We present a self-consistent mean field theory of the dynamo in 3D and turbulent diffusion in 2D in weakly ionized gas. We find that in 3D, the backreaction does not alter the beta effect while it suppresses the alpha effect when the strength of a mean magnetic field exceeds the critical value Bc ∼ √ νinτn〈v2〉/Rm. Here, νin, τn, and Rm are ion-neutral collision frequency, correlation time of ne...

A remarkable structure is observed in the innermost regions of the barred galaxy NGC 1415 : a small stellar bar, bright circumnuclear ionized gas seen in Hα, two bright ionized gas sources, seen in Hα, just beyond the ends of the small bar and a boxy distribution of optical continuum. We have developed a mass distribution model consisting in a disk, a bulge, and a bar to approximate the observe...

In order to distinguish between the various components of massive star forming regions (i.e. infalling, outflowing and rotating gas structures) within our own Galaxy, we require high angular resolution observations which are sensitive to structures on all size scales. To this end, we present observations of the molecular and ionized gas towards massive star forming regions at 230 GHz from the S...

Studies of the kinematics of gaseous halos in some spiral galaxies have shown that the rotational velocity of the gas decreases with height above the midplane (z). This vertical velocity gradient has been observed in both the neutral and ionized components of halos. We present imaging Fabry–Perot Hα observations of the edge-on galaxy NGC 5775. These observations allow us to study the variation ...

The modified Rankine-Hugoniot equations across a standing normal shockwave were discussed and adapted to obtain jump conditions for shockwave structure calculations. Coupling the modified Rankine-Hugoniot equations with the Burnett equations, the shockwave structure in a weakly ionized gas flow was computed and analyzed for a wide range of free-stream Mach numbers ranging from 1.75 to 6.0, with...

We have studied the kinematics of the ionized gas in the nearly face-on galaxy NGC 3938 by means of observations made with the Fabry–Perot interferometer TAURUS II at the William Herschel Telescope, using the Hα line. We have been able to produce high-resolution velocity and velocity-dispersion maps which allow us to make a detailed study of the kinematics of the ionized gas. In particular we h...

Context. The properties of the gas in halos of galaxies constrain global models of the interstellar medium. Kinematical information is of particular interest since it is a clue to the origin of the gas. Aims. Here we report observations of the kinematics of the thick layer of the diffuse ionized gas in NGC 891 in order to determine the rotation curve of the halo gas. Methods. We have obtained a...