scholarly journals Hydrogen Deficient Planetary Nebulae: Preliminary Results

1985 ◽  
Vol 87 ◽  
pp. 359-365 ◽  
Author(s):  
S.R. Pottasch ◽  
A. Mampaso ◽  
A. Manchado ◽  
J. Menzies
Keyword(s):  
Correction Factor ◽  
Heavy Element ◽  
Planetary Nebulae ◽  
Ionization State ◽  
Abundance Gradient ◽  
Element Abundances ◽  
Preliminary Results ◽  
Very High

AbstractNew spectra of A78 and A58 at different positions in the nebulae are presented. An abundance gradient is found in A78, extending quite close to the center. Similarly the nebulous knot near the center of A58 has considerably higher heavy element abundances than the outer regions of this nebula. The ionization state is considerably lower in A58 than A78. In A78 most of the neon is in the form of Ne+3 and Ne+4, indicating that the standard ionization correction factor as used by Jacoby and Ford, is substantially in error. Finally, the very high infrared excesses found in this nebulae are discussed.

scholarly journals Chemical Abundances from Planetary Nebulae in the Magellanic Clouds

1995 ◽  
Vol 10 ◽  
pp. 476-479 ◽  
Author(s):  
M.J. Barlow
Keyword(s):  
Electron Temperature ◽  
Heavy Element ◽  
Planetary Nebulae ◽  
Density Fluctuations ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Chemical Abundances ◽  
Element Abundances

AbstractHeavy element abundances, in particular those of oxygen, obtained from recent spectroscopic surveys of Magellanic Cloud planetary nebulae (PN), are reviewed and compared with those derived for H regions and objects in our own galaxy. These abundances have been based on collisionally excited lines and are very sensitive to the adopted electron temperature. There is increasing evidence that temperature or density fluctuations within nebulae lead to the electron temperatures being overestimated, with the corollary that the heavy element abundances have been underestimated.

scholarly journals Absorption Line Systems at z > 3 in the QSO 2000-330

1987 ◽  
Vol 124 ◽  
pp. 799-802
Author(s):  
R.W. Hunstead ◽  
M. Pettini ◽  
J.C. Blades ◽  
H.S. Murdoch
Keyword(s):  
High Resolution ◽  
Absorption Line ◽  
Heavy Element ◽  
Absorption Lines ◽  
List Type ◽  
Type Number ◽  
Element Abundances ◽  
Preliminary Results ◽  
Forest Region ◽  
Velocity Dispersions

This paper presents some preliminary results from analysis of our high-resolution (30–35 km/s FWHM) spectra of the Lyman α forest region in the z = 3.78 QSO 2000-330. These spectra were obtained at the Anglo-Australian Telescope over several observing seasons and have been analysed by fitting multiple-cloud Voigt profiles to Lyman series and heavy-element absorption lines. Two specific issues are addressed here: (i)The distribution of column densities, N(H I), and velocity dispersions, b, for hydrogen clouds in the interval zabs = 3.43–3.78;(ii)Heavy-element abundances in a system at zabs = 3.1723.

scholarly journals A Possible Subdivision of Type II Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 222-222
Author(s):  
M. Faúndez-Abans ◽  
W. J. Maciel
Keyword(s):  
Heavy Element ◽  
Classification Scheme ◽  
Planetary Nebulae ◽  
Type Ii ◽  
Element Abundances ◽  
Nitrogen Abundance

A revision is made of the classification scheme of planetary nebulae proposed by Peimbert (1978), taking into account the observed heavy-element abundances and radial abundance gradients (Faúndez-Abans and Maciel, 1986; 1987a). A subdivision is proposed of type II PN into the subtypes a and b, according to their nitrogen abundances relative to hydrogen (Faundez-Abans and Maciel, 1987b). Type IIa PN show a higher enrichment in nitrogen than type IIb, which present a nitrogen abundance close to the value of population I objects and a radial N/H gradient as well.

Distribution of R- and S-Process Elements in the Galactic Halo

1988 ◽  
Vol 132 ◽  
pp. 501-506
Author(s):  
C. Sneden ◽  
C. A. Pilachowski ◽  
K. K. Gilroy ◽  
J. J. Cowan
Keyword(s):  
Heavy Element ◽  
Galactic Halo ◽  
Low Noise ◽  
Heavy Elements ◽  
Process Synthesis ◽  
Element Abundances ◽  
Halo Stars ◽  
Abundance Patterns ◽  
R Process ◽  
Process Elements

Current observational results for the abundances of the very heavy elements (Z>30) in Population II halo stars are reviewed. New high resolution, low noise spectra of many of these extremely metal-poor stars reveal general consistency in their overall abundance patterns. Below Galactic metallicities of [Fe/H] Ã −2, all of the very heavy elements were manufactured almost exclusively in r-process synthesis events. However, there is considerable star-to-star scatter in the overall level of very heavy element abundances, indicating the influence of local supernovas on element production in the very early, unmixed Galactic halo. The s-process appears to contribute substantially to stellar abundances only in stars more metal-rich than [Fe/H] Ã −2.

The effect of heterotrophic yield on the assessment of the correction factor for anoxic growth

1996 ◽  
Vol 34 (5-6) ◽  
pp. 67-74 ◽  
Author(s):  
D. Orhon ◽  
S. Sözen ◽  
N. Artan
Keyword(s):  
Correction Factor ◽  
Domestic Sewage ◽  
Yield Coefficient ◽  
Heterotrophic Growth ◽  
Metabolic Processes ◽  
Anoxic Conditions ◽  
Industrial Wastewaters ◽  
Systems Modelling ◽  
Kinetics Of ◽  
Very High

For single-sludge denitrification systems, modelling of anoxic reactors currently uses the kinetics of aerobic heterotrophic growth together with a correction factor for anoxic conditions. This coefficient is computed on the basis of respirometric measurements with the assumption that the heterotrophic yield remains the same under aerobic and anoxic coditions. The paper provides the conceptual proof that the yield coefficient is significantly lower for the anoxic growth on the basis of the energetics of the related metabolic processes. This is used for the interpretation of the very high values for the correction factor experimentally determined for a number of industrial wastewaters. A default value for the anoxic heterotrophic yield coefficient is calculated for domestic sewage and compatible wastewaters and proposed for similar evaluations.

Heavy‐Element Abundances in Blue Compact Galaxies

1999 ◽  
Vol 511 (2) ◽  
pp. 639-659 ◽  
Author(s):  
Yuri I. Izotov ◽  
Trinh X. Thuan
Keyword(s):  
Heavy Element ◽  
Element Abundances ◽  
Compact Galaxies

scholarly journals The curious conundrum regarding sulfur and oxygen abundances in planetary nebulae

2011 ◽  
Vol 7 (S283) ◽  
pp. 384-385
Author(s):  
Richard B. C. Henry ◽  
Angela Speck ◽  
Amanda I. Karakas ◽  
Gary J. Ferland
Keyword(s):  
Correction Factor ◽  
Planetary Nebulae ◽  
Ultimate Explanation

AbstractWe carefully consider numerous explanations for the sulfur abundance anomaly in planetary nebulae. No one rationale appears to be satisfactory, and we suggest that the ultimate explanation is likely to be a heretofore unidentified feature of the nebular gas which significantly impacts the sulfur ionization correction factor.

scholarly journals Near–Infrared Imaging of Proto-Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 340-340 ◽  
Author(s):  
R.E.S. Clegg ◽  
N. A. Walton ◽  
M.J. Barlow
Keyword(s):  
Molecular Hydrogen ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Planetary Nebulae ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Preliminary Results ◽  
Near Ir ◽  
Intermediate Mass Stars ◽  
Hydrogen Lines

It is not really known how low and intermediate mass stars eject mass to form PNs. We present preliminary results from a programme of near–IR imaging, in which we study a sequence of objects, from extreme AGB stars through proto–planetaries to young, compact PNs. We aim to study the sequence of morphologies, to see where the onset of bipolar shaping occurs, and to use the IR molecular hydrogen lines to map neutral regions around ionized nebulae.

Tracing the Origins of the Ice Giants through Noble Gas Isotopic Composition

2021 ◽  
Author(s):  
Kathleen Mandt ◽  
Olivier Mousis ◽  
Jonathan Lunine ◽  
Bernard Marty ◽  
Thomas Smith ◽  
...  
Keyword(s):  
Solar System ◽  
Isotopic Composition ◽  
Heavy Element ◽  
Noble Gas ◽  
Giant Planet ◽  
Isotope Ratios ◽  
Building Blocks ◽  
Giant Planets ◽  
Element Abundances ◽  
Current State

<p>The current composition of giant planet atmospheres provides information on how such planets formed, and on the origin of the solid building blocks that contributed to their formation. Noble gas abundances and their isotope ratios are among the most valuable pieces of evidence for tracing the origin of the materials from which the giant planets formed. In this review we first outline the current state of knowledge for heavy element abundances in the giant planets and explain what is currently understood about the reservoirs of icy building blocks that could have contributed to the formation of the Ice Giants. We then outline how noble gas isotope ratios have provided details on the original sources of noble gases in various materials throughout the solar system. We follow this with a discussion on how noble gases are trapped in ice and rock that later became the building blocks for the giant planets and how the heavy element abundances could have been locally enriched in the protosolar nebula. We then provide a review of the current state of knowledge of noble gas abundances and isotope ratios in various solar system reservoirs, and discuss measurements needed to understand the origin of the ice giants. Finally, we outline how formation and interior evolution will influence the noble gas abundances and isotope ratios observed in the ice giants today. Measurements that a future atmospheric probe will need to make include (1) the <sup>3</sup>He/<sup>4</sup>He isotope ratio to help constrain the protosolar D/H and <sup>3</sup>He/<sup>4</sup>He; (2) the <sup>20</sup>Ne/<sup>22</sup>Ne and <sup>21</sup>Ne/<sup>22</sup>Ne to separate primordial noble gas reservoirs similar to the approach used in studying meteorites; (3) the Kr/Ar and Xe/Ar to determine if the building blocks were Jupiter-like or similar to 67P/C-G and Chondrites; (4) the krypton isotope ratios for the first giant planet observations of these isotopes; and (5) the xenon isotopes for comparison with the wide range of values represented by solar system reservoirs.</p><p>Mandt, K. E., Mousis, O., Lunine, J., Marty, B., Smith, T., Luspay-Kuti, A., & Aguichine, A. (2020). Tracing the origins of the ice giants through noble gas isotopic composition. Space Science Reviews, 216(5), 1-37.</p>

The Inner Abundance Gradient of M33 from Bright Planetary Nebulae

2006 ◽  
pp. 234-238
Author(s):  
Grażyna Stasińska ◽  
José M. Vílchez ◽  
Enrique Pérez ◽  
Rosa M. Gonzalez Delgado ◽  
Romano L.M. Corradi ◽  
...  
Keyword(s):  
Planetary Nebulae ◽  
Abundance Gradient
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