The Formation and Evolution of Massive Galaxies
  The discovery of massive galaxies at high redshifts, especially the passive
ones, poses a big challenge for the current standard galaxy formation models.
Here we use the semi-analytic galaxy formation model developed by Henriques et
al. to explore the formation and evolution of massive galaxies (MGs,
stellar-mass $M_{*}> 10^{11}$ M$_{\odot}$). Different from previous works, we
focus on the ones just formed (e.g. just reach $\simeq 10^{11}$ M$_{\odot}$).
We find that most of the MGs are formed around $z=0.6$, with the earliest
formation at $z>4$. Interestingly, although most of the MGs in the local
Universe are passive, we find that only $13\%$ of the MGs are quenched at the
formation time. Most of the quenched MGs at formation already hosts a very
massive supermassive black hole (SMBH) which could power the very effective AGN
feedback. For the star-forming MGs, the ones with more massive SMBH prefer to
quench in shorter timescales; in particular, those with $M_{\textrm{SMBH}} >
10^{7.5}$ M$_{\odot}$ have a quenching timescale of $\sim 0.5$ Gyr and the
characteristic $M_{\textrm{SMBH}}$ depends on the chosen stellar mass threshold
in the definition of MGs as a result of their co-evolution. We also find that
the "in-situ" star formation dominates the stellar mass growth of MGs until
they are formed. Over the whole redshift range, we find the quiescent MGs
prefer to stay in more massive dark matter halos, and have more massive SMBH
and less cold gas masses. Our results provide a new angle on the whole life of
the growth of MGs in the Universe.
