Missing bright red giants in the Galactic center: A fingerprint of its once active state?

Abstract

In the Galactic center nuclear star cluster, bright late-type stars exhibit a flat or even a decreasing surface-density profile, while fainter late-type stars maintain a cusp-like profile. Historically, the lack of red giants in the Galactic center was discovered via the drop in the strength of the CO absorption bandhead by Kris Sellgren et al. (1990), later followed by the stellar number counts based on the high angular resolution near-infrared observations. Several mechanisms were put forward that could have led to the preferential depletion of bright red giants: star-star collisions, tidal stripping, star-accretion disc collisions, or an infall of a massive cluster or a secondary black hole. Here we propose a novel scenario for the bright red-giant depletion based on the collisions between red giants and the nuclear jet, which was likely active in the Galactic center a few million years ago and could have led to the formation of the large-scale $\gamma$-ray Fermi bubbles. The process of the jet-induced ablation of red giants appears to be most efficient within $\sim 0.04\mathrm{pc}$ (S-cluster), while at larger distances it was complemented by star-accretion disc collisions and at smaller scales, tidal stripping operated. These three mechanisms likely operated simultaneously and created an apparent core of late-type stars within $\sim 0.5\mathrm{pc}$.

18 pages, 6 figures, 1 table; to appear in the proceedings of the online RAGtime 22 conference (organized in honour of Prof. Zdenek Stuchlik); minor additions

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• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• The Galactic Centre Chimney
• GSN 069 -- A Tidal Disruption Near-Miss
• The large-scale ionization cones in the Galaxy
• Spectroscopic Detection of a Cusp of Late-type Stars around the Central Black Hole in the Milky Way
• Evidence for a jet and outflow from Sgr A*: a continuum and spectral line study
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• Composition of the galactic center star cluster

Cited by in corpus (1)

• Mid-Infrared studies of dusty sources in the Galactic Center