Galaxy Merge

Simulation

• 'Identikit' software (Barnes & Hibbard 2009) : merge的状态

• 星系的次并合对spin的影响不大，主并合又分两种情况[1]、

fast rotator : 质量较小的merge，气体较多，merge之后可以重新获得气体和恒星，从而获得spin

slow rotator: 质量较大的merge，气体少，并合消耗spin，因而最终是slow rotator

• streams are a strong indication of nearly circular infall of a satellite (with a large angular momentum), whereas the appearance of shells clearly points to (nearly) radial satellite infall. [2]

mini-merge

• 质量比小于1:10
• mini mergers can increase the size of the host disc significantly without changing the global shape of the galaxy, if the impact occurs along the disk plane, providing a possible explanation for extended low-surface brightness disks reported from observations [3]

galaxy pair

• 大星系周围的非常close的satellite计数 [4]

If the satellites eventually infall into the host galaxies, the merger channel will be largely dominated by satellites with a mass ratio down to 1:10,(as these objects have 68 per cent of the total mass in satellites).