Fast evolving size of early-type galaxies at z > 2 and the role of dissipationless (dry) merging

摘要: We present the analysis of a large sample early-type galaxies (ETGs) at 0 \textless z 3 aimed tracing cosmic evolution their size and compare it with model pure dissipationless (dry) merging in Lambda cold dark matter (Lambda CDM) framework. The effective radius R-e depends on stellar mass M as R-e(M) alpha M-alpha similar to 0.5 all redshifts. redshift mass- or SDSS-normalized can be reproduced alpha(1 + z)(beta) beta -1, most massive ETGs possibly showing fastest evolutionary rate (beta -1.4). This slows down significantly -0.6 if \textgreater 2 are removed from sample, suggesting an accelerated increase typical sizes 2, especially for largest masses. A dry CDM is marginally consistent average 1.7, but predicts descendants too compact progenitor ETGs. opens crucial question what physical mechanism explain whether unclear observational bias partly responsible that.