MACS J0329-0211 Spectroscopic redshift catalog

The spatial distribution of the red galaxies traces a SE-NW elongated structure, without signs of a velocity gradient. This structure likely originates from the main phase of cluster assembly. The distribution of the blue galaxies is less concentrated, more rounded and shows signs of substructure, all characteristics indicating a recent infall of groups from the field.

We detect two loose clumps of blue galaxies in the south and southwest at a distance about R200 from the cluster center. The strong spatial segregation among galaxy populations is not accompanied by kinematical difference. Thanks to our extensive catalog of spectroscopic redshift, we are able to study galaxy systems that are intervening along the line of sight.

We can identify two foreground galaxy systems (GrG1 at z=0.31 and GrG2 at z=0.38) and one background system (GrG3 at z=0.47). We point out that the second brightest galaxy projected onto the MACS0329 core is in fact the dominant galaxy of the foreground group GrG2. MACS0329, GrG3 and two other systems detected using DESI DR9 photometric redshifts are close to each other, suggesting the presence of a large-scale structure.

MACS0329 is close to a state of dynamical equilibrium, although surrounded by a very rich environment. We emphasize that the use of an extensive redshift survey is essential to avoid misinterpretation of structures projected along the line of sight.