# Revealing Dust Obscured Star Formation in CLJ1449+0856, a Cluster at z=2

## TL;DR

This study uses multi-wavelength data to reveal intense star formation activity in the galaxy cluster CLJ1449 at redshift 2, showing a reversal of the typical star formation-density relation and evidence of ongoing accretion.

## Contribution

It provides a detailed analysis of star formation rates in a high-redshift cluster using combined submillimeter, optical, and infrared data, revealing unprecedented star formation density profiles.

## Key findings

- Star formation rate varies between 20-1600 M$_{ ext{odot}}$ yr$^{-1}$ across the cluster.
- Central 0.5 Mpc region has a total star formation rate of 800$ extpm$200 M$_{ ext{odot}}$ yr$^{-1}$.
- Star formation rate density is five orders of magnitude higher than field values.

## Abstract

We present SCUBA-2 450$\mu$m and 850$\mu$m data of the mature redshift 2 cluster CLJ1449. We combine this with archival Herschel data to explore the star forming properties of CLJ1449. Using high resolution ALMA and JVLA data we identify potentially confused galaxies, and use the Bayesian inference tool XID+ to estimate fluxes for them. Using archival optical and near infrared data with the energy-balance code CIGALE we calculate star formation rates, and stellar masses for all our cluster members, and find the star formation rate varies between 20-1600M$_{\odot}$yr$^{-1}$ over the entire 3Mpc radial range. The central 0.5Mpc region itself has a total star formation rate of 800$\pm$200M$_{\odot}$yr$^{-1}$, which corresponds to a star formation rate density of (1.2$\pm$0.3)$\times$10$^{4}$M$_{\odot}$yr$^{-1}$Mpc$^{-3}$, which is approximately five orders of magnitude greater than expected field values. When comparing this cluster to those at lower redshifts we find that there is an increase in star formation rate per unit volume towards the centre of the cluster. This indicates that there is indeed a reversal in the star formation/density relation in CLJ1449. Based on the radial star-formation rate density profile, we see evidence for an elevation in the star formation rate density, even out to radii of 3Mpc. At these radii the elevation could be an order of magnitude greater than field values, but the exact number cannot be determined due to ambiguity in the redshift associations. If this is the case it would imply that this cluster is still accreting material which is possibly interacting and undergoing vigorous star-formation.