Simulations and Analytic Calculations of Bubble Growth during Hydrogen Reionization

By Oliver Zahn, A. Lidz, M. McQuinn, S. Dutta, L. Hernquist, M. Zaldarriaga, S. Furlanetto. 2006

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We present results from a large volume simulation of hydrogen reionization. We combine 3D radiative transfer calculations and an N-body simulation, describing structure formation in the intergalactic medium, to detail the growth of H II regions around high-redshift galaxies. Our simulation tracks 10243 dark matter particles, in a box of comoving side length 65.6 Mpc h-1. This large volume allows us to accurately characterize the size distribution of H II regions throughout most of the reionization process. At the same time, our simulation resolves many of the small galaxies likely responsible for reionization. It confirms a picture anticipated by analytic models: H II regions grow collectively around highly clustered sources and have a well-defined characteristic size, which evolves from a sub-Mpc scale at the beginning of reionization to R > 10 Mpc toward the end. We present a detailed statistical description of our results and compare them with a numerical scheme based on the analytic model by Furlanetto and coworkers. We find that the analytic calculation reproduces the size distribution of H II regions and the 21 cm power spectrum of the radiative transfer simulation remarkably well. The ionization field from the simulation, however, has more small-scale structure than the analytic calculation, owing to Poisson scatter in the simulated abundance of galaxies on small scales. We propose and validate a simple scheme to incorporate this scatter into our calculations. Our results suggest that analytic calculations are sufficiently accurate to aid in predicting and interpreting the results of future 21 cm surveys. In particular, our fast numerical scheme is useful for forecasting constraints from future 21 cm surveys and in constructing mock surveys to test data analysis procedures.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/5e9217934ffe9312742ca2cd484d8f5c9475ee2d

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Citations in the corpus

He ii REIONIZATION AND ITS EFFECT ON THE INTERGALACTIC MEDIUM (2008, background): “…reionization, current models find that the growth of ionized bubbles is more collective; hundreds or even thousands of galaxies within a bubble contribute to its growth, leading to the bubble structure tracing the distribution of galaxies and to tens of Mpc HII regions (e.g., Zahn et al. 2007).”
Inside-out or outside-in: the topology of reionization in the photon-starved regime suggested by Lyα forest data (2008, methodology): “The models predict the spatial distribution of the (integrated) ionizing emissivity as well as the spatial distribution of ionized regions (Zahn et al. 2007; Mesinger & Furlanetto 2007; Geil & Wyithe 2008).”
LOFAR: The LOw-Frequency ARray (2013, background): “…that we may expect an evolving complex patch work of neutral (HI) and ionized hydrogen (HII) regions (Gnedin & Abel 2001; Ciardi et al. 2003; Whalen & Norman 2006; Mellema et al. 2006; Zahn et al. 2007; Mesinger & Furlanetto 2007; Thomas et al. 2009; Thomas & Zaroubi 2011; Ciardi et al. 2012).”
The Halo Mass Function: High-Redshift Evolution and Universality (2007, methodology): “…(Jenkins, Reed et al. 2003, ST, orWarren) at low redshift (Reed et al. 2003, 2007; Springel et al. 2005; Heitmann et al. 2006a; Maio et al. 2006; Zahn et al. 2007) or consistent with the PS fit (Jang-Condell & Hernquist 2001; Yoshida et al. 2003a, 2003b, 2003c; Cen et al. 2004; Iliev et al.…”
Early Cosmological H II/He III Regions and Their Impact on Second-Generation Star Formation (2006, background): “…early H ii regions determine the global topology of the distribution of neutral and ionized gas at different epochs (e.g.,McQuinn et al. 2005, 2007; Zahn et al. 2005, 2007), which can be probed by future ground-based radio observations; turned around, the observations will provide rich information…”
PAPER-64 CONSTRAINTS ON REIONIZATION: THE 21 cm POWER SPECTRUM AT z = 8.4 (2015, background): “Our results become more interesting in the range of kmin ∼ 0.1 and kmax ∼ 30 representative of fiducial simulations (Zahn et al. 2007; Lidz et al. 2008).”
Evolution of the Intergalactic Opacity: Implications for the Ionizing Background, Cosmic Star Formation, and Quasar Activity (2008, background): “This gives credibility to analytical and numerical calculations of hydrogen reionization that make this assumption (e.g., Sokasian et al. 2003b; Furlanetto et al. 2004; McQuinn et al. 2007b; Zahn et al. 2007).”
The Evolution of the Intergalactic Medium (2015, background): “…predictions for the structure of reionization in semi-analytic models and large-box simulations have been shown to be in fantastic agreement with one another (Zahn et al. 2007; Santos et al. 2008; Zahn et al. 2011), although these models themselves are not without controversy, as discussed shortly.”
Reionization and Cosmology with 21-cm Fluctuations (2009, methodology): “Mesinger & Furlanetto (2007) then estimate the ionization field based on a catalogue of sources assigned within the halo field (an idea previously used by Zahn et al. 2007) by applying a filtering technique based on the analytic bubble model.”
New Limits on 21cm EoR From PAPER-32 Consistent with an X-Ray Heated IGM at z=7.7 (2013, background): “…and 2) we do not know whether the ionization fraction at z ≈ 8 is near to the ionization fractions we investigate (although models such as Zahn et al. 2007 and Lidz et al. 2008 do predict xi = 0.5 near z ≈ 8), the implication of our measurements is that the IGM may have been heated…”
THE PRECISION ARRAY FOR PROBING THE EPOCH OF RE-IONIZATION: EIGHT STATION RESULTS (2009, background): “The brightness temperatures of polarized galactic synchrotron emission, continuum point-sources, and galactic/extra-galactic free-free emission can exceed the expected ∼10 mK fluctuations of the 21cm EoR signal by more than 5 orders of magnitude (Zahn et al. 2007; Santos et al. 2005).”
INTENSITY MAPPING WITH CARBON MONOXIDE EMISSION LINES AND THE REDSHIFTED 21 cm LINE (2011, methodology): “For this calculation, we use the Sheth-Tormen (2001) mass function to calculate the collapse fraction, since this formula matches the abundance of simulated dark matter halos at high redshifts fairly well (e.g. Zahn et al. 2007).”
Simulating cosmic reionization: how large a volume is large enough? (2013, methodology): “…based on different approaches: the friends-of-friends (FOF) method (Iliev et al. 2006; Friedrich et al. 2011), the spherical average method (SPA, Zahn et al. 2007; McQuinn et al. 2007) and the three-dimensional power spectra of the ionization fraction field (Iliev et al. 2006; Friedrich et al.…”
The GMRT Epoch of Reionization experiment: a new upper limit on the neutral hydrogen power spectrum at z≈ 8.6 (2010, background): “…patchy topology is well motivated by theory and simulations ⋆ Email:paciga@astro.utoronto.ca † Email:pen@cita.utoronto.ca (e.g. Furlanetto et al. 2004; Iliev et al. 2006; McQuinn et al. 2007; Zahn et al. 2007; see Trac & Gnedin 2009 for a review) though the exact properties are poorly constrained.”
21cmfast: a fast, seminumerical simulation of the high‐redshift 21‐cm signal (2010, methodology): “This difference is mostly attributable to the bubbleflagging algorithm; in general the ‘flagging-the-entire-sphere’ algorithm of MF07 better reproduces H II morphological structure than the ‘flagging-the-central-cell’ algorithm of Zahn et al. (2007) (e.g. MF07).”