1998/07/30 by E. M. Leitch, Leitch, E. M., A. C. S. Readhead +9
Physics and Astronomy · #Astrophysics (astro-ph) #Astrophysics and Cosmic Phenomena #Cosmology and Gravitation Theories #FOS: Physical sciences #Radio Astronomy Observations and Technology #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9807312
Revisions to match the published version, ApJ, 532: 37-56. Latex, emulateapj.sty, 22 pages, 21 Postscript figures
openalex publication_date 1998/07/30 · arxiv created 2000/10/18 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We report a measurement of anisotropy in the cosmic microwave background radiation (CMBR) on 7-22 arcminute scales. Observations of 36 fields near the North Celestial Pole (NCP) were made at 31.7 and 14.5 GHz, using the 5.5-meter and 40-meter telescopes at the Owens Valley Radio Observatory (OVRO) from 1993 to 1996. Multi-epoch VLA observations at 8.5 and 15 GHz allow removal of discrete source contamination. After point-source subtraction, we detect significant structure, which we identify with emission from a combination of a steep-spectrum foreground and the CMBR. The foreground component is found to correlate with IRAS 100 micron dust emission. Lack of H-alpha emission near the NCP suggests that this foreground is either high-temperature thermal bremsstrahlung (Te ~ 106 K), flat-spectrum synchrotron or an exotic component of dust emission. On the basis of low-frequency maps of the NCP, we can restrict the spectral index of the foreground to beta >= -2.2. Although the foreground signal dominates at 14.5 GHz, the extracted CMBR component contributes 88% of the variance at 31.7 GHz, yielding an rms fluctuation amplitude of 82+12.1-9.1 microKelvin, including 4.3% calibration uncertainty and 12% sample variance (68% confidence). The equivalent broadband amplitude is dTle = 59+8.6-6.5 microKelvin at le = 589. This measurement, when combined with small angular-scale upper limits obtained at the OVRO, indicates that the CMBR angular power spectrum decreases between l ~ 600 and l ~ 2000 and is consistent with flat cosmological models.