Measuring Global Galaxy Metallicities Using Emission-Line Equivalent Widths

By H. Kobulnicky, A. Phillips. 2003

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We develop a prescription for estimating the interstellar medium oxygen abundances of distant star-forming galaxies using the ratio EW R23 formed from the equivalent widths of the [O II] λ3727, [O III] λλ4959, 5007, and Hβ nebular emission lines. This EW R23 approach is essentially identical to the widely used R23 method of Pagel and coworkers. Using data from three spectroscopic surveys of nearby galaxies, we conclude that the emission-line equivalent-width ratios are a good substitute for emission-line flux ratios in galaxies with active star formation. The rms dispersion between EW R23 and the reddening-corrected R23 values is σ(log R23) ≤ 0.08 dex. This dispersion is comparable to the emission-line measurement uncertainties for distant galaxies in many spectroscopic galaxy surveys, and is somewhat smaller than the uncertainties of σ(O/H) ~ 0.15 dex inherent in strong-line metallicity calibrations. Because equivalent-width ratios are partially insensitive to interstellar reddening effects, emission-line equivalent-width ratios should be superior to flux ratios when reddening corrections are not available. The EW R23 method presented here is likely to be most useful for statistically estimating the mean metallicities for large samples of galaxies to trace their chemical properties as a function of redshift or environment. The approach developed here is used in a companion paper by Kobulnicky and coworkers to measure the metallicities of star-forming galaxies at z = 0.2-0.8 in the Deep Extragalactic Evolutionary Probe spectroscopic survey of the Groth strip.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/13d2923920adda468013186a94cf723cf5c5afb6

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Citations in the corpus

Optical Star Formation Rate Indicators (2005, unknown): “One widely used abundance indicator is the R23 parameter (Pagel et al. 1978), given by R23 ½O ii k3727þ ½O iii kk4959; 5007 H k4861 ; ð6Þ where each emission line must be corrected for dust reddening (but see Kobulnicky & Phillips 2003).”
Intergalactic Photon Spectra from the Far-IR to the UV Lyman Limit for 0 < z < 6 and the Optical Depth of the Universe to High-Energy Gamma Rays (2005, methodology): “Following our previous work, we use the quantitative measurements of these trends determined by Spinoglio et al. (1995) and Spinolgio , Andreani and Malkan (2002).”
Starburst and AGN activity in ultraluminous infrared galaxies (2003, methodology): “Optical and near-IR fluxes were taken from the APM and 2MASS databases and also from Carico et al (1988) & Spinoglio et al (1995).”
Infrared Power-Law Galaxies in the Chandra Deep Field-South: Active Galactic Nuclei and Ultraluminous Infrared Galaxies (2006, background): “…IR (8–1000 m) luminosity cannot be measured directly for most of the IR power-law galaxies in our sample, a number of works (e.g., Rush et al. 1993; Spinoglio et al. 1995; Takeuchi et al. 2005; Pérez-González et al. 2005) have shown that the 12 m luminosity is a good proxy for it for AGNs,…”
Resolving the mid-infrared cores of local Seyferts (2009, background): “…coverage and resolving power have changed the situation steadily over the past two decades (e.g., Sanders et al. 1989; Mulchaey et al. 1994; Spinoglio et al. 1995; Krabbe et al. 2001; Lutz et al. 2004; Buchanan et al. 2006; Ramos Almeida et al. 2008; Mushotzky et al. 2008; Meléndez et al.…”
A Survey of Kiloparsec-Scale Radio Outflows in Radio-Quiet Active Galactic Nuclei (2006, background): “Spinoglio and collaborators have argued that L12 scales almost linearly with the bolometric luminosity of the host galaxy, including the contribution of the AGN (Spinoglio & Malkan 1989; Spinoglio et al. 1995).”
Infrared Luminosity Functions from the Chandra Deep Field-South: The Spitzer View on the History of Dusty Star Formation at 0 ≲ z ≲ 1* (2005, methodology): “Using the 12µm IRAS galaxy sample, Spinoglio et al. (1995) first showed that the relative dust content of galaxies balances their total energetic output between the optical and the farinfrared, leaving a “pivot point” in the MIR where the specific luminosity linearly scales with the bolometric one.”
Optical Spectroscopy and X-Ray Detections of a Sample of Quasars and Active Galactic Nuclei Selected in the Mid-Infrared from Two Spitzer Space Telescope Wide-Area Surveys (2006, background): “Mid-infrared selection of AGN is effective because dust heated by the AGN forms a “calorimeter”, whose luminosity is not as strongly affected by obscuration as that in most other wavelength bands (except the radio) (e.g. Spinoglio et al. 1995; Meisenheimer et al. 2001; Ogle et al. 2006).”
An XMM–Newton spectral survey of 12 μm selected galaxies – I. X-ray data (2010, background): “Spinoglio & Malkan (1989) showed that a wide variety of AGN types emit a constant fraction of their bolometric luminosities at this wavelength, and furthermore shown to be true for star forming galaxies as well by Spinoglio et al. (1995).”
The reversal of the star formation-density relation in the distant universe (2007, background): “While it has been demonstrated that the mid infrared is a robust tracer (at the 40 % rms level) of the total IR luminosity (L IR=L[8–1000µm]) in the present-day universe (Chary & Elbaz 2001, Spinoglio et al. 1995), it is to be expected that te Fig.”
Toward an Understanding of the Rapid Decline of the Cosmic Star Formation Rate (2005, background): “Estimating Total IR Luminosity Local IR-luminous galaxies show a tight correlation between rest-frame 12–15 m luminosity and total IR luminosity (e.g., Spinoglio et al. 1995; Chary & Elbaz 2001; Roussel et al. 2001; Papovich & Bell 2002), with a scatter of 0.15 dex.”