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19 April 2024 |
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Article overview
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Measuring the Physical Conditions in High-Redshift Star-Forming Galaxies: Insights from KBSS-MOSFIRE | | Allison L. Strom
; Charles C. Steidel
; Gwen C. Rudie
; Ryan F. Trainor
; Max Pettini
; | | Date: |
23 Nov 2017 | | Abstract: | We use photoionization models designed to reconcile the joint rest-UV-optical
spectra of high-z star-forming galaxies to self-consistently infer the gas
chemistry and nebular ionization and excitation conditions for ~160 galaxies
from the Keck Baryonic Structure Survey (KBSS), using only observations of
their rest-optical nebular spectra. We find that the majority of z~2-3 KBSS
galaxies are moderately O-rich, with an interquartile range in
12+log(O/H)=8.29-8.55, and have significantly sub-solar Fe enrichment, with an
interquartile range of [Fe/H]=[-0.82,-0.54], contributing additional evidence
in favor of super-solar O/Fe in high-z galaxies. Ionization parameter and N/O,
as determined through comparisons with the photoionization models, are strongly
correlated with common strong-line indices (such as O32 and N2O2), whereas
diagnostics commonly used for measuring gas-phase O/H (such as N2 and O3N2) are
relatively insensitive to the overall amount of oxygen present in the gas. We
provide a new calibration using R23 to measure O/H in typical high-z galaxies,
although it is most useful for relatively O-rich galaxies; combining O32 and
R23 does not yield a more effective calibration. Finally, we consider
implications for the intrinsic correlations between physical conditions across
the galaxy sample and find that N/O varies with O/H in high-z galaxies in a
manner almost identical to local extragalactic HII regions. In contrast, we do
not find a strong anti-correlation between ionization parameter and metallicity
(O/H or Fe/H) in high-z galaxies, which is one of the principal bases for using
strong-line ratios to infer oxygen abundance. | | Source: | arXiv, 1711.8820 | | Services: | Forum | Review | PDF | Favorites | |
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