Astronomy & Astrophysics manuscript no. output c ESO 2020 April 16, 2020 A redshift database towards the Shapley Supercluster region ⋆ Hernán Quintana 1 , Dominique Proust 2 , Rolando Dünner 1 , Eleazar R. Carrasco 3 , and Andreas Reisenegger 1 1 Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile. Mail: hquin- tana@astro.puc.cl 2 GEPI, Observatoire de Paris, F92195 Meudon Principal CEDEX, France. 3 Gemini Observatory, NSF’s National Optical-Infrared Astronomy Research Laboratory, Casilla 603, La Serena 1700000, Chile. Received February 14, 2020; accepted April 2, 2020. ABSTRACT We present a database and catalogue of radial velocities of galaxies towards the region of the Shapley Supercluster (SSC) based on 18,129 measured velocities for 10,702 galaxies in the approximately 300 square degree area between 12h43m00s < R.A. < 14h17m00s and −23 ◦ 30 ′ 00 ′′ > Dec > −38 ◦ 30 ′ 00 ′′ . The database contains velocity measurements that have been reported in the literature up until 2015. It also includes 5,084 velocities, corresponding to 4,617 galaxies, observed by us at Las Campanas Observatory and Cerro Tololo Inter-American Observatory, which had not been reported individually until now. Of the latter, 2,585 correspond to galaxies with no other previously published velocity measurement before 2015. Every galaxy in the velocity database has been identified with a galaxy extracted from the SuperCOSMOS photometric catalogues. We also provide a combined average velocity catalogue for all 10,702 galaxies with measured velocities, adopting the SuperCOSMOS positions as a homogeneous base. A general magnitude cut-off at R2=18.0 mag was adopted (with exceptions only for some of the new reported velocities). In general terms, we confirm the overall structure of the SSC as reported in earlier papers. However, the more extensive velocity data show finer structures, which is to be discussed in a future publication. Key words. galaxies: clusters - galaxies: distances and redshifts - cosmology: large-scale structure of Universe - astronomical data bases - catalogs - surveys 1. Introduction Superclusters of galaxies are the largest structures that can be identified in large redshift surveys of galaxies or in catalogues of clusters of galaxies, of sizes ∼ 100 Mpc. With densities a few times larger than the average density of the Universe, they are already in the non-linear regime, but still far from being virial- ized (contrary to clusters of galaxies). Thus, their complex spa- tial and velocity structure still largely reflect their initial condi- tions and their limits are ill-defined and dependent on arbitrary criteria such as density thresholds or linking lengths. Dünner et al. (2006) proposed a physical definition of super- clusters as the largest structures that remain bound in spite of the accelerated expansion of the Universe and eventually collapse to form stable, virialized, spherical clusters that separate from each other at exponentially increasing velocities in the future (e.g. Araya-Melo et al. 2009). In a spherical model, the outermost shell of a bound structure of mass M approaches an asymptotic radius (3GM/Λ) 1/3 (where G is Newton’s gravitational constant and Λ is Einstein’s cosmological constant), corresponding to an average enclosed matter density twice that associated with the cosmological constant, ρ Λ ≡ Λ/(8πG). In the present Universe (with density parameters Ω m = 0.3 and Ω Λ = 0.7), the enclosed matter density is still 1.69 times higher than this asymptotic value, corresponding to 2.36 times the current critical density ⋆ Based on observations made at Las Campanas Observatory (Chile) and Cerro-Tololo Interamerican Observatory (Chile). The complete ver- sions of Tables 2 and 4 are only available in electronic form, both at http://www.astro.puc.cl/Shapley-catalogs and at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/. or 7.87 times the current average matter density of the Universe (Chiueh & He 2002; Dünner et al. 2006). The density thresh- old set by this criterion is rather high compared to those usually chosen to define superclusters, implying that most of the mass of observationally defined superclusters is actually not bound, and the physical definition yields smaller superclusters, as found, for example, by Chon et al. (2013). In order to distinguish these two definitions, Chon et al. (2015) proposed calling the latter ‘super- stes clusters’ (‘survivor clusters’), as they are expected to survive the accelerated expansion. In the nearby Universe, at redshifts z < 0.1, several su- perclusters have been identified, including our own. Tully et al. (2014) have proposed an extension of our own supercluster, where the Local Group and Milky Way reside, from an analysis of the results of the extensive Cosmic Flows surveys undertaken by their group, which includes new galaxies found in the tradi- tional zone of avoidance. These numerous galaxies form a con- nection between the Virgo supercluster and other nearby struc- tures, including 13 Abell clusters, forming a larger entity named the Laniakea supercluster, with a diameter of 160 Mpc (equiv- alently, 12,000 km s −1 in velocity) and a total mass of 10 17 M ⊙ . However, the density enhancement and dynamical state of the Laniakea supercluster lead to the prediction (Chon et al. 2015) that the whole structure is unbound and will disperse due to the effect of dark energy in the long-term future (with some sub- structures or clusters remaining bound). The more distant ‘Shapley Concentration’ or ‘Shapley Su- percluster’ (SSC) at z ≈ 0.05 was long ago recognized as one of the largest structures in the nearby Universe (Shapley 1930). Melnick & Quintana (1981) were the first to identify the central cluster, later named A3558 (Abell, Corwin, & Olowin 1989), as Article number, page 1 of 14 Article published by EDP Sciences, to be cited as https://doi.org/10.1051/0004-6361/202037726