Galaxy formation and evolution

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Bar Diagnostics in Edge-On Spiral Galaxies. III. N-Body Simulations of Disks

(2004)

Authors:

M Bureau, E Athanassoula

Black Hole Mass Determinations From Orbit Superposition Models are Reliable

(2004)

Authors:

Douglas Richstone, Karl Gebhardt, Monique Aller, Ralf Bender, Gary Bower, Alan Dressler, SM Faber, Alexei V Filippenko, Richard Green, Luis C Ho, John Kormendy, Tod R Lauer, John Magorrian, Jason Pinkney, Christos Siopis, Scott Tremaine

Stellar Kinematics of Boxy Bulges: Large-Scale Bars and Inner Disks

(2004)

Authors:

A Chung, M Bureau

The Star Formation Rate of the Universe at z~6 from the Hubble Ultra Deep Field

(2004)

Authors:

AJ Bunker, ER Stanway, RS Ellis, RG McMahon

Turbulent ambipolar diffusion: Numerical studies in two dimensions

Astrophysical Journal 603:1 I (2004) 165-179

Authors:

F Heitsch, EG Zweibel, AD Slyz, JEG Devriendt

Abstract:

Under ideal MHD conditions the magnetic field strength should be correlated with density in the interstellar medium (ISM). However, observations indicate that this correlation is weak. Ambipolar diffusion can decrease the flux-to-mass ratio in weakly ionized media; however, it is generally thought to be too slow to play a significant role in the ISM except in the densest molecular clouds. Turbulence is often invoked in astrophysical problems to increase transport rates above the (very slow) laminar values predicted by kinetic theory. We describe a series of numerical experiments addressing the problem of turbulent transport of magnetic fields in weakly ionized gases. We show, subject to various geometrical and physical restrictions, that turbulence in a weakly ionized medium rapidly diffuses the magnetic flux-to-mass ratio B/蟻 through the buildup of appreciable ion-neutral drifts on small scales. These results are applicable to the field strength-density correlation in the ISM, as well as the merging of flux systems such as protostar and accretion disk fields or protostellar jets with ambient matter, and the vertical transport of galactic magnetic fields.