Avoiding Progenitor Bias: The Structural and Mass Evolution of Brightest Group and Cluster Galaxies in Hierarchical Models since z≾1
The mass and structural evolution of massive galaxies is one of the hottest topics in galaxy formation. This is because it may reveal invaluable insights into the still debated evolutionary processes governing the growth and assembly of spheroids. However, direct comparison between models and observations is usually prevented by the so-called progenitor bias, i.e., new galaxies entering the observational selection at later epochs, thus eluding a precise study of how pre-existing galaxies actually evolve in size. To limit this effect, we here gather data on high-redshift brightest group and cluster galaxies, evolve their (mean) host halo masses down to z = 0 along their main progenitors, and assign as their "descendants" local Sloan Digital Sky Survey central galaxies matched in host halo mass. At face value, the comparison between high redshift and local data suggests a noticeable increase in stellar mass of a factor of ≳ 2 since z ~ 1, and of ≳ 2.5 in mean effective radius. We then compare the inferred stellar mass and size growth with those predicted by hierarchical models for central galaxies, selected at high redshifts to closely match the halo and stellar mass bins as in the data. Only hierarchical models characterized by very limited satellite stellar stripping and parabolic orbits are capable of broadly reproducing the stellar mass and size increase of a factor of ~2-4 observed in cluster galaxies since z ~ 1. The predicted, average (major) merger rate since z ~ 1 is in good agreement with the latest observational estimates.
Additional Information© 2015 American Astronomical Society. Received 2014 September 10; accepted 2014 December 10; published 2015 March 24. F.S. acknowledges partial support from a Marie Curie grant. S.M. acknowledges financial support from the Institut Universitaire de France (IUF), of which she is senior member. F.S. thanks Bruno Henriquez and Chervin Laporte for interesting discussions. This work is based on data obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory (JPL), California Institute of Technology (Caltech), under a contract with NASA. Support was provided by NASA through contract number 1439211 issued by JPL/Caltech. V.B. is supported financially by the National Research Foundation of South Africa. We thank the referee for useful comments and suggestions.
Published - 0004-637X_802_2_73.pdf
Submitted - 1501.02800v3.pdf