Near-infrared bulge–disc correlations of lenticular galaxies     

Sudhanshu Barway  Yogesh Wadadekar  Ajit K. Kembhavi  Y. D. Mayya 《Monthly notices of the Royal Astronomical Society》2009,394(4):1991-2000

We consider the luminosity and environmental dependence of structural parameters of lenticular galaxies in the near-infrared K band. Using a 2D galaxy image decomposition technique, we extract bulge and disc structural parameters for a sample of 36 lenticular galaxies observed by us in the K band. By combining data from the literature for field and cluster lenticulars with our data, we study correlations between parameters that characterize the bulge and the disc as a function of luminosity and environment. We find that scaling relations such as the Kormendy relation, photometric plane and other correlations involving bulge and disc parameters show a luminosity dependence. This dependence can be explained in terms of galaxy formation models in which faint lenticulars  ( M _T > −24.5)  formed via secular formation processes that likely formed the pseudo-bulges of late-type disc galaxies, while brighter lenticulars  ( M _T < −24.5)  formed through a different formation mechanism most likely involving major mergers. On probing variations in lenticular properties as a function of environment, we find that faint cluster lenticulars show systematic differences with respect to faint field lenticulars. These differences support the idea that the bulge and disc components fade after the galaxy falls into a cluster, while simultaneously undergoing a transformation from spiral to lenticular morphologies.  相似文献   

Sunspots and physics of magnetic flux tubes overstability and Kelvin-Helmholtz instability in a magnetic field     

Raghvendra Singh  Sudhanshu  Krishna M. Srivastava 《Astrophysics and Space Science》1983,89(1):201-220

We have studied the dynamical properties of convective overstability and Kelvin-Helmholtz instability in a vertical magnetic field with a downdraft. The Kelvin-Helmholtz instability and overstability produce the upward downward propagating Alfvén waves depending upon the magnitudes of the kinematic viscosity coefficient (eddy viscosity) ν, and thermometric conductivity κ. It is found that the instability may be driven by the density stratification and the effect of the eddy viscosity is to make the system stable. We discuss also the interaction of the overstability inx<0 and the downdraft inx>0, and the overstability at a vertical boundary of the field.  相似文献   

Thermal convection instability of a two-component fluid layer in hydromagnetics     

Krishna M. Srivastava  Sudhanshu  V. K. Katiyar 《Astrophysics and Space Science》1982,85(1-2):121-135

The thermal convection instability of a two component fluid layer subjected to a temperature gradient has been studied in the presence of an applied magnetic field. The associated thermal diffusion separation has a predominant effect even when the separations are small. Solutions for the non-oscillatory marginal states have been obtained. It is shown that the concentration gradient has a stabiliting or destabilizing effect according as T<or>0. Approximate solutions for the oscillatory solutions have been obtained by the method of variational principle and the dispersion relation has been solved numerically.  相似文献