A z=1.85 galaxy group in CEERS: evolved, dustless, massive intra-halo light and a brightest group galaxy in the making

Abstract

We present CEERS JWST/NIRCam imaging of a massive galaxy group at z=1.85, to explore the early JWST view on massive group formation in the distant Universe. The group contains >16 members (including 6 spectros. confirmations) down to log10(Mstar/Msun)=8.5, including the brightest group galaxy (BGG) in the process of actively assembling at this redshift. The BGG is comprised of multiple merging components extending ~3.6" (30kpc) across the sky. The BGG contributes 69% of the group's total galactic stellar mass, with one of the merging components containing 76% of the total mass of the BGG and a SFR>1810Msun/yr. Most importantly, we detect intra-halo light (IHL) in several HST and JWST/NIRCam bands, allowing us to construct a state-of-the-art rest-frame UV-NIR Spectral Energy Distribution of the IHL for the first time at this high redshift. This allows stellar population characterisation of both the IHL and member galaxies, as well as the morphology distribution of group galaxies vs. their star-formation activity when coupled with Herschel data. We create a stacked image of the IHL, giving us a sensitivity to extended emission of 28.5 mag/arcsec2 at rest-frame 1um. We find that the IHL is extremely dust poor (Av~0), containing an evolved stellar population of log10(t50/yr)=8.8, corresponding to a formation epoch for 50% of the stellar material 0.63Gyr before z=1.85. There is no evidence of ongoing star-formation in the IHL. The IHL in this group at z=1.85 contributes ~10% of the total stellar mass, comparable with what is observed in local clusters. This suggests that the evolution of the IHL fraction is more self-similar with redshift than predicted by some models, challenging our understanding of IHL formation during the assembly of high-redshift clusters. JWST is unveiling a new side of group formation at this redshift, which will evolve into Virgo-like structures in the local Universe.

14 pages + appendix, 11 figures, 4 tables. Accepted to A&A on 15th May 2023

References in corpus (25)

• The James Webb Space Telescope
• Star Formation in AEGIS Field Galaxies since z=1.1 : The Dominance of Gradually Declining Star Formation, and the Main Sequence of Star-Forming Galaxies
• An ultra-deep near-infrared spectrum of a compact quiescent galaxy at z=2.2
• 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts and Stellar Masses
• Detection of quiescent galaxies in a bicolor sequence from z=0-2
• Star formation efficiency in galaxy interactions and mergers: a statistical study
• A Long Time Ago in a Galaxy Far, Far Away: A Candidate z ~ 12 Galaxy in Early JWST CEERS Imaging
• The SCUBA-2 Cosmology Legacy Survey: 850um maps, catalogues and number counts
• The Importance of Mergers for the Origin of Intracluster Stars in Cosmological Simulations of Galaxy Clusters
• CEERS Epoch 1 NIRCam Imaging: Reduction Methods and Simulations Enabling Early JWST Science Results
• The Hierarchical Build-Up of Massive Galaxies and the Intracluster Light since z=1
• The Formation and Evolution of Intracluster Light
• Diffuse Optical Light in Galaxy Clusters II: Correlations with Cluster Properties
• Intracluster Light at the Frontier II: The Frontier Fields Clusters
• Compton thick active galactic nuclei in Chandra surveys
• The SCUBA-2 Cosmology Legacy Survey: The EGS deep field I - Deep number counts and the redshift distribution of the recovered Cosmic Infrared Background at 450 and 850 um
• Evidence for Cold-stream to Hot-accretion Transition as Traced by Lyα Emission from Groups and Clusters at 2 < z < 3.3
• The bending of the star-forming main sequence traces the cold- to hot-accretion transition mass over 0<z<4
• Intracluster light is already abundant at redshift beyond unity
• The Origins of UV-optical Color Gradients in Star-forming Galaxies at z ~ 2: Predominant Dust Gradients But Negligible sSFR Gradients
• Galaxy and Mass Assembly (GAMA): Extended Intra-Group Light in a group at $z=0.2$ from deep Hyper-Suprime Cam images
• Deciphering an evolutionary sequence of merger stages in infrared-luminous starburst galaxies at z ~ 0.7
• Hidden Cooling Flows in Clusters of Galaxies II: A Wider Sample
• Probing Intra-Halo Light with Galaxy Stacking in CIBER Images
• Bulge formation inside quiescent lopsided stellar disks: connecting accretion, star formation and morphological transformation in a z ~ 3 galaxy group

Cited by in corpus (6)

• Cosmic Vine: A z=3.44 large-scale structure hosting massive quiescent galaxies
• JWST/CEERS sheds light on dusty star-forming galaxies: forming bulges, lopsidedness and outside-in quenching at cosmic noon
• Delving deep: a population of extremely dusty dwarfs observed by JWST
• NOEMA formIng Cluster survEy (NICE): Characterizing eight massive galaxy groups at $1.5<z<4$ in the COSMOS field
• The intragroup light in KiDS+GAMA groups: A stacking analysis
• Euclid: A blue galaxy population and a brightest cluster galaxy in the making in a $z\sim 1.74$ MaDCoWS2 galaxy cluster candidate