We study the colors and metallicities of the brightest cluster galaxies (BCGs) and intracluster light (ICL) in galaxy groups and clusters, as predicted by a semi-analytic model of galaxy formation, coupled with a set of high-resolution N-body simulations. The model assumes stellar stripping and violent relaxation processes during galaxy mergers to be the main channels for the formation of the ICL. We find that BCGs are more metal-rich and redder than the ICL, at all redshifts once the ICL starts to form (z ∼ 1). In good agreement with several observed data, our model predicts negative radial metallicity and color gradients in the BCG+ICL system. By comparing the typical colors of the ICL with those of satellite galaxies, we find that the mass and metals in the ICL come from galaxies of different mass, depending on the redshift. Stripping of low-mass galaxies, 9 < log M ∗ < 10, is the most important contributor in the early stages of ICL formation, but the bulk of the mass/metals contents are given by intermediate/massive galaxies, 10 < log M ∗ < 11, at lower redshift. Our analysis supports the idea that stellar stripping is more important than galaxy mergers in building up the ICL, and highlights the importance of colors/metallicity measurements for understanding the formation and evolution of the ICL.
Bibliographical noteFunding Information:
S.K.Y. and E.C. acknowledge support from the Korean National Research Foundation (NRF-2017R1A2A1A05001116) and from the Brain Korea 21 Plus Program (21A20131500002). This study was performed under the umbrella of the joint collaboration between Yonsei University Observatory and the Korean Astronomy and Space Science Institute. X.K. acknowledges financial support by the 973 Program (2015CB857003) and the NSFC (No.11333008).
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All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science