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 New Ionization-Correction Factors for the Chemical Composition Determination of Galactic Planetary Nebulae and HII Regions in Blue Compact Dwarf Galaxies

2003 ◽  
Vol 209 ◽  
pp. 563-564
Author(s):  
V.V. Holovatyy ◽  
N.V. Havrylova ◽  
B.Ya. Melekh
Keyword(s):  
Chemical Composition ◽  
Energy Distribution ◽  
Filling Factor ◽  
Dwarf Galaxies ◽  
Planetary Nebulae ◽  
Hii Regions ◽  
Stellar Atmosphere ◽  
Hydrogen Atoms ◽  
B Stars ◽  
Free Parameters

The photoionization models (PhM) grid of the planetary nebulae (PN) and the HII regions in the blue compact dwarf galaxies (BCDG) was calculated. For grids modeling we used the CLOUDY94 code (Ferland G.J. 1999). Free parameters for PN grid were: (1) energy distribution, that corresponds to temperature of each of 15 chosen models (Clegg & Middlemass 1987); (2) chemical composition of nebular gas in models; (3) filling factor with its values, for every model, being equal to 0.1, 0.5 and 1. For HII regions the free parameters were: (1) energy distribution in the spectra of nuclei emission obtained for HII regions in BCDG by our method (Golovaty 1987, Melekh 2000) from high-quality observations (Izotov, Thuan, & Lipovetsky 1994, Izotov, Thuan, & Lipovetsky 1997, Thuan, Izotov, & Lipovetsky hys. J. 1995) of these objects (the method uses stellar atmosphere models of O-B stars (Schaerer et al. 1996, Schaerer & de Koter 1997)); (2) nebular gas filling factor with the values ranging from 0.0001 to 1; (3) the relative abundance of heavy elements; (4) the concentration of hydrogen atomsnH. All PhM were assumed to be spherically-symmetrical. As a result, 135 PN PhM and 270 HII regions PhM were calculated.

scholarly journals Ionized gas in dwarf galaxies: Abundance indicators

2008 ◽  
Vol 4 (S255) ◽  
pp. 375-380 ◽  
Author(s):  
Grażyna Stasińska
Keyword(s):  
Chemical Composition ◽  
Unsolved Problem ◽  
Dwarf Galaxies ◽  
Temperature Fluctuations ◽  
Hii Regions ◽  
Ionized Gas ◽  
Hii Region

AbstractWe discuss the four basic methods to derive HII region abundances in metal-poor galaxies by presenting a few recent results obtained with these methods. We end up by commenting on the yet unsolved problem of temperature fluctuations in HII regions, which may plague abundance determinations, as well as the discrepancy between abundances derived from recombination lines and collisionally excited lines, to which inhomogeneous chemical composition might be the explanation.

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 Abundances for a large sample of galactic Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 408-408 ◽  
Author(s):  
V. V. Golovaty ◽  
Yu.F. Malkov
Keyword(s):  
Chemical Composition ◽  
Observational Data ◽  
Planetary Nebulae ◽  
Central Star ◽  
Atomic Data ◽  
Large Sample ◽  
Photoionization Model ◽  
Abundance Determination

We present a database on the chemical composition of 200 planetary nebulae (PNe) in our Galaxy. Abundances of He, C, N, O, Ne, Mg, Si, S, and Ar are found for 175, 64, 190, 200, 170, 13, 40, 173, and 187 PNe respectively. The abundances for all PNe are obtained with the same atomic data and by the same method of abundance determination, so the database is highly homogeneous. The method of the determination of nebular abundances based on a photoionization model grid is described by Golovaty et al. (1993). Observational data have been compiled from 105 papers published in 1976–1994. For most of PNe in our sample, the distances and central star masses are determined as well (Malkov, this volume).

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