KINEMATICS OF AN ANTICENTER STREAM TRIBUTARY IN KAPTEYN'S SELECTED AREA 76

摘要

We have measured 3-D kinematics of stars in Kapteyn's Selected Area (SA) 76 that were selected to be Anticenter Stream (ACS) members on the basis of their kinematics and CMD positions. Mean stream kinematics from the 31 identified ACS members produce an orbit inclined by ～30° to the well-defined spatial distribution of the stream. We have explored possible explanations for this, and suggest that our data in SA 76 are measuring the motion of a kinematically cold sub-stream among the ACS debris, which was likely a fragment of the same infalling structure that created the larger ACS system.