A proto-cluster at z=2.45

TL;DR

This paper confirms a proto-cluster at redshift 2.45, analyzes its properties and evolution, and discusses the diversity of its potential descendants, highlighting the complexity of early structure formation.

Contribution

It provides spectroscopic confirmation of a high-redshift proto-cluster and compares its properties with simulations to understand its evolution into massive dark matter haloes.

Findings

Proto-cluster has an overdensity of 10 at z=2.45.

Structures at this redshift evolve into massive haloes by z=0.

Optical selection captures diverse proto-clusters with varied descendants.

Abstract

We present the spectroscopic confirmation of a $z=2.45$ proto-cluster. Its member galaxies lie within a radius of 1.4Mpc (physical) on the sky and within $\Delta v \pm 700$km/s along the line of sight. We estimate an overdensity of 10, suggesting that the structure has made the turn-around but is not assembled yet. Comparison to the Millennium simulation suggests that analogous structures evolve into $10^{14}-10^{15}$M$_{\odot}$/h type dark matter haloes by $z=0$ qualifying the notion of "proto-cluster". The search for the complete census of mock progenitor galaxies at $z\sim2.5$ of these massive $z=0$ mock clusters reveals that they are widely spread over areas with a diameter of 3-20Mpc. This suggests that the optical selection of such proto-clusters can result in a rich diversity regarding their $z=0$ descendants. We also searched for signs of environmental differentiation in this proto-cluster. Whilst we see a weak trend for more massive and more quiescent galaxies in the proto-cluster, this is not statistically significant.