The chemistry of planetary nebulae and HII regions in the dwarf galaxies Sextans A and B from deep VLT spectra

Magrini, L.; Leisy, P.; Corradi, R. L. M.; Perinotto, M.; Mampaso, A.; Vílchez, J. M.

doi:10.1051/0004-6361:20052973

Cited by 51 publications

(67 citation statements)

References 46 publications

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“…1 (Lee et al 2006) and Sextans B (Kniazev et al 2005;Magrini et al 2005). The face value of the average O/H is also consistent with those found by previous studies of IC10 by Hodge & Lee (1990) and Richer et al (2001).…”

Section: Results-i: Ic10's Enrichment Is Non-homogeneously Distributedsupporting

confidence: 91%

The chemical history of the nearest starburst galaxy – IC10

Gonçalves¹,

Magrini²

2009

Proc. IAU

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Abstract. The irregular dwarf galaxy IC10 is located within the Local Group (LG) at a distance of 750 kpc. Although several studies have revealed the existence of stellar populations with a broad range of ages, its star formation history (SFH) and age-metallicity (AM) relationship remain quite unknown. In this contribution we present our spectroscopic investigation of 15 H ii regions, 9 planetary nebulae (PNe) and 1 symbiotic star -so far the farthest known symbiotic binary. Our main goal is to reconstruct the SFH of IC10 and to constrain its AM relationship using young and intermediate-age stars. The direct availability of the electron temperature in our emission-line spectra allows an accurate determination of the IC10 metallicity map at two different epochs. We find a non-homogeneous distribution of metals at both epochs, but similar average abundances for the two analyzed populations. The derived AM relationship shows a little global enrichment, which is interpreted as due to the loss of metals by supernovae winds and to differential gas outflows. Our results bring strong observational constraints to the chemical enrichment history of IC10, the formation of dwarf irregular galaxies and the evolution of the LG as well.

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Section: Results-i: Ic10's Enrichment Is Non-homogeneously Distributedsupporting

confidence: 91%

The chemical history of the nearest starburst galaxy – IC10

Gonçalves¹,

Magrini²

2009

Proc. IAU

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“…For instance, in some very metal poor galaxies it has been found that oxygen abundances of PNe (and apparently also Ne) are higher than the average value of H II regions. Such is the case in the only PN known in Sextans A (Kniazev et al 2005;Magrini et al 2005), in the 8 PNe studied in NGC 3109 by Peña et al (2007), in a large fraction of PNe in the SMC and in a small but significant fraction in the LMC (Leisy & Dennefeld 2006 (Hernández-Martínez et al 2009, in preparation), we will present a more detailed grid of models and a deeper discussion on this subject.…”

Section: Introductionmentioning

confidence: 98%

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

Hernández-Martínez

Peña²,

Carigi

et al. 2009

A&A

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Aims. We aim to derive the chemical behavior of a significant sample of PNe and HII regions in the irregular galaxy NGC 6822. The selected objects are distributed in different zones of the galaxy. Our purpose is to obtain the chemical abundances of the present interstellar medium (ISM), represented by H ii regions, and the corresponding values at the time of formation of PNe. With these data the chemical homogeneity of NGC 6822 were tested and the abundance pattern given by H ii regions and PNe used as an observational constraint for computing chemical evolution models to infer the chemical history of NGC 6822.Methods. Due to the faintness of PNe and H ii regions in NGC 6822, to gather spectroscopic data with large telescopes is necessary.We obtained a well suited sample of spectra by employing VLT-FORS 2 and Gemini-GMOS spectrographs. Ionic and total abundances were calculated for the objects where electron temperatures could determined through the detection of [O iii] λ4363 or/and [N ii] λ5755 lines. A "simple" chemical evolution model was developed and the observed data were used to compute a model for NGC 6822 in order to infer a preliminary chemical history in this galaxy.Results. Confident determinations of He, O, N, Ne, S and Ar abundances were derived for a sample of 11 PNe and one H ii region. We confirm that the present ISM is chemically homogeneous, at least in the central 2 kpc of the galaxy, showing a value 12 + log O/H = 8.06 ± 0.04. From the abundance pattern of PNe, we identified two populations: a group of young PNe with abundances similar to H ii regions and a group of older objects with abundances a factor of two lower. A pair of extreme Type I PNe were found. No third dredge-up O enrichement was detected in PNe of this galaxy. The abundance determinations allow us to discuss the chemical behavior of the present and past ISM in NGC 6822. Our preliminary chemical evolution model predicts that an important gas-mass loss occurred during the first 5.3 Gyr, that no star higher than 40 M was formed, and that 1% of all 3-15 M stars became binary system progenitors of SNIa.

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“…The present work is part of our study of the structure and evolution of Local Group and nearby galaxies through the spectroscopy of their emission-line populations (see, e.g., Magrini et al 2005;Gonçalves et al 2007;Magrini & Gonçalves 2009;Gonçalves et al 2012Gonçalves et al , 2014Stanghellini et al 2015). In this framework, we have carried on a deep spectroscopic campaign with the multi-object spectrograph GMOS@Gemini-South telescope of the strong-line emitters of NGC 55, as illustrated in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

NGC 55: a disc galaxy with flat abundance gradients

Magrini

Gonçalves

Vajgel

2016

Mon. Not. R. Astron. Soc.

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We present new spectroscopic observations obtained with GMOS@Gemini-S of a sample of 25 H ii regions located in NGC 55, a late-type galaxy in the nearby Sculptor group. We derive physical conditions and chemical composition through the T e -method for 18 H ii regions, and strong-line abundances for 22 H ii regions. We provide abundances of He, O, N, Ne, S, Ar, finding a substantially homogenous composition in the ionised gas of the disc of NGC 55, with no trace of radial gradients. The oxygen abundances, both derived with T e -and strong-line methods, have similar mean values and similarly small dispersions: 12+log(O/H)=8.13±0.18 dex with the former and 12+log(O/H)=8.17±0.13 dex with the latter. The average metallicities and the flat gradients agree with previous studies of smaller samples of H ii regions and there is a qualitative agreement with the blue supergiant radial gradient as well. We investigate the origin of such flat gradients comparing NGC 55 with NGC 300, its companion galaxy, which is also twin of NGC 55 in terms of mass and luminosity. We suggest that the differences in the metal distributions in the two galaxies might be related to the differences in their K-band surface density profile. The flatter profile of NGC 55 probably causes in this galaxy higher infall/outflow rates than in similar galaxies. This likely provokes a strong mixing of gas and a re-distribution of metals.

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The chemistry of planetary nebulae and HII regions in the dwarf galaxies Sextans A and B from deep VLT spectra

Cited by 51 publications

References 46 publications

The chemical history of the nearest starburst galaxy – IC10

The chemical history of the nearest starburst galaxy – IC10

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

NGC 55: a disc galaxy with flat abundance gradients

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