Red giant branch stars as probes of stellar populations

Free access article

Issue		A&A Volume 442, Number 1, October IV 2005


Page(s)		195 - 200
Section		Galactic structure, stellar clusters and populations
DOI		http://dx.doi.org/10.1051/0004-6361:20053093

A&A 442, 195-200 (2005)
DOI: 10.1051/0004-6361:20053093

II. Properties of the newly discovered globular cluster GLIMPSE-C01

V. D. Ivanov¹, R. Kurtev² and J. Borissova¹

¹ European Southern Observatory, Ave. Alonso de Cordova 3107, Casilla 19, Santiago 19001, Chile
e-mail: [vivanov;jborisso]@eso.org
² Departamento de Física y Meteorología, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 644, Playa Ancha, Casilla 53, Valparaíso, Chile
e-mail: rkurtev@uv.cl

(Received 19 March 2005 / Accepted 26 May 2005)

Abstract
Deep near infrared photometry of the newly discovered Galactic globular Cluster GLIMPSE-C01 is reported. We derived for the first time the metal abundance of this object from the slope of the RGB: ${\rm [Fe/H]}=-1.61\pm0.14$ in the scale of Zinn (as implemented in Harris 1996), ${\rm [Fe/H]}=-1.44\pm0.12$ in the scale of Caretta & Gratton (1997), and ${\rm [Fe/H]}=-1.12\pm0.12$ in the scale of Ferraro et al. (1999). The tip and the clump of the red giant branch were used to confirm the estimates of Kobulnicky et al. (2005), placing the cluster at $D\sim3.7\pm0.8$ kpc, behind $A_{\rm V}\sim15$ mag of visual extinction. The best fit to the radial surface brightness profile with a single-mass King's model yielded a core radius $r_{\rm c}=0.78$ arcmin, tidal radius $r_{\rm t}=27$ arcmin and central concentration c=1.54.

Finally, we estimate the number of the "missing" globulars in the central region of the Milky Way. Based on the spatial distribution of the known clusters, and assuming radial symmetry around the Galactic center, we conclude that the Milky Way contains at least $10\pm3$ undiscovered objects. The distribution of known clusters in the bulge seem to resemble the orientation of the Milky Way bar.

Key words: Galaxy: globular clusters: general -- Galaxy: abundances -- stars: distances -- Galaxy: bulge -- Galaxy: fundamental parameters

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