Meridional tilt of the stellar velocity ellipsoid during bar buckling instability

Kanak Saha*, Daniel Pfenniger, Ronald E. Taam

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


The structure and evolution of the stellar velocity ellipsoid play an important role in shaping galaxies undergoing bar-driven secular evolution and the eventual formation of a boxy/peanut bulge such as is present in the Milky Way. Using collisionless N-body simulations, we show that during the formation of such a boxy/peanut bulge, the meridional shear stress of stars, which can be measured by the meridional tilt of the velocity ellipsoid, reaches a characteristic peak in its time evolution. It is shown that the onset of a bar buckling instability is closely connected to the maximum meridional tilt of the stellar velocity ellipsoid. Our findings bring a new insight to this complex gravitational instability of the bar which complements the buckling instability studies based on orbital models. We briefly discuss the observed diagnostics of the stellar velocity ellipsoid during such a phenomenon.

Original languageEnglish (US)
JournalAstrophysical Journal
Issue number2
StatePublished - Feb 20 2013


  • Galaxy: disk
  • galaxies: bulges
  • galaxies: evolution
  • galaxies: halos
  • galaxies: kinematics and dynamics
  • galaxies: structure

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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