GHOST Commissioning Science Results. IV. Chemodynamical Analyses of Milky Way Satellites Sagittarius II and Aquarius II
We present Gemini/GHOST high-resolution spectra of five stars observed in two low surface brightness Milky Way satellites, Sagittarius II (Sgr2) and Aquarius II (Aqu2). For Aqu2, the velocities and metallicities of the two stars are consistent with membership in a dark-matter-dominated ultra-faint d...
Saved in:
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
|
| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/add5f9 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1839635438848966656 |
|---|---|
| author | Daria Zaremba Kim Venn Christian R. Hayes Raphaël Errani Triana Cornejo Jennifer Glover Jaclyn Jensen Alan W. McConnachie Julio F. Navarro John Pazder Federico Sestito André Anthony Dave Andersen Gabriella Baker Timothy Chin Vladimir Churilov Ruben Diaz Tony Farrell Veronica Firpo Manuel Gomez-Jimenez David Henderson Venu M. Kalari Jon Lawrence Steve Margheim Bryan Miller J. Gordon Robertson Roque Ruiz-Carmona Katherine Silversides Karleyne Silva Peter J. Young Ross Zhelem |
| author_facet | Daria Zaremba Kim Venn Christian R. Hayes Raphaël Errani Triana Cornejo Jennifer Glover Jaclyn Jensen Alan W. McConnachie Julio F. Navarro John Pazder Federico Sestito André Anthony Dave Andersen Gabriella Baker Timothy Chin Vladimir Churilov Ruben Diaz Tony Farrell Veronica Firpo Manuel Gomez-Jimenez David Henderson Venu M. Kalari Jon Lawrence Steve Margheim Bryan Miller J. Gordon Robertson Roque Ruiz-Carmona Katherine Silversides Karleyne Silva Peter J. Young Ross Zhelem |
| author_sort | Daria Zaremba |
| collection | DOAJ |
| description | We present Gemini/GHOST high-resolution spectra of five stars observed in two low surface brightness Milky Way satellites, Sagittarius II (Sgr2) and Aquarius II (Aqu2). For Aqu2, the velocities and metallicities of the two stars are consistent with membership in a dark-matter-dominated ultra-faint dwarf galaxy (UFD). The chemical abundance ratios suggest inefficient star formation from only one or a few supernovae (e.g., low Na, Sr, Ba), and enriched potassium (K) from super-AGB stars. For Sgr2, the velocity and metallicity dispersions of its members are not clearly resolved, and our detailed chemical abundances show typical ratios for metal-poor stars, with low dispersions. There is only one exception—we report the discovery of an r -process enhanced star (Sgr 2584, [Eu/Fe] = +0.7 ± 0.2; thus, an r-I star). As r-I stars are found in both UFDs (Tuc III, Tuc IV, and Grus II) and globular clusters (M15 and M92), then this does not help to further classify the nature of Sgr2. Our exploration of Sgr2 demonstrates the difficulty in classifying some of the faintest (ambiguous) satellites. We advocate for additional diagnostics in analyzing the ambiguous systems, such as exploring radial segregation (by mass and/or chemistry), N -body simulations, and the need for dark matter to survive Galactic tidal effects. The spectra analyzed in this paper were taken as part of the GHOST commissioning observations, testing faint observation limits ( G < 18.8) and the single and double integrated field unit observing modes. |
| format | Article |
| id | doaj-art-ec8ea56c01cc4e81a8897fd2dcfde8c6 |
| institution | Matheson Library |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-ec8ea56c01cc4e81a8897fd2dcfde8c62025-07-09T08:31:31ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01987221710.3847/1538-4357/add5f9GHOST Commissioning Science Results. IV. Chemodynamical Analyses of Milky Way Satellites Sagittarius II and Aquarius IIDaria Zaremba0Kim Venn1https://orcid.org/0000-0003-4134-2042Christian R. Hayes2https://orcid.org/0000-0003-2969-2445Raphaël Errani3Triana Cornejo4Jennifer Glover5Jaclyn Jensen6https://orcid.org/0000-0002-4350-7632Alan W. McConnachie7https://orcid.org/0000-0003-4666-6564Julio F. Navarro8https://orcid.org/0000-0003-3862-5076John Pazder9Federico Sestito10https://orcid.org/0000-0002-3182-3574André Anthony11Dave Andersen12Gabriella Baker13Timothy Chin14Vladimir Churilov15Ruben Diaz16https://orcid.org/0000-0001-9716-5335Tony Farrell17Veronica Firpo18Manuel Gomez-Jimenez19David Henderson20Venu M. Kalari21https://orcid.org/0000-0002-4641-2532Jon Lawrence22Steve Margheim23https://orcid.org/0000-0001-8205-9441Bryan Miller24J. Gordon Robertson25Roque Ruiz-Carmona26Katherine Silversides27Karleyne Silva28https://orcid.org/0000-0003-1949-4621Peter J. Young29Ross Zhelem30Department of Physics and Astronomy, University of Victoria , PO Box 3055, STN CSC, Victoria BC V8W 3P6, Canada ; dariazaremba@uvic.caDepartment of Physics and Astronomy, University of Victoria , PO Box 3055, STN CSC, Victoria BC V8W 3P6, Canada ; dariazaremba@uvic.caNRC Herzberg Astronomy & Astrophysics , 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USAMcWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University , Pittsburgh, PA 15213, USADepartment of Physics and Astronomy, University of Victoria , PO Box 3055, STN CSC, Victoria BC V8W 3P6, Canada ; dariazaremba@uvic.caDepartment of Physics and Astronomy, University of Victoria , PO Box 3055, STN CSC, Victoria BC V8W 3P6, Canada ; dariazaremba@uvic.ca; Department of Physics, McGill University , 3600 Rue University, Montreal, QC, CanadaDepartment of Physics and Astronomy, University of Victoria , PO Box 3055, STN CSC, Victoria BC V8W 3P6, Canada ; dariazaremba@uvic.caDepartment of Physics and Astronomy, University of Victoria , PO Box 3055, STN CSC, Victoria BC V8W 3P6, Canada ; dariazaremba@uvic.ca; NRC Herzberg Astronomy & Astrophysics , 5071 West Saanich Road, Victoria, BC V9E 2E7, CanadaDepartment of Physics and Astronomy, University of Victoria , PO Box 3055, STN CSC, Victoria BC V8W 3P6, Canada ; dariazaremba@uvic.caDepartment of Physics and Astronomy, University of Victoria , PO Box 3055, STN CSC, Victoria BC V8W 3P6, Canada ; dariazaremba@uvic.ca; NRC Herzberg Astronomy & Astrophysics , 5071 West Saanich Road, Victoria, BC V9E 2E7, CanadaDepartment of Physics and Astronomy, University of Victoria , PO Box 3055, STN CSC, Victoria BC V8W 3P6, Canada ; dariazaremba@uvic.ca; Department of Physics, Astronomy and Mathematics, University of Hertfordshire , Hatfield, AL10 9AB, UKNRC Herzberg Astronomy & Astrophysics , 5071 West Saanich Road, Victoria, BC V9E 2E7, CanadaDepartment of Physics and Astronomy, University of Victoria , PO Box 3055, STN CSC, Victoria BC V8W 3P6, Canada ; dariazaremba@uvic.ca; TMT International Observatory , 100 W. Walnut Street, Suite 300, Pasadena, CA 91124, USAAustralian Astronomical Optics, Macquarie University , 105 Delhi Road, North Ryde, NSW 2113, AustraliaAustralian Astronomical Optics, Macquarie University , 105 Delhi Road, North Ryde, NSW 2113, AustraliaAustralian Astronomical Optics, Macquarie University , 105 Delhi Road, North Ryde, NSW 2113, AustraliaGemini Observatory/NSF’s NOIRLab , Casilla 603, La Serena, ChileAustralian Astronomical Optics, Macquarie University , 105 Delhi Road, North Ryde, NSW 2113, AustraliaGemini Observatory/NSF’s NOIRLab , Av. J. Cisternas 1500 N., 1720236, La Serena, ChileGemini Observatory/NSF’s NOIRLab , Casilla 603, La Serena, ChileGemini Observatory/NSF’s NOIRLab , 670 North A’ohōkū Place, Hilo, HI 96720, USAGemini Observatory/NSF’s NOIRLab , Casilla 603, La Serena, ChileAustralian Astronomical Optics, Macquarie University , 105 Delhi Road, North Ryde, NSW 2113, AustraliaRubin Observatory/NSF’s NOIRLab , Casilla 603, La Serena, ChileGemini Observatory/NSF’s NOIRLab , Casilla 603, La Serena, ChileAustralian Astronomical Optics, Macquarie University , 105 Delhi Road, North Ryde, NSW 2113, Australia; Sydney Institute for Astronomy, School of Physics, University of Sydney , NSW 2006, AustraliaGemini Observatory/NSF’s NOIRLab , Casilla 603, La Serena, ChileNRC Herzberg Astronomy & Astrophysics , 5071 West Saanich Road, Victoria, BC V9E 2E7, CanadaGemini Observatory/NSF’s NOIRLab , Casilla 603, La Serena, ChileResearch School of Astronomy and Astrophysics, College of Science, Australian National University , Canberra 2611, AustraliaAustralian Astronomical Optics, Macquarie University , 105 Delhi Road, North Ryde, NSW 2113, AustraliaWe present Gemini/GHOST high-resolution spectra of five stars observed in two low surface brightness Milky Way satellites, Sagittarius II (Sgr2) and Aquarius II (Aqu2). For Aqu2, the velocities and metallicities of the two stars are consistent with membership in a dark-matter-dominated ultra-faint dwarf galaxy (UFD). The chemical abundance ratios suggest inefficient star formation from only one or a few supernovae (e.g., low Na, Sr, Ba), and enriched potassium (K) from super-AGB stars. For Sgr2, the velocity and metallicity dispersions of its members are not clearly resolved, and our detailed chemical abundances show typical ratios for metal-poor stars, with low dispersions. There is only one exception—we report the discovery of an r -process enhanced star (Sgr 2584, [Eu/Fe] = +0.7 ± 0.2; thus, an r-I star). As r-I stars are found in both UFDs (Tuc III, Tuc IV, and Grus II) and globular clusters (M15 and M92), then this does not help to further classify the nature of Sgr2. Our exploration of Sgr2 demonstrates the difficulty in classifying some of the faintest (ambiguous) satellites. We advocate for additional diagnostics in analyzing the ambiguous systems, such as exploring radial segregation (by mass and/or chemistry), N -body simulations, and the need for dark matter to survive Galactic tidal effects. The spectra analyzed in this paper were taken as part of the GHOST commissioning observations, testing faint observation limits ( G < 18.8) and the single and double integrated field unit observing modes.https://doi.org/10.3847/1538-4357/add5f9the Milky WayDwarf galaxiesStar clustersStellar abundancesAstronomical instrumentation |
| spellingShingle | Daria Zaremba Kim Venn Christian R. Hayes Raphaël Errani Triana Cornejo Jennifer Glover Jaclyn Jensen Alan W. McConnachie Julio F. Navarro John Pazder Federico Sestito André Anthony Dave Andersen Gabriella Baker Timothy Chin Vladimir Churilov Ruben Diaz Tony Farrell Veronica Firpo Manuel Gomez-Jimenez David Henderson Venu M. Kalari Jon Lawrence Steve Margheim Bryan Miller J. Gordon Robertson Roque Ruiz-Carmona Katherine Silversides Karleyne Silva Peter J. Young Ross Zhelem GHOST Commissioning Science Results. IV. Chemodynamical Analyses of Milky Way Satellites Sagittarius II and Aquarius II The Astrophysical Journal the Milky Way Dwarf galaxies Star clusters Stellar abundances Astronomical instrumentation |
| title | GHOST Commissioning Science Results. IV. Chemodynamical Analyses of Milky Way Satellites Sagittarius II and Aquarius II |
| title_full | GHOST Commissioning Science Results. IV. Chemodynamical Analyses of Milky Way Satellites Sagittarius II and Aquarius II |
| title_fullStr | GHOST Commissioning Science Results. IV. Chemodynamical Analyses of Milky Way Satellites Sagittarius II and Aquarius II |
| title_full_unstemmed | GHOST Commissioning Science Results. IV. Chemodynamical Analyses of Milky Way Satellites Sagittarius II and Aquarius II |
| title_short | GHOST Commissioning Science Results. IV. Chemodynamical Analyses of Milky Way Satellites Sagittarius II and Aquarius II |
| title_sort | ghost commissioning science results iv chemodynamical analyses of milky way satellites sagittarius ii and aquarius ii |
| topic | the Milky Way Dwarf galaxies Star clusters Stellar abundances Astronomical instrumentation |
| url | https://doi.org/10.3847/1538-4357/add5f9 |
| work_keys_str_mv | AT dariazaremba ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT kimvenn ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT christianrhayes ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT raphaelerrani ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT trianacornejo ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT jenniferglover ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT jaclynjensen ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT alanwmcconnachie ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT juliofnavarro ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT johnpazder ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT federicosestito ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT andreanthony ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT daveandersen ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT gabriellabaker ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT timothychin ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT vladimirchurilov ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT rubendiaz ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT tonyfarrell ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT veronicafirpo ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT manuelgomezjimenez ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT davidhenderson ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT venumkalari ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT jonlawrence ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT stevemargheim ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT bryanmiller ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT jgordonrobertson ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT roqueruizcarmona ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT katherinesilversides ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT karleynesilva ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT peterjyoung ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii AT rosszhelem ghostcommissioningscienceresultsivchemodynamicalanalysesofmilkywaysatellitessagittariusiiandaquariusii |