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Near-infrared photometry of globular clusters towards the Galactic bulge : observations and photometric metallicity indicators

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Near-infrared photometry of globular clusters towards the Galactic bulge : observations and photometric metallicity indicators

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Título Near-infrared photometry of globular clusters towards the Galactic bulge : observations and photometric metallicity indicators
Autor Cohen, Roger
Moni Bidin, Christian
Mauro, Francesco
Bonatto, Charles Jose
Geisler, Doug
Abstract We present wide-field JHKS photometry of 16 Galactic globular clusters located towards the Galactic bulge, calibrated on the Two Micron All-Sky Survey photometric system. Differential reddening corrections and statistical field star decontamination are employed for all of these clusters before fitting fiducial sequences to the cluster red giant branches (RGBs). Observed values and uncertainties are reported for several photometric features, including the magnitude of the RGB bump, tip, the horizontal branch (HB) and the slope of the upper RGB. The latest spectroscopically determined chemical abundances are used to build distance- and reddening-independent relations between observed photometric features and cluster metallicity, optimizing the sample size and metallicity baseline of these relations by supplementing our sample with results from the literature.We find that the magnitude difference between the HB and the RGB bump can be used to predict metallicities, in terms of both iron abundance [Fe/H] and global metallicity [M/H], with a precision of better than 0.1 dex in all three near-IR bandpasses for relatively metal-rich ([M/H] −1) clusters. Meanwhile, both the slope of the upper RGB and the magnitude difference between the RGB tip and bump are useful metallicity indicators over the entire sampled metallicity range (−2 [M/H] 0) with a precision of 0.2 dex or better, despite model predictions that the RGB slope may become unreliable at high (near-solar) metallicities. Our results agree with previous calibrations in light of the relevant uncertainties, and we discuss implications for clusters with controversial metallicities as well as directions for further investigation.
Contido em Monthly notices of the Royal Astronomical Society. Oxford. Vol. 464, no. 2 (Jan. 2017), p. 1874-1902
Assunto Aglomerados globulares
Bojos de galaxias
Fotometria astronômica
Metalicidade
[en] General – infrared
[en] Globular clusters
[en] Stars
Origem Estrangeiro
Tipo Artigo de periódico
URI http://hdl.handle.net/10183/165000
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