Small‐Scale Cosmic Microwave Background Observations at 8.4 GHz

1997 ◽  
Vol 483 (1) ◽  
pp. 38-50 ◽  
Author(s):  
R. Bruce Partridge ◽  
Eric A. Richards ◽  
Edward B. Fomalont ◽  
K. I. Kellerman ◽  
Rogier A. Windhorst
Keyword(s):  
Cosmic Microwave Background ◽  
Small Scale ◽  
Microwave Background

scholarly journals Isotropic non-Gaussian gNL-like toy models that reproduce cosmic microwave background anomalies

2019 ◽  
Vol 626 ◽  
pp. A13 ◽  
Author(s):  
F. K. Hansen ◽  
T. Trombetti ◽  
N. Bartolo ◽  
U. Natale ◽  
M. Liguori ◽  
...  
Keyword(s):  
Cosmic Microwave Background ◽  
Large Scale ◽  
Statistical Significance ◽  
Common Mechanism ◽  
Small Scale ◽  
Cold Spot ◽  
Microwave Background ◽  
Significance Level ◽  
Non Gaussian ◽  
Cmb Fluctuations

Context. Based on recent observations of the cosmic microwave background (CMB), claims of statistical anomalies in the properties of the CMB fluctuations have been made. Although the statistical significance of the anomalies remains only at the ∼2−3σ significance level, the fact that there are many different anomalies, several of which support a possible deviation from statistical isotropy, has motivated a search for models that provide a common mechanism to generate them. Aims. The goal of this paper is to investigate whether these anomalies could originate from non-Gaussian cosmological models, and to determine what properties these models should have. Methods. We present a simple isotropic, non-Gaussian class of toy models that can reproduce six of the most extensively studied anomalies. We compare the presence of anomalies found in simulated maps generated from the toy models and from a standard model with Gaussian fluctuations. Results. We show that the following anomalies, as found in the Planck data, commonly occur in the toy model maps: (1) large-scale hemispherical asymmetry (large-scale dipolar modulation), (2) small-scale hemispherical asymmetry (alignment of the spatial distribution of CMB power over all scales ℓ = [2, 1500]), (3) a strongly non-Gaussian hot or cold spot, (4) a low power spectrum amplitude for ℓ <  30, including specifically (5) a low quadrupole and an unusual alignment between the quadrupole and the octopole, and (6) parity asymmetry of the lowest multipoles. We note that this class of toy model resembles models of primordial non-Gaussianity characterised by strongly scale-dependent gNL-like trispectra.

scholarly journals Reconstructing small-scale lenses from the cosmic microwave background temperature fluctuations

2019 ◽  
Vol 485 (3) ◽  
pp. 3919-3929 ◽  
Author(s):  
Benjamin Horowitz ◽  
Simone Ferraro ◽  
Blake D Sherwin
Keyword(s):  
Maximum Likelihood ◽  
Cosmic Microwave Background ◽  
Matched Filter ◽  
Low Noise ◽  
Small Scale ◽  
Next Generation ◽  
Microwave Background ◽  
Likelihood Methods ◽  
Quadratic Estimator ◽  
Maximum Likelihood Methods

Abstract Cosmic microwave background (CMB) lensing is a powerful probe of the matter distribution in the Universe. The standard quadratic estimator, which is typically used to measure the lensing signal, is known to be suboptimal for low-noise polarization data from next-generation experiments. In this paper, we explain why the quadratic estimator will also be suboptimal for measuring lensing on very small scales, even for measurements in temperature where this estimator typically performs well. Though maximum likelihood methods could be implemented to improve performance, we explore a much simpler solution, revisiting a previously proposed method to measure lensing that involves a direct inversion of the background gradient. An important application of this simple formalism is the measurement of cluster masses with CMB lensing. We find that directly applying a gradient inversion matched filter to simulated lensed images of the CMB can tighten constraints on cluster masses compared to the quadratic estimator. While the difference is not relevant for existing surveys, for future surveys it can translate to significant improvements in mass calibration for distant clusters, where galaxy lensing calibration is ineffective due to the lack of enough resolved background galaxies. Improvements can be as large as ${\sim } 50{{\ \rm per\ cent}}$ for a cluster at z = 2 and a next-generation CMB experiment with 1 $\mu$K arcmin noise, and over an order of magnitude for lower noise levels. For future surveys, this simple matched filter or gradient inversion method approaches the performance of maximum likelihood methods, at a fraction of the computational cost.

scholarly journals New Limits to the Small Scale Fluctuations in the Cosmic Background Radiation

1983 ◽  
Vol 104 ◽  
pp. 125-126
Author(s):  
K. I. Kellermann ◽  
E. B. Fomalont ◽  
J. V. Wall
Keyword(s):  
Cosmic Microwave Background ◽  
Radio Source ◽  
Flux Density ◽  
Background Radiation ◽  
Cosmic Background Radiation ◽  
Small Region ◽  
Small Scale ◽  
Microwave Background ◽  
Cosmic Background ◽  
Microwave Background Radiation

The VLA has been used at 4.9 GHz to observe a small region of sky in order to extend the radio source count to low flux density (Fomalont et al., these proceedings) and to look for small scale fluctuations in the 2.7 K cosmic microwave background radiation.

scholarly journals Small‐Scale Cosmic Microwave Background Temperature and Polarization Anisotropies Due to Patchy Reionization

2003 ◽  
Vol 598 (2) ◽  
pp. 756-766 ◽  
Author(s):  
Mario G. Santos ◽  
Asantha Cooray ◽  
Zoltan Haiman ◽  
Lloyd Knox ◽  
Chung‐Pei Ma
Keyword(s):  
Cosmic Microwave Background ◽  
Small Scale ◽  
Microwave Background ◽  
Cosmic Microwave Background Temperature ◽  
Background Temperature
Sign in / Sign up

Export Citation Format

Share Document