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Abstract Uncertain feedback processes in galaxies affect the distribution of matter, currently limiting the power of weak lensing surveys. If we can identify cosmological statistics that are robust against these uncertainties, or constrain these effects by other means, then we can enhance the power of current and upcoming observations from weak lensing surveys such as DES, Euclid, the Rubin Observatory, and the Roman Space Telescope. In this work, we investigate the potential of the electron density auto-power spectrum as a robust probe of cosmology and baryonic feedback. We use a suite of (magneto-)hydrodynamic simulations from the CAMELS project and perform an idealized analysis to forecast statistical uncertainties on a limited set of cosmological and physically-motivated astrophysical parameters. We find that the electron number density auto-correlation, measurable through either kinematic Sunyaev-Zel'dovich observations or through Fast Radio Burst dispersion measures, provides tight constraints on Ω m and the mean baryon fraction in intermediate-mass halos, f̅ bar . By obtaining an empirical measure for the associated systematic uncertainties, we find these constraints to be largely robust to differences in baryonic feedback models implemented in hydrodynamic simulations. We further discuss the main caveats associated with our analysis, and point out possible directions for futuremore »work.« less

Abstract We describe the measurement and treatment of the telescope beams for the Atacama Cosmology Telescope's fourth data release, DR4. Observations of Uranus are used to measure the central portion (<12 ' ) of the beams to roughly -40 dB of the peak. Such planet maps in intensity are used to construct azimuthally averaged beam profiles, which are fit with a physically motivated model before being transformed into Fourier space. We investigate and quantify a number of percent-level corrections to the beams, all of which are important for precision cosmology. Uranus maps in polarization are used to measure the temperature-to-polarization leakage in the main part of the beams, which is ≲ 1% (2.5%) at 150 GHz (98 GHz). The beams also have polarized sidelobes, which are measured with observations of Saturn and deprojected from the ACT time-ordered data. Notable changes relative to past ACT beam analyses include an improved subtraction of the atmospheric effects from Uranus calibration maps, incorporation of a scattering term in the beam profile model, and refinements to the beam model uncertainties and the main temperature-to-polarization leakage terms in the ACT power spectrum analysis.

Abstract We use Atacama Cosmology Telescope (ACT) observations at 98 GHz (2015–2019), 150 GHz (2013–2019), and 229 GHz (2017–2019) to perform a blind shift-and-stack search for Planet 9. The search explores distances from 300 au to 2000 au and velocities up to 6.′3 per year, depending on the distance ( r ). For a 5 Earth-mass Planet 9 the detection limit varies from 325 au to 625 au, depending on the sky location. For a 10 Earth-mass planet the corresponding range is 425 au to 775 au. The predicted aphelion and most likely location of the planet corresponds to the shallower end of these ranges. The search covers the whole 18,000 square degrees of the ACT survey. No significant detections are found, which is used to place limits on the millimeter-wave flux density of Planet 9 over much of its orbit. Overall we eliminate roughly 17% and 9% of the parameter space for a 5 and 10 Earth-mass Planet 9, respectively. These bounds approach those of a recent INPOP19a ephemeris-based analysis, but do not exceed it. We also provide a list of the 10 strongest candidates from the search for possible follow-up. More generally, we exclude (at 95% confidence) themore »presence of an unknown solar system object within our survey area brighter than 4–12 mJy (depending on position) at 150 GHz with current distance 300 au < r < 600 au and heliocentric angular velocity 1 .′ 5 yr − 1 < v · 500 au r < 2 .″ 3 yr − 1 , corresponding to low-to-moderate eccentricities. These limits worsen gradually beyond 600 au, reaching 5–15 mJy by 1500 au.« less

Context. Galaxy clusters are an important tool for cosmology, and their detection and characterization are key goals for current and future surveys. Using data from the Wide-field Infrared Survey Explorer (WISE), the Massive and Distant Clusters of WISE Survey (MaDCoWS) located 2839 significant galaxy overdensities at redshifts 0.7 ≲  z  ≲ 1.5, which included extensive follow-up imaging from the Spitzer Space Telescope to determine cluster richnesses. Concurrently, the Atacama Cosmology Telescope (ACT) has produced large area millimeter-wave maps in three frequency bands along with a large catalog of Sunyaev-Zeldovich (SZ)-selected clusters as part of its Data Release 5 (DR5). Aims. We aim to verify and characterize MaDCoWS clusters using measurements of, or limits on, their thermal SZ effect signatures. We also use these detections to establish the scaling relation between SZ mass and the MaDCoWS-defined richness. Methods. Using the maps and cluster catalog from DR5, we explore the scaling between SZ mass and cluster richness. We do this by comparing cataloged detections and extracting individual and stacked SZ signals from the MaDCoWS cluster locations. We use complementary radio survey data from the Very Large Array, submillimeter data from Herschel , and ACT 224 GHz data to assess the impact of contaminating sourcesmore »on the SZ signals from both ACT and MaDCoWS clusters. We use a hierarchical Bayesian model to fit the mass-richness scaling relation, allowing for clusters to be drawn from two populations: one, a Gaussian centered on the mass-richness relation, and the other, a Gaussian centered on zero SZ signal. Results. We find that MaDCoWS clusters have submillimeter contamination that is consistent with a gray-body spectrum, while the ACT clusters are consistent with no submillimeter emission on average. Additionally, the intrinsic radio intensities of ACT clusters are lower than those of MaDCoWS clusters, even when the ACT clusters are restricted to the same redshift range as the MaDCoWS clusters. We find the best-fit ACT SZ mass versus MaDCoWS richness scaling relation has a slope of p 1 = 1.84 −0.14 +0.15 , where the slope is defined as M λ ∝ 15 p 1 and λ 15 is the richness. We also find that the ACT SZ signals for a significant fraction (∼57%) of the MaDCoWS sample can statistically be described as being drawn from a noise-like distribution, indicating that the candidates are possibly dominated by low-mass and unvirialized systems that are below the mass limit of the ACT sample. Further, we note that a large portion of the optically confirmed ACT clusters located in the same volume of the sky as MaDCoWS are not selected by MaDCoWS, indicating that the MaDCoWS sample is not complete with respect to SZ selection. Finally, we find that the radio loud fraction of MaDCoWS clusters increases with richness, while we find no evidence that the submillimeter emission of the MaDCoWS clusters evolves with richness. Conclusions. We conclude that the original MaDCoWS selection function is not well defined and, as such, reiterate the MaDCoWS collaboration’s recommendation that the sample is suited for probing cluster and galaxy evolution, but not cosmological analyses. We find a best-fit mass-richness relation slope that agrees with the published MaDCoWS preliminary results. Additionally, we find that while the approximate level of infill of the ACT and MaDCoWS cluster SZ signals (1–2%) is subdominant to other sources of uncertainty for current generation experiments, characterizing and removing this bias will be critical for next-generation experiments hoping to constrain cluster masses at the sub-percent level.« less

We report a significant detection of the hot intergalactic medium in the filamentary bridge connecting the galaxy clusters Abell 399 and Abell 401. This result is enabled by a low-noise, high-resolution map of the thermal Sunyaev–Zeldovich signal from the Atacama Cosmology Telescope (ACT) and Planck satellite. The ACT data provide the 1.65 arcmin resolution that allows us to clearly separate the profiles of the clusters, whose centres are separated by 37 arcmin, from the gas associated with the filament. A model that fits for only the two clusters is ruled out compared to one that includes a bridge component at >5σ. Using a gas temperature determined from Suzaku X-ray data, we infer a total mass of $(3.3\pm 0.7)\times 10^{14}\, \mathrm{M}_{\odot }$ associated with the filament, comprising about 8 per cent of the entire Abell 399–Abell 401 system. We fit two phenomenological models to the filamentary structure; the favoured model has a width transverse to the axis joining the clusters of ${\sim }1.9\, \mathrm{Mpc}$. When combined with the Suzaku data, we find a gas density of $(0.88\pm 0.24)\times 10^{-4}\, \mathrm{cm}^{-3}$, considerably lower than previously reported. We show that this can be fully explained by a geometry in which the axis joining Abell 399 and Abell 401more »has a large component along the line of sight, such that the distance between the clusters is significantly greater than the $3.2\, \mathrm{Mpc}$ projected separation on the plane of the sky. Finally, we present initial results from higher resolution (12.7 arcsec effective) imaging of the bridge with the MUSTANG-2 receiver on the Green Bank Telescope.

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