Primordial helium, spectrophotometric technique, and I Zwicky 18

Details Primordial helium, spectrophotometric technique, and I Zwicky 18 Primordial helium, spectrophotometric technique, and I Zwicky 18

Jul 1985

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1985apjs...58..321d&link_type=abstract

Astrophysical Journal Supplement Series (ISSN 0067-0049), vol. 58, July 1985, p. 321-340.

Astronomy and Astrophysics

Astrophysics

133

Abundance, Cosmology, Dwarf Galaxies, Helium, Nuclear Fusion, Spectrophotometry, Data Reduction, Emission Spectra, Error Analysis, Interstellar Extinction, Nebulae, Radiant Flux Density, Spectral Line Width

Scientific paper

Emission-line observations of the dwarf galaxy I Zw 18 were obtained in order to calculate the primordial helium mass fraction Yp. The observations were carried out during five nights in February 1982, using the KPNO 2.1-meter telescope attached to a gold spectrograph and intensified image dissector scanner (IIDS). A mass fraction of 0.122 + or - 0.015 is derived on the basis of the relative line intensities, H-beta fluxes, and equivalent line widths of I Zw 18. It is shown that the estimated standard error of Yp is more realistic than errors predicted in previous studies. The relative line intensities, H-beta fluxes, and equivalent line widths are given in a table.

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