Mid-Infrared studies of dusty sources in the Galactic Center

TL;DR

This study uses 12 years of mid-infrared imaging data from ESO VLT to analyze the motions, fluxes, and physical characteristics of gas, dust, and stellar sources in the Galactic Center, revealing complex dynamics and interactions.

Contribution

It provides the first long-term proper motion measurements of dust features in the mini-spiral and identifies new kinematic behaviors and physical phenomena in the Galactic Center environment.

Findings

Proper motions of gas and dust features along the mini-spiral were measured.

Detection of Kelvin-Helmholtz instabilities in the radio tail components of IRS7.

The shape of IRS3 suggests a collision with a nuclear jet and tidal effects.

Abstract

Mid-Infrared (MIR) images of the Galactic center show extended gas and dust features along with bright IRS sources. 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 12 year time period and report their flux densities in $N$-band filters {and derive their spectral indices}. The observations were carried out by VISIR at ESO VLT. High-pass filtering led to the detection of several resolved filaments and clumps along the mini-spiral. Each source was fit by a 2-D 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 IRS7 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 the orientation of the extended late-type IRS3 star that is consistent with the ALMA sub-mm detection of the source. Its puffed-up envelope with the radius of $\sim 2\times 10^6\,R_{\odot}$ could be the result of the red-giant collision with a nuclear jet, which was followed by the tidal prolongation along the orbit.