1. Dynamics at high redshifts:

2. the case of a cluster at z=1.47
Sandro Bardelli - INAF Osservatorio Astronomico di Bologna
Christian Marinoni - LAM Marseille
Angela Iovino - INAF Osservatorio Astronomico di Brera
M.Scodeggio, O.Cucciati, O.Ilbert, M.Bolzonella, E.Zucca, C. Adami,
A. Zanichelli, L. Guzzo, L.Tresse, G.Zamorani, S.Arnouts, A.Cappi,
L.Pozzetti, D.Bottini, B.Garilli, V.LeBrun, O.LeFevre, D.Maccagni, J.P.Picat, R.Scaramella, G.Vettolani, M.Arnaboldi, S.Charlot, P.Ciliegi, T.Contini, S.Foucaud, P.Franzetti, I.Gavignaud, H.J.McCracken, B.Marano, A.Mazure, B.Meneux, R.Merighi, S.Paltani, R.Pello`, A.Pollo, M.Radovich, M.Bondi, A.Bongiorno, G.Busarello, S.Temporin, D.Vergani,
L.Gregorini, F.Lamareille, G.Mathez, Y.Mellier, P.Merluzzi,V.Ripepi, D.Rizzo

3. Figure 1 Fi

4. z=1.5
Figure 2
z=1.4
The cluster at
z=1.47
Figure 3

5. Figure 4
Spectroscopic
redshift histogram
in the cluster
region

6. The deep F02 field of the VIMOS VLT Deep Survey (VVDS, PI Le Fevre)
gives a unique possibility to study in depth (up to z~1.5) the large scale
structure of the Universe (Figure1). This survey collected redshifts of
galaxies to IAB<24 in an area of 0.4 x 0.4 deg2 .
Moreover deep photometry is available in the UBVRIJK bands.
Using the Voronoi Delaunay technique (Marinoni et al. 2002) on the
spectroscopic sample, we detected a significant system of galaxies
at z=1.47 (Figure 2). All spectra present features that assure good redshift
determination (Figure 3). This structure has been detected because of the
presence of 9 galaxies in a 7x7 arcmin region (corresponding
to 3.5x3.5 Mpc).
If we consider a wider region of 13x13 arcmin (6.5x6.5 Mpc),
the number of concordant redshifts increases: in Figure 4 we show the
redshifts histogram with the solid line representing the smoothed total
redshifts distribution of the VVDS.
No X ray emission has been found in a
unfavourable XMM archive observation.

7. Figure 5
The UBVRIJK coverage of the F02 field permits to compute high quality
photometric redshifts. In this figure (left) we performed an adaptive kernel
filtering of the whole F02 area, by selecting objects with photometric
redshift in the range [ ]. Black points corresponds to galaxies with
spectroscopic redshifts in the range [ ], while red points
correspond to a subclump of 5 very red galaxies. The structure has a
dimension of about 8x6 Mpc.

8. Figure 6
Figure 7

9. Figure 6

10. Figure 7

11. This structure lack of a definite color - magnitude relation.
In Figure 6 we show the (I - J) - I color magnitude plot of galaxies
in the cluster area. Triangles are galaxies with photometric redshift
within the range [ ], blue triangles are the red galaxies shown in
Figure 5. Note that at z=1.47, M* of elliptical galaxies has a magnitude of
IAB=25, while extreme blue galaxies have IAB=24.3 (Zucca et al, 2006) .
The red band represents the expected position of the color - magnitude
relation for red galaxies.
In Figure 7 we show the color - color relation of the galaxies in the
cluster region. Symbols are the same as in Figure 6, while the red lines
correspond to the expected colors of a z=1.47 elliptical.

12. DISCUSSION: Cluster or Forming structure?
This structure appears as an overdensity both in the
photometric and spectroscopic redshifts and is formed
by three subclumps and resemble the much more
massive cluster complexes in the Shapley Concentration
(Bardelli et al. 1998).
The velocity dispersion of the central clump is
775 + / km/s (based on 9 galaxies within a region
of 7’x8’) and is one of the most distant cluster known
(with those found by Mullis et al and Stanford
et al both at z=1.4).
This structure does not present evident color - magnitude
relation, but this is not surprising because it was found
as a purely optical detection (see Donahue et al. 2002)

15. The VVDS CONE

16. 3000 Mpc

17. VVDS 0226-04 “cone” 6217 galaxies with secure redshifts, IAB24
Coverage on 30x30 arcmin² so far
Current volume sampled: 3x106 Mpc3
=1/16th of final goal
3000 Mpc