Tidal Shear on Density Perturbations and Galaxy Formation

Abstract

The strenth of the tidal shear produced by the large-scale density field acting on primordial density perturbations is calculated in power law models. It is shown that the large-scale tidal field could, strongly affect the morphology, orientation and angular momentum aquisition of density peaks possibly playing a role in the formation of early-type galaxies. Evidence is presented that the correlacion between the orientation of perturbations and the large-scale density field could be a common property of Gaussian density fields with spectral indexes $n < 0$. We argue that alignment of strcutures as those detected for elliptical galaxies can be used to probe the the flatness of the spectrum on large scales but it cannot determine the exact value of the spectral index.