The number density of superdense early-type galaxies at 1<z<2 and the local cluster galaxies - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




The number density of superdense early-type galaxies at 1<z<2 and the local cluster galaxies - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: Many of the early-type galaxies observed so far at z>1 turned out to havesmaller radii with respect to that of a typical present-day early-type galaxywith comparable mass. This has generated the conviction that in the pastearly-type galaxies were more compact, hence denser, and that as a consequence,they should have increased their radius across the time to reconcile with thepresent-day ones. However, observations have not yet established whether thepopulation of early-types in the early Universe was fully represented bycompact galaxies nor if they were so much more numerous than in the present-dayUniverse to require an evolution of their sizes. Here we report the results ofa study based on a complete sample of 34 early-type galaxies at0.9~1.5 suggests thattheir build-up taken place in the first 3-4 Gyr, followed distinct paths. Also,we find that the number density of compact early-types at ~1.5 is consistentwith the lower limits of the local number density of compact early-typesderived from local clusters of galaxies. The similar number of compactearly-types found in the early and in the present day Universe frustrates thehypothesized effective radius evolution while provides evidence that alsocompact ETGs were as we see them today 9-10 Gyr ago. Finally, the fact that atleast most of the compact ETGs at high-z are accounted for by compactearly-types in local cluster of galaxies implies that the former are the directprogenitors of the compact early-type cluster galaxies establishing a directlink between environment and early phases of assembly of ETGs.



Author: P. Saracco, M. Longhetti, A. Gargiulo

Source: https://arxiv.org/







Related documents