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The distribution of stars around the Milky Way's central black hole II: Diffuse light from sub-giants and dwarfs

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Amaro-Seoane,  Pau
Astrophysical and Cosmological Relativity, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;

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1701.03817.pdf
(Preprint), 8MB

aa30452-17.pdf
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Citation

Schödel, R., Gallego-Cano, E., Dong, H., Nogueras-Lara, F., Gallego-Calvente, A. T., Amaro-Seoane, P., et al. (2018). The distribution of stars around the Milky Way's central black hole II: Diffuse light from sub-giants and dwarfs. Astronomy and Astrophysics, 609: A27. doi:10.1051/0004-6361/201730452.


Cite as: http://hdl.handle.net/21.11116/0000-0004-3A77-6
Abstract
This is the second of three papers that search for the predicted stellar cusp around the Milky Way's central black hole, Sagittarius A*, with new data and methods. We aim to infer the distribution of the faintest stellar population currently accessible through observations around Sagittarius A*. We use adaptive optics assisted high angular resolution images obtained with the NACO instrument at the ESO VLT. Through optimised PSF fitting we remove the light from all detected stars above a given magnitude limit. Subsequently we analyse the remaining, diffuse light density. The analysed diffuse light arises from sub-giant and main-sequence stars with KS ~ 19 - 20 with masses of 1 - 2 Msol . These stars can be old enough to be dynamically relaxed. The observed power-law profile and its slope are consistent with the existence of a relaxed stellar cusp around the Milky Way's central black hole. We find that a Nuker law provides an adequate description of the nuclear cluster's intrinsic shape (assuming spherical symmetry). The 3D power-law slope near Sgr A* is \gamma = 1.23 +- 0.05. At a distance of 0.01 pc from the black hole, we estimate a stellar mass density of 2.3 +- 0.3 x 10^7 Msol pc^-3 and a total enclosed stellar mass of 180 +- 20 Msol. These estimates assume a constant mass-to-light ratio and do not take stellar remnants into account. The fact that no cusp is observed for bright (Ks 16) giant stars at projected distances of roughly 0.1-0.3 pc implies that some mechanism has altered their appearance or distribution.