TY - JOUR
T1 - A z = 1.85 galaxy group in CEERS
T2 - Evolved, dustless, massive intra-halo light and a brightest group galaxy in the making
AU - Coogan, Rosemary T.
AU - Daddi, Emanuele
AU - Le Bail, Aurélien
AU - Elbaz, David
AU - Dickinson, Mark
AU - Giavalisco, Mauro
AU - Gómez-Guijarro, Carlos
AU - De La Vega, Alexander
AU - Bagley, Micaela
AU - Finkelstein, Steven L.
AU - Franco, Maximilien
AU - Cooray, Asantha R.
AU - Behroozi, Peter
AU - Bisigello, Laura
AU - Casey, Caitlin M.
AU - Ciesla, Laure
AU - Dimauro, Paola
AU - Finoguenov, Alexis
AU - Koekemoer, Anton M.
AU - Lucas, Ray A.
AU - Pérez-González, Pablo G.
AU - Aaron Yung, L. Y.
AU - Arrabal Haro, Pablo
AU - Kartaltepe, Jeyhan S.
AU - Jogee, Shardha
AU - Papovich, Casey
AU - Pirzkal, Nor
AU - Wilkins, Stephen M.
N1 - Publisher Copyright:
© 2023 The Authors.
PY - 2023/9/1
Y1 - 2023/9/1
N2 - 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 six spectroscopic confirmations) down to log10(M∗/M·) = 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 (30 kpc) 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 star formation rate > 1810 M· yr-1. Most importantly, we detected 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 versus their star formation activity when coupled with Herschel data. We created a stacked image of the IHL, giving us a sensitivity to extended emission of 28.5 mag arcsec-2 at rest-frame 1 μm. 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 0.63 Gyr 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.
AB - 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 six spectroscopic confirmations) down to log10(M∗/M·) = 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 (30 kpc) 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 star formation rate > 1810 M· yr-1. Most importantly, we detected 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 versus their star formation activity when coupled with Herschel data. We created a stacked image of the IHL, giving us a sensitivity to extended emission of 28.5 mag arcsec-2 at rest-frame 1 μm. 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 0.63 Gyr 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.
KW - Galaxies: evolution
KW - Galaxies: groups: general
KW - Galaxies: high-redshift
KW - Galaxies: interactions
KW - Galaxies: starburst
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U2 - 10.1051/0004-6361/202346172
DO - 10.1051/0004-6361/202346172
M3 - Article
AN - SCOPUS:85168717190
SN - 0004-6361
VL - 677
JO - Astronomy and astrophysics
JF - Astronomy and astrophysics
M1 - A3
ER -