HUBBLE SPACE TELESCOPE EMISSION-LINE GALAXIES AT z ∼ 2: THE MYSTERY OF NEON

Journal Article · Thu Jan 01 04:00:00 EST 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/798/1/29· OSTI ID:22364751

Zeimann, Gregory R.; Ciardullo, Robin; Gebhardt, Henry; Gronwall, Caryl; Hagen, Alex; Trump, Jonathan R.; Bridge, Joanna S.; Luo, Bin

We use near-infrared grism spectroscopy from the Hubble Space Telescope to examine the strength of [Ne III] λ3869 relative to Hβ, [O II] λ3727, and [O III] λ5007 in 236 low-mass (7.5 ≲ log (M {sub *}/M {sub ☉}) ≲ 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 {sup 22}Ne 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.

• OSTI ID: 22364751
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 798; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COMPARATIVE EVALUATIONS
EMISSION SPECTRA
EMISSION SPECTROSCOPY
GALAXIES
GALAXY NUCLEI
MASS
NEON IONS
OXYGEN
OXYGEN IONS
RED SHIFT
STAR EVOLUTION
TELESCOPES
UNIVERSE
WOLF-RAYET STARS
X RADIATION