Order and Chaos in the Local Disc Stellar Kinematics Induced by the Galactic Bar

By R. Fux. 2001

166 citations recorded by the source corpus.

The Galactic bar causes a characteristic splitting of the disc phase space into regular and chaotic orbit regions which is shown to play an important role in shaping the stellar velocity distribution in the Solar neighbourhood. A detailed orbital analysis within an analytical 2D rotating barred potential reveals that this splitting is mainly dictated by the value of the Hamiltonian H and the bar induced resonances. In the u v velocity plane at xed space position, the contours of constant H are circles centred on the local solid rotation velocity of the bar frame and of radius increasing with H. For reasonable bar strengths, the contour H = H12 corresponding to the eective potential at the Lagrangian points L1=2 marks the average transition from regular to chaotic motion, with the majority of orbits being chaotic at H>H 12. On top of this, the resonances generate an alternation of regular and chaotic orbit arcs opened towards lower angular momentum and asymmetric in u for space positions away from the principal axes of the bar. Test particle simulations of exponential discs in the same potential and a more realistic high-resolution 3D N-body simulation reveal how the decoupled evolution of the distribution function in the two kind of regions and the process of chaotic mixing lead to overdensities in the H > H12 chaotic part of the disc velocity distributions outside corotation. In particular, for realistic space positions of the Sun near or slightly beyond the outer Lindblad resonance and if u is dened positive towards the anti-centre, the eccentric quasi-periodic orbits trapped around the stable x1(1) orbits { i.e. the bar-aligned closed orbits which asymptotically become circular at larger distances { produce a broad u H 12 zone, whereas the corresponding u > 0 region appears as an overdensity of chaotic orbits forced to avoid that arc. This chaotic overdensity provides an original interpretation, distinct from the anti-bar elongated quasi-periodic orbit interpretation proposed by Dehnen (2000), for the prominent stream of high asymmetric drift and predominantly outward moving stars clearly emerging from the Hipparcos data. However, the most appropriate interpretation for this stream remains uncertain. The eects of spiral arms and of molecular clouds are also briefly discussed within this context.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/9149e6e39af4289fc29d171a787b579629ecb00a

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Citations in the corpus

The Milky Way’s stellar disk (2013, background): “On the one hand, the spiral arms and the Galactic bar are manifest non-axisymmetric features, with clear signatures also in the Solar neighborhood (e.g., Dehnen 1998, 2000; Fux 2001; Quillen 2003; Quillen & Minchev 2005).”
Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data: Revisiting the concept of superclusters (2004, background): “Chereul & Grenon (2001) proposed that the Hyades supercluster represents in fact an extension of the Hercules stream, but the LM method has shown that the two features are clearly separated in theUV-plane.”
Constraining the Milky Way assembly history with Galactic Archaeology (2016, background): “The numerical work of Dehnen (1999, 2000); Fux (2001); Minchev et al. (2010), and more recently Antoja et al. (2012), has shown that this stream can be explained as the effect of the Milky Way central bar if the Sun is placed just outside the 2:1 Outer Lindblad Resonance (OLR).”
The lifetimes of spiral patterns in disc galaxies (2010, background): “Individual features in this distribution have been attributed to resonances with the bar (Raboud et al. 1998; Dehnen 2000; Fux 2001), or with a spiral pattern (Quillen & Minchev 2005; Sellwood 2010b), while other models include both bars and spirals (Quillen 2003; Chakrabarty 2007; Antoja et al.…”
The stellar velocity distribution in the solar neighbourhood (2003, background): “…by massive compact halo objects or halo substructure (Lacey & Ostriker 1985), mergers with dwarf galaxies (Tóth & Ostriker 1992; Walker, Mihos & Hernquist 1996; Huang & Carlberg 1997), or the outer Lindblad resonance from the Galactic bar (Kalnajs 1991; Dehnen 1999, 2000; Fux 2001; Quillen 2003).”