Omega Centauri (ω Cen) is the Milky Way’s most massive globular cluster, and has long been suspected of being the remnant core of an accreted dwarf galaxy. If this scenario is correct, ω Cen should be tidally limited and tidal debris should be spread along its orbit. Here we use N-body simulations to show that the recently discovered ‘Fimbulthul’ structure is the long-sought-for tidal stream of ω Cen, extending up to 28° from the cluster. Follow-up high-resolution spectroscopy of five stream stars shows that they are closely grouped in velocity, and have metallicities consistent with having originated in that cluster. Informed by our N-body simulations, we devise a selection filter that we apply to Gaia mission data to also uncover the stream in the highly contaminated and crowded field within 10° of ω Cen. Further modelling of the stream may help to constrain the dynamical history of the dwarf galaxy progenitor of this disrupting system and guide future searches for its remnant stars in the Milky Way.
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Harris, W. E. A catalog of parameters for globular clusters in the Milky Way. Astron. J. 112, 1487–1488 (1996).
Johnson, C. I. & Pilachowski, C. A. Chemical abundances for 855 giants in the globular cluster Omega Centauri (NGC 5139). Astrophys. J. 722, 1373–1410 (2010).
Bellini, A. et al. The HST large programme on Omega Centauri. II. Internal kinematics. Astrophys. J. 853, 86 (2018).
Marino, A. F. et al. The C+N+O abundance of Omega Centauri giant stars: implications for the chemical-enrichment scenario and the relative ages of different stellar populations. Astrophys. J. 746, 14 (2012).
Zinnecker, H., Keable, C. J., Dunlop, J. S., Cannon, R. D. & Griffiths, W. K. In The Harlow Shapley Symposium on Globular Cluster Systems in Galaxies (eds Grindlay, J. E. & Davis Philip, A. G.) 603–604 (IAU, 1988).
Majewski, S. R. et al. In Proc. 35th Liege International Astrophysical Colloquia, The Galactic Halo: From Globular Cluster to Field Stars (eds Noels, A. et al.) 619–622 (Institut d’Astrophysique et de Geophysique, 2000).
Bekki, K. & Freeman, K. C. Formation of Omega Centauri from an ancient nucleated dwarf galaxy in the young Galactic Disc. Mon. Not. R. Astron. Soc. 346, L11–L15 (2003).
Mizutani, A., Chiba, M. & Sakamoto, T. Kinematics of tidal debris from Omega Centauri’s progenitor galaxy. Astrophys. J. 589, L89–L92 (2003).
Ideta, M. & Makino, J. Formation of Omega Centauri by tidal stripping of a dwarf galaxy. Astrophys. J. 616, L107–L110 (2004).
Tsuchiya, T., Korchagin, V. I. & Dinescu, D. I. Disruption of a dwarf galaxy under strong shocking: the origin of Omega Centauri. Mon. Not. R. Astron. Soc. 350, 1141–1151 (2004).
Johnston, K. V., Hernquist, L. & Bolte, M. Fossil signatures of ancient accretion events in the halo. Astrophys. J. 465, 278–287 (1996).
Johnston, K. V., Zhao, H., Spergel, D. N. & Hernquist, L. Tidal streams as probes of the Galactic potential. Astrophys. J. 512, L109–L112 (1999).
Ibata, R., Lewis, G. F., Irwin, M., Totten, E. & Quinn, T. Great circle tidal streams: evidence for a nearly spherical massive dark halo around the Milky Way. Astrophys. J. 551, 294–311 (2001).
Law, D. R. & Majewski, S. R. The Sagittarius dwarf galaxy: a model for evolution in a triaxial Milky Way halo. Astrophys. J. 714, 229–254 (2010).
Küpper, A. H. W. et al. Globular cluster streams as Galactic high-precision scales—the poster child palomar 5. Astrophys. J. 803, 80 (2015).
Ibata, R. A., Lewis, G. F., Irwin, M. J. & Quinn, T. Uncovering cold dark matter halo substructure with tidal streams. Mon. Not. R. Astron. Soc. 332, 915–920 (2002).
Johnston, K. V., Spergel, D. N. & Haydn, C. How lumpy is the Milky Way’s dark matter halo? Astrophys. J. 570, 656–664 (2002).
Carlberg, R. G. Dark matter sub-halo counts via star stream crossings. Astrophys. J. 748, 20 (2012).
Erkal, D., Belokurov, V., Bovy, J. & Sanders, J. L. The number and size of subhalo-induced gaps in stellar streams. Mon. Not. R. Astron. Soc. 463, 102–119 (2016).
Gaia Collaboration Gaia data release 2. Summary of the contents and survey properties. Astron. Astrophys. 616, A1 (2018).
Gaia Collaboration Gaia data release 2. The astrometric solution. Astron. Astrophys. 616, A2 (2018).
Ibata, R., Malhan, K. & Martin, N. The streams of the gaping abyss: a population of entangled stellar streams surrounding the inner galaxy. Astrophys. J. 872, 152 (2019).
Malhan, K. & Ibata, R. A. STREAMFINDER—I. A new algorithm for detecting stellar streams. Mon. Not. R. Astron. Soc. 477, 4063–4076 (2018).
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).
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).
Ibata, R. A., Malhan, K., Martin, N. F. & Starkenburg, E. Phlegethon, a nearby 75 degree-long retrograde stellar stream. Astrophys. J. 865, 85 (2018).
Gaia Collaboration Gaia data release 2. Kinematics of globular clusters and dwarf galaxies around the Milky Way. Astron. Astrophys. 616, A12 (2018).
Bianchini, P., Varri, A. L., Bertin, G. & Zocchi, A. Rotating globular clusters. Astrophys. J. 772, 67 (2013).
Braga, V. F. et al. On the RR Lyrae stars in globulars. V. The complete near-infrared (JHKs) census of Omega Centauri RR Lyrae variables. Astron. J. 155, 137 (2018).
Fernandez-Trincado, J. G. et al. RAVE stars tidally stripped or ejected from the Omega Centauri globular cluster. Astron. Astrophys. 583, A76 (2015).
Gilmore, G., Wyse, R. F. G. & Norris, J. E. Deciphering the last major invasion of the Milky Way. Astrophys. J. 574, L39–L42 (2002).
Meza, A., Navarro, J. F., Abadi, M. G. & Steinmetz, M. Accretion relics in the solar neighbourhood: debris from omega Cen’s parent galaxy. Mon. Not. R. Astron. Soc. 359, 93–103 (2005).
Altmann, M., Catelan, M. & Zoccali, M. Searching for merger debris in the Galactic halo: chemodynamical evidence based on local blue HB stars. Astron. Astrophys. 439, L5–L8 (2005).
Majewski, S. R. et al. Exploring halo substructure with giant stars: substructure in the local halo as seen in the grid giant star survey including extended tidal debris from Omega Centauri. Astrophys. J. 747, L37 (2012).
Helmi, A., Veljanoski, J., Breddels, M. A., Tian, H. & Sales, L. V. A box full of chocolates: the rich structure of the nearby stellar halo revealed by Gaia and RAVE. Astron. Astrophys. 598, A58 (2017).
Koppelman, H., Helmi, A. & Veljanoski, J. One large blob and many streams frosting the nearby stellar halo in Gaia DR2. Astrophys. J. 860, L11 (2018).
Myeong, G. C., Evans, N. W., Belokurov, V., Sanders, J. L. & Koposov, S. E. Discovery of new retrograde substructures: the shards of Omega Centauri? Mon. Not. R. Astron. Soc. 478, 5449–5459 (2018).
Leon, S., Meylan, G. & Combes, F. Tidal tails around 20 Galactic globular clusters. Observational evidence for gravitational disk/bulge shocking. Astron. Astrophys. 359, 907–931 (2000).
Donati, J. F., Semel, M., Carter, B. D., Rees, D. E. & Collier Cameron, A. Spectropolarimetric observations of active stars. Mon. Not. R. Astron. Soc. 291, 658–682 (1997).
Starkenburg, E. et al. The NIR Ca ii triplet at low metallicity. Searching for extremely low-metallicity stars in classical dwarf galaxies. Astron. Astrophys. 513, 34 (2010).
Gratton, R. G. The absolute magnitude of field metal-poor horizontal branch stars. Mon. Not. R. Astron. Soc. 296, 739–745 (1998).
Jordi, C. et al. Gaia broad band photometry. Astron. Astrophys. 523, A48 (2010).
Teuben, P. The stellar dynamics toolbox NEMO. In ASP Conf. Ser. 77, Astronomical Data Analysis Software and Systems IV (eds Shaw, R. A., Payne, H. E. & Hayes, J. J. E.) 398–401 (ASP, 1995).
Dehnen, W. & Binney, J. Mass models of the Milky Way. Mon. Not. R. Astron. Soc. 294, 429–438 (1998).
Gravity Collaboration Detection of the gravitational redshift in the orbit of the star S2 near the Galactic Centre massive black hole. Astron. Astrophys. 615, L15 (2018).
Karim, M. T. & Mamajek, E. E. Revised geometric estimates of the north Galactic pole and the Sun’s height above the Galactic mid-plane. Mon. Not. R. Astron. Soc. 465, 472–481 (2017).
Schönrich, R., Binney, J. & Dehnen, W. Local kinematics and the local standard of rest. Mon. Not. R. Astron. Soc. 403, 1829–1833 (2010).
Varri, A. L. & Bertin, G. Self-consistent models of quasi-relaxed rotating stellar systems. Astron. Astrophys. 540, A94 (2012).
Bianchini, P. et al. The internal rotation of globular clusters revealed by Gaia DR2. Mon. Not. R. Astron. Soc. 481, 2125–2139 (2018).
Dehnen, W. A hierarchical O(N) force calculation algorithm. J. Comput. Phys. 179, 27–42 (2002).
Gratton, R. G., Johnson, C. I., Lucatello, S., D’Orazi, V. & Pilachowski, C. Multiple populations in Omega Centauri: a cluster analysis of spectroscopic data. Astron. Astrophys. 534, A72 (2011).
This work has made use of data from the European Space Agency (ESA) 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. We thank the staff of the CFHT for taking the ESPaDOnS data used here, and for their continued support throughout the project. Based on observations obtained at the CFHT, which is operated by the National Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientique of France and the University of Hawaii. This work has been published under the framework of the IdEx Unistra and benefits from a funding from the state managed by the French National Research Agency as part of the investments for the future programme. PyRAF is a product of the Space Telescope Science Institute, which is operated by AURA for NASA. R.A.I. and N.M. gratefully acknowledge support from a ‘Programme National Cosmologie et Galaxies’ grant.
The authors declare no competing interests.
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Ibata, R.A., Bellazzini, M., Malhan, K. et al. Identification of the long stellar stream of the prototypical massive globular cluster ω Centauri. Nat Astron 3, 667–672 (2019). https://doi.org/10.1038/s41550-019-0751-x
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