Modeling Merger-Induced Starbursts

Question: If we use

generic galaxy models
plausible interaction parameters
simple star formation models

can we reproduce the properties of the ultraluminous IRAS galaxies through mergers?

Galaxy models:

exponential disk of gas and stars
M_gas = 10% M_disk
optional central bulge (M_bulge = 1/3 M_disk)
spherical dark matter halo (M_halo ~ 5 M_disk out to ~ 50 kpc)

Star formation prescription:

like a Schmidt law of index n~1.5
simple density dependence

Model 1: Disk/Halo galaxies

Evolution of Stars

Evolution of Gas

Star Formation rate

Model 2: Disk/Bulge/Halo Galaxies

Evolution of Stars

Evolution of Gas

Evolution of Star Formation Rate

What's going on?

Gaseous inflow and central activity are driven by gravitational torques from the host disk:
(Noguchi 1987; Barnes & Hernquist 1991; Mihos & Hernquist 1996)

Gas Angular Momentum	Physical Torques	Gravitational Torques

	(from Mihos & Hernquist 1996)

Inflow can be suppressed if global instabilities are suppressed:

Including a central bulge (Mihos & Hernquist 1994, 1996)

Reducing the disk surface density (eg, LSBs; Mihos, McGaugh, & de Blok 1997; Mihos 1999)

Suppressing orbital resonances (Barnes & Hernquist 1996)

but other influences (gas fraction, environment, etc) must surely also play a role...

Response is closely coupled to the dynamical and structural properties of the colliding galaxies. This has important ramifications for:

the nature of QSO/ULIRG host galaxies
the differences between interactions at low and high redshift