Young rich clusters have very important
cosmological implications since they are supposed to originate from the
rare initial density fluctuations of high amplitude.
In this general context, we have initiated a high
resolution multi-wavelength campaign (IR, radio, optical, X-ray)
in order to study in detail the properties of
distant bright X-ray clusters newly discovered
in the ROSAT All-Sky-Survey (RASS), especially in order to better understand
their dynamical state (Pierre et al. 1994a). We have selected a set
of 
clusters, having X-ray luminosities greater than
and thus expected to be massive. This implies a high density
for the intra-cluster gas and most likely, a deep gravitational potential. The
objects are located in the southern hemisphere between
within an area covering some 1700 square degrees. The redshifts cover
the range z = 0.15-0.31, which is ideal for mapping the whole cluster
extent within reasonable exposure times. It will also be possible to tackle
question related to cluster evolution by comparison with lower redshift
observations.
The cluster of galaxies A1300 is one of the priority target of the programme and we present here the first results of the detailed optical follow-up concerning this object.
A1300 is described as a richness class 1
object by Abell et al. (1989) and had not drawn specific
attention from the community so far. It was observed for the
first time in X-ray during the RASS and notified as such during a subsequent identification campaign at
the ESO 3.6 m Telescope (Pierre et al. 1994b).
These optical observations have shown that the cluster
is quite rich, very extended, has a redshift of
and suggested a high velocity
dispersion.
The RASS X-ray image is clearly extended, approximately in the SN
direction (Pierre et al. 1994b). Preliminary analysis
of a subsequent deep PSPC ROSAT pointing shows a
distinct clump at the northern end, some 3' from the cluster center,
corresponding to a conspicuous enhancement of the galaxy density. The
X-ray luminosity appeared to be high, 
in the ROSAT band, and hard.
All of this indicate that A1300 is quite
an interesting object - probably exceptional -,
one of the few 
clusters having a
high X-ray luminosity.
Throughout the paper we assume a Hubble
constant of 50 km/s/Mpc and 
.
 field center | Time (min) | |
| Photometry | ||
| R images | cD | 15, 10 |
| B images | cD |  |
| Spectroscopy | ||
| 1st mask | cD | 45, 40 |
| 2nd mask | cD | 75, 50 |
| 3rd mask | 3' north of the cD | 60, 75 |
|
