scholarly journals Determination of the primordial helium abundance Yp and its enrichment dY/dZ on the basis of chemical composition of the HII region in blue compact galaxies and planetary nebulae

2007 ◽  
Vol 11 (4) ◽  
pp. 468-472
Author(s):  
V. V. Holovatyy ◽  
B. Ya. Melekh ◽  
N. V. Havrylova
Keyword(s):  
Chemical Composition ◽  
Planetary Nebulae ◽  
Helium Abundance ◽  
Hii Region ◽  
Primordial Helium ◽  
Compact Galaxies

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 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 Determination of the Primordial Helium Abundance Based on NGC 346, an H ii Region of the Small Magellanic Cloud

2019 ◽  
Vol 876 (2) ◽  
pp. 98 ◽  
Author(s):  
Mabel Valerdi ◽  
Antonio Peimbert ◽  
Manuel Peimbert ◽  
Andrés Sixtos
Keyword(s):  
Magellanic Cloud ◽  
Helium Abundance ◽  
Small Magellanic Cloud ◽  
H Ii Region ◽  
Primordial Helium

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.

scholarly journals The Chemical Composition of Planetary Nebulae

1968 ◽  
Vol 34 ◽  
pp. 209-223 ◽  
Author(s):  
Lawrence H. Aller ◽  
Stanley J. Czyzak
Keyword(s):  
Chemical Composition ◽  
Planetary Nebulae ◽  
Quantum Mechanical ◽  
Physical Parameters ◽  
Chemical Compositions ◽  
Mechanical Theory ◽  
Gaseous Nebulae ◽  
Quantum Mechanical Theory ◽  
The One

The problem of the determination of the chemical compositions of planetary and other gaseous nebulae constitutes one of the most exasperating problems in astrophysics. On the one hand, the problem appears to be conceptually simple – the mechanisms of excitation of the various lines appear to be well understood and the necessary physical parameters can be obtained by quantum mechanical theory. Yet the task is a difficult one and we want to explore some of the significant features.

The Effect of Collisional Enhancement of Balmer Lines on the Determination of the Primordial Helium Abundance

2003 ◽  
Vol 592 (2) ◽  
pp. 846-865 ◽  
Author(s):  
V. Luridiana ◽  
A. Peimbert ◽  
M. Peimbert ◽  
M. Cervino
Keyword(s):  
Helium Abundance ◽  
Balmer Lines ◽  
Primordial Helium

scholarly journals Blue Compact Galaxies and the Primordial Helium Abundance Determination

1998 ◽  
Vol 11 (1) ◽  
pp. 137-138
Author(s):  
Y.I. Izotov ◽  
T.X. Thuan
Keyword(s):  
Linear Regression ◽  
H Ii Regions ◽  
Helium Abundance ◽  
Line Intensities ◽  
Low Metallicity ◽  
Physical Effects ◽  
Primordial Helium ◽  
Compact Galaxies ◽  
Abundance Determination

Abstract We use a sample of 45 low-metallicity H II regions to determine the primordial helium abundance Yp. We have carefully investigated the physical effects which may make the He I line intensities deviate from their recombination values such as collisional and fluorescent enhancements, underlying He I stellar absorption and absorption by Galactic interstellar Na, I. By extrapolating the Y vs. O/H linear regression to O/H = 0, we obtain Yp = 0.245±0.002. Our Yp gives 0.06±0.01.

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