Surface brightness profile of the Milky Way’s nuclear star cluster

Context. Although the Milky Way nuclear star cluster (MWNSC) was discovered more than four decades ago, several of its key prop-erties have not been determined unambiguously up to now because of the strong and spatially highly variable interstellar extinction toward the Galactic centre. Aims. In this paper we aim at determining the shape, size, and luminosity/mass of the MWNSC. Methods. To investigate the properties of the MWNSC, we used Spitzer/IRAC images at 3.6 and 4.5 µm, where interstellar extinction is at a minimum but the overall emission is still dominated by stars. We corrected the 4.5 µm image for PAH emission with the help of the IRAC 8.0 µm map and for extinction with the help of a [3.6 − 4.5] colour map. Finally, we investigated the symmetry of the nuclear cluster and fit it with Sérsic, Moffat, and King models. Results. We present an extinction map for the central ∼ 300 × 200 pc2 of the Milky Way?, as well as a PAH-emission- and extinction-corrected image of the stellar emission, with a resolution of about 0.20 pc. We find that the MWNSC appears in projection to be intrinsically point-symmetric, that it is significantly flattened, with its major axis aligned along the Galactic plane, and that it is cen-tred on the black hole, Sagittarius A*. Its density follows the well known approximate ρ ∝ r−2-law at distances of a few parsecs from Sagittarius A*, but becomes as steep as ρ ∝ r−3 at projected radii around 5 pc. We derive a half light radius of 4.2 ± 0.4 pc, a tota