Planetary nebulae in local group galaxies. III - Radial velocity observations of H II regions in the M32 field

1976 ◽  
Vol 208 ◽  
pp. 683 ◽  
Author(s):  
H. C. Ford ◽  
D. C. Jenner
Keyword(s):  
Radial Velocity ◽  
Local Group ◽  
Planetary Nebulae ◽  
H Ii Regions

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 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.

A Radial Velocity and Light Curve Study of Pulsations and Binarity in Proto-Planetary Nebulae

2015 ◽  
Vol 71-72 ◽  
pp. 127-128
Author(s):  
B.J. Hrivnak ◽  
W. Lu ◽  
G. Van de Steene ◽  
H. Van Winckel ◽  
J. Sperauskas ◽  
...  
Keyword(s):  
Light Curve ◽  
Radial Velocity ◽  
Planetary Nebulae

scholarly journals VELOCITY SEGREGATION IN A CLUMP-LIKE OUTFLOW WITH A NON-TOP HAT VELOCITY CROSS-SECTION

2021 ◽  
Vol 57 (2) ◽  
pp. 269-277
Author(s):  
A. Castellanos-Ramírez ◽  
A. C. Raga ◽  
J. Cantó ◽  
A. Rodríguez-González ◽  
L. Hernández-Martínez
Keyword(s):  
Star Formation ◽  
Simple Model ◽  
Radial Velocity ◽  
Cross Section ◽  
High Velocity ◽  
Planetary Nebulae ◽  
Young Stars ◽  
Working Surface ◽  
Star Formation Regions ◽  
Analytic Models

High velocity clumps joined to the outflow source by emission with a “Hubble law” ramp of linearly increasing radial velocity vs. distance are observed in some planetary nebulae and in some outflows in star formation regions. We propose a simple model in which a “clump” is ejected from a source over a period τ0, with a strong axis to edge velocity stratification. This non-top hat cross section results in the production of a highly curved working surface (initially being pushed by the ejected material, and later coasting along due to its inertia). From both analytic models and numerical simulations we find that this working surface has a linear velocity vs. position ramp, and therefore reproduces in a qualitative way the “Hubble law clumps” in planetary nebulae and outflows from young stars.

scholarly journals Light and velocity variability in Proto-Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 351-351
Author(s):  
Bruce J. Hrivnak ◽  
Wenxian Lu
Keyword(s):  
Physical Properties ◽  
Radial Velocity ◽  
Planetary Nebulae ◽  
Agb Stars

We have been carrying out a program of monitoring light and velocity variability in proto-planetary nebulae (PPN). Variability might arise due to binarity or pulsation. Many planetary nebulae display a bipolar shape, and it is suggested that this is caused by binarity. This can be investigated in PPN, particularly by radial velocity studies of those of spectral types F and G. Pulsation is known to exist in other types of post-AGB stars, and can be a means to learn more about the physical properties of the stars. No previous study of a sample of PPN has been published.

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 Central Stars of Young Planetary Nebulae - A New Class of Variables

2003 ◽  
Vol 209 ◽  
pp. 237-238 ◽  
Author(s):  
G. Handler
Keyword(s):  
Mass Loss ◽  
Radial Velocity ◽  
Time Scales ◽  
Variable Star ◽  
Planetary Nebulae ◽  
Stellar Mass ◽  
New Class ◽  
Stellar Pulsation ◽  
Stellar Pulsations ◽  
Central Stars

A new class of variable star is proposed. These are variable central stars of young Planetary Nebulae exhibiting roughly sinusoidal (semi)regular photometric and/or radial velocity variations with time scales of several hours. Fourteen of these objects have been identified. Their temperatures are between 25000 and 50000 K and most show hydrogen-rich spectra. The most likely reason for the variability is stellar pulsation. Another possibility would be variable stellar mass loss, but in that case the mechansism causing it must be different from that operating in massive O stars. We speculate that it actually is the stellar pulsations which cause mass loss mdulations.

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.

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