PhD Project: Starburst clusters near the center of the Galaxy
Argelander Institut für Astronomie, University of Bonn

PhD candidate: Maryam Habibi
 
 
Young, massive star clusters - or starburst clusters - are among the most extreme star forming environments in the Milky Way galaxy today. Due to the large distances to these objects their global properties are not well known. This is particularly true for the starburst clusters evolving near the center of the Galaxy, where the field population hampers the detection of lower-mass cluster members. The tidal field in the inner Galaxy disrupts central clusters on timescales of 10-20 Myr, leaving only a small time window to study these unusual objects.
 
Within the framework of the thesis, the VLT adaptive optics system NAOS/CONICA is emploid to obtain proper motion membership of stars in the Galactic center Arches cluster. The astrometric precision achieveable with ground-based diffraction-limmited imaging, and the large relative motion of the cluster with respect to the field, provides the unique opportunity to identify cluster stars on a star-by-star basis. Overcoming the most severe limitations in our understanding of central starburst clusters will lead to the characterisation of the true cluster extent, the lower-mass population, and the initial stellar mass function outside the immediate cluster core.
 
Scientific goals:
 
  1. • Derivation of the local extinction map towards the Arches cluster
  2. • Definition of cluster extent and radial profile
  3. • Extended stellar mass distribution
  4. • Constraints on the cluster orbit and tidal disruption in the Galactic center field
  5. • Comparison of tidal structure with existing N-body simulations
 
The project encompasses the analysis of spectroscopic and multi-epoch near infrared imaging data obtained with adaptive optics at large optical telescopes (e.g., VLT NACO, FORS, and SINFONI observations). Spectral types, luminosities and kinematic properties of individual cluster members will be determined, from which the dynamical state and the stellar mass distribution of starburst clusters will be derived. Special emphasis is placed on star clusters undergoing disruption in the strong gravitational field near the center of the Galaxy. Scientific aims include the in-depth understanding of the dynamical evolution of star clusters forming under extreme conditions and the search for tidal debris.
 
 
Specific analysis tools include:
 
  1. • data reduction and analysis of adaptive optics imaging and spectroscopy observations
  2. • selection of a clean sample of cluster stars:
     astrometric determination of proper motion membership
  1. •  derivation of the stellar mass distribution from isochrone fitting
  2. • definition of cluster life cycle in the GC from orbit simulations
  3. • comparison to existing N-body models of the Arches cluster