Globular Cluster Palomar 5 in SDSS data

Position of various stellar populations in SDSS color-color diagrams can be determined in several ways. For example, Fukugita et al. (1996) calculated colors by convolving stellar spectra with SDSS filters, while Krisciunas, Margon and Szkody (1998) determined colors directly by observing a sample of stars with known types. Another way to determine colors for stellar populations is by utilizing color-magnitude diagrams constructed for globular clusters. Stellar populations can be recognized from the morphology of data distribution in such diagrams, and then studied in color-color diagrams.

The figure below (click here for PostScript version) shows color-magnitude and color-color diagrams for about 2000 stars observed in SDSS commissioning run 756, which are inside a circle with 5 arcmin radius and centered on the position of the core of globular cluster Palomar 5 (the data are not corrected for extinction, estimated to Ar = 0.14 from maps by Schlegel et al., 1998). The upper two panels show g vs. u-g and r vs. g-r color-magnitude diagrams. The middle two panels show g-r vs. u-g and r-i vs. g-r color-magnitude diagrams. These two diagrams also include about 5000 field stars, marked by black dots, which clearly outline the stellar locus. The lower two panels show the zoomed versions of the above two diagrams.

Data are coded according to the position in r vs. g-r color-magnitude diagram displayed in the upper right corner. Most of sources with g-r < 1 probably belong to Palomar 5 and are displayed as blue dots in all 6 diagrams, while stars with g-r > 1, probably field stars, are displayed as red dots. Some stars with g-r < 1 are further coded according to:

Some noteworthy points are: