X-ray pre-ionization powered by accretion on the first black holes – I. A model for the WMAP polarization measurement

By M. Ricotti, Jeremiah P. Ostriker. 2003

186 citations recorded by the source corpus.

In this paper we investigate the possibility that there is a first phase of partial ionization due to X-rays produced by black hole (BH) accretion in small-mass galaxies at redshifts 7 < z < 20. This is followed by complete reionization by stellar sources at z ≃ 7. This scenario is motivated by the large optical depth to Thomson scattering, τ e ≃ 0.17 ± 0.04, recently measured by the Wilkinson Microwave Anisotropy Probe (WMAP). However, it is also consistent with the observed Gunn-Peterson trough in the spectra of quasars at z ∼ 5-6. We use a semi-analytic code to explore models with different BH accretion histories and cosmological parameters. We find that 'pre-ionization' by X-rays can increase the intergalactic medium (IGM) optical depth from τ e 0.06 given by stellar sources only, to 0.1 < τ e < 0.2, if a fraction of baryons 10 -5 < ω ac < 10 -4 is accreted on to seed BHs produced in the collapse of low-metallicity, high-mass stars before z ≃ 15. To be effective, pre-ionization requires a non-negligible star formation in the first small-mass galaxies in which seed BHs are formed. By z ∼ 20-25 the IGM is reheated to 10 000 K and the ionization fraction is about 20 per cent. The increase of the IGM Jeans mass is effective in reducing star formation in the smaller mass haloes. Large values of τ e are obtained in models with top-heavy stellar initial mass function only if pair-instability supernovae (SNe) are not important. Seed BHs are assumed to accrete at near the Eddington limit with a duty cycle that decreases slowly with increasing time. Alternatively, a moderate fraction of the black holes must be ejected from the host galaxy or exist without merging into the supermassive BHs in galactic centres. The model predicts that dwarf spheroidal galaxies, if they are preserved fossils of the first galaxies, may host a mass in BHs that is 5-40 per cent of their stellar mass. The redshifted X-ray background produced by this early epoch of BH accretion constitutes about 5-10 per cent of the hard X-ray background in the 2-50 keV bands and roughly half of the currently estimated BH mass density was formed at early times. Moreover, in most models, the photons from the redshifted background are sufficient to fully reionize He II at redshift z ∼ 3 without any additional contribution from quasars at lower redshifts and the temperature of the mean density IGM remains close to 10 4 K down to redshift z ∼ 1.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/6925fd967e02c2bd4d557a9e7539fa3ca56f65f3

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In Astronomy and Astrophysics

1. M. McQuinn
2. L. Hernquist
3. A. Mesinger
4. M. Volonteri
5. A. Ferrara
6. S. Furlanetto
7. Volker Bromm
8. John H. Wise

In Nuclear and High Energy Physics

1. A. Mesinger
2. J. Pritchard
3. S. Furlanetto
4. A. Ferrara
5. M. McQuinn
6. Abraham Loeb
7. M. Dijkstra
8. C. Carilli

Citations in the corpus

• Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Implications for Cosmology (2006, unknown): “…physics of reionization has been a subject of extensive theoretical study (Cen 2003; Ciardi et al. 2003; Haiman & Holder 2003; Madau et al. 2004; Oh & Haiman 2003; Venkatesan et al. 2003; Ricotti & Ostriker 2004; Sokasian et al. 2004; Somerville & Livio 2003; Wyithe & Loeb 2003; Iliev et al. 2005).”
• The aftermath of the first stars: massive black holes (2006, background): “…onto these black holes has important consequences for theories of the reionization of the Universe by miniquasars, as it is often assumed that accretion at the Eddington rate is achievable for miniquasars at redshifts z >∼ 15 (see Madau et al. 2004; Ricotti & Ostriker 2004; Kuhlen & Madau 2005).”
• 21 cm cosmology in the 21st century (2011, background): “In reality, of course, their evolution could be considerably more complex [69, 70].”
• Observational Constraints on Cosmic Reionization (2006, background): “High-energy X-ray photons from mini-quasars or supernova remnants at highredshift could also contribute significantly to the reionization process (Oh 2001; Venkatesan et al. 2001; Madau et al. 2004; Ricotti & Ostriker 2004).”
• Reionization and Cosmology with 21-cm Fluctuations (2009, background): “For ionization fractions & 10%, ionization by secondary electrons becomes inefficient (Ricotti & Ostriker 2004) and X-ray ionization is self regulating at the level of ∼ 10 − 20%.”
• Supermassive black hole formation during the assembly of pre-galactic discs (2006, background): “…stars that form with an initial mass function that is biased towards higher masses (Abel et al. 2000; Bromm et al. 2002) provide the initial seed black holes with masses of the order of a 10’s to 100 M⊙ (Madau & Rees 2001; Volonteri et al. 2003; Ricotti & Ostriker 2004; Mapelli et al. 2006).”
• 21-cm fluctuations from inhomogeneous X-ray heating before reionization (2006, background): “…& Loeb 2004), resonant scattering of Lyα photons (Madau, Meiksin & Rees 1997; Chen & MiraldaEscudé 2004; Furlanetto & Pritchard 2006; Meiksin 2006; Rybicki 2006; Chuzhoy & Shapiro 2007) and X-ray heating (Ostriker & Gnedin 1996; Oh 2001; Venkatesan, Giroux & Shull 2001; Ricotti & Ostriker 2004).”
• CRITICAL STAR FORMATION RATES FOR REIONIZATION: FULL REIONIZATION OCCURS AT REDSHIFT z ≈ 7 (2012, background): “One can also invoke a partially ionized IGM at zrei > 7, as discussed by many groups (Cen 2003; Venkatesan et al. 2003; Ricotti & Ostriker 2004; Benson et al. 2006; Shull & Venkatesan 2008).”
• Signatures of X-rays in the early Universe (2012, background): “Therefore, if X-rays were abundant in the early Universe, thermal feedback might delay the end stages of reionization (e.g. Ricotti & Ostriker 2004; Kuhlen & Madau 2005).”
• Feedback-regulated star formation and escape of LyC photons from mini-haloes during reionization (2016, background): “…active galactic nuclei (e.g., Shapiro & Giroux 1987; Haiman & Loeb 1998), accretion shock (Dopita et al. 2011), globular clusters (Ricotti 2002; Katz & Ricotti 2013, 2014), and X-rays from accreting stellar-mass black holes (e.g., Madau et al. 2004; Ricotti & Ostriker 2004; Mirabel et al. 2011).”
• ACCRETION ONTO THE FIRST STELLAR-MASS BLACK HOLES (2007, background): “…that accretion onto these black holes could power miniquasars has received a great deal of attention lately, since their radiation could have significantly increased the ionizing photon budget of the universe and extended the reionization process (Ricotti & Ostriker 2004; Madau et al. 2004).”
• Keeping the Universe ionized: photoheating and the clumping factor of the high-redshift intergalactic medium (2008, background): “An early population of X-ray sources, for example, could reheat the IGM to temperatures ∼ 104 K already at much higher redshifts (e.g. Collin-Souffrin 1991; Madau & Efstathiou 1999; Oh 2001; Venkatesan, Giroux, & Shull 2001; Machacek, Bryan, & Abel 2003; Madau et al. 2004; Ricotti & Ostriker 2004).”