Radiative Transfer Simulations of Cosmic Reionization. I. Methodology and Initial Results

By Hy Trac, Renyue Cen. 2006

215 citations recorded by the source corpus.

We present a new hybrid code for large-volume, high-resolution simulations of cosmic reionization, which utilizes an N-body algorithm for dark matter, physically motivated prescriptions for baryons and star formation, and an adaptive ray-tracing algorithm for radiative transfer of ionizing photons. Two test simulations, each with 3 billion particles and 400 million rays in a 50 Mpc h-1 box, have been run to give initial results. Halos are resolved down to virial temperatures of 104 K for the redshift range of interest in order to robustly model star formation and clumping factors. This is essential to correctly account for ionization and recombination processes. We find that the halos and sources are strongly biased with respect to the underlying dark matter, re-enforcing the requirement of large simulation boxes to minimize cosmic variance and to obtain a qualitatively correct picture of reionization. We model the stellar initial mass function (IMF) by following the spatially dependent gas metallicity evolution, and distinguish between the first generation, Population III (PopIII) stars and the second generation, Population II (PopII) stars. The PopIII stars with a top-heavy IMF produce an order of magnitude more ionizing photons at high redshifts z ≳ 10, resulting in a more extended reionization. In our simulations, complete overlap of H II regions occurs at z ≈ 6.5, and the computed mass- and volume-weighted residual H I fractions at 5 ≲ z ≲ 6.5 are both in good agreement with high-redshift quasar absorption measurements from the Sloan Digital Sky Survey (SDSS). The values for the Thomson optical depth are consistent within 1 - σ of the current best-fit value from third-year Wilkinson Microwave Anisotropy Probe (WMAP) results.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/b2e4aa3e1dcfdb3e0fe64665527157df7356137f

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Citations in the corpus

A case study of hurdle and generalized additive models in astronomy: the escape of ionizing radiation (2018, background): “…2013), semi-analytical (e.g. Choudhury, Haehnelt & Regan 2009; Pritchard, Loeb & Wyithe 2010; Santos et al. 2010; Mesinger, Furlanetto & Cen 2011; Shull et al. 2012a; Mitra, Ferrara & Choudhury 2013) as well as simulated (e.g. Iliev et al. 2006; Trac & Cen 2007; Ciardi et al. 2012) investigations.”
The birth of a galaxy – III. Propelling reionization with the faintest galaxies (2014, background): “…metal-free (Population III; Pop III) stars can contribute of the order of 10 per cent of the budget (Ricotti & Ostriker 2004a; Greif & Bromm 2006; Trac & Cen 2007; Wise & Abel 2008a; Ahn et al. 2012; Wise et al. 2012b; Johnson, Dalla & Khochfar 2013; Paardekooper, Khochfar & Dalla Vecchia 2013)…”
21cmfast: a fast, seminumerical simulation of the high‐redshift 21‐cm signal (2010, methodology): “…that the mean collapse fraction matches the ST collapse fraction (in agreement with N-body simulations; e.g. Jenkins et al. 2001; McQuinn et al. 2007; Trac & Cen 2007), while the fluctuations are sourced by the conditional PS model applied on the evolved density field.20 There is an implicit…”
IONIZING PHOTON ESCAPE FRACTIONS FROM HIGH-REDSHIFT DWARF GALAXIES (2008, unknown): “This quantity is an essential parameter in both semi-analytical reionization models (e.g. Cen 2003a,b; Wyithe & Loeb 2003a; Haiman & Holder 2003) and Nbody reionization simulations (e.g. Ciardi et al. 2003; Sokasian et al. 2003; Iliev et al. 2006; Trac & Cen 2007).”
A PER-BASELINE, DELAY-SPECTRUM TECHNIQUE FOR ACCESSING THE 21 cm COSMIC REIONIZATION SIGNATURE (2012, background): “Since ∆221(k) is expected to evolve on log k scales (McQuinn et al. 2007; Trac & Cen 2007), the width of τ -modes in the k‖-direction only becomes important on scales of ∆k ∼ k.”
The Evolution of the Intergalactic Medium (2015, background): “…towards modeling reionization (Gnedin & Ostriker 1997; Ciardi, Stoehr & White 2003; Furlanetto & Oh 2005; Iliev et al. 2006; McQuinn et al. 2007b; Trac & Cen 2007; Finlator et al. 2009; Gnedin 2014a; Thomas et al. 2009; Santos et al. 2010; Mesinger, Furlanetto & Cen 2011; Ciardi et al. 2012;…”
ON LYMAN-LIMIT SYSTEMS AND THE EVOLUTION OF THE INTERGALACTIC IONIZING BACKGROUND (2011, background): “In contrast with this result, simulations of reionization (e.g., Iliev et al. 2006; Trac & Cen 2007; Zahn et al. 2007) generally prescribe an emissivity history that is strongly decreasing with increasing redshift (Choudhury et al. 2009).”
He ii REIONIZATION AND ITS EFFECT ON THE INTERGALACTIC MEDIUM (2008, background): “For cosmological ray tracing codes, such small timesteps can be computationally intractable (although, see Trac & Cen 2007).”
Reionization and Cosmology with 21-cm Fluctuations (2009, methodology): “In large modern simulations, the most common approach to address this issue is to begin with an N-body code to generate a distribution of halos (e.g. Ciardi, Stoehr & White 2003, Sokasian et al. 2003, Iliev et al. 2007, Zahn et al. 2007, Trac & Cen 2007).”
Fast large volume simulations of the 21-cm signal from the reionization and pre-reionization epochs (2009, background): “…simulation), plus a full radiative transfer code to propagate the ionizing radiation (Gnedin 2000; Razoumov et al. 2002; Sokasian et al. 2003; Ciardi et al. 2003; Kohler et al. 2005; Iliev et al. 2006; Zahn et al. 2007; McQuinn et al. 2007; Shin et al. 2007; Trac & Cen 2007; Baek et al. 2009).”
Comparison of reionization models: radiative transfer simulations and approximate, seminumeric models (2010, methodology): “Red circles, green triangles, blue squares, and magenta pentagons correspond to the ionization algorithms of Trac & Cen (2007), McQuinn et al. (2007a), FFRT, and FFRT without Poisson fluctuations in the halo number (see §4), respectively.”
COSMIC MICROWAVE BACKGROUND CONSTRAINTS ON THE DURATION AND TIMING OF REIONIZATION FROM THE SOUTH POLE TELESCOPE (2011, background): “The effect on the patchy kSZ power spectrum of increasing the minimum source mass to 1010M (an increase of two orders of magnitude over the fiducial Mmin, discarding > 90% of sources, e.g., Trac & Cen 2007b) is shown in the black solid and dashed lines of Figure 2.”
CRITICAL STAR FORMATION RATES FOR REIONIZATION: FULL REIONIZATION OCCURS AT REDSHIFT z ≈ 7 (2012, background): “Although such a high redshift could be explained with ΛCDM simulations and modeled SFR histories (Choudhury & Ferrara 2005; Trac & Cen 2007; Shull & Venkatesan 2008), the CMB observations are at variance with optical surveys that suggest late reionization, unless reionization is a process that…”
ESCAPE FRACTION OF IONIZING PHOTONS DURING REIONIZATION: EFFECTS DUE TO SUPERNOVA FEEDBACK AND RUNAWAY OB STARS (2014, background): “…& Cen 2007; Kuhlen & Faucher-Giguère 2012; Robertson et al. 2013) and numerically (e.g.Gnedin 2000a; Razoumov et al. 2002; Ciardi et al. 2003; Fujita et al. 2003; Trac & Cen 2007; Gnedin et al. 2008; Wise & Cen 2009; Razoumov & Sommer-Larsen 2010; Yajima et al. 2011; Paardekooper et al. 2013).”
The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization (2015, background): “…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) and numerical simulations of reionisation (e.g. Iliev et al. 2006; Trac & Cen 2007; Ciardi et al. 2012).”
CANDELS: THE COSMIC ASSEMBLY NEAR-INFRARED DEEP EXTRAGALACTIC LEGACY SURVEY (2011, unknown): “The green curve is a model (Cooray et al. 2004; Trac & Cen 2007) that provides the star formation necessary to reionize the universe by z ≈ 7–8.”