%0 Generic %1 citeulike:51825 %A Porciani, Cristiano %A Dekel, Avishai %A Hoffman, Yehuda %D 2002 %K inertia locally proto-halo shear tidal torque %T Testing Tidal-Torque Theory: II. Alignment of Inertia and Shear and the Characteristics of Proto-haloes %U http://arxiv.org/abs/astro-ph/0105165 %X We investigate the cross-talk between the two key components of tidal-torque theory, the inertia (I) and shear (T) tensors, using a cosmological N-body simulation with thousands of well-resolved haloes. We find that the principal axes of I and T are strongly aligned, even though I characterizes the proto-halo locally while T is determined by the large-scale structure. Thus, the resultant galactic spin, which plays a key role in galaxy formation, is only a residual due to ~10 per cent deviations from perfect alignment of T and I. The T-I correlation induces a weak tendency for the proto-halo spin to be perpendicular to the major axes of T and I, but this correlation is erased by non-linear effects at late times, making the observed spins poor indicators of the initial shear field. However, the T-I correlation implies that the shear tensor can be used for identifying the positions and boundaries of proto-haloes in cosmological initial conditions -- a missing piece in galaxy formation theory. The typical configuration is of a prolate proto-halo lying perpendicular to a large-scale high-density ridge, with the surrounding voids inducing compression along the major and intermediate inertia axes of the proto-halo. This leads to a transient sub-halo filament along the large-scale ridge, whose sub-clumps then flow along the filament and merge into the final halo. The centres of proto-haloes tend to lie in ~1 sigma over-density regions, but their association with linear density maxima smoothed on galactic scales is vague: only ~40 per cent of the proto-haloes contain peaks within them. Several other characteristics distinguish proto-haloes from density peaks, e.g., they tend to compress along two principal axes while many peaks compress along three axes.

@misc{citeulike:51825, abstract = {We investigate the cross-talk between the two key components of tidal-torque theory, the inertia (I) and shear (T) tensors, using a cosmological N-body simulation with thousands of well-resolved haloes. We find that the principal axes of I and T are strongly aligned, even though I characterizes the proto-halo locally while T is determined by the large-scale structure. Thus, the resultant galactic spin, which plays a key role in galaxy formation, is only a residual due to ~10 per cent deviations from perfect alignment of T and I. The T-I correlation induces a weak tendency for the proto-halo spin to be perpendicular to the major axes of T and I, but this correlation is erased by non-linear effects at late times, making the observed spins poor indicators of the initial shear field. However, the T-I correlation implies that the shear tensor can be used for identifying the positions and boundaries of proto-haloes in cosmological initial conditions -- a missing piece in galaxy formation theory. The typical configuration is of a prolate proto-halo lying perpendicular to a large-scale high-density ridge, with the surrounding voids inducing compression along the major and intermediate inertia axes of the proto-halo. This leads to a transient sub-halo filament along the large-scale ridge, whose sub-clumps then flow along the filament and merge into the final halo. The centres of proto-haloes tend to lie in ~1 sigma over-density regions, but their association with linear density maxima smoothed on galactic scales is vague: only ~40 per cent of the proto-haloes contain peaks within them. Several other characteristics distinguish proto-haloes from density peaks, e.g., they tend to compress along two principal axes while many peaks compress along three axes.}, added-at = {2007-08-18T13:22:24.000+0200}, author = {Porciani, Cristiano and Dekel, Avishai and Hoffman, Yehuda}, biburl = {https://www.bibsonomy.org/bibtex/252d6a9b4a9a11b6d96deb703d034ce16/a_olympia}, citeulike-article-id = {51825}, description = {citeulike}, eprint = {astro-ph/0105165}, interhash = {44fdd2ce4c094069bbe0c72fb112a3fc}, intrahash = {52d6a9b4a9a11b6d96deb703d034ce16}, keywords = {inertia locally proto-halo shear tidal torque}, month = {January}, timestamp = {2007-08-18T13:22:59.000+0200}, title = {Testing Tidal-Torque Theory: II. Alignment of Inertia and Shear and the Characteristics of Proto-haloes}, url = {http://arxiv.org/abs/astro-ph/0105165}, year = 2002 }