**AAS 200th meeting, Albuquerque, NM, June 2002**

*Session 77. Large Scale Structure with the SDSS*

Special Session Oral, Thursday, June 6, 2002, 10:00-11:30am, Ballroom A
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## [77.06] SDSS Cluster Abundance and Cosmological Implications

*J. Annis, M. Makler, S. Kent, S. Dodelson, J. Frieman (Fermilab), E. Sheldon, T. McKay (Michigan), N. Bahcall (Princeton), SDSS Collaboration*

The SDSS is a very good cluster finding machine. The precise
5 color photometry allows photometric redshift techniques
that revolutionize methods of finding clusters in the
optical: projection on scales greater than delta-z = 0.05 is
no longer a problem. A corollary is that cluster finders
become both powerful group finders and powerful redshift
estimators. The statistics of the SDSS allows several
scaling relations to be constructed: N_{gals}, Lambda,
\sigma_{vel}, and weak lensing shear may be measured and
related. In particular, we find that the cluster galaxy
number function may be constructed from 0.05 \leq z \leq
0.5. By using SDSS calibrated halo occupational number
distribution theories, the number functions may be
predicted. The implied mass functions agree well with the
measured SDSS velocity dispersion function, but do not
suffer from the cosmic variance problems of all z < 0.1
measures.The number functions are quite sensitive to the
mass power spectrum. In particular, the
\sigma_{8}/\Omega_{m} degeneracy is broken, and constraints
on \sigma_{8}, the normalization of the power spectrum, may
be placed. The other relevent cosmological parameters that
affect the mass power spectrum are the dark matter mass
density, the power spectrum index, and the neutrino mass
density.

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Bulletin of the American Astronomical Society, **34**

© 2002. The American Astronomical Soceity.