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Mathematisch-Naturwissenschaftliche FakultätAstrophysik I.Physik

Warm Dust and IR-excess sources

In direct vicinity of Sgr A*, the super massive black hole in the center of our galaxy, is populated by many young O and B stars. After the first infrared observations of the Galactic center, that were able to resolve stars in the central parsec, these spectroscopic results are still unexpected. Mainly because the harsh environment of a super massive black hole hinders star formation. However, recent findings keep surprising the scientfic community. For example, an object is found in 2011 and it was believed, that this source is a gas cloud moving towards Sgr A* with high velocities up to 3000 km/s (1% of the speed of light).

In the last 6 years, we traced this object, that we call Dusty S-cluster Object (DSO) not only in the L' band but also in the K-band. For that, we used mainly SINFONI and NACO mounted at the Very Large Telescope in Chile. By combining observational data and theoretical models, we showed, that the DSO is rather a pre-main sequence star embedded in a dusty envelope that stays on a Keplerian orbit around Sgr A* especially after the peri-center passage in 2014. The K- and L'-band magnitudes show clear signitures of a class I Young Stellar Object (YSO). The combination of scattered dust emission with a stellar component can also be observed in other dusty objects around Sgr A*. The D2 and D3 sources, that are much slower compared to the DSO by a factor of 10, share the same photometric footprint. The measured flux and magnitudes can be also reproduced by a Spectral Energy Distribution (SED) that is used for the DSO.

By searching for other objects, we found a new bowshock source with bipolar morphology that we call X8 to underline similarities with the already know bowshock source X7. It is most likely the closest bipolar outflow source known to date. These bipolar features are found in YSOs which makes X8 another candidate that can be added to the community known phrase "Paradox of youth". Another interesting fact is found in the spectrum of X8. Like D2, D3, and X7 it shows ionized blue-shifted [Fe III] lines that are produced by high energies. It can be speculated, that a possible wind coming from Sgr A* is responsible for the ionization. 

Selected Publications