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A new method to estimate the ages of globular clusters: the case of NGC 3201

Published online by Cambridge University Press:  01 October 2008

A. Calamida ,
G. Bono ,
P. B. Stetson ,
M. Dall'Ora ,
M. Monelli ,
C. E. Corsi ,
P. G. Prada Moroni ,
S. Degl'Innocenti ,
A. Dotter  and
C. Brasseur
...Show all authors
A. Calamida
Affiliation:
ESO, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München, Germany email: acalamid@eso.org
G. Bono
Affiliation:
Universita' di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00040, Monte Porzio Catone, Italy
P. B. Stetson
Affiliation:
DAO, HIA-NRC, 5071 W. Saanich Road, Victoria, BC V9E 2E7, Canada
M. Dall'Ora
Affiliation:
INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
M. Monelli
Affiliation:
IAC - Instituto de Astrofisica de Canarias, Calle Via Lactea, E38200 La Laguna, Tenerife, Spain
C. E. Corsi
Affiliation:
INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00040, Monte Porzio Catone, Italy
P. G. Prada Moroni
Affiliation:
INAF-Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 40131 Trieste, Italy
S. Degl'Innocenti
Affiliation:
INAF-Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 40131 Trieste, Italy
A. Dotter
Affiliation:
UVIC, Victoria, BC V8W 3P6, Canada
C. Brasseur
Affiliation:
UVIC, Victoria, BC V8W 3P6, Canada
P. Amico
Affiliation:
ESO, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München, Germany email: acalamid@eso.org
E. Marchetti
Affiliation:
ESO, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München, Germany email: acalamid@eso.org
R. Buonanno
Affiliation:
Universita' di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy
A. Di Cecco
Affiliation:
Universita' di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy
S. D'Odorico
Affiliation:
ESO, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München, Germany email: acalamid@eso.org
I. Ferraro
Affiliation:
INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00040, Monte Porzio Catone, Italy
G. Iannicola
Affiliation:
INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00040, Monte Porzio Catone, Italy
M. Nonino
Affiliation:
INAF-Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 40131 Trieste, Italy
M. Romaniello
Affiliation:
ESO, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München, Germany email: acalamid@eso.org
N. Sanna
Affiliation:
Universita' di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy
D. A. Vandenberg
Affiliation:
UVIC, Victoria, BC V8W 3P6, Canada
M. Zoccali
Affiliation:
Universidad de Concepcion, Departamento de Fisica, Casilla 106-C, Concepcion, Chile
A. Walker
Affiliation:
Cerro Totolo Inter-American Observatory, Chile
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Abstract

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We devised a new method to estimate globular cluster absolute ages by adopting the knee of the bending of the lower main-sequence (MS) in the Near-Infrared (NIR) J, J - Ks color-magnitude diagram. The color difference between this feature and the Turn-Off point is strongly correlated to the cluster age. This method is marginally affected by distance and reddening uncertainties, and by the possible occurrence of differential reddening. Furthermore, the knee location does not depend on the cluster age and it is a robust theoretical prediction. We adopted accurate J, Ks-band photometry collected with both MAD/VLT and SOFI/NTT for the Galactic globular cluster NGC 3201 to identify the location of the knee at J~19.90 ±0.03 and J-Ks ~0.76±0.02 mag. The comparison with different sets of cluster isochrones, transformed adopting different Color–Temperature–Relations (CTRs), shows that the models are slightly redder than the observations for J > 19 mag. This difference could be due to the presence of a calibration drift or to a problem of the CTRs in this magnitude range.

Keywords

globular clusters: generalglobular clusters: individual (NGC 3201)
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Symposium S258: The Ages of Stars , October 2008 , pp. 189 - 196
Copyright
Copyright © International Astronomical Union 2009

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