The Detectability of High-Redshift Lyα Emission Lines prior to the Reionization of the Universe

By Zoltán Haiman. 2002

133 citations recorded by the source corpus.

For a source of Lyα radiation embedded in a neutral intergalactic medium (IGM) prior to the reionization epoch, the Lyα emission line is strongly suppressed by the intervening IGM. The damping wing of the so-called Gunn-Peterson trough can extend to the red side of the emission line and erase a significant fraction of the total line flux. However, the transmitted fraction increases with the size of the local cosmological H II region surrounding the source, and therefore with the ionizing luminosity and age of the source. Motivated by the recent discovery of a Lyα-emitting galaxy at a redshift z = 6.56 (Hu et al.), possibly prior to the reionization of the IGM, we revisit the effects of a neutral IGM on the Lyα emission line. We show that for faint sources with little or even no ionizing continuum, a sufficiently broad (Δv ≳ 300 km s-1) emission line can still remain observable. In particular, the line detected by Hu et al. is consistent with a source embedded in a neutral IGM. We provide characterizations of the asymmetry and total transmitted flux of the Lyα line as functions of the ionizing emissivity of its source. We argue that a statistical sample of Lyα emitters extending beyond the reionization redshift can be a useful probe of reionization.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7af2896c878f27a82d7ca8ccd3f29a60aa9ce6d7

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In Astronomy and Astrophysics

1. L. Hernquist
2. M. McQuinn
3. P. Hopkins
4. S. Furlanetto
5. Richard S. Ellis
6. M. Ouchi
7. A. Mesinger
8. M. Dijkstra

In Nuclear and High Energy Physics

1. M. McQuinn
2. S. Furlanetto
3. L. Hernquist
4. A. Mesinger
5. Abraham Loeb
6. M. Zaldarriaga
7. Renyue Cen
8. S. Oh

Citations in the corpus

• Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ∼ 6 Quasars. II. A Sample of 19 Quasars (2005, background): “When recombination is not important (Madau & Rees 2000, Cen & Haiman 2000, cf. Yu & Lu 2005), Cen & Haiman (2002) show that the HII region has a radius Rs = 8.0f −1/3 HI (ṄQ/6.5 × 10 57s−1)1/3(tQ/2× 10 7yr)1/3[(1 + zQ)/7] −1proper Mpc. (23) This is the same as Eq.”
• 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): “In this equation, Haiman (2002) considers an ionizing source at a given redshift z∗ with a constant SFR and a Salpeter IMF (the 0.1− 120M⊙ mass range), assuming that the source produces ionizing photons during the lifetime (t∗).”
• ON THE REDSHIFT EVOLUTION OF THE Lyα ESCAPE FRACTION AND THE DUST CONTENT OF GALAXIES (2010, background): “However, what this means for the neutral gas fraction is much harder to infer since the fraction of photons that scatters in the IGM depends on the exact wavelength with which Lyα is emitted (Haiman 2002; Santos 2004; Malhotra & Rhoads 2004; Verhamme et al. 2008; Dijkstra & Wyithe 2010).”
• The First Cosmic Structures and Their Effects (2004, background): “Haiman (2002) has revisited this problem for a fainter source, showing that even for a galaxy as the one discovered by Hu et al. (2002) a significant fraction of the emission line can remain observable.”
• Lyα Emitting Galaxies as a Probe of Reionisation (2014, background): “Of course, photons in the red peak start with a redshift as well, which boosts their visibility especially for large NHI (see Figure 2 in Dijkstra & Wyithe 2010, also see Haiman 2002).”
• The SUBARU Deep Field Project: Lymanα Emitters at a Redshift of 6.6 (2004, background): “(9) It should be mentioned that the SFRs estimated above are lower limits because it is quite likely that a blue half or more of the Lyα emission may be absorbed by dust grains in the galaxy, itself, and by the intergalactic H i gas (e.g., Hu et al. 2002; Haiman 2002).”
• Lyα Emitters at z = 5.7 in the Subaru Deep Field (2006, unknown): “They can be used to infer the reionization epoch of the universe via the change in their number density (Haiman & Spaans 1999; Rhoads & Malhotra 2001; Haiman 2002; Malhotra & Rhoads 2004; Stern et al. 2005; Kashikawa et al. 2005).”
• Probing the Ionization State of the Universe at z > 6 (2003, background): “These objects are interesting and relevant as direct probes of star and galaxy formation at z > 6, and the mere detectability of their Lyα emission is an important clue to the ionization state of the IGM (Haiman 2002).”
• The End of the Reionization Epoch Probed by Lyα Emitters at z = 6.5 in the Subaru Deep Field (2006, background): “We further assumed the radius of the H ii region to be 0.45 proper Mpc (Haiman 2002; Santos 2004).”
• The transition from Population III to normal galaxies: Lyα and He II emission and the ionising properties of high redshift starburst galaxies (2002, background): “Furthermore for Lyα source at redshifts close to or above the redshift of reionisation the intrinsic Lyα emission may be further reduced or suppressed by absorption in nearby line of sight HI clouds (cf. Miralda-Escude & Rees 1997, but also Haiman 2002, Madau 2002).”
• The Growth of H II Regions During Reionization (2004, background): “If the galaxy is embedded in a mostly neutral medium, Lyα absorption from the IGM can have a substantial effect on the line profile (Haiman 2002; Santos 2003; Loeb et al. 2004).”
• Unusually Large Fluctuations in the Statistics of Galaxy Formation at High Redshift (2003, background): “Reionization can the be detected statistically through the sudden jump in the number of faint sources (Haiman & Spaans 1999; Haiman 2002).”
• Observational Constraints on Cosmic Reionization (2006, background): “Haiman (2002), Santos (2004), Cen et al. (2005) showed that the local HII regions around Lyα galaxies reduce the attenuations of Lyα flux.”
• The impact of The IGM on high-redshift Lyα emission lines (2007, background): “…difference between this paper and previous work is our focus on the reionised IGM: although it is generally understood that a neutral IGM can strongly suppress Lyα emission from galaxies (Gunn & Peterson 1965; Haiman 2002; Santos 2004), the impact of an ionised IGM has been virtually ignored.”
• Studying reionization with Lyα emitters (2007, background): “…Lyα line from a galaxy is decreased if the neighborhood of an emitter is largely neutral, and this modulation can be used to probe the epoch of reionization (Miralda-Escude 1998; Madau & Rees 2000; Haiman 2002; Santos 2004; Furlanetto et al. 2004c; Furlanetto et al. 2006; Malhotra & Rhoads 2006a).”
• Lyman-α spectral properties of five newly discovered Lyman continuum emitters (2016, background): “The neutral fraction of the IGM increases with redshift (Madau 1995) and alters the transmission of high-redshift Lyα spectra (e.g. Haiman 2002; Santos 2004; Dijkstra 2014).”
• Big Three Dragons: A z = 7.15 Lyman-break galaxy detected in [O iii] 88 μm, [C ii] 158 μm, and dust continuum with ALMA (2018, background): “When Lyα photons enter the IGM, its spectral profile is further altered due to the damping wing of Lyα absorption by the intergalactic neutral hydrogen, increasing zLyα (Haiman 2002; Laursen et al. 2013).”
• Luminosity Functions of Lyα Emitters at Redshifts z = 6.5 and z = 5.7: Evidence against Reionization at z ≤ 6.5 (2004, background): “For many plausible models (Santos 2004; Haiman 2002), the reduction would be considerably larger, especially for low-luminosity sources that cannot carve a significant ionized bubble in the surrounding IGM.”