TY - JOUR
T1 - GHOST Commissioning Science Results II
T2 - a very metal-poor star witnessing the early Galactic assembly
AU - Sestito, Federico
AU - Hayes, Christian R.
AU - Venn, Kim A.
AU - Jensen, Jaclyn
AU - McConnachie, Alan W.
AU - Pazder, John
AU - Waller, Fletcher
AU - Arentsen, Anke
AU - Jablonka, Pascale
AU - Martin, Nicolas F.
AU - Matsuno, Tadafumi
AU - Navarro, Julio F.
AU - Starkenburg, Else
AU - Vitali, Sara
AU - Bassett, John
AU - Berg, Trystyn A. M.
AU - Diaz, Ruben
AU - Edgar, Michael L.
AU - Firpo, Veronica
AU - Gomez-Jimenez, Manuel
AU - Kalari, Venu
AU - Lambert, Sam
AU - Lawrence, Jon
AU - Robertson, Gordon
AU - Ruiz-Carmona, Roque
AU - Salinas, Ricardo
AU - Sebo, Kim M.
AU - Venkatesan, Sudharshan
N1 - Accepted version, minor editing. New figure showing Sr and Ba lines. Section 4.7 revised
PY - 2023/8/14
Y1 - 2023/8/14
N2 - This study focuses on Pristine$\_180956.78$$-$$294759.8$ (hereafter P180956, $[Fe/H] =-1.95\pm0.02$), a star selected from the Pristine Inner Galaxy Survey (PIGS), and followed-up with the recently commissioned Gemini High-resolution Optical SpecTrograph (GHOST) at the Gemini South telescope. The GHOST spectrograph's high efficiency in the blue spectral region ($3700-4800$~\AA) enables the detection of elemental tracers of early supernovae (\eg Al, Mn, Sr, Eu). The star exhibits chemical signatures resembling those found in ultra-faint dwarf systems, characterised by very low abundances of neutron-capture elements (Sr, Ba, Eu), which are uncommon among stars in the Milky Way halo. Our analysis suggests that P180956 bears the chemical imprints of a small number (2 or 4) of low-mass hypernovae ($\sim10-15 M_{\odot}$), which are needed to mostly reproduce the abundance pattern of the light-elements (\eg [Si, Ti/Mg, Ca] $\sim0.6$), and one fast-rotating intermediate-mass supernova ($\sim300\kms$, $\sim80-120 M_{\odot}$), which is the main channel contributing to the high [Sr/Ba] ($\sim +1.2$). The small pericentric ($\sim0.7$ kpc) and apocentric ($\sim13$ kpc) distances and its orbit confined to the plane ($\lesssim 2$ kpc), indicate that this star was likely accreted during the early Galactic assembly phase. Its chemo-dynamical properties suggest that P180956 formed in a system similar to an ultra-faint dwarf galaxy accreted either alone, as one of the low-mass building blocks of the proto-Galaxy, or as a satellite of Gaia-Sausage-Enceladus. The combination of Gemini's large aperture with GHOST's high efficiency and broad spectral coverage makes this new spectrograph one of the leading instruments for near-field cosmology investigations.
AB - This study focuses on Pristine$\_180956.78$$-$$294759.8$ (hereafter P180956, $[Fe/H] =-1.95\pm0.02$), a star selected from the Pristine Inner Galaxy Survey (PIGS), and followed-up with the recently commissioned Gemini High-resolution Optical SpecTrograph (GHOST) at the Gemini South telescope. The GHOST spectrograph's high efficiency in the blue spectral region ($3700-4800$~\AA) enables the detection of elemental tracers of early supernovae (\eg Al, Mn, Sr, Eu). The star exhibits chemical signatures resembling those found in ultra-faint dwarf systems, characterised by very low abundances of neutron-capture elements (Sr, Ba, Eu), which are uncommon among stars in the Milky Way halo. Our analysis suggests that P180956 bears the chemical imprints of a small number (2 or 4) of low-mass hypernovae ($\sim10-15 M_{\odot}$), which are needed to mostly reproduce the abundance pattern of the light-elements (\eg [Si, Ti/Mg, Ca] $\sim0.6$), and one fast-rotating intermediate-mass supernova ($\sim300\kms$, $\sim80-120 M_{\odot}$), which is the main channel contributing to the high [Sr/Ba] ($\sim +1.2$). The small pericentric ($\sim0.7$ kpc) and apocentric ($\sim13$ kpc) distances and its orbit confined to the plane ($\lesssim 2$ kpc), indicate that this star was likely accreted during the early Galactic assembly phase. Its chemo-dynamical properties suggest that P180956 formed in a system similar to an ultra-faint dwarf galaxy accreted either alone, as one of the low-mass building blocks of the proto-Galaxy, or as a satellite of Gaia-Sausage-Enceladus. The combination of Gemini's large aperture with GHOST's high efficiency and broad spectral coverage makes this new spectrograph one of the leading instruments for near-field cosmology investigations.
KW - astro-ph.GA
KW - astro-ph.IM
KW - astro-ph.SR
U2 - 10.1093/mnras/stae244
DO - 10.1093/mnras/stae244
M3 - Article
SN - 0035-8711
JO - Monthly Notices of the Royal Astronomical Society (MNRAS)
JF - Monthly Notices of the Royal Astronomical Society (MNRAS)
ER -