Speaker
Description
The study of distant galaxy groups and clusters at the peak epoch of star formation has been limited by the lack of a statistically significant, homogeneously selected, and spectroscopically confirmed sample, with most wok focusing on individual case studies. We carried out a large NOEMA program, the Noema formIng Cluster survEy (NICE), to spectroscopically confirm the nature of 65 (proto)cluster candidates at z ~2-4. 70% of the candidates host at least two galaxies with CO lines at concordant redshifts. These targets are selected as overdensities of massive galaxies at z > 2 with large total infrared luminosities. We systematically examine the star formation and cold gas properties of the protocluster members and find that SFRtot/Mhalo steeply increases with redshift, up to two dex higher than the field at z > 2. This rise is driven not by an excess of starbursts but by a concentration of massive, gas-rich galaxies (M⋆>10^10 M⊙) in the cluster cores. JWST observations of the NICE prototype protocluster, CL J1001 reveal a top-heavey stellar mass function that suports this picture. The star-forming member galaxies exhibit higher μgas and τgas than their field counterparts. Recent JWST/NIRCam imaging further shows that the member galaxies are more compact than their field counterparts, consistent with ongoing compaction processes in these gas-rich environments. Together, these results suggest that dense environments can sustain star formation through substantial gas reservoirs, promoting early mass assembly and the eventual formation of massive ellipticals in cluster centers. Further investigation of the underlying physical processes will benefit from observations with state of the art facilities, such as VLT/MUSE to trace cold gas filaments and Gemini/FLAMINGOS-2 for membership identification, etc.
