The Gaia inertial reference frame and the tilting of the Milky Way disk

Research output: Contribution to journalArticle

Abstract

While the precise relationship between the Milky Way disk and the symmetry planes of the dark matter halo remains somewhat uncertain, a time-varying disk orientation with respect to an inertial reference frame seems probable. Hierarchical structure formation models predict that the dark matter halo is triaxial and tumbles with a characteristic rate of similar to 2 rad H-0(-1) (similar to 30 mu as yr(-1)). These models also predict a time-dependent accretion of gas, such that the angular momentum vector of the disk should be misaligned with that of the halo. These effects, as well as tidal effects of the LMC, will result in the rotation of the angular momentum vector of the disk population with respect to the quasar reference frame. We assess the accuracy with which the positions and proper motions from Gaia can be referred to a kinematically non-rotating system, and show that the spin vector of the transformation from any rigid self-consistent catalog frame to the quasi-inertial system defined by quasars should be defined to better than 1 mu as yr(-1). Determination of this inertial frame by Gaia will reveal any signature of the disk orientation varying with time, improve models of the potential and dynamics of the Milky Way, test theories of gravity, and provide new insights into the orbital evolution of the Sagittarius dwarf galaxy and the Magellanic Clouds.

Details

Authors
Organisations
External organisations
  • Princeton University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology

Keywords

  • astrometry, cosmology: observations, Galaxy: disk, Galaxy: formation, reference systems, space vehicles: instruments
Original languageEnglish
Article number166
JournalAstrophysical Journal
Volume789
Issue number2
Publication statusPublished - 2014
Publication categoryResearch
Peer-reviewedYes