Three hydrogen recombination lines, H90alpha , H92alpha , and H109alpha have been observed with the Australia Telescope Compact Array toward the 30 Doradus Nebula, the giant HII region in the Large Magellanic Cloud. Emphasis is placed on the more sensitive H90alpha observations which also include the He90alpha and H113beta lines. The distributions of radial velocity and electron temperature have been mapped across the source. The heliocentric velocity of the ionized gas varies between 260 km/s and 300 km/s with a mean value of 280 km/s. In some places the line is double, suggesting that pieces of one of more expanding shells are being seen. The mean (LTE) electron temperature is 15000K with a range of +/-3500K. The beta /alpha ratio across most of the source is close to the expected LTE value of 0.28, but in some small regions has been determined to be as low as 0.17+/-.04. Where the helium abundance, Y(+) = [n(He)]/[n(H)], can be determined, it varies from 0.07+/-.01 to 0.14+/-.02, compared to a typical solar value of 0.1.
American Astronomical Society Meeting Abstracts #188
- Pub Date:
- May 1996