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The SkyMapper-Gaia RVS view of the Gaia–Enceladus–Sausage  – an investigation of the metallicity and mass of the Milky Way’s last major merger

Feuillet, Diane LU orcid ; Feltzing, Sofia LU orcid ; Sahlholdt, Christian LU and Casagrande, Luca (2020) In Monthly Notices of the Royal Astronomical Society 497(1). p.109-124
Abstract
We characterize the Gaia–Enceladus–Sausage kinematic structure recently discovered in the Galactic halo using photometric metallicities from the SkyMapper survey, and kinematics from Gaia  radial velocities measurements. By examining the metallicity distribution functions (MDFs) of stars binned in kinematic/action spaces, we find that the JR‾‾‾√ versus Lz space allows for the cleanest selection of Gaia–Enceladus–Sausage stars with minimal contamination from disc or halo stars formed in situ or in other past mergers. Stars with 30≤JR‾‾‾√≤50 (kpc km s−1)1/2 and −500 ≤ Lz ≤ 500 kpc km s−1 have a narrow MDF centred at [Fe/H] = −1.17 dex with a dispersion of 0.34 dex. This [Fe/H] estimate is more metal-rich than literature estimates by 0.1−0.3... (More)
We characterize the Gaia–Enceladus–Sausage kinematic structure recently discovered in the Galactic halo using photometric metallicities from the SkyMapper survey, and kinematics from Gaia  radial velocities measurements. By examining the metallicity distribution functions (MDFs) of stars binned in kinematic/action spaces, we find that the JR‾‾‾√ versus Lz space allows for the cleanest selection of Gaia–Enceladus–Sausage stars with minimal contamination from disc or halo stars formed in situ or in other past mergers. Stars with 30≤JR‾‾‾√≤50 (kpc km s−1)1/2 and −500 ≤ Lz ≤ 500 kpc km s−1 have a narrow MDF centred at [Fe/H] = −1.17 dex with a dispersion of 0.34 dex. This [Fe/H] estimate is more metal-rich than literature estimates by 0.1−0.3 dex. Based on the MDFs, we find that selection of Gaia–Enceladus–Sausage stars in other kinematic/action spaces without additional population information leads to contaminated samples. The clean Gaia–Enceladus–Sausage sample selected according to our criteria is slightly retrograde and lies along the blue sequence of the high VT halo colour magnitude diagram dual sequence. Using a galaxy mass–metallicity relation derived from cosmological simulations and assuming a mean stellar age of 10 Gyr, we estimate the mass of the Gaia–Enceladus–Sausage progenitor satellite to be 108.85–9.85 M⊙, which is consistent with literature estimates based on disc dynamic and simulations. Additional information on detailed abundances and ages would be needed for a more sophisticated selection of purely Gaia–Enceladus–Sausage stars. (Less)
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author
; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Monthly Notices of the Royal Astronomical Society
volume
497
issue
1
pages
109 - 124
publisher
Oxford University Press
external identifiers
  • scopus:85095974519
ISSN
1365-2966
DOI
10.1093/mnras/staa1888
language
English
LU publication?
yes
id
1c973389-7eb1-4bde-a5ca-46855213edd7
date added to LUP
2020-08-03 16:23:23
date last changed
2024-04-17 13:42:52
@article{1c973389-7eb1-4bde-a5ca-46855213edd7,
  abstract     = {{We characterize the Gaia–Enceladus–Sausage kinematic structure recently discovered in the Galactic halo using photometric metallicities from the SkyMapper survey, and kinematics from Gaia  radial velocities measurements. By examining the metallicity distribution functions (MDFs) of stars binned in kinematic/action spaces, we find that the JR‾‾‾√ versus Lz space allows for the cleanest selection of Gaia–Enceladus–Sausage stars with minimal contamination from disc or halo stars formed in situ or in other past mergers. Stars with 30≤JR‾‾‾√≤50 (kpc km s−1)1/2 and −500 ≤ Lz ≤ 500 kpc km s−1 have a narrow MDF centred at [Fe/H] = −1.17 dex with a dispersion of 0.34 dex. This [Fe/H] estimate is more metal-rich than literature estimates by 0.1−0.3 dex. Based on the MDFs, we find that selection of Gaia–Enceladus–Sausage stars in other kinematic/action spaces without additional population information leads to contaminated samples. The clean Gaia–Enceladus–Sausage sample selected according to our criteria is slightly retrograde and lies along the blue sequence of the high VT halo colour magnitude diagram dual sequence. Using a galaxy mass–metallicity relation derived from cosmological simulations and assuming a mean stellar age of 10 Gyr, we estimate the mass of the Gaia–Enceladus–Sausage progenitor satellite to be 108.85–9.85 M⊙, which is consistent with literature estimates based on disc dynamic and simulations. Additional information on detailed abundances and ages would be needed for a more sophisticated selection of purely Gaia–Enceladus–Sausage stars.}},
  author       = {{Feuillet, Diane and Feltzing, Sofia and Sahlholdt, Christian and Casagrande, Luca}},
  issn         = {{1365-2966}},
  language     = {{eng}},
  month        = {{07}},
  number       = {{1}},
  pages        = {{109--124}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{The SkyMapper-Gaia RVS view of the Gaia–Enceladus–Sausage  – an investigation of the metallicity and mass of the Milky Way’s last major merger}},
  url          = {{http://dx.doi.org/10.1093/mnras/staa1888}},
  doi          = {{10.1093/mnras/staa1888}},
  volume       = {{497}},
  year         = {{2020}},
}