Tracing the molecular hydrogen content of the Draco nebula: very low N(H2)/W(12CO) ratios or varying FIR-emissivities?

We have analysed three complete data sets, the IRAS 100 μm intensity, I 100 , the H I column density, N(H I), and the integral of the J = 1 → 0 line of the 12 CO molecule. W( 12 CO), for the Draco nebula [= IVC G091.0 + 38.0 (VLSR = −21)] to trace the total column density of hydrogen nuclei, N(H), and to derive the extinction, A V , and the total gas mass of this nebula. Adopting the relations between these quantities which were set up by Heithausen & Mebold we have analysed the [I 100 , N(H I), W( 12 CO)]-data cube by the method of the principal component transformation. The results are tested by the statistical F- and t-tests