GLOBULAR CLUSTER POPULATIONS: FIRST RESULTS FROM S{sup 4}G EARLY-TYPE GALAXIES
- Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
- Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Avenida Ejército 441, Santiago (Chile)
- Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France)
- Astronomy Division, Department of Physics, P.O. Box 3000, FI-90014 University of Oulu (Finland)
- IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States)
- Instituto de Astrofísica de Canarias, Vía Lácteas, E-38205 La Laguna (Spain)
- European Southern Observatory, Casilla 19001, Santiago 19 (Chile)
- MMT Observatory, P.O. Box 210065, Tucson, AZ 85721 (United States)
- Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)
- Leiden Observatory, University of Leiden, Niels Bohrweg 4, NL-2333 Leiden (Netherlands)
- National Radio Astronomy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
Using 3.6 μm images of 97 early-type galaxies, we develop and verify methodology to measure globular cluster populations from the S{sup 4}G survey images. We find that (1) the ratio, T {sub N}, of the number of clusters, N {sub CL}, to parent galaxy stellar mass, M {sub *}, rises weakly with M {sub *} for early-type galaxies with M {sub *} > 10{sup 10} M {sub ☉} when we calculate galaxy masses using a universal stellar initial mass function (IMF) but that the dependence of T {sub N} on M {sub *} is removed entirely once we correct for the recently uncovered systematic variation of IMF with M {sub *}; and (2) for M {sub *} < 10{sup 10} M {sub ☉}, there is no trend between N {sub CL} and M {sub *}, the scatter in T {sub 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 {sub 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 {sub *} > 10{sup 10} M {sub ☉} and can be as large as ∼0.02 for less massive galaxies. These are the first results from the S{sup 4}G sample of galaxies and will be enhanced by the sample of early-type galaxies now being added to S{sup 4}G and complemented by the study of later-type galaxies within S{sup 4}G.
- OSTI ID:
- 22364364
- Journal Information:
- Astrophysical Journal, Vol. 799, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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