Discovery of radiatively excited molecular hydrogen in the giant extragalactic HII region complex NGC 604

Israel, F.P.; Hawarden, T.G.; Wade, R.S.; Geballe, T.R.; Dishoeck, E.F. van (1989)

Article / Letter to editor

The 1-0S(1), 2-1S(1), 1-0S(0) and 1-0Q branch transitions of molecular hydrogen (H2) towards the giant emission nebula (HII region) NGC 604 in M33 have been detected. The line ratios are incompatible with shock-excited H2, but indicate the widespread presence of fluorescent H2 at a mean temperature T = 70 + or - 15 K. This is the first detection of fluorescent H2 emission associated with a giant (extragalactic) HII region complex.

• H II regions
• hydrogen
• molecular excitation
• nebulae
• line spectra
• ultraviolet radiation

• All authors: Israel, F.P.; Hawarden, T.G.; Wade, R.S.; Geballe, T.R.; Dishoeck, E.F. van
• Date: 1989
• Publisher: Royal Astronomical Society