An Investigation of Longitudinal Dependence of the Temperature of the Dust in the Local Interstellar Medium
Session 35 -- ISM: Abundances and Dust
Display presentation, Wednesday, June 14, 1995, 9:20am - 6:30pm

## [35.12] An Investigation of Longitudinal Dependence of the Temperature of the Dust in the Local Interstellar Medium

David R. Ciardi \& Ronald W. Canterna (University of Wyoming)

Using the $IRAS$ Sky Survey Atlas, we have investigated the spatial and temperature structure of the the local interstellar medium in the northern half of the first and second quadrants of the Galaxy ($10^{\circ} \leq b \leq 50^{\circ}$ \& $42^{\circ} \leq l \leq 146^{\circ}). The ratio of I$_{60\mu\rm{m}}$vs I$_{100\mu\rm{m}}$is found to be 0.1735 ($\pm$0.0004) indicating an average dust temperature of 24K impling that the 60$\mu\rm{m}$and 100$\mu\rm{m}$intensities are primarily produced by the thermal emission of large dust grains in thermal equilibrium with the interstellar radiation field. In addition, we have found a significant longitudinal dependence for the temperature associated with the interstellar dust. Using 1$^{\circ}\$ wide longitude bins, we find the average dust temperature varies by more than 20\% with a general gradient of decreasing temperature with increasing longitude. Further we find that the total surface brightness, in the same longitude bins, is anti-correlated with the temperature indicating that the hotter dust is associated with regions of lower dust quantity.