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Radiation from early black holes - I. Effects on the neutral intergalactic medium

Ripamonti, E. ; Mapelli, M. ; Zaroubi, S.

In: Monthly Notices of the Royal Astronomical Society, 2008, vol. 387, no. 1, p. 158-172

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    Title
    • Radiation from early black holes - I. Effects on the neutral intergalactic medium
    Author
    • Ripamonti, E.. Dipartimento di Fisica, Università di Milano-Bicocca, Piazza della Scienza 3, I-20123 Milano, Italy
    • Mapelli, M.. Institute for Theoretical Physics, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
    • Zaroubi, S.. Kapteyn Astronomical Institute, University of Groningen, Postbus 800, NL-9700AV Groningen, the Netherlands
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:295587
    Summary
    In the pre-reionization Universe, the regions of the intergalactic medium (IGM) which are far from luminous sources are the last to undergo reionization. Until then, they should be scarcely affected by stellar radiation; instead, the X-ray emission from an early black hole (BH) population can have much larger influence. We investigate the effects of such emission, looking at a number of BH model populations (differing for the cosmological density evolution of BHs, the BH properties, and the spectral energy distribution of the BH emission). We find that BH radiation can easily heat the IGM to 103-104K, while achieving partial ionization. The most interesting consequence of this heating is that BHs are expected to induce a 21-cm signal (δTb∼ 20-30 mK at z≲ 12) which should be observable with forthcoming experiments (e.g. LOFAR). We also find that at z≲ 10 BH emission strongly increases the critical mass separating star-forming and non-star-forming haloes