The Progenitors of Planetary Nebulae in Dwarf Irregular Galaxies

Richer, M. G.; McCall, Marshall L.

doi:10.1086/511410

Cited by 31 publications

(56 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In our sample of 11 PN candidates observed with GTC, we found that the He  λ4686 emission line is present (and measurable) Richer & McCall (2007), and the six objects observed with GTC and confirmed as PNe in this work, we find that 19 of the 26 PN candidates reported by are true PNe, and the others are highly probable PNe, thus indicating that the criteria for selecting PN candidates in external galaxies proposed by these authors are very good. However, as we see in the discussion, these criteria, which were designed to mainly select high-luminosity ([O ]λ5007) PNe (useful for building the planetary nebula luminosity function, PNLF), lead to ignore a number of PNe, in particular those with low excitation and low [O ] λ5007 flux.…”

Section: The True Nature Of Objects Observed With Gtcsupporting

confidence: 65%

“…In the case of PNe, the central stars are very faint, and no underlying absorption is expected to affect the nebular lines. An additional object observed, but not included in Table A Richer & McCall (2007), from observations with the Canada-France-Hawaii (CFH) telescope and the MultiObject Spectrograph MOS, for PN 17 and PN 20, and data published by Peimbert et al (2005) for the H  regions H V and H X: all were retrieved and physical conditions and chemical abundances recalculated, following the same procedure as for our GTC data to have a consistent data set of abundances.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Section: The True Nature Of Objects Observed With Gtcsupporting

confidence: 65%

Section: Observations and Data Reductionmentioning

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

show abstract

“…Richer & McCall (2007) obtained spectroscopic data of a sample of seven PNe. They reported that PNe in NGC 6822 have oxygen and neon abundances very similar to those in the H ii regions.…”

Section: Introductionmentioning

confidence: 99%

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

Hernández-Martínez

Peña²,

Carigi

et al. 2009

A&A

View full text Add to dashboard Cite

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.

show abstract

“…Ford et al (2002) found 7 candidate PNe and more recently Leisy et al (2005) have reported several new PN candidates, increasing the total sample to 17, most of them located in the central zone. An additional PN was found by Richer & McCall (2007). In the chemical context NGC 6822 is a metal-poor galaxy, with an interstellar medium (ISM) abundance of about 0.2 Z (e.g., Lee et al 2006;Richer & McCall 2007).…”

Section: Introductionmentioning

confidence: 99%

“…An additional PN was found by Richer & McCall (2007). In the chemical context NGC 6822 is a metal-poor galaxy, with an interstellar medium (ISM) abundance of about 0.2 Z (e.g., Lee et al 2006;Richer & McCall 2007). Spectroscopic studies of some emission line objects have been performed by Killen & Dufour (1982), Richer & McCall (1995, Peimbert et al 2005; and others.…”

Section: Introductionmentioning

confidence: 99%

Emission line objects in NGC 6822. New planetary nebula candidates

Hernández-Martínez

Peña

2008

A&A

View full text Add to dashboard Cite

Aims. Images obtained with the CTIO 4-m telescope and the MOSAIC-2 wide field camera in [O iii] 5007 and Hα on-band and off-band filters are analyzed to search for emission line objects in the dwarf galaxy NGC 6822. In particular we search for planetary nebula (PN) candidates. In addition, imaging and spectroscopy of a sub-sample of objects obtained with the ESO VLT and FORS 2 spectrograph are used to calibrate the MOSAIC imaging. Methods. In the continuum-subtracted images, a large number of line emission regions were detected, for which we measured instrumental magnitudes in all the filters. The [O iii] 5007 and Hα + [N ii] magnitudes were calibrated with the spectroscopy.Results. Based upon some criteria to distinguish between PNe and compact HII regions, we have found 26 PN candidates, increasing the known sample by 8 objects. Also we detected a number of compact HII regions and about 20 stellar-like objects emitting in Hα.For all the objects we present coordinates, instrumental magnitudes and nebular [O iii] and Hα + [N ii] fluxes. The observed luminosity function for the PN [O iii] 5007 magnitudes (PNLF) and the cumulative PNLF were calculated. We confirm that the PNLF presents a dip similar to the one detected for the Small Magellanic Cloud at 2.5 mag below the maximum. The cumulative PNLF returns a value M 5007 = −3.71 +0.21−0.42 for the peak absolute magnitude of the PNLF which is faint (but within uncertainties) compared to the value expected for galaxies with a metallicity similar to that of NGC 6822. From our best fit to the observed PNLF we obtained a rough estimate of the distance modulus m − M = 23.64 +0.23−0.43 mag, which agrees within uncertainties with recent values from Cepheid stars reported in the literature. Also the number of PNe in the brightest 0.5 mag, normalized to the galactic bolometric luminosity, was estimated to be α 0.5 ∼ (3.8 +0.90 −0.71 ) E-9. This number is similar to the values derived for galaxies with recent star formation and small galaxies (M B fainter than −18 mag) and larger than the values for early-type galaxies.

show abstract

The Progenitors of Planetary Nebulae in Dwarf Irregular Galaxies

Cited by 31 publications

References 54 publications

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

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

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

Emission line objects in NGC 6822. New planetary nebula candidates

Contact Info

Product

Resources

About