About

Jo Dunkley is a Professor of Physics & Astrophysical Sciences at Princeton University. She is involved in research within the Department of Astrophysical Sciences, focusing on astrophysics and cosmology. Her work includes studying the universe's fundamental properties, contributing to our understanding of cosmic phenomena. She is a member of the faculty and research community at Princeton, engaging in teaching, research, and departmental activities.

Research topics

• Astrophysics
• Physics
• Astronomy
• Optics
• Quantum mechanics
• Theoretical physics
• Classical mechanics
• Particle physics
• Statistics

Selected publications

• Disentangling the halo: joint model for measurements of the kinetic Sunyaev–Zeldovich effect and galaxy–galaxy lensing

  Monthly Notices of the Royal Astronomical Society · 2026-01-16 · 1 citations

  articleOpen access

  ABSTRACT We present the first joint analysis of the kinetic Sunyaev–Zeldovich (kSZ) effect with galaxy–galaxy lensing (GGL) for CMASS galaxies in the Baryon Oscillation Spectroscopic Survey. We show these complementary probes can disentangle baryons from dark matter in the outskirts of galactic haloes by alleviating model degeneracies that are present when fitting to kSZ or GGL measurements alone. In our joint kSZ + GGL analysis we show that the baryon density profile is well constrained on scales from 0.3 to 50 Mpc$\,h^{-1}$. With our well-constrained profile of the baryon density, we provide direct comparisons to simulations. For our model we find an outer slope of the baryon distribution that is shallower than predicted by some hydrodynamical simulations, consistent with enhanced baryonic feedback. We also show that not including baryons in a model for GGL can shift halo mass estimates by $\sim 20~{{\ \rm per\ cent}}$ compared to a model that includes baryons and is jointly fit to kSZ + GGL measurements. Our modelling code GGL and kSZ (glasz) is publicly available at https://github.com/James11222/glasz.

  PublisherDOI

• The Atacama Cosmology Telescope: DR6 Sunyaev-Zel’dovich Selected Galaxy Clusters Catalog

  The Open Journal of Astrophysics · 2026-01-27 · 2 citations

  articleOpen access

  We present the results of a search for galaxy clusters in the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) microwave sky maps covering 16293 square degrees in three frequency bands, using data obtained over the lifetime of the project (2008-2022). We report redshifts and mass estimates for 10040 clusters detected via their Sunyaev-Zel’dovich (SZ) effect with signal-to-noise greater than 4 at a 2.4 arcminute filter scale. The catalog includes 1180 clusters at redshifts greater than 1, and 123 clusters at redshifts greater than 1.5. Using a relation between cluster SZ signal and mass that is consistent with recent weak-lensing measurements, we estimate that clusters detected with signal-to-noise greater than 5 form a sample which is 90% complete for clusters with masses greater than <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mn>5</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>14</mml:mn> </mml:msup> </mml:mrow> </mml:math> MSun (measured within a spherical volume with mean density 500 times the critical density). El Gordo, a cluster found in an initial ACT survey of 755 square degrees, remains the most extreme cluster in mass and redshift; we find no cluster with a mass and redshift combination high enough to falsify the standard LCDM cosmology with Gaussian initial perturbations. We make public a variety of data products, including the full cluster candidate list, noise maps, and sky masks, along with our software for cluster detection and instructions for reproducing our cluster catalogs from the public ACT maps.

  PublisherDOI

• The Atacama Cosmology Telescope: A demonstration of CMB lensing measurement from daytime data

  arXiv (Cornell University) · 2025-11-13

  preprintOpen access

  We present a cosmic microwave background (CMB) lensing power spectrum analysis using daytime data (11am-11pm UTC) gathered by the Atacama Cosmology Telescope (ACT) over the period 2017-2022 (ACT Data Release 6). This dataset is challenging to analyze because the Sun heats and deforms the telescope mirror, complicating the characterization of the telescope. We perform more than one hundred null and consistency checks to ensure the robustness of our measurement and its compatibility with nighttime observations. We detect the CMB lensing power spectrum at 17$σ$ significance, with an amplitude $A_\textrm{lens} = 1.045 \pm 0.063$ with respect to the prediction from the best-fit Planck-ACT CMB power spectrum $Λ$CDM cosmology. In combination with the Dark Energy Spectroscopic Instrument (DESI) Baryon Acoustic Oscillation (BAO) data, this corresponds to a constraint on the amplitude of matter fluctuations $σ_8 = 0.826 \pm 0.027$. The analysis presented here is especially relevant for ground-based millimeter-wave CMB experiments at the Atacama site, paving the way for future analyses making use of both nighttime and daytime data to place tight constraints on cosmological parameters.

  PublisherOA PDFDOI

• The Atacama Cosmology Telescope: semi-analytic covariance matrices for the DR6 CMB power spectra

  Journal of Cosmology and Astroparticle Physics · 2025-05-01 · 8 citations

  articleOpen access

  Abstract The Atacama Cosmology Telescope Data Release 6 (ACT DR6) power spectrum is expected to provide state-of-the-art cosmological constraints, with an associated need for precise error modeling. In this paper we design, and evaluate the performance of, an analytic covariance matrix prescription for the DR6 power spectrum that sufficiently accounts for the complicated ACT map properties. We use recent advances in the literature to handle sharp features in the signal and noise power spectra, and account for the effect of map-level anisotropies on the covariance matrix. In including inhomogeneous survey depth information, the resulting covariance matrix prescription is structurally similar to that used in the Planck Cosmic Microwave Background (CMB) analysis. We quantify the performance of our prescription using comparisons to Monte Carlo simulations, finding better than 3% agreement. This represents an improvement from a simpler, pre-existing prescription, which differs from simulations by ∼ 16%. We develop a new method to correct the analytic covariance matrix using simulations, after which both prescriptions achieve better than 1% agreement. This correction method outperforms a commonly used alternative, where the analytic correlation matrix is assumed to be accurate when correcting the covariance. Beyond its use for ACT, this framework should be applicable for future high resolution CMB experiments including the Simons Observatory (SO).

  PublisherDOI

• Backlighting extended gas halos around luminous red galaxies: Kinematic Sunyaev-Zel’dovich effect from DESI Y1 and ACT data

  Physical review. D/Physical review. D. · 2025-11-07 · 12 citations

  articleOpen access

  The gas density profile around galaxies, shaped by feedback and affecting the galaxy lensing signal, is imprinted on the cosmic microwave background (CMB) by the kinematic Sunyaev-Zel'dovich effect (kSZ). We precisely measure this effect ($S/N\ensuremath{\approx}10$) via velocity stacking with 825,283 spectroscopically confirmed luminous red galaxies (LRG) from the Dark Energy Spectroscopic Instrument Year 1 (DESI Y1) survey, which overlap with the Atacama Cosmology Telescope (ACT) Data Release 6 temperature maps over $\ensuremath{\ge}4,000\text{ }\text{ }{\mathrm{deg}}^{2}$. We explore the kSZ dependence with various galaxy parameters and find no significant trend with redshift but clear trends with stellar mass and absolute magnitude in $g$, $r$, and $z$ bands. Our analysis suggests that the gas extends beyond the dark matter halo (99.5% confidence level, i.e., probability to exceed $(\mathrm{PTE})=0.005$). We find a tentative preference for hydrodynamical simulation models with stronger feedback that drives gas further out (Illustris $z=0.5$, $\mathrm{PTE}=0.37$) over weaker-feedback cases (IllustrisTNG $z=0.8$, $\mathrm{PTE}=0.045$), though with limited statistical significance. In all cases, a free multiplicative amplitude was fit to the simulated profiles, and further modeling work is required to firm up these conclusions. We find consistency between kSZ profiles around spectroscopic and photometric LRG, with comparable statistical power, thus increasing our confidence in the photometric analysis. Additionally, we present the first kSZ measurement around the DESI Y1 bright galaxy sample (BGS) and the emission-line galaxies (ELG) whose features match qualitative expectations. Finally, we forecast $S/N\ensuremath{\sim}50$ for future stacked kSZ measurements using data from the ACT, the DESI Y3, and the Rubin Observatory. These measurements will serve as an input for galaxy formation models and baryonic uncertainties in galaxy lensing.

  PublisherOA PDFDOI

• Cosmological limits on the neutrino mass sum for beyond-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">Λ</mml:mi><mml:mi>CDM</mml:mi></mml:math> models

  Physical review. D/Physical review. D. · 2025-04-17 · 10 citations

  articleOpen access

  The sum of neutrino masses can be measured cosmologically, as the sub-eV particles behave as “hot” dark matter whose main effect is to suppress the clustering of matter compared to a universe with the same amount of purely cold dark matter. Current astronomical data provide an upper limit on <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mo>∑</a:mo><a:msub><a:mrow><a:mi>m</a:mi></a:mrow><a:mrow><a:mi>ν</a:mi></a:mrow></a:msub></a:mrow></a:math> between 0.07–0.12 eV at 95% confidence, depending on the choice of data. This bound assumes that the cosmological model is <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mi mathvariant="normal">Λ</c:mi></c:mrow></c:math> Cold Dark Matter (<f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:mi mathvariant="normal">Λ</f:mi><f:mi>CDM</f:mi></f:math>), where dark energy is a cosmological constant, the spatial geometry is flat, and the primordial fluctuations follow a pure power law. Here, we update studies on how the mass limit degrades if we relax these assumptions. To existing data from the satellite we add new gravitational lensing data from the Atacama Cosmology Telescope, the new Type Ia supernova sample from the <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mrow><i:mi>Pantheon</i:mi><i:mo>+</i:mo><i:mtext>survey</i:mtext></i:mrow></i:math>, and baryonic acoustic oscillation (BAO) measurements from the Sloan Digital Sky Survey and the Dark Energy Spectroscopic Instrument. Using our fiducial data combination, described in the appendix, we find the neutrino mass limit is stable to most model extensions, with such extensions degrading the limit by less than 10%. We find a broadest bound of <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mrow><k:mo>∑</k:mo><k:msub><k:mrow><k:mi>m</k:mi></k:mrow><k:mrow><k:mi>ν</k:mi></k:mrow></k:msub><k:mo>&lt;</k:mo><k:mn>0.19</k:mn><k:mtext> </k:mtext><k:mtext> </k:mtext><k:mi>eV</k:mi></k:mrow></k:math> at 95% confidence for a model with dynamical dark energy, although this scenario is not statistically preferred over the simpler <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi mathvariant="normal">Λ</m:mi><m:mi>CDM</m:mi></m:math> model.

  PublisherOA PDFDOI

• Atacama Cosmology Telescope: Multiprobe cosmology with unWISE galaxies and ACT DR6 CMB lensing

  Physical review. D/Physical review. D. · 2025-04-09 · 12 citations

  articleOpen access

  We present a joint analysis of the cosmic microwave background (CMB) lensing power spectra measured from the Data Release 6 of the Atacama Cosmology Telescope (ACT) and PR4, cross-correlations between the ACT and lensing reconstruction and galaxy clustering from unWISE, and the unWISE clustering auto-spectrum. We obtain 1.5% constraints on the matter density fluctuations at late times parametrized by the best constrained parameter combination <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msubsup><a:mrow><a:mi>S</a:mi></a:mrow><a:mrow><a:mn>8</a:mn></a:mrow><a:mrow><a:mn>3</a:mn><a:mi mathvariant="normal">x</a:mi><a:mn>2</a:mn><a:mi>pt</a:mi></a:mrow></a:msubsup><a:mo>≡</a:mo><a:msub><a:mrow><a:mi>σ</a:mi></a:mrow><a:mrow><a:mn>8</a:mn></a:mrow></a:msub><a:mo stretchy="false">(</a:mo><a:msub><a:mrow><a:mi mathvariant="normal">Ω</a:mi></a:mrow><a:mrow><a:mi>m</a:mi></a:mrow></a:msub><a:mo>/</a:mo><a:mn>0.3</a:mn><a:msup><a:mrow><a:mo stretchy="false">)</a:mo></a:mrow><a:mrow><a:mn>0.4</a:mn></a:mrow></a:msup><a:mo>=</a:mo><a:mn>0.815</a:mn><a:mo>±</a:mo><a:mn>0.012</a:mn></a:mrow></a:math>. The commonly used <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msub><g:mi>S</g:mi><g:mn>8</g:mn></g:msub><g:mo>≡</g:mo><g:msub><g:mi>σ</g:mi><g:mn>8</g:mn></g:msub><g:mo stretchy="false">(</g:mo><g:msub><g:mi mathvariant="normal">Ω</g:mi><g:mi>m</g:mi></g:msub><g:mo>/</g:mo><g:mn>0.3</g:mn><g:msup><g:mo stretchy="false">)</g:mo><g:mn>0.5</g:mn></g:msup></g:math> parameter is constrained to <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:msub><l:mi>S</l:mi><l:mn>8</l:mn></l:msub><l:mo>=</l:mo><l:mn>0.816</l:mn><l:mo>±</l:mo><l:mn>0.015</l:mn></l:math>. In combination with baryon acoustic oscillation (BAO) measurements we find <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:msub><n:mi>σ</n:mi><n:mn>8</n:mn></n:msub><n:mo>=</n:mo><n:mn>0.815</n:mn><n:mo>±</n:mo><n:mn>0.012</n:mn></n:math>. We also present sound-horizon-independent estimates of the present day Hubble rate of <p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline"><p:mrow><p:msub><p:mrow><p:mi>H</p:mi></p:mrow><p:mrow><p:mn>0</p:mn></p:mrow></p:msub><p:mo>=</p:mo><p:msubsup><p:mrow><p:mn>66.4</p:mn></p:mrow><p:mrow><p:mo>−</p:mo><p:mn>3.7</p:mn></p:mrow><p:mrow><p:mo>+</p:mo><p:mn>3.2</p:mn></p:mrow></p:msubsup><p:mtext> </p:mtext><p:mtext> </p:mtext><p:mi>km</p:mi><p:mtext> </p:mtext><p:msup><p:mrow><p:mi mathvariant="normal">s</p:mi></p:mrow><p:mrow><p:mo>−</p:mo><p:mn>1</p:mn></p:mrow></p:msup><p:mtext> </p:mtext><p:msup><p:mrow><p:mi>Mpc</p:mi></p:mrow><p:mrow><p:mo>−</p:mo><p:mn>1</p:mn></p:mrow></p:msup></p:mrow></p:math> from our large scale structure data alone and <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:msub><s:mi>H</s:mi><s:mn>0</s:mn></s:msub><s:mo>=</s:mo><s:msubsup><s:mn>64.3</s:mn><s:mrow><s:mo>−</s:mo><s:mn>2.4</s:mn></s:mrow><s:mrow><s:mo>+</s:mo><s:mn>2.1</s:mn></s:mrow></s:msubsup><s:mtext> </s:mtext><s:mtext> </s:mtext><s:mi>km</s:mi><s:mtext> </s:mtext><s:msup><s:mi mathvariant="normal">s</s:mi><s:mrow><s:mo>−</s:mo><s:mn>1</s:mn></s:mrow></s:msup><s:mtext> </s:mtext><s:msup><s:mrow><s:mi>Mpc</s:mi></s:mrow><s:mrow><s:mo>−</s:mo><s:mn>1</s:mn></s:mrow></s:msup></s:math> in combination with uncalibrated supernovae from . Using parametric estimates of the evolution of matter density fluctuations, we place constraints on cosmic structure in a range of high redshifts typically inaccessible with cross-correlation analyses. Combining lensing cross- and autocorrelations, we derive a 3.3% constraint on the integrated matter density fluctuations above <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"><v:mi>z</v:mi><v:mo>=</v:mo><v:mn>2.4</v:mn></v:math>, one of the tightest constraints in this redshift range and fully consistent with a <x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline"><x:mrow><x:mi mathvariant="normal">Λ</x:mi></x:mrow></x:math> cold dark matter (<ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"><ab:mi mathvariant="normal">Λ</ab:mi><ab:mi>CDM</ab:mi></ab:math>) model fit to the primary CMB from . Finally, combining with primary CMB observations and using the extended low redshift coverage of these combined datasets we derive constraints on a variety of extensions to the <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" display="inline"><db:mi mathvariant="normal">Λ</db:mi><db:mi>CDM</db:mi></db:math> model including massive neutrinos, spatial curvature, and dark energy. We find in flat <gb:math xmlns:gb="http://www.w3.org/1998/Math/MathML" display="inline"><gb:mi mathvariant="normal">Λ</gb:mi><gb:mi>CDM</gb:mi><gb:mo>∑</gb:mo><gb:msub><gb:mi>m</gb:mi><gb:mi>ν</gb:mi></gb:msub><gb:mo>&lt;</gb:mo><gb:mn>0.12</gb:mn><gb:mtext> </gb:mtext><gb:mtext> </gb:mtext><gb:mi>eV</gb:mi></gb:math> at 95% confidence using the large scale structure data, BAO measurements from Sloan Digital Sky Survey, and primary CMB observations.

  PublisherOA PDFDOI

• The Atacama Cosmology Telescope: Large-scale velocity reconstruction with the kinematic Sunyaev-Zel'dovich effect and DESI LRGs

  Journal of Cosmology and Astroparticle Physics · 2025-05-01 · 6 citations

  articleOpen access

  Abstract The kinematic Sunyaev-Zel'dovich (kSZ) effect induces a non-zero density-density-temperature bispectrum, which we can use to reconstruct the large-scale velocity field from a combination of cosmic microwave background (CMB) and galaxy density measurements, in a procedure known as “kSZ velocity reconstruction”. This method has been forecast to constrain large-scale modes with future galaxy and CMB surveys, improving their measurement beyond what is possible with the galaxy surveys alone. Such measurements will enable tighter constraints on large-scale signals such as primordial non-Gaussianity, deviations from homogeneity, and modified gravity. In this work, we demonstrate a statistically significant measurement of kSZ velocity reconstruction for the first time, by applying quadratic estimators to the combination of the ACT DR6 CMB+kSZ map and the DESI LRG galaxies (with photometric redshifts) in order to reconstruct the velocity field. We do so using a formalism appropriate for the 2-dimensional projected galaxy fields that we use, which naturally incorporates the curved-sky effects important on the largest scales. We find evidence for the signal by cross-correlating with an external estimate of the velocity field from the spectroscopic BOSS survey and rejecting the null (no-kSZ) hypothesis at 3.8σ. Our work presents a first step towards the use of this observable for cosmological analyses.

  PublisherDOI

• Cosmological constraints from the cross-correlation of DESI Luminous Red Galaxies with CMB lensing from Planck PR4 and ACT DR6

  Journal of Cosmology and Astroparticle Physics · 2025-06-01 · 17 citations

  preprintOpen access

  Abstract We infer the growth of large scale structure over the redshift range 0.4 ≲ z ≲ 1 from the cross-correlation of spectroscopically calibrated Luminous Red Galaxies (LRGs) selected from the Dark Energy Spectroscopic Instrument (DESI) legacy imaging survey with CMB lensing maps reconstructed from the latest Planck and ACT data. We adopt a hybrid effective field theory (HEFT) model that robustly regulates the cosmological information obtainable from smaller scales, such that our cosmological constraints are reliably derived from the (predominantly) linear regime. We perform an extensive set of bandpower- and parameter-level systematics checks to ensure the robustness of our results and to characterize the uniformity of the LRG sample. We demonstrate that our results are stable to a wide range of modeling assumptions, finding excellent agreement with a linear theory analysis performed on a restricted range of scales. From a tomographic analysis of the four LRG photometric redshift bins we find that the rate of structure growth is consistent with ΛCDM with an overall amplitude that is ≃ 5-7% lower than predicted by primary CMB measurements with modest (∼ 2 σ ) statistical significance. From the combined analysis of all four bins and their cross-correlations with Planck we obtain S 8 = 0.765 ± 0.023, which is less discrepant with primary CMB measurements than previous DESI LRG cross Planck CMB lensing results. From the cross-correlation with ACT we obtain S 8 = 0.790 +0.024 -0.027 , while when jointly analyzing Planck and ACT we find S 8 = 0.775 +0.019 -0.022 from our data alone and σ 8 = 0.772 +0.020 -0.023 with the addition of BAO data. These constraints are consistent with the latest Planck primary CMB analyses at the ≃ 1.6-2.2 σ level, and are in excellent agreement with galaxy lensing surveys.

  PublisherOA PDFDOI

• The Simons Observatory: validation of reconstructed power spectra from simulated filtered maps for the small aperture telescope survey

  Journal of Cosmology and Astroparticle Physics · 2025-06-01 · 3 citations

  articleOpen access

  Abstract We present a transfer function-based method to estimate angular power spectra from filtered maps for cosmic microwave background (CMB) surveys. This is especially relevant for experiments targeting the faint primordial gravitational wave signatures in CMB polarisation at large scales, such as the Simons Observatory (SO) small aperture telescopes. While timestreams can be filtered to mitigate the contamination from low-frequency noise, usual methods that calculate the mode coupling at individual multipoles can be challenging for experiments covering large sky areas or reaching few-arcminute resolution. The method we present here, although approximate, is more practical and faster for larger data volumes. We validate it through the use of simulated observations approximating the first year of SO data, going from half-wave plate-modulated timestreams to maps, and using simulations to estimate the mixing of polarisation modes induced by an example of time-domain filtering. We show its performance through an example null test and with an end-to-end pipeline that performs inference on cosmological parameters, including the tensor-to-scalar ratio r . The performance demonstration uses simulated observations at multiple frequency bands. We find that the method can recover unbiased parameters for our simulated noise levels.

  PublisherDOI

Recent grants

• The Atacama Cosmology Telescope: searching for cracks in the Lambda Cold Dark Matter model

  NSF · $596k · 2021–2025

• Analysis of Atacama Cosmology Telescope data: cosmology beyond Planck

  NSF · $576k · 2018–2021

Frequent coauthors

• David N. Spergel

  94 shared

• Edward J. Wollack

  Goddard Space Flight Center

  91 shared

• Thibaut Louis

  Laboratoire de Physique des 2 Infinis Irène Joliot-Curie

  86 shared

• Lyman A. Page

  Princeton University

  82 shared

• J. Colin Hill

  Columbia University

  76 shared

• Sigurd Næss

  76 shared

• Erminia Calabrese

  Cardiff University

  74 shared

• M. Remazeilles

  73 shared

Labs

• Department of Astrophysical Sciences, Princeton UniversityPI