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Black Hole

Lensing of space time around a black hole. At Oxford we study black holes observationally and theoretically on all size and time scales - it is some of our core work.

Credit: ALAIN RIAZUELO, IAP/UPMC/CNRS. CLICK HERE TO VIEW MORE IMAGES.

Prof. David Alonso

Associate Professor of Cosmology

Sub department

  • Astrophysics

Research groups

  • Beecroft Institute for Particle Astrophysics and Cosmology
  • Rubin-LSST
David.Alonso@physics.ox.ac.uk
Telephone: 01865 (2)288582
Denys Wilkinson Building, room 532B
  • About
  • Publications

Constraints on dark matter and astrophysics from tomographic γ-ray cross-correlations

Physical Review D: Particles, Fields, Gravitation and Cosmology American Physical Society 109 (2024) 103517

Authors:

Anya Paopiamsap, David Alonso, Deaglan Bartlett, Maciej Bilicki

Abstract:

We study the cross-correlation between maps of the unresolved 𝛾-ray background constructed from the 12-year data release of the Fermi Large-Area Telescope, and the overdensity of galaxies in the redshift range 𝑧≲0.4 as measured by the 2MASS photometric redshift survey and the WISE-SuperCOSMOS photometric survey. A signal is detected at the 8−10⁢𝜎 level, which we interpret in terms of both astrophysical 𝛾-ray sources, and weakly interacting massive particles (WIMP) dark matter decay and annihilation. The sensitivity achieved allows us to characterise the energy and redshift dependence of the signal, and we show that the latter is incompatible with a pure dark matter origin. We thus use our measurement to place an upper bound on the WIMP decay rate and the annihilation cross section, finding constraints that are competitive with those found in other analyses. Our analysis is based on the extraction of clean model-independent observables that can then be used to constrain arbitrary astrophysical and particle physics models. In this sense we produce measurements of the 𝛾-ray emissivity as a function of redshift and rest-frame energy 𝜖, and of a quantity 𝐹⁡(𝜖) encapsulating all WIMP parameters relevant for dark matter decay or annihilation. We make these measurements, together with a full account of their statistical uncertainties, publicly available.

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Constraints on dark matter and astrophysics from tomographic γ -ray cross-correlations

Physical Review D American Physical Society (APS) 109:10 (2024) 103517

Authors:

Anya Paopiamsap, David Alonso, Deaglan J Bartlett, Maciej Bilicki

Abstract:

<jats:p>We study the cross-correlation between maps of the unresolved <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>γ</a:mi></a:math>-ray background constructed from the 12-year data release of the Large-Area Telescope, and the overdensity of galaxies in the redshift range <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>z</c:mi><c:mo>≲</c:mo><c:mn>0.4</c:mn></c:math> as measured by the 2MASS photometric redshift survey and the WISE-SuperCOSMOS photometric survey. A signal is detected at the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mn>8</e:mn><e:mo>−</e:mo><e:mn>10</e:mn><e:mi>σ</e:mi></e:math> level, which we interpret in terms of both astrophysical <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>γ</g:mi></g:math>-ray sources, and weakly interacting massive particles (WIMP) dark matter decay and annihilation. The sensitivity achieved allows us to characterise the energy and redshift dependence of the signal, and we show that the latter is incompatible with a pure dark matter origin. We thus use our measurement to place an upper bound on the WIMP decay rate and the annihilation cross section, finding constraints that are competitive with those found in other analyses. Our analysis is based on the extraction of clean model-independent observables that can then be used to constrain arbitrary astrophysical and particle physics models. In this sense we produce measurements of the <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mi>γ</i:mi></i:math>-ray emissivity as a function of redshift and rest-frame energy <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mi>ϵ</k:mi></k:math>, and of a quantity <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>F</m:mi><m:mo stretchy="false">(</m:mo><m:mi>ϵ</m:mi><m:mo stretchy="false">)</m:mo></m:math> encapsulating all WIMP parameters relevant for dark matter decay or annihilation. We make these measurements, together with a full account of their statistical uncertainties, publicly available.</jats:p> <jats:sec> <jats:title/> <jats:supplementary-material> <jats:permissions> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2024</jats:copyright-year> </jats:permissions> </jats:supplementary-material> </jats:sec>
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Accuracy requirements on intrinsic alignments for Stage-IV cosmic shear

Open Journal of Astrophysics Maynooth Academic Publishing 7 (2024)

Authors:

Anya Paopiamsap, Natalia Porqueres, David Alonso, Joachim Harnois-Deraps, C Danielle Leonard

Abstract:

In the context of cosmological weak lensing studies, intrinsic alignments (IAs) are one of the most In the context of cosmological weak lensing studies, intrinsic alignments (IAs) are one of the most complicated astrophysical systematic\rev{s} to model, given the poor understanding of the physical processes that cause them. A number of modelling frameworks for IAs have been proposed in the literature, both purely phenomenological or grounded on a perturbative treatment of symmetry-based arguments. However, the accuracy with which any of these approaches is able to describe the impact of IAs on cosmic shear data, particularly on the comparatively small scales ([Math Processing Error]) to which this observable is sensitive, is not clear. Here we quantify the level of disagreement between the true underlying intrinsic alignments and the theoretical model used to describe them that can be allowed in the context of cosmic shear analyses with future Stage-IV surveys. We consider various models describing this "IA residual’', covering both physics-based approaches, as well as completely agnostic prescriptions. The same qualitative results are recovered in all cases explored: for a Stage-IV cosmic shear survey, a mis-modelling of the IA contribution at the [Math Processing Error] level produces shifts of [Math Processing Error] on the final cosmological parameter constraints. Current and future IA models should therefore aim to achieve this level of accuracy, a prospect that is not unfeasible for models with sufficient flexibility.
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The Simons Observatory: Combining cross-spectral foreground cleaning with multitracer $B$-mode delensing for improved constraints on inflation

(2024)

Authors:

Emilie Hertig, Kevin Wolz, Toshiya Namikawa, Antón Baleato Lizancos, Susanna Azzoni, Irene Abril-Cabezas, David Alonso, Carlo Baccigalupi, Erminia Calabrese, Anthony Challinor, Josquin Errard, Giulio Fabbian, Carlos Hervías-Caimapo, Baptiste Jost, Nicoletta Krachmalnicoff, Anto I Lonappan, Magdy Morshed, Luca Pagano, Blake Sherwin
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Cosmic shear with small scales: DES-Y3, KiDS-1000 and HSC-DR1

(2024)

Authors:

Carlos García-García, Matteo Zennaro, Giovanni Aricò, David Alonso, Raul E Angulo
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