The Galactic center chimneys: The base of the multiphase outflow of the Milky Way

Abstract

Outflows and feedback are key ingredients of galaxy evolution. Evidence for an outflow arising from the Galactic center (GC) has recently been discovered at different wavelength. We show that the X-ray, radio, and infrared emissions are deeply interconnected, affecting one another and forming coherent features on scales of hundreds of parsecs, therefore indicating a common physical link associated with the GC outflow. We debate the location of the northern chimney and suggest that it might be located on the front side of the GC because of a significant tilt of the chimneys toward us. We report the presence of strong shocks at the interface between the chimneys and the interstellar medium, which are traced by radio and warm dust emission. We observe entrained molecular gas outflowing within the chimneys, revealing the multiphase nature of the outflow. In particular, the molecular outflow produces a long, strong, and structured shock along the northwestern wall of the chimney. Because of the different dynamical times of the various components of the outflow, the chimneys appear to be shaped by directed large-scale winds launched at different epochs. The data support the idea that the chimneys are embedded in an (often dominant) vertical magnetic field, which likely diverges with increasing latitude. We observe that the thermal pressure associated with the hot plasma appears to be smaller than the ram pressure of the molecular outflow and the magnetic pressure. This leaves open the possibility that either the main driver of the outflow is more powerful than the observed hot plasma, or the chimneys represent a "relic" of past and more powerful activity. These multiwavelength observations corroborate the idea that the chimneys represent the channel connecting the quasi-continuous, but intermittent, activity at the GC with the base of the Fermi bubbles.

Accepted for publication in Astronomy and Astrophysics

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Cited by in corpus (30)

• The 1.28 GHz MeerKAT Galactic Center Mosaic
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• Tracing the Milky Way's Vestigial Nuclear Jet
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• New Constraints on Cosmic Particle Populations at the Galactic Center using X-ray Observations of the Molecular Cloud Sagittarius B2
• Analyzing the Intrinsic Magnetic Field in the Galactic Center Radio Arc
• Revealing Gas Inflows towards the Galactic Central Molecular Zone
• Star Formation in Extreme Environments: A 200 pc High Velocity Gas Stream in the Galactic Centre
• Periodicity from X-ray sources within the inner Galactic disk
• CO Emission Delineating the Interface between the Milky Way Nuclear Wind Cavity and the Gaseous Disk
• Supernova-remnant origin of the Galactic-Centre filaments
• A VLA Study of Newly-Discovered Southern Latitude Non-Thermal Filaments in the Galactic Center: Radio Continuum Total-intensity and Spectral Index Properties
• Discovery of the Goat Horn complex: a $\sim 1000$ deg${}^2$ diffuse X-ray source connected to radio loop XII
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• Gas Transfer Between the Inner 3-kpc Disk and the Galactic Central Molecular Zone
• X-rays from a Central "Exhaust Vent" of the Galactic Center Chimney
• Sources and Radiations of the Fermi Bubbles
• Galactic Superbubbles in 3D: Wind Formation and Cloud Shielding
• XMM-Newton and NuSTAR discovery of a likely IP candidate XMMU J173029.8-330920 in the Galactic Disk
• Parabolic-like Trend in SiO Ratios throughout the Central Molecular Zone: Possible Signature of a Past Nuclear Activity in the Galactic Center
• SDSS-V LVM: Verifying what, and where, the 'Galactic Center' Lobe is
• How is Cold Gas Loaded into Galactic Nuclear Outflows?
• High Energy Emission from the Galactic Center
• Diffuse Hot Plasma in the Interstellar Medium and Galactic Outflows