Using state-of-the-art adaptive mesh refinement cosmological hydrodynamic simulations with a spatial resolution of 0.15 h-1kpc on a cosmological volume (20 h-1Mpc), we investigate the sizes of galaxies at z=3 in the standard cold dark matter model where re

8

2

y

a

M

2

]h

p

-

o

r

t

s

a

[

2

v

5

1

3

.

5

8

:0v

i

X

r

aGalaxySizeProblematz=3:SimulatedGalaxiesAreTooSmallM.RyanJoung1,RenyueCen1,&GregL.Bryan2Received