Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

The recurrent impact of the Sagittarius dwarf on the star formation history of the Milky Way

Abstract

Satellites orbiting disk galaxies can induce phase space features such as spirality, vertical heating and phase-mixing in their disks. Such features have also been observed in our own Galaxy, but the complexity of the Milky Way disk has only recently been fully mapped by Gaia Data Release 2 (DR2) data. This complex behaviour is mainly ascribed to repeated perturbations induced by the Sagittarius dwarf galaxy (Sgr) along its orbit, pointing to this satellite as the main dynamical architect of the Milky Way disk. Here, we model Gaia DR2-observed colour–magnitude diagrams to obtain a detailed star formation history of the ~2 kpc bubble around the Sun. It reveals three conspicuous and narrow episodes of enhanced star formation that we can precisely date as having occurred 5.7, 1.9 and 1.0 Gyr ago. The timing of these episodes coincides with proposed Sgr pericentre passages according to (1) orbit simulations, (2) phase space features in the Galactic disk and (3) Sgr stellar content. These findings most probably suggest that Sgr has also been an important actor in the build-up of the stellar mass of the Milky Way disk, with the perturbations from Sgr repeatedly triggering major episodes of star formation.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: CMD of the ~ 2-kpc bubble around the Sun.
Fig. 2: SFH representative of the ~2-kpc-radius bubble around the Sun.
Fig. 3: Testing the robustness of the SFH recovery with mock stellar populations.
Fig. 4: SFH in the ~2-kpc-radius bubble around the Sun distinguishing between the thin and thick disks.

Similar content being viewed by others

Data availability

All data analysed in this paper are publicly available from the Gaia DR2 archive (http://gea.esac.esa.int/archive/). The datasets containing information not available in public catalogues that is necessary to reproduce this work and the corresponding figures are available as Supplementary Data 1. An explanatory README file is included. Supplementary Data 1 consists of the following files: (1) For Figs. 1 and 2, two examples of randomly selected samples of ~250,000 stars (with different extinction coefficients), together with the solution from the THESTORM code. This includes two tables directly retrieved from the Gaia archive as described in the Methods, supplemented by extinction information on a star-by-star basis. (2) For Fig. 3, six mock population CMDs together with the outputs from THESTORM. (3) Examples of randomly selected samples of 250,000 stars for thin and thick disk stars, together with the solutions from the THESTORM code (for Fig. 4). Other data not included in the above-mentioned link are available from the corresponding author on reasonable request.

Code availability

The code used to interpolate the three-dimensional extinction maps63 can be retrieved from https://github.com/edober/dust_maps_3d.

References

  1. Gaia Collaboration et al. Gaia Data Release 2: summary of the contents and survey properties. Astron. Astrophys. 616, A1 (2018).

    Google Scholar 

  2. Gallart, C., Zoccali, M. & Aparicio, A. The adequacy of stellar evolution models for the interpretation of the color-magnitude diagrams of resolved stellar populations. Annu. Rev. Astron. Astrophys. 43, 387–434 (2005).

    ADS  Google Scholar 

  3. Mor, R., Robin, A. C., Figueras, F., Roca-Fàbrega, S. & Luri, X. Gaia DR2 reveals a star formation burst in the disc 2-3 Gyr ago. Astron. Astrophys. 624, L1 (2019).

    ADS  Google Scholar 

  4. Heavens, A., Panter, B., Jimenez, R. & Dunlop, J. The star-formation history of the Universe from the stellar populations of nearby galaxies. Nature 428, 625–627 (2004).

    ADS  Google Scholar 

  5. Perryman, M. A. C. et al. The HIPPARCOS Catalogue. Astron. Astrophys. 323, L49–L52 (1997).

    ADS  Google Scholar 

  6. Bertelli, G. & Nasi, E. Star formation history in the solar vicinity. Astron. J. 121, 1013–1023 (2001).

    ADS  Google Scholar 

  7. Vergely, J.-L., Köppen, J., Egret, D. & Bienaymé, O. An inverse method to interpret colour-magnitude diagrams. Astron. Astrophys. 390, 917–929 (2002).

    ADS  Google Scholar 

  8. Cignoni, M., Degl’Innocenti, S., Prada Moroni, P. G. & Shore, S. N. Recovering the star formation rate in the solar neighborhood. Astron. Astrophys. 459, 783–796 (2006).

    ADS  Google Scholar 

  9. Haywood, M. et al. Phylogeny of the Milky Way’s inner disk and bulge populations: implications for gas accretion, (the lack of) inside-out thick disk formation, and quenching. Astron. Astrophys. 618, A78 (2018).

    Google Scholar 

  10. Bernard, E. J. in IAU Symposium 334: Rediscovering Our Galaxy (eds Chiappini, C. et al.) 158–161 (IAU, 2018).

  11. Feltzing, S., Holmberg, J. & Hurley, J. R. The solar neighbourhood age-metallicity relation—does it exist? Astron. Astrophys. 377, 911–924 (2001).

    ADS  Google Scholar 

  12. Bergemann, M. et al. The Gaia-ESO Survey: radial metallicity gradients and age-metallicity relation of stars in the Milky Way disk. Astron. Astrophys. 565, A89 (2014).

    Google Scholar 

  13. Hayden, M. R. et al. Chemical cartography with APOGEE: metallicity distribution functions and the chemical structure of the Milky Way Disk. Astrophys. J. 808, 132 (2015).

    ADS  Google Scholar 

  14. Gaia Collaboration et al. Gaia Data Release 2: mapping the Milky Way disc kinematics. Astron. Astrophys. 616, A11 (2018).

    Google Scholar 

  15. Gaia Collaboration et al. Gaia Data Release 2: observational Hertzsprung–Russell diagrams. Astron. Astrophys. 616, A10 (2018).

    Google Scholar 

  16. Kennicutt, R. C. Jr., Keel, W. C., van der Hulst, J. M., Hummel, E. & Roettiger, K. A. The effects of interactions on spiral galaxies. II: disk star-formation rates. Astron. J. 93, 1011–1023 (1987).

    ADS  Google Scholar 

  17. Tissera, P. B., Domíguez-Tenreiro, R., Scannapieco, C. & Sáiz, A. Double starbursts triggered by mergers in hierarchical clustering scenarios. Mon. Not. R. Astron. Soc. 333, 327–338 (2002).

    ADS  Google Scholar 

  18. Ellison, S. L., Mendel, J. T., Patton, D. R. & Scudder, J. M. Galaxy pairs in the Sloan Digital Sky Survey–VIII. The observational properties of post-merger galaxies. Mon. Not. R. Astron. Soc. 435, 3627–3638 (2013).

    ADS  Google Scholar 

  19. Tinsley, B. M. & Larson, R. B. Stellar population explosions in proto-elliptical galaxies. Mon. Not. R. Astron. Soc. 186, 503–517 (1979).

    ADS  Google Scholar 

  20. Freeman, K. & Bland-Hawthorn, J. The new galaxy: signatures of its formation. Annu. Rev. Astron. Astrophys. 40, 487–537 (2002).

    ADS  Google Scholar 

  21. Meza, A., Navarro, J. F., Abadi, M. G. & Steinmetz, M. Accretion relics in the solar neighbourhood: debris from ω Cen’s parent galaxy. Mon. Not. R. Astron. Soc. 359, 93–103 (2005).

    ADS  Google Scholar 

  22. Gallart, C. et al. Uncovering the birth of the Milky Way through accurate stellar ages with Gaia. Nat. Astron 3, 932–939 (2019).

    ADS  Google Scholar 

  23. Naab, T. & Ostriker, J. P. Theoretical challenges in galaxy formation. Annu. Rev. Astron. Astrophys. 55, 59–109 (2017).

    ADS  Google Scholar 

  24. Ibata, R. A., Gilmore, G. & Irwin, M. J. A dwarf satellite galaxy in Sagittarius. Nature 370, 194–196 (1994).

    ADS  Google Scholar 

  25. Belokurov, V. et al. The field of streams: Sagittarius and its siblings. Astrophys. J. 642, L137–L140 (2006).

    ADS  Google Scholar 

  26. 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).

    ADS  Google Scholar 

  27. Purcell, C. W., Bullock, J. S., Tollerud, E. J., Rocha, M. & Chakrabarti, S. The Sagittarius impact as an architect of spirality and outer rings in the Milky Way. Nature 477, 301–303 (2011).

    ADS  Google Scholar 

  28. Laporte, C. F. P., Johnston, K. V., Gómez, F. A., Garavito-Camargo, N. & Besla, G. The influence of Sagittarius and the Large Magellanic Cloud on the stellar disc of the Milky Way Galaxy. Mon. Not. R. Astron. Soc. 481, 286–306 (2018).

    ADS  Google Scholar 

  29. Eggen, O. J. The motions of the A Stars at the North Galactic Pole. Publ. Astron. Soc. Pac. 81, 741 (1969).

    ADS  Google Scholar 

  30. Siebert, A. et al. Detection of a radial velocity gradient in the extended local disc with RAVE. Mon. Not. R. Astron. Soc. 412, 2026–2032 (2011).

    ADS  Google Scholar 

  31. Williams, M. E. K. et al. The wobbly galaxy: kinematics north and south with RAVE red-clump giants. Mon. Not. R. Astron. Soc. 436, 101–121 (2013).

    ADS  Google Scholar 

  32. Gómez, F. A. et al. Vertical density waves in the Milky Way disc induced by the Sagittarius dwarf galaxy. Mon. Not. R. Astron. Soc. 429, 159–164 (2013).

    ADS  Google Scholar 

  33. Antoja, T. et al. A dynamically young and perturbed Milky Way disk. Nature 561, 360–362 (2018).

    ADS  Google Scholar 

  34. Laporte, C. F. P., Minchev, I., Johnston, K. V. & Gómez, F. A. Footprints of the Sagittarius dwarf galaxy in the Gaia data set. Mon. Not. R. Astron. Soc. 485, 3134–3152 (2019).

    ADS  Google Scholar 

  35. de la Vega, A., Quillen, A. C., Carlin, J. L., Chakrabarti, S. & D’Onghia, E. Phase wrapping of epicyclic perturbations in the Wobbly Galaxy. Mon. Not. R. Astron. Soc. 454, 933–945 (2015).

    ADS  Google Scholar 

  36. Mackereth, J. T. et al. The origin of accreted stellar halo populations in the Milky Way using APOGEE, Gaia, and the EAGLE simulations. Mon. Not. R. Astron. Soc. 482, 3426–3442 (2019).

    ADS  Google Scholar 

  37. de Boer, T. J. L., Belokurov, V. & Koposov, S. The star formation history of the Sagittarius stream. Mon. Not. R. Astron. Soc. 451, 3489–3503 (2015).

    ADS  Google Scholar 

  38. Siegel, M. H. et al. The ACS survey of galactic globular clusters: M54 and Young populations in the sagittarius dwarf spheroidal galaxy. Astrophys. J. 667, L57–L60 (2007).

    ADS  Google Scholar 

  39. Besla, G. et al. Are the Magellanic Clouds on their first passage about the Milky Way? Astrophys. J. 668, 949–967 (2007).

    ADS  Google Scholar 

  40. Laporte, C. F. P., Gómez, F. A., Besla, G., Johnston, K. V. & Garavito-Camargo, N. Response of the Milky Way’s disc to the Large Magellanic Cloud in a first infall scenario. Mon. Not. R. Astron. Soc. 473, 1218–1230 (2018).

    ADS  Google Scholar 

  41. Laporte, C. F. P., Belokurov, V., Koposov, S. E., Smith, M. C. & Hill, V. Chemo-dynamical properties of the Anticenter Stream: a surviving disc fossil from a past satellite interaction. Mon. Not. R. Astron. Soc. 492, L61–L65 (2020).

    ADS  Google Scholar 

  42. McConnachie, A. W. et al. The remnants of galaxy formation from a panoramic survey of the region around M31. Nature 461, 66–69 (2009).

    ADS  Google Scholar 

  43. Bernard, E. J. et al. The star formation history and dust content in the far outer disc of M31. Mon. Not. R. Astron. Soc. 420, 2625–2643 (2012).

    ADS  Google Scholar 

  44. Mihos, J. C. & Hernquist, L. Triggering of starbursts in galaxies by minor mergers. Astrophys. J. 425, L13–L16 (1994).

    ADS  Google Scholar 

  45. Hernquist, L. & Mihos, J. C. Excitation of activity in galaxies by minor mergers. Astrophys. J. 448, 41 (1995).

    ADS  Google Scholar 

  46. Cox, T. J., Jonsson, P., Somerville, R. S., Primack, J. R. & Dekel, A. The effect of galaxy mass ratio on merger-driven starbursts. Mon. Not. R. Astron. Soc. 384, 386–409 (2008).

    ADS  Google Scholar 

  47. Moreno, J. et al. Mapping galaxy encounters in numerical simulations: the spatial extent of induced star formation. Mon. Not. R. Astron. Soc. 448, 1107–1117 (2015).

    ADS  Google Scholar 

  48. Teyssier, R., Chapon, D. & Bournaud, F. The driving mechanism of starbursts in galaxy mergers. Astrophys. J. 720, L149–L154 (2010).

    ADS  Google Scholar 

  49. Chien, L.-H. & Barnes, J. E. Dynamically driven star formation in models of NGC 7252. Mon. Not. R. Astron. Soc. 407, 43–54 (2010).

    ADS  Google Scholar 

  50. Moster, B. P., Macciò, A. V., Somerville, R. S., Naab, T. & Cox, T. J. The effects of a hot gaseous halo in galaxy major mergers. Mon. Not. R. Astron. Soc. 415, 3750–3770 (2011).

    ADS  Google Scholar 

  51. Luri, X. et al. Gaia Data Release 2: using Gaia parallaxes. Astron. Astrophys. 616, A9 (2018).

    Google Scholar 

  52. Lindegren, L. et al. Gaia Data Release 2: the astrometric solution. Astron. Astrophys. 616, A2 (2018).

    Google Scholar 

  53. Stassun, K. G. & Torres, G. Evidence for a systematic offset of -80 μas in the Gaia DR2 Parallaxes. Astrophys. J. 862, 61 (2018).

    ADS  Google Scholar 

  54. Riess, A. G. et al. Milky Way Cepheid standards for measuring cosmic distances and application to Gaia DR2: implications for the Hubble constant. Astrophys. J. 861, 126 (2018).

    ADS  Google Scholar 

  55. Zinn, J. C., Pinsonneault, M. H., Huber, D. & Stello, D. Confirmation of the Gaia DR2 parallax zero-point offset using asteroseismology and spectroscopy in the Kepler field. Astrophys. J. 878, 136 (2019).

    ADS  Google Scholar 

  56. Schönrich, R., McMillan, P. & Eyer, L. Distances and parallax bias in Gaia DR2. Mon. Not. R. Astron. Soc. 487, 3568–3580 (2019).

    ADS  Google Scholar 

  57. Khan, S. et al. New light on the Gaia DR2 parallax zero-point: influence of the asteroseismic approach, in and beyond the Kepler field. Astron. Astrophys. 628, A35 (2019).

    Google Scholar 

  58. Graczyk, D. et al. Testing systematics of Gaia DR2 parallaxes with empirical surface brightness: color relations applied to eclipsing binaries. Astrophys. J. 872, 85 (2019).

    ADS  Google Scholar 

  59. Hall, O. J. et al. Testing asteroseismology with Gaia DR2: hierarchical models of the red clump. Mon. Not. R. Astron. Soc. 486, 3569–3585 (2019).

    ADS  Google Scholar 

  60. Leung, H. W. & Bovy, J. Simultaneous calibration of spectro-photometric distances and the Gaia DR2 parallax zero-point offset with deep learning. Mon. Not. R. Astron. Soc. 489, 2079–2096 (2019).

    ADS  Google Scholar 

  61. Bailer-Jones, C. A. L., Rybizki, J., Fouesneau, M., Mantelet, G. & Andrae, R. Estimating distance from parallaxes. IV: distances to 1.33 billion stars in Gaia Data Release 2. Astron. J. 156, 58 (2018).

    ADS  Google Scholar 

  62. Anders, F. et al. Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18. Astron. Astrophys. 628, A94 (2019).

    Google Scholar 

  63. Lallement, R. et al. Three-dimensional maps of interstellar dust in the Local Arm: using Gaia, 2MASS, and APOGEE-DR14. Astron. Astrophys. 616, A132 (2018).

    Google Scholar 

  64. Casagrande, L. & VandenBerg, D. A. On the use of Gaia magnitudes and new tables of bolometric corrections. Mon. Not. R. Astron. Soc. 479, L102–L107 (2018).

    ADS  Google Scholar 

  65. Cignoni, M. & Tosi, M. Star formation histories of dwarf galaxies from the colour-magnitude diagrams of their resolved stellar populations. Adv. Astron. 2010, 158568 (2010).

    ADS  Google Scholar 

  66. Aparicio, A. & Hidalgo, S. L. IAC-pop: finding the star formation history of resolved galaxies. Astron. J. 138, 558–567 (2009).

    ADS  Google Scholar 

  67. Tolstoy, E., Hill, V. & Tosi, M. Star-formation histories, abundances, and kinematics of dwarf galaxies in the local group. Annu. Rev. Astron. Astrophys. 47, 371–425 (2009).

    ADS  Google Scholar 

  68. Monelli, M. et al. The ACS LCID Project. III. The star formation history of the Cetus dSph galaxy: a post-reionization fossil. Astrophys. J. 720, 1225–1245 (2010).

    ADS  Google Scholar 

  69. Pietrinferni, A., Cassisi, S., Salaris, M. & Castelli, F. A large stellar evolution database for population synthesis studies. I: scaled solar models and isochrones. Astrophys. J. 612, 168–190 (2004).

    ADS  Google Scholar 

  70. Kroupa, P. On the variation of the initial mass function. Mon. Not. R. Astron. Soc. 322, 231–246 (2001).

    ADS  Google Scholar 

  71. Evans, D. W. et al. Gaia Data Release 2: photometric content and validation. Astron. Astrophys. 616, A4 (2018).

    Google Scholar 

  72. Bernard, E. J. et al. The spatially-resolved star formation history of the M31 outer disc. Mon. Not. R. Astron. Soc. 453, L113–L117 (2015).

    ADS  Google Scholar 

  73. Bernard, E. J. et al. Star formation history of the Galactic bulge from deep HST imaging of low reddening windows. Mon. Not. R. Astron. Soc. 477, 3507–3519 (2018).

    ADS  Google Scholar 

  74. Ruiz-Lara, T. et al. Integrated-light analyses vs. colour-magnitude diagrams. II. Leo A: an extremely young dwarf in the Local Group. Astron. Astrophys. 617, A18 (2018).

    Google Scholar 

  75. Hidalgo, S. L. et al. The ACS LCID Project. V. The star formation history of the dwarf galaxy LGS-3: clues to cosmic reionization and feedback. Astrophys. J. 730, 14 (2011).

    ADS  Google Scholar 

  76. Cassisi, S., Potekhin, A. Y., Pietrinferni, A., Catelan, M. & Salaris, M. Updated electron-conduction opacities: the impact on low-mass stellar models. Astrophys. J. 661, 1094–1104 (2007).

    ADS  Google Scholar 

  77. Hidalgo, S. L. et al. The updated BaSTI stellar evolution models and isochrones. I. Solar-scaled calculations. Astrophys. J. 856, 125 (2018).

    ADS  Google Scholar 

  78. Rusakov, V. et al. The bursty star formation history of the Fornax dwarf spheroidal galaxy revealed with the HST. Preprint at https://arxiv.org/abs/2002.09714 (2020).

  79. Hunter, J. D. Matplotlib: a 2d graphics environment. Comput. Sci. Eng. 9, 90–95 (2007).

    Google Scholar 

  80. Astropy Collaboration et al. Astropy: a community Python package for astronomy. Astron. Astrophys. 558, A33 (2013).

    Google Scholar 

  81. Astropy Collaboration et al. The Astropy Project: building an open-science project and status of the v2.0 core package. Astron. J. 156, 123 (2018).

    ADS  Google Scholar 

Download references

Acknowledgements

We thank K. C. Freeman, C. Bailer-Jones, G. Battaglia, M. Beasley, C. Brook, C. Dalla Vecchia, J. Falcón-Barroso, R. Leaman and I. Pérez for useful discussions. T.R.-L. and C.G. acknowledge financial support through grant numbers (AEI/FEDER, UE) AYA2017-89076-P, AYA2016-77237-C3-1-P (RAVET project) and AYA2015-63810-P, as well as from the Ministerio de Ciencia, Innovación y Universidades (MCIU) through the State Budget and the Consejería de Economía, Industria, Comercio y Conocimiento of the Canary Islands Autonomous Community through the Regional Budget (including IAC project, TRACES). T.R.-L. is supported by a MCIU Juan de la Cierva–Formación grant (FJCI-2016-30342). S.C. acknowledges support from Premiale INAF “MITIC” and grant number AYA2013-42781P from the Ministry of Economy and Competitiveness of Spain; he has also been supported by the INFN (Iniziativa specifica TAsP). We used data from the European Space Agency mission Gaia (http://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; see http://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research makes use of Python (version 3.6.7, http://www.python.org); Matplotlib (version 3.0.0)79, a suite of open-source python modules that provide a framework for creating scientific plots; and Astropy (version 3.0.5), a community-developed core Python package for astronomy80,81.

Author information

Authors and Affiliations

Authors

Contributions

The manuscript was written by T.R.-L. and C.G. T.R.-L. and C.G. defined the final samples under analysis and extracted the SFH presented in this work. The software to analyse Gaia DR2 data was written by T.R.-L. and E.J.B. S.C. contributed to the tools used to generate the synthetic CMDs and evolutionary model predictions in the Gaia photometric system. All authors contributed to the interpretation and analysis of the results.

Corresponding author

Correspondence to Tomás Ruiz-Lara.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Astronomy thanks Michele Cignoni and Roger Mor for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Ruiz-Lara, T., Gallart, C., Bernard, E.J. et al. The recurrent impact of the Sagittarius dwarf on the star formation history of the Milky Way. Nat Astron 4, 965–973 (2020). https://doi.org/10.1038/s41550-020-1097-0

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41550-020-1097-0

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing