Breaks and truncations: a unified picture for spiral galaxies

Martín-Navarro, I.; Trujillo, I.; Bakos, J.; Knapen, J. H.
Bibliographical reference

Memorie della Societa Astronomica Italiana Supplement, v.25, p.25 (2013)

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2013
Number of authors
4
IAC number of authors
4
Citations
0
Refereed citations
0
Description
Departures from a simple exponential decay (usually called breaks or truncations) in the surface brightness distribution of galaxy disks are found in the vast majority of spirals. Understanding the origin of these breaks and how they evolve with time are key to address the mechanisms of galaxy growth. However, the community has encountered a significant discrepancy among the results obtained when the galaxies are observed face-on versus those cases where the projection is edge-on. In fact, truncations in edge-on disks are found at much larger radial distances than the breaks observed in face-on projections. In order to solve this puzzle, we have explored a large collection of edge-on late-type spiral galaxies using the SDSS and the S4G (Spitzer) surveys. We observe that breaks and truncations are not the same phenomena: we find both features coexisting in our spiral galaxies. We propose a unified picture where breaks are likely caused by a threshold in the star formation activity whereas truncations are associated to a drop in the distribution of stars caused by the maximum angular momentum of the disk. Our scheme is capable of unifying all the previous observations into a simple picture.