1 research outputs found
The Origin of Massive Compact Galaxies: Lessons from IllustrisTNG
We investigate the formation and evolution of z=0 massive compact galaxies
(MCGs) in the IllustrisTNG cosmological simulation. We found that, as in
observations, MCGs are mainly old (median age Gyr), have
super-solar metallicities (median ) and are
-enhanced (median ). The age distribution extends
to younger ages, however, and a few MCGs are as young as Gyr. In
general, MCGs assemble their mass early and accrete low angular momentum gas,
significantly increasing their mass while growing their size much slower. A
small fraction of MCGs follow another evolutionary path, going through a
compaction event, with their sizes shrinking by 40% or more. The accretion of
low angular momentum gas leads to enhanced SMBH growth, and MCGs reach the
threshold SMBH mass of - when kinetic
AGN feedback kicks in and quenches the galaxy - earlier than non-compact
galaxies. Comparing MCGs to a sample of median-sized quiescent galaxies matched
in effective velocity dispersion, we find that their accretion histories are
very different. 71% of MCGs do not merge after quenching compared to 37% of
median-sized quiescent galaxies. Moreover, tracing these populations back in
time, we find that at least a third of median-sized quiescent galaxies do not
have a compact progenitor, underscoring that both dry mergers and progenitor
bias effects are responsible for the differences in the kinematics and stellar
population properties of MCGs and median-sized quiescent galaxies.Comment: 15 pages, 15 figures (not including appendices). Accepted for
publication in the Monthly Notices of the Royal Astronomical Societ