Red giant branch stars as probes of stellar populations. I. 2MASS calibration and application to 2MASS GC01

Free access article

Issue		A&A Volume 390, Number 3, August II 2002


Page(s)		937 - 943
Section		Stellar clusters and associations
DOI		http://dx.doi.org/10.1051/0004-6361:20020748

A&A 390, 937-943 (2002)
DOI: 10.1051/0004-6361:20020748

Red giant branch stars as probes of stellar populations. I. 2MASS calibration and application to 2MASS GC01

V. D. Ivanov¹ and J. Borissova²

¹ European Southern Observatory, Ave. Alonso de Cordova 3107, Casilla 19, Santiago 19001, Chile
² Institute of Astronomy, Bulgarian Academy of Sciences, and Isaac Newton Institute of Chile, Bulgarian Branch, 72 Tsarigradsko Chaussèe, 1784 Sofia, Bulgaria
e-mail: jura@haemimont.bg

(Received 16 January 2002 / Accepted 24 April 2002 )

Abstract
The near-infrared behavior of the red giant branch (RGB hereafter) as a function of abundance is examined with an unprecedented large sample of 27 Galactic globular clusters with Two Micron All Sky Survey photometry. We propose a new simplified analysis, involving the zero point of the RGB slope fit, and derive calibrations for the RGB slope, zero point, and tip. The weak metallicity sensitivity of the zero point leads to a "fan"-like diagram to obtain the abundance distributions in resolved stellar systems, and reddening estimates. Finally, we apply the new calibrations to the recently discovered Galactic globular cluster 2MASS GC01, to derive [Fe/H] $_{\rm H96}=-1.19\pm0.38$ mag. The uncertainty is dominated by the severe foreground contamination. We estimate an extinction of $A_V=21.07\pm2.20$ mag toward the cluster.

Key words: Galaxy: globular clusters: general -- Galaxy: abundances -- galaxies: abundances -- galaxies: distances and redshifts -- stars: distances -- stars: abundances

Offprint request: V. D. Ivanov, vivanov@eso.org

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