We present tomographic measurements of structure growth using crosscorrelations of Atacama Cosmology Telescope (ACT) DR6 and Planck cosmic microwave background (CMB) lensing maps with the unWISE Blue and Green galaxy samples, which span the redshift ranges 0.2 ≲
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Abstract z ≲ 1.1 and 0.3 ≲z ≲ 1.8, respectively. We improve on prior unWISE crosscorrelations not just by making use of the new, highprecision ACT DR6 lensing maps, but also by including additional spectroscopic data for redshift calibration and by analyzing our measurements with a more flexible theoretical model. We determine the amplitude of matter fluctuations at low redshifts (z ≃ 0.2–1.6), finding using the ACT crosscorrelation alone and ${S}_{8}\equiv {\sigma}_{8}{({\mathrm{\Omega}}_{m}/0.3)}^{0.5}=0.813\pm 0.021$S _{8}= 0.810 ± 0.015 with a combination of Planck and ACT crosscorrelations; these measurements are fully consistent with the predictions from primary CMB measurements assuming standard structure growth. The addition of baryon acoustic oscillation data breaks the degeneracy betweenσ _{8}and Ω_{m}, allowing us to measureσ _{8}= 0.813 ± 0.020 from the crosscorrelation of unWISE with ACT andσ _{8}= 0.813 ± 0.015 from the combination of crosscorrelations with ACT and Planck. These results also agree with the expectations from primary CMB extrapolations in ΛCDM cosmology; the consistency ofσ _{8}derived from our two redshift samples atz ∼ 0.6 and 1.1 provides a further check of our cosmological model. Our results suggest that structure formation on linear scales is well described by ΛCDM even down to low redshiftsz ≲ 1. 
Abstract Line intensity mapping (LIM) is a rapidly emerging technique for constraining cosmology and galaxy formation using multifrequency, low angular resolution maps.Many LIM applications crucially rely on crosscorrelations of two line intensity maps, or of intensity maps with galaxy surveys or galaxy/CMB lensing.We present a consistent halo model to predict all these crosscorrelations and enable joint analyses, in 3D redshiftspace and for 2D projected maps.We extend the conditional luminosity function formalism to the multiline case, to consistently account for correlated scatter between multiple galaxy line luminosities.This allows us to model the scaledependent decorrelation between two line intensity maps,a key input for foreground rejection and for approaches that estimate autospectra from crossspectra.This also enables LIM crosscorrelations to reveal astrophysical properties of the interstellar medium inacessible with LIM autospectra.We expose the different sources of luminosity scatter or “line noise” in LIM, and clarify their effects on the 1halo and galaxy shot noise terms.In particular, we show that the effective number density of halos can in some cases exceed that of galaxies, counterintuitively.Using observational and simulation input, we implement this halo model for the Hα, [Oiii], Lymanα, CO and [Cii] lines.We encourage observers and simulators to measure galaxy luminosity correlation coefficients for pairs of lines whenever possible.Our code is publicly available at https://github.com/EmmanuelSchaan/HaloGen/tree/LIM .In a companion paper, we use this halo model formalism and codeto highlight the degeneracies between cosmology and astrophysics in LIM, and to compare the LIM observables to galaxy detection for a number of surveys.more » « less

Abstract Line intensity mapping (LIM) proposes to efficiently observe distant faint galaxies and map the matter density field at high redshift.Building upon the formalism in a companion paper,we first highlight the degeneracies between cosmology and astrophysics in LIM.We discuss what can be constrained from measurements of the mean intensity and redshiftspace power spectra.With a sufficient spectral resolution, the largescale redshiftspace distortions of the 2halo term can be measured, helping to break the degeneracy between bias and mean intensity.With a higher spectral resolution, measuring the smallscale redshiftspace distortions disentangles the 1halo and shot noise terms.Crosscorrelations with external galaxy catalogs or lensing surveys further break degeneracies.We derive requirements for experiments similar to SPHEREx, HETDEX, CDIM, COMAP and CONCERTO.We then revisit the question of the optimality of the LIM observables, compared to galaxy detection, for astrophysics and cosmology.We use a matched filter to compute the luminosity detection threshold for individual sources.We show that LIM contains information about galaxies too faint to detect, in the highnoise or highconfusion regimes.We quantify the sparsity and clustering bias of the detected sources and compare them to LIM, showing in which cases LIM is a better tracer of the matter density.We extend previous work by answering these questions as a function of Fourier scale, including for the first time the effect of cosmic variance, pixeltopixel correlations, luminositydependent clustering bias and redshiftspace distortions.more » « less

ABSTRACT Reconstruction is becoming a crucial procedure of galaxy clustering analysis for future spectroscopic redshift surveys to obtain subper cent level measurement of the baryon acoustic oscillation scale. Most reconstruction algorithms rely on an estimation of the displacement field from the observed galaxy distribution. However, the displacement reconstruction degrades near the survey boundary due to incomplete data and the boundary effects extend to ${\sim}100\, \mathrm{Mpc}/h$ within the interior of the survey volume. We study the possibility of using radial velocities measured from the cosmic microwave background observation through the kinematic Sunyaev–Zeldovich effect to improve performance near the boundary. We find that the boundary effect can be reduced to ${\sim}3040\, \mathrm{Mpc}/h$ with the velocity information from Simons Observatory. This is especially helpful for dense low redshift surveys where the volume is relatively small and a large fraction of total volume is affected by the boundary.more » « less

Abstract We present cosmological constraints from a gravitational lensing mass map covering 9400 deg^{2}reconstructed from measurements of the cosmic microwave background (CMB) made by the Atacama Cosmology Telescope (ACT) from 2017 to 2021. In combination with measurements of baryon acoustic oscillations and big bang nucleosynthesis, we obtain the clustering amplitude
σ _{8}= 0.819 ± 0.015 at 1.8% precision, , and the Hubble constant ${S}_{8}\equiv {\sigma}_{8}{({\mathrm{\Omega}}_{\mathrm{m}}/0.3)}^{0.5}=0.840\pm 0.028$H _{0}= (68.3 ± 1.1) km s^{−1}Mpc^{−1}at 1.6% precision. A joint constraint with Planck CMB lensing yieldsσ _{8}= 0.812 ± 0.013, , and ${S}_{8}\equiv {\sigma}_{8}{({\mathrm{\Omega}}_{\mathrm{m}}/0.3)}^{0.5}=0.831\pm 0.023$H _{0}= (68.1 ± 1.0) km s^{−1}Mpc^{−1}. These measurements agree with ΛCDM extrapolations from the CMB anisotropies measured by Planck. We revisit constraints from the KiDS, DES, and HSC galaxy surveys with a uniform set of assumptions and find thatS _{8}from all three are lower than that from ACT+Planck lensing by levels ranging from 1.7σ to 2.1σ . This motivates further measurements and comparison, not just between the CMB anisotropies and galaxy lensing but also between CMB lensing probingz ∼ 0.5–5 on mostly linear scales and galaxy lensing atz ∼ 0.5 on smaller scales. We combine with CMB anisotropies to constrain extensions of ΛCDM, limiting neutrino masses to ∑m _{ν}< 0.13 eV (95% c.l.), for example. We describe the mass map and related data products that will enable a wide array of crosscorrelation science. Our results provide independent confirmation that the universe is spatially flat, conforms with general relativity, and is described remarkably well by the ΛCDM model, while paving a promising path for neutrino physics with lensing from upcoming groundbased CMB surveys. 
Abstract We present new measurements of cosmic microwave background (CMB) lensing over 9400 deg^{2}of the sky. These lensing measurements are derived from the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) CMB data set, which consists of five seasons of ACT CMB temperature and polarization observations. We determine the amplitude of the CMB lensing power spectrum at 2.3% precision (43
σ significance) using a novel pipeline that minimizes sensitivity to foregrounds and to noise properties. To ensure that our results are robust, we analyze an extensive set of null tests, consistency tests, and systematic error estimates and employ a blinded analysis framework. Our CMB lensing power spectrum measurement provides constraints on the amplitude of cosmic structure that do not depend on Planck or galaxy survey data, thus giving independent information about largescale structure growth and potential tensions in structure measurements. The baseline spectrum is well fit by a lensing amplitude ofA _{lens}= 1.013 ± 0.023 relative to the Planck 2018 CMB power spectra bestfit ΛCDM model andA _{lens}= 1.005 ± 0.023 relative to the ACT DR4 + WMAP bestfit model. From our lensing power spectrum measurement, we derive constraints on the parameter combination of ${S}_{8}^{\mathrm{CMBL}}\equiv {\sigma}_{8}{\left({\mathrm{\Omega}}_{m}/0.3\right)}^{0.25}$ from ACT DR6 CMB lensing alone and ${S}_{8}^{\mathrm{CMBL}}=0.818\pm 0.022$ when combining ACT DR6 and Planck ${S}_{8}^{\mathrm{CMBL}}=0.813\pm 0.018$NPIPE CMB lensing power spectra. These results are in excellent agreement with ΛCDM model constraints from Planck or ACT DR4 + WMAP CMB power spectrum measurements. Our lensing measurements from redshiftsz ∼ 0.5–5 are thus fully consistent with ΛCDM structure growth predictions based on CMB anisotropies probing primarilyz ∼ 1100. We find no evidence for a suppression of the amplitude of cosmic structure at low redshifts.