a) Chosen initial period distribution (thin solid line) and effect of the gas-induced orbital decay on period distributions of binaries embedded in an r^-2 gas density distribution with ρ_max = 10⁵   cm^-3 and a sound speed of 0.49 km s^-1 after 1   Myr (thick solid line), compared with a Gaussian fit (dotted line) to the observations by Raghavan et al. (2010). b) Same as in a), with results from the nbody6 simulations.