arxiv: 2503.14452 · v2 · submitted 2025-03-18 · 🌌 astro-ph.CO · hep-ph

Recognition: 2 theorem links

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The Atacama Cosmology Telescope: DR6 Power Spectra, Likelihoods and ΛCDM Parameters

Thibaut Louis , Adrien La Posta , Zachary Atkins , Hidde T. Jense , Irene Abril-Cabezas , Graeme E. Addison , Peter A. R. Ade , Simone Aiola

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Tommy Alford David Alonso Mandana Amiri Rui An Jason E. Austermann Eleonora Barbavara Nicholas Battaglia Elia Stefano Battistelli James A. Beall Rachel Bean Ali Beheshti Benjamin Beringue Tanay Bhandarkar Emily Biermann Boris Bolliet J Richard Bond Erminia Calabrese Valentina Capalbo Felipe Carrero Shi-Fan Chen Grace Chesmore Hsiao-mei Cho Steve K. Choi Susan E. Clark Nicholas F. Cothard Kevin Coughlin William Coulton Devin Crichton Kevin T. Crowley Omar Darwish Mark J. Devlin Simon Dicker Cody J. Duell Shannon M. Duff Adriaan J. Duivenvoorden Jo Dunkley Rolando Dunner Carmen Embil Villagra Max Fankhanel Gerrit S. Farren Simone Ferraro Allen Foster Rodrigo Freundt Brittany Fuzia Patricio A. Gallardo Xavier Garrido Martina Gerbino Serena Giardiello Ajay Gill Jahmour Givans Vera Gluscevic Samuel Goldstein Joseph E. Golec Yulin Gong Yilun Guan Mark Halpern Ian Harrison Matthew Hasselfield Erin Healy Shawn Henderson Brandon Hensley Carlos Herv\'ias-Caimapo J. Colin Hill Gene C. Hilton Matt Hilton Adam D. Hincks Ren\'ee Hlo\v{z}ek Shuay-Pwu Patty Ho John Hood Erika Hornecker Zachary B. Huber Johannes Hubmayr Kevin M. Huffenberger John P. Hughes Margaret Ikape Kent Irwin Giovanni Isopi Neha Joshi Ben Keller Joshua Kim Kenda Knowles Brian J. Koopman Arthur Kosowsky Darby Kramer Aleksandra Kusiak Alex Lague Victoria Lakey Eunseong Lee Yaqiong Li Zack Li Michele Limon Martine Lokken Marius Lungu Niall MacCrann Amanda MacInnis Mathew S. Madhavacheril Diego Maldonado Felipe Maldonado Maya Mallaby-Kay Gabriela A. Marques Joshiwa van Marrewijk Fiona McCarthy Jeff McMahon Yogesh Mehta Felipe Menanteau Kavilan Moodley Thomas W. Morris Tony Mroczkowski Sigurd Naess Toshiya Namikawa Federico Nati Simran K. Nerval Laura Newburgh Andrina Nicola Michael D. Niemack Michael R. Nolta John Orlowski-Scherer Luca Pagano Lyman A. Page Shivam Pandey Bruce Partridge Karen Perez Sarmiento Heather Prince Roberto Puddu Frank J. Qu Damien C. Ragavan Bernardita Ried Guachalla Keir K. Rogers Felipe Rojas Tai Sakuma Emmanuel Schaan Benjamin L. Schmitt Neelima Sehgal Shabbir Shaikh Blake D. Sherwin Carlos Sierra Jon Sievers Crist\'obal Sif\'on Sara Simon Rita Sonka David N. Spergel Suzanne T. Staggs Emilie Storer Kristen Surrao Eric R. Switzer Niklas Tampier Robert Thornton Hy Trac Carole Tucker Joel Ullom Leila R. Vale Alexander van Engelen Jeff Van Lanen Cristian Vargas Eve M. Vavagiakis Kasey Wagoner Yuhan Wang Lukas Wenzl Edward J. Wollack Kaiwen Zheng

Authors on Pith no claims yet

Pith reviewed 2026-05-13 14:39 UTC · model grok-4.3

classification 🌌 astro-ph.CO hep-ph

keywords CMB power spectraAtacama Cosmology TelescopeΛCDM parameterscosmological constraintsPlanck dataSunyaev-Zel'dovich effectbaryon acoustic oscillations

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The pith

ACT DR6 power spectra combined with Planck data constrain the universe's composition, expansion rate, and initial conditions within the standard ΛCDM model.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper measures cosmic microwave background temperature and polarization power spectra from Atacama Cosmology Telescope Data Release 6 maps covering large sky areas at 98, 150, and 220 GHz. These spectra match the predictions of the ΛCDM model plus known foregrounds when analyzed over 10,000 square degrees to arcminute scales. Joint analysis with Planck data then yields precise parameter values for baryon and dark matter densities, the Hubble constant, the scalar spectral index, and the fluctuation amplitude. The results remain consistent whether using temperature or polarization data and show no excess lensing or departure from spatial flatness. A high-significance detection of Sunyaev-Zel'dovich anisotropy appears with a small-scale tilt matching hydrodynamical simulations that include feedback.

Core claim

The ACT DR6 angular power spectra in TT, TE, and EE are well fit by the sum of CMB anisotropy described by ΛCDM plus foregrounds, and the joint P-ACT dataset with Planck produces Ω_b h² = 0.0226 ± 0.0001, Ω_c h² = 0.118 ± 0.001, H0 = 68.22 ± 0.36 km/s/Mpc, n_s = 0.974 ± 0.003, and σ8 = 0.813 ± 0.005. Adding CMB lensing and DESI baryon acoustic oscillation data leaves the same ΛCDM parameters consistent at the 1.6σ level with DESI DR2, with no evidence for excess lensing or non-flat geometry.

What carries the argument

The ACT DR6 maps and derived angular power spectra in temperature and polarization, modeled as ΛCDM CMB plus foreground components including a tilted Sunyaev-Zel'dovich template.

If this is right

Baryon density is fixed at 0.0226 with 0.4 percent precision and cold dark matter density at 0.118 with 1 percent precision.
The Hubble constant is measured at 68.22 km/s/Mpc from the joint dataset and tightens to 68.43 km/s/Mpc when DESI DR2 is added.
The scalar spectral index is 0.974 and fluctuation amplitude σ8 is 0.813, both consistent across temperature and polarization channels.
Sunyaev-Zel'dovich anisotropy is detected at high significance with suppressed small-scale power relative to the baseline template.
No departure from spatial flatness is found and lensing is consistent with the ΛCDM prediction.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

These measurements can be cross-checked against independent local distance-ladder Hubble constant determinations to quantify any remaining tension.
The observed SZ tilt supplies a direct test for galaxy formation feedback prescriptions in hydrodynamical simulations.
Future ACT or Simons Observatory data at higher sensitivity could isolate possible scale-dependent deviations from the current best-fit model.
The consistency between P-ACT and DESI DR2 at 1.6σ suggests the parameter values are robust to the choice of large-scale structure tracer.

Load-bearing premise

The observed ACT power spectra are accurately described by the standard ΛCDM CMB signal plus modeled foregrounds with no large unaccounted systematics.

What would settle it

A statistically significant residual in the ACT TT, TE, or EE spectra after subtracting the best-fit ΛCDM-plus-foregrounds model at scales where noise is low would falsify the central claim.

read the original abstract

We present power spectra of the cosmic microwave background (CMB) anisotropy in temperature and polarization, measured from the Data Release 6 maps made from Atacama Cosmology Telescope (ACT) data. These cover 19,000 deg$^2$ of sky in bands centered at 98, 150 and 220 GHz, with white noise levels three times lower than Planck in polarization. We find that the ACT angular power spectra estimated over 10,000 deg$^2$, and measured to arcminute scales in TT, TE and EE, are well fit by the sum of CMB and foregrounds, where the CMB spectra are described by the $\Lambda$CDM model. Combining ACT with larger-scale Planck data, the joint P-ACT dataset provides tight limits on the ingredients, expansion rate, and initial conditions of the universe. We find similar constraining power, and consistent results, from either the Planck power spectra or from ACT combined with WMAP data, as well as from either temperature or polarization in the joint P-ACT dataset. When combined with CMB lensing from ACT and Planck, and baryon acoustic oscillation data from DESI DR1, we measure a baryon density of $\Omega_b h^2=0.0226\pm0.0001$, a cold dark matter density of $\Omega_c h^2=0.118\pm0.001$, a Hubble constant of $H_0=68.22\pm0.36$ km/s/Mpc, a spectral index of $n_s=0.974\pm0.003$, and an amplitude of density fluctuations of $\sigma_8=0.813\pm0.005$. Including the DESI DR2 data tightens the Hubble constant to $H_0=68.43\pm0.27$ km/s/Mpc; $\Lambda$CDM parameters agree between the P-ACT and DESI DR2 data at the $1.6\sigma$ level. We find no evidence for excess lensing in the power spectrum, and no departure from spatial flatness. The contribution from Sunyaev-Zel'dovich (SZ) anisotropy is detected at high significance; we find evidence for a tilt with suppressed small-scale power compared to our baseline SZ template spectrum, consistent with hydrodynamical simulations with feedback.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

ACT DR6 gives new independent CMB spectra over 10k deg2 that fit LambdaCDM plus foregrounds and tighten joint constraints with Planck and DESI without major surprises.

read the letter

The key point is that this DR6 release supplies fresh high-resolution ACT power spectra in TT, TE, and EE that are measured to arcminute scales over a large sky patch and combine cleanly with Planck to sharpen LambdaCDM parameters. The numbers line up with prior results: Omega_b h2 at 0.0226, H0 near 68.3, sigma8 at 0.813, and no sign of excess lensing or curvature. The SZ anisotropy shows up at high significance with a tilt that matches hydro simulations including feedback, which is a concrete new detail from the data itself. Polarization noise is three times lower than Planck, and the internal splits plus cross-checks with WMAP look consistent. That is real value for anyone updating parameter tables or testing extensions. The analysis follows standard methods for foreground subtraction and likelihood construction, which keeps the paper straightforward rather than flashy. The central assumption—that the spectra are CMB plus known foregrounds with no large unmodeled systematics—holds in the reported fits, and the circularity is low because the power spectra are direct observables cross-checked externally. A minor soft spot is that the abstract summarizes the error budget and foreground modeling at a high level; a referee would still need the full covariance details and template choices to confirm robustness at the smallest scales. This is the kind of paper cosmologists who combine CMB with BAO or lensing data will want to cite for the updated numbers. It deserves a serious referee because the dataset is new, the consistency checks are present, and the constraints are precise enough to matter for precision cosmology work.

Referee Report

1 major / 2 minor

Summary. The manuscript presents CMB temperature and polarization power spectra from ACT DR6 maps covering 19,000 deg² (with analysis over 10,000 deg²) in bands at 98, 150, and 220 GHz. It demonstrates that the TT, TE, and EE spectra to arcminute scales are well fit by the ΛCDM model plus foregrounds, including a high-significance SZ anisotropy component with a detected tilt matching hydrodynamical simulations. Joint P-ACT constraints with Planck, combined with ACT/Planck lensing and DESI BAO, yield precise ΛCDM parameters (e.g., Ω_b h²=0.0226±0.0001, H0=68.22±0.36 km/s/Mpc) consistent with WMAP and DESI, with no evidence for excess lensing or non-flatness.

Significance. If the results hold, this provides a valuable independent high-resolution CMB dataset that cross-validates Planck measurements and tightens cosmological constraints when combined, particularly through polarization and small-scale data. The explicit SZ detection and tilt, plus consistency across splits and with external probes, strengthen the case for ΛCDM and improve robustness of parameters like σ8 and H0. Machine-checked consistency checks and reproducible likelihoods would further enhance its impact.

major comments (1)

The central claim that the ACT spectra over 10,000 deg² are well fit by ΛCDM plus foregrounds with no significant unmodeled systematics underpins all parameter results. The full error budget, including systematic contributions to the power spectra and their propagation into the joint P-ACT likelihood, must be presented in detail (likely in the methods or results section on likelihood construction) to allow verification that residuals do not bias the reported constraints such as H0=68.22±0.36.

minor comments (2)

Clarify in the abstract and introduction why the power spectrum analysis uses 10,000 deg² while maps cover 19,000 deg², including any masking or selection criteria.
A table comparing ΛCDM parameters derived from temperature-only vs. polarization-only subsets of the P-ACT dataset would strengthen the reported internal consistency.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their constructive review and recommendation for minor revision. We appreciate the emphasis on transparency in the error budget and address the point below.

read point-by-point responses

Referee: The central claim that the ACT spectra over 10,000 deg² are well fit by ΛCDM plus foregrounds with no significant unmodeled systematics underpins all parameter results. The full error budget, including systematic contributions to the power spectra and their propagation into the joint P-ACT likelihood, must be presented in detail (likely in the methods or results section on likelihood construction) to allow verification that residuals do not bias the reported constraints such as H0=68.22±0.36.

Authors: We agree that a detailed, explicit presentation of the full error budget is necessary for independent verification. The current manuscript describes the power spectrum estimation, foreground modeling, null tests, and likelihood construction (including covariance from simulations), with systematic uncertainties quantified via data splits and simulations. To address the referee's request directly, we will add a dedicated subsection (or expanded table) in the revised methods section on likelihood construction. This will tabulate all systematic contributions (e.g., calibration, beam, atmospheric, and map-making residuals), show their propagation into the joint P-ACT covariance matrix, and demonstrate via explicit checks that residuals do not bias parameters such as H0 at the reported precision. revision: yes

Circularity Check

0 steps flagged

No significant circularity in derivation chain

full rationale

The paper measures ACT DR6 angular power spectra directly from the maps as observables (TT, TE, EE to arcminute scales over 10,000 deg²). These are then fit to a ΛCDM + foreground model (including tilted SZ) to extract parameters, with joint constraints from Planck data. This is standard Bayesian parameter estimation from independent data; the spectra are cross-checked against Planck and WMAP, and fit quality (no excess lensing, acceptable χ²) is reported as a test rather than an assumption. No self-definitional reductions, fitted inputs renamed as predictions, or load-bearing self-citations appear in the abstract or described chain. The result is externally falsifiable against other datasets and does not reduce to its inputs by construction.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claim rests on the validity of the ΛCDM model for describing CMB spectra after foreground subtraction and on accurate modeling of instrumental and astrophysical systematics.

free parameters (1)

ΛCDM cosmological parameters
Fitted directly to the combined ACT+Planck+DESI power spectra and BAO data.

axioms (1)

domain assumption The observed spectra are the sum of CMB (ΛCDM) plus modeled foregrounds with no significant unaccounted systematics
Invoked when stating the spectra are well fit by the model.

pith-pipeline@v0.9.0 · 6548 in / 1380 out tokens · 41238 ms · 2026-05-13T14:39:19.480882+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

IndisputableMonolith.Foundation.DAlembert.Inevitability bilinear_family_forced unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

We find that the ACT angular power spectra … are well fit by the sum of CMB and foregrounds, where the CMB spectra are described by the ΛCDM model. Combining ACT with larger-scale Planck data, the joint P-ACT dataset provides tight limits on the ingredients, expansion rate, and initial conditions of the universe … Ω_b h² = 0.0226 ± 0.0001, Ω_c h² = 0.118 ± 0.001, H_0 = 68.22 ± 0.36 km/s/Mpc, n_s = 0.974 ± 0.003, and σ_8 = 0.813 ± 0.005.
IndisputableMonolith.Foundation.DimensionForcing dimension_forced unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

We find no evidence for excess lensing in the power spectrum, and no departure from spatial flatness.

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