400d is an X-ray survey for galaxy clusters using
observations. It is sensitive to "typical",
M ~ 3e14 h−1 Msun, clusters out to
z ~ 1 and covers 400 square degrees
— essentially all suitable ROSAT pointed
data. Our sensitive detection
algorithm has produced a statistically complete and
uncontaminated cluster sample.
Our catalog contains 242 clusters,
all with spectroscopic redshfits. The survey area and volume
are carefully calibrated.
A complete subsample of 41 clusters at
0.35 < z < 0.9 was observed
with Chandra. These
clusters are the basis of our cosmological
work. They are also used in several accompanying projects.