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Title: Exploring Asymmetric Substructures of the Outer Disk Based on the Conjugate Angle of the Radial Action
Abstract We use the conjugate angle of radial action (θR), the best representation of the orbital phase, to explore the “midplane,” “north branch,” “south branch,” and “Monoceros area” disk structures that were previously revealed in the LAMOST K giants. The former three substructures, identified by their 3D kinematical distributions, have been shown to be projections of the phase space spiral (resulting from nonequilibrium phase mixing). In this work, we find that all of these substructures associated with the phase spiral show high aggregation in conjugate angle phase space, indicating that the clumping in conjugate angle space is a feature of ongoing, incomplete phase mixing. We do not find theZ–VZphase spiral located in the “Monoceros area,” but we do find a very highly concentrated substructure in the quadrant of conjugate angle space with the orbital phase from the apocenter to the guiding radius. The existence of the clump in conjugate angle space provides a complementary way to connect the “Monoceros area” with the direct response to a perturbation from a significant gravitationally interactive event. Using test particle simulations, we show that these features are analogous to disturbances caused by the impact of the last passage of the Sagittarius dwarf spheroidal galaxy.  more » « less
Award ID(s):
1908653
PAR ID:
10470480
Author(s) / Creator(s):
; ; ; ; ; ; ;
Publisher / Repository:
Institute of Physics
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
956
Issue:
1
ISSN:
0004-637X
Page Range / eLocation ID:
13
Subject(s) / Keyword(s):
galaxy kinematics galaxy anticenters
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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