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Abstract We report the first statistical analyses of [Cii] and dust continuum observations in six strong Oiabsorber fields at the end of the reionization epoch obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Combined with one [Cii] emitter reported in Wu et al., we detect one Oi-associated [Cii] emitter in six fields. At redshifts of Oiabsorbers in nondetection fields, no emitters are brighter than our detection limit within impact parameters of 50 kpc and velocity offsets between ±200 km s⁻¹. The averaged [Cii]-detection upper limit is <0.06 Jy km s⁻¹(3σ), corresponding to the [Cii] luminosity ofL_[CII]< 5.8 × 10⁷L_⊙and the [Cii]-based star formation rate of SFR_[CII]<5.5M_⊙yr⁻¹. Cosmological simulations suggest that only ∼10^−2.5[Cii] emitters around Oiabsorbers have comparable SFR to our detection limit. Although the detection in one out of six fields is reported, an order of magnitude number excess of emitters obtained from our ALMA observations supports that the contribution of massive galaxies that caused the metal enrichment cannot be ignored. Further, we also found 14 tentative galaxy candidates with a signal-to-noise ratio of ≈4.3 at large impact parameters (>50 kpc) and having larger outflow velocities within ±600 km s⁻¹. If these detections are confirmed in the future, then the mechanism of pushing metals at larger distances with higher velocities needs to be further explored from the theoretical side. 

Abstract We present an analysis of the number density of galaxies as a function of stellar mass (i.e., the stellar mass function (SMF)) in the COSMOS field atz∼ 3.3, making a comparison between the SMF in overdense environments and the SMF in the coeval field. In particular, this region contains the Elentári proto-supercluster, a system of six extended overdensities spanning ∼70 cMpc on a side. A clear difference is seen in the high-mass slope of these SMFs, with overdense regions showing an increase in the ratio of high-mass galaxies to low-mass galaxies relative to the field, indicating a more rapid buildup of stellar mass in overdense environments. This result qualitatively agrees with analyses of clusters atz∼ 1, though the differences between protocluster and field SMFs atz∼ 3.3 are smaller. While this is consistent with overdensities enhancing the evolution of their member galaxies, potentially through increased merger rates, whether this enhancement begins in protocluster environments or even earlier in group environments is still unclear. Though the measured fractions of quiescent galaxies between the field and overdense environments do not vary significantly, implying that this stellar mass enhancement is ongoing and any starbursts triggered by merger activity have not yet quenched, we note that spectroscopic observations are biased toward star-forming populations, particularly for low-mass galaxies. If mergers are indeed responsible, high-resolution imaging of Elentári and similar structures at these early epochs should then reveal increased merger rates relative to the field. Larger samples of well-characterized overdensities are necessary to draw broader conclusions in these areas. 

ABSTRACT We present six spectroscopically confirmed massive protostructures, spanning a redshift range of 2.5 < z < 4.5 in the Extended Chandra Deep Field South (ECDFS) field discovered as part of the Charting Cluster Construction in VUDS and ORELSE (C3VO) survey. We identify and characterize these remarkable systems by applying an overdensity measurement technique on an extensive data compilation of public and proprietary spectroscopic and photometric observations in this highly studied extragalactic field. Each of these six protostructures, i.e. a large scale overdensity (volume >9000 cMpc3) of more than 2.5σδ above the field density levels at these redshifts, have a total mass Mtot ≥ 1014.8 M⊙ and one or more highly overdense (overdensity$$\, \gt 5\sigma _{\delta }$$) peaks. One of the most complex protostructures discovered is a massive (Mtot = 1015.1M⊙) system at z ∼ 3.47 that contains six peaks and 55 spectroscopic members. We also discover protostructures at z ∼ 3.30 and z ∼ 3.70 that appear to at least partially overlap on sky with the protostructure at z ∼ 3.47, suggesting a possible connection. We additionally report on the discovery of three massive protostructures at z = 2.67, 2.80, and 4.14 and discuss their properties. Finally, we discuss the relationship between star formation rate and environment in the richest of these protostructures, finding an enhancement of star formation activity in the densest regions. The diversity of the protostructures reported here provide an opportunity to study the complex effects of dense environments on galaxy evolution over a large redshift range in the early Universe. 

Streams of intergalactic gas enriched by previous star formation were observed spiraling toward a massive galaxy.