Globular Cluster Populations: First Results from S4G Early-type Galaxies

Zaritsky, D.; Aravena, Manuel; Athanassoula, E.; Bosma, Albert; Comerón, Sébastien; Elmegreen, Bruce G.; Erroz-Ferrer, S.; Gadotti, Dimitri A.; Hinz, Joannah L.; Ho, Luis C.; Holwerda, Benne; Knapen, J. H.; Laine, Jarkko; Laurikainen, Eija; Muñoz-Mateos, Juan Carlos; Salo, Heikki; Sheth, Kartik
Referencia bibliográfica

The Astrophysical Journal, Volume 799, Issue 2, article id. 159, 19 pp. (2015).

Fecha de publicación:
2
2015
Número de autores
17
Número de autores del IAC
2
Número de citas
11
Número de citas referidas
11
Descripción
Using 3.6 μm images of 97 early-type galaxies, we develop and verify methodology to measure globular cluster populations from the S4G survey images. We find that (1) the ratio, T N, of the number of clusters, N CL, to parent galaxy stellar mass, M *, rises weakly with M * for early-type galaxies with M * > 1010 M ☉ when we calculate galaxy masses using a universal stellar initial mass function (IMF) but that the dependence of T N on M * is removed entirely once we correct for the recently uncovered systematic variation of IMF with M *; and (2) for M * < 1010 M ☉, there is no trend between N CL and M *, the scatter in T N is significantly larger (approaching two orders of magnitude), and there is evidence to support a previous, independent suggestion of two families of galaxies. The behavior of N CL in the lower-mass systems is more difficult to measure because these systems are inherently cluster-poor, but our results may add to previous evidence that large variations in cluster formation and destruction efficiencies are to be found among low-mass galaxies. The average fraction of stellar mass in clusters is ~0.0014 for M * > 1010 M ☉ and can be as large as ~0.02 for less massive galaxies. These are the first results from the S4G sample of galaxies and will be enhanced by the sample of early-type galaxies now being added to S4G and complemented by the study of later-type galaxies within S4G.
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