AAS 195th Meeting, January 2000
Session 5. Looking Towards The Galactic Center
Display, Wednesday, January 12, 2000, 9:20am-6:30pm, Grand Hall

[5.05] A Study of the Distribution of Galactic Scattering Material in the Longitude Range 30\circ \le l \le 75\circ

J. F. Salgado (University of Michigan), C. J. Salter, T. Ghosh (NAIC/Arecibo Obs.), W. Junor (Univ. of New Mexico), P. K. Manoharan (Radio Astronomy Centre, TIFR)

Using multi-frequency VLBA and MERLIN observations of 32 compact radio sources within 30\circ \le l \le 75\circ, \mid b\mid\,\le 3\circ, we test suggestions that the distribution of Galactic electron-density fluctuations contains a spiral component. We derive Scattering Measure (SM = \int0s CN2(s\prime) \, ds\prime) values and limits from source sizes obtained via \lambda 18-cm images. Lines of sight in this longitude range pass from the Sagittarius Arm, through an interarm region, into the Orion Arm, and large changes in the distribution of SM are expected if spiral structure is present in the electron-density fluctuations. Results indicate such effects. These measurements further constrain the parameters in the CN2 distribution model by Ghosh & Rao (1992). New best-fit parameters for this model are presented.