Using new spectroscopic observations obtained as part of the VIMOS Ultra-Deep Survey ( VUDS ) , we performed a systematic search for overdense environments in the early universe ( z > 2 ) and report here on the discovery of Cl J0227-0421 , a massive protocluster at z = 3.29 .
This protocluster is characterized by both the large overdensity of spectroscopically confirmed members , \delta _ { gal } = 10.5 \pm 2.8 , and a significant overdensity in photometric redshift members .
The halo mass of this protocluster is estimated by a variety of methods to be \sim 3 \times 10 ^ { 14 } \mathcal { M } _ { \odot } at z \sim 3.3 , which , evolved to z = 0 results in a halo mass rivaling or exceeding that of the Coma cluster .
The properties of 19 spectroscopically confirmed member galaxies are compared with a large sample of VUDS/VVDS galaxies in lower density field environments at similar redshifts .
We find tentative evidence for an excess of redder , brighter , and more massive galaxies within the confines of the protocluster relative to the field population , which suggests that we may be observing the beginning of environmentally induced quenching .
The properties of these galaxies are investigated , including a discussion of the brightest protocluster galaxy , which appears to be undergoing vigorous coeval nuclear and starburst activity .
The remaining member galaxies appear to have characteristics that are largely similar to the field population .
Though we find weaker evidence of the suppression of the median star formation rates among and differences in the stacked spectra of member galaxies with respect to the field , we defer any conclusions about these trends to future work with the ensemble of protostructures that are found in the full VUDS sample .