiwisit

• Geoff Murphy

• Dr Mike Wilensky

• Isabelle Ye

Former group members:

• Samir Choudhuri (PDRA 2019-2022), now faculty at IIT Madras.

Teaching.

I most recently taught SPA6311 Physical Cosmology (3rd year) at QMUL, and previously taught SPA5201 Physics Laboratory (2nd year). I also supervise projects for SPA6776 (Extended Independent Project) and SPA6913 (Physics Review Project), both in the 3rd year.

I was previously director of the new BSc and MSci programme in Physics with Data Science at QMUL, which launched in 2021.

Slides on Cosmology with SKA and Pathfinders from the 2016 INAF Scuola Lucchin summer school [20MB].

Slides on Gibbs sampling and Gaussian constrained realisations [7MB].

PhD students

(Includes students jointly supervised with others.)

• Isabelle Ye (PhD, QMUL, 2021-)

• Geoff Murphy (PhD, UWC, 2021-)

• Katrine Glasscock (PhD, QMUL, 2021-)

• Chris Addis (PhD, QMUL, 2021-)

• Fraser Kennedy (PhD, QMUL, 2019-)

• Caroline Guandalin (PhD, U. São Paulo, 2018-2021)

• Mikael Bull Steen (PhD, Oslo, 2014-2016)

Masters students

(Includes students jointly supervised with others.)

• Dimos Zografos (MSc, QMUL, 2020-2021)

• Kabelo Malapane (Masters, U. Western Cape, 2020-)

• Ankur Dev (Masters, QMUL, 2019-2020)

• Tim Oates (MSc, QMUL, 2019-2020)

• Alex Reedy (MSc, QMUL, 2019-2020)

• Matt Warner (Masters, QMUL, 2019-2020)

• Bradley Cooper-Barnard (MSc, QMUL, 2019)

• Thomas Murray (MSc, QMUL, 2019)

• Lisa McBride (Masters, SFSU, 2018)

• Magnus Fagernes Ivarsen (Masters, Oslo, 2015-16)

• Robert Olav Fauli (Masters, Oslo, 2014-15)

Summer research students

• Thomas Boyer (Masters, ENSTA Paris, 2021)

• Romain Pioch (Masters, ENSTA Paris, 2020)

• Kai-Hei Chan (undergrad, Hong Kong University, 2019)

• Peter Pan (undergrad, QMUL, 2019)

• Matthieu Vilatte (Masters, ENSTA Paris, 2019)

• Richelle Xavier (undergrad, Warwick, 2019)

• Shaunak Modak (undergrad, UC Berkeley, 2018)

• Duncan Rocha (undergrad, Harvey Mudd College, 2018)

• Louis Penafiel (undergrad, UC Riverside, 2017)

• Elizabeth Kimura (undergrad, Santa Monica College, 2017)

• Amanda Brown (undergrad, Princeton, 2016)

Outreach.

I've been involved in public outreach since the very start of my scientific career. Science is an extremely important part of the shared culture of humanity, and I believe that professional scientists have a duty to put their work into the public commons in an effective way, so that everyone can share in our discoveries.

I was the graduate public outreach coordinator at Oxford Astrophysics while I was a DPhil student there. We used to run open evenings for schools and the general public, using the Philip Wetton telescope on the roof of the Denys Wilkinson Building, and various cool Zooniverse projects.

We also initiated a rather successful annual space science festival called Stargazing Oxford, to tie in with the BBC's Stargazing Live programmes.

I've also been interviewed a few times here and there, and occasionally comment on science news stories (and opinion) in the press, as well as doing the odd podcast now and then.

The pinnacle of my media career, however, was when I appeared (for approximately one second) in the 2013 feature documentary Hawking. You can find me at around 40 minutes in, eating soup and waving my hands.

RHINO.

RHINO is a prototype 21cm global signal experiment that we are developing at Jodrell Bank Observatory. It's based on a large horn antenna operating at around 70 MHz (4m wavelength). While horns have to be gigantic at these wavelengths, they offer excellent control over the beam pattern, cross-polarisation, side- and backlobes etc.

Contact.

Please feel free to contact me about any aspect of my research, computer code, or otherwise. I prefer email wherever possible.

I'm also on Twitter, and some other things like that.