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1999AJ....118.2229M - Astron. J., 118, 2229-2244 (1999/November-0)
The star formation history of the local group dwarf elliptical galaxy NGC 185. II. Gradients in the stellar population.
MARTINEZ-DELGADO D., APARICIO A. and GALLART C.
Abstract (from CDS):
The luminous ``blue stars'' discovered by W. Baade in 1951 in the center of NGC 185 are discussed using new CCD images in B and Baade's original photographic plates. Considering their fuzzy, unresolved appearance and that a conspicuous main sequence is lacking in the CMD at our limiting magnitude, we reach the conclusion that most of Baade's blue objects are in fact star clusters. These clusters, as well as the other stellar populations, are young (a few times 100 Myr) but not as young as they would be if they were individual stars (a few times 10 Myr). A supernova remnant (SNR) close to the center of NGC 185 has been analyzed from Hα images. The fact that a conspicuous main sequence is lacking in our CMD implies that the supernova (SN) had originated from a white dwarf progenitor. A consistent picture arises in which the gas observed in the central region of NGC 185 would have an internal origin. The rate at which evolved stars return gas to the interstellar medium is enough to seed the recent star formation observed in the center of the galaxy, and the SN rate is probably low enough to allow the galaxy to retain the gas not used in the new stellar generations. Further support is found in the similar kinematic properties of gas and stars.
Abstract Copyright: ∼
Journal keyword(s): Galaxies: Dwarf - Galaxies: Evolution - Galaxies: Individual: NGC Number: NGC 185 - Galaxies: Photometry - Galaxies: Local Group
Nomenclature: Table 2: [MAG99] NN (Nos 1-19).
Simbad objects: 25
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