16 research outputs found
Formation of Warped Disks by Galactic Fly-by Encounters. I. Stellar Disks
Warped disks are almost ubiquitous among spiral galaxies. Here we revisit and
test the `fly-by scenario' of warp formation, in which impulsive encounters
between galaxies are responsible for warped disks. Based on N-body simulations,
we investigate the morphological and kinematical evolution of the stellar
component of disks when galaxies undergo fly-by interactions with adjacent dark
matter halos. We find that the so-called `S'-shaped warps can be excited by
fly-bys and sustained for even up to a few billion years, and that this
scenario provides a cohesive explanation for several key observations. We show
that disk warp properties are governed primarily by the following three
parameters; (1) the impact parameter, i.e., the minimum distance between two
halos, (2) the mass ratio between two halos, and (3) the incident angle of the
fly-by perturber. The warp angle is tied up with all three parameters, yet the
warp lifetime is particularly sensitive to the incident angle of the perturber.
Interestingly, the modeled S-shaped warps are often non-symmetric depending on
the incident angle. We speculate that the puzzling U- and L-shaped warps are
geometrically superimposed S-types produced by successive fly-bys with
different incident angles, including multiple interactions with a satellite on
a highly elongated orbit.Comment: 16 pages, 13 figures, 3 tables. Accepted for publication in Ap
Tunnel Barrier Engineering of Titanium Oxide for High Non-Linearity of Selector-less Resistive Random Access Memory
In this study, the effect of the oxygen profile and thickness of multiple-layers TiOx on tunnel barrier characteristics was investigated to achieve high non-linearity in low-resistance state current (I-LRS). To form the tunnel barrier in multiple-layer of TiOx, tunnel barrier engineering in terms of the thickness and oxygen profile was attempted using deposition and thermal oxidation times. It modified the defect distribution of the tunnel barrier for effective suppression of ILRS at off-state (1/2V(Read)). By inserting modified tunnel barrier in resistive random access memory, a high non-linear I-LRS was exhibited with a significantly lowered I-LRS for 1/2V(Read). (C) 2014 AIP Publishing LLC.ope