2002/08/07 by S. P. Boughn, R. G. Crittenden, G. P. Koehrsen
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Cluster analysis #Cosmic background radiation #Cosmic microwave background #Cosmology #Dark Matter and Cosmic Phenomena #Dark matter #Dipole #Galaxies: Formation, Evolution, Phenomena #Limit (mathematics) #Moment (physics) #Rest frame #Universe #astro-ph
paper · pdf · doi:10.1086/343861
published as Astrophys.J. 580 (2002) 672-684 · 15 pages, 8 postscript figures, to appear in the Astrophysical Journal. The postscript version appears not to print, so use the PDF version
arxiv created 2002/08/07 · openalex publication_date 2002/12/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
A careful analysis of the HEAO 1 A-2 2-10 keV full-sky map of the X-ray background (XRB) reveals clustering on the scale of several degrees. After removal of the contribution due to beam smearing, the intrinsic clustering of the background is found to be consistent with an autocorrelation function of the form (3.6 ± 0.9) × 10 -4 θ -1 , where θ is measured in degrees. If current active galactic nucleus models of the hard XRB are reasonable and the cosmological constant-cold dark matter (ΛCDM) cosmology is correct, this clustering implies an X-ray bias factor of b X ~ 2. Combined with the absence of a correlation between the XRB and the cosmic microwave background (CMB), this clustering can be used to limit the presence of an integrated Sachs-Wolfe (ISW) effect and thereby to constrain the value of the cosmological constant, Ω Λ ≤ 0.60 (95% CL). This constraint is inconsistent with much of the Ω Λ parameter space currently favored by other observations. Finally, we marginally detect the dipole moment of the diffuse XRB and find it to be consistent with the dipole due to our motion with respect to the mean rest frame of the XRB. The limit on the amplitude of any intrinsic dipole is δ I / I ≤ 5 × 10 -3 at the 95% CL. When compared to the local bulk velocity, this limit implies a constraint on the matter density of the universe of Ω / b X (0) ≳ 0.24.