The formation and evolution of local brightest cluster galaxies ( BCGs ) is investigated by determining the stellar populations and dynamics from the galaxy core , though the outskirts and into the intracluster light ( ICL ) .
Integral spectroscopy of 23 BCGs observed out to 4 r _ { e } is collected and high signal-to-noise regions are identified .
Stellar population synthesis codes are used to determine the age , metallicity , velocity , and velocity dispersion of stars within each region .
The intracluster light ( ICL ) spectra are best modeled with populations that are younger and less metal-rich than those of the BCG cores .
The average BCG core age of the sample is 13.3 \pm 2.8 Gyr and the average metallicity is [ Fe / H ] = 0.30 \pm 0.09 , whereas for the ICL the average age is 9.2 \pm 3.5 Gyr and the average metallicity is [ Fe / H ] = 0.18 \pm 0.16 .
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 .
The most extended BCGs are closest to the peak of the cluster ’ s X-ray luminosity .
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 .
Any recent star formation in the BCGs is a minor component , and is associated with the cluster cool core status .