Nebular Emission Line Ratios in z ≃ 2–3 Star-forming Galaxies with KBSS-MOSFIRE: Exploring the Impact of Ionization, Excitation, and Nitrogen-to-Oxygen Ratio
By A. Strom, C. Steidel, G. Rudie, R. Trainor, M. Pettini, Naveen A. Reddy. 2016
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We present a detailed study of the rest-optical (3600–7000 Å) nebular spectra of ∼380 star-forming galaxies at , obtained with Keck/Multi-object Spectrometer for Infrared Exploration (MOSFIRE) as part of the Keck Baryonic Structure Survey (KBSS). The KBSS-MOSFIRE sample is representative of star-forming galaxies at these redshifts, with stellar masses and star formation rates SFR = 3–1000 yr−1. We focus on robust measurements of many strong diagnostic emission lines for individual galaxies: [O ii]λλ3727, 3729, [Ne iii]λ3869, Hβ, [O iii] 4960, 5008, [N ii]λλ 6549, 6585, Hα, and [S ii]λλ6718, 6732. Comparisons with observations of typical local galaxies from the Sloan Digital Sky Survey and between subsamples of KBSS-MOSFIRE show that high-redshift galaxies exhibit a number of significant differences in addition to the well-known offset in log([O iii] /Hβ) and log([N ii] /Hα). We argue that the primary difference between H ii regions in galaxies and those at is an enhancement in the degree of nebular excitation, as measured by [O iii]/Hβ and [([O iii] +[O ii] )/Hβ]. At the same time, KBSS-MOSFIRE galaxies are ∼10 times more massive than galaxies with similar ionizing spectra and have higher N/O (likely accompanied by higher O/H) at fixed excitation. These results indicate the presence of harder ionizing radiation fields at fixed N/O and O/H relative to typical galaxies, consistent with Fe-poor stellar population models that include massive binaries, and highlight a population of massive, high-specific star formation rate galaxies at high redshift with systematically different star formation histories than galaxies of similar stellar mass today.
View Paper: https://www.semanticscholar.org/paper/d4124ef4d0721de89ad88237722b9c81dd935da2
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Citations in the corpus
- The SINS/zC-SINF Survey of z ∼ 2 Galaxy Kinematics: SINFONI Adaptive Optics–assisted Data and Kiloparsec-scale Emission-line Properties (2018, background): “…ratio, as amply discussed in the literature 5 (e.g., Kewley & Dopita 2002; Kewley et al. 2013; Pérez-Montero & Contini 2009; Yuan et al. 2012; Andrews & Martini 2013; Steidel et al. 2014; Shapley et al. 2015; Sanders et al. 2015, 2017; Kashino et al. 2017; Strom et al. 2017; Cresci et al. 2017).”
- JWST Census for the Mass–Metallicity Star Formation Relations at z = 4–10 with Self-consistent Flux Calibration and Proper Metallicity Calibrators (2023, methodology): “…of lower-redshift samples of continuum-selected galaxies ( Nakajima & Ouchi 2014; Troncoso et al. 2014; Sanders et al. 2016; Onodera et al. 2016; Strom et al. 2017 ) and Ly α emitting galaxies ( LAEs; Nakajima & Ouchi 2014; Erb et al. 2016; Nakajima et al. 2020 ) , as indicated in the legend.”
- Near infrared spectroscopy and star-formation histories of 3 ≤ z ≤ 4 quiescent galaxies (2018, background): “Recent results suggest this criterion should be made even stricter, shifting the z ∼ 0 critetion of Juneau et al. (2011) by 1 dex in mass (Strom et al. 2017); this would reduce the fraction of AGNs among our [O iii] emitters to 40%, which remains substantial.”