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With a goal toward deriving the physical conditions in external galaxies, wepresent a survey of the formaldehyde emission in a sample of starburst systems.By extending a technique used to derive the spatial density in star formationregions in our own Galaxy, we show how the relative intensity of the1(10)-1(11) and 2(11)-2(12) K-doublet transitions of H2CO can provide anaccurate densitometer for the active star formation environments found instarburst galaxies. Relying upon an assumed kinetic temperature and co-spatialemission and absorption from both H2CO transitions, our technique is applied toa sample of nineteen IR-bright galaxies which exhibit various forms ofstarburst activity. In the five galaxies of our sample where both H2COtransitions were detected we have derived spatial densities. We also use H2COto estimate the dense gas mass in our starburst galaxy sample, finding similarmass estimates for the dense gas forming stars in these objects as derivedusing other dense gas tracers. A related trend can be seen when one comparesL_IR to our derived n(H2) for the five galaxies within which we have derivedspatial densities. Even though our number statistics are small, there appearsto be a trend toward higher spatial density for galaxies with higher infraredluminosity. This is likely another representation of the L_IR-M_densecorrelation.

Formaldehyde Densitometry of Starburst Galaxies