Relative distances of Omega Centauri and 47 Tucanae
Abstract
We present precise optical and near-infrared ground-based photometry of two Globular Clusters (GCs): Omega Cen and 47 Tuc. These photometric catalogs are unbiased in the Red Giant Branch (RGB) region close to the tip. We provide new estimates of the RGB tip (TRGB) magnitudes--m_I(TRGB)=9.84+/-0.05, Omega Cen; m_I(TRGB)=9.46+/-0.06, 47 Tuc--and use these to determine the relative distances of the two GCs. We find that distance ratios based on different calibrations of the TRGB, the RR Lyrae stars and kinematic distances agree with each other within one sigma. Absolute TRGB and RR Lyrae distance moduli agree within 0.10--0.15 mag, while absolute kinematic distance moduli are 0.2--0.3 mag smaller. Absolute distances to 47 Tuc based on the Zero-Age-Horizontal-Branch and on the white dwarf fitting agree within 0.1 mag, but they are 0.1--0.3 mag smaller than TRGB and RR Lyrae distances.
Keywords
Cite
@article{arxiv.0809.0863,
title = {Relative distances of Omega Centauri and 47 Tucanae},
author = {G. Bono and P. B. Stetson and N. Sanna and A. Piersimoni and L. M. Freyhammer and Y. Bouzid and R. Buonanno and A. Calamida and F. Caputo and C. E. Corsi and A. Di Cecco and M. Dall'Ora and I. Ferraro and G. Iannicola and M. Monelli and M. Nonino and L. Pulone and C. Sterken and J. Storm and T. Tuvikene and A. R. Walker},
journal= {arXiv preprint arXiv:0809.0863},
year = {2009}
}
Comments
5 pages, 4 figures, accepted for publication by ApJL