ON THE REDSHIFT EVOLUTION OF THE Lyα ESCAPE FRACTION AND THE DUST CONTENT OF GALAXIES

By M. Hayes, Daniel Schaerer, G. Östlin, J. Mas-Hesse, H. Atek, D. Kunth. 2010

195 citations recorded by the source corpus.

The Lyα emission line has been proven to be a powerful tool for studying evolving galaxies at the highest redshift. However, in order to use Lyα as a physical probe of galaxies, it becomes vital to know the Lyα escape fraction (fLyαesc). Unfortunately, due to the resonant nature of Lyα, fLyαesc may vary unpredictably and requires empirical measurement. Here, we compile Lyα luminosity functions (LFs) between redshifts z = 0 and 8 and, combined with Hα and ultraviolet data, assess how fLyαesc evolves with redshift. We find a strong upward evolution in fLyαesc over the range z = 0.3–6, which is well fit by the power law fLyαesc∝(1 + z)ξwith ξ = (2.57+0.19−0.12). This predicts that fLyαesc should reach unity at z = 11.1. By comparing fLyαesc and EB−V in individual galaxies we derive an empirical relationship between fLyαesc and EB−V, which includes resonance scattering and can explain the redshift evolution of fLyαesc between z = 0 and 6 purely as a function of the evolution in the dust content of galaxies. Beyond z ≈ 6.5, fLyαesc drops more substantially, an effect attributed to either ionizing photon leakage, or an increase in the neutral gas fraction of the intergalactic medium. While distinguishing between these two scenarios may be extremely challenging, by framing the problem this way we remove the uncertainty of the halo mass from Lyα-based tests of reionization. We finally derive a new method by which to estimate the dust content of galaxies, based purely upon the observed Lyα and UV LFs. These data are characterized by an exponential with an e-folding scale of zEBV ≈ 3.4.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/a31e9f85080d631f01b828a26d71ec97be574a9e

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Citations in the corpus

SILVERRUSH. IV. Lyα luminosity functions at z = 5.7 and 6.6 studied with ∼1300 Lyα emitters on the 14–21 deg2 sky (2017, background): “…is defined by the ratio of the star formation rate densities (SFRDs) estimated from observed Lyα luminosity densities (LDs) to those estimated from intrinsic UV LDs, largely increases from z ∼ 0 to z ∼ 6 by two orders of magnitudes, and turns to the decrease beyond z & 6 (e.g., Hayes et al. 2011).”
Star Formation in the Milky Way and Nearby Galaxies (2012, background): “Several ongoing studies are quantifying this parameter by comparing Lyα fluxes of galaxies with independent SFR tracers such as Hα or the UV continuum (e.g., Atek et al. 2009; Scarlata et al. 2009; Blanc et al. 2011; Hayes et al. 2011).”
THE SPECTRAL EVOLUTION OF THE FIRST GALAXIES. I. JAMES WEBB SPACE TELESCOPE DETECTION LIMITS AND COLOR CRITERIA FOR POPULATION III GALAXIES (2011, background): “…100 h )1/2 ] +mAB, 100h. (5) To avoid predictions hinging on the highly uncertain luminosity of the Lyα emission line at high redshifts (e.g. Fontana et al. 2010; Hayes et al. 2011), we assume the Lyα escape fraction to be zero – i.e. the Lyα line does not contribute to the predicted fluxes at all.”
REIONIZATION AFTER PLANCK: THE DERIVED GROWTH OF THE COSMIC IONIZING EMISSIVITY NOW MATCHES THE GROWTH OF THE GALAXY UV LUMINOSITY DENSITY (2015, background): “This is particularly the case, since z > 6 galaxies may be more efficient at releasing ionizing radiation into the IGM due to evolution in fesc or ξion (both of which have been speculated to increase at z > 6: Siana et al. 2010; Hayes et al. 2011, HM12, KF12, Duncan & Conselice 2015).”
Lyα Emitting Galaxies as a Probe of Reionisation (2014, background): “These analyses have revealed that f αesc is anti-correlated with the dust-content18 of galaxies (Atek et al. 2009; Kornei et al. 2010; Hayes et al. 2011).”
The Universe Is Reionizing at z ∼ 7: Bayesian Inference of the IGM Neutral Fraction Using Lyα Emission from Galaxies (2017, background): “This is likely a simplification, as trends at lower redshifts show increasing EW with redshift as dust decreases in galaxies (Hayes et al. 2011), but the time between z ∼ 6 and z ∼ 7 is short (< 200 Myr).”
CIGALE: a python Code Investigating GALaxy Emission (2018, background): “Even though the escape fraction is generally low in the nearby universe, it may reach much higher values at high redshift to reionise the universe (e.g. Inoue et al. 2006; Hayes et al. 2011).”
THE EVOLUTION OF THE GALAXY REST-FRAME ULTRAVIOLET LUMINOSITY FUNCTION OVER THE FIRST TWO BILLION YEARS (2014, background): “After reducing the amount of Lyα flux to 25% of the intrinsic value, our photometric redshifts matched the input redshifts (which matches expectations for the global Lyα escape fraction; e.g., Blanc et al. 2011; Hayes et al. 2011).”
Escape of Lyman continuum radiation from local galaxies - Detection of leakage from the young starburst Tol 1247-232 (2013, background): “There might also be a trend toward higher fesc with a lower internal absorption, which also has been observed for the escape fraction of Lyα photons (e.g. Atek et al. 2009; Hayes et al. 2010, 2011), although the escape mechanisms can vary significantly between the two.”
Lyman-α spectral properties of five newly discovered Lyman continuum emitters (2016, background): “The same behaviour has been reported for the evolution of f Lyαesc with redshift (Hayes et al. 2011).”
Inferences on the timeline of reionization at z ∼ 8 from the KMOS Lens-Amplified Spectroscopic Survey (2019, background): “Whilst there may be evolution in the amount of Lyα escaping the ISM of galaxies with increasing redshift, it is probably increasing as dust masses and HI covering fractions may decrease at higher redshifts and facilitate Lyα escape at fixed galaxy mass (Hayes et al. 2011; Oyarzún et al. 2016).”
The MUSE Hubble Ultra Deep Field Survey - VIII. Extended Lyman-α haloes around high-z star-forming galaxies (2017, background): “This difference could be due to an evolution of the Lyα escape fraction with redshift, possibly due to dust content evolution (Hayes et al. 2011; Dijkstra & Jeeson-Daniel 2013) or because of sensitivity limitations.”
Identification of the brightest Lyα emitters at z = 6.6 : Implications for the evolution of the luminosity function in the reionization era (2015, background): “Using a joint analysis of the evolution of the Lyα and LBG luminosity functions, Hayes et al. (2011) finds that the volumetric (statistical) Lyα escape fraction increases with redshift up to z = 6 and decreases at higher redshift, although this result is based on the integration of the Lyα LF from…”
Ionization state of inter-stellar medium in galaxies: evolution, SFR-M * -Z dependence, and ionizing photon escape (2013, background): “Because the fraction of LAEs in star-forming galaxies increases with redshift (at least up to z ∼ 6; e.g. Ouchi et al. 2008; Vanzella et al. 2009; Stark et al. 2010, 2011; Hayes et al. 2011), the average fesc for z ∼ 6 galaxies would be higher than that for z ∼ 3 galaxies.”
KECK SPECTROSCOPY OF FAINT 3 < z < 8 LYMAN BREAK GALAXIES: EVIDENCE FOR A DECLINING FRACTION OF EMISSION LINE SOURCES IN THE REDSHIFT RANGE 6 < z < 8 (2011, background): “It is important to note that our f is differs from fLyαesc , commonly defined in the literature as the total escape fraction of Lyα photons (e.g., Hayes et al. 2011). fLyαesc represents the total transmission of Lyα, accounting for both attenuation of photons within the galaxy by mechanisms such as…”