Temperature Fluctuations, H ii Region Abundances, and Primordial Helium

1998 ◽  
pp. 95-103
Author(s):  
Gary Steigman ◽  
Sueli M. Viegas ◽  
Ruth Gruenwald
Keyword(s):  
Temperature Fluctuations ◽  
H Ii Region ◽  
Primordial Helium

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 Concerning the Primordial Abundance of Helium in Quasi-Stellar Sources

1972 ◽  
Vol 44 ◽  
pp. 474-477
Author(s):  
Joseph Silk
Keyword(s):  
Galaxy Formation ◽  
Temperature Fluctuations ◽  
Helium Content ◽  
Primordial Abundance ◽  
Primordial Helium ◽  
Stellar Sources ◽  
Absolute Luminosity

Primordial temperature fluctuations, which appear to be necessary in order to explain aspects of galaxy formation, can lead to observable effects in some objects. In QSS and other compact systems a correlation of absolute luminosity with primordial helium content is predicted.

scholarly journals Photo-ionization models of NGC 2363 and their implications

1999 ◽  
Vol 193 ◽  
pp. 487-488
Author(s):  
Valentina Luridiana ◽  
Manuel Peimbert ◽  
Claus Leitherer
Keyword(s):  
Observational Data ◽  
Emission Spectra ◽  
Temperature Fluctuations ◽  
High Mass ◽  
Observational Constraints ◽  
Stellar Cluster ◽  
A Value ◽  
Low Metallicity ◽  
H Ii Region ◽  
Photo Ionization

We compute photo-ionization models for the giant extragalactic H II region NGC 2363, and compare them with optical observational data. We focus on the following observational constraints: F(Hβ), Ne, EW(Hβ), and the ratios of I(λ 5007), I(λ 4363), I(λ 3727), I(λ 6300), I(λ 6720) and I(λ 4686) relative to I(Hβ). We discuss the variations of the emission spectra obtained with different input parameters. We show that low metallicity models (Z = 0.10Z⊙) cannot reproduce the observed features of the spectrum, and that the disagreement can be satisfactorily overcome by allowing for spatial temperature fluctuations in the nebula. Accordingly, we show that the metallicity of NGC 2363 has most probably been underestimated, and that a value of Z ≃ 0.25 Z⊙ is in better agreement with the observational data than the usually adopted value Z≃0.10Z⊙. We also derive values for the slope and the high mass end of the IMF, as well as the age of the stellar cluster.

scholarly journals The Magellanic Clouds and the Primordial Helium Abundance

2000 ◽  
Vol 198 ◽  
pp. 194-203 ◽  
Author(s):  
Manuel Peimbert ◽  
Antonio Peimbert
Keyword(s):  
Neutral Hydrogen ◽  
Magellanic Clouds ◽  
Heavy Elements ◽  
H Ii Regions ◽  
Helium Abundance ◽  
Temperature Variations ◽  
Systematic Effects ◽  
H Ii Region ◽  
Primordial Helium

A new determination of the pregalactic helium abundance based on the Magellanic Clouds H II regions is discussed. This determination amounts to Yp = 0.2345 ± 0.0030 and is compared with those derived from giant extragalactic H II regions in systems with extremely low heavy elements content. It is suggested that the higher primordial value derived by other authors from giant H II region complexes could be due to two systematic effects: the presence of neutral hydrogen inside the helium Strömgren sphere and the presence of temperature variations inside the observed volume.

scholarly journals No temperature fluctuations in the giant H II region H 1013

2013 ◽  
Vol 551 ◽  
pp. A82 ◽  
Author(s):  
G. Stasińska ◽  
C. Morisset ◽  
S. Simón-Díaz ◽  
F. Bresolin ◽  
D. Schaerer ◽  
...  
Keyword(s):  
Temperature Fluctuations ◽  
H Ii Region

The primordial helium abundance determination using multicomponent photoionization modelling of low-metallicity H II regions

2018 ◽  
Vol 8 (1) ◽  
pp. 16-23
Author(s):  
I. Koshmak ◽  
B. Melekh
Keyword(s):  
Chemical Compositions ◽  
H Ii Regions ◽  
Helium Abundance ◽  
Rotating Stars ◽  
Chemical Abundances ◽  
Free Expansion ◽  
Outer Component ◽  
Low Metallicity ◽  
H Ii Region ◽  
Primordial Helium

The method for the multicomponent photoionization modelling (MPhM) of low-metallicity H II regions surrounding the starburst region was developed. The internal structure of the H II region has been determined using the evolutionary modelling of the superwind bubble surrounding the star-forming region. Models of Chevalier and Clegg (1985) and Weaver et al. (1977) have been used to determine the radial distribution of the gas density, the velocity of gas layers, and the temperature within internal components (the region of the superwind free expansion and the cavity, respectively). The chemical abundances in region of the superwind free expansion were obtained from the evolutionary population synthesis with including of rotating stars. The chemical abundances within cavity were defined by averaging over mass the chemical compositions of mixture of the abundances of gas from superwind and ones within outer component, because of gas evaporation from external component into the cavity. External components of our models describe a high-density, thin shell of gas formed by superwind shock and a typical undisturbed hydrodynamically H II region, respectively. Evolutionary grids of multicomponent low-metallicity models are calculated. A comparative analysis of the results of their calculation with the observed data has been carried out. The ionic abundances averaged over modelling volume as well as chemical composition assumed in models were used to derive the new expressions for ionization-correction factors that were used to redetermine the chemical compositions of 88 H II regions in blue compact dwarf galaxies. It must be noticed that we used for this propose the ionic abundances obtained by Izotov et al. (2007). In result the primordial helium abundance and its enrichment during stellar chemical evolution of matter were determined.

scholarly journals A new determination of the primordial helium abundance using the analyses of H ii region spectra from SDSS

2021 ◽  
Vol 502 (2) ◽  
pp. 3045-3056
Author(s):  
O A Kurichin ◽  
P A Kislitsyn ◽  
V V Klimenko ◽  
S A Balashev ◽  
A V Ivanchik
Keyword(s):  
Sloan Digital Sky Survey ◽  
H Ii Regions ◽  
Helium Abundance ◽  
Physical Conditions ◽  
Sky Survey ◽  
H Ii Region ◽  
Standard Cosmological Model ◽  
Primordial Helium ◽  
Good Agreement

ABSTRACT The precision measurement of the primordial helium abundance Yp is a powerful probe of the early Universe. The most common way to determine Yp is the analyses of observations of metal-poor H ii regions found in blue compact dwarf galaxies. We present the spectroscopic sample of 100 H ii regions collected from the Sloan Digital Sky Survey. The final analysed sample consists of our sample and HeBCD data base from Izotov et al. (2007). We use a self-consistent procedure to determine physical conditions, current helium abundances, and metallicities of the H ii regions. From a regression to zero metallicity, we have obtained Yp = 0.2462 ± 0.0022, which is one of the most stringent constraints obtained with such methods up to date and is in a good agreement with the Planck result $Y_{\rm p}^{\it {\mathrm{ Planck}}} = 0.2471 \pm 0.0003$. Using the determined value of Yp and the primordial deuterium abundance taken from Particle Data Group (Zyla et al. 2020) we put a constraint on the effective number of neutrino species Neff = 2.95 ± 0.16, which is consistent with the Planck one Neff = 2.99 ± 0.17. Further increase of statistics potentially allows us to achieve Planck accuracy, which in turn will become a powerful tool for studying the self-consistency of the standard cosmological model and/or physics beyond.

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