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Context.We identified and analysed massive quiescent galaxies (MQGs) atz ≈ 3.1 within the 2 deg²COSMOS field and explored the effect of the galaxy environment on quenching processes. By examining the variation in the quenched fraction and physical properties of these galaxies in different environmental contexts, including local densities, protoclusters, and cosmic filaments, we investigated the connection between environmental factors and galaxy quenching at cosmic noon. Aims.We selected MQGs atz ≈ 3.1 using deep photometric data from the COSMOS2020 catalogue combined with narrow-band-selected Lyman-αemitters (LAEs) from the One-hundred-square-degree DECam Imaging in Narrowbands (ODIN) survey. We performed a spectral energy distribution fitting using the code BAGPIPES to derive the star formation histories and quenching timescales. We constructed Voronoi-tessellation density maps using LAEs, and we independently selected galaxies photometrically to characterize the galaxy environments. Methods.We identified 24 MQGs atz ≈ 3.1, each of which has a stellar mass higher than 10^10.6 M_⊙. These MQGs share remarkably uniform star-formation histories, with intense starburst phases followed by rapid quenching within short timescales (≤400 Myr). The consistency of these quenching timescales suggests a universal and highly efficient quenching mechanism in this epoch. We found no significant correlation between environmental density (either local or large scale) and galaxy quenching parameters such as the quenching duration, the quenched fraction, or the timing. MQGs show no preferential distribution with respect to protoclusters or filaments compared to massive star-forming galaxies. Some MQGs reside close to gas-rich filaments, but show no evidence of rejuvenated star formation. This implies gas-heating mechanisms and not gas exhaustion. These results indicate that the quenching processes atz ≈ 3.1 likely depend little on the immediate galaxy environment. Results.Our findings suggest that environmental processes alone, such as galaxy mergers, interactions, or gas stripping, cannot fully explain the galaxy quenching atz ≈ 3.1. Internal mechanisms such as feedback from AGN, stellar feedback, virial shock heating, or morphological quenching instead play an important role in quenching. Future spectroscopic observations must confirm the quiescent nature and precise redshifts of these galaxies. Observational studies of gas dynamics, gas temperature, and ionisation conditions within and around MQGs will also clarify the physical mechanisms driving galaxy quenching during this critical epoch of galaxy evolution. 

Abstract The One-hundred-deg²DECam Imaging in Narrowbands (ODIN) survey is carrying out a systematic search for protoclusters during Cosmic Noon, using Lyα-emitting galaxies (LAEs) as tracers. Once completed, ODIN aims to identify hundreds of protoclusters at redshifts of 2.4, 3.1, and 4.5 across seven extragalactic fields, covering a total area of up to 91 deg². In this work, we report the high clustering strength of the ODIN protoclusters, determined via measurements of their cross-correlation with LAEs. Our sample consists of 150 protocluster candidates atz = 2.4 and 3.1, identified in two ODIN fields with a total area of 13.9 deg². Atz = 2.4 and 3.1, the inferred protocluster biases are $6.6_{-1.1}^{+1.3}$and $6.1_{-1.1}^{+1.3}$, corresponding to mean halo masses of $\log 〈M/M_{\odot }〉=13.53_{-0.24}^{+0.21}$and $12.96_{-0.33}^{+0.28}$, respectively. By the present day, these protoclusters are expected to evolve into virialized galaxy clusters with a mean mass of ∼10^14.5M_⊙. By comparing the observed number density of protoclusters to that of halos with the same measured clustering strength, we find that the completeness of our sample is of order unity. Finally, the similar descendant masses derived for our samples atz= 2.4 and 3.1, assuming that the halo number density remains constant, suggest that they represent similar structures observed at different cosmic epochs. As a consequence, any observed differences between the two samples can be understood as redshift evolution. The ODIN protocluster samples will thus provide valuable insights into the cosmic evolution of cluster galaxies. 

Abstract While many Lyαblobs (LABs) are found in and around several well-known protoclusters at high redshift, how they trace the underlying large-scale structure is still poorly understood. In this work, we utilize 5352 Lyαemitters (LAEs) and 129 LABs atz= 3.1 identified over a ∼9.5 deg²area in early data from the ongoing One-hundred-deg²DECam Imaging in Narrowbands (ODIN) survey to investigate this question. Using LAEs as tracers of the underlying matter distribution, we identify overdense structures as galaxy groups, protoclusters, and filaments of the cosmic web. We find that LABs preferentially reside in regions of higher-than-average density and are located in closer proximity to overdense structures, which represent the sites of protoclusters and their substructures. Moreover, protoclusters hosting one or more LABs tend to have a higher descendant mass than those which do not. Blobs are also strongly associated with filaments of the cosmic web, with ∼70% of the population being within a projected distance of ∼2.4 pMpc from a filament. We show that the proximity of LABs to protoclusters is naturally explained by their association with filaments as large cosmic structures are where many filaments converge. The contiguous wide-field coverage of the ODIN survey allows us to establish firmly a connection between LABs as a population and filaments of the cosmic web for the first time. 

Abstract We describe the survey design and science goals for One-hundred-deg²DECam Imaging in Narrowbands (ODIN), a NOIRLab survey using the Dark Energy Camera (DECam) to obtain deep (AB ∼ 25.7) narrowband images over an unprecedented area of sky. The three custom-built narrowband filters,N419,N501, andN673, have central wavelengths of 419, 501, and 673 nm and respective FWHM of 7.5, 7.6, and 10.0 nm, corresponding to Lyαatz= 2.4, 3.1, and 4.5 and cosmic times of 2.8, 2.1, and 1.4 Gyr, respectively. When combined with even deeper, public broadband data from the Hyper Suprime-Cam, DECam, and in the future, the Legacy Survey of Space and Time, the ODIN narrowband images will enable the selection of over 100,000 Lyα-emitting (LAE) galaxies at these epochs. ODIN-selected LAEs will identify protoclusters as galaxy overdensities, and the deep narrowband images enable detection of highly extended Lyαblobs (LABs). Primary science goals include measuring the clustering strength and dark matter halo connection of LAEs, LABs, and protoclusters, and their respective relationship to filaments in the cosmic web. The three epochs allow for the redshift evolution of these properties to be determined during the period known as Cosmic Noon, where star formation was at its peak. The narrowband filter wavelengths are designed to enable interloper rejection and further scientific studies by revealing [Oii] and [Oiii] atz= 0.34, Lyαand Heii1640 atz= 3.1, and Lyman continuum plus Lyαatz= 4.5. Ancillary science includes similar studies of the lower-redshift emission-line galaxy samples and investigations of nearby star-forming galaxies resolved into numerous [Oiii] and [Sii] emitting regions.