EDP Sciences
Free access
Issue
A&A
Volume 424, Number 1, September II 2004
Page(s) 199 - 211
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20035910


A&A 424, 199-211 (2004)
DOI: 10.1051/0004-6361:20035910

The calibration of the RGB Tip as a Standard Candle

Extension to Near Infrared colors and higher metallicity
M. Bellazzini1, F. R. Ferraro2, A. Sollima1, 2, E. Pancino1 and L. Origlia1

1  INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
    e-mail: michele.bellazzini@bo.astro.it
2  Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
    e-mail: francesco.ferraro3@unibo.it

(Received 19 December 2003 / Accepted 28 April 2004 )

Abstract
New empirical calibrations of the Red Giant Branch Tip in the  I, J, H and  K bands based on two fundamental pillars, namely $\omega$ Centauri and 47 Tucanae, have been obtained by using a large optical and near infrared photometric database.

Our best estimates give $M_I^{\rm TRGB}= -4.05 \pm 0.12$, $M_J^{\rm TRGB}= -5.20 \pm 0.16$, $M_H^{\rm TRGB}= -5.94 \pm 0.18$ and $M_K^{\rm TRGB}= -6.04 \pm 0.16$ at $[M/H]\simeq-1.5$ ( $\omega$ Cen) and $M_I^{\rm TRGB}= -3.91 \pm 0.13$, $M_J^{\rm TRGB}= -5.47 \pm 0.25$, $M_H^{\rm TRGB}= -6.35 \pm 0.30$ and $M_K^{\rm TRGB}= -6.56 \pm 0.20$ at $[M/H]\simeq-0.6$ (47 Tuc).

With these new empirical calibrations we also provide robust relations of the TRGB magnitude in the  I, J, H, and K bands as a function of the global metallicity. It has also been shown that our calibrations self-consistently provide a distance modulus of the Large Magellanic Cloud in good agreement with the standard value ( $(m-M)_0\simeq 18.50$)).


Key words: distance scale -- globular clusters: individual: NGC 5139; NGC 104 -- stars: Population II -- Magellanic Clouds

SIMBAD Objects



© ESO 2004