CfCP SDSS Science Center Projects
With our SDSS colleagues, we are measuring the clustering of
galaxies in the SDSS redshift survey. Preliminary results based
on a sample of 30,000 galaxies were published in 2001. In 2002,
we are analyzing a much larger sample of 170,000 galaxies,
which enables us to measure how galaxy clustering varies with
properties such as luminosity, color, and spectral type.
These variations probe the nature of bias, the relation
between galaxy and mass clustering.
The redshift distortions of the clustering will enable us to
measure the cosmic density parameter. In addition, a much
larger sample of ~10 million galaxies with photometric redshift
estimates is being analyzed, yielding results consistent
with those from the redshift survey.
We are also working
on interpreting these clustering results using the halo
occupation model of galaxy formation.
A catalog of galaxy groups and clusters in the SDSS redshift
survey is being constructed, using a friends-of-friends
algorithm, which will provide an independent probe of the
halo model and cosmological parameters.
We are analyzing galaxy-galaxy lensing in the SDSS imaging
data and using it to probe the nature of galaxy dark halos and the
correlation of halo properties with the luminous components
(morphology, luminosity, etc)
of galaxies. Galaxy-galaxy lensing offers a sensitive
probe of the cosmic density parameter and a constraint on
the bias between mass and light. Preliminary results from
SDSS commissioning data were published in 1999; a sample
ten times larger is now being analyzed. More information
Statistical weak lensing of clusters detected in the
SDSS imaging survey is being used to probe
the relation between
cluster mass and other observables such as
X-ray temperature and the number of cluster
We are carrying out a systematic search for lensed
quasars in SDSS data, using the ARC 3.5m telescope,
Magellan, Keck, and the MMT for follow-up
spectroscopy and imaging,
with the aim of constructing
a homogeneous sample for studies of cosmology and
(lens) galaxy properties. So far, several SDSS
lenses have been discovered.
We have constructed a spectral classification system
for SDSS quasars based on Principal Component Analysis.
We have developed the
SDSS spectra, classifies objects, calculates their redshifts,
and measures a variety of properties (line equivalent widths,
velocity dispersions, spectral classes, etc). We are
currently developing techniques to decompose spectra into
their components when the light from two objects is found in
a single spectroscopic fiber.
We have developed an advanced 3-d visualization tool for
viewing the SDSS redshift data (and other multi-dimensional datasets).
This system, developed for both scientific and
educational outreach purposes,
is particularly useful for viewing the large-scale
clustering of galaxies and quasars.
This system has been
on temporary display at the Adler Planetarium and has been
featured in Discover magazine, National Geographic,
WTTW Channel 11, and WBBM-TV in Chicago.