The group acknowledges funding by the German Science Foundation's
Emmy Noether programme.
Dr. Andrea Stolte (PI)
PhD Students
Maryam Habibi
Science Aims
One of the most heavily debated, and extensively used,
universal quantities in astrophysics is the initial stellar mass function (IMF). The IMF describes the relative
numbers of high- vs. low-mass stars in any given star-forming region. Any stellar population observed today is
a direct result of the IMF during its formation and the subsequent evolutionary history of the stellar population.
In the solar neighbourhood, the IMF is surprisingly universal. Such universality is unexpected given that gaseous
and stellar densities, pre-stellar core temperatures, and magnetic fields in molecular clouds vary significantly.
One reason for this apparent similarity in the local stellar mass spectrum may originate from the similar conditions
of star-forming clouds in the solar environment. However, this environment is not characteristic for the extreme
starburst regions in external galaxies, in galactic nuclei, and in dense stellar clusters. The closest environments
where stars form under enhanced temperatures, gas densities, and possibly magnetic pressures are provided in Milky Way
starburst clusters. At the present epoch, these young, massive star clusters harbour 10,000 solar masses in stars or
more, and are formed in rare numbers in the Milky Way's spiral arms and near the center of the Galaxy.
The Emmy Noether group at the Argelander Institute for Astronomy in Bonn studies resolved starburst clusters in the Milky Way
to answer the universal question as to whether their initial stellar mass functions are similar to or deviate from the IMF
in the solar neighbourhood. The expected results provide the basis to understand the multitude of massive, unresolved
extragalactic starburst clusters, where the massive stars contribute the majority of the light, while the total mass
may be dominated by the low-mass stellar content in each cluster.
The most puzzling questions in star cluster formation
Despite several decades of young star-cluster research, some of the most basic
characteristics of young, massive star clusters are still unknown:
Survey collaboration
Emmy Noether Group, Argelander Inistut für Astronomie, University of Bonn
Science goals of the survey
With the aim to understand the environmental effects on star cluster formation,
a sample of massive star clusters has to be observed and analysed uniformly.
The Milky Way provides a small sample of six young, massive clusters securely
classified as starbursts with cluster masses in excess of 10,000 solar masses.
In this sample,
the Arches and Quintuplet clusters located near the center of the Milky Way
span ages of 2.5 to 4.5 Myr, and the two spiral arm clusters NGC 3603 and Westerlund 1
cover ages of 2 to 4 Myr. Due to their similar age ranges, these four clusters are ideally
suited to probe the differences in cluster evolution between spiral arms and the
Galactic center star-forming environment.
Methods