Escape of Lyα and continuum photons from star-forming galaxies

Hidenobu Yajima, Yuexing Li, Qirong Zhu, Tom Abel, Caryl Gronwall, Robin Ciardullo

Research output: Contribution to journalArticle

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Abstract

A large number of high-redshift galaxies have been discovered via their narrow-band Lya line or broad-band continuum colours in recent years. The nature of the escaping process of photons from these early galaxies is crucial to understand galaxy evolution and the cosmic reionization. Here, we investigate the escape of Lya, non-ionizing UV-continuum (λ lt; 1300-1600Å in rest frame), and ionizing photons (λ <912 Å) from galaxies by combining a cosmological hydrodynamic simulation with three-dimensional multiwavelength radiative transfer calculations. The galaxies are simulated in a box of 53 h-3 Mpc3 with high resolutions using the Aquila initial condition which reproduces a MilkyWay-like galaxy at redshift z = 0.We find that the escape fraction (fesc) of these different photons shows a complex dependence on redshift and galaxy properties: fLyα esc and fUV esc appear to evolve with redshift, and they show similar, weak correlations with galaxy properties such as mass, star formation, metallicity, and dust content, while fIon esc remains roughly constant at ̃0.2 from z ̃ 0 to 10, and it does not show clear dependence on galaxy properties. fLyα esc correlates more strongly with f UV esc than with f Ion esc . In addition, we find a relation between the emergent Lya luminosity and the ionizing photon emissivity of Lyman Alpha Emitters (LAEs). By combining this relation with the observed luminosity functions of LAEs at different redshift, we estimate the contribution from LAEs to the reionization of intergalactic medium (IGM). Our result suggests that ionizing photons from LAEs alone are not sufficient to ionize IGM at z ≥ 6, but they can maintain the ionization of IGM at z ̃ 0-5.

Original languageEnglish (US)
Pages (from-to)776-786
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume440
Issue number1
DOIs
StatePublished - Apr 2014

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escape
galaxies
continuums
stars
photons
emissivity
radiative transfer
ionization
intergalactic media
hydrodynamics
emitters
dust
ion
simulation
luminosity
metallicity
boxes
narrowband
star formation
broadband

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

@article{f38d87b17e8c4a288d4c92f3d8045412,
title = "Escape of Lyα and continuum photons from star-forming galaxies",
abstract = "A large number of high-redshift galaxies have been discovered via their narrow-band Lya line or broad-band continuum colours in recent years. The nature of the escaping process of photons from these early galaxies is crucial to understand galaxy evolution and the cosmic reionization. Here, we investigate the escape of Lya, non-ionizing UV-continuum (λ lt; 1300-1600{\AA} in rest frame), and ionizing photons (λ <912 {\AA}) from galaxies by combining a cosmological hydrodynamic simulation with three-dimensional multiwavelength radiative transfer calculations. The galaxies are simulated in a box of 53 h-3 Mpc3 with high resolutions using the Aquila initial condition which reproduces a MilkyWay-like galaxy at redshift z = 0.We find that the escape fraction (fesc) of these different photons shows a complex dependence on redshift and galaxy properties: fLyα esc and fUV esc appear to evolve with redshift, and they show similar, weak correlations with galaxy properties such as mass, star formation, metallicity, and dust content, while fIon esc remains roughly constant at ̃0.2 from z ̃ 0 to 10, and it does not show clear dependence on galaxy properties. fLyα esc correlates more strongly with f UV esc than with f Ion esc . In addition, we find a relation between the emergent Lya luminosity and the ionizing photon emissivity of Lyman Alpha Emitters (LAEs). By combining this relation with the observed luminosity functions of LAEs at different redshift, we estimate the contribution from LAEs to the reionization of intergalactic medium (IGM). Our result suggests that ionizing photons from LAEs alone are not sufficient to ionize IGM at z ≥ 6, but they can maintain the ionization of IGM at z ̃ 0-5.",
author = "Hidenobu Yajima and Yuexing Li and Qirong Zhu and Tom Abel and Caryl Gronwall and Robin Ciardullo",
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Escape of Lyα and continuum photons from star-forming galaxies. / Yajima, Hidenobu; Li, Yuexing; Zhu, Qirong; Abel, Tom; Gronwall, Caryl; Ciardullo, Robin.

In: Monthly Notices of the Royal Astronomical Society, Vol. 440, No. 1, 04.2014, p. 776-786.

Research output: Contribution to journalArticle

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T1 - Escape of Lyα and continuum photons from star-forming galaxies

AU - Yajima, Hidenobu

AU - Li, Yuexing

AU - Zhu, Qirong

AU - Abel, Tom

AU - Gronwall, Caryl

AU - Ciardullo, Robin

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N2 - A large number of high-redshift galaxies have been discovered via their narrow-band Lya line or broad-band continuum colours in recent years. The nature of the escaping process of photons from these early galaxies is crucial to understand galaxy evolution and the cosmic reionization. Here, we investigate the escape of Lya, non-ionizing UV-continuum (λ lt; 1300-1600Å in rest frame), and ionizing photons (λ <912 Å) from galaxies by combining a cosmological hydrodynamic simulation with three-dimensional multiwavelength radiative transfer calculations. The galaxies are simulated in a box of 53 h-3 Mpc3 with high resolutions using the Aquila initial condition which reproduces a MilkyWay-like galaxy at redshift z = 0.We find that the escape fraction (fesc) of these different photons shows a complex dependence on redshift and galaxy properties: fLyα esc and fUV esc appear to evolve with redshift, and they show similar, weak correlations with galaxy properties such as mass, star formation, metallicity, and dust content, while fIon esc remains roughly constant at ̃0.2 from z ̃ 0 to 10, and it does not show clear dependence on galaxy properties. fLyα esc correlates more strongly with f UV esc than with f Ion esc . In addition, we find a relation between the emergent Lya luminosity and the ionizing photon emissivity of Lyman Alpha Emitters (LAEs). By combining this relation with the observed luminosity functions of LAEs at different redshift, we estimate the contribution from LAEs to the reionization of intergalactic medium (IGM). Our result suggests that ionizing photons from LAEs alone are not sufficient to ionize IGM at z ≥ 6, but they can maintain the ionization of IGM at z ̃ 0-5.

AB - A large number of high-redshift galaxies have been discovered via their narrow-band Lya line or broad-band continuum colours in recent years. The nature of the escaping process of photons from these early galaxies is crucial to understand galaxy evolution and the cosmic reionization. Here, we investigate the escape of Lya, non-ionizing UV-continuum (λ lt; 1300-1600Å in rest frame), and ionizing photons (λ <912 Å) from galaxies by combining a cosmological hydrodynamic simulation with three-dimensional multiwavelength radiative transfer calculations. The galaxies are simulated in a box of 53 h-3 Mpc3 with high resolutions using the Aquila initial condition which reproduces a MilkyWay-like galaxy at redshift z = 0.We find that the escape fraction (fesc) of these different photons shows a complex dependence on redshift and galaxy properties: fLyα esc and fUV esc appear to evolve with redshift, and they show similar, weak correlations with galaxy properties such as mass, star formation, metallicity, and dust content, while fIon esc remains roughly constant at ̃0.2 from z ̃ 0 to 10, and it does not show clear dependence on galaxy properties. fLyα esc correlates more strongly with f UV esc than with f Ion esc . In addition, we find a relation between the emergent Lya luminosity and the ionizing photon emissivity of Lyman Alpha Emitters (LAEs). By combining this relation with the observed luminosity functions of LAEs at different redshift, we estimate the contribution from LAEs to the reionization of intergalactic medium (IGM). Our result suggests that ionizing photons from LAEs alone are not sufficient to ionize IGM at z ≥ 6, but they can maintain the ionization of IGM at z ̃ 0-5.

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