X-ray bubbles in the circumgalactic medium of TNG50 Milky Way- and M31-like galaxies: signposts of supermassive black hole activity

Pillepich, Annalisa; Nelson, Dylan; Truong, Nhut; Weinberger, Rainer; Martin-Navarro, Ignacio; Springel, Volker; Faber, Sandy M.; Hernquist, Lars
Bibliographical reference

Monthly Notices of the Royal Astronomical Society

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The TNG50 cosmological simulation produces X-ray emitting bubbles, shells, and cavities in the circumgalactic gas above and below the stellar discs of Milky Way- and Andromeda-like galaxies with morphological features reminiscent of the eROSITA and Fermi bubbles in the Galaxy. Two-thirds of the 198 MW/M31 analogues inspected in TNG50 at z = 0 show one or more large-scale, coherent features of overpressurized gas that impinge into the gaseous halo. Some of the galaxies include a succession of bubbles or shells of increasing size, ranging from a few to many tens of kpc. These are prominent in gas pressure, X-ray emission, and gas temperature, and often exhibit sharp boundaries with typical shock Mach numbers of 2-4. The gas in the bubbles outflows with maximum (95th pctl) radial velocities of ~100-1500 km s-1. TNG50 bubbles expand with speeds as high as 1000-2000 km s-1 (about 1-2 kpc Myr-1), but with a great diversity and with larger bubbles expanding at slower speeds. The bubble gas is at 106.4-7.2 K temperatures and is enriched to metallicities of $0.5-2~\rm Z_{\odot }$. In TNG50, the bubbles are a manifestation of episodic, kinetic, wind-like energy injections from the supermassive black holes at the galaxy centres that accrete at low Eddington ratios. According to TNG50, X-ray, and possibly γ-ray, bubbles similar to those observed in the Milky Way should be a frequent feature of disc-like galaxies prior to, or on the verge of, being quenched. They should be within the grasp of eROSITA in the local Universe.
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Traces of Galaxy Formation: Stellar populations, Dynamics and Morphology

We are a large, diverse, and very active research group aiming to provide a comprehensive picture for the formation of galaxies in the Universe. Rooted in detailed stellar population analysis, we are constantly exploring and developing new tools and ideas to understand how galaxies came to be what we now observe.

Martín Navarro