Gaps and length asymmetry in the stellar stream Palomar 5 as effects of Galactic bar rotation

Abstract

The stellar stream emerging from the globular cluster Palomar 5 (Pal 5) is one of the few Galactic streams that is clearly associated with its progenitor system. Recent optical photometric data show that Pal 5’s leading arm appears truncated compared with the trailing arm, which is not expected from previous simulations. We demonstrate that inclusion of the rotating Galactic bar in the dynamical modelling of Pal 5 can reproduce the truncation. As the bar sweeps by, stream stars experience differences in net torques near their orbital pericentres. This leads to the formation of discontinuities in the energy distribution of stream members that in turn become apparent as ever-widening gaps in the stream’s spatial density. We conclude that only streams orbiting far from the Galactic Centre or streams on retrograde orbits can be used to unambiguously constrain dark matter subhalo interactions. Additionally, we expect that the Pal 5 leading-arm debris should reappear south of the density truncation.

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Fig. 1: The truncation in the leading arm of Pal 5 can be reproduced by introducing a prograde Galactic bar.
Fig. 2: Observables of the Pal 5 stream evolved in a potential with a prograde Galactic bar.
Fig. 3: Gap formation and evolution in a Pal 5-like stellar stream due to the spinning Galactic bar.
Fig. 4: Variations in the torque from the Galactic bar due to stream inclination (i) and pericentric distance (R p).
Fig. 5: The Galactic potential.

References

  1. 1.

    Odenkirchen, M. et al. Detection of massive tidal tails around the globular cluster Palomar 5 with Sloan Digital Sky Survey commissioning data. Astrophys. J. Lett. 548, L165–L169 (2001).

    ADS  Article  Google Scholar 

  2. 2.

    York, D. G. et al. The Sloan Digital Sky Survey: technical summary. Astron. J. 120, 1579–1587 (2000).

    ADS  Article  Google Scholar 

  3. 3.

    Odenkirchen, M., Grebel, E. K., Dehnen, W., Rix, H.-W. & Cudworth, K. M. Kinematic study of the disrupting globular cluster Palomar 5 using VLT spectra. Astron. J. 124, 1497–1510 (2002).

    ADS  Article  Google Scholar 

  4. 4.

    Fritz, T. K. & Kallivayalil, N. The proper motion of Palomar 5. Astrophys. J. 811, 123 (2015).

    ADS  Article  Google Scholar 

  5. 5.

    Dotter, A., Sarajedini, A. & Anderson, J. Globular clusters in the outer galactic halo: new Hubble Space Telescope/Advanced Camera for surveys imaging of six globular clusters and the galactic globular cluster age-metallicity relation. Astrophys. J. 738, 74 (2011).

    ADS  Article  Google Scholar 

  6. 6.

    Odenkirchen, M., Grebel, E. K., Kayser, A., Rix, H.-W. & Dehnen, W. Kinematics of the tidal debris of the globular cluster Palomar 5. Astron. J. 137, 3378–3387 (2009).

    ADS  Article  Google Scholar 

  7. 7.

    Kuzma, P. B., Da Costa, G. S., Keller, S. C. & Maunder, E. Palomar 5 and its tidal tails: a search for new members in the tidal stream. Mon. Not. R. Astron. Soc. 446, 3297–3309 (2015).

    ADS  Article  Google Scholar 

  8. 8.

    Küpper, A. H. W. et al. Globular cluster streams as galactic high-precision scales — the poster child Palomar 5. Astrophys. J. 803, 80 (2015).

    ADS  Article  Google Scholar 

  9. 9.

    Bovy, J., Bahmanyar, A., Fritz, T. K. & Kallivayalil, N. The shape of the inner Milky Way halo from observations of the Pal 5 and GD-1 stellar streams. Astrophys. J. 833, 31 (2016).

    ADS  Article  Google Scholar 

  10. 10.

    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).

    ADS  Article  Google Scholar 

  11. 11.

    Yoon, J. H., Johnston, K. V. & Hogg, D. W. Clumpy streams from clumpy halos: detecting missing satellites with cold stellar structures. Astrophys. J. 731, 58 (2011).

    ADS  Article  Google Scholar 

  12. 12.

    Carlberg, R. G., Grillmair, C. J. & Hetherington, N. The Pal 5 star stream gaps. Astrophys. J. 760, 75 (2012).

    ADS  Article  Google Scholar 

  13. 13.

    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, 60–85 (2017).

  14. 14.

    Bovy, J., Erkal, D. & Sanders, J. L. Linear perturbation theory for tidal streams and the small-scale CDM power spectrum. Mon. Not. R. Astron. Soc. 466, 628–668 (2017).

    ADS  Article  Google Scholar 

  15. 15.

    Thomas, G. F., Ibata, R., Famaey, B., Martin, N. F. & Lewis, G. F. Exploring the reality of density substructures in the Palomar 5 stellar stream. Mon. Not. R. Astron. Soc. 460, 2711–2719 (2016).

    ADS  Article  Google Scholar 

  16. 16.

    Dehnen, W., Odenkirchen, M., Grebel, E. K. & Rix, H.-W. Modeling the disruption of the globular cluster Palomar 5 by galactic tides. Astron. J. 127, 2753–2770 (2004).

    ADS  Article  Google Scholar 

  17. 17.

    Pearson, S., Küpper, A. H. W., Johnston, K. V. & Price-Whelan, A. M. Tidal stream morphology as an indicator of dark matter halo geometry: the case of Palomar 5. Astrophys. J. 799, 28 (2015).

    ADS  Article  Google Scholar 

  18. 18.

    Chambers, K. C. et al. The Pan-STARRS1 surveys. Preprint at https://arxiv.org/abs/1612.05560 (2016).

  19. 19.

    Bernard, E. J. et al. A synoptic map of halo substructures from the Pan-STARRS1 3π survey. Mon. Not. R. Astron. Soc. 463, 1759–1768 (2016).

  20. 20.

    Hattori, K., Erkal, D. & Sanders, J. L. Shepherding tidal debris with the Galactic bar: the Ophiuchus stream. Mon. Not. R. Astron. Soc. 460, 497–512 (2016).

    ADS  Article  Google Scholar 

  21. 21.

    Price-Whelan, A. M., Sesar, B., Johnston, K. V. & Rix, H.-W. Spending too much time at the Galactic bar: chaotic fanning of the Ophiuchus stream. Astrophys. J. 824, 104 (2016).

    ADS  Article  Google Scholar 

  22. 22.

    Wegg, C. & Gerhard, O. Mapping the three-dimensional density of the Galactic bulge with VVV red clump stars. Mon. Not. R. Astron. Soc. 435, 1874–1887 (2013).

    ADS  Article  Google Scholar 

  23. 23.

    Gerhard, O. Pattern speeds in the Milky Way. Memorie della Societa Astronomica Italiana Supplementi 18, 185–188 (2011).

    ADS  Google Scholar 

  24. 24.

    Balbinot, E. & Gieles, M. The devil is in the tails: the role of globular cluster mass evolution on stream properties. Preprint at https://arxiv.org/abs/1702.02543 (2017).

  25. 25.

    Englmaier, P. & Gerhard, O. Gas dynamics and large-scale morphology of the Milky Way galaxy. Mon. Not. R. Astron. Soc. 304, 512–534 (1999).

    ADS  Article  Google Scholar 

  26. 26.

    Dehnen, W. The effect of the outer Lindblad resonance of the Galactic bar on the local stellar velocity distribution. Astron. J. 119, 800–812 (2000).

    ADS  Article  Google Scholar 

  27. 27.

    Gaia Collaboration. et al. The Gaia mission. Astron. Astrophys. 595, A1 (2016).

    Article  Google Scholar 

  28. 28.

    Johnston, K. V. A prescription for building the Milky Way’s halo from disrupted satellites. Astrophys. J. 495, 297–308 (1998).

    ADS  Article  Google Scholar 

  29. 29.

    Helmi, A. & White, S. D. M. Building up the stellar halo of the Galaxy. Mon. Not. R. Astron. Soc. 307, 495–517 (1999).

    ADS  Article  Google Scholar 

  30. 30.

    Johnston, K. V., Sackett, P. D. & Bullock, J. S. Interpreting debris from satellite disruption in external galaxies. Astrophys. J. 557, 137–149 (2001).

    ADS  Article  Google Scholar 

  31. 31.

    Binney, J. & Tremaine, S. Galactic Dynamics 2nd edn (Princeton Univ. Press, 2008).

  32. 32.

    Hendel, D. & Johnston, K. V. Tidal debris morphology and the orbits of satellite galaxies. Mon. Not. R. Astron. Soc. 454, 2472–2485 (2015).

    ADS  Article  Google Scholar 

  33. 33.

    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).

    ADS  Article  Google Scholar 

  34. 34.

    Diemand, J. et al. Clumps and streams in the local dark matter distribution. Nature 454, 735–738 (2008).

    ADS  Article  Google Scholar 

  35. 35.

    Klypin, A., Kravtsov, A. V., Valenzuela, O. & Prada, F. Where are the missing Galactic satellites? Astrophys. J. 522, 82–92 (1999).

    ADS  Article  Google Scholar 

  36. 36.

    Hui, L., Ostriker, J. P., Tremaine, S. & Witten, E. On the hypothesis that cosmological dark matter is composed of ultra-light bosons. Phys. Rev. Lett. 95, 043541 (2017).

    ADS  Google Scholar 

  37. 37.

    D’Onghia, E., Springel, V., Hernquist, L. & Keres, D. Substructure depletion in the Milky Way halo by the disk. Astrophys. J. 709, 1138–1147 (2010).

    ADS  Article  Google Scholar 

  38. 38.

    Garrison-Kimmel, S. et al. Not so lumpy after all: modeling the depletion of dark matter subhalos by Milky Way-like galaxies. Preprint at https://arxiv.org/abs/1701.03792 (2017).

  39. 39.

    Errani, R., Peñarrubia, J., Laporte, C. F. P. & Gómez, F. A. The effect of a disc on the population of cuspy and cored dark matter substructures in Milky Way-like galaxies. Mon. Not. R. Astron. Soc. 465, L59–L63 (2017).

    ADS  Article  Google Scholar 

  40. 40.

    Amorisco, N. C., Gómez, F. A., Vegetti, S. & White, S. D. M. Gaps in globular cluster streams: giant molecular clouds can cause them too. Mon. Not. R. Astron. Soc. 463, L17–L21 (2016).

    ADS  Article  Google Scholar 

  41. 41.

    Sanders, J. L., Bovy, J. & Erkal, D. Dynamics of stream-subhalo interactions. Mon. Not. R. Astron. Soc. 457, 3817–3835 (2016).

    ADS  Article  Google Scholar 

  42. 42.

    Sandford, E., Küpper, A. H. W., Johnston, K. V. & Diemand, J. Quantifying tidal stream disruption in a simulated Milky Way. Mon. Not. R. Astron. Soc. 470, 522–538 (2017).

  43. 43.

    Erkal, D. & Belokurov, V. Properties of dark subhaloes from gaps in tidal streams. Mon. Not. R. Astron. Soc. 454, 3542–3558 (2015).

    ADS  Article  Google Scholar 

  44. 44.

    Miyamoto, M. & Nagai, R. Three-dimensional models for the distribution of mass in galaxies. Pub. Astron. Soc. Jpn 27, 533–543 (1975).

    ADS  Google Scholar 

  45. 45.

    Navarro, J. F., Frenk, C. S. & White, S. D. M. The structure of cold dark matter halos. Astrophys. J. 462, 563–575 (1996).

    ADS  Article  Google Scholar 

  46. 46.

    Wang, Y., Zhao, H., Mao, S. & Rich, R. M. A new model for the Milky Way bar. Mon. Not. R. Astron. Soc. 427, 1429–1440 (2012).

    ADS  Article  Google Scholar 

  47. 47.

    Dwek, E. et al. Morphology, near-infrared luminosity, and mass of the Galactic bulge from COBE DIRBE observations. Astrophys. J. 445, 716–730 (1995).

    ADS  Article  Google Scholar 

  48. 48.

    Hernquist, L. & Ostriker, J. P. A self-consistent field method for galactic dynamics. Astrophys. J. 386, 375–397 (1992).

    ADS  Article  Google Scholar 

  49. 49.

    Portail, M., Wegg, C., Gerhard, O. & Martinez-Valpuesta, I. Made-to-measure models of the Galactic box/peanut bulge: stellar and total mass in the bulge region. Mon. Not. R. Astron. Soc. 448, 713–731 (2015).

    ADS  Article  Google Scholar 

  50. 50.

    Bovy, J. galpy: a python library for Galactic dynamics. Astrophys. J. Supp. 216, 29–56 (2015).

    ADS  Article  Google Scholar 

  51. 51.

    Bovy, J. et al. The Milky Way’s circular-velocity curve between 4 and 14 kpc from APOGEE data. Astrophys. J. 759, 131 (2012).

    ADS  Article  Google Scholar 

  52. 52.

    Xue, X. X. et al. The Milky Way’s circular velocity curve to 60 kpc and an estimate of the dark matter halo mass from the kinematics of 2400 SDSS blue horizontal-branch stars. Astrophys. J. 684, 1143–1158 (2008).

    ADS  Article  Google Scholar 

  53. 53.

    Deason, A. J., Belokurov, V., Evans, N. W. & An, J. Broken degeneracies: the rotation curve and velocity anisotropy of the Milky Way halo. Mon. Not. R. Astron. Soc. 424, L44–L48 (2012).

    ADS  Article  Google Scholar 

  54. 54.

    Prince, P. & Dormand, J. High order embedded Runge-Kutta formulae. J. Comput. Appl. Math. 7, 67–75 (1981). http://www.sciencedirect.com/science/article/pii/0771050X81900103

    MathSciNet  Article  MATH  Google Scholar 

  55. 55.

    Hairer, E., Nørsett, S. P. & Wanner, G. Solving Ordinary Differential Equations. I. Nonstiff Problems 2nd edn (Springer-Verlag, Berlin, 2000).

    Google Scholar 

  56. 56.

    Price-Whelan, A., Sipocz, B. & Oh, S. adrn/gala: version 0.1.3 (2017); https://doi.org/10.5281/zenodo.321907.

  57. 57.

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

    Article  Google Scholar 

  58. 58.

    Schönrich, R. Galactic rotation and solar motion from stellar kinematics. Mon. Not. R. Astron. Soc. 427, 274–287 (2012).

    ADS  Article  Google Scholar 

  59. 59.

    Schönrich, R., Binney, J. & Dehnen, W. Local kinematics and the local standard of rest. Mon. Not. R. Astron. Soc. 403, 1829–1833 (2010).

    ADS  Article  Google Scholar 

  60. 60.

    Fardal, M. A., Huang, S. & Weinberg, M. D. Generation of mock tidal streams. Mon. Not. R. Astron. Soc. 452, 301–319 (2015).

    ADS  Article  Google Scholar 

  61. 61.

    Gibbons, S. L. J., Belokurov, V. & Evans, N. W. ‘Skinny Milky Way please’, says Sagittarius. Mon. Not. R. Astron. Soc. 445, 3788–3802 (2014).

    ADS  Article  Google Scholar 

  62. 62.

    Choi, J.-H., Weinberg, M. D. & Katz, N. The dynamics of tidal tails from massive satellites. Mon. Not. R. Astron. Soc. 381, 987–1000 (2007).

    ADS  Article  Google Scholar 

  63. 63.

    Bovy, J. Dynamical modeling of tidal streams. Astrophys. J. 795, 95 (2014).

    ADS  Article  Google Scholar 

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Acknowledgements

We acknowledge A. Brown, the Gaia Project Scientist Support Team and the Gaia Data Processing and Analysis Consortium (DPAC) for making the PyGaia package open source. We thank the Flatiron Institute Center for Computational Astrophysics for providing the space to carry out this project. S.P. thanks J. Chanamé and E. Bernard for insightful discussions. K.V.J. and S.P. acknowledge support from National Science Foundation grant AST-1614743.

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S.P. led the modelling, analysis, figure production and writing of the paper. A.M.P.-W. assisted with the modelling, writing and with producing figures. All authors discussed the results, their interpretation and the presentation of the paper.

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Correspondence to Sarah Pearson.

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Pearson, S., Price-Whelan, A.M. & Johnston, K.V. Gaps and length asymmetry in the stellar stream Palomar 5 as effects of Galactic bar rotation. Nat Astron 1, 633–639 (2017). https://doi.org/10.1038/s41550-017-0220-3

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