Massive galaxies and EROs at z=1-3 in cosmological hydrodynamic
simulations: Is the hierarchical CDM model wrong?
Ken Nagamine (UC San Diego)
Recently there have been several claims that the hierarchical cold dark
matter (CDM) model might have a difficulty in producing massive galaxies
that have been found at redshift z=1-2 by near-IR observations. In order
to test these claims, we study the properties of massive galaxies at
z=1-3 in two different types of cosmological hydrodynamic simulations.
In particular, I focus on colors, stellar masses, and star formation
histories of galaxies, and describe how the hydrodynamic simulations
achieve the production of 10^11 Msun galaxies by z=2. Unlike the current
semi-analytic models of galaxy formation, our models predict the peak of
the Madau plot to be at z>=5 and higher stellar mass density at z>1 than
the current observational estimates. Our models suggest that the current
observations could be missing as much as 50% of the stellar masses at
high redshift. We also study the number density of Extremely Red Objects
(EROs), and find that our simulations can account for the observed space density
of EROs at z=1-2 if a uniform extinction of E(B-V)=0.4 is assumed.
However, it still remains to be seen whether the simulations can produce
enough 'dead massive EROs'.