A study of small diffuse nebulae

Ten small galactic H II regions have been studied by filter photometry at the Prairie Observatory of the University of Illinois and with the Harvard Scanner at Kitt Peak National Observatory. Absolute H..cap alpha.. and H..beta.. fluxes were determined for all 10, and fluxes in the (O II) lambda3727, (O II) lambda7324, (O III) lambdalambda5007+4959, and (N II) lambdalambda6584+6548 lines were also obtained. Extinction constants were calculated from H..cap alpha../H..beta.. ratios, and also from radio/H..beta.. ratios when possible. Differences between the optical extinctions and the radio extinctions are found for six of the eight regions with known radio fluxes; the observed differences can be explained by local dust. Electron temperatures from (O II) are found to lie within the range 5000--7500 K, but these temperatures should be regarded as lower limits to the actual (O II) electron temperatures. Nitrogen to oxygen ratios were calculated for all of the regions, and the average value of the nitrogen to oxygen radio lies at the lower end of the range of values found by other observers for H II regions.