Face-on projections of the stacked surface density distributions of stars and gas in the X-Y plane within a 15 × 15 kpc² box at 2.5 Gyr for the models r1c14b00, r1c14b05, and r1c14b10 (from left to right). The yellowish-brown colors represent the stellar distribution, while the dark regions indicate the gas distribution. The overlaid blue and purple points mark young stars with ages 0.01 < t_age < 0.1 Gyr and t_age ≤ 0.01 Gyr, respectively. The same projections at 1, 2, 3, 4, and 5 Gyr are shown in Fig. 4. The separate surface density distributions of stars and gas are presented in Fig. A.3.