期刊
ASTROPHYSICAL JOURNAL LETTERS
卷 678, 期 1, 页码 L21-L24出版社
IOP PUBLISHING LTD
DOI: 10.1086/588285
关键词
galaxies : dwarf; galaxies : individual (Tucana); Local Group; stars : horizontal-branch; stars : variables : other
We present a study of the radial distribution of RR Lyrae variables, which present a range of photometric and pulsational properties, in the dwarf spheroidal galaxy Tucana. We find that the fainter RR Lyrae stars, having a shorter period, are more centrally concentrated than the more luminous, longer period RR Lyrae variables. Through comparison with the predictions of theoretical models of stellar evolution and stellar pulsation, we interpret the fainter RR Lyrae stars as a more metal- rich subsample. In addition, we show that they must be older than about 10 Gyr. Therefore, the metallicity gradient must have appeared very early on in the history of this galaxy.
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