Yuxiang Qin1, Simon J. Mutch1, Alan R. Duffy2, Paul M. Geil1, Gregory B. Poole2, Andrei Mesinger3 and J. Stuart B. Wyithe1
School of Physics, University of Melbourne, Parkville, VIC 3010, Australia
Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn, VIC 3122, Australia
Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
Massive quiescent galaxies are thought to have formed stars rapidly at early times followed by a long period of quiescence. The recent discovery of a massive quiescent galaxy, ZF-COSMOS-20115 at z ∼ 4, only 1.5 Gyr after the Big Bang, places new constraints on galaxy growth and the role of feedback in early star formation. Spectroscopic follow-up confirmed ZF-COSMOS-20115 as a massive quiescent galaxy at z = 3.717 with an estimated stellar mass of ∼1e11M⊙, showing no evidence of recent star formation. We use the Meraxes semi-analytic model to investigate how ZF-COSMOS-20115 analogues build stellar mass, and why they become quiescent. We identify three analogue galaxies with similar properties to ZF-COSMOS-20115. We find that ZF-COSMOS-20115 is likely hosted by a massive halo with virial mass of ∼1e13M⊙, having been through significant mergers at early times. These merger events drove intense growth of the nucleus, which later prevented cooling and quenched star formation. ZF-COSMOS-20115 likely remained quiescent at z < 3.7. We find that the analogues host the most massive black holes in our simulation and were luminous quasars at z ∼ 5, indicating that ZF-COSMOS-20115 and other massive quiescent galaxies may be the descendants of high redshift quasars. In addition, the model suggests that ZF-COSMOS-20115 formed in a region of intergalactic medium that was reionized early.
Key words: methods: numerical — galaxies: formation — galaxies: high-redshift