References

ASTRA Proceedings

ASTRA Proc.

2199-3963

Copernicus Publications

Göttingen, Germany

10.5194/ap-1-23-2014

Cosmic rays as regulators of molecular cloud properties

Padovani

¹ ² ⁴ Hennebelle

³ Galli

Laboratoire de Radioastronomie Millimétrique, UMR 8112 du CNRS, École Normale Supérieure et Observatoire de Paris, 24 rue Lhomond, 75231 Paris cedex 05, France

INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy

CEA, IRFU, SAp, Centre de Saclay, 91191 Gif-Sur-Yvette, France

now at: Laboratoire Univers et Particules de Montpellier, UMR 5299 du CNRS, Université de Montpellier 2, place E. Bataillon, cc072, 34095 Montpellier, France

27 06 2014

1 23 27

2014

This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/

This article is available from https://ap.copernicus.org/articles/1/23/2014/ap-1-23-2014.html

The full text article is available as a PDF file from https://ap.copernicus.org/articles/1/23/2014/ap-1-23-2014.pdf

Cosmic rays are the main agents in controlling the chemical evolution and setting the ambipolar diffusion time of a molecular cloud. We summarise the processes causing the energy degradation of cosmic rays due to their interaction with molecular hydrogen, focusing on the magnetic effects that influence their propagation. Making use of magnetic field configurations generated by numerical simulations, we show that the increase of the field line density in the collapse region results in a reduction of the cosmic-ray ionisation rate. As a consequence the ionisation fraction decreases, facilitating the decoupling between the gas and the magnetic field.

References 1

Balbus, S. A. and Hawley, J. F.: A powerful local shear instability in weakly magnetized disks. I – Linear analysis. II – Nonlinear evolution, Astrophys. J., 376, 214–222, 1991.

Becker, J. K., Black, J. H., Safarzadeh, M., and Schuppan, F.: Tracing the Sources of Cosmic Rays with Molecular Ions, Astrophys. J., 739, L43, <a href="http://dx.doi.org/10.1088/2041-8205/739/2/L43">https://doi.org/10.1088/2041-8205/739/2/L43</a>, 2011.

Casadei, D. and Bindi, V.: The Origin of Cosmic Ray Electrons and Positrons, Astrophys. J., 612, 262–267, 2004.

Ceccarelli, C., Hily-Blant, P., Montmerle, T., Dubus, G., Gallant, Y., and Fiasson, A.: Supernova-enhanced Cosmic-Ray Ionization and Induced Chemistry in a Molecular Cloud of W51C, Astrophys. J. Lett., 740, L4, <a href="http://dx.doi.org/10.1088/2041-8205/740/1/L4">https://doi.org/10.1088/2041-8205/740/1/L4</a>, 2011.

Cleeves, L. I., Adams, F. C., Bergin, E. A., and Visser, R.: Radionuclide Ionization in Protoplanetary Disks: Calculations of Decay Product Radiative Transfer, Astrophys. J., 777, 28, <a href="http://dx.doi.org/10.1088/0004-637X/777/1/28">https://doi.org/10.1088/0004-637X/777/1/28</a>, 2013.

Dalgarno, A., Yan, M., and Liu, W.: Electron Energy Deposition in a Gas Mixture of Atomic and Molecular Hydrogen and Helium, Astrophys. J. Suppl. S., 125, 237–256, 1999.

Dapp, W. B., Basu, S., and Kunz, M. W.: Bridging the gap: disk formation in the Class 0 phase with ambipolar diffusion and Ohmic dissipation, Astron. Astrophys., 541, A35, <a href="http://dx.doi.org/10.1051/0004-6361/201117876">https://doi.org/10.1051/0004-6361/201117876</a>, 2012.

Fromang, S., Hennebelle, P., and Teyssier, R.: A high order Godunov scheme with constrained transport and adaptive mesh refinement for astrophysical magnetohydrodynamics, Astron. Astrophys., 457, 371–384, <a href="http://dx.doi.org/10.1051/0004-6361:20065371">https://doi.org/10.1051/0004-6361:20065371</a>, 2006.

Gerin, M., De Luca, M., Black, J., et al.: Interstellar \chemOH^+, \chemH_2O^+ and \chemH_3O^+ along the sight-line to G10.6–0.4, Astron. Astrophys., 518, L110, <a href="http://dx.doi.org/10.1051/0004-6361/201014576">https://doi.org/10.1051/0004-6361/201014576</a>, 2010.

Glassgold, A. E. and Langer, W. D.: Heating of Molecular-Hydrogen Clouds by Cosmic Rays and X-Rays, Astrophys. J., 186, 859–888, 1973.

Glassgold, A. E., Galli, D., and Padovani, M.: Cosmic-Ray and X-Ray Heating of Interstellar Clouds and Protoplanetary Disks, Astrophys. J., 756, 157, <a href="http://dx.doi.org/10.1088/0004-637X/756/2/157">https://doi.org/10.1088/0004-637X/756/2/157</a>, 2012.

Goto, M., Usuda, T., Nagata, T., Geballe, T. R., McCall, B. J., C. P.,Indriolo, N., Suto, H., Henning, T., Morong, C. P., and Oka, T.: Absorption Line Survey of H^+3 toward the Galactic Center Sources. II. Eight Infrared Sources within 30 pc of the Galactic Center 2008, Astrophys. J., 688, 306, <a href="http://dx.doi.org/10.1086/591657">https://doi.org/10.1086/591657</a>, 2008.

Indriolo, N. and McCall, B. J.: Investigating the Cosmic-Ray Ionization Rate in the Galactic Diffuse Interstellar Medium Through Observations of H+3, Astrophys. J., 745, 91, <a href="http://dx.doi.org/10.1088/0004-637X/745/1/91">https://doi.org/10.1088/0004-637X/745/1/91</a>, 2012.

Joos, M., Hennebelle, P., and Ciardi, A.: Protostellar disk formation and transport of angular momentum during magnetized core collapse, Astron. Astrophys., 543, A128, <a href="http://dx.doi.org/10.1051/0004-6361/201118730">https://doi.org/10.1051/0004-6361/201118730</a>, 2012.

Krolik, J. H. and Kallman, T. R.: X-ray ionization and the Orion molecular cloud, Astrophys. J., 267, 610–624, 1983.

Longair, M. S.: High Energy Astrophysics, Cambridge University Press, Cambridge, UK, 2002.

McKee, C. F.: Photoionization-regulated star formation and the structure of molecular clouds, Astrophys. J., 345, 782–801, <a href="http://dx.doi.org/10.1086/167950">https://doi.org/10.1086/167950</a>, 1989.

McKee, C. F. and Ostriker, E. C.: Theory of Star Formation, Annu. Rev. Astron. Astr., 45, 565–687, <a href="http://dx.doi.org/10.1146/annurev.astro.45.051806.110602">https://doi.org/10.1146/annurev.astro.45.051806.110602</a>, 2007.

Mellon, R. R. and Li, Z.-H.: Magnetic Braking and Protostellar Disk Formation: Ambipolar Diffusion, Astrophys. J., 698, 922, <a href="http://dx.doi.org/10.1088/0004-637X/698/1/922">https://doi.org/10.1088/0004-637X/698/1/922</a> 2009.

Montmerle, T.: Gamma-rays from star-forming regions: from SNOBs to Dark Accelerators, in: High Energy Phenomena in Massive Stars, San Francisco, CA, edited by: Mart\'i, J., Luque-Escamilla, P. L., and Combi, J. A., ASP Conf. Ser. 422, p. 85, 2010.

Nath, B. B. and Biermann, P. L.: Cosmic ray ionization of the interstellar medium, Mon. Not. R. Astron. Soc., 267, 447–451, 1994.

Neufeld, D. A., Goicoechea, J. R., Sonnentrucker, P., et al.: Herschel/HIFI observations of interstellar OH+ and \chemH_2O^+ towards W49N: a probe of diffuse clouds with a small molecular fraction, Astron. Astrophys., 521, L10, <a href="http://dx.doi.org/10.1051/0004-6361/201015077">https://doi.org/10.1051/0004-6361/201015077</a>, 2010.

Padovani, M. and Galli, D.: Effects of magnetic fields on the cosmic-ray ionization of molecular cloud cores, Astron. Astrophys., 530, A109, <a href="http://dx.doi.org/10.1051/0004-6361/201116853">https://doi.org/10.1051/0004-6361/201116853</a>, 2011.

Padovani, M. and Galli, D.: Cosmic-Ray Propagation in Molecular Clouds, in: Cosmic Rays in Star-Forming Environments, edited by: Torres, D. F. and Reimer, O., Advances in Solid State Physics, Springer, Berlin, 34, 61–82, 2013.

Padovani, M., Galli, D., and Glassgold, A. E.: Cosmic-ray ionization of molecular clouds, Astron. Astrophys., 501, 619–631, 2009.

Padovani, M., Hennebelle, P., and Galli, D.: Cosmic-ray ionisation in collapsing clouds, Astron. Astrophys., 560, A114, <a href="http://dx.doi.org/10.1051/0004-6361/201322407">https://doi.org/10.1051/0004-6361/201322407</a>, 2013.

Padovani, M., Galli, D., Hennebelle, P., Commerçon, B., and Joos, M.: The role of cosmic rays on magnetic field diffusion and the formation of protostellar discs, Astron. Astrophys., submitted, 2014.

Phelps, A. V.: Cross Sections and Swarm Coefficients for H+, H2+, H+3, H, H2, and H- in H2 for Energies from 0.1 eV to 10 keV, J. Phys. Chem. Ref. Data, 19, 653, <a href="http://dx.doi.org/10.1063/1.555858">https://doi.org/10.1063/1.555858</a>, 1990.

Potgieter, M. S.: Very local interstellar spectra for galactic electrons, protons and helium, in: 33rd ICRC, Rio de Janeiro, Brazil, 2013, The Astroparticle Physics Conference, arXiv:1310.6133v1, 2013.

Potgieter, M. S., Vos, E. E., Nndanganeni, R. R., Boezio, M., and Munini, R.: A Very Local Interstellar Spectrum for Galactic Electrons, in: 33rd ICRC, Rio de Janeiro, Brazil, 2013, The Astroparticle Physics Conference, arXiv:1308.1591v1, 2013.

Schlickeiser, R.: Cosmic Ray Astrophysics, Springer Berlin, 2002.

Silk, J. and Norman, C.: X-ray emission from pre-main-sequence stars, molecular clouds and star formation, Astrophys. J. Lett., 272, L49–L53, 1983.

Spitzer Jr., L. J. and Tomasko, M. G.: Heating of H i Regions by Energetic Particles, Astrophys. J., 152, p. 971, <a href="http://dx.doi.org/10.1086/149610">https://doi.org/10.1086/149610</a>, 1968.

Teyssier, R.: Cosmological hydrodynamics with adaptive mesh refinement, Astron. Astrophys., 385, 337–364, <a href="http://dx.doi.org/10.1051/0004-6361:20011817">https://doi.org/10.1051/0004-6361:20011817</a>, 2002.

Umebayashi, T. and Nakano, T.: Fluxes of Energetic Particles and the Ionization Rate in Very Dense Interstellar Clouds, Publ. Astron. Soc. Jpn., 33, 617–635, 1981.

Wakelam, V., Herbst, E., Le Bourlot, J., Hersant, F., Selsis, F., and Guilloteau, S.: Sensitivity analyses of dense cloud chemical models, Astron. Astrophys., 517, A21, <a href="http://dx.doi.org/10.1051/0004-6361/200913856">https://doi.org/10.1051/0004-6361/200913856</a>, 2010.

Wdowczyk, J. and Wolfendale, A. W.: Highest energy cosmic rays, Annu. Rev. Nucl. Part. S., 39, 43–71, <a href="http://dx.doi.org/10.1146/annurev.ns.39.120189.000355">https://doi.org/10.1146/annurev.ns.39.120189.000355</a>, 1989.