Research Interests

I am interested in the study of Galactic Nuclei because it can teach us about galaxy evolution, star formation in the most extreme environments, and the relation between stellar nuclei, MBHs, and host galaxies.

The biggest obstacle for studying Galactic Nuclei is their great distance, which limits us to the study of the integrated light, averaged over scales of several parsecs to tens of parsecs and dominated by the brightest stars.

For this reason, I study the centre of the Milky Way, because it is close to Earth (located at only 8 kpc from us). Because of its proximity, it is the only galaxy nucleus in which we can actually resolve the stellar population observationally and examine its properties and dynamics on scales of milli-parsecs. Moreover, we can explore the radius of the influence of the central black hole in detail. It is thus a crucial laboratory for studying galactic nuclei and NSCs.

I use high angular resolution near-infrared imaging data from the WFC3 camera at the Hubble Space Telescope and from the NACO instrument at the VLT. Now, I am working on the following:
 L-band image of the Galactic Center central parsec obtained with NACO instrument at the VLT-ESO telescopes. Credit: Schödel, R.

  • Stellar cusp: Theoretical stellar dynamics predicts the existence of a stellar cusp around the central black hole of the Milky Way. However, current observations indicate the absence of such a cusp. This contradiction may pose a severe problem to our understanding of stellar dynamics. My work aims at pushing the analysis of the structure of the NSC to fainter stars than what was examined before. Can we confirm the absence of a stellar cusp?

     

  • Star formation and formation history of the NSC: Nuclear star clusters can be found in the majority of galaxies, both late and early types. Ks-band image of the Galactic Center (Gallego-Cano et al, 2017). The Ks-band image was obtained on 11th May 2011 with NACO instrument at the VLT and covers the central 1.5’ x 1.5’ of the GC.NSCs show typically sigs of complex stellar populations, with quasi-continuous star formation. Frequently, they show signs of star formation episoades having occurred less than 100 Myr ago. Although some models for the star formation history of the Milky Way’s NSC exist, they are based on spectroscopic data of a few hundred stars within about 1 pc of the black hole. I would like to provide new, different constraints from analysing near-infrared multi-wavelength imaging and fitting stellar population models to the resulting colour-magnitude diagrams and luminosity functions. In particular, I wonder how important is the population of intermediate age stars, that formed between a few 10 Myr and a few 100 Myr ago?

     

     

     

  • Collaboration with Galactic Center Group at UCLA: I am working on NIRC/Keck Speckle data obtained between 1995 and 2005. The data have been key to determining the orbits of stars around the Super Massive Black Hole, SgA*. Thanks to holographic data reduction, the data were succeeded used. Now we want to improve the exploitation of these old data again. We are concerned with optimising image quality, minimising edge effects, reducing systematic errors, and optimising error estimation.

Simulation of gas cloud after close approach to the black hole at the centre of the Milky Way:  This view shows a simulation of how a gas cloud that has been observed approaching the supermassive black hole at the centre of the galaxy may break apart over the next few years. This is the first time ever that the approach of such a doomed cloud to a supermassive black hole has been observed and it is expected to break up completely during 2013. The remains of the gas cloud are shown in red and yellow, with the cloud's orbit marked in red. The stars orbiting the black hole are also shown along with blue lines marking their orbits. This view simulates the expected positions of the stars and gas cloud in the year 2021.Credit: ESO/MPE/Marc Schartmann