The role of shocks in the determination of empirical abundances for type-I PNe

2018 ◽  
Vol 14 (S343) ◽  
pp. 377-378
Author(s):  
Roberto D. D. Costa ◽  
Paulo J. A. Lago
Keyword(s):  
Planetary Nebulae ◽  
Type I ◽  
Correction Factors ◽  
Chemical Abundances

AbstractWe investigate, in the light of new diagnostic diagrams, the role of shocks in the ionization profile of type-I planetary nebulae, and their relation to the empirical derivation of chemical abundances. We apply our technique to two well-known type-I objects: NGC 2440 and NGC 6302. Our results indicate that shocks play a very important role in the spectra of both nebulae and, since the presence of shocks reinforces the flux of low ionization lines, this artificial reinforcement can lead to incorrect chemical abundances, when they are derived through Ionization Correction Factors, at least for type-I PNe.

scholarly journals Imaging the elusive H-poor gas in planetary nebulae with large abundance discrepancy factors

2016 ◽  
Vol 12 (S323) ◽  
pp. 65-69 ◽  
Author(s):  
Jorge García-Rojas ◽  
Romano L. M. Corradi ◽  
Henri M. J. Boffin ◽  
Hektor Monteiro ◽  
David Jones ◽  
...  
Keyword(s):  
Planetary Nebulae ◽  
Tunable Filter ◽  
Close Binary ◽  
Chemical Abundances ◽  
Dual Nature ◽  
Gas Phases ◽  
Binary Evolution ◽  
The Universe ◽  
Central Stars

AbstractThe discrepancy between abundances computed using optical recombination lines (ORLs) and collisionally excited lines (CELs) is a major, unresolved problem with significant implications for the determination of chemical abundances throughout the Universe. In planetary nebulae (PNe), the most common explanation for the discrepancy is that two different gas phases coexist: a hot component with standard metallicity, and a much colder plasma enhanced in heavy elements. This dual nature is not predicted by mass loss theories, and direct observational support for it is still weak. In this work, we present our recent findings that demonstrate that the largest abundance discrepancies are associated with close binary central stars. OSIRIS-GTC tunable filter imaging of the faint O ii ORLs and MUSE-VLT deep 2D spectrophotometry confirm that O ii ORL emission is more centrally concentrated than that of [Oiii] CELs and, therefore, that the abundance discrepancy may be closely linked to binary evolution.

scholarly journals Helium and Oxygen Abundances in SMC Planetary Nebulae

2000 ◽  
Vol 198 ◽  
pp. 234-235
Author(s):  
R. D. D. Costa ◽  
J. A. de Freitas Pacheco ◽  
T. P. Idiart
Keyword(s):  
Spectroscopic Data ◽  
Planetary Nebulae ◽  
Hii Regions ◽  
Physical Parameters ◽  
Type I ◽  
Chemical Abundances ◽  
High Quality

In this work we report new high quality spectroscopic data for a sample of PNe in the SMC, aiming to derive physical parameters and chemical abundances, in particular to settle the question concerning the oxygen discrepancy found for type I planetaries with respect to stars and HII regions.

scholarly journals A detailed look at chemical abundances in the Magellanic Clouds

2011 ◽  
Vol 7 (S283) ◽  
pp. 502-503
Author(s):  
Richard A. Shaw ◽  
Ting-Hui Lee ◽  
Letizia Stanghellini ◽  
James E. Davies ◽  
D. Anibal García-Hernández ◽  
...  
Keyword(s):  
Direct Methods ◽  
Abundance Ratio ◽  
Type I ◽  
Large Set ◽  
Agb Stars ◽  
Correction Factors ◽  
Chemical Abundances ◽  
Elemental Abundances ◽  
Low Metallicity ◽  
Low Mass

AbstractWe determine elemental abundances of He, N, O, Ne, S, and Ar in Magellanic Cloud planetary nebulae (PNe) using direct methods and a large set of observed ions, minimizing the need for ionization correction factors. In contrast to prior studies, we find a clear separation between Type I and non-Type I PNe in these low-metallicity environments, and no evidence that the O-N nucleosynthesis cycle is active in low-mass progenitors. We find that the S/O abundance ratio is anomalously low compared to H ii regions, confirming the “sulfur anomaly” found for Galactic PNe. We also found that Ne/O is elevated in some cases, raising the possibility that Ne yields in low-mass AGB stars may be enhanced at low metallicity.

scholarly journals Confronting expansion distances of planetary nebulae with Gaia DR2 measurements

2019 ◽  
Vol 625 ◽  
pp. A137 ◽  
Author(s):  
D. Schönberner ◽  
M. Steffen
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Precise Determination ◽  
Asymptotic Giant Branch ◽  
Correction Factors ◽  
Trigonometric Parallaxes ◽  
Formation And Evolution ◽  
Hydrodynamical Simulations ◽  
Good Agreement

Context. Individual distances to planetary nebulae are of the utmost relevance for our understanding of post-asymptotic giant-branch evolution because they allow a precise determination of stellar and nebular properties. Also, objects with individual distances serve as calibrators for the so-called statistical distances based on secondary nebular properties. Aims. With independently known distances, it is possible to check empirically our understanding of the formation and evolution of planetary nebulae as suggested by existing hydrodynamical simulations. Methods. We compared the expansion parallaxes that have recently been determined for a number of planetary nebulae with the trigonometric parallaxes provided by the Gaia Data Release 2. Results. Except for two out of 11 nebulae, we found good agreement between the expansion and the Gaia trigonometric parallaxes without any systematic trend with distance. Therefore, the Gaia measurements also prove that the correction factors necessary to convert proper motions of shocks into Doppler velocities cannot be ignored. Rather, the size of these correction factors and their evolution with time as predicted by 1D hydrodynamical models of planetary nebulae is basically validated. These correction factors are generally greater than unity and are different for the outer shell and the inner bright rim of a planetary nebula. The Gaia measurements also confirm earlier findings that spectroscopic methods often lead to an overestimation of the distance. They also show that even modelling of the entire system of star and nebula by means of sophisticated photoionisation modelling may not always provide reliable results. Conclusions. The Gaia measurements confirm the basic correctness of the present radiation-hydrodynamics models, which predict that both the shell and the rim of a planetary nebula are two independently expanding entities, created and driven by different physical processes, namely thermal pressure (shell) or wind interaction (rim), both of which vary differently with time.

scholarly journals IFU Spectroscopy of Southern Planetary Nebulae V: Low-Ionisation Structures

2017 ◽  
Vol 34 ◽  
Author(s):  
A. Ali ◽  
M. A. Dopita
Keyword(s):  
Emission Line ◽  
Planetary Nebulae ◽  
Central Star ◽  
Chemical Compositions ◽  
Physical Analysis ◽  
Type I ◽  
High Excitation ◽  
Chemical Abundances ◽  
Physical Conditions ◽  
Integral Field Spectroscopy

AbstractIn this fifth paper of the series, we examine the spectroscopy and morphology of four southern Galactic planetary nebulae Hen 2-141, NGC 5307, IC 2553, and PB 6 using new integral field spectroscopy data. The morphologies and ionisation structures of the sample are given as a set of emission-line maps. In addition, the physical conditions, chemical compositions, and kinematical characteristics of these objects are derived. The results show that PB 6 and Hen 2-141 are of very high excitation classes and IC 2553 and NGC 5307 are mid to high excitation objects. The elemental abundances reveal that PB 6 is of Type I, Hen 2-141 and IC 2553 are of Type IIa, and NGC 5307 is of Type IIb/III. The observations unveil the presence of well-defined low-ionisation structures or ‘knots’ in all objects. The diagnostic diagrams reveal that the excitation mechanism of these knots is probably by photoionisation of dense material by the nebular central stars. The physical analysis of six of these knots show no significant differences with their surrounding nebular gas, except their lower electron densities. In spite of the enhancement of the low-ionisation emission lines of these knots, their chemical abundances are nearly comparable to their surrounding nebulae, with the exception of perhaps slightly higher nitrogen abundances in the NGC 5307 knots. The integrated spectrum of IC 2553 reveals that nearly all key lines that have led researchers to characterise its central star as a weak-emission line star type are in fact of nebular origin.

scholarly journals Planetary Nebulae in the Andromeda Galaxy and its Companions

1978 ◽  
Vol 76 ◽  
pp. 19-34 ◽  
Author(s):  
Holland C. Ford
Keyword(s):  
Radial Velocity ◽  
Globular Clusters ◽  
Direct Determination ◽  
Planetary Nebulae ◽  
Emission Lines ◽  
Direct Measure ◽  
Chemical Abundances ◽  
Andromeda Galaxy ◽  
Powerful Means

The identification and observation of planetary nebulae in the Andromeda galaxy (M31) and its companions provide a powerful means of studying their old stellar populations. The direct determination of chemical abundances and radial velocities for even the brightest individual old stars is impossible at the distance of M31. The strongest emission lines of planetary nebulae are as bright as the entire visual continuum of the most luminous giants. Consequently, spectrophotometry of planetary nebulae presently provides the only direct measure of chemical abundances, and, with the exception of globular clusters, the only radial velocity determinations for the old populations.

Oral Lactobacilli Related to Caries Status of Children with Primary Dentition

2020 ◽  
Vol 54 (2) ◽  
pp. 194-204 ◽  
Author(s):  
Jinthana Lapirattanakul ◽  
Ryota Nomura ◽  
Rena Okawa ◽  
Setsuyo Morimoto ◽  
Pornpen Tantivitayakul ◽  
...  
Keyword(s):  
Dental Caries ◽  
Type I Collagen ◽  
Primary Dentition ◽  
Type I ◽  
Rdna Sequences ◽  
16S Rdna Sequences ◽  
Associated Species ◽  
Prevalent Species

Oral lactobacilli are members of a group of bacteria implicated in caries progression, although information regarding their transmission, colonization, and caries-associated species is not well established. This study isolated oral lactobacilli from a group of children with primary dentition for determination of Lactobacillus prevalence, detection of Streptococcus mutans, a major pathogen of caries initiation, and dental caries status of the children. Species of Lactobacillus isolates were determined from examination of 16S rDNA sequences. Subsequently, the most prevalent species was evaluated for involvement in caries status, and binding ability to type I collagen of all Lactobacillus isolates was determined in association with caries status. Multilocus sequence typing (MLST) of eleven loci was carried out to study strains of the predominant Lactobacillus sp. The detection of oral lactobacilli together with S. mutans was significantly associated with the highest dental caries indices, but there was no involvement of collagen-binding properties of Lactobacillus isolates in caries status. Lactobacillus fermentum was the most prevalent, and its presence was related to high scores of caries indices. MLST analysis of L. fermentum population could not specify a particular clone associated with caries status, but revealed sharing of identical L. fermentum strains among children in the same classrooms. Taken together, the data contributed useful information on the role of oral lactobacilli, in particular L. fermentum in dental caries.

scholarly journals Chemical Abundances in Magellanic Cloud Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 354-354
Author(s):  
D. J. Monk ◽  
M. J. Barlow ◽  
R. E. S. Clegg
Keyword(s):  
Spectroscopic Data ◽  
Planetary Nebulae ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Type I ◽  
Chemical Abundances ◽  
Special Groups

Optical spectroscopic data for 71 Planetary Nebulae (PN) in the Large and Small Magellanic Clouds have been analysed. The line fluxes have been used to determine nebular temperatures, densities, and the abundances of He, N, O, Ne and Ar, relative to H. In our sample there are 12 nebulae with N/O ≥ 0.5, resembling Peimbert's Type I PN; 6 low excitation (LE) objects (1 ≤ I(5007)/I(Hβ) ≤ 4); and 4 very-low-excitation (VLE) nebulae (I(Hβ) > I(5007), similar to the Galactic VLE class. Mean abundances have been calculated for the nebulae not in these special groups.

Spectrophotometry of Selected Planetary Nebulae of Type I in the Magellanic Clouds

1993 ◽  
Vol 155 ◽  
pp. 584-584 ◽  
Author(s):  
S. Torres-Peimbert ◽  
M. Peimbert ◽  
M.T. Ruitz ◽  
M. Peña
Keyword(s):  
Wavelength Range ◽  
Planetary Nebulae ◽  
Magellanic Clouds ◽  
Type I ◽  
Chemical Abundances ◽  
Spectroscopic Observations ◽  
Physical Conditions

We carried out spectroscopic observations of N67 (in the SMC), and N66, N97 and N102 (in the LMC) with the 4-m telescope of CTIO. The wavelength range is λλ 3500–7400. From these we obtained physical conditions and chemical abundances of these objects.

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