Publication Date:
2014-04-02
Description:
The relation between the stellar mass and size of a galaxy's structural subcomponents, such as discs and spheroids, is a powerful way to understand the processes involved in their formation. Using very large catalogues of photometric bulge+disc structural decompositions and stellar masses from the Sloan Digital Sky Survey Data Release Seven, we carefully define two large subsamples of spheroids in a quantitative manner such that both samples share similar characteristics with one important exception: the ‘bulges’ are embedded in a disc and the ‘pure spheroids’ are galaxies with a single structural component. Our bulge and pure spheroid subsample sizes are 76 012 and 171 243, respectively. Above a stellar mass of ~10 10 M , the mass–size relations of both subsamples are parallel to one another and are close to lines of constant surface mass density. However, the relations are offset by a factor of 1.4, which may be explained by the dominance of dissipation in their formation processes. Whereas the size–mass relation of bulges in discs is consistent with gas-rich mergers, pure spheroids appear to have been formed via a combination of ‘dry’ and ‘wet’ mergers.
Print ISSN:
1745-3925
Electronic ISSN:
1745-3933
Topics:
Physics
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