First, the luminosity functions of young ... cluster systems are remarkably similar to the mass functions of GMCs in present-day spiral galaxies (Harris & Pudritz 1994).

Second, ... the radial distribution of the young ... clusters follows closely the remnant's visual light distribution. This indicates that the progenitors of the young [massive] clusters experienced the same violent relaxation as did the disk stars (Schweizer et al. 1996). This in turn suggests that these progenitors reacted to the merger like point masses and were quite compact. The GMCs of the input galaxies fit the bill, while the more diffuse interstellar gas presumably experienced significant dissipation and piled up near the center of the remnant, redistributing itself differently from the stars.