The Chemical Composition of the Small Magellanic Cloud H<scp>ii</scp>Region NGC 346 and the Primordial Helium Abundance

Peimbert, M.; Peimbert, Antonio; Ruíz, M. T.

doi:10.1086/309485

Cited by 181 publications

(255 citation statements)

References 53 publications

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“…The H ii region abundances have been obtained adopting values of t 2 larger than 0.00. Further arguments in favor of t 2 > 0:00 have been presented elsewhere (Peimbert 2002;Peimbert & Peimbert 2002a, 2002b.…”

Section: Ionic Abundances From Collisionally Excited Linesmentioning

confidence: 89%

The Chemical Composition of the 30 Doradus Nebula Derived from Very Large Telescope Echelle Spectrophotometry

Peimbert¹

2003

ApJ

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133

182

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Section: Ionic Abundances From Collisionally Excited Linesmentioning

confidence: 89%

The Chemical Composition of the 30 Doradus Nebula Derived from Very Large Telescope Echelle Spectrophotometry

Peimbert¹

2003

ApJ

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133

182

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“…To derive the He + abundance, we used the effective recombination coefficients of Storey & Hummer (1995) for H i and those computed by Porter et al (2012Porter et al ( , 2013 for He i, whose calculations include corrections for collisional excitation and self-absorption effects. The finally adopted He + /H + ratio for each object has been derived from a maximum likelihood method (MLM, Peimbert et al 2000Peimbert et al , 2002. With this method we obtain the best pair of values of mean He + /H + ratio and temperature fluctuations parameter -t 2 , in this case we designate it as t 2 (He i) -that minimize the χ 2 of the MLM.…”

Section: Ionic Abundances and Abundance Discrepancymentioning

confidence: 99%

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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“…which has been obtained from the value of the primordial helium abundance obtained by Luridiana et al (2003), Y p = 0.2391, and the slope of the He vs. O relationship quoted by Peimbert et al (2000), ΔY/ΔO = 3.5. Dopita et al (2006b) assume for the He abundance a steeper relation given by:…”

Section: The Chemical Composition Meshmentioning

confidence: 99%

On emission-line spectra obtained from evolutionary synthesis models

Villaverde

Cerviño

Luridiana

2010

A&A

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Aims. In this paper we study the influence of the ionizing cluster mass on the emission line spectrum of H ii regions in order to determine the influence of low mass clusters on the integrated emission line spectra of galaxies. Methods. For this purpose, we present a grid of photoionization models that covers metallicities from Z = 0.001 to Z = 0.040, ages from 0.1 to 10 Ma (with a time step of 0.1 Ma), and cluster initial masses from 1 to 10 7 M . The stellar masses follow a Salpeter initial mass function (IMF) in an instantaneous burst mode of star formation. We obtain power-law scale-relations between emission-line luminosities and ionizing cluster masses from the grids and we evaluate the dependences on the ionizing cluster mass for some line luminosities, equivalent widths and line ratios. Results. Power-law scale-relations are shown to be useful tools to obtain robust diagnostics, as examples: (a) Hα/Hβ ratio varies from the usually assumed value of 2.86, these variations imply the existence of a lower limit to the attainable precision in extinction star formation rate indicator for ages older than ∼4.5 Ma. We also show that the ionizing cluster mass dependence explains why empirical calibrations produce more reliable diagnostics of some emission lines than photoionization models grids. Finally, we show preliminary results about the contribution of low mass clusters (M < 10 4 M ) to the integrated emission line spectra of galaxies, which can be as high as 80% for some relevant lines.

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The Chemical Composition of the Small Magellanic Cloud HiiRegion NGC 346 and the Primordial Helium Abundance

Cited by 181 publications

References 53 publications

The Chemical Composition of the 30 Doradus Nebula Derived from Very Large Telescope Echelle Spectrophotometry

The Chemical Composition of the 30 Doradus Nebula Derived from Very Large Telescope Echelle Spectrophotometry

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

On emission-line spectra obtained from evolutionary synthesis models

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