Heating and ionization of the primordial intergalactic medium by high mass x-ray binaries

Knevitt, G. and Wynn, G.A. and Power, C. and Bolton, James S. (2014) Heating and ionization of the primordial intergalactic medium by high mass x-ray binaries. Monthly Notices of the Royal Astronomical Society, 445 (2). pp. 2034-2048. ISSN 1365-2966

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Abstract

We investigate the influence of high-mass X-ray binaries (HMXBs) on their high-redshift environments. Using a one-dimensional radiative transfer code, we predict the ionization and temperature profiles surrounding a coeval stellar population, composed of main-sequence stars and HMXBs, at various times after its formation. We consider both uniform density surroundings, and a cluster embedded in a 108 M⊙ Navarro–Frenk–White (NFW) halo. HMXBs in a constant density environment produce negligible enhanced ionization because of their high-energy spectral energy distributions and short lifetimes. In this case, HMXBs only marginally contribute to the local heating rate. For NFW profiles, radiation from main-sequence stars cannot prevent the initially ionized volume from recombining since it is unable to penetrate the high-density galactic core. However, HMXB photons stall recombinations behind the front, keeping it partially ionized for longer. The increased electron density in these partially ionized regions promotes further cooling, resulting in lower intergalactic medium (IGM) temperatures. In the context of this starburst model, we have shown that HMXBs do not make a major contribution to reionization or IGM heating. However, X-ray escape fractions are high in both density profile cases. Continuous star formation may result in the build up of X-rays over time, reducing the ionization time-scale and potentially leading to low level ionization of the distant IGM.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2014 The authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Keywords: Galaxies: formation, Cosmology: theory, X-rays: binaries
Schools/Departments: University of Nottingham, UK > Faculty of Science > School of Physics and Astronomy
Identification Number: 10.1093/mnras/stu1803
Depositing User: Bolton, James
Date Deposited: 04 May 2017 13:30
Last Modified: 04 May 2017 13:33
URI: http://eprints.nottingham.ac.uk/id/eprint/42505

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