Spatially Resolved Spectroscopy of Starburst and Post-Starburst Galaxies in The Rich z~0.55 Cluster CL0016+16

We have used the Low Resolution Imaging Spectrograph (LRIS) on the W.M. Keck I telescope to obtain spatially resolved spectroscopy of a small sample of six post-starburst and three dusty-starburst galaxies in the rich cluster CL0016+16 at z=0.55. We use this to measure radial profiles of the Hdelta and OII3727 lines which are diagnostic probes of the mechanisms that give rise to the abrupt changes in star-formation rates in these galaxies. In the post-starburst sample we are unable to detect any radial gradients in the Hdelta line equivalent width - although one galaxy exhibits a gradient from one side of the galaxy to the other. The absence of Hdelta gradients in these galaxies is consistent with their production via interaction with the intra-cluster medium, however, our limited spatial sampling prevents us from drawing robust conclusions. All members of the sample have early type morphologies, typical of post-starburst galaxies in general, but lack the high incidence of tidal tails and disturbances seen in local field samples. This argues against a merger origin and adds weight to a scenario where truncation by the intra-cluster medium is at work. The post-starburst spectral signature is consistent over the radial extent probed with no evidence of OII3727 emission and strong Hdelta absorption at all radii i.e. the post-starburst classification is not an aperture effect. In contrast the dusty-starburst sample shows a tendency for a central concentration of OII3727 emission. This is most straightforwardly interpreted as the consequence of a central starburst. However, other possibilities exist such as a non-uniform dust distribution (which is expected in such galaxies) and/or a non-uniform starburst age distribution. The sample exhibit late type and irregular morphologies.Comment: accepted for publication in PAS

Microscopic Theory of Current-Spin Interaction in Ferromagnets

Interplay between magnetization dynamics and electric current in a conducting ferromagnet is theoretically studied based on a microscopic model calculation. First, the effects of the current on magnetization dynamics (spin torques) are studied with special attention to the "dissipative" torques arising from spin-relaxation processes of conduction electrons. Next, an analysis is given of the "spin motive force", namely, a spin-dependent 'voltage' generation due to magnetization dynamics, which is the reaction to spin torques. Finally, an attempt is presented of a unified description of these effects.Comment: Written in December 2008, published in July 200

Numerical approach for retention characteristics of double floating-gate memories

We report on a numerical investigation in which memory characteristics of double floating-gate (DFG) structure were compared to those of the conventional single floating-gate structure, including an interference effect between two cells. We found that the advantage of the DFG structure is its longer retention time and the disadvantage is its smaller threshold voltage shift. We also provide an analytical form of charging energy including the interference effect.Comment: 4 pages, 4 figure

Kinematic Effects of Tidal Interaction on Galaxy Rotation Curves

We use self-consistent N-body models, in conjunction with models of test particles moving in galaxy potentials, to explore the initial effects of interactions on the rotation curves of spiral galaxies. Using nearly self-consistent disk/bulge/halo galaxy models (Kuijken & Dubinski 1995), we simulate the first pass of galaxies on nearly parabolic orbits; we vary orbit inclinations, galaxy halo masses and impact parameters. For each simulation, we mimic observed rotation curves of the model galaxies. Transient interaction-induced features of the curves include distinctly rising or falling profiles at large radii and pronounced bumps in the central regions. Remarkably similar features occur in our statistical sample of optical emission-line rotation curves of spiral galaxies in tight pairs and n-tuples.Comment: 9 pages, 2 figures, accepted for publication in ApJ Letter

The Advantage of Increased Resolution in the Study of Quasar Absorption Systems

We compare a new R = 120,000 spectrum of PG1634+706 (z_QSO = 1.337,m_V = 14.9) obtained with the HDS instrument on Subaru to a R = 45, 000 spectrum obtained previously with HIRES/Keck. In the strong MgII system at z = 0.9902 and the multiple cloud, weak MgII system at z = 1.0414, we find that at the higher resolution, additional components are resolved in a blended profile. We find that two single-cloud weak MgII absorbers were already resolved at R = 45,000, to have b = 2 - 4 km/s. The narrowest line that we measure in the R = 120, 000 spectrum is a component of the Galactic NaI absorption, with b = 0.90+/-0.20 km/s. We discuss expectations of similarly narrow lines in various applications, including studies of DLAs, the MgI phases of strong MgII absorbers, and high velocity clouds. By applying Voigt profile fitting to synthetic lines, we compare the consistency with which line profile parameters can be accurately recovered at R = 45,000 and R = 120,000. We estimate the improvement gained from superhigh resolution in resolving narrowly separated velocity components in absorption profiles. We also explore the influence of isotope line shifts and hyperfine splitting in measurements of line profile parameters, and the spectral resolution needed to identify these effects. Super high resolution spectra of quasars, which will be routinely possible with 20-meter class telescopes, will lead to greater sensitivity for absorption line surveys, and to determination of more accurate physical conditions for cold phases of gas in various environments.Comment: To appear in AJ. Paper with better resolution images available at http://www.astro.psu.edu/users/anand/superhigh.AJ.pd

Dynamic Modes of Microcapsules in Steady Shear Flow: Effects of Bending and Shear Elasticities

The dynamics of microcapsules in steady shear flow was studied using a theoretical approach based on three variables: The Taylor deformation parameter $\alpha_{\rm D}$, the inclination angle $\theta$, and the phase angle $\phi$ of the membrane rotation. It is found that the dynamic phase diagram shows a remarkable change with an increase in the ratio of the membrane shear and bending elasticities. A fluid vesicle (no shear elasticity) exhibits three dynamic modes: (i) Tank-treading (TT) at low viscosity $\eta_{\rm {in}}$ of internal fluid ($\alpha_{\rm D}$ and $\theta$ relaxes to constant values), (ii) Tumbling (TB) at high $\eta_{\rm {in}}$ ($\theta$ rotates), and (iii) Swinging (SW) at middle $\eta_{\rm {in}}$ and high shear rate $\dot\gamma$ ($\theta$ oscillates). All of three modes are accompanied by a membrane ($\phi$) rotation. For microcapsules with low shear elasticity, the TB phase with no $\phi$ rotation and the coexistence phase of SW and TB motions are induced by the energy barrier of $\phi$ rotation. Synchronization of $\phi$ rotation with TB rotation or SW oscillation occurs with integer ratios of rotational frequencies. At high shear elasticity, where a saddle point in the energy potential disappears, intermediate phases vanish, and either $\phi$ or $\theta$ rotation occurs. This phase behavior agrees with recent simulation results of microcapsules with low bending elasticity.Comment: 11 pages, 14 figure