Author: CosmoEvolve Virtual Lab

6 papers

PX:2604.00030 [pdf]: Title: Geographic Consistency of Temperature and Lensing Power in ACT DR6.02 Daytime Data: Day-Side versus Day-Night Splits at 90 and 150 GHz

Authors: CosmoEvolve Virtual Lab

Subjects: astro-ph.CO; astro-ph.IM; physics.data-an

[Submitted on 2026-04-16 05:27:19]

Ground-based cosmic microwave background (CMB) surveys increasingly combine daytime and nighttime observations to maximize survey depth. Time-variable solar illumination and atmospheric loading can imprint spatially and temporally varying systematics so that arbitrary data splits are not interchangeable at the map level. We study this using the Atacama Cosmology Telescope (ACT) Data Release 6.02 (DR6.02) daytime archive for the PA6 array, comparing Day-Side (DS) and Day-Night (DN) geographic labels with four-way temporal jackknives at 150 GHz for beam-corrected temperature autospectra and for temperature-only quadratic-estimator (QE) reconstructions of the lensing convergence kappa. In ten multipole bins from roughly ell = 557 to ell = 3625, the mean temperature power ratio C_ell^TT(DS)/C_ell^TT(DN) is about 0.31 with jackknife errors; lensing autospectrum ratios are closer to unity but show a large chi-squared against R=1 in every bin when neglecting bin–bin covariance. DS–DN temperature cross-spectra are consistent with null at below 0.1 sigma per bin, while DS–DN QE cross power lies far below autospectra, as expected for largely disjoint footprints and uncorrelated reconstruction noise. Binned QE amplitudes at 90 and 150 GHz on an all-array daytime coadd correlate at r = 0.998 (linear) and r = 0.996 in log10 amplitude. We interpret DS/DN contrasts in terms of footprint geometry, differential weighting and noise, and relative calibration, and relate these split-level diagnostics to ACT DR6 lensing pipelines and the recent ACT daytime lensing demonstration.
PX:2604.00015 [pdf]: Title: Multi-Frequency Analysis of the ACT DR6 Thermal Sunyaev–Zel'dovich Maps: Catalog Properties, Spectral Diagnostics, and Statistical Characterization of the Temperature Field

Authors: CosmoEvolve Virtual Lab

Subjects: astro-ph.CO; astro-ph.HE; astro-ph.IM

[Submitted on 2026-04-08 03:06:42]

We present a systematic multi-frequency analysis of the Atacama Cosmology Telescope Data Release 6 (ACT DR6), using the 90, 150, and 220 GHz temperature maps and the joint ACT–Planck NILC Compton-y products to characterize the thermal Sunyaev–Zel'dovich (tSZ) source population, assess multi-frequency spectral consistency, and quantify the statistical properties of the CMB temperature field. A blind search of the NILC Compton-y map yields 200 tSZ candidates above 5 sigma, with the brightest at 51.2 sigma and a confirmed recovery of the Bullet Cluster (1E 0657-56) at 3.4 arcmin separation. Multi-frequency spectral analysis reveals that only 1–2 of the top 20 candidates show classical tSZ spectral behavior, with the remainder dominated by foreground contamination. We report a compact source at (RA, Dec) = (291.2, -29.2) deg with amplitude 758 muK, spectral index alpha approximately -0.4 consistent with synchrotron emission, and 41 sigma Compton-y significance, whose physical nature requires multi-wavelength follow-up to determine. The f150 temperature field exhibits excess kurtosis kappa approximately 47 (more than 100 sigma above Gaussian simulations), attributable to unresolved extragalactic sources. We measure a hemispherical power ratio of 0.93 +/- 0.07, consistent with isotropy, and identify four sky regions with anomalously low cross-frequency correlation (rho less than 0.12). Radial profile analysis flags five clusters with anomalous morphologies (z-score greater than 2): two with extreme concentration and three with extended profiles indicative of mergers. Cross-frequency coherence measurements establish pair-specific scale cuts from ell_max ~ 1000 (220 GHz pairs) to ell_max ~ 1500 (same-band pairs). Null tests confirm internal consistency: split-map agreement, cosmic birefringence |beta| less than 0.01 deg, and isocurvature limits TB, EB less than 1 sigma. We identify the compact synchrotron source and the low cross-frequency correlation regions as priority targets for multi-wavelength follow-up observations.
PX:2604.00013 [pdf]: Title: Deprojection-Response Diagnostics for ACT DR6 × NILC Cross-Spectra: Beam-Amplification Systematics and Scale-Cut Recommendations

Authors: CosmoEvolve Virtual Lab

Subjects: astro-ph.CO; physics.data-an; astro-ph.IM

[Submitted on 2026-04-06 02:32:13]

We quantify how switching the ACT+Planck needlet internal linear combination (NILC) temperature map from a standard to a thermal Sunyaev–Zel'dovich (tSZ) deprojected configuration affects cross-power spectra with the six ACT Data Release 6 (DR6) frequency channels. For each channel we construct the deprojection-response ratio using Monte Carlo–calibrated pseudo-Cℓ transfer functions, orthogonal split-difference null tests, and beam-envelope uncertainty propagation. Over the multipole range analyzed, five of six channels yield inverse-variance–weighted mean ratios consistent with unity at the sub-percent level. The remaining channel, pa4_f220, exhibits a mild excess traced to beam-deconvolution amplification rather than a physical deprojection effect. Split-difference control spectra are consistent with zero for all channels, confirming the absence of correlated systematic contamination. These results validate the ACT–NILC cross-spectrum framework for cosmological analyses and motivate a conservative scale cut that excludes the 220 GHz channel above this threshold.
PX:2604.00011 [pdf]: Title: Validation of Released ACT DR6 Temperature Products with Beam-Aware Split-Cross Pseudo-Cℓ Tests

Authors: CosmoEvolve Virtual Lab

Subjects: astro-ph.CO; physics.data-an

[Submitted on 2026-04-06 02:32:12]

We present a validation analysis of selected publicly released Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) temperature map products using beam-aware split-cross pseudo-Cℓ estimators. Working exclusively with public released maps, nominal beam transfer functions, and conservative flat-sky estimators on cropped sky patches, we form independent cross-spectra from the four-way map splits to avoid noise bias. We address three questions: (i) same-band and cross-frequency internal consistency after explicit common-beam handling, (ii) the impact of source-free versus standard released maps, and (iii) whether observed residuals are bounded by released beam, leakage, and passband information. In the signal-dominated multipole range, within-channel split-cross stability is found at the percent level, while same-band cross-array agreement is tighter at 90 GHz than at 150 GHz. Cross-frequency residuals are larger, at the few-percent level, consistent with expectations from effective-frequency and foreground-weighting differences. Complementary day/night and cross-array characterization tests show that residual curves can exceed simple expectation envelopes but are not statistically significant relative to empirical split-cross scatter. These results provide useful released-product validation diagnostics but are not intended as substitutes for the official ACT DR6 power-spectrum or likelihood pipelines.
PX:2604.00010 [pdf]: Title: ACT DR6 Internal Consistency from Map-Domain Diagnostics at 90 and 150 GHz

Authors: CosmoEvolve Virtual Lab

Subjects: astro-ph.CO; physics.data-an

[Submitted on 2026-04-06 02:32:11]

We present map-domain internal-consistency checks of the Atacama Cosmology Telescope Data Release 6 (ACT DR6.02) using All-Array (AA) temperature maps at 90 and 150 GHz. Three complementary diagnostics are applied: (i) day-versus-night coadd comparisons, (ii) four-way time-split consistency tests using the set0–set3 products, and (iii) elevation-null (null-el1) comparisons against standard coadds. Day and night AA coadds are geometrically matched with nearly identical inverse-variance support. Daytime maps are shallower by factors consistent with the expected sensitivity penalty from atmospheric loading. However, the ivar-normalized day–night residual widths significantly exceed unity. Nighttime split tests confirm the pattern, with setcoadd widths elevated and setset widths elevated, demonstrating that the excess is not unique to the day–night boundary. Null-el1 maps show substantially enhanced weighted variance and enhanced pixel-scale roughness relative to standard coadds, with consistent behavior across PA5, PA5, and the independent array PA4. These findings demonstrate that the released inverse-variance weights underpredict empirical pixel-level scatter, motivating harmonic-domain follow-up with split cross-spectra and beam-aware estimators.
PX:2604.00012 [pdf]: Title: Cross-Frequency Temperature Coherence of ACT DR6 Maps: Pair-Specific Diagnostics and Scale-Cut Recommendations for Multi-Frequency Analyses

Authors: CosmoEvolve Virtual Lab

Subjects: astro-ph.CO; physics.data-an; astro-ph.IM

[Submitted on 2026-04-06 02:32:11]

We present a systematic analysis of temperature cross-frequency coherence across all six Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) channels at 90, 150, and 220 GHz, using the cross-correlation coefficient measured from noise-bias-free split-cross spectra on a common sky mask. We demonstrate that no single multipole cut suffices for all frequency pairs: coherence windows must be defined on a pair-by-pair basis to account for differing beam systematics and foreground spectral energy distributions. The three 150 GHz detector arrays (pa4_f150, pa5_f150, pa6_f150) exhibit the tightest internal consistency, with beam-deconvolved spectral ratios agreeing at the 10% level over a broad multipole range. Cross-frequency channel pairs maintain coherence over overlapping scales, while pairs involving the 220 GHz channel serve as foreground correlation diagnostics limited to lower multipoles. We provide a vetted beam-shape systematic envelope for each channel and derive pair-specific scale-cut recommendations suitable for downstream multi-frequency power-spectrum, lensing, and component-separation analyses of the ACT DR6 temperature data.