RECONCILING THE STELLAR AND NEBULAR SPECTRA OF HIGH-REDSHIFT GALAXIES
By C. Steidel, A. Strom, M. Pettini, G. Rudie, Naveen A. Reddy, R. Trainor. 2016
206 citations recorded by the source corpus.
We present a combined analysis of rest-frame far-UV (FUV; 1000–2000 Å) and rest-frame optical (3600–7000 Å) composite spectra formed from very deep Keck/LRIS and Keck/MOSFIRE observations of a sample of 30 star-forming galaxies with , selected to be broadly representative of the full KBSS-MOSFIRE spectroscopic survey. Since the same massive stars are responsible for the observed FUV continuum and for the excitation of the observed nebular emission, a self-consistent stellar population synthesis model should simultaneously match the details of the FUV stellar+nebular continuum and—when inserted as the excitation source in photoionization models—predict all observed nebular emission line ratios. We find that only models including massive star binaries, having low stellar metallicity ( ) but relatively high nebular (ionized gas-phase) abundances ( ), can successfully match all of the observational constraints. We show that this apparent discrepancy is naturally explained by highly super-solar O/Fe ( ), expected for a gas whose enrichment is dominated by the products of core-collapse supernovae. While O dominates the physics of the ionized gas (and thus the nebular emission lines), Fe dominates the extreme-UV (EUV) and FUV opacity and controls the mass-loss rate from massive stars, resulting in particularly dramatic effects for massive stars in binary systems. This high nebular excitation—caused by the hard EUV spectra of Fe-poor massive stars—is much more common at high redshift than low redshift due to systematic differences in the star formation history of typical galaxies.
Subfields: Astronomy and Astrophysics, Instrumentation
View Paper: https://www.semanticscholar.org/paper/905f474a12c49aaf4dc673ad7b13d533bf539a58
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Citations in the corpus
- Nebular Continuum and Line Emission in Stellar Population Synthesis Models (2016, methodology): “The Padova+Geneva models are shown in gray, and are unable to produce enough [He II] emission to explain the observed He2 line ratios from Steidel et al. (2016).”
- Near infrared spectroscopy and star-formation histories of 3 ≤ z ≤ 4 quiescent galaxies (2018, background): “…with the upcoming James Webb Space Telescope (JWST), although given the expected change in gas-phase metallicity and ionization parameters in high redshift galaxies (e.g., Erb et al. 2010; Steidel et al. 2016; Shapley et al. 2017), an evolution of the [O ii] SFR calibration would not be surprising.”
- 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 (2016, background): “These measurements show that the KBSS stack, which is representative of the full KBSS-MOSFIRE sample discussed here (c.f. the yellow point in Figure 17), is consistent with the N/O-O/H relation observed for the sample of H II regions from Pil12 (see Figure 16 of Steidel et al. 2016).”
- Binary Population and Spectral Synthesis Version 2.1: Construction, Observational Verification, and New Results (2017, methodology): “Steidel et al. (2016) have suggested that the spectra of galaxies at z ∼ 2 − 3 are best fit by combining very low metallicity stellar spectra (the observed properties of which are most strongly influenced by the iron abundance) with somewhat higher metallicity nebular gas (the properties of which…”
- Modelling the nebular emission from primeval to present-day star-forming galaxies (2016, methodology): “…of H ii regions and galaxies in the nearby Universe, which increasingly appear as inappropriate to study the star formation and ISM conditions of chemically young galaxies (e.g., Erb et al. 2010; Steidel et al. 2014, 2016; Shapley et al. 2015; see also Brinchmann et al. 2008; Shirazi et al. 2014).”
- Rapid Reionization by the Oligarchs: The Case for Massive, UV-bright, Star-forming Galaxies with High Escape Fractions (2019, background): “…the strong nebular fluxes, high ionization lines, and extreme line widths that are now known to be ubiquitous at z∼2.5–3.5 (e.g., Holden et al. 2016; Steidel et al. 2016; Reddy et al. 2018b) and also commonly seen at z>6 (e.g., Stark et al. 2015; RobertsBorsani et al. 2016; Mainali et al. 2017).”
- The HDUV Survey: A Revised Assessment of the Relationship between UV Slope and Dust Attenuation for High-redshift Galaxies (2017, background): “Alternatively, the lower gas-phase [Si/O] measured from the composite rest-frame UV spectrum of z ∼ 2 galaxies relative to the solar value indicates significant depletion of Si onto dust grains, while carbon is under-abundant relative to oxygen (Steidel et al. 2016).”