Lyα Emitting Galaxies as a Probe of Reionisation

By M. Dijkstra. Publications Astronomical Society of Australia, 2014

220 citations recorded by the source corpus.

Abstract The Epoch of Reionization (EoR) represents a milestone in the evolution of our Universe. Star-forming galaxies that existed during the EoR likely emitted a significant fraction ( ~ 5 − 40%) of their bolometric luminosity as Lyα line emission. However, neutral intergalactic gas that existed during the EoR was opaque to Lyα emission that escaped from galaxies during this epoch, which makes it difficult to observe. The neutral intergalactic medium (IGM) may thus reveal itself by suppressing the Lyα flux from background galaxies. Interestingly, a ‘sudden’ reduction in the observed Lyα flux has now been observed in galaxies at z > 6. This review contains a detailed summary of Lyα radiative processes: I describe (i) the main Lyα emission processes, including collisional-excitation & recombination (and derive the origin of the famous factor ‘0.68’), and (ii) basic radiative transfer concepts, including e.g. partially coherent scattering, frequency diffusion, resonant versus wing scattering, optically thick versus ‘extremely’ optically thick (static/outflowing/collapsing) media, and multiphase media. Following this review, I derive expressions for the Gunn-Peterson optical depth of the IGM during (inhomogeneous) reionisation and post-reionisation. I then describe why current observations appear to require a very rapid evolution of volume-averaged neutral fraction of hydrogen in the context of realistic inhomogeneous reionisation models, and discuss uncertainties in this interpretation. Finally, I describe how existing & futures surveys and instruments can help reduce these uncertainties, and allow us to fully exploit Lyα emitting galaxies as a probe of the EoR.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/ff1dfc70699df25e68f22dbee4cb58b2b82013fb

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. P. Hopkins
2. R. Dav'e
3. L. Hernquist
4. C. Conroy
5. P. V. van Dokkum
6. R. Somerville
7. T. Naab
8. Richard S. Ellis

In Instrumentation

1. P. V. van Dokkum
2. C. Conroy
3. P. Hopkins
4. R. Dav'e
5. Richard S. Ellis
6. M. Franx
7. M. Trenti
8. S. Khochfar

Citations in the corpus

• THE GRISM LENS-AMPLIFIED SURVEY FROM SPACE (GLASS). I. SURVEY OVERVIEW AND FIRST DATA RELEASE (2015, background): “In addition, uncertainties exist on the theoretical side which include how Lyα photons escape from galaxies, how this depends on galaxy properties, the role of galactic winds, and how much Lya is reprocessed by the CGM (giving rise to “blobs/halos” see, e.g., Dijkstra 2014, for a review).”
• Extended Lyman α haloes around individual high-redshift galaxies revealed by MUSE (2015, background): “Under the idealised conditions of “case B” recombination (a medium optically thick to all Lyman series photons; Baker & Menzel 1938), the intrinsic production rates should have a nearly constant ratio of NLyα = 0.68NLyC (for a derivation of this factor and its validity range see Dijkstra 2014).”
• Conditions for Reionizing the Universe with a Low Galaxy Ionizing Photon Escape Fraction (2019, background): “It can be an excellent tracer of a neutral IGM, as neutral H I gas resonantly scatters Lyα photons, attenuating their observable surface brightness (e.g., Miralda-Escudé and Rees 1998; Malhotra & Rhoads 2004; Santos 2004; Verhamme et al. 2006; McQuinn et al. 2007; Dijkstra 2014).”
• The Universe Is Reionizing at z ∼ 7: Bayesian Inference of the IGM Neutral Fraction Using Lyα Emission from Galaxies (2017, background): “Into the EoR, a powerful probe of the IGM is the Lyman alpha (Lyα, 1216Å) emission line from galaxies, which is strongly attenuated by neutral hydrogen (Haiman & Spaans 1999; Malhotra & Rhoads 2004; Santos 2004; Verhamme et al. 2006; McQuinn et al. 2007a; Dijkstra 2014).”
• Planck intermediate results. XLVI. Reduction of large-scale systematic effects in HFI polarization maps and estimation of the reionization optical depth (2016, unknown): “…of full reionization provided by Lyman-α absorption in the spec- ∗Corresponding author: J. L. Puget, jean-loup.puget@ias.u-psud.fr tra of high redshift objects (see Dijkstra 2014; Mashian et al. 2016; Robertson et al. 2015; Bouwens et al. 2015; Zitrin et al. 2015, for recent results and reviews).”
• Lyman-α spectral properties of five newly discovered Lyman continuum emitters (2016, background): “This cosmic feedback of the first astrophysical objects is thought to have influenced the formation and evolution of galaxies in their first stages (Ocvirk et al. 2015) and determines their detectability (Stark et al. 2011; Schenker et al. 2014; Dijkstra 2014, 2016).”
• 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).”
• 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).”
• Inferences on the timeline of reionization at z ∼ 8 from the KMOS Lens-Amplified Spectroscopic Survey (2019, background): “This rapid decline of detected Lyα emission is most plausibly due to absorption in an increasingly neutral IGM (Dijkstra et al. 2011; Dijkstra 2014; Mesinger et al. 2015).”