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Title: Hubble space telescope emission line galaxies at z ∼ 2: the Lyα escape fraction

Abstract

We compare the Hβ line strengths of 1.90 < z < 2.35 star-forming galaxies observed with the near-IR grism of the Hubble Space Telescope with ground-based measurements of Lyα from the HETDEX Pilot Survey and narrow-band imaging. By examining the line ratios of 73 galaxies, we show that most star-forming systems at this epoch have a Lyα escape fraction below ∼6%. We confirm this result by using stellar reddening to estimate the effective logarithmic extinction of the Hβ emission line (c {sub Hβ} = 0.5) and measuring both the Hβ and Lyα luminosity functions in a ∼100, 000 Mpc{sup 3} volume of space. We show that in our redshift window, the volumetric Lyα escape fraction is at most 4.4{sub −1.2}{sup +2.1}%, with an additional systematic ∼25% uncertainty associated with our estimate of extinction. Finally, we demonstrate that the bulk of the epoch's star-forming galaxies have Lyα emission line optical depths that are significantly greater than that for the underlying UV continuum. In our predominantly [O III] λ5007-selected sample of galaxies, resonant scattering must be important for the escape of Lyα photons.

Authors:
; ; ; ; ; ;
Publication Date:
OSTI Identifier:
22369984
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 796; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPARATIVE EVALUATIONS; COSMOLOGY; EMISSION; EMISSION SPECTRA; GALAXIES; LUMINOSITY; LYMAN LINES; MASS; NEAR INFRARED RADIATION; PHOTONS; RED SHIFT; RESONANCE SCATTERING; SPACE; STAR EVOLUTION; STARS; TELESCOPES

Citation Formats

Ciardullo, Robin, Zeimann, Gregory R., Gronwall, Caryl, Gebhardt, Henry, Schneider, Donald P., Hagen, Alex, Malz, A. I., E-mail: rbc@astro.psu.edu, E-mail: grzeimann@psu.edu, E-mail: caryl@astro.psu.edu, E-mail: gebhardt@psu.edu, E-mail: dps@astro.psu.edu, E-mail: hagen@psu.edu, E-mail: malz@psu.edu, and others, and. Hubble space telescope emission line galaxies at z ∼ 2: the Lyα escape fraction. United States: N. p., 2014. Web. doi:10.1088/0004-637X/796/1/64.
Ciardullo, Robin, Zeimann, Gregory R., Gronwall, Caryl, Gebhardt, Henry, Schneider, Donald P., Hagen, Alex, Malz, A. I., E-mail: rbc@astro.psu.edu, E-mail: grzeimann@psu.edu, E-mail: caryl@astro.psu.edu, E-mail: gebhardt@psu.edu, E-mail: dps@astro.psu.edu, E-mail: hagen@psu.edu, E-mail: malz@psu.edu, & others, and. Hubble space telescope emission line galaxies at z ∼ 2: the Lyα escape fraction. United States. https://doi.org/10.1088/0004-637X/796/1/64
Ciardullo, Robin, Zeimann, Gregory R., Gronwall, Caryl, Gebhardt, Henry, Schneider, Donald P., Hagen, Alex, Malz, A. I., E-mail: rbc@astro.psu.edu, E-mail: grzeimann@psu.edu, E-mail: caryl@astro.psu.edu, E-mail: gebhardt@psu.edu, E-mail: dps@astro.psu.edu, E-mail: hagen@psu.edu, E-mail: malz@psu.edu, and others, and. 2014. "Hubble space telescope emission line galaxies at z ∼ 2: the Lyα escape fraction". United States. https://doi.org/10.1088/0004-637X/796/1/64.
@article{osti_22369984,
title = {Hubble space telescope emission line galaxies at z ∼ 2: the Lyα escape fraction},
author = {Ciardullo, Robin and Zeimann, Gregory R. and Gronwall, Caryl and Gebhardt, Henry and Schneider, Donald P. and Hagen, Alex and Malz, A. I., E-mail: rbc@astro.psu.edu, E-mail: grzeimann@psu.edu, E-mail: caryl@astro.psu.edu, E-mail: gebhardt@psu.edu, E-mail: dps@astro.psu.edu, E-mail: hagen@psu.edu, E-mail: malz@psu.edu and others, and},
abstractNote = {We compare the Hβ line strengths of 1.90 < z < 2.35 star-forming galaxies observed with the near-IR grism of the Hubble Space Telescope with ground-based measurements of Lyα from the HETDEX Pilot Survey and narrow-band imaging. By examining the line ratios of 73 galaxies, we show that most star-forming systems at this epoch have a Lyα escape fraction below ∼6%. We confirm this result by using stellar reddening to estimate the effective logarithmic extinction of the Hβ emission line (c {sub Hβ} = 0.5) and measuring both the Hβ and Lyα luminosity functions in a ∼100, 000 Mpc{sup 3} volume of space. We show that in our redshift window, the volumetric Lyα escape fraction is at most 4.4{sub −1.2}{sup +2.1}%, with an additional systematic ∼25% uncertainty associated with our estimate of extinction. Finally, we demonstrate that the bulk of the epoch's star-forming galaxies have Lyα emission line optical depths that are significantly greater than that for the underlying UV continuum. In our predominantly [O III] λ5007-selected sample of galaxies, resonant scattering must be important for the escape of Lyα photons.},
doi = {10.1088/0004-637X/796/1/64},
url = {https://www.osti.gov/biblio/22369984}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 796,
place = {United States},
year = {Thu Nov 20 00:00:00 EST 2014},
month = {Thu Nov 20 00:00:00 EST 2014}
}