SIMBAD references

We unveil the complex shape of a proto-supercluster at z∼2.45 in the COSMOS field exploiting the synergy of both spectroscopic and photometric redshifts. Thanks to the spectroscopic redshifts of the VIMOS Ultra-Deep Survey (VUDS), complemented by the zCOSMOS-Deep spectroscopic sample and high-quality photometric redshifts, we compute the three-dimensional (3D) overdensity field in a volume of ∼100x100x250 comoving Mpc³ in the central region of the COSMOS field, centred at z∼2.45 along the line of sight. The method relies on a two-dimensional (2D) Voronoi tessellation in overlapping redshift slices that is converted into a 3D density field, where the galaxy distribution in each slice is constructed using a statistical treatment of both spectroscopic and photometric redshifts. In this volume, we identify a proto-supercluster, dubbed "Hyperion" for its immense size and mass, which extends over a volume of ∼60x60x150 comoving Mpc³ and has an estimated total mass of ∼4.8x10¹⁵M_☉. This immensely complex structure contains at least seven density peaks within 2.4≤z≤2.5 connected by filaments that exceed the average density of the volume. We estimate the total mass of the individual peaks, M_tot, based on their inferred average matter density, and find a range of masses from ∼0.1x10¹⁴M_☉ to ∼2.7x10¹⁴M_☉. By using spectroscopic members of each peak, we obtain the velocity dispersion of the galaxies in the peaks, and then their virial mass M_vir (under the strong assumption that they are virialised). The agreement between M_vir and M_tot is surprisingly good, at less than 1-2σ, considering that (almost all) the peaks are probably not yet virialised. According to the spherical collapse model, these peaks have already started or are about to start collapsing, and they are all predicted to be virialised by redshift z∼0.8-1.6. We finally perform a careful comparison with the literature, given that smaller components of this proto-supercluster had previously been identified using either heterogeneous galaxy samples (Lyα emitters, sub-mm starbursting galaxies, CO emitting galaxies) or 3D Lyα forest tomography on a smaller area. With VUDS, we obtain, for the first time across the central ∼1 deg² of the COSMOS field, a panoramic view of this large structure, that encompasses, connects, and considerably expands in a homogeneous way on all previous detections of the various sub-components. The characteristics of this exceptional proto-supercluster, its redshift, its richness over a large volume, the clear detection of its sub-components, together with the extensive multi-wavelength imaging and spectroscopy granted by the COSMOS field, provide us the unique possibility to study a rich supercluster in formation.