Chemical behavior of the dwarf irregular galaxy NGC6822. Its PN and HII region abundances

Hernández-Martínez, L.; Peña, M.; Carigi, Leticia; García‐Rojas, J.

doi:10.1051/0004-6361/200912476

Cited by 34 publications

(33 citation statements)

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“…(1)) and the evolution of the chemical abundance by mass in the ISM for the element i, X i (t) (Eq. (2)), respectively (Hernández-Martínez 2010).…”

Section: Chemical Evolution Equations With a Delayedmentioning

confidence: 99%

“…This method was modified by Hernández-Martínez (2010) to include numerical infalls, outflows, and star-formation rates. We also increase in this new code the number of chemical elements considered from 5 to 27.…”

Section: Introductionmentioning

confidence: 99%

“…Their chemical evolution models were built to reproduce the present component of the ISM, as given by the chemical abundances of the H ii region HV, determined from recombination lines (RLs). Hernández-Martínez et al (2009) determined abundances from collisionally excited lines (CELs) for 11 PNe and one H ii region. From these data they confirmed the chemical homogeneity of the present component in the ISM and found the presence of two populations of PNe.…”

Section: Introductionmentioning

confidence: 99%

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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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“…(1)) and the evolution of the chemical abundance by mass in the ISM for the element i, X i (t) (Eq. (2)), respectively (Hernández-Martínez 2010).…”

Section: Chemical Evolution Equations With a Delayedmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…This includes evidence for recent star formation in the form of a known population of massive stars, as well as a number of H II regions (Venn et al 2001;de Blok & Walter 2006;Hernández-Martínez et al 2009;Levesque & Massey 2012).…”

Section: Introductionmentioning

confidence: 99%

Red Supergiant Stars as Cosmic Abundance Probes: Kmos Observations in NGC 6822

Patrick

Evans

Davies

et al. 2015

ApJ

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We present near-IR spectroscopy of red supergiant (RSG) stars in NGC 6822, obtained with the new K-band Multi-Object Spectrograph Very Large Telescope, Chile. From comparisons with model spectra in the J-band we determine the metallicity of 11 RSGs, finding a mean value of [Z] = −0.52 ± 0.21, which agrees well with previous abundance studies of young stars and H II regions. We also find an indication for a low-significance abundance gradient within the central 1 kpc. We compare our results with those derived from older stellar populations and investigate the difference using a simple chemical evolution model. By comparing the physical properties determined for RSGs in NGC 6822 with those derived using the same technique in the Galaxy and the Magellanic Clouds, we show that there appears to be no significant temperature variation of RSGs with respect to metallicity, in contrast to recent evolutionary models.

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“…5) but not chemical gradients. In the irregular galaxy NGC 6822 different populations have also been found and in this case these populations do show different dynamics and different chemical composition, although no chemical gradients (Hernández-Martínez et al 2009;Flores-Durán et al 2014;García-Rojas et al 2016).…”

Section: Is There a Relation Between The Kinematicsmentioning

confidence: 88%

Kinematic and chemical study of planetary nebulae and H II regions in NGC 3109

Flores-Durán

Peña

Ruíz

2017

A&A

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Aims. We present high-resolution spectroscopy of a number of planetary nebulae (PNe) and H ii regions distributed along the dwarf irregular galaxy NGC 3109 and compare their kinematical behavior with that of H i data. We aim to determine if there is a kinematical connection among these objects. We also aim to determine the chemical composition of some PNe and H ii regions in this galaxy and discuss it in comparison with stellar evolution models.Methods. Data for eight PNe and one H ii region were obtained with the high-resolution spectrograph Magellan Inamori Kyocera Echelle (MIKE) at Las Campanas Observatory, Chile. Data for three PNe, six compact H ii regions, and nine knots or clumps in extended H ii regions were obtained with the high-resolution spectrograph Manchester Echelle Spectrometer (MES) attached to the 2.1m telescope at the Observatorio Astronómico Nacional, SPM, B.C., Mexico. An additional object was obtained from The SPM Catalogue of Extragalactic Planetary Nebulae. Thus, in total we have high-quality data for nine of the 20 PNe detected in this galaxy, and many H ii regions. In the wavelength calibrated spectra, the heliocentric radial velocities were measured with a precision better than 7.8 km s −1 . Data for blue supergiant stars were collected from the literature to be included in the analysis. The heliocentric radial velocities of the different objects were compared to the velocities of the H i disk at the same position. Physical conditions and ionic abundances of PNe and H ii regions were obtained from the emission lines, and we used recent ionization correction factors to derive the total chemical abundances.Results. From the analysis of radial velocities we found that H ii regions in NGC 3109 share the kinematics of the H i disk at the same projected position with very low dispersion in velocities. Blue supergiant stars and PNe rotate in the same direction as the H i disk but these objects have much larger dispersion; this larger dispersion is possibly because these objects belong to a different population that is located in the central stellar bar reported for this galaxy. From the chemical abundance determinations we demonstrate that PNe are enriched in O and Ne. The average O abundance in H ii regions is 12 + log O/H = 7.74 ± 0.09 and PNe show significantly higher oxygen abundance by 0.43 dex in average. Ne abundance are about three times larger in PNe than in H ii regions. This is a very important result showing that because of the low metallicity in the galaxy, O and Ne in PNe have been enriched by their progenitors in nucleosynthesis processes and brought to the surface during third dredge-up events. Our PN abundances are better reproduced by some nonstandard stellar evolution models for a metallicity of Z = 0.001, similar to the metallicity of H ii regions. Abundances in H ii regions show no metallicity gradient in this galaxy. We discuss a possible connection between the kinematics and chemistry.

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Chemical behavior of the dwarf irregular galaxy NGC6822. Its PN and HII region abundances

Cited by 34 publications

References 50 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

Red Supergiant Stars as Cosmic Abundance Probes: Kmos Observations in NGC 6822

Kinematic and chemical study of planetary nebulae and H II regions in NGC 3109

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