Magnetogravitational instability in strongly coupled rotating clumpy molecular clouds including heating and cooling functions

Abstract

The molecular clouds (MCs) formation is caused due to gravitational collapse mechanism and is significantly affected due to radiative heating and cooling processes. The paper analyzes the gravitational instability in the strongly coupled clumpy MCs, under the effects of uniform rotation, magnetic field, and heatloss functions. The generalized hydrodynamic (GHD) equations coupled with the modified energy equation (which incorporates the heating and cooling effects due to cloud-cloud collisions) are used to describe the mathematical model. A general dispersion relation is analytically derived using the normal mode analysis method, by taking the orientations of the magnetic field and uniform rotation along the vertical direction. The Jeans criteria of gravitational instability are obtained for strongly and weakly coupling limits, which are modified due to the Coulomb coupling parameter, heat-loss functions, and viscoelastic coefficients. It is found that the value of the critical wavenumber decreases due to the strong coupling between the plasma particles (coupling parameter) and clump stirring processes (heating rate), thus both have stabilizing influence on the onset of gravitational collapse in clumpy MCs. The influence of various parameters on the growth rate of the instability is discussed numerically and it is found that the cooling rate parameter which described the cloud-cloud collisions shows the destabilizing effect. The region of instability is observed to be smaller in the strongly coupled clumps (kinetic limit) than in the weakly coupled (hydrodynamic limit) clumps. The results are helpful in understanding the role of heating and cooling mechanisms in the MCs formation.