Taxing the rich: Recombinations and bubble growth during reionization

By S. Furlanetto, S. Oh. 2005

182 citations recorded by the source corpus.

Reionization is inhomogeneous for two reasons: the clumpiness of the intergalactic medium (IGM), and clustering of the discrete ionizing sources. While numerical simulations can in principle take both into account, they are at present limited by small box sizes. On the other hand, analytic models have only examined the limiting cases of a clumpy IGM (with uniform ionizing emissivity) and clustered sources (embedded in a uniform IGM). Here, we present the first analytic model that includes both factors. At first, recombinations can be ignored and ionized bubbles grow primarily through major mergers, because at any given moment the bubbles have a well-defined characteristic size. As a result, reionization resembles ‘punctuated equilibrium,’ with a series of well-separated sharp jumps in the ionizing background. These features are local effects and do not reflect similar jumps in the global ionized fraction. We then combine our bubble model with a simple description of recombinations in the IGM. We show that the bubbles grow until recombinations balance ionizations, when their expansion abruptly halts. If the IGM density structure is similar to that at moderate redshifts, this limits the bubble radii to ∼20 comoving Mpc; however, if the IGM is significantly clumpier at higher redshifts (because of minihalo formation, for example), the limit could be much smaller. Once a bubble reaches saturation, that region of the Universe has for all intents and purposes entered the ‘post-overlap’ stage. Because different H ii regions saturate over a finite time interval, the overlap epoch actually has a finite width. Our model also predicts a mean recombination rate several times larger than expected for a uniformly illuminated IGM. This picture naturally explains the substantial large-scale variation in Lyman-series opacity along the lines of sight to the known z > 6 quasars. More quasar spectra will shed light on the transition between the ‘bubble-dominated’ topology characteristic of reionization and the ‘web-dominated’ topology characteristic of the later Universe.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/ef795c40fcf09e840c8ceb0f5300050b79661bd1

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Citations in the corpus

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).”
The impact of The IGM on high-redshift Lyα emission lines (2007, background): “At overlap a ‘jump’ in the ionising background may occur (Gnedin 2000, although see Furlanetto & Oh, 2005).”
Simulations and Analytic Calculations of Bubble Growth during Hydrogen Reionization (2006, background): “A large dynamic range is required to resolve the small mass galaxies which may make up the sources and sinks of ionizing photons, while simultaneously sampling the distribution of HII regions, which may be as large as R ∼ 20 comoving Mpc h−1 towards the end of reionization (Furlanetto & Oh 2005).”
ON LYMAN-LIMIT SYSTEMS AND THE EVOLUTION OF THE INTERGALACTIC IONIZING BACKGROUND (2011, background): “Intuition is gained by approximating P (∆) as a power law with index−γ over the densities that contribute most of the recombinations (Furlanetto & Oh 2005).”
Keeping the Universe ionized: photoheating and the clumping factor of the high-redshift intergalactic medium (2008, background): “For example, Furlanetto & Oh (2005) point out that if the large-scale dense regions are ionised first, the clumping factor may be somewhat larger than one would otherwise expect, because the photons are initially confined to these dense regions.”
Comparison of reionization models: radiative transfer simulations and approximate, seminumeric models (2010, background): “…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).”
Efficient Simulations of Early Structure Formation and Reionization (2007, background): “Ionized regions are expected to reach characteristic sizes of tens of comoving Mpc (Furlanetto et al. 2004c; Furlanetto & Oh 2005), which is over seven orders of magnitude in mass larger than the pertinent cooling mass, corresponding to gas with a temperature of T ∼ 104 K (e.g. Efstathiou 1992;…”
The Giant Gemini GMOS survey of zem > 4.4 quasars – I. Measuring the mean free path across cosmic time (2014, methodology): “For isothermal density profiles, the Miralda-Escudé et al. (2000) model yields H I ∝ [ λ912mfp ]1.5 (Furlanetto & Oh 2005) which approximately holds in the numerical treatment by McQuinn et al. (2011).”
SILVERRUSH. IV. Lyα luminosity functions at z = 5.7 and 6.6 studied with ∼1300 Lyα emitters on the 14–21 deg2 sky (2017, methodology): “By using the analytic models of Furlanetto et al. (2006) (See also Furlanetto & Oh 2005), we quantify the typical size of ionized bubbles around LAEs at z = 6.6.”
The Evolution of the Intergalactic Medium (2015, methodology): “…source limit, the impact of dense systems/recombinations should be reduced, potentially skewing the predictions for the structure of reionization (Furlanetto & Oh 2005; Ciardi et al. 2012; Choudhury, Haehnelt 16The detail at which the sources are followed range from prescriptions based simply on…”
21 cm cosmology in the 21st century (2011, background): “To set the critical density ∆c, we account for the patchy nature of reionization, which proceeds via the expansion and overlap of ionized bubbles [49].”
NEW CONSTRAINTS ON COSMIC REIONIZATION FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN (2013, background): “These high-density clumps recombine much faster than average, soCHII may increase throughout reionization (Furlanetto & Oh 2005).”
Cosmological Parameter Estimation Using 21 cm Radiation from the Epoch of Reionization (2005, background): “Furlanetto & Oh (2005) show that recombinations within halos affect the bubble size distribution in the FZH04 model only at x̄i k 0:7, increasing in importance as x̄i !”
COSMIC MICROWAVE BACKGROUND CONSTRAINTS ON THE DURATION AND TIMING OF REIONIZATION FROM THE SOUTH POLE TELESCOPE (2011, background): “Furthermore, recombinations in dense systems might effectively stall bubble growth early on in reionization, leading to a slowly percolating web of similarly sized ionized regions (Furlanetto & Oh 2005).”
Rapid Reionization by the Oligarchs: The Case for Massive, UV-bright, Star-forming Galaxies with High Escape Fractions (2019, background): “…Case B recombination may not be an appropriate description toward the end of reionization when local absorption in dense clumps becomes important (Furlanetto & Oh 2005), or CH II is bound to evolve as the universe grows more ionized (Pawlik et al. 2015), though its effect on reionization…”
The global 21-centimeter background from high redshifts (2006, methodology): “We can compute the collapse fraction (or more precisely f coll) required to 6Unlike Miralda-Escudé et al. (2000), we do not treat C and x̄i as independent variables; we simply set C as a function of x̄i using the methods described in Furlanetto & Oh (2005). achieve xα = 1 from equation (18).”
New Measurements of the Ionizing Ultraviolet Background over 2 < z < 5 and Implications for Hydrogen Reionization (2013, methodology): “As pointed out by Miralda-Escudé et al. (2000) and Furlanetto & Oh (2005), once the IGM is essentially fully ionized, the evolution in Γ is driven by the photo-evaporation of optically thick Lymanlimit systems, which largely regulate the mean free path.”
Simulating Cosmic Reionization at Large Scales I: the Geometry of Reionization (2005, background): “…other hand, these ionizing sources were strongly clustered at high redshift and, as a consequence, the H II regions they created are expected to quickly overlap and grow to very large sizes,reaching up to tens of Mpc (e.g. Barkana & Loeb 2004; Furlanetto & Oh 2005; Cen 2005; Iliev et al. 2005c).”