Near- and mid-infrared observations in the inner tenth of a parsec of the Galactic center -- Detection of proper motion of a filament very close to Sgr~A*

Abstract

We analyze the gas and dust emission in the immediate vicinity of the supermassive black hole Sgr~A* at the Galactic center (GC) with the ESO VLT (Paranal/Chile) instruments SINFONI and VISIR. The SINFONI H+K data cubes show several emission lines with related line map counterparts. From these lines, the Br$\gamma$ emission is the most prominent one and appears to be shaped as a bar extending along the North-South direction. With VISIR, we find a dusty counterpart to this filamentary emission. In this work, we present evidence that this feature can be most likely connected to the mini-spiral and potentially influenced by the winds of the massive stars in the central cluster or an accretion wind from Sgr~A*. To this end, we co-add the SINFONI data between 2005 and 2015. The spectroscopic analysis reveals a range of Doppler-shifted emission lines. We also detect substructures in the shape of clumps that can be investigated in the channel maps of the Br$\gamma$-bar. In addition, we compare the detection of the near-infrared (NIR) Br$\gamma$ feature to PAH1 mid-infrared (MIR) observations and published 226 GHz radio data. These clumps show a proper motion of about $320$km/s that are consistent with other infrared continuum detected filaments in the Galactic center. Deriving a mass of $2.5\,\times\,10^{-5}\,M_{\odot}$ for the investigated Br$\gamma$-feature shows an agreement with former derived masses for similar objects. Besides the North-South Br$\gamma$-bar, we find a comparable additional East-West feature. Also, we identify several gas reservoirs that are located west of Sgr~A* that may harbor dusty objects.