ABSTRACT We calculate the constraints on dark energy and cosmic modifications to gravity achievable with upcoming cosmic microwave background (CMB) surveys sensitive to the Sunyaev-Zel'dovich (SZ) ...effects. The analysis focuses on using the mean pairwise velocity of clusters as observed through the kinematic SZ effect (kSZ), an approach based on the same methods used for the first detection of the kSZ effect, and includes a detailed derivation and discussion of this statistic's covariance under a variety of different survey assumptions. The potential of current, Stage II, and upcoming, Stages III and IV, CMB observations are considered, in combination with contemporaneous spectroscopic and photometric galaxy observations. A detailed assessment is made of the sensitivity to the assumed statistical and systematic uncertainties in the optical depth determination, the magnitude and uncertainty in the minimum detectable mass, and the importance of pairwise velocity correlations at small separations, where nonlinear effects can start to arise. In combination with Stage III constraints on the expansion history, such as those projected by the Dark Energy Task Force, we forecast 5% and 3% for fractional errors on the growth factor, γ, for Stage III and IV surveys, respectively, and 2% constraints on the growth rate, fg, for a Stage IV survey for . The results suggest that kSZ measurements of cluster peculiar velocities, obtained from cross-correlation with upcoming spectroscopic galaxy surveys, could provide robust tests of dark energy and theories of gravity on cosmic scales.
We construct cosmic microwave background lensing mass maps using data from
the 2014 and 2015 seasons of observations with the Atacama Cosmology Telescope
(ACT). These maps cover 2100 square degrees ...of sky and overlap with a wide variety
of optical surveys. The maps are signal dominated on large scales and have fidelity
such that their correlation with the cosmic infrared background is clearly visible by
eye. We also create lensing maps with thermal Sunyaev-Zel’dovich contamination
removed using a novel cleaning procedure that only slightly degrades the lensing
signal-to-noise ratio. The cross-spectrum between the cleaned lensing map and the
BOSS CMASS galaxy sample is detected at 10-σ significance, with an amplitude of
A = 1.02±0.10 relative to the Planck best-fit LCDM cosmological model with fiducial
linear galaxy bias. Our measurement lays the foundation for lensing cross-correlation
science with current ACT data and beyond.
We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest ...Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CL J0102-4915 as the most significant SZ decrement in a sky survey area of 755 deg super(2). Our Very Large Telescope (VLT)/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, sigma sub(gal) = 1321 + or - 106 km s super(-1). Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T sub(X) = 14.5 + or - 0.1 keV and 0.5-2.0 keV band luminosity of L sub(X) = (2.19 + or - 0.11) x 10 super(45) h super(-2) sub(70) erg s super(-1). We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y sub(X), and integrated SZ distortion, we estimate a cluster mass of M sub(200)a = (2.16 + or - 0.32) x 10 super(15) h super(-1) sub(70) M sub(middot in circle). We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CL J0102-4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6.6 + or - 0.7 keV at the merging low-entropy, high-metallicity, cool core to a high of 22 + or - 6 keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other. Archival radio data at 843 MHz reveal diffuse radio emission that, if associated with the cluster, indicates the presence of an intense double radio relic, hosted by the highest redshift cluster yet. ACT-CL J0102-4915 is possibly a high-redshift analog of the famous Bullet cluster. Such a massive cluster at this redshift is rare, although consistent with the standard LambdaCDM cosmology in the lower part of its allowed mass range. Massive, high-redshift mergers like ACT-CL J0102-4915 are unlikely to be reproduced in the current generation of numerical N-body cosmological simulations.
Abstract We present arcminute-resolution intensity and polarization maps of the Galactic center made with the Atacama Cosmology Telescope. The maps cover a 32 deg 2 field at 98, 150, and 224 GHz with ...∣ l ∣ ≤ 4°, ∣ b ∣ ≤ 2°. We combine these data with Planck observations at similar frequencies to create coadded maps with increased sensitivity at large angular scales. With the coadded maps, we are able to resolve many known features of the Central Molecular Zone (CMZ) in both total intensity and polarization. We map the orientation of the plane-of-sky component of the Galactic magnetic field inferred from the polarization angle in the CMZ, finding significant changes in morphology in the three frequency bands as the underlying dominant emission mechanism changes from synchrotron to dust emission. Selected Galactic center sources, including Sgr A*, the Brick molecular cloud (G0.253+0.016), the Mouse pulsar wind nebula (G359.23-0.82), and the Tornado supernova remnant candidate (G357.7-0.1), are examined in detail. These data illustrate the potential for leveraging ground-based cosmic microwave background polarization experiments for Galactic science.
We present a catalog of 182 galaxy clusters detected through the Sunyaev-Zel'dovich (SZ) effect by the Atacama Cosmology Telescope in a contiguous 987.5 deg2 field. The clusters were detected as SZ ...decrements by applying a matched filter to 148 GHz maps that combine the original ACT equatorial survey with data from the first two observing seasons using the ACTPol receiver. Optical/IR confirmation and redshift measurements come from a combination of large public surveys and our own follow-up observations. Where necessary, we measured photometric redshifts for clusters using a pipeline that achieves accuracy Δz/(1 + z) = 0.015 when tested on Sloan Digital Sky Survey data. Under the assumption that clusters can be described by the so-called universal pressure profile (UPP) and its associated mass scaling law, the full signal-to-noise ratio > 4 sample spans the mass range , with median . The sample covers the redshift range 0.1 < z < 1.4 (median z = 0.49), and 28 clusters are new discoveries (median z = 0.80). We compare our catalog with other overlapping cluster samples selected using the SZ, optical, and X-ray wavelengths. We find that the ratio of the UPP-based SZ mass to richness-based weak-lensing mass is . After applying this calibration, the mass distribution for clusters with M500c > 4 × 1014 M is consistent with the number of such clusters found in the South Pole Telescope SZ survey.
Abstract
We report on the serendipitous discovery of three transient millimeter-wave sources using data from the Atacama Cosmology Telescope. The first, detected at R.A
.
= 273.8138, decl. = −49.4628 ...at ∼50
σ
total, brightened from less than 5 mJy to at least 1100 mJy at 150 GHz with an unknown rise time shorter than 13 days, during which the increase from 250 mJy to 1100 mJy took only 8 minutes. Maximum flux was observed on 2019 November 8. The source’s spectral index in flux between 90–150 GHz was positive,
α
= 1.5 ± 0.2. The second, detected at R.A. = 105.1584, decl
.
= −11.2434 at ∼20
σ
total, brightened from less than 20 mJy to at least 300 mJy at 150 GHz with an unknown rise time shorter than 8 days. Maximum flux was observed on 2019 December 15. Its spectral index was also positive,
α
= 1.8 ± 0.2. The third, detected at R.A
.
= 301.9952, decl. = 16.1652 at ∼40
σ
total, brightened from less than 8 mJy to at least 300 mJy at 150 GHz over a day or less but decayed over a few days. Maximum flux was observed on 2018 September 11. Its spectrum was approximately flat, with a spectral index of
α
= −0.2 ± 0.1. None of the sources were polarized to the limits of these measurements. The two rising-spectrum sources are coincident in position with M and K stars, while the third is coincident with a G star.
PDF
