Massive starburst galaxies in the early Universe are estimated to have depletion times of $\sim 100$ Myr and thus be able convert their gas very quickly into stars, possibly leading a rapid quenching star formation. For these reasons, they considered progenitors massive early-type (ETGs). In this paper, we study two high-$z$ starbursts, AzTEC/C159 ($z\simeq 4.57$) J1000+0234 4.54$), observed wi...

A prescription for the density of a wind compressed disc (WCD) is given and the IRemissionof the disc is calculated. The prescription enables emission fromWCDs to be calculated simply without recourse to full 2 1 2 -dimensional (2 1 2 -D) modelling of rotating radiatively driven winds. It is shown that the standard WCD model is incapable of representing observed Be star discs. As a guide for fu...

In this work the most spectacular phenomena occurring during the formation of a star are briefly reviewed: accretion through a rotating disc of matter and outflow through the poles of the new stellar object. Magnetic fields have been proposed to be principally responsible for the coexistence of these opposed mechanisms of accretion and outflowing. According to different models, the magnetic fie...

We study the stability of compressible cylindrical differentially rotating flow in the presence of the magnetic field, and show that compressibility alters qualitatively the stability properties of flows. Apart from the well-known magnetorotational instability that can occur even in incompressible flow, there exist a new instability caused by compressibility. The necessary condition of the newl...

We consider the evolution of a warped disc around a Kerr black hole, under conditions such that the warp propagates in a wavelike manner. This occurs when the dimensionless effective viscosity, α, that damps the warp is less than the characteristic angular semi-thickness, H/R, of the disc. We adopt linearized equations that are valid for warps of sufficiently small amplitude in a Newtonian disc...

We calculate the structure of accretion disc around a rapidly rotating black hole with a super-Eddington accretion rate. The luminosity and height of the disc are reduced by the advection effect. In the case of a large viscosity parameter, α > 0.03, the accretion flow strongly deviates from thermodynamic equilibrium and overheats in the central region. With increasing accretion rate, the flow t...

The effects of ambipolar diffusion on the linear stability of weakly ionised accretion discs are examined. Earlier work on this topic has focused on axial magnetic fields and perturbation wavenumbers. We consider here more general field and wavenumber geometries, and find that qualitatively new results are obtained. Provided a radial wavenumber and azimuthal field are present along with their a...

Massive galaxies in the young Universe, ten billion years ago, formed stars at surprising intensities1, 2. Although this is commonly attributed to violent mergers, the properties of many of these galaxies are incompatible with such events, showing gas-rich, clumpy, extended rotating disks not dominated by spheroids1, 2, 3, 4, 5. Cosmological simulations6 and clustering theory6, 7 are used to ex...

The spacetime of a boosted Bondi-Sachs rotating black hole is considered as proper background to examine electromagnetic configurations connected analytic solutions Maxwell equations. In our analysis, we first use the transformations in order bring metric into Kerr-Schild form, from which zero angular momentum observers (ZAMOs) are constructed via ADM formalism. coordinates obtain Killing field...

Recent observations of blue stragglers by De Marco et al. (2004) have revealed continuum deficits on the blue side of the Balmer discontinuity, leading these authors to infer the presence of discs around the stars. This intriguing possibility may throw light on aspects of the mechanisms responsible for at least some of these objects; current theories of blue straggler formation invoke stellar c...