scholarly journals Chemical Composition of Planetary Nebulae: A New Determination

1993 ◽  
Vol 155 ◽  
pp. 579-579
Author(s):  
V.V. Golovaty ◽  
Yu. F. Malkov
Keyword(s):  
Chemical Composition ◽  
Massive Stars ◽  
Galactic Disk ◽  
Planetary Nebulae ◽  
Correction Factors ◽  
Galactic Bulge ◽  
Mixing Processes ◽  
Nitrogen Abundance ◽  
The Mean

A new method of the determination of planetary nebulae abundances is proposed. Unobserved ionization stages are taken into account with aid of the correlations between relative abundances of various ions which had been obtained from the grid of the photoionization models of planetary nebulae luminescence calculated by us. Simple approximative expressions for the determination of He/H, C/H, N/H, O/H, Ne/H, Mg/H, Si/H, S/H, and Ar/H are found. The chemical composition of 130 galactic planetary nebulae is revised. The observational data were compiled from 73 papers of many authors published in 1972–1991. Our mean abundances of C, N, O, Ne, S, Ar are 0.1–0.3 dex lower than the mean abundances of these elements found previously by other authors. Such a discrepancy may be due to an overestimation of “empirical” ionization correction factors in previous works. It is shown that the abundance of oxygen in massive stars-precursors may be reduced by 0.2 dex on average due to the ON-cycle, but the abundance of neon remains practically unchanged. A comparative analysis of the abundances in the galactic disk, bulge and halo nebulae is carried out. We found that helium is enhanced in the galactic bulge nebulae relative to the disk ones, but the mean nitrogen abundance and mean ratio N/O are lower in the bulge. Our data suggest that the second dredge-up did not take place in the stars-precursors of the bulge planetaries, and the helium and nitrogen enhancement in these nebulae is due to other mixing processes. The mean abundances of O, Ne, S, Ar in the galactic disk and galactic bulge nebulae are quite similar, and we must conclude that the stars-precursors of the bulge planetaries had been formed during the same burst of star formation as the stars-precursors of the disk nebulae, while the halo nebulae correspond to the previous burst.

scholarly journals Chemical Abundances in Galactic Bulge Pn

1993 ◽  
Vol 155 ◽  
pp. 581-581 ◽  
Author(s):  
N.A. Walton ◽  
M.J. Barlow ◽  
R.E.S. Clegg
Keyword(s):  
Galactic Disk ◽  
Planetary Nebulae ◽  
Solar Neighbourhood ◽  
Galactic Bulge ◽  
Low Resolution ◽  
Chemical Abundances ◽  
The Mean ◽  
Optical Spectrophotometry ◽  
High Metallicity

We present abundance determinations, in particular of carbon, and C/O ratios, for 11 Galactic bulge planetary nebulae (PN) based on our low resolution UV data from IUE observations and optical spectrophotometry from the Anglo-Australian Telescope. We compare the observed abundances with those predicted by dredge-up theory for the high metallicity Galactic bulge. The sample abundances are also contrasted with the abundances found for PN in the Galactic disk. The mean C/O ratio for the bulge PN is significantly lower than that found for Galactic disk PN. Further, we present an abundance analysis of the very metal-poor bulge PN M2-29. From an analysis of the differential extinction found from the observed ratios of the He ii 1640,4686Å lines, we find that the ultraviolet reddening law towards the bulge is steeper than in the solar neighbourhood.

scholarly journals The UV and optical reddening law to the Galactic Bulge and CNO abundances in Bulge planetary nebulae

1993 ◽  
Vol 153 ◽  
pp. 337-338
Author(s):  
N.A. Walton ◽  
M.J. Barlow ◽  
R.E.S. Clegg
Keyword(s):  
Galactic Disk ◽  
Planetary Nebulae ◽  
Line Ratio ◽  
Solar Neighbourhood ◽  
Balmer Line ◽  
Galactic Bulge ◽  
The Mean ◽  
Cno Abundances ◽  
Halo Population ◽  
Selective Extinction

An analysis of the differential ultraviolet extinction towards four bulge planetary nebulae, based on the observed line ratio of He II 1640/4686Å, shows that the ultraviolet reddening law towards the bulge is much steeper than in the solar neighbourhood. An analysis of the optical reddening law for 42 bulge PN, based upon observed Balmer line ratios and Hβ to radio free-free flux ratios, is presented. The optical reddening law towards the bulge is steeper than in the local ISM, and thus the ratio of total to selective extinction, Rv = 2.29 (± 0.50), is lower than the standard solar neighbourhood value of Rv = 3.10.We present abundance determinations, in particular C/H and C/O ratios, for 11 Galactic bulge PN, based on spectrophotometry in the UV from IUE and in the optical from the Anglo-Australian Telescope. The derived abundances are compared with values for PN in the Galactic disk. The mean C/O ratio for bulge PN is significantly lower than that found for Galactic disk PNs. Additionally we present an abundance analysis of the very metal-poor halo population PN M2-29, which is located in the bulge.

scholarly journals Chemical Composition of the Galactic Bulge in Baade's Window

2009 ◽  
Vol 5 (S265) ◽  
pp. 279-284 ◽  
Author(s):  
Andrew McWilliam ◽  
Jon Fulbright ◽  
R. Michael Rich
Keyword(s):  
Chemical Composition ◽  
Massive Stars ◽  
Galactic Bulge ◽  
Rapid Formation ◽  
The Mean ◽  
Red Clump

Abstract1. McWilliam and Zoccali (2009) show the existence of two Red Clump populations towards the Galactic bulge, based on 2MASS data. 2.Measured [Mg/Fe], [Al/Fe], and [La/Eu] ratios in the bulge are consistent with a rapid formation timescale (<1Gyr), which also requires a slightly top-heavy IMF to reproduce the mean bulge metallicity. The [C/O] and [O/Fe] ratios are consistent if their predicted metal-dependent yields from massive stars with winds are considered. The decline in explosive [α/Fe] (Si, Ca, and Ti) can only be understood if their yields also decline with metallicity above [Fe/H]~−1.

scholarly journals Chemical Composition of Galactic Planetary Nebulae and HII Regions in Blue Compact Dwarf Galaxies: New Determination

2003 ◽  
Vol 209 ◽  
pp. 565-566
Author(s):  
V.V. Holovatyy ◽  
N.V. Havrylova ◽  
B.Ya. Melekh
Keyword(s):  
Chemical Composition ◽  
Dwarf Galaxies ◽  
Planetary Nebulae ◽  
Hii Regions ◽  
Astronomical Observatory ◽  
Atomic Data ◽  
Correction Factors ◽  
Hii Region ◽  
National University

The expressions of new ionization-correction factors (ICF) (see these Proceedings) are employed for the determination of chemical composition of the 200 galactic planetary nebulae(PN) and 43 HII regions in blue compact dwarf galaxies (BCDG). We have used PN spectra from different papers published previously (> 100) and HII region spectra from (Izotov, Thuan, & Lipovetsky 1.994, Izotov, Thuan, & Lipovetsky 1997, Thuan, Izotov, & Lipovetsky hys. J. 1995). Code DIAGN (Holovatyy et al. 1999) developed at Astronomical Observatory of Lviv National University is also used. Atomic data for determination of ne, Te and the ionic abundances (A+i/H+) were modified to be compatible with the CLOUDY94 code (Ferland G.J. 1999).

scholarly journals Planetary Nebulae and the Pregalactic Helium Abundance

1989 ◽  
Vol 131 ◽  
pp. 213-213 ◽  
Author(s):  
Walter J. Maciel
Keyword(s):  
Chemical Composition ◽  
Recent Work ◽  
Planetary Nebulae ◽  
H Ii Regions ◽  
Helium Abundance

Recent work has emphasized the determination of the pregalactic helium abundance by mass Yp and the slope ΔY/ΔZ based on the chemical composition of both galactic and extragalactic H II regions (Pagel, 1987; Pagel et al., 1986).

scholarly journals The T.60 Operation at Pic du Midi

1988 ◽  
Vol 98 ◽  
pp. 102-103
Author(s):  
Christian Buil ◽  
Olivier Las Vergnas
Keyword(s):  
Chemical Composition ◽  
Planetary Nebulae ◽  
Variable Stars ◽  
Programme Committee ◽  
Experimental Trial ◽  
The World ◽  
Set Up ◽  
New Facilities ◽  
Jupiter’S Satellites

Since Spring 1983, the Pic du Midi and Toulouse Observatory has put the Gentilly 60-cm telescope at the disposal of amateurs. There was an initial experimental trial in 1982, and an amateur Programme Committee was set up in 1983. The “T.60 Association” took over the whole of the operation in 1984. So far, five hundred different amateur astronomers have used the equipment. The prime advantage of the T.60 is its site at the Pic du Midi, 2877 m altitude, one of the best observing sites in the world. By giving new facilities to amateurs, the T.60 offers considerable scientific and educational rewards. Work that has already been carried out includes: determination of H-R diagrams of faint clusters, spectra of planetary nebulae, polarimetric and interferometric studies of nebulae, photoelectric and visual studies of variable stars, research into the chemical composition of faint stars, and observations of mutual phenomena of Jupiter’s satellites.

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.

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