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 Very Large Telescope (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 Brγ 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 could most be likely connected to the minispiral 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 coadd 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 Brγ bar. In addition, we compare the detection of the near-infrared Brγ feature to PAH1 mid-infrared observations and published 226 GHz radio data. These clumps show a proper motion of about 320 km s−1 that are consistent with other infrared continuum–detected filaments in the GC. Deriving a mass of for the investigated Brγ feature shows an agreement with former derived masses for similar objects. Besides the north–south Brγ 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.

Mid-infrared (MIR) images of the Galactic center show extended gas and dust features along with bright infrared sources (IRS). Some of these dust features are a part of ionized clumpy streamers orbiting Sgr A*, known as the mini-spiral. We present their proper motions over a 12 yr time period and report their flux densities in N-band filters and derive their spectral indices. The observations were carried out by VISIR at the ESO’s Very Large Telescope. High-pass filtering led to the detection of several resolved filaments and clumps along the mini-spiral. Each source was fit by a 2D Gaussian profile to determine the offsets and aperture sizes. We perform aperture photometry to extract fluxes in two different bands. We present the proper motions of the largest consistent set of resolved and reliably determined sources. In addition to stellar orbital motions, we identify a stream-like motion of extended clumps along the mini-spiral. We also detect MIR counterparts of the radio tail components of the IRS 7 source. They show a clear kinematical deviation with respect to the star. They likely represent Kelvin–Helmholtz instabilities formed downstream in the shocked stellar wind. We also analyze the shape and orientation of the extended late-type IRS 3 star that is consistent with the Atacama Large Millimeter/submillimeter Array submillimeter detection of the source. Its puffed-up envelope with a radius of ∼2 × 106 R ⊙ could be the result of the red-giant collision with a nuclear jet, which was followed by tidal prolongation along the orbit.

Abstract The EUV provides most of the ionization that creates the high equivalent width (EW) broad and narrow emission lines (BELs, NELs) of quasars. Spectra of Hypermassive Schwarzschild black holes (HMBHs, MBH ≥ 1010M⊙) with α-discs, decline rapidly in the EUV suggesting much lower EWs. Model spectra for black holes of mass 106 − 1012M⊙ and accretion rates 0.03 ≤ Lbol/Ledd ≤ 1.0 were input to the CLOUDY photoionization code. BELs become ∼100 times weaker in EW from MBH ∼ 108M⊙ to MBH ∼ 1010M⊙. The high ionization BELs (O VI 1034 Å, C IV 1549 Å, He II 1640 Å) decline in EW from (MBH ≥ 106M⊙, reproducing the Baldwin effect, but regain EW for MBH ≥ 1010M⊙). The low ionization lines (MgII 2798 Å, Hβ 4861 Å and Hα 6563 Å) remain weak. Lines for maximally spinning HMBHs behave similarly. Line ratio diagrams for the BELs show that high OVI/Hβ and low CIV/Hα may pick out HMBH, although OVI is often hard to observe. In NEL BPT diagrams HMBHs lie among star forming regions, except for highly spinning, high accretion rate HMBHs. In summary, the BELs expected from HMBHs would be hard to detect using the current optical facilities. From 100 to 1012M⊙, the emission lines used to detect AGN only have high EW in the 106 − 109M⊙ window, where most AGN are found. This selection effect may be distorting reported distributions of MBH.