Probing reionization with Lyman α emission lines

By Michael R. Santos. 2003

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Lyman a emission from high-redshift galaxies may be a powerful probe of the ionization history of the intergalactic medium (IGM) at z > 6; the observed Lyman a emission line is sensitive to the IGM hydrogen neutral fraction over the range 0.1-1. We present calculations of observed Lyman a emission lines from z > 6 galaxies, illustrating the effect of varying the many free parameters associated with the emitting galaxy, its halo and the IGM around the galaxy. In particular, we use a dynamic model of the IGM that includes the effect of IGM infall toward the emitting galaxy. Galactic winds may play a crucial role in determining observed Lyman a line fluxes. We compare our model predictions with observations of two z = 6.5 galaxies and conclude that, if galactic winds are allowed for, existing observations place no constraint on the neutral fraction of the IGM at z = 6.5. Future infrared observations will constrain the importance of galactic winds; if winds are unimportant for the observed z = 6.5 galaxies, our models suggest that the IGM neutral fraction at z = 6.5 is ≤0.1.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/6a87338decaa0c77ae4ef29c7fb3270603318b80

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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): “However, due to uncertainties in the clustering of Lyα galaxies and the clumpiness of the IGM, a relatively high neutral fraction cannot yet be ruled out by the Lyα emitter observations (Santos 2004, Haiman & Cen 2005, Wyithe et al. 2005, Furlanetto et al. 2006).”
Identification of the brightest Lyα emitters at z = 6.6 : Implications for the evolution of the luminosity function in the reionization era (2015, background): “…in absorption systems, although again, there is no definite explanation why there should be a sudden increase. iv) the most quoted reason (e.g. Santos 2004; Haiman & Cen 2005; McQuinn et al. 2007; Choudhury et al. 2014; Jensen et al. 2014) is that the observed decrease in both the evolution…”
Lyman α radiative transfer in a multiphase medium (2005, background): “…environs of the host galaxy, Lyα photons undergo processing in the surrounding intergalactic medium (IGM), and the presence or ab- E-mail: peng@physics.ucsb.edu sence of observed Lyα emission can be used to place constraints on the epoch of reionization (Fan et al. 2002; Haiman 2002; Santos 2004).”
REIONIZATION AFTER PLANCK: THE DERIVED GROWTH OF THE COSMIC IONIZING EMISSIVITY NOW MATCHES THE GROWTH OF THE GALAXY UV LUMINOSITY DENSITY (2015, methodology): “…to an increasingly neutral IGM at z ∼ 7–8, one can use this technique to quantify the filling factor of ionized hydrogen at z ∼ 6.5–8 (Malhotra & Rhoads 2004; Santos 2004; McQuinn et al. 2007; Mesinger & Furlanetto 2008; Fontana et al. 2010; Stark et al. 2010, 2011; Dijkstra et al. 2011;…”
Lyα Radiation from Collapsing Protogalaxies. I. Characteristics of the Emergent Spectrum (2005, background): “The result of this is that the IGM may erase a fraction of the red part of the Ly line (Barkana & Loeb 2004; Santos 2004).”
The Evolution of the Intergalactic Medium (2015, background): “…as the photons scatter out of the host galaxy or “absorbed” by flows onto the host, effects that influence the amount of scattering from a neutral IGM (Santos 2004; Dijkstra, Lidz & Wyithe 2007).23 22For gamma ray bursts (GRBs), it is difficult to separate IGM absorption from absorption from H i…”
LINE-EMITTING GALAXIES BEYOND A REDSHIFT OF 7: AN IMPROVED METHOD FOR ESTIMATING THE EVOLVING NEUTRALITY OF THE INTERGALACTIC MEDIUM (2014, methodology): “First proposed as a practical experiment using Lyman break galaxies (LBGs) by Stark et al. (2010), the idea followed earlier theoretical work by Miralda-Escudé et al. (2000), Santos (2004) and others.”
Lyα Emitting Galaxies as a Probe of Reionisation (2014, background): “…dense gas (and/or retarded Hubble flows) around dark matter halos hosting Lyα emitting galaxies can give rise to an increased opacity of the IGM around the Lyα resonance, and even extending somewhat into the red side of the Lyα line (Santos 2004; Dijkstra, Lidz, & Wyithe 2007; Laursen 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): “Based on Figure 25 of Santos (2004), our Lyα transmission fraction result is consistent with xHI ∼ 0.0− 0.2 considering the two cases.”
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.”
Mapping Neutral Hydrogen during Reionization with the Lyα Emission from Quasar Ionization Fronts (2007, unknown): “…from the luminosity-function evolution of Ly -emitting galaxies (LAEs) at z > 6 (Miralda-Escudé & Rees 1998; Madau & Rees 2000; Haiman 2002; Santos 2004; Taniguchi et al. 2005; Furlanetto et al. 2006; Malhotra & Rhoads 2006; Kashikawa et al. 2006), and from their clustering properties…”
The End of the Reionization Epoch Probed by Lyα Emitters at z = 6.5 in the Subaru Deep Field (2006, methodology): “We further assumed the radius of the H ii region to be 0.45 proper Mpc (Haiman 2002; Santos 2004).”
Lyα COOLING EMISSION FROM GALAXY FORMATION (2010, background): “…and systematic infall around massive halos (e.g., Faucher-Giguère et al. 2008c) can amplify and shift the absorption, whereas galactic winds act to “let through” more radiation by redshifting it away from the Lyα line center (e.g., Santos 2004; Dijkstra et al. 2007; Dijkstra & Wyithe 2010).”
The morphology of H ii regions during reionization (2006, background): “If there are pockets of neutral gas at these redshifts, the statistics of these emitters can be dramatically altered (Madau & Rees 2000; Haiman 2002; Santos 2004; Furlanetto et al. 2006a; Malhotra & Rhoads 2006).”
Studying reionization with Lyα emitters (2007, background): “Galactic winds can collisionally ionize the hydrogen within up to ∼ 0.2 pMpc of a galaxy, eliminating the importance of nearby infall (Santos 2004).”
The observed ionization rate of the intergalactic medium and the ionizing emissivity at z≥ 5: evidence for a photon-starved and extended epoch of reionization (2007, background): “…beyond the putative tail end of the hydrogen reionization epoch at z 6, determining the ionization state of the IGM is still problematic (e.g. Fan et al. 2002; Santos 2004; Songaila 2004; Gallerani, Choudhury & Ferrara 2006; Fan et al. 2006; Bolton & Haehnelt 2007; Dijkstra, Wyithe & Haiman 2007).”
NEW CONSTRAINTS ON COSMIC REIONIZATION FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN (2013, background): “…reionization, resonant absorption near the source galaxies, and absorption from dense IGM structures) and inside galaxies (dust absorption, emission geometry, and winds) all affect the detailed interpretation of the raw measurements (e.g., Santos 2004; Dijkstra et al. 2011; Bolton & Haehnelt 2012).”
Reionization and Galaxy Evolution Probed by z = 7 Lyα Emitters (2007, methodology): “Application of Santos (2004) model yields the neutral fractions of xz=6.6HI ∼ 0.12–0.42 and x z=7 HI ∼ 0.12–0.54.”