Evidence for dust emission in the Warm Ionised Medium using WHAM data

Abstract

We have used the WHAM H_alpha survey and Leiden/Dwingeloo HI data to decompose the Far-infrared emission (from 100 to 1000 micron) at high Galactic latitude into components associated with the Warm Ionised Medium (WIM) and the Warm Neutral Medium (WNM). This decomposition is possible for the first time thanks to preliminary WHAM data that cover a significant fraction of the sky (about 10%). We confirm the first detection of dust emission from the WIM (Lagache et al. 1999) and show that the WIM dust temperature and emissivity are very similar to those in the WNM. The analysis suggests moreover that about 25% of the far-IR dust emission at high galactic latitude is uncorrelated with the HI gas. The decomposition again reveals a Cosmic Far-Infrared Background (CFIRB) which is determined for the first time from 100 to 1000 micron using two independant gas tracers.