Destruction of protoplanetary discs in the Orion Nebula Cluster

Abstract

We use numerical N-body simulations of the Orion Nebula Cluster (ONC) to\ninvestigate the destruction of protoplanetary disks by close stellar encounters\nand UV radiation from massive stars. The simulations model a cluster of 4000\nstars, and we consider separately cases in which the disks have fixed radii of\n100 AU and 10 AU. In the former case, depending on a star's position and orbit\nin the cluster over 10^7 years, UV photoevaporation removes at least 0.01 Msol\nfrom its disk, and can remove up to 1 Msol. We find no dynamical models of the\nONC consistent with the suggestion of Storzer and Hollenbach that the observed\ndistribution and abundance of proplyds could be explained by a population of\nstars on radial orbits which spend relatively little time near Theta 1C Ori\n(the most massive star in the ONC). Instead the observations require either\nmassive disks (e.g. a typical initial disk mass of 0.4 Msol) or a very recent\nbirth for Theta 1C Ori. When we consider the photoevaporation of the inner 10\nAU of disks in the ONC, we find that planet formation would be hardly affected.\nOutside that region, planets would be prevented from forming in about half the\nsystems, unless either the initial disk masses were very high or they formed in\nless than ~ 2 Myr and Theta 1C Ori has only very recently appeared. We also\npresent statistics on the distribution of minimum stellar encounter\nseparations. This peaks at 1000 AU, with less than 10% of stars having had an\nencounter closer than 100 AU after 10^7 years. We conclude that stellar\nencounters are unlikely to play a significant role in destroying protoplanetary\ndisks. In the absence of any disruption mechanism other than those considered\nhere, we would thus predict planetary systems like our own to be common amongst\nstars forming in ONC-like environments.\n