| Description |
We propose Herschel dual-band PACS photometry for a unique set of 31 (B8K0) stars that host on-going activity in the terrestrial planet zones, to probe for signatures of cold/outer planetesimal belts. We are interested in probing a fundamental question about planetary systemsis a two-belt structure like that of the solar system the most common outcome of planet formation? These young solar- and A-type have dust emission well characterized with Spitzer/IRS 5-35 micron spectroscopy, revealing dust regions similar in temperature to our asteroid belt and the interior zodiacal cloud (T150200 K). Because the warm belts have a median temperature of 190K, slightly warmer than that expected at the snow line, we have reason to believe that there is a common grain creation mechanism operating in the inner regions of the star-disk systems. Herschel provides the observational sensitivity at PACS 70 (or 100) micron required to successfully constrain the extent of the inner/warm dust emission, or reveal the presence of an outer/colder belt of planetesimals. In summary, the PACS observations will:1) detect the long wavelength emission of the warm/inner dust and/or establish the existence of an outer/colder planetesimal belt;2) constrain via modeling properties of the emitting dust; e.g. charateristic temperature, minimum mass and position;3) facilitate comparison of dust distributions across stellar spectral range;and 4) establish the overall architecture of the circumstellar dust, perhaps pointing to favorable regions where exoplanets may reside.We request 35.2 hours in PACS AORs using the mini-scan map mode for point-sources, selecting the blue (6085 micron) lter for most (26 of 31) targets, and the green (85125 micron) lter for 5 targets with Spitzer 70 micron detections in agreement with the short-wavelength warm-t extrapolations. |
