摘要：Context. The size of a galaxy encapsulates the signature of the
different physical processes driving its evolution. The distribution of galaxy sizes in
the Universe as a function of cosmic time is therefore a key to understand galaxy
evolution.
Aims. We aim to measure the average sizes and size distributions of
galaxies as they are assembling before the peak in the comoving star formation rate
density of the Universe to better understand the evolution of galaxies across cosmic
time.
Methods. We used a sample of ~1200 galaxies in the COSMOS and ECDFS fields with confirmed
spectroscopic redshifts 2 ≤
zspec ≤ 4.5 in the VIMOS Ultra Deep
Survey (VUDS), representative of star-forming galaxies with iAB ≤ 25. We
first derived galaxy sizes by applying a classical parametric profile-fitting method using
GALFIT. We then measured the total pixel area covered by a galaxy above a given surface
brightness threshold, which overcomes the difficulty of measuring sizes of galaxies with
irregular shapes. We then compared the results obtained for the equivalent circularized
radius enclosing 100% of the measured galaxy light r100T ~2.2 to those obtained with the effective radius
re,circ measured with GALFIT.
Results. We find that the sizes of galaxies computed with our
non-parametric approach span a wide range but remain roughly constant on average with a
median value r100T ~2.2 kpc for galaxies with 2
