We present new B , V and I-band photometry for a sample of 43 local subdwarfs with HIPPARCOS parallax errors < 13 \% , in the metallicity range -1.0 < [ Fe / H ] < -0.3 , which we use to perform main sequence ( MS ) fitting to the Galactic globular cluster 47 Tuc .
This sample is many times larger than those used in previous MS-fitting studies and also enables us to fit in two colour planes , V / ( B - V ) and V / ( V - I ) .
With this enlarged subdwarf sample we investigate whether the current discrepancy in empirical distance estimates for 47 Tuc , arising from recent MS-fitting and white dwarf fitting results , is due to inaccuracies in the MS-fitting method .
Comparison of published photometries for 47 Tuc has revealed systematic offsets which mean that the ( B - V ) main-line used in previous studies may be too blue by \sim 0.02 mag , which would have the effect of making any derived distance modulus too large by around 0.1 mag .
Preliminary work has also highlighted discrepancies between results obtained in the 2 colour planes , V / ( B - V ) and V / ( V - I ) .
We have derived main-lines in V / ( B - V ) and V / ( V - I ) from the data of Kaluzny et al .
( 1998 ) , which we have recalibrated from the ‘ secondary ’ standards in 47 Tuc of Stetson ( 2000 ) .
Using an assumed cluster reddening of E ( B - V ) = 0.04 , our best-fit apparent distance modulus is ( m - M ) _ { V } = 13.37 ^ { +0.10 } _ { -0.11 } in both colour planes , which implies a cluster age of 11.0 \pm 1.4 Gyr and leads to a dereddened distance modulus of ( m - M ) _ { 0 } = 13.25 ^ { +0.06 } _ { -0.07 } .
Comparison with previous work shows that our apparent distance modulus is \sim 0.2 mag smaller than those derived in previous MS-fitting studies .
The difference is accounted for by our preferred cluster reddening and the recalibration of the cluster photometry , which has made the main-line redder by an average of 0.02 mag in ( B - V ) .
Our derived distance modulus is also now plausibly consistent with the short distance recently derived from white dwarf fitting .
Independent support for our MS-fitting distance comes from consideration of the Red Clump in the cluster , from which we derive a dereddened distance modulus of ( m - M ) _ { 0 } = 13.31 \pm 0.05 , which is in agreement with the MS-fitting result .