(Toni+, 2025) ================================================================================ The COSMOS-Web deep galaxy group catalog up to z=3.7 Greta Toni, Ghassem Gozaliasl, Matteo Maturi, Lauro Moscardini, Alexis Finoguenov, Gianluca Castignani, Fabrizio Gentile, Kaija Virolainen, M. Caitlin Casey, S. Jeyhan Kartaltepe, B. Hollis Akins, Natalie Allen, C. Rafael Arango-Toro, Arif Babul, Malte Brinch, E. Nicole Drakos, L. Andreas Faisst, Maximilien Franco, E. Richard Griffiths, Santosh Harish, Günther Hasinger, Olivier Ilbert, Shuowen Jin, Ali Ahmad Khostovan, M. Anton Koekemoer, Maarit Korpi-Lagg, L. Rebecca Larson, Jitrapon Lertprasertpong, Daizhong Liu, Georgios Magdis, Richard Massey, Henry Joy McCracken, Jed McKinney, Louise Paquereau, Jason Rhodes, E. Brant Robertson, Mark Sargent, Marko Shuntov, Masayuki Tanaka, Sina Taamoli, Elmo Tempel, Sune Toft, Eleni Vardoulaki, Lilan Yang =2025A&A...697A.197T 2025A&A...697A.197T ================================================================================ Keywords: galaxies: clusters: general / galaxies: evolution / galaxies: groups: general / galaxies: luminosity function, mass function / galaxies: high-redshift / large-scale structure of Universe Abstract: Galaxy groups with total masses below $\sim 10^{14} \, M_\odot$ and up to a few tens of members are the most common galaxy environment, marking the transition between the field and the most massive galaxy clusters. In this framework, identifying and studying groups plays a crucial role in understanding structure formation and galaxy evolution. Despite the challenges in detecting such relatively small structures, modern deep surveys allow us to build well-characterized samples of galaxy groups up to the regime where the structures we observe today were taking shape. We aim to build the largest deep catalog of galaxy groups to date over the COSMOS-Web field effective area of 0.45 deg$^2$. We leveraged the deep imaging, high resolution, and high- quality photometry from the James Webb Space Telescope observations of the COSMOS-Web field. We used the recent COSMOS-Web photometric catalog with sky position, photometric redshift, and magnitude in a reference band for each selected galaxy. We performed the group search with the Adaptive Matched Identifier of Clustered Objects (AMICO) algorithm, a linear matched filter based on an analytical model for the cluster/group signal. This algorithm has already been tested in wide and deep field surveys, including a successful application to COSMOS data up to $z=2$. In this work, we tested the algorithm's performances at even higher redshift and searched for protocluster cores and groups at $z>2$. To benchmark this relatively unexplored regime, we compiled a list of known protoclusters in COSMOS at $2 \leq z \leq 3.7$ and matched them with our detections. We studied the spatial connection between detected cores through a clustering analysis. We estimated the purity and the completeness of our group sample by creating data-driven mocks via a Monte Carlo approach with the SinFoniA code and linked signal-to-noise to purity levels to define desired purity thresholds. We detected 1678 groups in the COSMOS-Web field up to $z=3.7$ with a purity level of $\sim 77\%$, providing a deep catalog of galaxy members that extends nearly two magnitudes deeper than the previous application of AMICO to COSMOS. Around 670 groups have been detected with a purity of 90\%. Our catalog includes more than 850 groups whose photometric redshift was confirmed by assigning robust spectroscopic counterparts. This catalog of galaxy groups is the largest ultra-deep group sample built on JWST observations so far and offers a unique opportunity to explore several aspects of galaxy evolution in different environments spanning $\sim$12 Gyr and study groups themselves, from the least rich population of groups to the formation of the most massive clusters. Description: We present the COSMOS-Web deep galaxy group catalog obtained by applying the AMICO algorithm to the COSMOS-Web photometric galaxy catalog, the result of the largest contiguous JWST observation to date. The catalog contains 1678 candidate groups and protocluster cores up to z=3.7. The group catalog is accompanied by the list of associated members. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . this file groups.txt 130 1678 catalog of candidate group detections memberships.txt 38 1745652 galaxy memberships with probability>0.005 -------------------------------------------------------------------------------- Byte-by-byte Description of file: groups.txt -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- ID [1/1816] Group identification number 6- 14 F9.5 deg RA [149.66/150.57] Right Ascension (R.A.) 16- 24 F9.7 deg DEC [1.73/2.68] Declination (Dec) 26- 29 F4.2 --- Z [0.08/3.7] AMICO group redshift 31- 39 F9.7 --- SN [1.27/6.66] signal-to-noise ratio, including background and group contributions 41- 50 F10.7 --- SN_NOCL [6.0/43.11] signal-to-noise ratio, including only background 52- 61 F10.8 --- AMP [0.12/2.52] Signal amplitude 63- 73 F11.9 --- MSKFRC [0.02/0.8] Fraction of the group inaccessible because of mask 75- 84 F10.6 --- LAMBDA [13.99/455.96] Apparent richness based on the galaxy probability assoc. (visible number of galaxies) 86- 95 F10.7 --- LAMBDA_STAR [2.01/77.57] Intrinsic richness (as LAMBDA but m