Asymmetric Warping Research Articles

Warps and correlations with intrinsic parameters of galaxies in the visible and radio

From a comparison of the different parameters of warped galaxies in the radio, and especially in the visible, we find that: a) No large galaxy (large mass or radius) has been found to have high amplitude in the warp, and there is no correlation of size/mass with the degree of asymmetry of the warp. b) The disc density and the ratio of dark to luminous mass show an opposing trend: smaller values give more asymmetric warps in the inner radii (optical warps) but show no correlation with the amplitude of the warp; however, in the external radii is there no correlation with asymmetry. c) A third anticorrelation appears in a comparison of the amplitude and degree of asymmetry in the warped galaxies. Hence, it seems that very massive dark matter haloes have nothing to do with the formation of warps but only with the degree of symmetry in the inner radii, and are unrelated to the warp shape for the outermost radii. Denser discs show the same dependence.

Loop-generated bounds on changes to the graviton dispersion relation

We identify the effective theory appropriate to the propagation of massless bulk fields in brane-world scenarios, to show that the dominant low-energy effect of asymmetric warping in the bulk is to modify the dispersion relation of the effective 4-dimensional modes. We show how such changes to the graviton dispersion relation may be bounded through the effects they imply, through loops, for the propagation of standard model particles. We compute these bounds and show that they provide, in some cases, the strongest constraints on nonstandard gravitational dispersions. The bounds obtained in this way are the strongest for the fewest extra dimensions and when the extra-dimensional Planck mass is the smallest. Although the best bounds come for warped 5-D scenarios, for which the 5D Planck Mass is O(TeV), even in 4 dimensions the graviton loop can lead to a bound on the graviton speed which is comparable with other constraints.

Optical and 21 CM Observations of the Warped, Edge-On Galaxy UGC 7170

Aperture synthesis observations in the 21 cm line of H I are presented for UGC 7170, an edge-on disk galaxy with an optical warp. For a derived distance of 31.8 Mpc, we find an HI mass of 4.5 x 10^9^ M_sun_. The HI gas does not extend much beyond the stellar light, reaching only to about three exponential scale lengths of the stellar disk. The ratio of the H I mass to the dynamical mass is normal for a late-type spiral, but the mass-to-light ratio is high, M_dyn_/L_B_ = 43 in solar units, indicating that most of the mass is in a dark halo. Since we observe the rotation curve to flatten at about 1.3 scale lengths of the optical disk, the core radius of the dark halo must be comparable to the disk scale length. UGC 7170 has an asymmetric warp that bends more strongly on the southern side than on the northern side of the galaxy. This warp is evident at both optical and 21 cm wavelengths, and the similarities of the stellar and gaseous warps are consistent with a gravitational origin for the warp. The relatively small size of the halo core makes it possible to explain the warp as a gravitational bending mode of the galactic disk, if the dark halo is assumed to be slightly flattened.

The warp instability of a non-linear rotating model of disk self-gravitating systems

Abstract A model of a non-linear pulsating disc was constructed. The distribution function is given by Notation is the same as in another Nuritdinov's contribution in this issue. The warp oscillations of the model were studied. A non-stationary dispersion equation was obtained. The dependence of the critical virial ratio (2T/∣U∣)0 On the rotation parameter was found for cupola and asymmetric warp oscillations.

Comparative study of nonlinear time warping techniques in isolated word speech recognition systems

In this paper, the effects of two major design choices on the performance of an isolated word speech recognition system are examined in detail. They are: 1) the choice of a warping algorithm among the Itakura asymmetric, the Sakoe and Chiba symmetric, and the Sakoe and Chiba asymmetric, and 2) the size of the warping window to reduce computation time. Two vocabularies were used: the digits (zero, one,..., nine) and a highly confusable subset of the alphabet (b, c, d, e, g, p, t, v, z). The Itakura asymmetric warping algorithm appears to be slightly better than the other two for the confusable vocabulary. We discuss the reasons why the performance of the algorithms is vocabulary dependent. Finally, for the data used in our experiments, a warping window of about 100 ms appears to be optimal.

The shape of cooling filaments in old supernova remnants

The evolution of a filament in an old supernova remnant is investigated in two dimensions using analytical methods to determine its structure and stability and to show whether it collapses into a sheet or a cylinder. All parameters are assumed constant along the length of the feature. The cross section of the filament is found to flatten as it cools, and to degenerate into a thin sheet which is unstable to asymmetric warping disturbances. This probably leads to a number of parallel striations as the filament splits up, consistent with observations in the Cygnus Loop. The ratio of depth to width is typically 10:1, and so the feature may appear to be tubelike or a sheet, depending on perspective. The application to Vela and Puppis, IC 443, S 147, and CTB 1 is pointed out.

Are Filaments Cylindrical or Sheet-Like?

Rapid cooling and collapse in a thermally unstable medium can lead to filamentary structures that are comparable to those observed in old supernova remnants. Here, simple formulae are derived for the shape of a filament forming in this manner. The cross-sectional shape of a filament will flatten and the ratio of major to minor axes (aspect ratio) increases in proportion to the density as it becomes sheet-like. Thus the aspect ratio of observed filaments is expected to be of the same order as the temperature change during the collapse, T1/T0. In very old remnants the filaments may appear to be tubes or sheets depending on perspective with aspect ratios less than 10. This model predicts a correlation between optical morphology and the temperature of the shock-heated gas. For T1 between 105K and 106K, the thin sheet that forms is likely to split up through asymmetric warping disturbances, leading to several parallel striations, consistent with observations in the Cygnus Loop. Above 106K, the instability may cause the sheet to degenerate before it has cooled to 104K. Hence, an absence of well-defined filaments is expected near X-ray emitting regions.