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A Deep View into the Nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. II. Kinematic Characterization of the Stellar Populations

Alfaro-Cuello, M. ; Kacharov, N. ; Neumayer, N. ; Bianchini, P. ; Mastrobuono-Battisti, A. LU ; Lützgendorf, N. ; Seth, A. C. ; Böker, T. ; Kamann, S. and Leaman, R. , et al. (2020) In Astrophysical Journal 892(1).
Abstract

The Sagittarius dwarf spheroidal galaxy is in an advanced stage of disruption but still hosts its nuclear star cluster (NSC), M54, at its center. In this paper, we present a detailed kinematic characterization of the three stellar populations present in M54: Young metal-rich (YMR); intermediate-age metal-rich (IMR); and old metal-poor (OMP), based on the spectra of 6500 individual M54 member stars extracted from a large Multi-Unit Spectroscopic Explorer (MUSE)/Very Large Telescope data set. We find that the OMP population is slightly flattened with a low amount of rotation (0.8 km s-1) and with a velocity dispersion that follows a Plummer profile. The YMR population displays a high amount of rotation (5 km s-1) and... (More)

The Sagittarius dwarf spheroidal galaxy is in an advanced stage of disruption but still hosts its nuclear star cluster (NSC), M54, at its center. In this paper, we present a detailed kinematic characterization of the three stellar populations present in M54: Young metal-rich (YMR); intermediate-age metal-rich (IMR); and old metal-poor (OMP), based on the spectra of 6500 individual M54 member stars extracted from a large Multi-Unit Spectroscopic Explorer (MUSE)/Very Large Telescope data set. We find that the OMP population is slightly flattened with a low amount of rotation (0.8 km s-1) and with a velocity dispersion that follows a Plummer profile. The YMR population displays a high amount of rotation (5 km s-1) and a high degree of flattening, with a lower and flat velocity dispersion profile. The IMR population shows a high but flat velocity dispersion profile, with some degree of rotation (2 km s-1). We complement our MUSE data with information from Gaia DR2 and confirm that the stars from the OMP and YMR populations are comoving in 3D space, suggesting that they are dynamically bound. While dynamical evolutionary effects (e.g., energy equipartition) are able to explain the differences in velocity dispersion between the stellar populations, the strong differences in rotation indicate different formation paths for the populations, as supported by an N-body simulation tailored to emulate the YMR-OMP system. This study provides additional evidence for the M54 formation scenario proposed in our previous work, where this NSC formed via GC accretion (OMP) and in situ formation from gas accretion in a rotationally supported disk (YMR).

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Contribution to journal
publication status
published
subject
in
Astrophysical Journal
volume
892
issue
1
article number
20
publisher
American Astronomical Society
external identifiers
  • scopus:85085121065
ISSN
0004-637X
DOI
10.3847/1538-4357/ab77bb
language
English
LU publication?
yes
id
820f1afd-f98d-4320-b14e-fe898f9bec5c
date added to LUP
2020-06-24 16:31:28
date last changed
2022-12-23 23:06:24
@article{820f1afd-f98d-4320-b14e-fe898f9bec5c,
  abstract     = {{<p>The Sagittarius dwarf spheroidal galaxy is in an advanced stage of disruption but still hosts its nuclear star cluster (NSC), M54, at its center. In this paper, we present a detailed kinematic characterization of the three stellar populations present in M54: Young metal-rich (YMR); intermediate-age metal-rich (IMR); and old metal-poor (OMP), based on the spectra of 6500 individual M54 member stars extracted from a large Multi-Unit Spectroscopic Explorer (MUSE)/Very Large Telescope data set. We find that the OMP population is slightly flattened with a low amount of rotation (0.8 km s<sup>-1</sup>) and with a velocity dispersion that follows a Plummer profile. The YMR population displays a high amount of rotation (5 km s<sup>-1</sup>) and a high degree of flattening, with a lower and flat velocity dispersion profile. The IMR population shows a high but flat velocity dispersion profile, with some degree of rotation (2 km s<sup>-1</sup>). We complement our MUSE data with information from Gaia DR2 and confirm that the stars from the OMP and YMR populations are comoving in 3D space, suggesting that they are dynamically bound. While dynamical evolutionary effects (e.g., energy equipartition) are able to explain the differences in velocity dispersion between the stellar populations, the strong differences in rotation indicate different formation paths for the populations, as supported by an N-body simulation tailored to emulate the YMR-OMP system. This study provides additional evidence for the M54 formation scenario proposed in our previous work, where this NSC formed via GC accretion (OMP) and in situ formation from gas accretion in a rotationally supported disk (YMR).</p>}},
  author       = {{Alfaro-Cuello, M. and Kacharov, N. and Neumayer, N. and Bianchini, P. and Mastrobuono-Battisti, A. and Lützgendorf, N. and Seth, A. C. and Böker, T. and Kamann, S. and Leaman, R. and Watkins, L. L. and Van De Ven, G.}},
  issn         = {{0004-637X}},
  language     = {{eng}},
  month        = {{03}},
  number       = {{1}},
  publisher    = {{American Astronomical Society}},
  series       = {{Astrophysical Journal}},
  title        = {{A Deep View into the Nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. II. Kinematic Characterization of the Stellar Populations}},
  url          = {{http://dx.doi.org/10.3847/1538-4357/ab77bb}},
  doi          = {{10.3847/1538-4357/ab77bb}},
  volume       = {{892}},
  year         = {{2020}},
}