Fitting the mass–radius relation of embedded clusters in observations using N-body simulations. (a) Dashed lines are the r_h − M_ecl relations at different time nodes (t = 1 Myr, 2 Myr, 3 Myr and 4 Myr), i.e. the 1 Myr, 2 Myr, 3 Myr and 4 Myr expanding lines. Red squares and black dots represent the clusters from Carpenter et al. (1993) and Lada et al. (1991), respectively. (b) Plus symbols show the clusters from Lada & Lada (2003), while the black and red plus symbols show the clusters selected by the magnitude limits m_K<15.5 and m_K>15.5, respectively. The horizontal line marks the position of the radius r = 1 pc. (c) Distribution of the magnitude limits mK of the clusters in Lada & Lada (2003).