2009/02/26 by Mark Dijkstra, Abraham Loeb
Physics and Astronomy · #Active galactic nucleus #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Galaxy #Intergalactic dust #Intergalactic travel #Opacity #Physics #Redshift #Supernova #astro-ph.CO
paper · pdf · doi:10.1111/j.1365-2966.2009.15102.x
6 pages, 4 figures
arxiv created 2009/02/26 · openalex publication_date 2009/07/06 · arxiv updated 2015/05/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Active galactic nuclei (AGN) produce a dominant fraction (FAGN∼ 80 per cent) of the soft X-ray background (SXB) at photon energies 0.5 < E < 2 keV. If dust pervaded throughout the intergalactic medium, its scattering opacity would have produced diffuse X-ray haloes around AGN. Taking account of known galaxies and galaxy clusters, only a fraction Fhalo≲ 10 per cent of the SXB can be in the form of diffuse X-ray haloes around AGN. We therefore limit the intergalactic opacity to optical/infrared photons from large dust grains, with radii in the range a= 0.2–2.0 μm, to a level τGD≲ 0.15(Fhalo/10 per cent)(FAGN/80 per cent)−1 to a redshift z∼ 1. Our results are only weakly dependent on the grain size distribution in this size range or the redshift evolution of the intergalactic dust. Stacking X-ray images of AGN can be used to improve our constraints and diminish the importance of dust as a source of systematic uncertainty for future supernova surveys which aim to improve the precision on measuring the redshift evolution of the dark energy equation-of-state.