Previous
abstract 
Next
abstract
M74 (NGC 628) is an ScI galaxy which is viewed nearly face-on with many well-defined \hii regions. We report individual UV fluxes of over 160 \hii regions in M74, as imaged by the Ultraviolet Imaging Telescope during the Astro-1 mission in December, 1990. We compare the \hii region fluxes in the near-UV (2490 \AA) and far-UV (1520 \AA) with each other and with the fluxes measured in the B, R and H$\alpha$ bands. Preliminary results indicate that emission from \hii regions directly contributes 30\% of all UV flux.
We also compare the locations and the morphologies of individual \hii emission features in the near-UV and H$\alpha$. The average displacement between an \hii region's near-UV emission peak and its H$\alpha$ emission peak is approximately 3 arcseconds and is measurably greater than the uncertainty which may be attributed to known sources of error. Because the UV image sources are generally reflection nebulae while the H$\alpha$ sources are ionized gas, this comparison gives valuable information about the relative locations of these two ISM components.
