Inside-out or outside-in: the topology of reionization in the photon-starved regime suggested by Lyα forest data

By T. R. Choudhury, M. Haehnelt, J. Regan. 2008

170 citations recorded by the source corpus.

We use a set of seminumerical simulations based on the Zel'dovich approximation, the friends-of-friends algorithm and excursion set formalism to generate reionization maps of high dynamic range with a range of assumptions regarding the distribution and luminosity of ionizing sources and the spatial distribution of sinks for the ionizing radiation. We find that ignoring the inhomogeneous spatial distribution of regions of high gas density where recombinations are important - as is often done in studies of this kind - can lead to misleading conclusions regarding the topology of reionization, especially if reionization occurs in the photon-starved regime suggested by Lya forest data. The inhomogeneous spatial distribution of recombinations significantly reduces the mean-free path of ionizing photons and the typical size of coherently ionized regions. Reionization proceeds then much more as an outside-in process. Low-density regions far from ionizing sources become ionized before regions of high gas density not hosting sources of ionizing radiation. The spatial distribution of sinks of ionization radiation also significantly affects the shape and amplitude of the power spectrum of fluctuations of 21 cm emission. The slope of the 21 cm power spectrum as measured by upcoming 21 cm experiments should be able to distinguish to what extent the topology of reionization proceeds outside-in or inside-out, while the evolution of the amplitude of the power spectrum with increasing ionized mass fraction should be sensitive to the spatial distribution and the luminosity of ionizing sources.

Subfields: Astronomy and Astrophysics, Biophysics, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/5aeead5eb57ab090e5bb9bd0205b6a5f0bdb3db6

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Citations in the corpus

The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization (2015, background): “…jppaarde@uni-heidelberg.de population to reionisation (e.g. Bouwens et al. 2012; Robertson et al. 2013), semi-analytic modelling of reionisation (e.g. Choudhury et al. 2009; Pritchard et al. 2010; Santos et al. 2010; Mesinger et al. 2011; Raskutti et al. 2012; Mitra et al. 2013; Shull et al. 2012)…”
COSMIC MICROWAVE BACKGROUND CONSTRAINTS ON THE DURATION AND TIMING OF REIONIZATION FROM THE SOUTH POLE TELESCOPE (2011, methodology): “…state-of-the-art reionization simulations, and are typically included via analytic prescriptions (e.g., Furlanetto & Oh 2005; McQuinn et al. 2007b; Choudhury et al. 2009; Crociani et al. 2011). several groups to develop much more CPU efficient, approximate algorithms (Furlanetto et al. 2004; Zahn…”
Signatures of X-rays in the early Universe (2012, background): “A physical choice for Rmax corresponds to the mean free path of ionizing photons,Rmfp (Furlanetto & Oh 2005; Choudhury et al. 2009; Alvarez & Abel 2012).”
Inhomogeneous recombinations during cosmic reionization (2014, methodology): “Instead if the (mass-weighted) neutral fraction of the entire ∼ 1 Mpc simulation cell was set to unity, the reionization morphology could be noticeably changed on small-scales (Choudhury et al. 2009; Crociani et al. 2011).”
Evidence of patchy hydrogen reionization from an extreme Lyα trough below redshift six (2014, background): “…the local mean free path will still evolve rapidly and exhibit a degree of spatial variance as residual patches of neutral hydrogen and/or Lyman limit systems at the edges of H ii regions are ionized (e.g., Furlanetto & Oh 2005; Choudhury et al. 2009; Alvarez & Abel 2012; Sobacchi & Mesinger 2014).”
Comparison of reionization models: radiative transfer simulations and approximate, seminumeric models (2010, background): “This semi-numerical scheme can be extended to contain additional physics such as spatially inhomogeneous recombinations (Choudhury et al. 2009), a mass dependent ionization efficiency (Furlanetto et al. 2006a), and radiative feedback (Geil & Wyithe 2008).”
21cmfast: a fast, seminumerical simulation of the high‐redshift 21‐cm signal (2010, background): “This approach to generating large-scale density fields was also adopted by Choudhury et al. (2009) and Santos et al. (2009), who briefly showed that the resulting fields at high z traced the DM distribution from an N-body code fairly well.”
NEW CONSTRAINTS ON COSMIC REIONIZATION FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN (2013, background): “…the IGM (Miralda-Escudé et al. 2000; Bolton & Becker 2009); (3) accounts for spatial structure in the averaged transmission measurements (Lidz et al. 2006); and (4) predicts the topology of ionized and neutral regions at the tail end of reionization (Furlanetto et al. 2004b; Choudhury et al. 2009).”