INTERGALACTIC TRANSMISSION AND ITS IMPACT ON THE Lyα LINE

Laursen, Peter; Sommer–Larsen, Jesper; Razoumov, Alexei O.

doi:10.1088/0004-637x/728/1/52

Cited by 211 publications

(360 citation statements)

References 80 publications

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“…This might be the reason for the high τ d preference of the data. However, for the observed spectra the blue side might be attenuated not by dust but by neutral gas in the CGM and / or IGM which scatters Lyα photons out of the line-of-sight, and thus, effectively absorb the blue side of the spectrum (Dijkstra et al 2007;Laursen et al 2011). …”

Section: Fitting Resultsmentioning

confidence: 99%

Modeling 237 Lyman-αspectra of the MUSE-Wide survey

Grönke

2017

A&A

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We compare 237 Lyman-α (Lyα) spectra of the "MUSE-Wide survey" ) to a suite of radiative transfer simulations consisting of a central luminous source within a concentric, moving shell of neutral gas, and dust. This six parameter shell-model has been used numerously in previous studies, however, on significantly smaller datasets. We find that the shell-model can reproduce the observed spectral shape very well -better than the also common 'Gaussian-minus-Gaussian' model which we also fitted to the dataset. Specifically, we find that ∼ 94% of the fits possess a goodness-of-fit value of p(χ 2 ) > 0.1. The large number of spectra allows us to robustly characterize the shell-model parameter range, and consequently, the spectral shapes typical for realistic spectra. We find that the vast majority of the Lyα spectral shapes require an outflow and only ∼ 5% are well-fitted through an inflowing shell. In addition, we find ∼ 46% of the spectra to be consistent with a neutral hydrogen column density < 10 17 cm −2 -suggestive of a non-negligible fraction of continuum leakers in the MUSE-Wide sample. Furthermore, we correlate the spectral against the Lyα halo properties against each other but do not find any strong correlation.

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Section: Fitting Resultsmentioning

confidence: 99%

Modeling 237 Lyman-αspectra of the MUSE-Wide survey

Grönke

2017

A&A

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“…The "true" IGM only affects the strength of Lyα red peak by the damped absorption factor of e −τ , where τ is the optical depth of the IGM HI gas along the line of sight, and its effect on the velocity of the narrow Lyα red peak is negligible. Some simulations suggested that the HI gas in the CGM can be very close to the Lyα photons in frequency, so the CGM HI gas can resonantly scatter and/or absorb Lyα photons at V(redpeak)<160 km s −1 (Laursen et al 2011;Dijkstra 2014) and change the V(red-peak) of Lyα profile. In fact those scatterings by CGM are part of the Lyα escape process before Lyα photons reach the "true" IGM.…”

Section: Predicting Lyα Escape Fractionmentioning

confidence: 99%

Lyα Profile, Dust, and Prediction of Lyα Escape Fraction in Green Pea Galaxies

Yang

Malhotra

Grönke

et al. 2017

ApJ

192

241

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We studied Lyman-α (Lyα) escape in a statistical sample of 43 Green Peas with HST/COS Lyα spectra. Green Peas are nearby star-forming galaxies with strong [OIII]λ5007 emission lines. Our sample is four times larger than the previous sample and covers a much more complete range of Green Pea properties. We found that about 2/3 of Green Peas are strong Lyα line emitters with rest-frame Lyα equivalent width > 20Å. The Lyα profiles of Green Peas are diverse. The Lyα escape fraction, defined as the ratio of observed Lyα flux to intrinsic Lyα flux, shows anti-correlations with a few Lyα kinematic features -both the blue peak and red peak velocities, the peak separations, and FWHM of the red portion of the Lyα profile. Using properties measured from SDSS optical spectra, we found many correlations -Lyα escape fraction generally increases at lower dust reddening, lower metallicity, lower stellar mass, and higher [OIII]/[OII] ratio. We fit their Lyα profiles with the HI shell radiative transfer model and found Lyα escape fraction anti-correlates with the best-fit N HI . Finally, we fit an empirical linear relation to predict f Lyα esc from the dust extinction and Lyα red peak velocity. The standard deviation of this relation is about 0.3 dex. This relation can be used to isolate the effect of IGM scatterings from Lyα escape and to probe the IGM optical depth along the line of sight of each z > 7 Lyα emission line galaxy in the JWST era.

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“…As a result, the inflow feature in our profiles may disappear and the shape may become an asymmetric single peak with only photons at the red wing. Laursen et al (2011) showed that a large fraction of Lyα flux from galaxies atz 6.5 could be lost by scattering in IGM despite most of the IGM being ionized. As a simple test, we show the line profiles without photons at shorter wavelength as (Laursen et al 2011). shown in the blue dashed lines in the figure.…”

Section: The Lyα Line Profilementioning

confidence: 99%

COLD ACCRETION IN EARLY GALAXY FORMATION AND ITS ${\rm Ly}\alpha $ SIGNATURES

Yajima

Zhu

et al. 2015

ApJ

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Lyα emission has played an important role in detecting high-redshift galaxies, including recently distant ones at redshifts > z 7. It may also contain important information concerning the origin of these galaxies. Here, we investigate the formation of a typical L * galaxy and its observational signatures at the earliest stage by combining a cosmological hydrodynamic simulation with three-dimensional radiative transfer (RT) calculations using the newly improved ART 2 code. Our cosmological simulation uses the Aquila initial condition, which zooms in on a Milky-Way-like halo with high resolutions, and our RT couples multi-wavelength continuum, Lyα line, and ionization of hydrogen. We find that the modeled galaxy starts to form at redshift z ∼ 24 through the efficient accretion of cold gas, which produces a strong Lyα line with a luminosity ofã 1 as early as z ∼ 14. The Lyα emission appears to trace the cold, dense gas. The lines exhibit asymmetric, single-peak profiles, and are shifted to the blue wing, a characteristic feature of gas inflow. Moreover, the contribution to the total Lyα luminosity from excitation cooling increases with redshift and becomes dominant at z  6. We predict that L * galaxies such as the modeled one may be detected at z  8 by the James Webb Space Telescopeand Atacama Large Millimeter Array with a reasonable integration time. Beyond redshift 12, however, the Lyα line may only be observable by spectroscopic surveys. Our results suggest that the Lyα line is one of the most powerful tools to detect the first generation of galaxies and decipher their formation mechanism.

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INTERGALACTIC TRANSMISSION AND ITS IMPACT ON THE Lyα LINE

Cited by 211 publications

References 80 publications

Modeling 237 Lyman-αspectra of the MUSE-Wide survey

Modeling 237 Lyman-αspectra of the MUSE-Wide survey

Lyα Profile, Dust, and Prediction of Lyα Escape Fraction in Green Pea Galaxies

COLD ACCRETION IN EARLY GALAXY FORMATION AND ITS ${\rm Ly}\alpha $ SIGNATURES

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