Milky Way — disk galaxy
Andromeda — M31
starburst — tidal shock
tidal streams — debris
dark matter halo

mass ratio M₁/M₂ = 1.0

impact param b = 0.4 R_disk

relative velocity v = 110 km/s

merger time ~4.5 Gyr

starburst SFR ×10–50 normal

approach

drag → orbit

scroll → zoom

Toomre Model
restricted 3-body
Test-particle disk। Massless stars। Live bulge+halo। N=6000 per galaxy।
Tidal Forces
F_tidal ∝ 1/r³
Differential gravity। Tidal arms form। Bridges connect cores। t_dyn ~ R/σ।
Starburst
SFR ∝ Σ_gas²
Kennicutt-Schmidt law। Shock compression। ULIRG luminosity। AGN triggering।
Dark Matter
NFW profile
ρ∝1/r(1+r)²। Halo drag। Core oscillation। DM stripped first।
Final State
Milkomeda
Elliptical remnant। Stars ejected। SMBH binary। ~T+6 Gyr merger।
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