Formation of the Small Magellanic Cloud: ancient major merger as a solution to the kinematical differences between old stars and HI gas

Abstract

Recent observations of the Small Magellanic Cloud (SMC) have revealed that the HI gas shows a significant amount of rotation (V_c 60 km/s), while no or little rotation is evident for the old stellar populations. We suggest that this unique kinematical difference between these components in the SMC can be caused by a major merger event which occurred in the early stage of the SMC formation. Our simulations show that dissipative dwarf-dwarf merging can transform two gas-rich dwarf irregulars into a new dwarf, which consists of a spheroidal stellar component and a rotating extended HI disk. The remnant of this dwarf-dwarf merging shows significantly different kinematics between stars and gas, in the sense that a gas disk rotates rapidly while a stellar component shows little rotation. We thus suggest that the simulated dwarf having a dynamically hot spheroid and an extended gas disk finally evolves into the present SMC after efficient stripping of the outer gas via tidal fields of the Galaxy and the Large Magellanic Cloud. We also suggest that spatial distributions and kinematics of RGB and AGB stars with different ages in the possible spheroidal component of the SMC can provide valuable information on whether and when a past major merger event really occurred in the SMC.

13 pages, 4 figures (three color), ApJL in press

References in corpus (18)

• Star Formation in Galaxies Along the Hubble Sequence
• The Structure of Dark Matter Haloes in Dwarf Galaxies
• A New Look at the Kinematics of Neutral Hydrogen in the Small Magellanic Cloud
• The influence of gas on the structure of merger remnants
• Spectroscopic Survey of Red Giants in the SMC. I: Kinematics
• Formation and evolution of the Magellanic Clouds. I.Origin of structural, kinematical, and chemical properties of the Large Magellanic Cloud
• AGB stars in the Magellanic Clouds. II. The rate of star formation across the LMC
• Formation of a polar-ring galaxy in a galaxy merger
• Dwarf Galaxies Also Have Stellar Halos
• ESO215-G?009: An Extreme HI-Rich Dwarf Irregular Galaxy
• The Magellanic Squall: Gas Replenishment from the Small to Large Magellanic Cloud
• High Resolution HI Observations of the Galaxy NGC404: a dwarf S0 with abundant Interstellar gas
• The spatial and age distribution of stellar populations in DDO 190
• Impact of dark matter subhalos on extended HI disks of galaxies: Possible formation of HI fine structures and stars
• Deep Optical Imaging of Starbursting "Transition" Dwarf Galaxies
• C stars in the outer spheroid of NGC 6822
• The Origin of Large-scale HI structures in the Magellanic Bridge
• The size and structure of the spheroid of IC 1613

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