The SWS survey for rotational H2 lines in late-type galaxies. Observations of the central regions of NGC 6946
Valentijn E.A., van der Werf P.P., de Graauw T., de Jong T.
Abstract:
We report the first extragalactic detection of the pure rotational H2 S(0) and S(1) lines at 28.2 and 17.0 
m in the central 130pc molecular complex of the nearby Scd galaxy NGC 6946. We deduce a temperature of this gas component of 170K and a mass of 5x106M
for an ortho/para ratio of 3, corresponding to the ratio of statistical weights. The warm gas is confined to a ~5" (135pc) diameter region where a moderate nuclear starburst accounts for the elevated
temperature. Depending on the assumed CO/H2 conversion factor, the warm component contains of the order of 5-10% (with formal lower and upper limits of 2 and 20%) of the total molecular mass in this region. CO data had indicated the presence of this warm gas, but did not provide a mass measurement. The ISO results can fully account for the warm component indicated by the CO data. The CO/H2 conversion factor for the 12CO J=1-0 line is not strongly affected by the
presence of the warm component.
Keywords:
galaxies: individual: NGC 6946 - galaxies: ISM
Full text (compressed)
[ ISO Home Page | Astronomy and Astrophysics Page ]