Galaxy Collisions
Curtis Struck
Dept of Physics and Astronomy, Iowa State University, Ames, IA 50010 USA
E-mail: curt@iastate.edu
Table 1: Classification Variables
Timescale |
Y (young) ² 108 yr. |
I (intermediate) 108-108 |
O (old) > 109 yr. |
Hubble Type for each galaxy (Disk component, gas fraction) |
E elliptical, spheroidal |
D significant disk |
G gas disk, or irregular |
Companion Mass, Perturbation Amplitude |
Small < 10% denote by subscript |
Intermediate Å 10-50% lower case |
Large > 50% upper case |
Spin-Orbit Coupling (for each galaxy) |
+ prograde |
0 orthogonal |
- retrograde |
Table 2: General Types of Induced Star Formation
|
Type |
Description |
Activity Timescale |
Relative Intensity |
Example |
|
Central Starbursts |
Nuclear, Nuclear Rings, or Bars |
Short to Intermediate |
Moderate |
M82 |
|
Waves in Disks |
Rings, Spirals or more complicated forms |
Short to Intermediate |
Weak - Moderate |
M51, Cartwheel |
|
Extended Tidal Features |
Tails, Bridges, etc. |
Short to Intermediate |
Weak |
Arp 295 |
|
Mergers |
Strong Central SF (plus any of the above) |
Intermediate to Long |
Weak to Strong |
Arp 220 |
Table 3: Merger Rate Exponent Determinations
|
Source |
Exponent m |
Mean Survey Redshift |
|
Zepf & Koo 1989 |
4.0 ± 2.5 |
0.25 |
|
Burkey et al. 1994 |
2.5 ± 0.5 |
0.4 |
|
Calberg, Pritchet, & Infante 1994 |
3.4 ± 1.0 |
0.4 |
|
Woods, Fahlman, & Richer 1995 |
Å 0 |
³ 0.4 |
|
Yee & Ellingson 1995 |
4.0 ± 1.5 |
0.38 |
|
Lavery et al. 1996 |
Å 4.5 |
Å 1.0 |
|
Neuschaefer et al. 1997 HST Medium Deep Survey |
1.2 ± 0.4 |
1-2 |
|
Patton et al. 1997 |
2.8 ± 0.9 |
0.33 |