Toomre sequence

The Toomre Sequence is a series of galaxies introduced by Alar Toomre in 1977 that exemplifies how the appearance of interacting and merging spiral galaxies changes as the merging process progresses, increasingly resembling elliptical galaxies . At the beginning, the original galaxies are still clearly separated, while at the end there is only a single galaxy body.

Toomre Sequence galaxies

Progressing from early to later stages of the amalgamation, the members of the Toomre sequence are:

• NGC 4038 / NGC 4039
• NGC 4676
• NGC 7592
• NGC 7764A
• NGC 6621 / NGC 6622
• NGC 3509
• NGC 520
• NGC 2623
• NGC 3256
• NGC 3921
• NGC 7252

literature

• Toomre, A., Mergers and some consequences , in The Evolution of Galaxies and Stellar Populations , eds. BM Tinsley and RB Larson, (New Haven: Yale University Press), p. 401 (1977),