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Clocking The Formation Of Today’s Largest Galaxies: Intracluster Light And Nearby Companions

Presentation #124.01 in the session “Galaxies”.

Published onJun 18, 2021
Clocking The Formation Of Today’s Largest Galaxies: Intracluster Light And Nearby Companions

The formation and evolution of local brightest cluster galaxies (BCGs) is investigated by comparing the stellar populations and dynamics of the galaxy, the intracluster light (ICL), and nearby companions. Integral spectroscopic data of 23 local BCGs observed out to 4 re is collected. Stellar population synthesis codes are used to determine the age, metallicity, velocity, and velocity dispersion of stars within regions such as the galaxy core, the intracluster light, and the nearby companions, when available. The ICL spectra are best modeled with populations that are younger and less metal-rich than those of the BCG cores. The velocity dispersion profile is seen to be rising or flat in most of the sample (17/23), and those with rising values reach the value of the host cluster’s velocity dispersion in several cases. Thirty-six Companions to the 23 BCG are identified, 83+5-11% have dynamical friction timescales less than 0.5 Gyr, and have ≥ 80% probability of bound to their respective BCG. Brighter BCGs are found to have fewer companions. The results are consistent with the idea that the BCG cores and inner regions formed quickly and long ago, with the outer regions and ICL forming more recently, and continuing to assemble through minor merging.


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