Temperature Bias and the Primordial Helium Abundance Determination

Peimbert, Antonio; Peimbert, M.; Luridiana, V.

doi:10.1086/324601

Cited by 147 publications

(262 citation statements)

References 44 publications

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“…Liu et al (2006) report that for most galactic PNe, ADFs are in the range of 1.6 to 3. Likewise, Peimbert et al (1995a) determined ADFs for many galactic PNe and computed similar ADF values. Therefore we applied an ADF = 2 to the PN abundance determinations from CELs to derive a value for recombination lines.…”

Section: Observational Constraintsmentioning

confidence: 89%

Planetary nebulae as observational constraints in chemical evolution models for NGC 6822

Hernández-Martínez

Carigi

Peña

et al. 2011

A&A

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Aims. Chemical evolution models are useful for understanding the formation and evolution of stars and galaxies. Model predictions will be more robust when more observational constraints are used. We present chemical evolution models for the dwarf irregular galaxy NGC 6822 using chemical abundances of old and young planetary nebulae (PNe) and H ii regions as observational constraints. We use two sets of chemical abundances, one derived from collisionally excited lines (CELs) and one from recombination lines (RLs). We use our models as a tool to distinguish between both procedures for abundance determinations. Methods. In our chemical evolution code the chemical contribution of low and intermediate mass stars is time-delayed, while for the massive stars the chemical contribution follows the instantaneous recycling approximation. Our models have two main free parameters: the mass-loss rate of a well-mixed outflow and the upper mass limit, M up , of the initial mass function (IMF). To reproduce the gaseous mass and the present-day O/H value we need to vary the outflow rate and the M up value. Results. We calculate two models with different M up values that reproduce the constraints adequately. The abundances of old PNe agree with our models and support the star-formation history derived independently from photometric data. Both require an early wellmixed wind, lasting 5.3 Gyr, to reproduce the observed gaseous mass in the galaxy. In addition, by assuming a fraction of binaries producing SNIa of 1%, the models fit the Fe/H abundance ratio as derived from A supergiants. The first model (M4C), which assumes M up = 40 M , fits within errors smaller than 2σ the O/H, Ne/H, S/H, Ar/H and Cl/H abundances obtained from CELs for old and young PNe and H ii regions. The second model (M1R), which adopts M up = 80 M , reproduces within 2σ errors the O/H, C/H, Ne/H and S/H abundances adopted from RLs. Both models reproduce the increase of the O, Ne, S, and Ar elements during the last 6 Gyr. We are not able to match the observed N/O ratios in either case, which suggests that the N yields of LIMS need to be improved. Model M1R does not provide a good fit to the Cl/H and Ar/H ratios, because the SN yields of those elements for m > 40 M are not adequate and need to be improved (two sets of yields were tried). From these results we are unable to conclude which set of abundances (the one from CELs or the one from RLS) represents the real abundances in the ISM better. We discuss the predicted ΔY/ΔO values, finding that the value from model M1R agrees better with data for other galaxies from the literature than the value from model M4C.

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Section: Observational Constraintsmentioning

confidence: 89%

Planetary nebulae as observational constraints in chemical evolution models for NGC 6822

Hernández-Martínez

Carigi

Peña

et al. 2011

A&A

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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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“…As one can see, thel − -catalyzed process significantly changes the upper bound; for mτ R = #4 For more detailed discussion, see [12,18]. #5 See also recent value of Y p reported in [21] where the authors adopted larger errors (0.0028) than that of [20]. 100 GeV, for example, the very stringent constraint is obtained when the gravitino mass is larger than O(0.1 GeV), which corresponds to τl > ∼ O(10 3 sec).…”

mentioning

confidence: 99%

Big-bang nucleosynthesis with long-lived charged slepton

2007

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We consider constraints on long-lived charged scalar leptonsl ± in supersymmetric models, where gravitino is the lightest superparticle. We study the decay and hadronization processes ofl ± . We also take into account the significant enhancement of 6 Li production due to the formation of the bound-state ( 4 Hel − ); for this purpose, we use the reaction rate given by the most recent calculation based on coupled-channel method.

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Temperature Bias and the Primordial Helium Abundance Determination

Cited by 147 publications

References 44 publications

Planetary nebulae as observational constraints in chemical evolution models for NGC 6822

Planetary nebulae as observational constraints in chemical evolution models for NGC 6822

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

Big-bang nucleosynthesis with long-lived charged slepton

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