The Milky Way 3-Helium Abundance |
| |
Authors: | T M Bania R T Rood D S Balser |
| |
Institution: | (1) Department of Astronomy, Institute for Astrophysical Research, Boston University, 725 Commonweath Ave., Boston, MA 02215, USA;(2) Department of Astronomy, University of Virginia, Box 3818 University Station, Charlottesville, VA 22903, USA;(3) National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944, USA |
| |
Abstract: | We are making precise determinations of the abundance of the light isotope of helium, 3He. The 3He abundance in Milky Way sources impacts stellar evolution, chemical evolution, and cosmology. The abundance of 3He is derived from measurements of the hyperfine transition of 3He+ which has a rest wavelength of 3.46 cm (8.665 GHz). As with all the light elements, the present interstellar 3He abundance results from a combination of Big Bang Nucleosynthesis (BBNS) and stellar nucleosynthesis. We are measuring the
3He abundance in Milky Way H ii regions and planetary nebulae (PNe). The source sample is currently comprised of 60 H ii regions and 12 PNe. H ii regions are examples of zero-age objects that are young relative to the age of the Galaxy. Therefore their abundances chronicle
the results of billions of years of Galactic chemical evolution. PNe probe material that has been ejected from low-mass (M≤ 2M
⊙) to intermediate-mass (M∼2–5M
⊙) stars to be further processed by future stellar generations. Because the Milky Way ISM is optically thin at centimeter wavelengths,
our source sample probes a larger volume of the Galactic disk than does any other light element tracer of Galactic chemical
evolution. The sources in our sample possess a wide range of physical properties (including object type, size, temperature,
excitation, etc.). The 3He abundances we derive have led to what has been called “The 3He Problem”. |
| |
Keywords: | Cosmology: cosmological parameters The Galaxy: abundances evolution ISM: abundances evolution ii regions" target="_blank">H ii regions Stars: AGB post-AGB |
本文献已被 SpringerLink 等数据库收录! |
|