Search for: All records

Weak gravitational lensing of the cosmic microwave background (CMB) has been established as a robust and powerful observable for precision cosmology. However, the impact of Galactic foregrounds, which has been studied less extensively than many other potential systematics, could in principle pose a problem for CMB lensing measurements. These foregrounds are inherently non-Gaussian and hence might mimic the characteristic signal that lensing estimators are designed to measure. We present an analysis that quantifies the level of contamination from Galactic dust in lensing measurements, focusing particularly on measurements with the Atacama Cosmology Telescope and the Simons Observatory. We employ a whole suite of foreground models and study the contamination of lensing measurements with both individual frequency channels and multifrequency combinations. We test the sensitivity of different estimators to the level of foreground non-Gaussianity and the dependence on sky fraction and multipole range used. We find that Galactic foregrounds do not present a problem for the Atacama Cosmology Telescope experiment (the bias in the inferred CMB lensing power spectrum amplitude remains below $0.3\sigma$). For Simons Observatory, not all foreground models remain below this threshold. Although our results are conservative upper limits, they suggest that further work on characterizing dust biases and determining the impact of mitigation methods is well motivated, especially for the largest sky fractions. 

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 $S_8^{3\mathrm{x}2\mathrm{pt}}\equiv {\sigma }_8({\mathrm{\Omega }}_m/0.3{)}^{0.4}=0.815\pm 0.012$. The commonly used $S_8\equiv {\sigma }_8({\mathrm{\Omega }}_m/0.3{)}^{0.5}$parameter is constrained to $S_8=0.816\pm 0.015$. In combination with baryon acoustic oscillation (BAO) measurements we find ${\sigma }_8=0.815\pm 0.012$. We also present sound-horizon-independent estimates of the present day Hubble rate of $H_0={66.4}_{-3.7}^{+3.2}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$from our large scale structure data alone and $H_0={64.3}_{-2.4}^{+2.1}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$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 $z=2.4$, one of the tightest constraints in this redshift range and fully consistent with a $\mathrm{\Lambda }$cold dark matter ( $\mathrm{\Lambda }\mathrm{CDM}$) 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 $\mathrm{\Lambda }\mathrm{CDM}$model including massive neutrinos, spatial curvature, and dark energy. We find in flat $\mathrm{\Lambda }\mathrm{CDM}\sum m_{\nu }<0.12\mathrm{eV}$at 95% confidence using the large scale structure data, BAO measurements from Sloan Digital Sky Survey, and primary CMB observations. 

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 latestPlanckand 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 (∼ 2σ) statistical significance.From the combined analysis of all four bins and their cross-correlations withPlanckwe obtainS₈= 0.765 ± 0.023, which is less discrepant with primary CMB measurements than previous DESI LRG crossPlanckCMB lensing results.From the cross-correlation with ACT we obtainS₈= 0.790^+0.024_-0.027, while when jointly analyzingPlanckand ACT we findS₈= 0.775^+0.019_-0.022from our data alone andσ₈= 0.772^+0.020_-0.023with the addition of BAO data.These constraints are consistent with the latestPlanckprimary CMB analyses at the ≃ 1.6-2.2σlevel, and are in excellent agreement with galaxy lensing surveys. 

Abstract We present a high-significance cross-correlation of CMB lensing maps from the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) with luminous red galaxies (LRGs) from the Dark Energy Spectroscopic Instrument (DESI) Legacy Survey spectroscopically calibrated by DESI. We detect this cross-correlation at a significance of 38σ; combining our measurement with thePlanck Public Release 4 (PR4) lensing map, we detect the cross-correlation at 50σ. Fitting this jointly with the galaxy auto-correlation power spectrum to break the galaxy bias degeneracy withσ₈, we perform a tomographic analysis in four LRG redshift bins spanning 0.4 ≤z≤ 1.0 to constrain the amplitude of matter density fluctuations through the parameter combinationS₈^×=σ₈(Ω_m/ 0.3)^0.4. Prior to unblinding, we confirm with extragalactic simulations that foreground biases are negligible and carry out a comprehensive suite of null and consistency tests. Using a hybrid effective field theory (HEFT) model that allows scales as small ask_max= 0.6 h/ Mpc, we obtain a 3.3% constraint onS₈^×=σ₈(Ω_m/ 0.3)^0.4= 0.792^+0.024_-0.028from ACT data, as well as constraints onS₈^×(z) that probe structure formation over cosmic time.Our result is consistent with the early-universe extrapolation from primary CMB anisotropies measured byPlanck PR4 within 1.2σ. Jointly fitting ACT andPlanck lensing cross-correlations we obtain a 2.7% constraint ofS₈^×= 0.776^+0.019_-0.021, which is consistent with the Planck early-universe extrapolation within 2.1σ, with the lowest redshift bin showing the largest difference in mean. The latter may motivate further CMB lensing tomography analyses atz< 0.6 to assess the impact of potential systematics or the consistency of the ΛCDM model over cosmic time. 

ABSTRACT Compact sources can cause scatter in the scaling relationships between the amplitude of the thermal Sunyaev–Zel’dovich Effect (tSZE) in galaxy clusters and cluster mass. Estimates of the importance of this scatter vary – largely due to limited data on sources in clusters at the frequencies at which tSZE cluster surveys operate. In this paper, we present 90 GHz compact source measurements from a sample of 30 clusters observed using the MUSTANG2 instrument on the Green Bank Telescope. We present simulations of how a source’s flux density, spectral index, and angular separation from the cluster’s centre affect the measured tSZE in clusters detected by the Atacama Cosmology Telescope (ACT). By comparing the MUSTANG2 measurements with these simulations we calibrate an empirical relationship between 1.4 GHz flux densities from radio surveys and source contamination in ACT tSZE measurements. We find 3 per cent of the ACT clusters have more than a 20 per cent decrease in Compton-y but another 3 per cent have a 10 per cent increase in the Compton-y due to the matched filters used to find clusters. As sources affect the measured tSZE signal and hence the likelihood that a cluster will be detected, testing the level of source contamination in the tSZE signal using a tSZE-selected catalogue is inherently biased. We confirm this by comparing the ACT tSZE catalogue with optically and X-ray-selected cluster catalogues. There is a strong case for a large, high-resolution survey of clusters to better characterize their source population.