2004/04/03 by J. Chluba, R. A. Sunyaev · 2 citations
Physics and Astronomy · #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Particle physics theoretical and experimental studies #astro-ph
paper · pdf · doi:10.1051/0004-6361:20041016
published as Astron.Astrophys. 424 (2003) 389-408 · 20 pages, 11 figures, submitted to Astronomy and Astrophysics
arxiv created 2004/04/03 · openalex publication_date 2004/08/23 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
The CMB angular temperature fluctuations observed by Cobe and Wmap enable us to place a lower limit on the spectral distortions of the CMB at any angular scale. These distortions are connected with the simple fact that the superposition of blackbodies with different temperatures in general is not a blackbody. We show that in the limit of small temperature fluctuations the superposition of blackbodies leads to a y-type spectral distortion. It is known that the CMB dipole induces a y-type spectral distortion with quadrupole and monopole angular distribution leading to a corresponding whole sky y-parameter of . We show here that taking the difference of the CMB signal in the direction of the maximum and minimum of the CMB dipole due to the superposition of two blackbodies leads to a spectral distortion with . The amplitude of this distortion can be calculated to the same precision as the CMB dipole, i.e. today. Therefore it may be used as a source with brightness of several or tens of μK to cross calibrate and calibrate different frequency channels of CMB surveys with a precision of a few tens or hundreds of nK. We also discuss clusters of galaxies as possible sources for calibration purposes. Furthermore, we show in this work that primordial anisotropies for multipoles also lead to spectral distortions but with a much smaller y-parameter, i.e. .