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Abstract Using deep near-infrared Keck/MOSFIRE observations, we analyze the rest-optical spectra of eight star-forming galaxies in the COSMOS and GOODS-N fields. We reach integration times of ∼10 hr in the deepest bands, pushing the limits on current ground-based observational capabilities. The targets fall into two redshift bins, of five galaxies atz∼ 1.7 and three galaxies atz∼ 2.5, and were selected as likely to yield significant auroral-line detections. Even with long integration times, detection of the auroral lines remains challenging. We stack the spectra together into subsets based on redshift, improving the signal-to-noise ratio on the [Oiii]λ4364 auroral emission line and, in turn, enabling a direct measurement of the oxygen abundance for each stack. We compare these measurements to commonly employed strong-line ratios alongside measurements from the literature. We find that the stacks fall within the distribution ofz> 1 literature measurements, but a larger sample size is needed to robustly constrain the relationships between strong-line ratios and oxygen abundance at high redshift. We additionally report detections of [Oi]λ6302 for nine individual galaxies and composite spectra of 21 targets in the MOSFIRE pointings. We plot their line ratios on the [Oiii]λ5008/Hβversus [Oi]λ6302/Hαdiagnostic diagram, comparing our targets to local galaxies and Hiiregions. We find that the [Oi]/Hαratios in our sample of galaxies are consistent with being produced in gas ionized byα-enhanced massive stars, as has been previously inferred for rapidly forming galaxies at early cosmic times.
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SALT-RSS Multiobject Spectroscopic Data Reduction to Reveal Physical Properties of [O ii]-emitting Galaxies from HETDEX and ODIN
Abstract Line flux ratios from [O ii] doublets can probe electron densities in the interstellar medium of galaxies. We employ the Southern African Large Telescope’s (SALT) Robert Stobie Spectrograph (RSS), which provides sufficient resolution (R ∼ 3000) to split the [O ii] doublets, to target galaxies from Hobby-Eberly Telescope Dark Energy Experiment and One-hundred-deg2DECam Imaging in Narrowbands with emission line fluxes of at least 2 × 10−16 erg cm−2 s−1. Reduction is carried out using RSSMOSPipeline to reduce SALT-RSS data through wavelength calibration. Despite SALT-RSS being known for its difficulty to flux calibrate, we present spectra that have been flux calibrated using alignment stars with Sloan Digital Sky Survey spectra as standards. We combine multiple spectroscopic settings to obtain full 2D spectra across a wavelength range of 3500–9500 Å. A 1D spectrum can then be extracted to calculate flux ratios and line widths, revealing important physical properties of these bright [O ii]-emitters.
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- PAR ID:
- 10505192
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- Research Notes of the AAS
- Volume:
- 8
- Issue:
- 5
- ISSN:
- 2515-5172
- Format(s):
- Medium: X Size: Article No. 125
- Size(s):
- Article No. 125
- Sponsoring Org:
- National Science Foundation
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