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Session 105 - Pre-Main Sequence Binaries and Disks.
Display session, Thursday, January 18
North Banquet Hall, Convention Center
Star formation occurs by gravitational collapse of clumps of dense, cold gas and dust, embedded with magnetic fields. All current theories predict the formation of a disk early in the gravitatinal collapse phase, under various conditions. Mid-IR polarimetric studies found mostly toroidal disk magnetic fields, whereas Extreme-IR polarimetric studies found mostly poloidal disk magnetic fields. Observations (compiled here) show that when disks are in relative isolation they generally have an E-vector perpendicular to the disk elongation, and that when disks have a gaseous companion object nearby they generally have an E-vector parallel to the disk elongation. Using the usual interpretation, with the B-vector perpendicular to the E-vector (model of Davis-Greenstein), we find that when disks are in relative isolation, they generally have a toroidal magnetic field (B parallel to the disk elongation), and that when disks have a a gaseous companion objetc nearby they generally have a poloidal magnetic field (B perpendicular to the disk elongation). A possible interpretation could be that, on average, an accompanying source can delay or prolong the life of the envelope/cocoon of the primary disk through tidal interaction, ie the gravitational attraction by the companion object on the gas originally infalling onto the primary object may be to cause a drifting of the infalling gas away from the primary object at first. It may thus take a longer time for this infalling gas to finally arrive on the primary object, owing to the moving disturbance of the orbiting companion object, as compared to the lifetime of an envelope for an isolated disk.
