Context. 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. Aims. 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. Methods. We selected the low redshift (0.05 < z 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. Results. By comparing the F275W and F160W half light radius, we find the massive galaxies are mainly follow the 'inside-out' growth mode, which is consistent with the previous results. Moreover, the HST F275W and F160W images reveal that some of the low-mass galaxies (< 10 8 M ⊙ ) have the 'outside-in' growth mode: their images show a compact UV morphology, implying an ongoing star formation in the galaxy centre, while 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 ⊙ 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.

Using the 0.9–4.4 μm imaging data from the James Webb Space Telescope (JWST) early release observation in the SMACS J0723.3–7327 galaxy cluster field, we discuss the properties of three submillimeter galaxies (SMGs) detected by the Atacama Large Millimeter/submillimeter Array Array. These sources are magnified by 1.4–2.1 × due to gravitational lensing. This is the first time that submillimeter galaxy hosts are resolved in the rest-frame near-infrared (NIR). One source was previously undetected by Hubble Space Telescope, while the remaining two are disk galaxies with Sérsic indices of ∼0.9 and star formation rates on or just below the star formation “main sequence.” Their submillimeter emission originates from the inner parts of the hosts, suggesting that their dust contents are concentrated toward the center. The host half-light radii measured in the rest-frame NIR are ∼1.5 × smaller than those measured in the rest-frame optical, consistent with a concentrated dust distribution. The more severe extinction that optical light suffers toward the center makes it seemingly less concentrated. Therefore, we expect that the optically based determination of the stellar mass distribution within host galaxies could still be severely biased by dust. Interestingly, these two disk galaxies are dramatically different in their outer regions, with one being star forming and the other being quiescent. Upcoming JWST observations of statistically significant samples of SMGs will allow us to understand the correlation between the dusty star-forming regions and their hosts.

Historically, GHz radio emission has been used extensively to characterize the star-formation activity in galaxies. In this work, we look for empirical relationships amongst the radio luminosity, the infrared luminosity, and the CO-based molecular gas mass. We assemble a sample of 278 nearby galaxies with measurements of radio continuum and total infrared emission, and the 12CO J = 1–0 emission line. We find a correlation between the radio continuum and the CO emission line (with a scatter of 0.36 dex), in a large sample of different kinds of galaxies. Making use of this correlation, we explore the evolution of the molecular gas mass function and the cosmological molecular gas mass density in six redshift bins up to z = 1.5. These results agree with previous semi-analytic predictions and direct measurements: the cosmic molecular gas density increases up to z = 1.5. In addition, we find a single plane across five orders of magnitude for the explored luminosities, with a scatter of 0.27 dex. These correlations are sufficiently robust to be used for samples where no CO measurements exist.