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Session 89 - Star-forming Galaxies.
Oral session, Friday, January 09
International Ballroom East,
New observations of molecular hydrogen emission in the near-IR K band are presented for two extragalactic star-forming regions: the starburst galaxy NGC253 and the giant HII regions NGC5461 in M101. In both cases we describe the evidence which indicates that the dominant excitation is by UV photons and not by shocks. In NGC253 our evidence is based on the value of the H_2 ortho/para ratio which, together with the line excitation, argues for radiative excitation in dense gas. In NGC5461 we detect emission from the V=2 and v=3 ro-vibrational series which demonstrate unambiguously the gas to be UV-excited and that the gas density is low.
