NEW STRONG-LINE ABUNDANCE DIAGNOSTICS FOR H ii REGIONS: EFFECTS OF κ-DISTRIBUTED ELECTRON ENERGIES AND NEW ATOMIC DATA

By M. Dopita, R. Sutherland, D. Nicholls, Lisa J. Kewley, Frédéric P. A. Vogt. 2013

239 citations recorded by the source corpus.

Recently, Nicholls et al., inspired by in situ observations of solar system astrophysical plasmas, suggested that the electrons in H ii regions are characterized by a κ-distribution of energies rather than a simple Maxwell–Boltzmann distribution. Here, we have collected together new atomic data within a modified photoionization code to explore the effects of both the new atomic data and the κ-distribution on the strong-line techniques used to determine chemical abundances in H ii regions. By comparing the recombination temperatures (Trec) with the forbidden line temperatures (TFL), we conclude that κ ∼ 20. While representing only a mild deviation from equilibrium, this result is sufficient to strongly influence abundances determined using methods that depend on measurements of the electron temperature from forbidden lines. We present a number of new emission line ratio diagnostics that cleanly separate the two parameters determining the optical spectrum of H ii regions—the ionization parameter q or and the chemical abundance, 12+log(O/H). An automated code to extract these parameters is presented. Using the homogeneous data set from van Zee et al., we find self-consistent results between all of these different diagnostics. The systematic errors between different line ratio diagnostics are much smaller than those found in the earlier strong-line work. Overall, the effect of the κ-distribution on the strong-line abundances derived solely on the basis of theoretical models is rather small.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/b4a88e94832a3882469e3adce30a49059129025f

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Citations in the corpus

• STRONG NEBULAR LINE RATIOS IN THE SPECTRA of z ∼ 2–3 STAR FORMING GALAXIES: FIRST RESULTS FROM KBSS-MOSFIRE (2014, background): “It has also been argued that Te-based metallicities may be biased low due to temperature gradients and/or by the details of the electron energy distribution (e.g., Stasińska 2005; Dopita et al. 2013).”
• SDSS IV MaNGA – metallicity and nitrogen abundance gradients in local galaxies (2017, background): “Despite recent advances (Dopita et al. 2013; Perez-Montero 2014; Blanc et al. 2015; Asari et al. 2016; Curti et al. 2017), reliably measuring the gas metallicity from strong emission lines ratios remains a difficult problem in observational astrophysics.”
• PHYSICAL PROPERTIES OF EMISSION-LINE GALAXIES AT z ∼ 2 FROM NEAR-INFRARED SPECTROSCOPY WITH MAGELLAN FIRE (2014, methodology): “As pointed out by Dopita et al. (2013), R23based metallicities should be treated with caution, particularly as the ratio is only weakly sensitive to abundance for 8.3 .”
• New calibrations for abundance determinations in H ii regions (2016, unknown): “Grids of photoionization models of Hii regions can be used to establish a relation between strong-line intensities and oxygen abundances (e.g.,McCall, Rybski & Shields 1985; Dopita & Evans 1986; McGaugh 1991; Kewley & Dopita 2002; Dopita et al. 2013).”
• THE MOSDEF SURVEY: ELECTRON DENSITY AND IONIZATION PARAMETER AT z ∼ 2.3 (2015, background): “Recent investigations (Nicholls et al. 2013; Dopita et al. 2013) have suggested advantages in using the most up-to-date collision strength and transition probability atomic data instead of outdated values included in the IRAF routine temden (Shaw & Dufour 1994).”
• The SAMI Galaxy Survey: shocks and outflows in a normal star-forming galaxy (2014, methodology): “We use the latest MAPPINGS IV code (Dopita et al. 2013), which incorporates a new non-thermal electron energy excitation (Nicholls, Dopita & Sutherland 2012; Nicholls et al. 2013) and updated atomic data, to model the line ratios.”
• A BUDGET AND ACCOUNTING OF METALS AT z ∼ 0: RESULTS FROM THE COS-HALOS SURVEY (2013, background): “…in galaxies; it is possible that new emission line diagnostics adopting a κ-distribution for the electron energies could resolve some of the systematic uncertainties currently plaguing this field, leading to smaller uncertainties in the near future (Nicholls et al. 2012; Dopita et al. 2013).”
• Nebular Continuum and Line Emission in Stellar Population Synthesis Models (2016, methodology): “For the nebular model based on MIST ionizing spectra, we apply the gas phase abundances used in Dopita et al. (2013), which are based on the Grevesse et al. (2010) solar abundance set.”
• SDSS-IV MaNGA : the impact of diffuse ionized gas on emission-line ratios, interpretation of diagnostic diagrams and gas metallicity measurements (2016, methodology): “When metallicity, ionization parameter, density, or ionizing spectrum change, the location of ionized gas on the BPT diagram changes (e.g., Dopita et al. 2000, 2013; Kewley et al. 2002, 2013a,b).”
• The origin and evolution of the galaxy mass–metallicity relation (2015, background): “Alternatively, it has also been proposed that the observed MZR could continue to rise at the highmetallicity end when using new metallicity diagnostics that account for non-equilibrium electron energy distributions (see e.g. Dopita et al. 2013; Nicholls et al. 2013).”
• Modelling the nebular emission from primeval to present-day star-forming galaxies (2016, methodology): “…the dependence of carbon production on metallicity has resulted in the secondary component to be either ignored (e.g., CL01, Kewley & Dopita 2002) or assigned a specific dependence on the O/H ratio (e.g., Dopita et al. 2013) in previous models of nebular emission from H ii regions and galaxies.”
• Relativistic jet feedback in high-redshift galaxies – I. Dynamics (2016, methodology): “This code is the latest version of the MAPPINGS 4.0 code described in Nicholls et al. (2013) and Dopita et al. (2013), and includes numerous upgrades to both the input atomic physics (CHIANTI v8, Del Zanna et al. 2015) and new methods of solution.”
• THE MOSDEF SURVEY: EXCITATION PROPERTIES OF z ∼ 2.3 STAR-FORMING GALAXIES (2014, methodology): “Photoionization models (Ferland et al. 1998; Kewley & Dopita 2002; Dopita et al. 2013) tuned to match the distributions of local galaxies in these diagnostic diagrams have been used to translate observed sets of emission lines into physical quantities such as oxygen abundance, ionization parameter…”
• GASP. I. Gas Stripping Phenomena in Galaxies with MUSE (2017, methodology): “The q parameter is defined by Dopita et al. (2013) as the ratio between the number of ionizing 15 http://fpavogt.github.io/pyqz photons per unit area per second and the gas particle number density.16 The code interpolates a finite set of diagnostic lineratio grids computed with the MAPPINGS code to…”
• Binary Population and Spectral Synthesis Version 2.1: Construction, Observational Verification, and New Results (2017, methodology): “…gas screen within the source galaxy is beyond the scope of BPASS itself, but can be modelled in detail using a radiative transfer code such as CLOUDY (Ferland et al. 1998) or MAPPINGS (see Dopita et al. 2013, and references therein) to assess the contribution of nebular continuum and line emission.”
• THE UNIVERSAL RELATION OF GALACTIC CHEMICAL EVOLUTION: THE ORIGIN OF THE MASS–METALLICITY RELATION (2014, background): “However, longstanding discrepancies between various metallicity diagnostics remain unresolved (e.g., Kudritzki et al. 2008; Bresolin et al. 2009; Kudritzki et al. 2012; Nicholls et al. 2012; Dopita et al. 2013).”
• Nuclear activity versus star formation: emission-line diagnostics at ultraviolet and optical wavelengths (2015, methodology): “…from H ii regions and AGN often rely on the predictions of standard photoionization codes, such as MAPPINGS (Sutherland & Dopita 1993; Allen et al. 2008; Dopita et al. 2013) and CLOUDY (Ferland 1993; Ferland et al. 1998, 2013), which have both undergone regular updates over the past decades.”
• New fully empirical calibrations of strong-line metallicity indicators in star forming galaxies (2016, background): “Moreover, we are here considering the simple case of Maxwell-Boltzmann distributed electrons, while recent studies suggested that kdistributions could better represent the behavior of free electrons inside single Hii regions (Nicholls et al. 2012, 2013; Dopita et al. 2013).”