The centre of the Milky Way is the nearest nucleus of a galaxy. It is therefore a unique laboratory for studying massive black holes and nuclear star clusters, and for investigating astrophysical processes in extreme environments. The Galactic centre has been my main field of research since over 15 years. As part of my PhD thesis I participated directly in the discovery of the first stellar orbits around Sagittarius A*, the Milky Way´s central, supermassive black hole. This work is still ranked first in the list of the ESO Top 10 Astronomical Discoveries (Schödel et al. 2002; Schödel et al. 2003). Via my collaboration with the UCLA Galactic Center Group, I am still closely involved in the study of stellar orbits around Sagittarius A* (see: Meyer et al. 2012; Boehle et al. 2016). I have studied the variable, polarised emission from the accretion flow or outflow around Sagittarius A* and have played a key role in several international coordinated multi-wavelength campaigns (e.g., Genzel et al. 2003; Eckart et al. 2006; Schoedel et al. 2011). Starting out from studying the immediate environment of Sagittarius A*, I have moved on to characterising the stellar population and its dynamics in the central parsec of the Milky Way (Schödel et al. 2007; Schödel et al. 2009), and am now dedicated to characterising the structure, stellar population and formation history of the nuclear star cluster, a ~25 million solar mass cluster with complex star formation history that dominates the inner 10 pc of the Milky Way (Schödel et al. 2014a), and of the nuclear stellar disc, a dense stellar disk-like structure that marks the Galactic centre proper and stretches out to distances of about 200 pc from the central black hole. I consider my most fundamental contributions to the field the discovery and study of stellar orbits around the supermassive black hole, the characterisation of the nuclear star cluster, in particular its size, mass and shape, and my group’s recent confirmation of the existence of the predicted stellar cusp around Sagittarius A*.
High resolution imaging
Interferometry, adaptive optics (AO), speckle/lucky imaging, and sparse aperture masking, as well as the related image reconstruction and analysis techniques are key methodologies for my research. In particular, I have presented an effective method to extract instantaneous point spread functions (PSFs) from short exposures of crowded fields. This allows us to apply the so-called speckle holography algorithm to obtain images at the maximum possible angular resolution with a large suite of existing instruments. This methodology is the basis of our GALACTICNUCLEUS project (Schödel et al. 2012; Schödel et al. 2013) and is explained in more detail in the Project section.
Massive stars play a central role in astrophysics due to their impact on chemical evolution, star formation, or ISM dynamics. Yet, because they are rare and short-lived, they are still poorly understood. Together with my colleagues Antxón Alberdi (IAA-CSIC, Spain) and Joel Sánchez-Bermúdez (MPIA, Germany), I am involved in interferometric studies of massive stars with the ESO’s VLT Interferometer.
Infrared observations of stellar populations
Work on the Galactic Centre, on massive stars, and with high angular resolution near-infrared imaging has led me naturally to be involved in near-infrared studies of stellar populations in star clusters. With my colleague Koraljka Muzic from the University of Lisbon I am involved in studying Brown Dwarfs in dense stellar clusters.
Massive black holes and nuclear star clusters
The black hole and nuclear star cluster at the center of the Milky Way are a close up, unique laboratory. Massive black holes and nuclear star clusters in the nearby Universe provide the necessary context for Galactic centre research. I am the leading of a review on the Galactic centre in this context (Schödel et al. 2014b) and have co-organised several workshops on this topic.