Gas/Star Offsets in Tidal Debris
(Mihos, ApJ, 2000)

The curious case of Arp 299:
  • Stars and gas in tidal debris are seperated by ~ 10 kpc along the spine of the tidal tail.
  • Gas seems to lead the stellar tail!
Not seen in the simulations, eg (Mihos & Hernquist 1996):



Green: optical starlight
Blue: HI gas
(from Hibbard & Yun 1999)



Visualizing the IMAX Simulation


Exponential Gas + Stars
 Extended Outer HI Disk



What's up? Different mass distributions lead to different angular momentum distributions. Gas is drawn from preferentially further out in the disks and has higher specific angular momentum than the stars. It ends up leading.