Efficient Simulations of Early Structure Formation and Reionization

By A. Mesinger, S. Furlanetto. 2007

366 citations recorded by the source corpus.

Detailed theoretical studies of the high-redshift universe, and especially reionization, are generally forced to rely on time-consuming N-body codes and/or radiative transfer algorithms. We present a method to construct seminumerical "simulations," which can efficiently generate realizations of halo distributions and ionization maps at high redshifts. Our procedure combines an excursion-set approach with first-order Lagrangian perturbation theory and operates directly on the linear density and velocity fields. As such, the achievable dynamic range with our algorithm surpasses the current practical limit of N-body codes by orders of magnitude. This is particularly significant in studies of reionization, where the dynamic range is the principal limiting factor, because ionized regions reach scales of tens of comoving Mpc. We test our halo-finding and ionization-mapping algorithms separately against N-body simulations with radiative transfer and obtain excellent agreement. We compute the size distributions of ionized and neutral regions in our maps. We find even larger ionized bubbles than do purely analytic models at the same volume-weighted mean hydrogen neutral fraction, x̄H I, especially early in reionization. We also generate maps and power spectra of 21 cm brightness temperature fluctuations, which for the first time include corrections due to gas bulk velocities. We find that velocities widen the tails of the temperature distributions and increase small-scale power, although these effects quickly diminish as reionization progresses. We also include some preliminary results from a simulation run with the largest dynamic range to date: a 250 Mpc box that resolves halos with masses M ≥ 2.2 × 108 M☉. We show that accurately modeling the late stages of reionization, x̄H I ≲ 0.5, requires such large scales. The speed and dynamic range provided by our seminumerical approach will be extremely useful in the modeling of early structure formation and reionization.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/6637adbb01929d5e700cad0588770fbb7960ca6b

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Citations in the corpus

Fundamental physics with the Square Kilometre Array (2018, background): “…progress has been made in condensing these rich astrophysical effects into simple semi-analytical prescriptions that capture the large-scale features of the 21- cm signal during this period (Furlanetto et al., 2004a,b; Mesinger & Furlanetto, 2007; Mesinger et al., 2011; Visbal et al., 2012).”
INTENSITY MAPPING WITH CARBON MONOXIDE EMISSION LINES AND THE REDSHIFTED 21 cm LINE (2011, background): “Further, we ignore the impact of peculiar velocities which should not significantly influence our present calculations (Mesinger & Furlanetto 2007).”
Signatures of X-rays in the early Universe (2012, methodology): “We do not explicitly compute individual halo locations (as in Mesinger & Furlanetto 2007), but instead apply the conditional excursion-set formalism directly on the non-linear density field to compute fcoll (Zahn et al. 2011).”
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 First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization (2015, background): “The ionising emissivity of the sources is generally taken to scale with the mass of the halo (e.g. Trac & Cen 2007; Mesinger & Furlanetto 2007; Iliev et al. 2012).”
Fast large volume simulations of the 21-cm signal from the reionization and pre-reionization epochs (2009, methodology): “In this paper, we propose a semi-numerical technique, partially following the hybrid approach prescribed in Mesinger & Furlanetto (2007), capable of quickly generating an end-to-end simulation of the 21 cm signal even at high redshifts when the effect of the spin temperature is nonnegligible.”
21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal (2015, methodology): “It combines the astrophysical parameter sampler cosmohammer (Akeret et al. 2013), calling the seminumerical 21 cm simulation code 21CMFAST (Mesinger & Furlanetto 2007; Mesinger et al. 2011) at each point in the sampled EoR astrophysical parameter space.”
Quantitative Constraints on the Reionization History from the IGM Damping Wing Signature in Two Quasars at z > 7 (2018, methodology): “…algorithm assigns collapsed mass to each cell according to the non-linear density field, and it is this collapsed mass field which is filtered to determine whether a given region is ionized, similar to DexM (Mesinger & Furlanetto 2007) but without explicitly generating a distribution of halos.”
Inferring the astrophysics of reionization and cosmic dawn from galaxy luminosity functions and the 21-cm signal (2018, methodology): “To compute the various fields in the above equation, we use the semi-numerical simulation 21cmfast(Mesinger & Furlanetto 2007; Mesinger et al. 2011).”
NEW OBSERVATIONS OF z ∼ 7 GALAXIES: EVIDENCE FOR A PATCHY REIONIZATION (2014, methodology): “As in Dijsktra et al. (2011), reionization morphologies were generated using the public code, DexM (Mesinger & Furlanetto 2007).”
COSMIC MICROWAVE BACKGROUND CONSTRAINTS ON THE DURATION AND TIMING OF REIONIZATION FROM THE SOUTH POLE TELESCOPE (2011, methodology): “These regions can span tens of comoving Mpc in size towards the end of reionization (Furlanetto & Oh 2005; Zahn et al. 2005b, 2007; Mesinger & Furlanetto 2007; Shin et al. 2008).”
Lyα Emitting Galaxies as a Probe of Reionisation (2014, methodology): “…poorly known parameters related to galaxy formation, the ionising emissivity of starforming galaxies, their spectra etc. Alternative, faster ‘seminumeric’ algorithms have been developed which allow for a more efficient exploration of the full the parameter space (e.g. Mesinger & Furlanetto 2007).”
COMPLETING THE CENSUS OF Lyα EMITTERS AT THE REIONIZATION EPOCH (2011, background): “…model predictions of the Lyα LF at the reionization epoch agree that the amplitude of the LF decreases as xHI increases (McQuinn et al. 2007; Haiman & Cen 2005; Le Delliou et al. 2005; Dijkstra et al. 2007b; Mesinger & Furlanetto 2007; Kobayashi et al. 2007; Iliev et al. 2008; Dayal et al. 2009).”
Comparison of reionization models: radiative transfer simulations and approximate, seminumeric models (2010, methodology): “…other hand, reionization simulations must also be large enough to statistically sample the distribution of HII regions, which can span tens of comoving megaparsecs in size towards the end of reionization (Furlanetto & Oh 2005; Zahn et al. 2005, 2007; Mesinger & Furlanetto 2007; Shin et al. 2008).”
WHAT NEXT-GENERATION 21 cm POWER SPECTRUM MEASUREMENTS CAN TEACH US ABOUT THE EPOCH OF REIONIZATION (2013, neutral): “01 (Mesinger & Furlanetto 2007; Mesinger et al. 2011).”
Fluctuations in the high-redshift Lyman–Werner background: close halo pairs as the origin of supermassive black holes (2008, methodology): “Here, the solid (dashed) curve shows the non-linear (linear) bias approximation, while the histogram shows the two–point correlation function derived from a ’semi-numerical’ simulation (Mesinger & Furlanetto 2007).”
Can the intergalactic medium cause a rapid drop in Lyα emission at z > 6? (2014, methodology): “The 5 http://homepage.sns.it/mesinger/Sim semi-numerical approach combines excursion set and perturbation formalisms to generate various cosmic fields, and has been extensively tested against numerical simulations (Mesinger & Furlanetto 2007; Mesinger et al. 2011; Zahn et al. 2011).”
Inhomogeneous recombinations during cosmic reionization (2014, methodology): “7 we show the size distributions of the HII regions, calculated according to the procedure in Mesinger & Furlanetto (2007): randomly choosing an ionized cell and tabulating the distance to the HII region edge along a randomly chosen direction.”