The abundance of the chemical elements is a measure of the occurrence of the chemical elements relative to all other elements in a given environment. Klimenko , ⦠Google Scholar. A single value of the baryon density fits 4 abundances simultaneously. Porter, Ferland, Storey, & Detisch (2012) have recently published updated He I emissivities based on improved photoionization cross-sections. In an attempt to better reduce the latter, and continue to better characterize the former, we apply MCMC methods to the large dataset recently compiled by Izotov, Thuan, & Stasiska (2007). Keith MacAdam. The He I emissivities are the foundation of the model of the H II region's emission. He i Emission in the Orion Nebula and Implications for Primordial Helium Abundance. Title: The primordial helium abundance and the number of neutrino families. 2. In the Orion analysis, we eliminate some weak and blended lines and compare theory and observation for our reduced line list. Download Free PDF. The Primordial Helium Abundance. As gas cycles through generations of stars, hydrogen is burned to helium-4 (and beyond), increasing the 4 He abundance above its primordial value. Primordial helium abundance is normally inferred from the measurements of interstellar gas in the galaxies close to our own where star formation does not ⦠The strategy, therefore, is to concentrate on determining the helium abundance in the most nearly primordial regions of low metallicity which, as with deuterium, lie outside of the Galaxy. Fusion processes in post-main sequence stars are responsible for many of the heavier nuclei. Helium is the second most abundant element in the visible universe and its cosmological significance was recognised by Alpher et al. These nebulae form the basis for measuring the primordial helium abundance. (en) Helium is a colorless, odorless, tasteless, non-toxic, inert monatomic chemical element, that heads the noble gas series in the periodic table and whose atomic number is 2. Additionally, a high-signal-to-noise ratio is essential. It is now known that the elements observed in the Universe were created ineither of two ways. Other than protium, helium-3 is the only stable isotope of any element with more protons than neutrons. For the purposes of stellar nucleosynthesis calculations that require a primordial He abundance (for metal fraction Z = 0), I adopt the predicted ⦠Our result indicates that it is premature to emphasize a discrepancy. The Problem. Hydrogen-Helium Abundance Hydrogen and helium account for nearly all the nuclear matter in today's universe. The final ⦠the errors associated with nearly all attempts to calculate the primordial helium abundance from such observations. II. Observations of metal-poor extragalactic H II regions allow the determination of the primordial helium abundance, Y p. The He I emissivities are the foundation of the model of the H II region's emission. In the Orion analysis, we eliminate some weak and blended lines and compare theory and observation for our reduced line list. The data have been taken with the Focal Reducer Low Dispersion Spectrograph 1 (FORS1) at the 8.2-m Very Large Telescope. These nebulae form the basis for measuring the primordial helium abundance. Cosmic Abundance of Helium and Hydrogen The Big Bang theory provides a natural way to explain the present abundance of the elements. Helium, chemical element, inert gas of Group 18 (noble gases) of the periodic table. Observational measures of the primordial helium mass fraction, YP, are of interest for cosmology and fundamental particle physics. PDF. I present a brief review on the determination of the primordial helium abundance by unit mass, Yp. The second lightest element, helium is a colorless, odorless, and tasteless gas that becomes liquid at -268.9 degrees Celsius. The observed motions of the metal poor stars are indicators of their age, and hence their likelihood of being true carriers of primordial abundances. Light elements (namely deuterium, helium, and lithium) were produced in thefirst few minutes of the Big Bang, while elements heavier than helium arethought to have their origins in the interiors of stars ⦠The data have been taken with the Focal Reducer Low Dispersion Spectrograph 1 (FORS1) at the 8.2-m Very Large Telescope. The primordial abundance of {sup 4}He: An update. A short summary of ⦠Hydrogen-Helium Abundance Hydrogen and helium account for nearly all the nuclear matter in today's universe. The Primordial Helium Abundance. We stress that the main result of the present work is the increase in the size of the uncertainty rather than the shift in the primordial value. Presently, the best constraints on Yp come from observations of star forming regions in very metal-poor galaxies (although the impact of Yp on the CMB has been detected). Authors: Antonio Peimbert, Manuel Peimbert, Valentina Luridiana. Primordial nucleosynthesisis believed by most cosmologists to have taken place in the interval from roughly 10 se⦠The goal being to measure Y, the helium mass fraction present in ionised gas of low heavy element abundance. Porter, Ferland, Storey, & Detisch (2012) have recently published updated He I emissivities based on improved photoionization cross-sections. The American Astronomical Society (AAS), established in 1899 and based in Washington, DC, is the major organization of professional astronomers in ⦠Izotov, Yuri I. ; Thuan, Trinh X. ; Lipovetsky, Valentin A. Abstract. Cosmology / Astrophysics. There is evidence for temperature fluctuations in Planetary Nebulae and in some Galactic H II regions. Images should be at least 640×320px (1280×640px for best display). Download PDF Search for other works by this author on: Oxford Academic. CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): We present results from photoionization models of low-metallicity H II regions. Hydrogen-Helium Abundance. Hydrogen and helium account for nearly all the nuclear matter in today's universe. This is consistent with the standard or "big bang" model. The process of forming the hydrogen and helium and other trace constituents is often called "big bang nucleosynthesis". . Early studies have pioneered a method by which one can extrapolate the He/H versus O/H relation to the primordial abundance, Y p as the oxygen abundance tends to zero (Peimbert & Torres-Peimbert 1974; Lequeux et al. OSTI.GOV Journal Article: The primordial helium abundance from updated emissivities Title: The primordial helium abundance from updated emissivities Full Record Primordial Helium Abundance and the Primordial Fireball. We apply a recently developed theoretical model of helium emission to observations of both the Orion Nebula and a sample of extragalactic H II regions. This paper. Abundance is measured in one of three ways: by the mass-fraction (the same as weight fraction); by the mole-fraction (fraction of atoms by numerical count, or sometimes fraction of molecules in gases); or by the volume-fraction. ABSTRACT. It is assumed in the calculation that the present temperature of the primordial fireball is 3 K, and the abundances are computed for two values of the present mean density of matter in tbe ⦠The U.S. Department of Energy's Office of Scientific and Technical Information Andrey Tsivilev. Primordial helium abundance is normally inferred from the measurements of interstellar gas in the galaxies close to our own where star formation does not ⦠Gary Ferland. Our Orion analysis suggests that the problem does not lie in the theoretical models. Primordial Helium Abundance. I present a brief review on the determination of the primordial helium abundance by unit mass, Yp. obtenemos una E. Aver, K. A. Olive and E. D. Skillman, âA new approach to systematic uncertainties and self-consistency in helium abundance determinations,â JCAP 05 (2010) 003. The value of the primordial helium abundance as a constraint on the age of the universe is discussed emphasizing the age of the oldest stars as an estimate of the age of the universe. Simultaneous measurement of several helium emission lines with two independent telescope/spectrograph configurations allow us ⦠Download PDF. Our models show that the helium ionization correction factor (ICF) can be nonnegligible for nebulae excited by stars with eÆective temperatures larger than 40,000 K. Furthermore, we ând that when the eÆective temperature rises to above 45,000 K, the ICF can be signiâcantly negative. Recent Estimates of the Primordial Helium Abundance Eric Mamajek (UR) Last updated: 15 November 2010 Summary I've reviewed the literature since 1990 regarding estimates of the primordial He abundance (Y p; 4 He specifically). helium abundance is 2 l to 30% by mass. Its boiling and melting points are the lowest among the elements and it exists only as a gas except in extreme conditions . By continuing to use this site you agree to our use of cookies. The most common way to determine Y p is the analyses of observations of metal-poor H ii regions found in blue compact dwarf galaxies. Helium-3 is a light, stable isotope of helium with two protons and one neutron. We conducted a long-slit spectrophotometry analysis to obtain the chemical abundances of seven metal-poor HII regions in three galaxies: UM 160, UM 420, and TOL 0513-393. In the standard Big Bang model, the light elements in the cosmos -hydrogen and helium but also deuterium and lithium- were created in the very early Universe. We calculate a linear fit to these measurements, accounting for intrinsic scatter, and report a new determination of the primordial helium number abundance, y_P = 0.0805+/-0.0017, which corresponds to a primordial helium mass fraction Y_P = 0.2436+/-0.0040. Big Bang nucleosynthesis predicts a primordial abundance of about 25% helium-4 by mass, irrespective of the initial conditions of the universe. Primordial helium was estimated for each nebula using the expression Y P = Y â ÎY ÎZ Z âÎY S where Y was derived from the helium abundance, Z was estimated from the chemical abundances, ÎY S are the helium yields from van den Hoek & Groenewegen (1997) and ÎY/ÎZ =2.0±0.6 was taken from Peimbert et al. In this paper we present a new determination of Yp based on observations of the metal poor extragalactic H ii regions NGC 346, I Zw 18, and NGC 2363. The determination of the pregalactic, or primordial, helium abundance by mass Yp is paramount for the study of cosmology, the physics of elementary particles, and the chemical evolution of galaxies. Full Record; Other Related Research We derived the physical conditions and the chemical abundances of N, O, Ne, S, Ar, and ⦠THE PRIMORDIAL HELIUM ABUNDANCE AND THE NUMBER OF NEUTRINO FAMILIES A. Peimbert,1 M. Peimbert,1 and V. Luridiana2,3 Received June 8 2016; accepted July 26 2016 RESUMEN Basados en observaciones de regiones HII y en los nuevos c´alculos de los coeï¬-cientes de recombinaci´on de las l´Ä±neas de HeI debidos a Porter et al. Primordial chemistry: an overview. The primordial helium abundance from observations of extragalactic H II regions B. E. J. Pagel, B. E. J. Pagel 1 NORDITA, Blegdamsvej 17, DK-2100 Copenhagen Ø, Denmark. Helium-3 was discovered in 1939. Such observations 3 have confirmed that the primordial abundance of helium-4 was 25%. Izotov and Thuan have argued that their derived value of the primordial helium abundance (Yp) is inconsistent with the value derived from WMAP assuming standard big bang nu-cleosynthesis, in the sense that their determination is too high by two sigma. E. A. Simonson, The U.S. Department of Energy's Office of Scientific and Technical Information Title: A new determination of the primordial helium abundance using the analyses of HII region spectra from SDSS Authors: O.A. We derived the physical conditions and the chemical abundances of N, O, Ne, S, Ar, and Cl. The calculated value, $Y_{P,\,S}=0.244\pm0.006$, is in good agreement with the estimate from the Planck experiment, as well as, determinations in the literature using oxygen as the metallicity tracer. Full Record; Other Related Research; Abstract. Current measures ob The value of the primordial helium abundance as a constraint on the age of the universe is discussed emphasizing the age of the oldest stars as an estimate of the age of the universe. Our result indicates that it is premature to emphasize a discrepancy. Our models show that the helium ionization correction factor (ICF) can be nonnegligible for nebulae excited by stars with eective temperatures larger than 40,000 K. Download Full PDF Package. S. Parfenov. the basis for measuring the primordial helium abundance. lium abundance by mass, Y, of different objects and in the accuracy of the predictions of the primordial helium abundance by unit mass, YP (also known as the primordial helium mass fraction), by Big Bang Nucleosynthesis (BBN) has led to a better understanding of the universe. The Astrophysical Journal, 2007. Andrey Tsivilev. We present a new determination of the primordial helium mass fraction Yp , based on 93 spectra of 86 low-metallicity extragalactic H II regions, and taking into account the latest developments concerning systematic effects. The abundance of the chemical elements is a measure of the occurrence of the chemical elements relative to all other elements in a given environment. I will review recent progress on the observational determination of the primordial helium abundance (Yp). Primordial nucleosynthesis occurred very early in the history of the Universe, resulting in some helium and small traces of lithium and deuterium, the heavy isotope of hydrogen. We have derived a primordial helium abundance of Y p = 0.2477 ± 0.0029, based on new atomic physics computations of the recombination coefficients of He I and of the collisional excitation of the H I Balmer lines together with observations and photoionization models of metal-poor extragalactic H II regions. ABSTRACT. This site uses cookies. To find out more, see our Privacy and Cookies policy. Other isotopes including 2 H, 3 H, 3 He, 6 Li, 7 Li, and 7 Be are much rarer; the estimated abundance of primordial lithium is 10 â10 relative to hydrogen. My research is on the Primordial Helium Abundance. It would be very interesting to compare the helium abundances in Fig. If such fluctuations occur in the low metallicity, extragalactic H II regions used to probe the primordial helium abundance, the derived 4He mass fraction, YP, could be systematically different from the true primordial value. The Primordial Helium Abundance: Systematic Effects and a New Determination. There has been a dispute about the actual primordial helium abundance in the Universe: either 23.4 or 24.4 percent by mass, with both broups claiming 0.2 percent accuracy so this is 5 sigma discrepancy between the different observational camps. Determination of the primordial helium abundance from radio recombination line observations. [10 pts Primordial Nucleosynthesis (i) 5 pts| Show that the primordial abundance of helium by mass is where np/nn is the ratio (by number) of protons to neutrons, if all the baryons ar e in H and He Hint: The abundance of helium by mass is He mHe where n is the number density and m is the mass. Helium-3 occurs as a primordial nuclide, escaping from Earth's crust into its atmosphere and into outer space over millions of years. Kislitsyn , V.V. In physical cosmology, Big Bang nucleosynthesis (abbreviated BBN, also known as primordial nucleosynthesis, archeonucleosynthesis, archonucleosynthesis, protonucleosynthesis and paleonucleosynthesis) is the production of nuclei other than those of the lightest isotope of hydrogen (hydrogen-1, H, having a single proton as a nucleus) during the early phases of the Universe. Using our determination of the primordial helium abundance in combination with the latest primordial deuterium measurement, (D/H)_P x 10^5 =2.527+/-0.030, we place a bound on the baryon density Omega_bh^2 = 0.0215+/-0.0005 and the effective number of neutrino species Neff = ⦠This is the long-sought primordial helium, one of the two original chemical elements (the even more abundant hydrogen being the other) from which ⦠It is concluded that the galactic H II regions may not be suitable for determining the primordial He abundance, based on currently available data and theoretical modelling. According to the big bang model, nuclear reactions in the first few minutes after the big bang produced the three lightest elements: hydrogen, helium, and lithium. The resulting estimate of the primordial helium abundance, YP = 0.228 0.005 (s.e. The primary uncertainty in the globular cluster technique is that of the starting helium abundance. Helium is the most common element in the universe after hydrogen, with a mass fraction of about 24%. YP is determined by means of an extrapolation to Z = 0 The Universe's light-element abundance is another important criterion by whichthe Big Bang hypothesis is verified. We use a sample of 45 low-metallicity H II regions in blue compact dwarf (BCD) galaxies to determine the primordial helium abundance YP with a precision better than 5%. (2007). S. Parfenov. This site uses cookies. Measurements of 4He in metal-poor extragalactic H ii regions: the primordial Helium abundance and the ÎY/ÎO ratio - Volume 5 Issue S268 The American Astronomical Society (AAS), established in 1899 and based in Washington, DC, is the major organization of professional astronomers in North America. WHT and Calar Alto 3.5m double spectrograph observations of the very low metallicity galaxy SBS 0335-052 are presented. Such observations 3 have confirmed that the primordial abundance of helium-4 was 25%. The fit is good but not perfect. 1979). Much later, stars produced all the other elements, including the carbon upon which all life is based, the nitrogen and oxygen in the air we breathe, the calcium in our bones, and the iron in our blood. Free PDF. Upload an image to customize your repositoryâs social media preview. Helium-3 is also thought to be a natural ⦠Recent Estimates of the Primordial Helium Abundance Eric Mamajek (UR) Last updated: 15 November 2010 Summary I've reviewed the literature since 1990 regarding estimates of the primordial He abundance (Y p; 4 He specifically). The Primordial Helium-4 Abundance The post-BBN evolution of 4 He is quite simple. For the purposes of stellar nucleosynthesis calculations that require a primordial He abundance (for metal fraction Z = 0), I adopt the predicted ⦠CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): A reanalysis is made for the helium abundance determination for the Izotov-Thuan (2004) spectroscopic sample of extragalactic H II regions. Nevertheless, accurate determination of the primordial helium abundance from observations of H II regions is constrained by both systematic and statistical uncertainties. We apply a recently developed theoretical model of helium emission to observations of both the Orion Nebula and a sample of extragalactic H II regions. We conducted a long-slit spectrophotometry analysis to obtain the chemical abundances of seven metal-poor HII regions in three galaxies: UM 160, UM 420, and TOL 0513-393. This paper contains results of a calculation of the He3, He', and deuterium abundances produced in the early stages of expansion of the Universe. Astronomy Letters, 2009. Kurichin , P.A. Primordial helium abundance and uncertainties The calculations presented here provide a grid of emission coefficients as a function of density and temperature. Consideration of possible sources of scatter ⦠We report progress on observational and theoretical work related to a more accurate determination of the primordial helium abundance. We present the spectroscopic sample of 100 H ii regions collected from the Sloan Digital Sky Survey. or. Limits to the primordial helium abundance in the baryon-inhomogeneous big bang The parameter space for baryon inhomogeneous big bang models is explored with the goal of determining the minimum helium abundance obtainable in such models while still satisfying the other light-element constraints. The precision measurement of the primordial helium abundance Y p is a powerful probe of the early Universe. Hydrogen-Helium Abundance. Carroll & Ostlie give 23 to 24% helium. There is a window of uncertainty, but it is clear that hydrogen and helium make up 98% plus of the ordinary matter in the universe. This high percentage of helium argues strongly for the big bang model, since other models gave very small percentages of helium. ⦠Last July Dr. Peter Jacobsen, an astronomer with the European Space Agency, reported finding some evidence for the primordial helium in observations by the Hubble Space Telescope. But he was unable to measure the amount, and he and other astronomers felt the results were inconclusive. Keith MacAdam. However, efforts to determine the primordial helium abundance via observations of metal poor H II regions have been limited by significant uncertainties (compared with the value inferred from BBN theory using the CMB determined value of the baryon density). This "Schramm plot" depicts primordial abundances of 4 He, D, 3 He, and 7 Li as a function of cosmic baryon content from standard BBN predictions. Its membership of We study the effect that the temperature structure has on the determination of the primordial helium abundance, Yp. The measured elemental abundances of metal poor stars indicate that the distribution of heavy elements from the big bang may not be what current theory predicts. Gary Ferland. primordial helium abundance effective temperature data result low-metallicity hii region nebula form izotov thuan nonnegligible icfs stellar atmosphere slight increase selection criterion helium ionization correction factor hii region metallicity dependent small icf metallicity independent criterion photoionization model fit line present result ), is unchanged from what has been derived previously, but the dY/dZ slope is still remarkably large, about 4, and in significant disagreement with what had been theoretically predicted for ⦠To find out more, see our Privacy and Cookies policy. The primary uncertainty in the globular cluster technique is that of the starting helium abundance. Observations of metal-poor extragalactic H II regions allow the determination of the primordial helium abundance, Y_p. If the average mass density in the universe were a factor of 30 below the accepted estimate of the mass in galaxies, it would lead to a much lower primeval helium abundance. OSTI.GOV Journal Article: The primordial abundance of {sup 4}He: An update. CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): The primordial abundance of 4 He, YP, is one of the hottest themes in present-day astronomy, mostly due to its cosmological relevance. The primordial helium abundance $Y_P$ is calculated using sulphur as metallicity tracer in the classical methodology (with $Y_P$ as an extrapolation of $Y$ to zero metals). That hydrogen began to combine, too, slowly forming stars and galaxies out of the cosmic primordial soup. ADS. Measurements of the abundance gradient across a galactic disk indicate that the He+/H+ ratio changes within 7 kpc of galactic centers, where metallicity could increase. We present new high-quality spectrophotometric observations of 27 supergiant H II regions in 23 low-metallicity blue compact galaxies (BCGs) with oxygen abundance 12 + log (O/H) between 7.22 and 8.17 (Z â /50 <= Z <= Z â /6), most of which ⦠Tests of big bang nucleosynthesis and early universe cosmology require precision measurements for helium abundance determinations. The boiling and freezing points of helium are lower than those of any other known substance. On determining the primordial helium abundance from the spectra of H II galaxies A data set of 53 H II galaxies and giant H II regions whose observed abundances have reliable formal uncertainties reveals that the O/H-He/H relation used to determine the primordial helium abundance (PBA) has a highly significant physical dispersion. We have analyzed the correction for the ionization structure of W51, obtained an actual abundance of helium in the range y = (8.9â9.7)%, and determined its primordial abundance Y p (produced during primordial nucleosynthesis in the Universe) in this source. Download with Google Download with Facebook. Abundance is measured in one of three ways: by the mass-fraction (the same as weight fraction); by the mole-fraction (fraction of atoms by numerical count, or sometimes fraction of molecules in gases); or by the volume-fraction. We present results from photoionization models of low-metallicity H II regions. The primordial helium abundance determination requires the analysis of young, low metallicity, and relatively high excitation nebulae, which contain a negligible or small amount of neutral helium. OSTI.GOV Journal Article: Primordial chemistry: an overview. We demonstrate a correlation between equivalent width and apparent helium abundance of lines from extragalactic sources that is most likely due By continuing to use this site you agree to our use of cookies. Using the same dataset, Izotov and Thuan have argued that their derived value of the primordial helium abundance (Y_p) is inconsistent with the value derived from WMAP assuming standard big bang nucleosynthesis, in the sense that their determination is too high by two sigma. Hydrogen-1 is the most abundant nuclide, comprising roughly 92% of the atoms in the Universe, with helium-4 second at 8%.
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