Optical Recombination Lines of Heavy Elements in Giant Extragalactic H<scp>ii</scp>Regions

Esteban, C.; Peimbert, M.; Torres-Peimbert, S.; Rodríguez, Mónica

doi:10.1086/344104

Cited by 111 publications

(178 citation statements)

References 81 publications

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“…The peculiar position of NGC 2363 is indicated in Figure 6 because it will be discussed later. The figure shows the wellknown C/O vs. O/H correlation found in previous works by, for example, Garnett et al (1995Garnett et al ( , 1999) from observations of CELs or Esteban et al (2002Esteban et al ( , 2009) from observations of RLs. Figure 6 includes the time evolution of the abundances predicted by the chemical evolution models of the Milky Way disc presented by Esteban et al (2013).…”

Section: The C/o Vs O/h Relationsupporting

confidence: 59%

Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution★

Esteban

García‐Rojas

Carigi³

et al. 2014

Monthly Notices of the Royal Astronomical Society

111

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We present deep echelle spectrophotometry of the brightest emission-line knots of the star-forming galaxies He 2−10, Mkn 1271, NGC 3125, NGC 5408, POX 4, SDSS J1253−0312, Tol 1457−262, Tol 1924−416 and the H ii region Hubble V in the Local Group dwarf irregular galaxy NGC 6822. The data have been taken with the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the 3100-10420Å range. We determine electron densities and temperatures of the ionized gas from several emission-line intensity ratios for all the objects. We derive the ionic abundances of C 2+ and/or O 2+ from faint pure recombination lines (RLs) in several of the objects, permitting to derive their C/H and C/O ratios. We have explored the chemical evolution at low metallicities analysing the C/O vs. O/H, C/O vs. N/O and C/N vs. O/H relations for Galactic and extragalactic H ii regions and comparing with results for halo stars and DLAs. We find that H ii regions in star-forming dwarf galaxies occupy a different locus in the C/O vs. O/H diagram than those belonging to the inner discs of spiral galaxies, indicating their different chemical evolution histories, and that the bulk of C in the most metal-poor extragalactic H ii regions should have the same origin than in halo stars. The comparison between the C/O ratios in H ii regions and in stars of the Galactic thick and thin discs seems to give arguments to support the merging scenario for the origin of the Galactic thick disc. Finally, we find an apparent coupling between C and N enrichment at the usual metallicities determined for H ii regions and that this coupling breaks in very low-metallicity objects.

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Section: The C/o Vs O/h Relationsupporting

confidence: 59%

Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution★

Esteban

García‐Rojas

Carigi³

et al. 2014

Monthly Notices of the Royal Astronomical Society

111

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“…1b smaller symbols correspond to models for which [N ] λ5755/Hβ is smaller than 10 −4 . This is the flux limit attained by Esteban et al (2002) with 3 hours of integration on a 4 m telscope for the brightest H  region in M 33.…”

Section: The Biasesmentioning

confidence: 74%

“…Recombination lines have also been detected in a few H  regions (e.g. Peimbert et al 1993;Esteban et al 1998Esteban et al , 1999Esteban et al , 2002Tsamis et al 2003b;Garcia-Rojas et al 2004). Here again they lead to higher abundances than collisionally excited lines, although not to the same extreme as in planetary nebulae.…”

Section: Derive Abundances From Pure Recombination Linesmentioning

confidence: 99%

Biases in abundance derivations for metal-rich nebulae

Stasińska¹

2005

A&A

169

211

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Abstract. Using ab-initio photoionization models of giant H  regions, we test methods for abundance determinations based on a direct measurement of the electron temperature, now possible even for moderate to high-metallicity objects. We find that, for metallicities larger than solar, the computed abundances deviate systematically from the real ones, generally by larger amounts for more metal-rich H  regions. We discuss the reasons for this, and present diagrams allowing the reader to better understand the various factors coming into play. We briefly discuss less classical methods to derive abundances in metal-rich H  regions.In particular, we comment on the interest of the oxygen and carbon recombination lines. We also show that, contrary to the case of giant H  regions, the physical conditions in bright extragalactic planetary nebulae are such that their chemical composition can be accurately derived even at high metallicities. Thus, extragalactic planetary nebulae are promising potential probes of the metallicity of the interstellar medium in the internal parts of spiral galaxies as well as in metal-rich elliptical galaxies.

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“…To obtain a consistent and, possibly, more correct set of data for the hydrogen distributions, the conversion from CO flux to H 2 surface density has been redone using the oxygen-dependent calibration by Wilson (1995), assuming the O/H-gradient derived by Esteban et al (2002Esteban et al ( , 2005.…”

Section: Abundance Datamentioning

confidence: 99%

The origin of carbon: Low-mass stars and an evolving, initially top-heavy IMF?

Mattsson

2010

A&A

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Multi-zone chemical evolution models (CEMs), differing in the nucleosynthesis prescriptions (yields) and prescriptions of star formation, have been computed for the Milky Way. All models fit the observed O/H and Fe/H gradients well and reproduce the main characteristics of the gas distribution, but they are also designed to do so. For the C/H gradient the results are inconclusive with regards to yields and star formation. The C/Fe and O/Fe vs. Fe/H, as well as C/O vs. O/H trends predicted by the models for the solar neighbourhood zone were compared with stellar abundances from the literature. For O/Fe vs. Fe/H all models fit the data, but for C/O vs. O/H, only models with increased carbon yields for zero-metallicity stars or an evolving initial mass function provide good fits. Furthermore, a steep star formation threshold in the disc can be ruled out since it predicts a steep fall-off in all abundance gradients beyond a certain galactocentric distance (∼13 kpc) and cannot explain the possible flattening of the C/H and Fe/H gradients in the outer disc seen in observations. Since in the best-fit models the enrichment scenario is such that carbon is primarily produced in low-mass stars, it is suggested that in every environment where the peak of star formation happened a few Gyr back in time, winds of carbon-stars are responsible for most of the carbon enrichment. However, a significant contribution by zero-metallicity stars, especially at very early stages, and by winds of high-mass stars, which are increasing in strength with metallicity, cannot be ruled out by the CEMs presented here. In the solar neighbourhood, as much as 80%, or as little as 40% of the carbon may have been injected to the interstellar medium by low-and intermediate-mass stars. The stellar origin of carbon remains an open question, although production in low-and intermediate-mass stars appears to be the simplest explanation of observed carbon abundance trends.

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Optical Recombination Lines of Heavy Elements in Giant Extragalactic HiiRegions

Cited by 111 publications

References 81 publications

Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution★

Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution★

Biases in abundance derivations for metal-rich nebulae

The origin of carbon: Low-mass stars and an evolving, initially top-heavy IMF?

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