Stellar population gradient from the core to the outer region. Zhúlóng has a quiescent-like galaxy core embedded in a star-forming stellar disk. The figure shows the SED shapes and photometry as measured in different annuli, from the central core (top left) to the outer region (bottom right), as indicated by the labels. The properties of different annular regions are listed in Table 1. Note that the galaxy is very extended, with spiral arms extending more than 19 kpc in diameter.