Electron Temperatures Derived from Observations of Low-Density H II Regions and Planetary Nebulae

1966 ◽  
Vol 143 ◽  
pp. 168 ◽  
Author(s):  
C. R. O'dell
Keyword(s):  
Planetary Nebulae ◽  
H Ii Regions ◽  
Low Density

scholarly journals Planetary Nebulae in Local Group Galaxies

1983 ◽  
Vol 103 ◽  
pp. 443-460
Author(s):  
Holland C. Ford
Keyword(s):  
Local Group ◽  
Planetary Nebulae ◽  
Stellar Populations ◽  
Chemical Compositions ◽  
H Ii Regions ◽  
Helium Abundance ◽  
Abundance Gradient ◽  
Star Forming ◽  
Ic 10 ◽  
Ngc 6822

Recent surveys for planetary nebulae have given the first identifications in Fornax, NGC 6822, M33, IC 10, Leo A, Sextans A, Pegasus, WLM, NGC 404, and M81, and extended the identifications in the SMC, the LMC, and M31. Observations of planetaries have established chemical compositions in old or intermediate age populations in 8 Local Group galaxies. The chemical compositions show that i) the helium abundance is higher in planetary nebulae than in H II regions in the same galaxy, and ii) nitrogen is overabundant relative to H II regions by factors of 4 to 100. Planetary nebulae are not a major source of helium in star-forming galaxies, and are a major source of nitrogen. The planetary in Fornax has a relatively high O abundance, and, together with Fornax's carbon stars, establishes the presence of at least 2 stellar populations. The abundance gradient derived from 3 planetaries in M31 is very shallow, and gives high abundances at ~ 20 kpc. By using planetary nebulae as standard candles, upper and lower distance limits have been set for 10 Local Group candidates, and a new distance estimated for M81.

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 What do planetary nebulae and H II regions reveal about the chemical evolution of nearby dwarf galaxies?

2018 ◽  
Vol 14 (S344) ◽  
pp. 161-177 ◽  
Author(s):  
Denise R. Gonçalves
Keyword(s):  
Chemical Evolution ◽  
Local Group ◽  
Planetary Nebulae ◽  
H Ii Regions ◽  
Chemical Abundances ◽  
Local Universe ◽  
Time Line ◽  
Nearby Galaxies ◽  
H Ii Region ◽  
Age Range

AbstractThe Local Group contains a great number of dwarf irregulars and spheroidals, for which the spectroscopy of individual stars can be obtained. Thus, the chemical evolution of these galaxies can be traced, with the only need of finding populations spanning a large age range and such that we can accurately derive the composition. Planetary nebulae (PNe) are old- and intermediate-age star remnants and their chemical abundances can be obtained up to 3-4 Mpc. H ii regions, which are brighter and much easily detected, represent galaxies young content. PNe and H ii regions share similar spectroscopic features and are analysed in the same way. Both are among the best tracers of the chemical evolution allowing to draw the chemical time line of nearby galaxies. The focus in this review are the PN and H ii region populations as constraints to the chemical evolution models and the mass-metallicity relation of the local universe.

scholarly journals The 100 strongest radio point sources in the field of the Large Magellanic Cloud at 1.4 GHz

2009 ◽  
pp. 65-70 ◽  
Author(s):  
J.L. Payne ◽  
L.A. Tauber ◽  
M.D. Filipovic ◽  
E.J. Crawford ◽  
Horta de
Keyword(s):  
Spectral Index ◽  
Planetary Nebulae ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Point Sources ◽  
H Ii Regions ◽  
Short Spacing ◽  
Mosaic Image ◽  
Initial List ◽  
Compact Array

We present the 100 strongest 1.4 GHz point sources from a new mosaic image in the direction of the Large Magellanic Cloud (LMC). The observations making up the mosaic were made using Australia Telescope Compact Array (ATCA) over a ten year period and were combined with Parkes single dish data at 1.4 GHz to complete the image for short spacing. An initial list of co-identifications within 1000 at 0.843, 4.8 and 8.6 GHz consisted of 2682 sources. Elimination of extended objects and artifact noise allowed the creation of a refined list containing 1988 point sources. Most of these are presumed to be background objects seen through the LMC; a small portion may represent compact H ii regions, young SNRs and radio planetary nebulae. For the 1988 point sources we find a preliminary average spectral index (?) of -0.53 and present a 1.4 GHz image showing source location in the direction of the LMC.

scholarly journals H166  Studies of Extended Low-Density H II Regions Associated With IC 1795 (W3)

1976 ◽  
Vol 176 (1) ◽  
pp. 135-143 ◽  
Author(s):  
L. Hart ◽  
A. Pedlar
Keyword(s):  
H Ii Regions ◽  
Low Density

scholarly journals Chemical evolution of the galactic interstellar medium: abundance gradients

1979 ◽  
Vol 84 ◽  
pp. 307-316 ◽  
Author(s):  
Manuel Peimbert
Keyword(s):  
Interstellar Medium ◽  
Chemical Evolution ◽  
Planetary Nebulae ◽  
Observational Evidence ◽  
H Ii Regions

Recent abundance determinations of galactic H II regions and planetary nebulae are reviewed. The presence of O/H and N/H abundance gradients is well established; there is observational evidence indicating the presence of N/S, He/H and C/H abundance gradients. Some implications of these results are discussed.

scholarly journals A Survey of Recombination-line Abundances in Planetary Nebulae and H II Regions

2003 ◽  
Vol 209 ◽  
pp. 383-384 ◽  
Author(s):  
Y. G. Tsamis ◽  
M. J. Barlow ◽  
X.-W. Liu ◽  
I. J. Danziger
Keyword(s):  
Planetary Nebulae ◽  
Magellanic Cloud ◽  
H Ii Regions ◽  
Recombination Line ◽  
Large Aperture

We have derived C, N and O abundances, relative to H, using optical recombination lines (ORLs), for a number of galactic planetary nebulae and for three Magellanic Cloud PNe (LMC N66, N141, SMC N87) and compared them with the corresponding abundances derived from collisionally-excited lines (CELs). Our goal was to investigate the fact that PNe ORL abundances are in most cases larger than those obtained from CELs. Our scanning, long-slit observations were combined with large-aperture IUE, IRAS and ISO data to yield integrated abundances for more than half of our target objects.

scholarly journals Plasma diagnostics for planetary nebulae and H ii regions using N ii and O ii optical recombination lines

2011 ◽  
Vol 7 (S283) ◽  
pp. 432-433
Author(s):  
Ian A. McNabb ◽  
Xuan Fang ◽  
Xiao–Wei Liu ◽  
Peter J. Storey
Keyword(s):  
Plasma Diagnostics ◽  
Planetary Nebulae ◽  
Coupling Scheme ◽  
H Ii Regions ◽  
Diagnostic Analysis ◽  
Plasma Diagnostic ◽  
Intermediate Coupling ◽  
Physical Conditions ◽  
Cold Metal ◽  
Intermediate Coupling Scheme

AbstractWe carry out plasma diagnostic analysis for a number of planetary nebulae (PNe) and H ii regions. We use N ii and O ii optical recombination lines (ORLs) with new effective recombination coefficients calculated under the intermediate coupling scheme, for a range of electron temperatures (Te) and densities (Ne), and fitted against the most reliable measurements. Comparing Te derived from ORLs, collisionally excited lines (CELs), the hydrogen Balmer Jump, and/or He i if available, we find the relation Te (ORLs) < Te (He i) < Te (H i BJ) < Te (CELs), confirming the physical conditions in the bi-abundance model postulated by Liu et al., i.e. the nebula contains another cold, metal-rich and probably H-deficient component.

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

2017 ◽  
Vol 601 ◽  
pp. A147 ◽  
Author(s):  
S. N. Flores-Durán ◽  
M. Peña ◽  
M. T. Ruiz
Keyword(s):  
Planetary Nebulae ◽  
Chemical Study ◽  
H Ii Regions

scholarly journals Planetary Nebulae: An Introductory Review

1983 ◽  
Vol 103 ◽  
pp. 1-13
Author(s):  
Lawrence H. Aller
Keyword(s):  
Interstellar Medium ◽  
Radio Frequency ◽  
Stellar Evolution ◽  
Planetary Nebulae ◽  
Galactic Structure ◽  
Low Density ◽  
Introductory Review

Planetary nebulae constitute a popular field of investigation because they offer a unique opportunity to study the final stages of stellar evolution before a star dies. They supply challenges not only to the stellar evolution expert but also to the spectroscopist, to the student of galactic structure, and to all observers, whether one works in the optical, ultraviolet (UV), infrared (IR) or radio-frequency (r.f.) ranges. They offer insights into properties of dusty, low-density plasmas which may help unravel problems of the interstellar medium (ISM) and quasars. Finally, many are aesthetically beautiful art creations.

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