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4 papers · 1 filter
Improving Helium Abundance Determinations with Leo P as a Case Study
Erik Aver, Danielle A. Berg, Keith A. Olive +3
Currently, the primordial helium abundance is best estimated through spectroscopic observations of H II regions in metal-poor galaxies. However these determinations are limited by…
The effects of He I 10830 on helium abundance determinations
Erik Aver, Keith A. Olive, Evan D. Skillman
Observations of helium and hydrogen emission lines from metal-poor extragalactic H II regions provide an independent method for determining the primordial helium abundance, Y_p. Tr…
The primordial helium abundance from updated emissivities
Erik Aver, Keith A. Olive, R. L. Porter +1
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…
ALFALFA Discovery of the Nearby Gas-Rich Dwarf Galaxy Leo~P. III. An Extremely Metal Deficient Galaxy
Evan D. Skillman, John J. Salzer, Danielle A. Berg +10
We present KPNO 4-m and LBT/MODS spectroscopic observations of an HII region in the nearby dwarf irregular galaxy Leo P discovered recently in the Arecibo ALFALFA survey. In both o…