UV and NIR size of the low-mass field galaxies: the UV compact galaxies
  Most of the massive star-forming galaxies are found to have `inside-out'
stellar mass growth modes, which means the inner parts of the galaxies mainly
consist of the older stellar population, while the star forming in the outskirt
of the galaxy is still ongoing. The high-resolution HST images from Hubble Deep
UV Legacy Survey (HDUV) and Cosmic Assembly Near-infrared Deep Extragalactic
Legacy Survey (CANDELS) projects with the unprecedented depth in both F275W and
F160W bands are the perfect data sets to study the forming and formed stellar
distribution directly. We selected the low redshift ($0.05 < z_{\rm spec} <
0.3$) galaxy sample from the GOODS-North field where the HST F275W and F160W
images are available. Then we measured the half light radius in F275W and F160W
bands, which are the indicators of the star formation and stellar mass. By
comparing the F275W and F160W half light radius, we find the massive galaxies
are mainly follow the `inside-out' growth which is consistent with the previous
results. Moreover, the HST F275W and F160W images reveal that some of the
low-mass galaxies ($<10^8M_\odot$) have the `outside-in' growth mode: their
images show a compact UV morphology, implying an ongoing star formation in the
galaxy centre, the stars in the outskirts of the galaxies are already formed.
The two modes transit smoothly at stellar mass range about $10^{8-9}M_\odot$
with a large scatter. We also try to identify the possible neighbour massive
galaxies from the SDSS data, which represent the massive galaxy sample. We find
that all of the spec-z selected galaxies have no massive galaxy nearby. Thus
the `outside-in' mode we find in the low-mass galaxies are not likely
originated from the environment.
