Southern Standard Stars for the u'g'r'i'z' System:
An Introduction
The Sloan Digital Sky Survey (SDSS) is a
five-color imaging survey with spectroscopic follow-up of the Northern
Galactic Cap region, approximately one-quarter of the entire sky.
During the first phase of the SDSS (SDSS-1) during the 5 year period
from 2000 to 2005, the SDSS obtained five-color imaging data for
approximately 100 million objects and the positions for each of these
objects. Using the colors and magnitudes the survey selected
approximately 1 million objects for spectroscopic follow-up
observations. These objects were primarily galaxies and quasars and
the spectra enable us to obtain distances to them, thus allowing us to
build a 3-D map of the northern Galactic cap. However, roughly half
of the objects in the imaging survey are stars in our own Galaxy.
Furthermore, the second phase of the SDSS (SDSS-2) has a large stellar
and Galactic Structure component. There are several survey projects
in both SDSS-1 and SDSS-2 designed for looking at the more interesting
of these stars as well as the mundane ones. However, to make sense of
all this, we have to define what we mean when we say a star is a
certain brightness or has a certain color.
We use well-observed, non-varying stars called "standard stars"
to make these definitions. The SDSS uses a group of 158 standard
stars spread around the northern sky that are used as the basis of
the magnitude (or brightness) and color (difference in magnitudes
between two different colored filters) determinations for the survey
objects. This information is then used to select, based on color
and brightness, the spectroscopic candidates for the survey.
All that is well and good but, the northern standard stars are
really only useful in the northern hemisphere. So, we have embarked
on this project to create a set of standard stars in the SDSS
u'g'r'i'z' filter system for the southern hemisphere. This project
will take approximately four years to gather enough observations to
assign magnitudes (brightnesses) to the set of selected stars.
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