1D profiles of ionization fraction x_HII (left), gas temperature T_k (middle), and 21 cm signal T_21 cm (right) as functions of the physical distance R from a galaxy with M_* = 10⁷ M_⊙ at z = 10.07. The colors indicate galaxies with τ_age = 0.02 Gyr (cyan), 0.1 Gyr (red), and 0.2 Gyr (yellow). The solid lines denote the results obtained by adopting the SFH from LG20 (SFH_LG20), while the dotted lines denote a constant SFR throughout the SFH (SFH_const). The surrounding IGM is assumed to be uniform with the mean density of the Universe at z = 10.07.