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A stellar stream remnant of a globular cluster below the metallicity floor

Nature volume 601, pages 45–48 (2022)Cite this article

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Abstract

Stellar ejecta gradually enrich the gas out of which subsequent stars form, making the least chemically enriched stellar systems direct fossils of structures formed in the early Universe1. Although a few hundred stars with metal content below 1,000th of the solar iron content are known in the Galaxy2,3,4, none of them inhabit globular clusters, some of the oldest known stellar structures. These show metal content of at least approximately 0.2% of the solar metallicity \(([{\rm{Fe}}/{\rm{H}}]\gtrsim -2.7)\). This metallicity floor appears universal5,6, and it has been proposed that protogalaxies that merged into the galaxies we observe today were simply not massive enough to form clusters that survived to the present day7. Here we report observations of a stellar stream, C-19, whose metallicity is less than 0.05% of the solar metallicity \(([{\rm{F}}{\rm{e}}/{\rm{H}}]=-3.38\pm 0.06\,({\rm{s}}{\rm{t}}{\rm{a}}{\rm{t}}{\rm{i}}{\rm{s}}{\rm{t}}{\rm{i}}{\rm{c}}{\rm{a}}{\rm{l}})\pm 0.20\,({\rm{s}}{\rm{y}}{\rm{s}}{\rm{t}}{\rm{e}}{\rm{m}}{\rm{a}}{\rm{t}}{\rm{i}}{\rm{c}}))\). The low metallicity dispersion and the chemical abundances of the C-19 stars show that this stream is the tidal remnant of the most metal-poor globular cluster ever discovered, and is significantly below the purported metallicity floor: clusters with significantly lower metallicities than observed today existed in the past and contributed their stars to the Milky Way halo.

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Fig. 1: Properties of the C-19 member stars.
Fig. 2: Metallicity properties of C-19 and its stars observed by spectroscopy.
Fig. 3: High-resolution GRACES spectra for three members of C-19.

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Data availability

The data used in this article are listed in Extended Data Tables 1–5.

Code availability

The codes used for the analysis were not designed to be made public but can be requested from the corresponding author.

References

  1. Frebel, A. & Norris, J. E. Near-field cosmology with extremely metal-poor stars. Ann. Rev. Astron. Astrophys. 53, 631–688 (2015).

    Article  ADS  CAS  Google Scholar 

  2. Yong, D. et al. The most metal-poor stars. III. The metallicity distribution function and carbon-enhanced metal-poor fraction. Astrophys. J. 762, 27 (2013).

    Article  ADS  Google Scholar 

  3. Li, H., Tan, K. & Zhao, G. A catalog of 10,000 very metal-poor stars from LAMOST DR3. Astrophys. J. Supp. 238, 16 (2018).

    Article  ADS  Google Scholar 

  4. Aguado, D. S. et al. The Pristine survey - VI. The first three years of medium-resolution follow-up spectroscopy of Pristine EMP star candidates. Mon. Not. R. Astron. Soc. 490, 2241–2253 (2019).

    Article  ADS  CAS  Google Scholar 

  5. Beasley, M. A. et al. An old, metal-poor globular cluster in Sextans A and the metallicity floor of globular cluster systems. Mon. Not. R. Astron. Soc. 487, 1986–1993 (2019).

    Article  ADS  CAS  Google Scholar 

  6. Wan, Z. et al. The tidal remnant of an unusually metal-poor globular cluster. Nature 583, 768–770 (2020).

    Article  ADS  CAS  PubMed  Google Scholar 

  7. Kruijssen, J. M. D. The minimum metallicity of globular clusters and its physical origin - implications for the galaxy mass-metallicity relation and observations of proto-globular clusters at high redshift. Mon. Not. R. Astron. Soc. 486, L20–L25 (2019).

    Article  ADS  CAS  Google Scholar 

  8. Ibata, R. et al. Charting the Galactic acceleration field. I. A search for stellar streams with Gaia DR2 and EDR3 with follow-up from ESPaDOnS and UVES. Astrophys. J. 914, 123 (2021).

    Article  ADS  CAS  Google Scholar 

  9. Gaia Collaboration et al. Gaia Early Data Release 3. Summary of the contents and survey properties. Astron. Astrophys. 649, A1 (2021).

    Article  Google Scholar 

  10. Starkenburg, E. et al. The Pristine survey - I. Mining the Galaxy for the most metal-poor stars. Mon. Not. R. Astron. Soc. 471, 2587–2604 (2017).

    Article  ADS  CAS  Google Scholar 

  11. Harris, W. E. A catalog of parameters for globular clusters in the Milky Way. Astron. J. 112, 1487 (1996).

    Article  ADS  Google Scholar 

  12. Willman, B. & Strader, J. ”Galaxy,” defined. Astron. J. 144, 76 (2012).

    Article  ADS  Google Scholar 

  13. Leaman, R. Insights into pre-enrichment of star clusters and self-enrichment of dwarf galaxies from their intrinsic metallicity dispersions. Astron. J. 144, 183 (2012).

    Article  ADS  Google Scholar 

  14. Kirby, E. N. et al. The universal stellar mass-stellar metallicity relation for dwarf galaxies. Astrophys. J. 779, 102 (2013).

    Article  ADS  Google Scholar 

  15. Gratton, R. G., Carretta, E. & Bragaglia, A. Multiple populations in globular clusters. Lessons learned from the Milky Way globular clusters. Astron. Astrophys. R. 20, 50 (2012).

    Article  ADS  Google Scholar 

  16. Bastian, N. & Lardo, C. Multiple stellar populations in globular clusters. Ann. Rev. Astron. Astrophys. 56, 83–136 (2018).

    Article  ADS  CAS  Google Scholar 

  17. Ji, A. P. et al. The Southern Stellar Stream Spectroscopic Survey (S5): chemical abundances of seven stellar streams. Astron. J. 160, 181 (2020).

    Article  ADS  CAS  Google Scholar 

  18. Roederer, I. U. Are there any stars lacking neutron-capture elements? Evidence from strontium and barium. Astron. J. 145, 26 (2013).

    Article  ADS  Google Scholar 

  19. Côté, B. et al. Neutron star mergers might not be the only source of r-process elements in the Milky Way. Astrophys. J. 875, 106 (2019).

    Article  ADS  Google Scholar 

  20. Ji, A. P., Frebel, A., Simon, J. D. & Chiti, A. Complete element abundances of nine stars in the r-process galaxy Reticulum II. Astrophys. J. 830, 93 (2016).

    Article  ADS  Google Scholar 

  21. Hansen, T. T. et al. An r-process enhanced star in the dwarf galaxy Tucana III. Astrophys. J. 838, 44 (2017).

    Article  ADS  Google Scholar 

  22. Roederer, I. U. Primordial r-process dispersion in metal-poor globular clusters. Astrophys. J. Lett. 732, L17 (2011).

    Article  ADS  Google Scholar 

  23. Yoon, J. et al. Galactic archeology with the AEGIS survey: the evolution of carbon and iron in the Galactic halo. Astrophys. J. 861, 146 (2018).

    Article  ADS  Google Scholar 

  24. Norris, J. E. et al. The most metal-poor stars. IV. The two populations with [Fe/H] < −3.0. Astrophys. J. 762, 28 (2013).

    Article  ADS  Google Scholar 

  25. Youakim, K. et al. The Pristine survey - VIII. The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime. Mon. Not. R. Astron. Soc. 492, 4986–5002 (2020).

    Article  ADS  CAS  Google Scholar 

  26. Roederer, I. U. & Gnedin, O. Y. High-resolution optical spectroscopy of stars in the Sylgr stellar stream. Astrophys. J. 883, 84 (2019).

    Article  ADS  CAS  Google Scholar 

  27. Larsen, S. S., Romanowsky, A. J., Brodie, J. P. & Wasserman, A. An extremely metal-deficient globular cluster in the Andromeda galaxy. Science 370, 970–973 (2020).

    Article  ADS  CAS  PubMed  Google Scholar 

  28. Bonaca, A., Hogg, D. W., Price-Whelan, A. M. & Conroy, C. The spur and the gap in GD-1: dynamical evidence for a dark substructure in the Milky Way halo. Astrophys. J. 880, 38 (2019).

    Article  ADS  CAS  Google Scholar 

  29. Ibata, R. A., Lewis, G. F. & Martin, N. F. Feeling the pull: a study of natural galactic accelerometers. I. Photometry of the delicate stellar stream of the Palomar 5 globular cluster. Astrophys. J. 819, 1 (2016).

    Article  ADS  Google Scholar 

  30. Erkal, D., Koposov, S. E. & Belokurov, V. A sharper view of Pal 5’s tails: discovery of stream perturbations with a novel non-parametric technique. Mon. Not. R. Astron. Soc. 470, 60–84 (2017).

    Article  ADS  CAS  Google Scholar 

  31. Ma, X. et al. The origin and evolution of the galaxy mass-metallicity relation. Mon. Not. R. Astron. Soc. 456, 2140–2156 (2016).

    Article  ADS  CAS  Google Scholar 

  32. Kielty, C. L. et al. The Pristine survey - XII. Gemini-GRACES chemo-dynamical study of newly discovered extremely metal-poor stars in the Galaxy. Mon. Not. R. Astron. Soc. 506, 1438–1461 (2021).

    Article  ADS  Google Scholar 

  33. Malhan, K., Ibata, R. A. & Martin, N. F. Ghostly tributaries to the Milky Way: charting the halo’s stellar streams with the Gaia DR2 catalogue. Mon. Not. R. Astron. Soc. 481, 3442–3455 (2018).

    Article  ADS  CAS  Google Scholar 

  34. Carlberg, R. G. Globular clusters in a cosmological N-body simulation. Astrophys. J. 861, 69 (2018).

    Article  ADS  Google Scholar 

  35. Malhan, K., Ibata, R. A., Carlberg, R. G., Valluri, M. & Freese, K. Butterfly in a cocoon, understanding the origin and morphology of globular cluster streams: the case of GD-1. Astrophys. J. 881, 106 (2019).

    Article  ADS  CAS  Google Scholar 

  36. Martin, N. F. et al. The Pristine survey – XVI. The metallicity of 21 stellar streams around the Milky Way detected with the STREAMFINDER in Gaia EDR3. Mon. Not. R. Astron. Soc submitted (2021).

  37. Bressan, A. et al. PARSEC: stellar tracks and isochrones with the PAdova and TRieste stellar evolution code. Mon. Not. R. Astron. Soc. 427, 127–145 (2012).

    Article  ADS  CAS  Google Scholar 

  38. Maraston, C. Evolutionary population synthesis: models, analysis of the ingredients and application to high-z galaxies. Mon. Not. R. Astron. Soc. 362, 799–825 (2005).

    Article  ADS  CAS  Google Scholar 

  39. Deason, A. J., Belokurov, V. & Evans, N. W. The Milky Way stellar halo out to 40 kpc: squashed, broken but smooth. Mon. Not. R. Astron. Soc. 416, 2903–2915 (2011).

    Article  ADS  Google Scholar 

  40. Lindegren, L. et al. Gaia Early Data Release 3. Parallax bias versus magnitude, colour, and position. Astron. Astrophys. 649, A4 (2021).

    Article  Google Scholar 

  41. Ibata, R. A., Malhan, K., Martin, N. F. & Starkenburg, E. Phlegethon, a nearby 75-degree-long retrograde Stellar Stream. Astrophys. J. 865, 85 (2018).

    Article  ADS  Google Scholar 

  42. Chene, A.-N. et al. in Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, Vol. 9151 (eds. Navarro, R. et al.) 915147 (SPIE, 2014).

  43. Pazder, J., Fournier, P., Pawluczyk, R. & van Kooten, M. in Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, Vol. 9151 (eds. Navarro, R. et al.) 915124 (SPIE, 2014).

  44. Martioli, E. et al. in Software and Cyberinfrastructure for Astronomy II Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, Vol. 8451 (eds. Radziwill, N. M. & Chiozzi, G.) 84512B (SPIE, 2012).

  45. Schlegel, D. J., Finkbeiner, D. P. & Davis, M. Maps of dust infrared emission for use in estimation of reddening and cosmic microwave background radiation foregrounds. Astrophys. J. 500, 525 (1998).

    Article  ADS  Google Scholar 

  46. Schlafly, E. F. & Finkbeiner, D. P. Measuring reddening with Sloan Digital Sky Survey stellar spectra and recalibrating SFD. Astrophys. J. 737, 103 (2011).

    Article  ADS  Google Scholar 

  47. González Hernández, J. I. & Bonifacio, P. A new implementation of the infrared flux method using the 2MASS catalogue. Astron. Astrophys. 497, 497–509 (2009).

    Article  ADS  Google Scholar 

  48. Mucciarelli, A., Bellazzini, M. & Massari, D. Exploiting the Gaia EDR3 photometry to derive stellar temperatures. Astron. Astrophys. (in the press).

  49. Mashonkina, L., Jablonka, P., Pakhomov, Y., Sitnova, T. & North, P. The formation of the Milky Way halo and its dwarf satellites; a NLTE-1D abundance analysis. I. Homogeneous set of atmospheric parameters. Astron. Astrophys. 604, A129 (2017).

    Article  ADS  Google Scholar 

  50. Karovicova, I. et al. Fundamental stellar parameters of benchmark stars from CHARA interferometry. I. Metal-poor stars. Astron. Astrophys. 640, A25 (2020).

    Article  CAS  Google Scholar 

  51. Giribaldi, R. E., da Silva, A. R., Smiljanic, R. & Cornejo Espinoza, D. TITANS metal-poor reference stars. I. Accurate effective temperatures and surface gravities for dwarfs and subgiants from 3D non-LTE H α profiles and Gaia parallaxes. Astron. Astrophys. 650, A194 (2021).

    Article  CAS  Google Scholar 

  52. Kurucz, R. L. ATLAS12, SYNTHE, ATLAS9, WIDTH9, et cetera. Mem. Soc. Astron. Ital. Suppl. 8, 14 (2005).

    ADS  Google Scholar 

  53. Sneden, C. A. Carbon and Nitrogen Abundances in Metal-Poor Stars. PhD thesis, Univ. of Texas at Austin (1973).

  54. Sobeck, J. S. et al. The abundances of neutron-capture species in the very metal-poor globular cluster M15: a uniform analysis of red giant branch and red horizontal branch stars. Astron. J. 141, 175 (2011).

    Article  ADS  Google Scholar 

  55. Placco, V. M. et al. Linemake: an atomic and molecular line list generator. Res. Notes AAS 5, 92 (2021).

    Article  ADS  Google Scholar 

  56. http://inspect-stars.net.

  57. http://nlte.mpia.de.

  58. Lind, K., Bergemann, M. & Asplund, M. Non-LTE line formation of Fe in late-type stars - II. 1D spectroscopic stellar parameters. Mon. Not. R. Astron. Soc. 427, 50–60 (2012).

    Article  ADS  CAS  Google Scholar 

  59. Bergemann, M. & Cescutti, G. Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy (2010).

  60. Bergemann, M., Lind, K., Collet, R., Magic, Z. & Asplund, M. Non-LTE line formation of Fe in late-type stars - I. Standard stars with 1D and <3D> model atmospheres. Mon. Not. R. Astron. Soc. 427, 27–49 (2012).

    Article  ADS  CAS  Google Scholar 

  61. Mashonkina, L., Korn, A. J. & Przybilla, N. A non-LTE study of neutral and singly-ionized calcium in late-type stars. Astron. Astrophys. 461, 261–275 (2007).

    Article  ADS  CAS  Google Scholar 

  62. Asplund, M., Grevesse, N., Sauval, A. J. & Scott, P. The chemical composition of the Sun. Ann. Rev. Astron. Astrophys. 47, 481–522 (2009).

    Article  ADS  CAS  Google Scholar 

  63. Tody, D. in Astronomical Data Analysis Software and Systems II Astronomical Society of the Pacific Conference Series, Vol. 52 (eds. Hanisch, R. J. et al.) 173 (1993).

  64. Aguado, D. S., Allende Prieto, C., González Hernández, J. I., Rebolo, R. & Caffau, E. New ultra metal-poor stars from SDSS: follow-up GTC medium-resolution spectroscopy. Astron. Astrophys. 604, A9 (2017).

    Article  ADS  Google Scholar 

  65. Aguado, D. S., González Hernández, J. I., Allende Prieto, C. & Rebolo, R. J0815+4729: a chemically primitive dwarf star in the galactic halo observed with Gran Telescopio Canarias. Astrophys. J. Lett. 852, L20 (2018).

    Article  ADS  Google Scholar 

  66. Allende Prieto, C. et al. Deep SDSS optical spectroscopy of distant halo stars. I. Atmospheric parameters and stellar metallicity distribution. Astron. Astrophys. 568, A7 (2014).

    Article  Google Scholar 

  67. Aguado, D. S., González Hernández, J. I., Allende Prieto, C. & Rebolo, R. WHT follow-up observations of extremely metal-poor stars identified from SDSS and LAMOST. Astron. Astrophys. 605, A40 (2017).

    Article  ADS  Google Scholar 

  68. Koesterke, L., Allende Prieto, C. & Lambert, D. L. Center-to-limb variation of solar three-dimensional hydrodynamical simulations. Astrophys. J. 680, 764–773 (2008).

    Article  ADS  Google Scholar 

  69. Boender, C. G. E., Rinnoy Kan, A. H. G., Timmer, G. T. & Stougie, L. A stochastic method for global optimization. Math. Program. 22, 125 (1982).

    Article  MathSciNet  MATH  Google Scholar 

  70. Wenger, M. et al. The SIMBAD astronomical database. The CDS reference database for astronomical objects. Astron. Astrophys. Suppl. Ser. 143, 9–22 (2000).

    Article  ADS  Google Scholar 

  71. Ochsenbein, F., Bauer, P. & Marcout, J. The VizieR database of astronomical catalogues. Astron. Astrophys. Suppl. Ser. 143, 23–32 (2000).

    Article  ADS  Google Scholar 

  72. http://www.inasan.rssi.ru/~lima/pristine.

Download references

Acknowledgements

N.F.M., R.A.I., A.A. and Z.Y. gratefully acknowledge support from the French National Research Agency (ANR)-funded project Pristine (ANR-18-CE31-0017) along with funding from Centre National de la Recherche Scientifique (CNRS)–INSU through the Programme National de Cosmologie et Galaxies and through CNRS grant PICS07708 and from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 834148). K.A.V. is grateful for funding through the National Science and Engineering Research Council of Canada (NSERC) Discovery Grants and CREATE programmes. E.S. acknowledges funding through VIDI grant ‘Pushing Galactic Archaeology to its Limits’ (project number VI.Vidi.193.093), which is funded by the Dutch Research Council (NWO). J.I.G.H. acknowledges financial support from Spanish Ministry of Science and Innovation (MICINN) project AYA2017-86389-P, and also from the Spanish MICINN under the 2013 Ramón y Cajal programme (RYC-2013-14875). G.F.T. acknowledges support from the Agencia Estatal de Investigación of the Spanish MCINN (grant number FJC2018-037323-I). We thank the Canada–France–Hawaii Telescope (CFHT) staff for performing the Pristine observations in queue mode, for their reactivity in adapting the schedule and for answering questions during the data-reduction process. We are also grateful to the High Performance Computing Centre of the University of Strasbourg and its staff for very generous time allocation and for their support during the development of the STREAMFINDER project. This research used the SIMBAD database70, managed and run  at CDS, Strasbourg, France. This research used the VizieR catalogue access tool71, CDS, Strasbourg, France. This work is based on observations obtained with MegaPrime–MegaCam, a joint project of the CFHT and CEA–DAPNIA, at the CFHT, which is operated by the National Research Council of Canada, the Institut National des Science de l’Univers of the French CNRS and the University of Hawaii. ESPaDOnS is a collaborative project funded by France (CNRS, MENESR, OMP, and LATT), Canada (NSERC), the CFHT and the European Space Agency. Data were reduced with use of the CFHT-developed OPERA data-reduction pipeline. We recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the Indigenous Hawaiian community. We are very fortunate to have had the opportunity to conduct observations from this mountain. This work is based on observations obtained with Gemini Remote Access to CFHT ESPaDOnS Spectrograph (GRACES), as part of the Gemini Large and Long Program, GN-2020B-LP-102. The international Gemini Observatory, a program of NSF’s NOIRLab, is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil) and Korea Astronomy and Space Science Institute (Republic of Korea). This work is based on observations made with the GTC telescope, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, under Director’s Discretionary Time. This work was partly based on data obtained with the instrument OSIRIS, built by a consortium led by the Instituto de Astrofísica de Canarias in collaboration with the Instituto de Astronomía of the Universidad Autónoma de México. OSIRIS was funded by GRANTECAN and the National Plan of Astronomy and Astrophysics of the Spanish Government. This work used data from the European Space Agency mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Guo Shoujing Telescope (LAMOST) is a national major scientific project of the Chinese Academy of Sciences. Funding for the project was provided by the National Development and Reform Commission. LAMOST is operated and managed by the National Astronomical Observatories, Chinese Academy of Sciences.

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Authors and Affiliations

  1. Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, Strasbourg, France

    Nicolas F. Martin, Rodrigo A. Ibata, Anke Arentsen & Zhen Yuan

  2. Max-Planck-Institut für Astronomie, Heidelberg, Germany

    Nicolas F. Martin & Morgan Fouesneau

  3. Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada

    Kim A. Venn, Federico Sestito, Sébastien Fabbro & Julio F. Navarro

  4. Institute of Astronomy, University of Cambridge, Cambridge, UK

    David S. Aguado

  5. Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain

    David S. Aguado, Jonay I. González Hernández, Carlos Allende Prieto & Guillaume F. Thomas

  6. Dipartimento di Fisica e Astronomia, Universitá degli Studi di Firenze, Sesto Fiorentino, Italy

    David S. Aguado

  7. Kapteyn Astronomical Institute, University of Groningen, Groningen, the Netherlands

    Else Starkenburg

  8. Departamento de Astrofísica, Universidad de La Laguna, La Laguna, Tenerife, Spain

    Jonay I. González Hernández, Carlos Allende Prieto & Guillaume F. Thomas

  9. GEPI, Observatoire de Paris, Université PSL, CNRS, Meudon, France

    Piercarlo Bonifacio, Elisabetta Caffau & Pascale Jablonka

  10. Department of Astronomy & Astrophysics, University of Toronto, Toronto, Ontario, Canada

    Raymond G. Carlberg

  11. NRC Herzberg Astronomy & Astrophysics, Victoria, British Columbia, Canada

    Sébastien Fabbro & Alan W. McConnachie

  12. Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France

    Vanessa Hill & Georges Kordopatis

  13. Laboratoire d’astrophysique, École Polytechnique Fédérale de Lausanne, Observatoire, Versoix, Switzerland

    Pascale Jablonka

  14. Dipartimento di Fisica & Astronomia “Augusto Righi”, Alma Mater Studiorum, Università di Bologna, Bologna, Italy

    Carmela Lardo & Alessio Mucciarelli

  15. The Oskar Klein Centre, Department of Physics, Stockholm University, Stockholm, Sweden

    Khyati Malhan

  16. Institute of Astronomy, Russian Academy of Sciences, Moscow, Russia

    Lyudmila I. Mashonkina

  17. UK Astronomy Technology Centre, Royal Observatory, Edinburgh, UK

    Rubén Sánchez-Janssen

  18. INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Bologna, Italy

    Alessio Mucciarelli

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  1. Nicolas F. Martin
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  2. Kim A. Venn
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  3. David S. Aguado
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  19. Khyati Malhan
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  20. Lyudmila I. Mashonkina
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  25. Zhen Yuan
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  26. Alessio Mucciarelli
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N.F.M. is a co-leader of the Pristine survey, led the discovery of the C-19 stream, coordinated the spectroscopic observations and co-led the writing of the manuscript. K.A.V. led the GRACES spectroscopic follow-up and the analysis of the resulting spectra, and co-led the writing of the manuscript. D.S.A. led the analysis of the OSIRIS spectra and the writing of the corresponding section of the manuscript. E.S. is a co-leader of the Pristine survey and derived the Pristine photometric metallicities. J.I.G.H. coordinated the OSIRIS follow-up, performed the radial velocity analysis of these spectra and was greatly involved in writing this part of the manuscript. R.A.I. led the STREAMFINDER analysis and derived the orbit of the stream. P.B., E.C. and F.S. derived stellar and orbital parameters for the stars with spectroscopic follow-up. All other authors helped in the development of the Pristine survey and all authors assisted in the development and writing of the paper. A.M. derived the relations used to infer the stellar parameters of the spectroscopically observed stars.

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Correspondence to Nicolas F. Martin.

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Extended data figures and tables

Extended Data Fig. 1 Pristine photometric information for all stars of the C-19 stream selected by STREAMFINDER and present in the Pristine survey.

Large symbols represent stars with G0 < 19.0, for which the STREAMFINDER selection is very reliable, and small symbols represent stars fainter than this limit, which are more likely contaminated in the STREAMFINDER catalogue (see also Fig. 1). The lines represent model expectations as determined from the spectral libraries and filter response curves, without an assumption on whether the star is a dwarf or a giant10. Both model lines and data points are color-coded by their \({[{\rm{Fe}}/{\rm{H}}]}_{{\rm{Pristine}}}\) metallicities. Most C-19 candidate members are located in the region that corresponds to metallicities below \([{\rm{Fe}}/{\rm{H}}]=-3.0\) (above the blue line). For the large data points, we specifically used a photometric metallicity model tailored to giant stars. Near the tip of the red giant branch, it deviates significantly from the generic model represented by the coloured lines and explains the higher metallicity of the right-most point compared with the models.

Extended Data Fig. 2 Favourite orbital solutions for the C-19 stream.

The dashed line shows the orbit of C-19 constrained using the proper motions (red symbols in a, b) of C-19 members identified by STREAMFINDER, their Gaia parallaxes (c), their radial velocities when available (d) and their location on the sky compared with the distribution of extinction45 (e). The orbit determined without using the Gaia parallax information but instead anchoring the distance at 18 kpc is represented by the dotted line. f, g The two orbits, integrated for ±1 Gyr, projected on the Galactic plane, and in the R–z plane. The thick red lines correspond to the part of the orbits that overlaps the observed C-19 member stars.

Extended Data Fig. 3 Spectra of the C-19 member stars observed with OSIRIS, normalized using a running mean filter after removing the velocity signal in the rest frame (black lines), together with the best fit (blue lines) derived by adopting a fitting procedure.

The metallicity, [Fe/H], computed from [M/H] and [Ca/H] is also indicated for each target (see the text for more details).

Extended Data Table 1 List of potential C-19 members from the STREAMFINDER sample
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Extended Data Table 2 Summary of observations for the C-19 candidate stars
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Extended Data Table 3 Spectroscopic parameters and one-dimensional LTE chemical abundances for the Gemini–GRACES spectra
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Extended Data Table 4 Spectral lines and atomic data used for the chemical abundances for the Gemini–GRACES spectra
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Extended Data Table 5 Stellar parameters and abundances of C-19 stars observed with GTC–OSIRIS
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Martin, N.F., Venn, K.A., Aguado, D.S. et al. A stellar stream remnant of a globular cluster below the metallicity floor. Nature 601, 45–48 (2022). https://doi.org/10.1038/s41586-021-04162-2

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