Near-infrared reddening of extra-galactic GMCs in a face-on geometry

Aims. We describe the near-infrared reddening signature of giant molecular clouds (GMCs) in external galaxies. In particular, we examine the EJ−H and EH−K color-excesses, and the effective extinction law observed in discrete GMC regions. We also study the effect of the relative scale height of the GMC distribution to the color-excesses, and to the observed mass function of GMCs when the masses are derived using color-excess as a linear estimator of mass. Methods. We perform Monte Carlo radiative transfer simulations with 3D models of stellar radiation and clumpy dust distributions, resembling a face-on geometry. The scattered light is included in the models, and near-infrared color maps are calculated from the simulated data. We perform the simulations with different scale heights of GMCs and compare the color-excesses and attenuation of light in different geometries. We extract GMCs from the simulated color maps and compare the mass functions to the input mass