Abstract We explore the redshift evolution of the dynamical properties of massive clusters and their brightest cluster galaxies (BCGs) at z < 2 based on the IllustrisTNG-300 simulation. We select 270 massive clusters with M 200 < 10 14 M ⊙ at z = 0 and trace their progenitors based on merger trees. From 67 redshift snapshots covering z < 2, we compute the 3D subhalo velocity dispersion as a cluster velocity dispersion ( σ cl ). We also calculate the 3D stellar velocity dispersion of the BCGs ( σ *,BCG ). Both σ cl and σ *,BCG increase as the universe ages. The BCG velocity dispersion grows more slowly than the cluster velocity dispersion. Furthermore, the redshift evolution of the BCG velocity dispersion shows dramatic changes at some redshifts resulting from dynamical interaction with neighboring galaxies (major mergers). We show that σ *,BCG is comparable with σ cl at z > 1, offering an interesting observational test. The simulated redshift evolution of σ cl and σ *,BCG generally agrees with an observed cluster sample for z < 0.3, but with large scatter. Future large spectroscopic surveys reaching to high redshift will test the implications of the simulations for the mass evolution of both clusters and their BCGs.
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Clocking the formation of today’s largest galaxies: wide field integral spectroscopy of brightest cluster galaxies and their surroundings
The formation and evolution of local brightest cluster galaxies (BCGs) is investigated by determining the stellar populations and dynamics from the galaxy core, through 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 ICL spectra are best modelled with populations that are younger and less metal-rich than those of the BCG cores. The average BCG core age of the sample is $\rm 13.3\pm 2.8\, Gyr$ and the average metallicity is $\rm [Fe/H] = 0.30\pm 0.09$, whereas for the ICL the average age is $\rm 9.2\pm 3.5\, Gyr$ and the average metallicity is $\rm [Fe/H] = 0.18\pm 0.16$. 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.
more » « less- Award ID(s):
- 1814375
- NSF-PAR ID:
- 10126257
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 491
- Issue:
- 2
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- p. 2617-2638
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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