Color--Magnitude Diagrams and Luminosity Functions down to the Hydrogen Burning Limit. III. A Preliminary HST Study of NGC6791

King, I. R.; Bedin, L. R.; Piotto, G.; Cassisi, S.; Anderson, J.; .

Color--Magnitude Diagrams and Luminosity Functions down to the Hydrogen Burning Limit. III. A Preliminary HST Study of NGC6791

Authors

Description

Using HST ACS/WFC images, we derive the color--magnitude diagram of the old, metal-rich open cluster NGC 6791 to nearly 29th magnitude in V, which is the neighborhood of the hydrogen-burning limit.Comparison with isochrones leads to a discussion of the distance modulus, the reddening, and the age of the cluster. By making a statistical correction for field stars we derive a preliminary luminosity function, and a very tentative mass function. The white dwarf sequence is clearly shown, and has been discussed in a separate paper.
21 pages, 8 figures. Accepted (25 April 2005) on AJ, in press for the August issue