Using the Galaxy as an example, we study the effect of j x B force on the rotational curves of gas and plasma in galaxies. Acceptable model for the galactic magnetic field and plausible physical parameters are used to fit the flat rotational curve for gas and plasma based on the observed baryonic (visible) matter distribution and j x B force term in the static MHD equation of motion. We also study the effects of varied strength of the magnetic field, its pitch angle and length scale on the rotational curves. We show that j x B force does not play an important role on the plasma dynamics in the intermediate range of distances 6-12 kpc from the centre, whilst the effect is sizable for larger r (r > 15 kpc), where it is the most crucial.
Shown are the errors and difficulties of the equations used for galaxy rotation speeds in the book "Galactic Dynamics" (Binney and Tremaine). A usable and accurate set of equations is then presented. The new equations allow easy determination of galaxy mass distribution from the rotation profile with no need for dark matter or any knowledge of galaxy surface light.
It has recently been suggested that observed galaxy rotation curves can be accounted for by general relativity without recourse to dark-matter halos. Good fits have been produced to observed galatic rotation curves using this model. We show that the implied total mass is infinite, adding to the evidence opposing the hypothesis.
The environmental dependencies of the characteristics of spiral galaxy rotation curves are studied in this work. We use our large, homogeneously collected sample of 510 cluster spiral galaxy rotation curves to test the claim that the shape of a galaxy's rotation curve strongly depends on its location within the cluster, and thus presumably on the strength of the local intracluster medium and on the frequency and strength of tidal interactions with the cluster and cluster galaxies. Our data do not corroborate such a scenario, consistent with the fact that Tully-Fisher residuals are independent …
A Born-Infeld theory has been proposed in order to explain both dark matter and dark energy. We show that the approximation used to deduce the flat rotation curves in this model breaks down at large distances in a spherically symmetric configuration.
Given the dimensions (including thickness) and rotation speeds for an axisymmetric galaxy, a closed-loop iterative method is designed to find the total mass, density, and surface-mass density (SMD)distributions. There is no need for dark-matter halos. Density accuracy of course depends on the accuracy of the thickness data, but SMD and total mass are as good as the inputs of rotation speeds vs radius if reasonable estimates are made for thickness. The effects of an exponential "atmosphere" are included.
Using an outer rotation curve of the Galaxy, we explore the galactic constants and the mass of the Galaxy. We show that Θ_0 of 200 km/s is more favorable than the IAU standard value of 220 km/s, and also show that if Θ_0 is smaller than 207 km/s the rotation curve beyond 2R_0 is declining in Keplerian fashion. In the case of Θ_0= 200 km/s and R_0= 7.6 kpc, the total mass and the extent of the Galaxy inferred from the rotation curve are 2.0+/-0.3x 10^{11} M_\odot and 15 kpc, respectively. These results may significantly change the previous view of the Galaxy, that its outer region is dominated …
A scalar potential model (SPM) was developed from considerations of galaxy clusters and of redshift. The SPM is applied to HI rotation curves (RCs) and RC asymmetry of spiral galaxies. The resulting model adds the force of a scalar potential of the host galaxy and of neighboring galaxies to the Newtonian rotation velocity equation. The RC is partitioned radially into regions. The form of the equation for each parameter of each region is the same with differing proportionality constants. Integer values of each equation are determined empirically for each galaxy. Among the sample galaxies, the g…
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 profile…
We show how the temperature and the polarisation of the cosmic microwave background are affected by bulk rotation of clusters of galaxies owing to the kinetic Sunyaev-Zeldovich effect. The main effects of rotation are (i) a shift of the position of the peak of the temperature fluctuation relative to the center of the cluster by a few percent of the core radius and (ii) a tilt of the direction of the plane of linear polarisation by several degrees.
This is a speculative attempt to connect string theory with cosmological observation. Inspired by an exactly solvable model in string theory, and based on the assumption that all matter is made of strings, individual stars will couple universally to this string gauge field and execute Landau orbits, much like electrons in an external magnetic field. This three-parameter phenomenological model can adequately fit the galaxy rotation curves. The extra centripetal acceleration provided by the background field can hence account for the "missing mass" needed to sustain the high rotation speed beyond…
The S-Z effect and Faraday rotation from halos are examined over a wide mass range, an including gas condensation and magnetic field evolution. Contributions to the CMB angular power spectrum are evaluated for galaxy clusters, galaxy groups and galaxies. Smaller mass halos are found to play a more important role than massive halos for the B-mode polarisation associated with the S-Z CMB anisotropies. The B-modes from Faraday rotation dominate the secondary B-modes caused by gravitational lensing at l > 3000. Measurement of B-mode polarisation in combination with the S-Z power spectrum can poten…
The mean electromotive force in the framework of mean--field magnetohydrodynamics is found with a particular attention to the effect of a mean rotation of the fluid on the mean electromotive force. Anisotropy of the turbulence due to gradients of its intensity or its helicity are admitted. The mean magnetic field is considered to be weak enough to exclude quenching effects. Magnetic fluctuations with a zero mean magnetic field are taken into account. The Omega x J -effect works in the same way with velocity fluctuations and magnetic fluctuations. A contribution to the electromotive force conne…
Our modelling of FR I radio jets as decelerating, relativistic flows allows us to derive their orientations accurately. We present images of Faraday rotation for two of these these objects (3C 31 and NGC 315) and show that the fluctuations of rotation measure (RM) are larger in the fainter (receding) jets, as expected if the rotation occurs in the hot galaxy/group halos. The gas density is much lower in NGC 315 and the RM fluctuations are only just detectable.
The proposition that dark matter halos possess angular momentum, though widely accepted, is a theoretical prediction which has, till date, not been observationally verified. The gravi-magnetic field produced by a rotating gravitating object is possibly the only direct consequence of the angular momentum of dark matter halos. The gravitational Faraday rotation produced by the dark matter halo of our galaxy is present in all astronomical observations. A detection of the imprint of this effect on the all-sky cosmic microwave background radiation polarisation pattern would directly probe the angul…
Recent determination of the outer rotation curve of the Galaxy suggests that the total Galactic mass is likely to concentrate into a region of radius $\sim2R_0$. If this finding is correct, the previously estimated optical depth of microlensing events towards the Large Magellanic Cloud (LMC) should be correspondingly reduced. It appears that a truncated Galactic halo model instead of the standard isothermal one extending to LMC accounts naturally for the reported microlensing rate by the MACHO collaboration. Such an explanation is indeed obvious yet has been overlooked in the past.
We present a study of the rotation measure (RM) obtained from a sample of extra-galactic radio sources either embedded in or seen in projection through a sample of seven southern galaxy clusters (declination less than 30 degrees). We compare our results with those obtained previously through similar statistical studies and conclude there is a statistically significant broadening of the RM signal in galaxy clusters when compared to a control sample. Further, we concur with the findings of Clarke (2000) that the typical influence of the cluster on the RM extends to around 800 kpc from the cluste…
We construct a Galacto-Local Group rotation curve, combining the Galactic rotation curve with a diagram, where galacto-centric radial velocities of outer globular clusters and member galaxies of the Local Group are plotted against their galacto-centric distances. The high-velocity ends of this pseudo rotation curve within a radius R ~ 150 kpc are well traced by a rotation curve calculated for the NFW (Navaro, Frenk, White) and Burkert dark halo models. The NFW model indicates that the Galaxy's mass within 385 kpc, half distance to M31, is ~ 4 x 10^{11}M_{sun}. High-velocity ends of the pseudo …
The rotation velocity asymmetry v observed in spiral galaxy HI rotation curves linearly correlates with the effective potential force from the 10 closest neighboring galaxies normalized for the test particle mass and the gravitational constant. The magnitude of the potential force from a close galaxy is proportional to the luminosity of the close galaxy and inversely proportional to the square of the distance from the close galaxy to the target galaxy. The correlation coefficient is 0.99 and F test is 0.99. Also, the slope of the rotation curve in the disk region of a galaxy from rising to fla…
Rotation curves of interacting galaxies often show that velocities are either rising or falling in the direction of the companion galaxy. We seek to reproduce and analyse these features in the rotation curves of simulated equal-mass galaxies suffering a one-to-one encounter, as possible indicators of close encounters. Using simulations of major mergers in 3D, we study the time evolution of these asymmetries in a pair of galaxies, during the first passage. Our main results are: (a) the rotation curve asymmetries appear right at pericentre of the first passage, (b) the significant disturbed rota…
An effect of the differential rotation on the nonlinear electromotive force in MHD turbulence is found. It includes a nonhelical $α$ effect which is caused by a differential rotation, and it is independent of a hydrodynamic helicity. There is no quenching of this effect contrary to the quenching of the usual $α$ effect caused by a hydrodynamic helicity. The nonhelical $α$ effect vanishes when the rotation is constant on the cylinders which are parallel to the rotation axis. The mean differential rotation creates also the shear-current effect which changes its sign with the nonlinear growth of …
We present the results of a radio polarimetric study of the high-redshift radio galaxy PKS B0529-549 (z=2.575), based on high-resolution 12 mm and 3 cm images obtained with the Australia Telescope Compact Array (ATCA). The source is found to have a rest-frame Faraday rotation measure of -9600 rad m^{-2}, the largest seen thus far in the environment of a z > 2 radio galaxy. In addition, the rest-frame Faraday dispersion in the screen responsible for the rotation is calculated to be 5800 rad m^{-2}, implying rotation measures as large as -15400 rad m^{-2}. Using supporting near-IR imaging from t…
Here we briefly report on results of self-consistent numerical modeling of a differentially rotating force-free magnetosphere of an aligned rotator. We show that differential rotation of the open field line zone is significant for adjusting of the global structure of the magnetosphere to the current density flowing through the polar cap cascades. We argue that for most pulsars stationary cascades in the polar cap can not support stationary force-free configurations of the magnetosphere.
We present spatially resolved stellar rotation velocity and velocity dispersion profiles form Keck/LRIS absorption-line spectra for 25 galaxies, mostly visually classified ellipticals, in three clusters at z=0.5. We interpret the kinematical data and HST photometry using oblate axisymmetric two-integral f(E,Lz) dynamical models based on the Jeans equations. This yields good fits, provided that the seeing and observational characteristics are carefully modeled. The fits yield for each galaxy the dynamical M/L and a measure of the galaxy rotation rate. Paper II addresses the implied M/L evolutio…
EGRET gamma-ray archival data used with GALPROP software show two ringlike structures in Milky Way Plane which roughly tally with distribution of stars ([1] & references therein). To understand fully the implications of this and similar results on detailed structure and rotation curve of especially Milky Way Disk as well as rotation curves of other galaxies as derived from spatially resolved spectroscopic data-cubes, a re-examination of the basis of the connection between mass density and rotation curve is warranted. Kenneth F. Nicholson's approach [2], which uses only Newtonian dynamics & gra…
We present Hubble Space Telescope images and 2 years of optical photometry of the quadruple quasar HE0435-1223. The time delays between the intrinsic quasar variations are 14.4+/-0.8 (A-D), 8.0+/-0.8 (A-B) and 2.1+/-0.8 (A-C) days. We also observed non-intrinsic variations of ~0.1 mag/yr that we attribute to microlensing. Instead of the traditional approach of assuming a rotation curve for the lens galaxy and then deriving the Hubble constant (H_0), we assume H_0=(72+/-7) km/s/Mpc and derive constraints on the rotation curve. On the scale over which the lensed images occur (1.2"=5kpc/h=1.5R_e)…
After explaining the motivation for this article, I briefly recapitulate the methods used to determine, somewhat coarsely, the rotation curves of our Milky Way Galaxy and other spiral galaxies, especially in their outer parts, and the results of applying these methods. Recent observations and models of the very inner central parts of galaxian rotation curves are only briefly described. I then present the essential Newtonian theory of (disk) galaxy rotation curves. The next two sections present two numerical simulation schemes and brief results. Application of modified Newtonian dynamics to the…
A large luminosity--linewidth template sample is now available, improved absorption corrections have been derived, and there are a statistically significant number of galaxies with well determined distances to supply the zero point. A revised estimate of the Hubble Constant is H_0=77 +-4 km/s/Mpc where the error is the 95% probability statistical error. Systematic uncertainties are potentially twice as large.
We have obtained interferometer observations of the central region of the Sb galaxy NGC 4527 in the 12CO (J=1-0) line emission using the Nobeyama Millimeter Array. We also obtained optical (Halpha, [NII]) spectroscopy using the Okayama 188-cm reflector along the major axis. The kinematical structure and the distribution of HII regions show symmetry around the nucleus, while the distribution of molecular gas is asymmetric. The molecular-gas mass shares only 10% of the dynamical mass in the central 1 kpc radius region. Using position-velocity diagrams, we have derived a center-to-disk rotation c…
Accurate distances to stars and galaxies allow for significant tests of stellar evolution, galaxy formation and evolution and cosmology. NASA's Space Interferometry Mission (SIM) will obtain precision [1-30 microarcsec] astrometry for 10-20k objects brighter than V=20 mag. In this paper we discuss a method to determine the distance of nearby spiral galaxies using the technique of rotational parallaxes, and show that it is possible to achieve distance errors of only a few percent. With such distances at hand, it becomes possible to determine an accurate zero-point for the Tully-Fisher relation,…
The mean electromotive force (MEMF) in a rotating stratified magnetohydrodynamical turbulence is studied.Our study rests on the mean-field magnetohydrodynamics framework and $τ$ approximation. We compute the effects of the large-scale magnetic fields (LSMF), global rotation and large-scale shear flow on the different parts of the MEMF (such as $α$ - effect, turbulent diffusion, turbulent transport, etc.) in an explicit form. The influence of the helical magnetic fluctuations which stem from the small-scale dynamo is taken into account, as well. In the paper, we derive the equation governing th…
We present deep, high velocity resolution (1.6 km/s) GMRT HI as well as optical data for the faint (M_B ~ -10.9) galaxy Camelopardalis B. We find that the HI in the galaxy has a regular velocity field, consistent with rotational motion. The implied kinematical major axis is well aligned with the major axis of both the HI and optical images. Cam B is the faintest known galaxy with such relatively well behaved kinematics. From the HI velocity field we derive a rotation curve for the galaxy. The peak (inclination corrected) rotation velocity is only 7km/s, comparable to the observed velocity disp…
How has the ``fluffy'' core of the Sgr dwarf galaxy survived multiple strong shocks from the tidal force of the Galactic halo and disc since the formation of the core a Hubble time ago? A scenario that Sgr was deflected to its current orbit by the Magellanic Clouds after a rendezvous on the north Galactic pole 2-3 Gyrs ago is examined. It is shown that the conditions of the collision fix both the sense of circulation of Sgr and the LMC around the Galaxy and the slope of the Galactic rotation curve. The model argues that the two orthogonal polar circles traced by a dozen or so Galactic halo dwa…
We apply the modified acceleration law obtained from Einstein gravity coupled explaining galaxy rotation curves without exotic dark matter. Our sample of galaxies includes low surface brightness (LSB) and high surface brightness (HSB) galaxies, and an elliptical galaxy. In those cases where photometric data are available, a best fit via the single parameter (M/L)_{stars} to the luminosity of the gaseous (HI plus He) and luminous stellar disks is obtained. Additionally, a best fit to the rotation curves of galaxies is obtained in terms of a parametric mass distribution (independent of luminosit…
We present a unified rotation curve of the Galaxy re-constructed from the existing data by re-calculating the distances and velocities for a set of galactic constants R_0=8 kpc and V_0=200 km/s. We decompose it into a bulge with de Vaucouleurs-law profile of half-mass scale radius 0.5 kpc and mass 1.8 x 10^{10}M_{sun}, an exponential disk of scale radius 3.5 kpc of 6.5 x 10^{10}M_{sun}, and an isothermal dark halo of terminal velocity 200 km/s. The r^{1/4}-law fit was obtained for the first time for the Milky Way's rotation curve. After fitting by these fundamental structures, two local minima…
In this paper we discuss a dynamic flux-transport dynamo model that includes the feedback of the induced magnetic field on differential rotation and meridional flow. We consider two different approaches for the feedback: meanfield Lorentz force and quenching of transport coefficients such as turbulent viscosity and heat conductivity. We find that even strong feedback on the meridional flow does not change the character of the flux-transport dynamo significantly; however it leads to a significant reduction of differential rotation. To a large degree independent from the dynamo parameters, the s…
We derive a formalism, within the theory of linear response, for the analysis of the interaction of a satellite (the perturber) with a spherical galaxy whose equilibrium is described by a one-particle distribution function. We compute the formal expression of the force on the satellite including the self-gravity of the stars and the shift of the stellar center of mass. We apply the perturbative technique to the case of a satellite moving at high speed across a stellar system and find a natural decomposition of the force into a global component resulting from the tidal interaction and a compone…
The recently proposed Cooperstock-Tieu galaxy model claims to explain the flat rotation curves without dark matter. The purpose of this note is to show that this model is internally inconsistent and thus cannot be considered a valid solution. Moreover, by making the solution consistent the ability to explain the flat rotation curves is lost.
In this review, I will first introduce possible methods to probe the large-scale magnetic fields in our Galaxy and discuss their limitations. The magnetic fields in the Galactic halo, mainly revealed by the sky distribution of rotation measures of extragalactic radio sources, probably have a global structure of a twisted dipole field. The large-scale field structure in the Galactic disk has been most efficiently deduced from pulsar rotation measures (RMs). There has been a lot of progress since the 1980s when the magnetic field in the local area of our Galaxy was first traced by a very small s…
We present deep, high velocity resolution (~1.6 km/s) Giant Meterwave Radio Telescope (GMRT) HI 21cm synthesis images of the faint (M_B ~ -10.6) local group dwarf galaxy DDO210. We find that the HI distribution in the galaxy is not axi-symmetric, but shows density enhancements in the eastern and southern halves of the galaxy. The optical emission is lopsided with respect to the HI, most of the bright optical emission arises from the eastern half of the HI disk. The velocity field of the galaxy is however quite regular and shows a systematic large scale pattern, consistent with the rotational m…
We use the tapering effect of Halpha/[NII] rotation curves of spiral galaxies first noted by Goad & Roberts (1981) to investigate the internal extinction in disks. The scale length of exponential fits to the inner part of rotation curves depends strongly on the disk axial ratio. Preliminary modelling of the effect implies substantial opacity of the central parts of disks at a wavelength of 0.66 μ. In addition, the average kinematic scale length of rotation curves, when corrected to face--on perspective, has a nearly constant value of about 1.7 h^{-1} kpc, for all luminosity classes. The interp…
We use the rotation curves of more than 100 disk galaxies to examine whether the structure of their surrounding dark halos is consistent with the universal density profile proposed by Navarro, Frenk & White (NFW profiles). Rotation curve shape is a strong function of galaxy surface brightness: low-surface brightness galaxies (LSBs) have slowly rising rotation curves while in high-surface brightness systems the rotation speed rises sharply and stays flat or even declines beyond the optical radius. These observations are consistent with NFW halo profiles, with the possible exception of a few LSB…
Proof of the existence of a significant population of normal disk galaxies at redshift z>2 would have profound implications for theories of structure formation and evolution. We present evidence based on Keck HIRES observations that the damped Lyman-alpha absorber at z=3.15 toward the quasar Q2233+1310 may well be such an example. Djorgovski et al have recently detected the Lyman-alpha emission from the absorber, which we assume is at the systemic redshift of the absorbing galaxy. By examining the profiles of the metal absorption lines arising from the absorbing galaxy in relation to its syste…
The nonsymmetric gravitational theory predicts an acceleration law that modifies the Newtonian law of attraction between particles. For weak fields a fit to the flat rotation curves of galaxies is obtained in terms of the mass (mass-to-light ratio M/L) of galaxies. The fits assume that the galaxies are not dominated by exotic dark matter. The equations of motion for test particles reduce for weak gravitational fields to the GR equations of motion and the predictions for the solar system and the binary pulsar PSR 1913+16 agree with the observations. The gravitational lensing of clusters of gala…
Equations of motion, in cylindrical co-ordinates, for the observed rotation of gases within the gravitational potential of spiral galaxies have been derived from Carmeli's Cosmological General Relativity theory. A Tully-Fisher type relation results and rotation curves are reproduced without the need for non-baryonic halo dark matter. Two acceleration regimes are discovered that are separated by a critical accleration $\approx 4.75 \times 10^{-10}$ $m.s^{-2}$. For accelerations larger than the critical value the Newtonian force law applies, but for accelerations less than the critical value the…
We have obtained 63 rotation measures (RMs) from polarization observations of southern pulsars, of which 54 are new measurements and 3 are varied from previous values. The new pulsar RM data at high Galactic latitudes are mostly consistent with the antisymmetric RM distribution found previously. For the Galactic disc, evidence for a field reversal near the Perseus arm, and possibly another beyond it, is presented. Inside the Solar Circle, in addition to the two known field reversals in or near the Carina-Sagittartus arm and the Crux-Scutum arm, a further reversal in the Norma arm is tentativel…
Strongly lensed galaxies at high redshift provide a unique window into the early universe. We compare the internal kinematics of the strongly lensed Lyman-break galaxy (LBG) 'arc&core' at z=3.2 (the first strongly lensed z~3 LBG with the signs of rotation on sub-kiloparsec scales) with an LBG that is not gravitationally lensed, as well as with a larger sample of actively star-forming galaxies at slightly lower redshifts. All galaxies have deep rest-frame optical integral-field spectroscopy obtained with the VLT. The unlensed galaxies appear to have a larger ratio of random to bulk motion. Fiel…
We investigate the rich cluster Abell 2029 (z~0.08) using optical imaging and long-slit spectral observations of 52 disk galaxies distributed throughout the cluster field. No strong emission-line galaxies are present within ~400 kpc of the cluster center, a region largely dominated by the similarly-shaped X-ray and low surface brightness optical envelopes centered on the giant cD galaxy. However, two-thirds of the galaxies observed outside the cluster core exhibit line emission. H-alpha rotation curves of 14 cluster members are used in conjunction with a deep I band image to study the environm…
The distance modulus of a galaxy determined from Cepheids differs from its distance modulus determined from Tully-Fisher by an amount that is proportional to the galaxy's line width, W: Delta mu ~ (-1.73\pm 0.46)log(W). While a miscalibration of the slope of Tully-Fisher could in principle produce this effect, we argue that such a miscalibration is very unlikely. The other possible explanation is that the inferred Cepheid luminosity is correlated with the rotation speed v (and hence W) of its parent galaxy: L ~ v^{0.7}. This proportionality is superposed on the well-established relation betwee…
