GALACTIC STRUCTURES ASSOCIATED WITH EXTREME SCATTERING EVENTS IN THE RADIO LIGHT CURVES OF NRAO 140, 0954+658, AND 2352+495

Of the nine quasars whose radio light curves contain suspected extreme scattering events (ESEs), we find that the lines of sight toward three of them (NRAO 140, 0954+658, and 2352+495) pass through the edges of clearly identifiable Galactic structures seen at IR wavelengths and in 21 cm continuum emission. These structures are possible sites for enhanced turbulence in the electron column density distribution which, through diffractive or refractive propagation effects, may be responsible for the unusual flux density variations we denote as an ESE. Of the remaining six sources whose light curves display an ESE, four (0133+476, 0300+470, 1749+096, ana 1821+107) appear near the edges of 100 mum IR clumps in the Galactic foreground and two (1502+106 and 1611+343) are 1-degrees-2-degrees from the nearest clump. We suggest that the shell-like object, observed in projection against NRAO 140, may be a very old nova remnant.