Top-heavy IMFs in ultra compact dwarf galaxies?
Abstract
Ultra compact dwarf galaxies (UCDs) are dense stellar systems at the border between massive star-clusters and small galaxies. Their on average high optical mass-to-light (M/L) ratio cannot be explained by stellar populations with the canonical stellar initial mass function (IMF), while it is doubtful that non-baryonic dark matter can accumulate enough on the scales of UCDs for influencing their dynamics significantly. UCDs in the Virgo galaxy cluster apparently also have an over-abundance of neutron stars, strongly suggesting a top-heavy IMF, which would explain both findings. This is because a top-heavy IMF can provide the unseen mass through an abundance of stellar remnants. The suggested variation of the IMF can be understood if UCDs represent a case of rapid star-formation in an extremely dense environment. While top-heavy IMFs imply a much heavier mass-loss shortly after the formation of a stellar system, this process does not necessarily dissolve the UCDs. Their formation with a top-heavy IMF would therefore not contradict their existence.
Keywords
Cite
@article{arxiv.1201.3912,
title = {Top-heavy IMFs in ultra compact dwarf galaxies?},
author = {Jörg Dabringhausen and Pavel Kroupa},
journal= {arXiv preprint arXiv:1201.3912},
year = {2012}
}
Comments
Proceedings to the conference "UP: Have Observations Revealed a Variable Upper End of the Initial Mass Funktion?" that was held in Sedona, Arizona, in 2010. The subject of this article is discussed in greater detail in our recent paper "Low-mass X-ray binaries indicate a top-heavy IMF in ultra compact dwarf galaxies", arXiv:1110.2779