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  The fragmenting past of the disk at the Galactic Center : The culprit for the missing red giants

Amaro-Seoane, P., & Chen, X. (2014). The fragmenting past of the disk at the Galactic Center: The culprit for the missing red giants. The Astrophysical Journal Letters, 781(1): L18.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-002A-8041-0 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-002A-8042-E
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 Creators:
Amaro-Seoane, Pau1, Author              
Chen, Xian1, Author
Affiliations:
1Astrophysical and Cosmological Relativity, AEI-Golm, MPI for Gravitational Physics, Max Planck Society, ou_1933290              

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Free keywords: Astrophysics, Cosmology and Extragalactic Astrophysics, astro-ph.CO, Astrophysics, Galaxy Astrophysics, astro-ph.GA
 Abstract: Since 1996 we have known that the Galactic Center (GC) displays a core-like distribution of red giant branch (RGB) stars starting at ~ 10", which poses a theoretical problem, because the GC should have formed a segregated cusp of old stars. This issue has been addressed invoking stellar collisions, massive black hole binaries, and infalling star clusters, which can explain it to some extent. Another observational fact, key to the work presented here, is the presence of a stellar disk at the GC. We postulate that the reason for the missing stars in the RGB is closely intertwined with the disk formation, which initially was gaseous and went through a fragmentation phase to form the stars. Using simple analytical estimates, we prove that during fragmentation the disk developed regions with densities much higher than a homogeneous gaseous disk, i.e. "clumps", which were optically thick, and hence contracted slowly. Stars in the GC interacted with them and in the case of RGB stars, the clumps were dense enough to totally remove their outer envelopes after a relatively low number of impacts. Giant stars in the horizontal branch (HB), however, have much denser envelopes. Hence, the fragmentation phase of the disk must have had a lower impact in their distribution, because it was more difficult to remove their envelopes. We predict that future deeper observations of the GC should reveal less depletion of HB stars and that the released dense cores of RGB stars will still be populating the GC.

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 Dates: 2013-10-012013-12-182014
 Publication Status: Published in print
 Pages: 5 pages, no figures, accepted for publication ApJ Letts
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 Table of Contents: -
 Rev. Method: -
 Identifiers: arXiv: 1310.0458
DOI: 10.1088/2041-8205/781/1/L18
URI: http://arxiv.org/abs/1310.0458
 Degree: -

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Title: The Astrophysical Journal Letters
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Pages: - Volume / Issue: 781 (1) Sequence Number: L18 Start / End Page: - Identifier: -