Related papers: Massive Star Feedback on the IMF
Recent studies of the substellar population in the Taurus cloud have revealed a deficit of brown dwarfs (BD) compared to the Trapezium cluster population (Briceno et al 1998; Luhman 2000; Luhman et al 2003a; Luhman 2004). However, these…
The observed distribution of IMF shapes can be understood as statistical sampling from a universal IMF and variations that result from stellar-dynamical processes. However, young star clusters appear to have an IMF biased towards low-mass…
Recent observations show a strong correlation between stellar mass and accretion rate in young stellar and sub-stellar objects, with the scaling $\dot{M}_{acc} \propto M_*^2$ holding over more than four orders of magnitude in accretion…
We present the results of numerical experiments designed to evaluate the usefulness of near-infrared luminosity functions for constraining the Initial Mass Function (IMF) of young stellar populations. From this numerical modeling, we find…
We present a large suite of simulations of the formation of low-mass star clusters. Our simulations include an extensive set of physical processes -- magnetohydrodynamics, radiative transfer, and protostellar outflows -- and span a wide…
The stellar initial mass function (IMF) in the early universe is essential to understand the formation of ancient galaxies. To this end, we conduct a series of long-term radiation hydrodynamic simulations following star cluster formation,…
We describe the results of a very deep imaging survey of the Trapezium Cluster in the IJH bands, using the UKIRT high resolution camera UFTI. Approximately 32% of the 515 point sources detected are brown dwarf candidates, including several…
I have performed a search for young low-mass stars and brown dwarfs (BDs) in 2 regions encompassing a total area of 4 deg^2 in the Taurus star-forming region, discovering 15 new members of Taurus. In addition, I present 7 new members…
We exploit the ability of the Hubble Space Telescope to probe near infrared water absorption present in the atmosphere of low-mass stars, brown dwarfs and planetary mass objects to create a very pure sample of Orion Nebula Cluster (ONC)…
Here I discuss recent work on brown dwarfs, massive stars and the IMF in general. The stellar IMF can be well described by an invariant two-part power law in present-day star-formation events within the Local Group of galaxies. It is nearly…
Understanding the origin of high-mass stars is central to modern astrophysics. We shed light on this problem with simulations using a novel, adaptive-mesh, ray-tracing algorithm. These simulations consistently follow the gravitational…
Observations of mergers of multi-compact object systems offer insights to the formation processes of massive stars in globular clusters. Simulations of stellar clusters, may be used to understand and interpret observations. Simulations…
The current knowledge on the stellar IMF is documented. It appears to become top-heavy when the star-formation rate density surpasses about 0.1Msun/(yr pc^3) on a pc scale and it may become increasingly bottom-heavy with increasing…
We investigate how different stellar initial mass functions (IMFs) can affect the mass loss and survival of star clusters. We find that IMFs with radically different low-mass cut-offs (between 0.1 and 2 Msun) do not change cluster…
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…
Theoretical considerations lead to the expectation that stars should not have masses larger than about m_{max*}=60-120Msun, while the observational evidence has been ambiguous. Only very recently has a physical stellar mass limit near…
The ONC appears to be unusual on two grounds: The observed constellation of the OB stars of the entire Orion Nebula cluster and its Trapezium at its centre implies a time-scale problem given the age of the Trapezium, and an IMF problem for…
It has been shown before that the high mass-to-light ratios of ultra compact dwarf galaxies (UCDs) can be explained if their stellar initial mass function (IMF) was top-heavy, i.e. that the IMF was skewed towards high mass stars. In this…
We present results from Tree+SPH simulations of a galaxy cluster, aimed at studying the metal enrichment of the intra--cluster medium (ICM). The simulation code includes a fairly advanced treatment of star formation, as well as the release…
When star clusters are formed at low star-formation rates (SFRs), their stellar initial mass function (IMF) can hardly be filled continuously with stars at each mass. This lack holds for massive stars and is observationally verified by the…