The Galactic halo stellar density distribution from photometric survey data: results of a pilot study

¹ Osservatorio Astronomico Di Capodimonte, via Moiariello 16, 80131 Napoli, Italy e-mail: cignoni@df.unipi.it
² Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, Postfach 1312, 85741 Garching, Germany

Received: 19 October 2006
Accepted: 6 November 2006

Abstract

Aims.Our goal is to recover the Galactic halo spatial density by means of field stars. To this aim, we have applied a new technique to the Capodimonte Deep Field (OACDF, Alcalá et al. 2004), as a pilot study in view of the VLT Survey Telescope (VST) stellar projects. Considering this unique chance to collect deep and wide-field photometry with the VST, our method may represent a useful tool towards definitive mapping of the Galactic halo.

Methods.In the framework of synthetic stellar populations, turn-off stars are used to reconstruct the spatial density. The space density is determined by comparing the data with synthetic color-magnitude diagrams (CMDs). The only assumptions involve the IMF, age, and metallicity of the synthetic halo population. Stars are randomly placed in the solid angle. The contributions of the various Monte Carlo distributions (with a step of 4 kpc) along the line of sight are simultaneously varied to reproduce the observed CMD.

Results.Our result for the space density is consistent with a power-law exponent over a range of Galactocentric distances from 8 to 40 kpc.