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@ARTICLE{Dapp:139150,
      author       = {Dapp, Wolfgang and Basu, Shantanu and Kunz, Matthew W.},
      title        = {{B}ridging the gap: disk formation in the {C}lass 0 phase
                      with ambipolar diffusion and {O}hmic dissipation},
      journal      = {Astronomy and astrophysics},
      volume       = {541},
      issn         = {1432-0746},
      address      = {Les Ulis},
      publisher    = {EDP Sciences},
      reportid     = {FZJ-2013-05157},
      pages        = {A35 -},
      year         = {2012},
      abstract     = {Context. Ideal magnetohydrodynamical (MHD) simulations have
                      revealed catastrophic magnetic braking in the protostellar
                      phase, which prevents the formation of a centrifugal disk
                      around a nascent protostar. Aims. We determine if non-ideal
                      MHD, including the effects of ambipolar diffusion and Ohmic
                      dissipation determined from a detailed chemical network
                      model, will allow for disk formation at the earliest stages
                      of star formation. Methods. We employ the axisymmetric
                      thin-disk approximation in order to resolve a dynamic range
                      of 9 orders of magnitude in length and 16 orders of
                      magnitude in density, while also calculating partial
                      ionization using up to 19 species in a detailed chemical
                      equilibrium model. Magnetic braking is applied to the
                      rotation using a steady-state approximation, and a
                      barotropic relation is used to capture the thermal
                      evolution. Results. We resolve the formation of the first
                      and second cores, with expansion waves at the periphery of
                      each, a magnetic diffusion shock, and prestellar infall
                      profiles at larger radii. Power-law profiles in each region
                      can be understood analytically. After the formation of the
                      second core, the centrifugal support rises rapidly and a
                      low-mass disk of radius approximately $10 R_sun$ is formed
                      at the earliest stage of star formation, when the second
                      core has mass of about $0.001 M_sun.$ The mass-to-flux
                      ratio is about 10,000 times the critical value in the
                      central region. Conclusions. A small centrifugal disk can
                      form in the earliest stage of star formation, due to a
                      shut-off of magnetic braking caused by magnetic field
                      dissipation in the first core region. There is enough
                      angular momentum loss to allow the second collapse to occur
                      directly, and a low-mass stellar core to form with a
                      surrounding disk. The disk mass and size will depend upon
                      how the angular momentum transport mechanisms within the
                      disk can keep up with mass infall onto the disk. Accounting
                      only for direct infall, we estimate that the disk will
                      remain $\lessim$ 10 AU, undetectable even by ALMA, for
                      approximately 40,000 yr, representing the early Class 0
                      phase.},
      cin          = {JSC},
      ddc          = {520},
      cid          = {I:(DE-Juel1)JSC-20090406},
      pnm          = {411 - Computational Science and Mathematical Methods
                      (POF2-411)},
      pid          = {G:(DE-HGF)POF2-411},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000304390900035},
      doi          = {10.1051/0004-6361/201117876},
      url          = {https://juser.fz-juelich.de/record/139150},
}