The MOSDEF Survey: First Measurement of Nebular Oxygen Abundance at z > 4

Alice E. Shapley, Ryan L. Sanders, Naveen A. Reddy, Mariska Kriek, William R. Freeman, Bahram Mobasher, Brian Siana, Alison L. Coil, Gene C.K. Leung, Laura Degroot, Irene Shivaei, Sedona H. Price, Mojegan Azadi, James Aird

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

We present the first spectroscopic measurement of multiple rest-frame optical emission lines at z > 4. During the MOSFIRE Deep Evolution Field survey, we observed the galaxy GOODSN-17940 with the Keck I/MOSFIRE spectrograph. The K-band spectrum of GOODSN-17940 includes significant detections of the [O ii]λλ3726,3729, [Ne iii]λ3869, and Hγ emission lines and a tentative detection of Hδ, indicating z spec = 4.4121. GOODSN-17940 is an actively star-forming z > 4 galaxy based on its K-band spectrum and broadband spectral energy distribution. A significant excess relative to the surrounding continuum is present in the Spitzer/IRAC channel 1 photometry of GOODSN-17940, due primarily to strong Hα emission with a rest-frame equivalent width of EW(Hα) = 1200. Based on the assumption of 0.5 Z o models and the Calzetti attenuation curve, GOODSN-17940 is characterized by . The Balmer decrement inferred from Hα/Hγ is used to dust correct the Hα emission, yielding . These M and star formation rate (SFR) values place GOODSN-17940 an order of magnitude in SFR above the z ∼ 4 star-forming "main sequence." Finally, we use the observed ratio of [Ne iii]/[O ii] to estimate the nebular oxygen abundance in GOODSN-17940, finding O/H ∼ 0.2 (O/H)o. Combining our new [Ne iii]/[O ii] measurement with those from stacked spectra at z ∼ 0, 2, and 3, we show that GOODSN-17940 represents an extension to z > 4 of the evolution toward higher [Ne iii]/[O ii] (i.e., lower O/H) at fixed stellar mass. It will be possible to perform the measurements presented here out to z ∼ 10 using the James Webb Space Telescope.

Original languageEnglish
Article numberL30
JournalAstrophysical Journal Letters
Volume846
Issue number2
DOIs
StatePublished - Sep 10 2017

Bibliographical note

Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved.

Keywords

  • galaxies: ISM
  • galaxies: evolution
  • galaxies: high-redshift

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint

Dive into the research topics of 'The MOSDEF Survey: First Measurement of Nebular Oxygen Abundance at z > 4'. Together they form a unique fingerprint.

Cite this