Correlation of Supernova Remnant Masers and Gamma-Ray Sources (2009)
Hewitt, John W., Yusef-Zadeh, Farhad, Wardle, Mark
Supernova remnants interacting with molecular clouds are potentially exciting systems in which to detect evidence of cosmic ray acceleration. Prominent gamma-ray emission is produced via the decay of...
On the Formation of Compact Stellar Disks Around Sgr A* (2008)
Wardle, Mark, Yusef-Zadeh, Farhad
The recent identification of one or two sub-parsec disks of young, massive stars orbiting the ~4e6 solar mass black hole Sgr A* has prompted an "in-situ" scenario for star formation in disks of gas...
A search for OH 6 GHz maser emission towards supernova remnants (2008)
McDonnell, Korinne E., Wardle, Mark, Vaughan, Alan E.
OH masers at 1720 MHz have proven to be excellent indicators of interactions between supernova remnants and molecular clouds. OH excitation calculations suggest that the 6049 MHz OH maser line is...
Magnetorotational instability in protoplanetary discs: The effect of dust grains (2008)
Salmeron, Raquel, Wardle, Mark
We investigate the linear growth and vertical structure of the MRI in protoplanetary discs when dust grains are well mixed with the gas over the entire disc thickness. All the grains have the same...
Hall magnetohydrodynamics of partially ionized plasmas (2007)
The Hall effect arises in a plasma when electrons are able to drift with the magnetic field but ions cannot. In a fully-ionized plasma this occurs for frequencies between the ion and electron...
ATCA 1.2 cm Observations of the Massive Star Forming Region G305.2+0.2 (2007)
Walsh, Andrew J., Chapman, Jacqueline F., Burton, Michael G., Wardle, Mark, Millar, T. J.
We report on Australia Telescope observations of the massive star forming region G305.2+0.2 at 1.2 cm. We detected emission in five molecules towards G305A, confirming its hot core nature. We...
Radial and vertical angular momentum transport in protostellar discs (2007)
Salmeron, Raquel, Königl, Arieh, Wardle, Mark
Angular momentum in protostellar discs can be transported either radially, through turbulence induced by the magnetorotational instability (MRI), or vertically, through the torque exerted by a...
A search for OH 6 GHz maser emission towards southern supernova remnants (2007)
McDonnell, Korinne E., Vaughan, Alan E., Wardle, Mark
OH masers at 1720 MHz have proven to be excellent indicators of interactions between supernova remnants and molecular clouds. Recent calculations suggest that the 6049 MHz OH maser line is excited...
Magnetic fields in protoplanetary disks (2007)
Magnetic fields likely play a key role in the dynamics and evolution of protoplanetary discs. They have the potential to efficiently transport angular momentum by MHD turbulence or via the...
OH (1720 MHz) masers serve as indicators of SNR - molecular cloud interaction sites. These masers are collisionally excited in warm (50-100K) shocked gas with densities of order 1e5 cm^-3 when the OH...
Walsh, Andrew J, Chapman, Jacqueline F, Burton, Michael G, Wardle, Mark, Millar, T. J
We report on Australia Telescope Compact Array observations of the massive star-forming region G305.2+0.2 at 1.2 cm. We detected emission in five molecules towards G305A, confirming its hot core...
Angular momentum transport in protostellar discs (2007)
Salmeron, Raquel, Königl, Arieh, Wardle, Mark
Angular momentum transport in protostellar discs can take place either radially, through turbulence induced by the magnetorotational instability (MRI), or vertically, through the torque exerted by a...
Magnetic fields in protoplanetary disks (2007)
Magnetic fields likely play a key role in the dynamics and evolution of protoplanetary disks. They have the potential to efficiently transport angular momentum by MHD turbulence or via the...
Radial and vertical angular momentum transport in protostellar discs (2007)
Salmeron, Raquel, Königl, Arieh, Wardle, Mark
Angular momentum in protostellar discs can be transported either radially, through turbulence induced by the magnetorotational instability (MRI), or vertically, through the torque exerted by a...
Walsh, Andrew J., Chapman, Jacqueline F., Burton, Michael G., Wardle, Mark, Millar, T.J.
We report on Australia Telescope Compact Array observations of the massive star-forming region G305.2+0.2 at 1.2 cm. We detected emission in five molecules towards G305A, confirming its hot core...
Angular momentum transport in protostellar discs (2006)
Salmeron, Raquel, Konigl, Arieh, Wardle, Mark
Angular momentum transport in protostellar discs can take place either radially, through turbulence induced by the magnetorotational instability (MRI), or vertically, through the torque exerted by a...
Hall Magnetohydrodynamics of weakly-ionized plasma (2006)
We show that the Hall scale in a weakly ionized plasma depends on the fractional ionization of the medium and, Hall MHD description becomes important whenever the ion-neutral collision frequency is...
Ion dynamics and the magnetorotational instability in weakly-ionized discs (2006)
The magnetorotational instability (MRI) of a weakly ionized, differentially rotating, magnetized plasma disk is investigated in the multi-fluid framework. The disk is threaded by a uniform vertical...
GBT Observations of IC 443: the Nature of OH(1720 MHz) Masers and OH Absorption (2006)
Hewitt, John W., Yusef-Zadeh, Farhad, Wardle, Mark, Roberts, Douglas A., Kassim, Namir E.
We present results of spectral line observations of the ground state transitions of hydroxyl(OH) toward supernova remnant IC 443 carried out with the Green Bank Telescope. At a spatial resolution of...
Ion dynamics and the magnetorotational instability in weakly ionized discs (2006)
The magnetorotational instability (MRI) of a weakly ionized, differentially rotating, magnetized plasma disc is investigated in the multifluid framework. The disc is threaded by a uniform vertical...
Dust grain dynamics in C-type shock waves in molecular clouds (2006)
We investigate the role and behaviour of dust grains in fast C-type magnetohydrodynamic (MHD) shock waves in weakly ionized, dense molecular clouds. We calculate the structure of steady, oblique,...
Ion dynamics and the magnetorotational instability in weakly ionized discs (2006)
The magnetorotational instability (MRI) of a weakly ionized, differentially rotating, magnetized plasma disc is investigated in the multifluid framework. The disc is threaded by a uniform vertical...
Dust grain dynamics in C-type shock waves in molecular clouds (2006)
We investigate the role and behaviour of dust grains in fast C-type magnetohydrodynamic (MHD) shock waves in weakly ionized, dense molecular clouds. We calculate the structure of steady, oblique,...
Dust grain dynamics in C-Type shock waves in molecular clouds (2006)
We investigate the role and behaviour of dust grains in fast C-type magnetohydrodynamic (MHD) shock waves in weakly ionized, dense molecular clouds. We calculate the structure of steady, oblique,...
Dust grain dynamics in C-Type shock waves in molecular clouds (2005)
Chapman, Jacqueline F., Wardle, Mark
We investigate the role and behaviour of dust grains in C-type MHD shock waves in weakly ionized, dense molecular clouds. New shock models are presented for steady, oblique C-type shock structures...
Magnetorotational instability in protoplanetary discs (2005)
Salmeron, Raquel, Wardle, Mark
We investigate the linear growth and vertical structure of the magnetorotational instability (MRI) in weakly ionized, stratified accretion discs. The magnetic field is initially vertical and dust...
Magnetorotational instability in protoplanetary discs (2004)
Salmeron, Raquel, Wardle, Mark
We investigate the linear growth and vertical structure of the magnetorotational instability (MRI) in weakly ionised, stratified accretion discs. The magnetic field is initially vertical and dust...
A variety of processes play a role in the evolution of protostellar disks. Here I focus on the uncertain issue of magnetic field-disk coupling and its implications for magnetically-driven turbulence...
Magnetorotational instability in stratified, weakly ionised accretion discs (2003)
Salmeron, Raquel, Wardle, Mark
We present a linear analysis of the vertical structure and growth of the magnetorotational instability in stratified, weakly ionised accretion discs, such as protostellar and quiescent dwarf novae...
Magnetorotational instability in weakly ionised, stratified accretion discs (2003)
Salmeron, Raquel, Wardle, Mark
The magnetorotational instability (MRI) (Balbus and Hawley 1991, Hawley and Balbus 1991) transports angular momentum radially outwards in accretion discs through the distortion of the magnetic field...
Star Formation and the Hall Effect (2003)
The breakdown of flux-freezing in molecular clouds and protostellar discs is usually approximated by ambipolar diffusion at low densities or by resistive diffusion at high densities. Here I discuss...
Magnetorotational instability in stratified, weakly-ionized accretion discs (2003)
Salmeron, Raquel, Wardle, Mark
We present a linear analysis of the vertical structure and growth of the magnetorotational instability in stratified, weakly ionized accretion discs, such as protostellar and quiescent dwarf novae...
Yusef-Zadeh, F., Shure, Mark, Wardle, Mark, Kassim, N.
The Trifid nebula (M20) is a well-known prominent optical HII region trisected by obscuring dust lanes. Radio continuum VLA observations of this Nebula show free-free emission at lambda 3.6 and 6cm...
Dwarkadas, Vikram, Ball, Lewis, Caswell, James, Green, Anne, Johnston, Simon, Schmidt, Brian, ...
We summarise the proceedings of the SRCfTA workshop on ``Supernova Remnants, Pulsars and the Interstellar Medium'' that was held at the University of Sydney on Mar 18 and 19, 1999.
Enhanced OH in C-type shock waves in molecular clouds (1999)
Cosmic-ray and X-ray ionisations in molecular gas produce a weak far-ultraviolet flux through the radiative decay of H2 molecules that have been excited by collisions with energetic electrons (the...
Modelling of Extreme Scattering Events suggests that the Galaxy's dark matter is an undetected population of cold, AU-sized, planetary-mass gas clouds. None of the direct observational constraints on...
Thermal stability of cold clouds in galaxy halos (1999)
We consider the thermal properties of cold, dense clouds of molecular hydrogen and atomic helium. For cloud masses below 10^-1.7 Msun, the internal pressure is sufficient to permit the existence of...
High velocity gas from the Galactic dark halo (1998)
We present the germ of a new model for High Velocity Clouds, derived from the idea that the dark matter halo of our Galaxy is in the form of cold, planetary-mass gas clouds. In this picture HVCs...
OH(1720 MHz) Masers at the Galactic Centre (1998)
Wardle, Mark, Yusef-Zadeh, Farhad, Geballe, T. R.
OH(1720 MHz) masers permit direct measurements of the magnetic field strength at the Galactic Centre, and their angular broadening constrains models for the medium that scatters radio waves in the...
The conductivity of dense molecular gas (1998)
We evaluate the conductivity tensor for molecular gas at densities ranging from 10^4 to 10^15 cm^-3 for a variety of grain models. The Hall contribution to the conductivity has generally been...
The Balbus-Hawley instability in weakly ionised discs (1998)
MHD in protostellar discs is modified by the Hall current when the ambipolar diffusion approximation breaks down. Here I examine the Balbus-Hawley (magnetorotational) instability of a weak, vertical...
Wardle, Mark, Yusef-Zadeh, Farhad, Geballe, T. R.
OH(1720 MHz) masers unaccompanied by 1665/7 MHz line masers have recently been proposed as indicators of the interaction of supernova remnants (SNRs) and molecular clouds. We present a model for the...
I examine the role of dust grains in determining the structure of steady, cold, oblique C-type shocks in dense molecular gas. Gas pressure, the inertia of the charged components, and changes in...
Extreme scattering events and Galactic dark matter (1998)
Extreme Scattering Events (ESEs) are attributed to radio-wave refraction by a cloud of free-electrons crossing the line-of-sight. We present a new model in which these electrons form the...
Magnetically-Driven Winds from Protostellar Disks (1997)
Angular momentum transport in protostellar disks can be achieved by the action of a large scale magnetic field that runs vertically through the disk. The magnetic field centrifugally drives material...