TY - JOUR
T1 - Hubble Space Telescope emission-line galaxies atz - 2
T2 - The mystery of neon
AU - Zeimann, Gregory R.
AU - Ciardullo, Robin
AU - Gebhardt, Henry
AU - Gronwall, Caryl
AU - Hagen, Alex
AU - Trump, Jonathan R.
AU - Bridge, Joanna S.
AU - Luo, Bin
AU - Schneider, Donald P.
N1 - Publisher Copyright:
© 2015. The American Astronomical Society. All rights reserved.
PY - 2015/1/1
Y1 - 2015/1/1
N2 - We use near-infrared grism spectroscopy from the Hubble Space Telescope to examine the strength of [Ne III] λ3869 relative to Hβ, [OII] λ3727, and [OIII] λ5007 in 236 low-mass (7.5 ≲ log(M∗/M⊙ ) ≲ 10.5) star-forming galaxies in the redshift range 1.90 < z < 2.35. By stacking the data by stellar mass, we show that the [Ne III]/[O II] ratios of the z - 2 universe are marginally higher than those seen in a comparable set of local Sloan Digital Sky Survey galaxies, and that [Ne III]/[O III] is enhanced by -0.2 dex. We consider the possible explanations for this -4σ result, including higher oxygen depletion out of the gas phase, denser H ii regions, higher production of 22Ne via Wolf-Rayet stars, and the existence of a larger population of X-ray obscured active galactic nuclei at z - 2 compared to z - 0. None of these simple scenarios, alone, are favored to explain the observed line ratios. We conclude by suggesting several avenues of future observations to further explore the mystery of enhanced [Ne III] emission.
AB - We use near-infrared grism spectroscopy from the Hubble Space Telescope to examine the strength of [Ne III] λ3869 relative to Hβ, [OII] λ3727, and [OIII] λ5007 in 236 low-mass (7.5 ≲ log(M∗/M⊙ ) ≲ 10.5) star-forming galaxies in the redshift range 1.90 < z < 2.35. By stacking the data by stellar mass, we show that the [Ne III]/[O II] ratios of the z - 2 universe are marginally higher than those seen in a comparable set of local Sloan Digital Sky Survey galaxies, and that [Ne III]/[O III] is enhanced by -0.2 dex. We consider the possible explanations for this -4σ result, including higher oxygen depletion out of the gas phase, denser H ii regions, higher production of 22Ne via Wolf-Rayet stars, and the existence of a larger population of X-ray obscured active galactic nuclei at z - 2 compared to z - 0. None of these simple scenarios, alone, are favored to explain the observed line ratios. We conclude by suggesting several avenues of future observations to further explore the mystery of enhanced [Ne III] emission.
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U2 - 10.1088/0004-637X/798/1/29
DO - 10.1088/0004-637X/798/1/29
M3 - Article
AN - SCOPUS:84919489289
SN - 0004-637X
VL - 798
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 29
ER -