The spectrally resolved Lyα emission of three Lyα-selected field galaxies at z ∼ 2.4 from the hetdex pilot survey

Taylor S. Chonis, Guillermo A. Blanc, Gary J. Hill, Joshua J. Adams, Steven L. Finkelstein, Karl Gebhardt, Juna A. Kollmeier, Robin Ciardullo, Niv Drory, Caryl Gronwall, Alex Hagen, Roderik A. Overzier, Mimi Song, Gregory R. Zeimann

Research output: Contribution to journalReview article

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Abstract

We present new results on the spectrally resolved Lyα emission of three Lyα-emitting field galaxies at z ∼ 2.4 with high Lyα equivalent width (>100 Å) and Lyα luminosity (∼10 43 erg s-1). At 120 km s-1 (FWHM) spectral resolution, the prominent double-peaked Lyα profile straddles the systemic velocity, where the velocity zero point is determined from spectroscopy of the galaxies' rest-frame optical nebular emission lines. The average velocity offset from systemic of the stronger redshifted emission component for our sample is 176 km s-1 while the average total separation between the redshifted and main blueshifted emission components is 380 km s-1. These measurements are a factor of ∼2 smaller than for UV-continuum-selected galaxies that show Lyα in emission with lower Lyα equivalent widths. We compare our Lyα spectra to the predicted line profiles of a spherical "expanding shell" Lyα radiative transfer grid that models large-scale galaxy outflows. Specifically, blueward of the systemic velocity where two galaxies show a weak, highly blueshifted (by ∼1000 km s -1) tertiary emission peak, the model line profiles are a relatively poor representation of the observed spectra. Since the neutral gas column density has a dominant influence over the shape of the Lyα line profile, we caution against equating the observed Lyα velocity offset with a physical outflow velocity, especially at lower spectral resolution where the unresolved Lyα velocity offset is a convoluted function of several degenerate parameters. Referring to rest-frame ultraviolet and optical Hubble Space Telescope imaging, we find that galaxy-galaxy interactions may play an important role in inducing a starburst that results in copious Lyα emission as well as perturbing the gas distribution and velocity field, both of which have strong influence over the Lyα emission line profile.

Original languageEnglish (US)
Article number99
JournalAstrophysical Journal
Volume775
Issue number2
DOIs
StatePublished - Oct 1 2013

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galaxies
profiles
spectral resolution
outflow
interacting galaxies
spherical shells
neutral gases
Hubble Space Telescope
radiative transfer
light emission
gas
erg
velocity distribution
grids
luminosity
continuums
spectroscopy
shell
gases

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Chonis, T. S., Blanc, G. A., Hill, G. J., Adams, J. J., Finkelstein, S. L., Gebhardt, K., ... Zeimann, G. R. (2013). The spectrally resolved Lyα emission of three Lyα-selected field galaxies at z ∼ 2.4 from the hetdex pilot survey. Astrophysical Journal, 775(2), [99]. https://doi.org/10.1088/0004-637X/775/2/99
Chonis, Taylor S. ; Blanc, Guillermo A. ; Hill, Gary J. ; Adams, Joshua J. ; Finkelstein, Steven L. ; Gebhardt, Karl ; Kollmeier, Juna A. ; Ciardullo, Robin ; Drory, Niv ; Gronwall, Caryl ; Hagen, Alex ; Overzier, Roderik A. ; Song, Mimi ; Zeimann, Gregory R. / The spectrally resolved Lyα emission of three Lyα-selected field galaxies at z ∼ 2.4 from the hetdex pilot survey. In: Astrophysical Journal. 2013 ; Vol. 775, No. 2.
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abstract = "We present new results on the spectrally resolved Lyα emission of three Lyα-emitting field galaxies at z ∼ 2.4 with high Lyα equivalent width (>100 {\AA}) and Lyα luminosity (∼10 43 erg s-1). At 120 km s-1 (FWHM) spectral resolution, the prominent double-peaked Lyα profile straddles the systemic velocity, where the velocity zero point is determined from spectroscopy of the galaxies' rest-frame optical nebular emission lines. The average velocity offset from systemic of the stronger redshifted emission component for our sample is 176 km s-1 while the average total separation between the redshifted and main blueshifted emission components is 380 km s-1. These measurements are a factor of ∼2 smaller than for UV-continuum-selected galaxies that show Lyα in emission with lower Lyα equivalent widths. We compare our Lyα spectra to the predicted line profiles of a spherical {"}expanding shell{"} Lyα radiative transfer grid that models large-scale galaxy outflows. Specifically, blueward of the systemic velocity where two galaxies show a weak, highly blueshifted (by ∼1000 km s -1) tertiary emission peak, the model line profiles are a relatively poor representation of the observed spectra. Since the neutral gas column density has a dominant influence over the shape of the Lyα line profile, we caution against equating the observed Lyα velocity offset with a physical outflow velocity, especially at lower spectral resolution where the unresolved Lyα velocity offset is a convoluted function of several degenerate parameters. Referring to rest-frame ultraviolet and optical Hubble Space Telescope imaging, we find that galaxy-galaxy interactions may play an important role in inducing a starburst that results in copious Lyα emission as well as perturbing the gas distribution and velocity field, both of which have strong influence over the Lyα emission line profile.",
author = "Chonis, {Taylor S.} and Blanc, {Guillermo A.} and Hill, {Gary J.} and Adams, {Joshua J.} and Finkelstein, {Steven L.} and Karl Gebhardt and Kollmeier, {Juna A.} and Robin Ciardullo and Niv Drory and Caryl Gronwall and Alex Hagen and Overzier, {Roderik A.} and Mimi Song and Zeimann, {Gregory R.}",
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Chonis, TS, Blanc, GA, Hill, GJ, Adams, JJ, Finkelstein, SL, Gebhardt, K, Kollmeier, JA, Ciardullo, R, Drory, N, Gronwall, C, Hagen, A, Overzier, RA, Song, M & Zeimann, GR 2013, 'The spectrally resolved Lyα emission of three Lyα-selected field galaxies at z ∼ 2.4 from the hetdex pilot survey', Astrophysical Journal, vol. 775, no. 2, 99. https://doi.org/10.1088/0004-637X/775/2/99

The spectrally resolved Lyα emission of three Lyα-selected field galaxies at z ∼ 2.4 from the hetdex pilot survey. / Chonis, Taylor S.; Blanc, Guillermo A.; Hill, Gary J.; Adams, Joshua J.; Finkelstein, Steven L.; Gebhardt, Karl; Kollmeier, Juna A.; Ciardullo, Robin; Drory, Niv; Gronwall, Caryl; Hagen, Alex; Overzier, Roderik A.; Song, Mimi; Zeimann, Gregory R.

In: Astrophysical Journal, Vol. 775, No. 2, 99, 01.10.2013.

Research output: Contribution to journalReview article

TY - JOUR

T1 - The spectrally resolved Lyα emission of three Lyα-selected field galaxies at z ∼ 2.4 from the hetdex pilot survey

AU - Chonis, Taylor S.

AU - Blanc, Guillermo A.

AU - Hill, Gary J.

AU - Adams, Joshua J.

AU - Finkelstein, Steven L.

AU - Gebhardt, Karl

AU - Kollmeier, Juna A.

AU - Ciardullo, Robin

AU - Drory, Niv

AU - Gronwall, Caryl

AU - Hagen, Alex

AU - Overzier, Roderik A.

AU - Song, Mimi

AU - Zeimann, Gregory R.

PY - 2013/10/1

Y1 - 2013/10/1

N2 - We present new results on the spectrally resolved Lyα emission of three Lyα-emitting field galaxies at z ∼ 2.4 with high Lyα equivalent width (>100 Å) and Lyα luminosity (∼10 43 erg s-1). At 120 km s-1 (FWHM) spectral resolution, the prominent double-peaked Lyα profile straddles the systemic velocity, where the velocity zero point is determined from spectroscopy of the galaxies' rest-frame optical nebular emission lines. The average velocity offset from systemic of the stronger redshifted emission component for our sample is 176 km s-1 while the average total separation between the redshifted and main blueshifted emission components is 380 km s-1. These measurements are a factor of ∼2 smaller than for UV-continuum-selected galaxies that show Lyα in emission with lower Lyα equivalent widths. We compare our Lyα spectra to the predicted line profiles of a spherical "expanding shell" Lyα radiative transfer grid that models large-scale galaxy outflows. Specifically, blueward of the systemic velocity where two galaxies show a weak, highly blueshifted (by ∼1000 km s -1) tertiary emission peak, the model line profiles are a relatively poor representation of the observed spectra. Since the neutral gas column density has a dominant influence over the shape of the Lyα line profile, we caution against equating the observed Lyα velocity offset with a physical outflow velocity, especially at lower spectral resolution where the unresolved Lyα velocity offset is a convoluted function of several degenerate parameters. Referring to rest-frame ultraviolet and optical Hubble Space Telescope imaging, we find that galaxy-galaxy interactions may play an important role in inducing a starburst that results in copious Lyα emission as well as perturbing the gas distribution and velocity field, both of which have strong influence over the Lyα emission line profile.

AB - We present new results on the spectrally resolved Lyα emission of three Lyα-emitting field galaxies at z ∼ 2.4 with high Lyα equivalent width (>100 Å) and Lyα luminosity (∼10 43 erg s-1). At 120 km s-1 (FWHM) spectral resolution, the prominent double-peaked Lyα profile straddles the systemic velocity, where the velocity zero point is determined from spectroscopy of the galaxies' rest-frame optical nebular emission lines. The average velocity offset from systemic of the stronger redshifted emission component for our sample is 176 km s-1 while the average total separation between the redshifted and main blueshifted emission components is 380 km s-1. These measurements are a factor of ∼2 smaller than for UV-continuum-selected galaxies that show Lyα in emission with lower Lyα equivalent widths. We compare our Lyα spectra to the predicted line profiles of a spherical "expanding shell" Lyα radiative transfer grid that models large-scale galaxy outflows. Specifically, blueward of the systemic velocity where two galaxies show a weak, highly blueshifted (by ∼1000 km s -1) tertiary emission peak, the model line profiles are a relatively poor representation of the observed spectra. Since the neutral gas column density has a dominant influence over the shape of the Lyα line profile, we caution against equating the observed Lyα velocity offset with a physical outflow velocity, especially at lower spectral resolution where the unresolved Lyα velocity offset is a convoluted function of several degenerate parameters. Referring to rest-frame ultraviolet and optical Hubble Space Telescope imaging, we find that galaxy-galaxy interactions may play an important role in inducing a starburst that results in copious Lyα emission as well as perturbing the gas distribution and velocity field, both of which have strong influence over the Lyα emission line profile.

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DO - 10.1088/0004-637X/775/2/99

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