Hot and cold spots in the first plus second year {ital COBE}/DMR maps

Journal Article · Sun Oct 01 00:00:00 EDT 1995 · Astrophysical Journal

DOI:https://doi.org/10.1086/176321· OSTI ID:278632

Cayon, L; Smoot, G ^[1]

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1. Lawrence Berkeley Laboratory, Center for Particle Astrophysics, University of California, Berkeley, California 94720 (United States)

Density perturbations at the decoupling epoch produce angular fluctuations in the temperature of the cosmic microwave background (CMB) radiation that may appear as hot and cold spots. Observational data of the CMB include instrumental noise in addition to cosmological signal. One would like to determine which of the observed spots are produced by noise and which correspond to signal. In this work we first present a statistical analysis of the first plus second year {ital COBE}/DMR map at 53 GHz that reveals the presence of a cosmological signal in the data. The analysis is based on Harrison-Zeldovich Monte Carlo realizations and utilizes a generalized {chi}{sup 2} statistic. The method is applied to the number of spots and the fraction of the total area that appears above or below a certain value of the dispersion of the noise, including and excluding the quadrupole, giving {ital Q}{sub rms{minus}{ital PS}}=15{sup +3}{sub {minus}6}, 18{sup +5}{sub {minus}7} {mu}K and {ital Q}{sub rms{minus}{ital PS}}=18{sup +3}{sub {minus}4}, 21{plus_minus}6 {mu}K, respectively, at the 95{percent} confidence level. The data taken by the {ital COBE}/DMR experiment during the first 2 years at three different frequencies (31, 53, and 90 GHz) are used to determine which of the spots observed at 53 GHz appear simultaneously in the other two channels. The significance of those spots is determined by comparing their area and signal-to-noise ratio with noise Monte Carlo simulations. We point out two cold spots and one hot spot at positions ({ital l},{ital b}){approx_equal}({minus}99{degree}, 57{degree}), ({minus}21{degree}, {minus}45{degree}), ({minus}81{degree}, {minus}33{degree}) respectively, at the 95{percent} confidence level. {copyright} {ital 1995 The American Astronomical Society.}

• Research Organization: Lawrence Berkeley National Laboratory
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 278632
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 452; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ANGULAR DISTRIBUTION
ANISOTROPY
BACKGROUND RADIATION
DENSITY
FLUCTUATIONS
GHZ RANGE 01-100
HOT SPOTS
MICROWAVE RADIATION
MONTE CARLO METHOD
NOISE
PERTURBATION THEORY
SIGNAL-TO-NOISE RATIO
TEMPERATURE DISTRIBUTION
UNIVERSE