| Description |
Edge-on spiral galaxies are a unique perspective on the vertical structure of spiral disks, both stars and the iconic dark dustlanes. The thickness of these dustlanes can now be resolved for the first time with Herschel in far-infrared and sub-mm emission.Resolved far-infrared and sub-mm observations of edge-on spirals will impact on several current topics. First and foremost, these Herschel observations will settle whether or not there is a phase change in the vertical structure of the ISM with disk mass. Previously, a dramatic change in dustlane morphology was observed as in massive disks the dust collapses into a thin lane. If this is the case, the vertical balance between turbulence and gravity dictates the ISM structure and consequently star-formation and related phenomena (spiral arms, bars etc.). We specificaly target lower mass nearby edge-ons to complement existing Herschel observations of high-mass edge-on spirals. Secondly, the combined data-set, together with existing Spitzer observations, will drive the generation of spiral disk Spectral Energy Distribution models. These model how dust reprocesses starlight to thermal emission but the dust geometry remains the critical unknown. And thirdly, the observations will provide an accurate and unbiased census of the cold dusty structures occasionally seen extending out of the plane of the disk, when backlit by the stellar disk. We ask for priority one for the remaining 8.9 hours of PACS and SPIRE observations of low- and intermediate-mass disks complement slated Herschel observations of massive edge-on spirals and existing Spitzer observations in the near-infrared. |
