ON THE ROLE OF PSEUDODISK WARPING AND RECONNECTION IN PROTOSTELLAR DISK FORMATION IN TURBULENT MAGNETIZED CORES

The formation of rotationally supported protostellar disks is suppressed in ideal MHD in non-turbulent cores with aligned magnetic field and rotation axis. A promising way to resolve this so-called "magnetic braking catastrophe" is through turbulence. The reason for the turbulence-enabled disk formation is usually attributed to the turbulence-induced magnetic reconnection, which is thought to reduce the magnetic flux accumulated in the disk-forming region. We advance an alternative interpretation, based on magnetic decoupling-triggered reconnection of severely pinched field lines close to the central protostar and turbulence-induced warping of the pseudodisk of Galli and Shu. Such reconnection weakens the central split magnetic monopole that lies at the heart of the magnetic braking catastrophe under flux freezing. We show, through idealized numerical experiments, that the pseudodisk can be strongly warped, but not completely destroyed, by a subsonic or sonic turbulence. The warping decreases the rates of angular momentum removal from the pseudodisk by both magnetic torque and outflow, making it easier to form a rotationally supported disk. More importantly, the warping of the pseudodisk out of the disk-forming, equatorial plane greatly reduces the amount of magnetic flux threading the circumstellar, disk-forming region, further promoting disk formation. The beneficial effects of pseudodisk warping can also be achieved by a misalignment between the magnetic field and rotation axis. These two mechanisms of disk formation, enabled by turbulence and field-rotation misalignment respectively, are thus unified. We find that the disks formed in turbulent magnetized cores are rather thick and significantly magnetized. Implications of these findings, particularly for the thick young disk inferred in L1527, are briefly discussed.

[1]  R. Klein,et al.  THE FRAGMENTATION OF MAGNETIZED, MASSIVE STAR-FORMING CORES WITH RADIATIVE FEEDBACK , 2012, 1211.3467.

[2]  F. Shu,et al.  Collapse of magnetized molecular cloud cores. I: Semianalytical solution , 1993 .

[3]  P. Hennebelle,et al.  Magnetic processes in a collapsing dense core I. Accretion and ejection , 2007, 0709.2886.

[4]  A. Lazarian,et al.  THE ROLE OF TURBULENT MAGNETIC RECONNECTION IN THE FORMATION OF ROTATIONALLY SUPPORTED PROTOSTELLAR DISKS , 2011, 1109.3716.

[5]  M. Wardle,et al.  The Hall effect in star formation , 2011, 1109.1370.

[6]  V. Wakelam,et al.  SURVIVAL OF INTERSTELLAR MOLECULES TO PRESTELLAR DENSE CORE COLLAPSE AND EARLY PHASES OF DISK FORMATION , 2013, 1307.6868.

[7]  P. Hennebelle,et al.  Disk formation during collapse of magnetized protostellar cores , 2009, 0909.3190.

[8]  R. Pudritz,et al.  THE EARLY HISTORY OF PROTOSTELLAR DISKS, OUTFLOWS, AND BINARY STARS , 2009, 0910.1615.

[9]  G. Kowal,et al.  NUMERICAL TESTS OF FAST RECONNECTION IN WEAKLY STOCHASTIC MAGNETIC FIELDS , 2009, 0903.2052.

[10]  Zhi-Yun Li,et al.  ALIGNMENT BETWEEN FLATTENED PROTOSTELLAR INFALL ENVELOPES AND AMBIENT MAGNETIC FIELDS , 2013, 1305.2922.

[11]  Zhi-Yun Li,et al.  MAGNETIC FLUX EXPULSION IN STAR FORMATION , 2011, 1105.5739.

[12]  N. Patel,et al.  A KEPLERIAN CIRCUMBINARY DISK AROUND THE PROTOSTELLAR SYSTEM L1551 NE , 2012, 1205.3854.

[13]  C. Brinch,et al.  A deeply embedded young protoplanetary disk around L1489 IRS observed by the submillimeter array , 2007, 0709.3175.

[14]  Zhi-Yun Li,et al.  DISK FORMATION ENABLED BY ENHANCED RESISTIVITY , 2010, 1006.0793.

[15]  C. Hull,et al.  PROTOSTELLAR DISK FORMATION ENABLED BY WEAK, MISALIGNED MAGNETIC FIELDS , 2013, 1301.5648.

[16]  M. Hogerheijde,et al.  Rotationally-supported disks around Class I sources in Taurus: disk formation constraints , 2013, 1312.5716.

[17]  C. Gammie,et al.  Transport and Accretion in Planet-Forming Disks , 2014, 1401.7306.

[18]  D. Marrone,et al.  DETECTION OF A MAGNETIZED DISK AROUND A VERY YOUNG PROTOSTAR , 2013, 1311.6225.

[19]  Daniel J. Price,et al.  The effect of magnetic fields on the formation of circumstellar discs around young stars , 2007, 0705.1096.

[20]  B. Matthews,et al.  MAGNETIC FIELD STRUCTURE AROUND LOW-MASS CLASS 0 PROTOSTARS: B335, L1527, AND IC348-SMM2 , 2011, 1103.4370.

[21]  Charlottesville,et al.  PROTOSTELLAR ACCRETION FLOWS DESTABILIZED BY MAGNETIC FLUX REDISTRIBUTION , 2012, 1205.4083.

[22]  M. Wardle,et al.  The Hall effect in accretion flows , 2012, 1208.5887.

[23]  National Tsing Hua University,et al.  A Keplerian disk around a Class 0 source: ALMA observations of VLA1623A , 2013, 1310.8481.

[24]  T. Mouschovias,et al.  The non-isothermal stage of magnetic star formation - II. Results , 2010, 1003.2722.

[25]  Zhi-Yun Li,et al.  DISK FORMATION IN MAGNETIZED CLOUDS ENABLED BY THE HALL EFFECT , 2011, 1101.3018.

[26]  L. Mundy,et al.  MISALIGNMENT OF MAGNETIC FIELDS AND OUTFLOWS IN PROTOSTELLAR CORES , 2012, 1212.0540.

[27]  S. Inutsuka,et al.  Effect of Magnetic Braking on Circumstellar Disk Formation in a Strongly Magnetized Cloud , 2010, 1009.2140.

[28]  Zhi-Yun Li,et al.  MAGNETIC BRAKING AND PROTOSTELLAR DISK FORMATION: AMBIPOLAR DIFFUSION , 2008, 0809.3593.

[29]  Philip J. Armitage,et al.  Dynamics of Protoplanetary Disks , 2010, 1011.1496.

[30]  L. Hartmann,et al.  A ∼0.2-solar-mass protostar with a Keplerian disk in the very young L1527 IRS system , 2012, Nature.

[31]  P. Hennebelle,et al.  Outflows and mass accretion in collapsing dense cores with misaligned rotation axis and magnetic field , 2010, Monthly Notices of the Royal Astronomical Society: Letters.

[32]  Zhi-Yun Li,et al.  Collapse of Magnetized Singular Isothermal Toroids. II. Rotation and Magnetic Braking , 2003, astro-ph/0311377.

[33]  F. Adams,et al.  Star Formation in Molecular Clouds: Observation and Theory , 1987 .

[34]  Magnetic fields in molecular clouds , 2012 .

[35]  M. Norman,et al.  ZEUS-2D : a radiation magnetohydrodynamics code for astrophysical flows in two space dimensions. II : The magnetohydrodynamic algorithms and tests , 1992 .

[36]  Zhi-Yun Li,et al.  The Earliest Stages of Star and Planet Formation: Core Collapse, and the Formation of Disks and Outflows , 2014, 1401.2219.

[37]  A. Lazarian,et al.  Disc formation in turbulent cloud cores: is magnetic flux loss necessary to stop the magnetic braking catastrophe or not? , 2012, 1211.1059.

[38]  Averting the magnetic braking catastrophe on small scales: disk formation due to Ohmic dissipation , 2010 .

[39]  R. Klessen,et al.  Turbulence-induced disc formation in strongly magnetized cloud cores , 2013, 1302.4901.

[40]  P. Bodenheimer.  Angular Momentum Evolution of Young Stars and Disks , 1995 .

[41]  P. Bodenheimer,et al.  The formation of protostellar disks. I - 1 M(solar) , 1993 .

[42]  R. Klessen,et al.  Disc formation in turbulent massive cores: circumventing the magnetic braking catastrophe , 2012, 1201.5302.

[43]  Zhi-Yun Li,et al.  NON-IDEAL MHD EFFECTS AND MAGNETIC BRAKING CATASTROPHE IN PROTOSTELLAR DISK FORMATION , 2011, 1106.2620.

[44]  Zhi-Yun Li,et al.  Hydromagnetic Accretion Shocks around Low-Mass Protostars , 1996 .

[45]  P. Hennebelle,et al.  Protostellar disk formation and transport of angular momentum during magnetized core collapse , 2012, 1203.1193.

[46]  S. Okuzumi,et al.  RADIATION MAGNETOHYDRODYNAMIC SIMULATIONS OF PROTOSTELLAR COLLAPSE: PROTOSTELLAR CORE FORMATION , 2012, 1206.3567.

[47]  Jonathan P. Williams,et al.  Protoplanetary Disks and Their Evolution , 2011, 1103.0556.

[48]  R. Klessen,et al.  Magnetic fields during the early stages of massive star formation – I. Accretion and disc evolution , 2011, 1106.4485.

[49]  Zhi-Yun Li,et al.  Magnetic Braking and Protostellar Disk Formation: The Ideal MHD Limit , 2007, 0709.0445.

[50]  T. Treu,et al.  AN ENVIRONMENTAL STUDY OF THE ULTRALUMINOUS X-RAY SOURCE POPULATION IN EARLY-TYPE GALAXIES , 2013, 1311.4544.

[51]  R. Crutcher,et al.  Magnetic Fields in Dark Cloud Cores: Arecibo OH Zeeman Observations , 2008, 0802.2253.

[52]  L. Hartmann,et al.  MODELING THE RESOLVED DISK AROUND THE CLASS 0 PROTOSTAR L1527 , 2013, 1305.3604.

[53]  Wolf B. Dapp,et al.  Bridging the gap: disk formation in the Class 0 phase with ambipolar diffusion and Ohmic dissipation , 2011, 1112.3801.

[54]  Reconnection in a weakly stochastic field , 1998, astro-ph/9811037.

[55]  J. Silk.  Molecular Clouds and Star Formation , 1980 .

[56]  E. Bergin,et al.  ALMA observations of the kinematics and chemistry of disc formation , 2014, 1405.1416.

[57]  Chin-Fei Lee.  A ROTATING DISK IN THE HH 111 PROTOSTELLAR SYSTEM , 2011, 1108.1896.

[58]  F. Shu,et al.  Gravitational Collapse of Magnetized Clouds. I. Ideal Magnetohydrodynamic Accretion Flow , 2006, astro-ph/0604573.

[59]  Cecilia Ceccarelli,et al.  Our astrochemical heritage , 2012, 1210.6368.

[60]  Taipei,et al.  DOES MAGNETIC-FIELD-ROTATION MISALIGNMENT SOLVE THE MAGNETIC BRAKING CATASTROPHE IN PROTOSTELLAR DISK FORMATION? , 2013, 1301.6545.

[61]  K. Rice,et al.  Protostars and Planets V , 2005 .

[62]  D. Wilner,et al.  PROSAC: a submillimeter array survey of low-mass protostars - II. The mass evolution of envelopes, disks, and stars from the class 0 through I stages , 2009, 0909.3386.

[63]  P. Hennebelle,et al.  The influence of turbulence during magnetized core collapse and its consequences on low-mass star formation , 2013, 1301.3004.