Chemical and Photometric Evolution of the Local Group Galaxy NGC 6822 in a Cosmological Context

Carigi, Leticia; Colín, Pedro; Peimbert, M.

doi:10.1086/503664

Cited by 20 publications

(29 citation statements)

References 72 publications

(116 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is found in several works on chemical evolution models (e.g., Chiappini et al 2003;Carigi et al 2005;Mollá et al 2006;Romano et al 2010;Kobayashi et al 2011). The prediction of our model is 7.4σ higher than the value observed in H ii regions, therefore we consider that the N yields adopted for LIMS are in general overestimated the models.…”

Section: Our Best Model For Abundances From Celsmentioning

confidence: 55%

“…Therefore, the accretion history is a better approximation for this galaxy than simple parametric equations. Carigi et al (2006) described two families of cosmological models for the increase of baryonic mass: S (smallinfall) and L (large-infall). We have chosen the L-models because they better adjust the observational constrains presented by CCP06 (the S-models predict higher enrichment in O/H and C/H than the L-models).…”

Section: Assumptions Of the Chemical Evolution Modelsmentioning

confidence: 99%

“…These authors demonstrated that the accumulated thermal energy is much higher than the present binding energy, therefore much of that energy should have been thrown away through galactic winds. Carigi et al (2006) gave several arguments to explain why the outflows that are needed to eliminate this excess in thermal energy likely occurred in the first few billion years of evolution (t < 5 Gyr) when the galaxy was less bounded (note that the binding energy of a galaxy is also a function of time and in the hierarchical cosmology, the potential wells of galaxies for a given present mass were shallower in the past). The gas outflow should have stopped when the binding and thermal energy came to an equilibrium.…”

Section: The Computed Modelsmentioning

confidence: 99%

See 2 more Smart Citations

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

Hernández-Martínez

Carigi

Peña

et al. 2011

A&A

View full text Add to dashboard Cite

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.

show abstract

Section: Our Best Model For Abundances From Celsmentioning

confidence: 55%

Section: Assumptions Of the Chemical Evolution Modelsmentioning

confidence: 99%

Section: The Computed Modelsmentioning

confidence: 99%

See 1 more Smart Citation

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

Hernández-Martínez

Carigi

Peña

et al. 2011

A&A

View full text Add to dashboard Cite

show abstract

“…In both the SMC and NGC 6822 the PNLF dip is ∼2.5 mag fainter than the brightest PNe. Carigi et al (2006) and Hernández-Martínez et al (2009) presented a study of the star formation history of NGC 6822, showing evidence of two important star forming episodes, which could be related to a dip seen in the PNLF (see Sect. 6).…”

Section: Introductionmentioning

confidence: 98%

A two-mode planetary nebula luminosity function

Rodríguez-González

Hernández-Martínez

Esquivel

et al. 2015

A&A

View full text Add to dashboard Cite

Context. We propose a new planetary nebula luminosity function (PNLF) that includes two populations in the distribution. Our PNLF is a direct extension of the canonical function proposed by Jacoby et al. (1987), in order to avoid problems related with the histogram construction, it is cast in terms of cumulative functions. Aims. We are interested in recovering the shape of the faint part of the PNLF in a consistent manner, for galaxies with and without a dip in their PNLFs. Methods. The parameters for the two-mode PNLF are obtained with a genetic algorithm, which obtains a best fit to the PNLF varying all of the parameters simultaneously in a broad parameter space. Results. We explore a sample of nine galaxies with various Hubble types and construct their PNLF. All of the irregular galaxies, except one, are found to be consistent with a two-mode population, while the situation is less clear for ellipticals and spirals.For the case of NGC 6822, we show that the two-mode PNLF is consistent with previous studies of the star formation history within that galaxy. Our results support two episodes of star formation, in which the second episode is significantly stronger.

show abstract

“…By studying abundances in H  regions, they also found that the ISM located in the 2 kpc around the centre is chemically homogeneous, showing 12+log (O/H) = 8.06 ± 0.04. Carigi et al (2006) constructed chemical evolution models that fit the photometric properties of NGC 6822 computed by Wyder (2001Wyder ( , 2003 and derived a robust star formation history (SFH) for this galaxy. Detailed galactic chemical evolution models were computed by , 2011 using PNe and H  region abundances as constraints with no conclusive results.…”

Section: Introductionmentioning

confidence: 99%

The planetary nebulae and H II regions in NGC 6822 revisited. Clues to AGB nucleosynthesis

García‐Rojas

Peña

Flores-Durán

et al. 2016

A&A

View full text Add to dashboard Cite

Aims. The chemical behaviour of an ample sample of planetary nebulae (PNe) in NGC 6822 is analysed.Methods. Spectrophotometric data of 11 PNe and two H  regions were obtained with the OSIRIS spectrograph attached to the Gran Telescopio Canarias. Data for other 13 PNe and three H  regions were retrieved from the literature. Physical conditions and chemical abundances of O, N, Ne, Ar, and S were derived in a consistent way for 19 PNe and 4 H  regions.Results. Abundances in the PNe sample are widely distributed showing 12 + log (O/H) from 7.4 to 8.2 and 12 + log (Ar/H) from 4.97 to 5.80. Two groups of PNe can be differentiated: one old with low metallicity (12 + log (O/H) < 8.0 and 12 + log (Ar/H) < 5.7) and another younger one with metallicities similar to the values for H  regions. The old objects are distributed in a larger volume than the young ones. An important fraction of PNe (over 30%) was found to be highly N-rich (Peimbert Type I PNe). Such PNe occur at any metallicity. In addition, about 60% of the sample presents high ionization (He ++ /He ≥ 0.1), possessing a central star with effective temperature higher than 100 000 K. Possible biases in the sample are discussed. From comparison with stellar evolution models by Karakas (2010) and Fishlock et al. (2014) of the observed N/O abundance ratios, our PNe should have had initial masses that are lower than 4 M , although if the comparison is made with Ne vs. O abundances, the initial masses should have been lower than 2 M . It appears that these models of stars of 2−3 M are producing too much 22 Ne in the stellar surface at the end of the AGB. On the other hand, the comparison with another set of stellar evolution models with a different treatment of convection and on the assumptions about the overshoot of the convective core during the core H-burning phase, provided there is reasonable agreement between the observed and predicted N/O and Ne/H ratios if initial masses of more massive stars are about 4 M .

show abstract

Chemical and Photometric Evolution of the Local Group Galaxy NGC 6822 in a Cosmological Context

Cited by 20 publications

References 72 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

A two-mode planetary nebula luminosity function

The planetary nebulae and H II regions in NGC 6822 revisited. Clues to AGB nucleosynthesis

Contact Info

Product

Resources

About