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Discovery of molecular hydrogen in a high-velocity cloud of the Galactic halo

Abstract

The Milky Way's halo contains clouds of neutral hydrogen with high radial velocities which do not follow the general rotational motion of the Galaxy1. Few distances to these high-velocity clouds are known2,3, so even gross properties such as total mass are hard to determine. As a consequence, there is no generally accepted theory regarding their origin. One idea4,5 is that they result from gas that has cooled after being ejected from the Galaxy through fountain-like flows powered by supernovae; another is that they are composed of gas, poor in heavy elements, which is falling onto the disk of the Milky Way from intergalactic space6,7. The presence of molecular hydrogen, whose formation generally requires the presence of dust (and therefore gas, enriched in heavy elements), could help to distinguish between these possibilities. Here we report the discovery of molecular hydrogen absorption in a high-velocity cloud along the line of sight to the Large Magellanic Cloud. We also derive for the same cloud an iron abundance which is half of the solar value. From these data, we conclude that gas in this cloud originated in the disk of the Milky Way.

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Figure 1: The spectral region between 1,006 and 1,012 Å in the ORFEUS spectrum of HD269546.
Figure 2: Comparison between the H2 absorption profile (top panel) and the H I emission profile (bottom panel) for the HVC gas in the direction of HD269546.
Figure 3: Map of the peak intensities for neutral hydrogen emission.

References

  1. 1

    Wakker,B. Distribution and origin of high-velocity clouds. Astron. Astrophys. 250, 499–508 (1991).

    ADS  Google Scholar 

  2. 2

    Wakker,B. P. & van Woerden,H. High-velocity clouds. Annu. Rev. Astron. Astrophys. 35, 217–266 (1997).

    ADS  CAS  Article  Google Scholar 

  3. 3

    van Woerden,H. et al. A confirmed location in the Galactic halo for the high-velocity cloud ‘chain A’. Nature 400, 138–141 (1999).

    ADS  CAS  Article  Google Scholar 

  4. 4

    Shapiro,P. R. & Field,G. B. Consequences of a new hot component of the interstellar medium. Astrophys. J. 205, 762–765 (1976).

    ADS  CAS  Article  Google Scholar 

  5. 5

    Bregman,J. N. The galactic fountain of high-velocity clouds. Astrophys. J. 236, 577–591 (1980).

    ADS  CAS  Article  Google Scholar 

  6. 6

    Oort,J. H. The formation of galaxies and the origin of the high-velocity hydrogen. Astron. Astrophys. 7, 381–404 (1970).

    ADS  Google Scholar 

  7. 7

    Blitz,L. et al. High-velocity clouds: building blocks of the Local Group. Astrophys. J. 514, 818–843 (1999).

    ADS  CAS  Article  Google Scholar 

  8. 8

    Wakker,B. P., Murphy,E. M., van Woerden, H. & Dame,T. M. A sensitive search for molecular gas in high-velocity clouds. Astrophys. J. 488, 216–223 (1997).

    ADS  CAS  Article  Google Scholar 

  9. 9

    Akeson,R. L. & Blitz,L. A search for hydrogen and molecular gas absorption in high-velocity clouds. Astrophys. J. 523, 163–170 (1999).

    ADS  CAS  Article  Google Scholar 

  10. 10

    Barnstedt,J. et al. The ORFEUS II Echelle Spectrometer: Instrument description, performance and data reduction. Astron. Astrophys. Suppl. 134, 561–567 (1999).

    ADS  Article  Google Scholar 

  11. 11

    Savage,B. D. & de Boer,K. S. Ultraviolet absorption by interstellar gas at large distances from the Galactic plane. Astrophys. J. 243, 460–484 (1981).

    ADS  CAS  Article  Google Scholar 

  12. 12

    Bomans,D. J., de Boer,K. S., Koornneef,J. & Grebel,E. K. CIV absorption from hot gas inside the supergiant shell LMC4 observed with HST and IUE. Astron. Astrophys. 313, 101–112 (1996).

    ADS  CAS  Google Scholar 

  13. 13

    de Boer,K. S., Morras,R. & Bajaja,E. The location of intermediate- and high-velocity gas in the general direction of the Large Magellanic Cloud. Astron. Astrophys. 233, 523–526 (1990).

    ADS  CAS  Google Scholar 

  14. 14

    McGee,R. X. & Newton,L. M. Neutral hydrogen in the Galactic halo. Proc. Astron. Soc. Aust. 6, 358–385 (1986).

    ADS  CAS  Article  Google Scholar 

  15. 15

    Savage,B. D., Bohlin,R. C., Drake,J. F. & Budich,W. A survey of interstellar molecular hydrogen. Astrophys. J. 216, 291–307 (1977).

    ADS  CAS  Article  Google Scholar 

  16. 16

    Spitzer,L. & Zweibel,E. G. On the theory of H2 rotational excitation. Astrophys. J. 191, L127–L130 (1974).

    ADS  CAS  Article  Google Scholar 

  17. 17

    Burton,M. G., Hollenbach,D. J. & Thielens,A. G. G. M. Mid-infrared rotational line emission from interstellar molecular hydrogen. Astrophys. J. 399, 563–572 (1992).

    ADS  CAS  Article  Google Scholar 

  18. 18

    Jura,M. A. Interstellar clouds containing optically thin H2. Astrophys. J. 197, 575–580 (1975).

    ADS  CAS  Article  Google Scholar 

  19. 19

    Putman,M. E. & Gibson,B. K. First results from the Parkes Multibeam High-velocity Cloud Survey. Proc. Astron. Soc. Aust. 16, 70–76 (1999).

    ADS  CAS  Article  Google Scholar 

  20. 20

    Grewing,M. & Schulz-Lüpertz,E. Ionisationsstrukturen im galaktischen Halogas. Mitt. Astron. Gesellsch. 52, 79–83 (1981).

    ADS  Google Scholar 

  21. 21

    de Boer,K. S., Jura,M. A. & Schull,J. M. Diffuse and dark clouds in the interstellar medium. Scientific Accomplishments of the IUE (ed. Kondo, Y.) 485–515 (Reidel, Dordrecht, 1987).

  22. 22

    Pei,Y. C. & Fall,S. M. Cosmic chemical evolution. Astrophys. J. 454, 69–76 (1995).

    ADS  CAS  Article  Google Scholar 

  23. 23

    Morton,D. C. & Dinerstein,H. L. Interstellar molecular hydrogen toward Zeta Puppis. Astrophys. J. 204, 1–11 (1975).

    ADS  Article  Google Scholar 

  24. 24

    Field,G. B., Somerville,W. B. & Dressler,K. Hydrogen molecules in Astronomy. Annu. Rev. Astron. Astrophys. 4, 207–244 (1966).

    ADS  CAS  Article  Google Scholar 

  25. 25

    Nichols, J. S. & Linsky,J. L. The Final Archive and recalibration of the International Ultraviolet Explorer (IUE) satellite. Astron. J. 111, 517–536 (1996).

    ADS  Article  Google Scholar 

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Acknowledgements

We thank M. Putman and C. Brüns for providing part of the HIPASS data.

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Correspondence to P. Richter.

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Richter, P., de Boer, K., Widmann, H. et al. Discovery of molecular hydrogen in a high-velocity cloud of the Galactic halo. Nature 402, 386–387 (1999). https://doi.org/10.1038/46492

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