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Astron. Astrophys. 336, 130-136 (1998)

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Archer of the Galactic disk? The effect on the outer H Idisk of the Milky Way of collisional encounters with the Sagittarius dwarf galaxy

R.A. Ibata and A.O. Razoumov

Department of Physics & Astronomy, University of British Columbia, 2219 Main Mall, Vancouver, B.C., V6T 1Z4, Canada (surname@astro.ubc.ca)

Received 30 September 1997 / Accepted 12 May 1998


Hydrodynamical calculations undertaken to simulate the collisional interaction between the Sagittarius dwarf and the Galactic outer H Idisk are presented, constrained by recently derived orbital and mass parameters for this dwarf galaxy. It is found that a significant distortion to the structure of the Galactic H Idisk will be induced by the collision if the mass of the dwarf exceeds [FORMULA]; this value is consistent with an estimate derived by requiring that the dwarf galaxy is sufficiently robust to survive tidal disruption until the present time. Though the precise details of the interaction are compromised in our simulations by the lack of a live Galactic halo, we find that for model masses [FORMULA], prominent spiral arms and a substantial lopsidedness in the outer disk are produced. Furthermore, a noticeable warp-like structure is induced in the disk. Thus the Sagittarius dwarf may have significantly affected the star formation history and structure of the outer Galaxy. These simulations confirm the possibility of determining the current merging rate of low surface brightness, gas-poor dwarf galaxies of mass [FORMULA] onto giant spiral galaxies from careful analysis of observations of the structure of H Idisks.

Key words: methods: N-body simulations – Galaxy: kinematics and dynamics – Galaxy: structure – galaxies: individual: Sagittarius dwarf – galaxies: interactions

Present address: European Southern Observatory, Karl-Schwarzschild Straße 2, D-85748 Garching bei München, Germany

Send offprint requests to: R.A. Ibata

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© European Southern Observatory (ESO) 1998

Online publication: July 7, 1998