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Intracluster light in the core of z ∼ 2 galaxy proto-clusters

Werner, S. V.; Hatch, N. A.; Matharu, J.; Gonzalez, A. H.; Bahé, Y. M.; Mei, S.; Noirot, G.; Wylezalek, D.


S. V. Werner

J. Matharu

A. H. Gonzalez

Y. M. Bahé

S. Mei

G. Noirot

D. Wylezalek


Intracluster light is thought to originate from stars that were ripped away from their parent galaxies by gravitational tides and galaxy interactions during the build up of the cluster. The stars from such interactions will accumulate over time, so semi-analytic models suggest that the abundance of intracluster stars is negligible in young proto-clusters at z∼ 2 and grows to around a quarter of the stellar mass in the oldest, most mature clusters. In contrast to these theoretical expectations, we report on the detection of intracluster light within two proto-clusters at z= 2 using deep HST images. We use the colour of the intracluster light to estimate its mass-to-light ratio in annuli around the brightest cluster galaxies (BCG), up to a radius of 100 kpc. We find that 54 ± 5 per cent and 71 ± 3 per cent of the stellar mass in these regions is located more than 10 kpc away from the BCGs in the two proto-clusters. This low concentration is similar to BCGs in lower redshift clusters, and distinct from other massive proto-cluster galaxies. This suggests that intracluster stars are already present within the core 100 kpc of proto-clusters. We compare these observations to the Hydrangea hydrodynamical galaxy cluster simulations and find that intracluster stars are predicted to be a generic feature of group-sized haloes at z= 2. These intracluster stars will gradually move further away from the BCG as the proto-cluster assembles into a cluster.

Journal Article Type Article
Acceptance Date May 8, 2023
Online Publication Date May 10, 2023
Publication Date 2023-07
Deposit Date May 16, 2023
Publicly Available Date May 25, 2023
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press (OUP)
Peer Reviewed Peer Reviewed
Volume 523
Issue 1
Pages 91-104
Keywords galaxies: clusters: general, galaxies: evolution, galaxies: photometry
Public URL
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