Simulating cosmic reionization at large scales – II. The 21-cm emission features and statistical signals

By G. Mellema, Ilian Iliev, Ue-Li Pen, P. R. S. Astron, S. Leiden, Cita, D. Astronomy, U. Austin. 2006

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We present detailed predictions for the redshifted 21-cm signal from the epoch of reionization. These predictions are obtained from radiative transfer calculations on the results of large-scale (100 h -1 Mpc), high dynamic range, cosmological simulations. We consider several scenarios for the reionization history, of both early and extended reionizations. From the simulations, we construct and analyse a range of observational characteristics, from the global signal, via detailed images and spectra, to statistical representations of rms fluctuations, angular power spectra, and probability distribution functions to characterize the non-Gaussianity of the 21-cm signal. We find that the different reionization scenarios produce quite similar observational signatures, mostly differing in the redshifts of 50 per cent reionization, and of final overlap. All scenarios show a gradual transition in the global signatures of mean signal and rms fluctuations, which would make these more difficult to observe. Individual features, such as deep gaps and bright peaks, are substantially different from the mean, and mapping these with several arcminutes and 100 s of kHz resolution would provide a direct measurement of the underlying density field and the geometry of the cosmological H II regions, although significantly modified by peculiar velocity distortions. The presence of late emission peaks suggests these to be a useful target for observations. The power spectra during reionization are strongly boosted compared to the underlying density fluctuations. The strongest statistical signal is found around the time of 50 per cent reionization and displays a clear maximum at an angular scale of l ∼ 3000-5000. We find the distribution function of emission features to be strongly non-Gaussian, with an order of magnitude higher probability of bright emission features. These results suggest that, observationally, it may be easier to find individual bright features than deriving the power spectra, which, in turn, is easier than observing individual images.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

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Citations in the corpus

The Evolution of the Intergalactic Medium (2015, background): “Figure 11 shows a light cone image of a large-box reionization simulation, from Mellema et al. (2006).”
Simulations and Analytic Calculations of Bubble Growth during Hydrogen Reionization (2006, background): “…(see e.g. Gnedin 2000; Razoumov et al. 2002; Ciardi et al. 2003; Sokasian et al. 2002; Sokasian et al. 2001; Furlanetto et al. 2004b,a; Kohler et al. 2005; Iliev et al. 2005; Mellema et al. 2006) is, however, required to constrain the topology of reionization from current and future observations.”
Reionization and Cosmology with 21-cm Fluctuations (2009, background): “An important outcome from the large cosmological volumes attained by modern numerical simulations has been the prediction of 21 cm signals that will be observable using forthcoming low frequency arrays (e.g. Mellema et al. 2006, Lidz et al. 2008).”
Shock waves in Eulerian cosmological simulations: main properties and acceleration of cosmic rays (2008, background): “Therefore, a study of cosmological shock waves must deal with the influence of a re-ionizing background (Haiman & Holder 2003; Loeb & Barkana 2001; Mellema et al. 2006).”
Foregrounds for observations of the cosmological 21 cm line - I. First Westerbork measurements of Galactic emission at 150 MHz in a low latitude field (2009, background): “Simulations indicate that the cosmological signal is expected to vary with redshift (Ciardi & Madau 2003; Mellema et al. 2006; Thomas et al. 2008).”
Self-regulated reionization (2006, methodology): “Attempts to simulate reionization in a CDM universe this way include Ciardi et al. (2000); Nakamoto et al. (2001); Razoumovet al. (2002); Ciardi et al. (2003b); Sokasian et al. (2003); Ilievet al. (2006b); Mellema et al. (2006b).”
Early Cosmological H II/He III Regions and Their Impact on Second-Generation Star Formation (2006, background): “…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 on the nature of the first sources of light (Madau et al. 1997; Zaldarriaga et al. 2004; Furlanetto et al. 2004b; Mellema et al. 2006).”
Science with the Murchison Widefield Array (2012, background): “…measuring the one-point probability distribution function (PDF) of the 21 cm brightness temperature distribution as a function of smoothing scale (Mellema et al. 2006; Ichikawa et al. 2010; Petrovic & Oh 2011) or its higher moments (Wyithe & Morales 2007), the threepoint correlation function…”
The morphology of H ii regions during reionization (2006, methodology): “…al. emission within the next few years.1 The 21-cm signal will be an excellent probe of the structure of reionization (Furlanetto, Zaldarriaga & Hernquist 2004b; Zaldarriaga, Furlanetto & Hernquist 2004; Furlanetto, Zaldarriaga & Hernquist 2004c; Furlanetto, Oh & Briggs 2006b; Mellema et al. 2006).”
Inside-out or outside-in: the topology of reionization in the photon-starved regime suggested by Lyα forest data (2008, methodology): “These studies range from radiative transfer simulation generally performed by post-processing the density field of DM simulations (Ciardi, Ferrara, & White 2003; Iliev et al. 2006b; Mellema et al. 2006; Iliev et al. 2007; McQuinn et al. 2006; McQuinn etal.”
Reionization and the Cosmic Dawn with the Square Kilometre Array (2012, background): “These are typically numerically expensive and so restricted to either relatively small volumes or small parts of parameter space, but are capable of high resolution giving insights into small scale structures (Mellema et al. 2006; Baek et al. 2010).”
21 cm cosmology in the 21st century (2011, background): “Such calculations [102, 132, 136, 137] are of great utility in describing the large scale properties of the 21 cm signal.”