New Surveys of Star-Forming Regions: Spitzer and XMM-Newton

The Taurus Molecular Cloud (TMC) is the pivotal nearby star formation region with which essentially all theories of low-mass star formation have been tested. It contains the nearest sample of forming Class 0 and Class I protostars that have been investigated in detail; it shows some of the best-studied accretion disks and some of the finest protostellar jets.

We have used XMM-Newton in an exceptionally large project to survey the Taurus region at unprecedented depth in X-rays in the framework of the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST), using 170 hrs of observing time for about 20 deep exposures in the densest areas of the Taurus region, plus further 190 hrs from the archive (PI M. Güdel, with an international team of 30 astronomers, see left Figure for an overview of the spatial coverage); more recently, the Spitzer Space Telescope scanned the entire cloud area, about 45 sq. degrees during 200 hours in all photometric bands (PI = D. Padgett/Caltech; M. Güdel leading joint IR/X-ray studies) for a project now defined as a Spitzer legacy program. Both surveys have been accompanied by deep optical and near-infrared surveys conducted with the Canada-France-Hawaii telescope. The XEST project has recently been published in a special issue of the Astronomy & Astrophysics journal (June 2007), accompanied by press releases by ESA and A&A.

The Spitzer Taurus survey covers a total of of 45 sq. degrees. The figure on the right shows the large-scale maps. These maps provide a complete view of the mid-IR dust distribution across the Taurus clouds. Note the filamentary structure in the 160μm map. Important results have been obtained for the brown dwarf (BD) sample; about half of the BDs reveal an infrared excess, indicative of the presence of circumstellar disks (published in Guieu et al. 2007, see Fig. below, showing Spitzer IR SEDs). A cross-correlation between disk properties and XEST results is in progress.