4-8 October 2015
Hans Harnack Haus
Europe/Berlin timezone
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Contribution Contributed Talk

Hans Harnack Haus -
FROM DENSE CORES TO PROTOSTARS 2

In-situ particle (re-)acceleration and induced ionisation in protostars

Speakers

  • Dr. Marco PADOVANI

Primary authors

Co-authors

Content

It is largely accepted that Galactic cosmic rays, which pervade the interstellar medium, originate by means of shock waves in supernova remnants [1]. Cosmic rays activate the rich chemistry that is observed in a molecular cloud [2] and they also regulate its collapse timescale [3], determining the efficiency of star and planet formation, but they cannot penetrate up to the densest part of a molecular cloud, where the formation of stars is expected, because of energy loss processes and magnetic field deflections [4,5,6,7]. Recently, observations towards young protostellar systems showed a surprisingly high value of the ionisation rate [8,9], the main indicator of the presence of cosmic rays in molecular cloud. Synchrotron emission, the typical feature of relativistic electrons, has been also detected towards the bow shock of a T Tauri star [10]. Nevertheless, the origin of these signatures peculiar to accelerated particles is still puzzling. Here we show that particle acceleration can be driven by shock waves occurring in protostars. We found that shocks in protostellar jets can be strong accelerators of protons, which can be easily boosted up to relativistic energies. Another possible efficient acceleration site is located at the protostellar surface, where shocks caused by impacting material during the collapse phase are strong enough to accelerate protons. While electron acceleration is not efficient because of Coulomb losses, secondary electrons created during the ionisation process can reach relativistic energies. Our results demonstrate the possibility of accelerating particles during the early phase of a proto-Solar-like system and can be used as the argument to support available observations. The existence of an internal source of energetic particles can have a strong and unforeseen impact over the stellar and planet formation process as well as on the formation of pre-biotic molecules.

References:

  1. Drury, L. O'C. 1983, RPPh, 46, 973
  2. Duley, W. W. & Williams, D. A. 1984, Interstellar Chemistry, Academic Press
  3. Balbus, S. A. & Hawley, J. F. 1991, ApJ, 376, 214
  4. Padovani, M., Galli, D. & Glassgold, A. E. 2009, A&A, 501, 619
  5. Padovani, M. & Galli, D. 2011, A&A, 530, 109
  6. Padovani, M., Hennebelle, P. & Galli, D. 2013, A&A, 560, 114
  7. Cleeves, L. I., Adams, F. C. & Bergin, E. A. 2013, ApJ, 772, 5
  8. Ceccarelli, C., Dominik, C., López-Sepulcre, A., Kama, M., Padovani, M. et al. 2014, ApJ, 790, 1
  9. Podio, L., Lefloch, B., Ceccarelli, C., Codella, C. & Bachiller, 2014, A&A, 565, 64
  10. Ainsworth, R. E., Scaife, A. M. M., Ray, T. P., Taylor, A. M., Green, D. A. et al. 2014, ApJ, 792, 18