Can the intergalactic medium cause a rapid drop in Lyα emission at z > 6?

By A. Mesinger, A. Aykutalp, E. Vanzella, L. Pentericci, A. Ferrara, M. Dijkstra. 2014

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The large cross-section of the Lyman alpha (Lya) line makes it a sensitive probe of the ionization state of the intergalactic medium (IGM). Here we present the most complete study to date of the IGM Lya opacity, and its application to the redshift evolution of the 'Lya fraction', i.e. the fraction of color-selected galaxies with a detectable Lya emission line. We use a tiered approach, which combines large-scale semi-numeric simulations of reionization with moderate-scale hydrodynamic simulations of the ionized IGM. This allows us to simultaneously account for evolution in both: (i) the opacity from an incomplete (patchy) reionization, parameterized by the filling factor of ionized regions, Q_HII; and (ii) the opacity from self-shielded systems in the ionized IGM, parameterized by the average photo-ionization rate inside HII regions, \Gamma. In contrast to recent empirical models, attenuation from patchy reionization has a unimodal distribution along different sightlines, while attenuation from self-shielded systems is more bimodal. We quantify the average IGM transmission in our (Q_HII, \Gamma) parameter space, which can easily be used to interpret new data sets. Using current observations, we predict that the Lya fraction cannot drop by more than a factor of ~2 with IGM attenuation alone, even for HII filling factors as low as Q_HII>0.1. Larger changes in the Lya fraction could result from a co-evolution with galaxy properties. Marginalizing over \Gamma, we find that current observations constrain Q_HII = 6.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/260111a1ca913b8e4e0a729c44611588931fbc95

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Citations in the corpus

21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal (2015, background): “…such constraints can be obtained from the spectra of high-z quasars such as ULAS J1120+0641 (Bolton et al. 2011; Mortlock et al. 2011) or from the observed drop in Lyman-α emission from high-z galaxies (e.g. Caruana et al. 2014; Pentericci et al. 2014; Dijkstra et al. 2014; Mesinger et al. 2015).”
THE GRISM LENS-AMPLIFIED SURVEY FROM SPACE (GLASS). I. SURVEY OVERVIEW AND FIRST DATA RELEASE (2015, background): “In detail, quantitative constraints inferred from Lya emitting galaxies still suffer significantly from observational uncertainties (e.g., Mesinger et al. 2015).”
EVIDENCE FOR PopIII-LIKE STELLAR POPULATIONS IN THE MOST LUMINOUS Lyα EMITTERS AT THE EPOCH OF REIONIZATION: SPECTROSCOPIC CONFIRMATION (2015, background): “However, it is becoming clear that re-ionisation by itself is not enough to explain the rapid decline of the fraction of strong Lyα emitters towards z ∼ 7 (e.g. Dijkstra 2014; Mesinger et al. 2015).”
Stellar population effects on the inferred photon density at reionization (2015, background): “…suggested that the ⋆ E-mail: e.r.stanway@warwick.ac.uk number density of neutral hydrogen clouds rises sharply at z > 6, resulting in absorption in distant spectra, and so fewer galaxies observable in the Lyman-α transition of Hydrogen (Stark et al. 2010; Caruana et al. 2014; Mesinger et al. 2015).”
Inferences on the timeline of reionization at z ∼ 8 from the KMOS Lens-Amplified Spectroscopic Survey (2019, methodology): “Ouchi et al. (2010); McGreer et al. (2014); Sobacchi & Mesinger (2015); Mesinger et al. (2015); Davies et al. (2018); Greig et al. (2018); Mason et al. (2018a) and the Planck Collaboration et al. (2016).”
Feedback-regulated star formation and escape of LyC photons from mini-haloes during reionization (2016, background): “…et al. 2014; Schenker et al. 2014; Pentericci et al. 2014; Tilvi et al. 2014; Matthee et al. 2015) suggest that reionisation may have ended later than previously thought (e.g., Chardin et al. 2015; Choudhury et al. 2015; Davies & Furlanetto 2016, c.f., Haardt & Madau 2012; Mesinger et al. 2015).”
CONTRASTING GALAXY FORMATION FROM QUANTUM WAVE DARK MATTER, ψDM, WITH ΛCDM, USING PLANCK AND HUBBLE DATA (2015, background): “A relatively sharp reionization transition is considered likely if galaxies are the dominant source of reionization, based on advanced hybrid techniques (Mesinger et al. 2015), which justifies the instantaneous reionization redshift approximation (Dijkstra 2014; Mitra et al. 2015).”
Identification of the brightest Lyα emitters at z = 6.6 : Implications for the evolution of the luminosity function in the reionization era (2015, background): “Mesinger et al. (2015) however argue that re-ionisation can not be the only driver of the observed changing opacity to Lyα and Konno et al. (2014) mention that the neutral IGM fraction required to explain their observed evolution of the Lyα LF (see left panel of Fig.”
Rapid Reionization by the Oligarchs: The Case for Massive, UV-bright, Star-forming Galaxies with High Escape Fractions (2019, background): “While the evolution in the fraction of Lyα emitters in Lyman-break galaxies (e.g., Mesinger et al. 2015) encodes the evolution of x zH I¯ ( ), Mason et al. (2018) show that a more competitive constraint may be derived by utilizing EW distributions.”
Hydrogen Epoch of Reionization Array (HERA) (2016, background): “First stars are expected to form at z ∼ 25−30 and their imprint on the 21 cm signal is expected to be sensitive to the halo mass where they are formed (Mesinger et al. 2015).”
REIONIZATION AFTER PLANCK: THE DERIVED GROWTH OF THE COSMIC IONIZING EMISSIVITY NOW MATCHES THE GROWTH OF THE GALAXY UV LUMINOSITY DENSITY (2015, methodology): “Not only do the observational inferences depend on the intrinsic velocity offset of Lyα emission (e.g., Mesinger et al. 2015; Stark et al. 2015), but it is dependent on details of the radiative transfer, inhomogeneities in the IGM, the ionizing background, all of which rely on high-quality…”
The Evolution of the Intergalactic Medium (2015, background): “…in the neutral fraction to explain it (to xHI > 0.4 by z = 7; Mesinger et al. 2015), although there is debate over whether the dense absorption systems that many of these studies had ignored allows for less rapid evolution (Bolton & Haehnelt 2013; Choudhury et al. 2015; Mesinger et al. 2015).”
Lyα EMISSION FROM A LUMINOUS z = 8.68 GALAXY: IMPLICATIONS FOR GALAXIES AS TRACERS OF COSMIC REIONIZATION (2015, background): “The currently observed decline (e.g. Schenker et al. 2014) implies a surprisingly rapid end to the process (Choudhury et al. 2014; Mesinger et al. 2015).”
Spectroscopic detection of C iv λ1548 in a galaxy at z = 7.045: implications for the ionizing spectra of reionization-era galaxies (2015, background): “The weak Lyα emission is thought to reflect an increase in the IGM neutral hydrogen fraction over 6 < z < 8 (Mesinger et al. 2015; Choudhury et al. 2014), as would be expected if reionization is incomplete at z ' 7−8 (e.g, Robertson et al. 2013, 2015).”
Lyα and C iii] emission in z = 7–9 Galaxies: accelerated reionization around luminous star-forming systems? (2016, background): “The decline in the volume density of Lyα emitters at z > 6.5 is consistent with strong attenuation from intergalactic hydrogen, possibly requiring neutral fractions of xHI ∼> 0.3 − 0.5 at z ' 7 − 8 (Mesinger et al. 2015; Choudhury et al. 2015).”
Consistent modelling of the meta-galactic UV background and the thermal/ionization history of the intergalactic medium (2018, result): “It is also consistent with the drop in the observed abundance of Lyman-α emitting galaxies at z & 6 (e.g., Treu et al. 2013; Zheng et al. 2017), which is (at least partly) due to absorption by an increasingly neutral IGM (e.g., Choudhury et al. 2015; Mesinger et al. 2015).”
The Universe Is Reionizing at z ∼ 7: Bayesian Inference of the IGM Neutral Fraction Using Lyα Emission from Galaxies (2017, methodology): “Our constraint on the neutral fraction, xhi = 0.59 +0.11 −0.15, is consistent with other robust probes of IGM neutrality at z ∼ 7 (Mesinger et al. 2015; Greig et al. 2017) demonstrating the power of Lyα follow-up of LBGs to constrain the neutral fraction, and providing more strong evidence that the…”