We calculate the effects of frame dragging on the Galactic-Center stars. Assuming the stars are only slightly relativistic, we derive an approximation to the Kerr metric, which turns out to be a weak field Schwarzschild metric plus a frame dragging term. By numerically integrating the resulting geodesic equations, we compute the effect on keplerian elements and the kinematics. We find that the kinematic effect at pericenter passage is proportional to (a(1-e^2))^{-2}. For known Galactic-center stars it is of order 10 m/s. If observed this would provide a measurement of the spin of the black hole.
The structure, kinematics and dynamics of the Galactic stellar halo are reviewed including evidence of substructure in the spatial distribution and kinematics of halo stars. Implications for galaxy formation theory are subsequently discussed; in particular it is argued that the observed kinematics of stars in the outer Galactic halo can be used as an important constraint on viable galaxy formation scenarios.
We analyze the distribution of G and K type stars towards the Galactic poles using RAVE and ELODIE radial velocities, 2MASS photometric star counts, and UCAC2 proper motions. The combination of photometric and 3D kinematic data allows us to disentangle and describe the vertical distribution of dwarfs, sub-giants and giants and their kinematics. We identify discontinuities within the kinematics and magnitude counts that separate the thin disk, thick disk and a hotter component. The respective scale heights of the thin disk and thick disk are 225$\pm$10 pc and 1048$\pm$36 pc. We also constrain t…
Space motions are given for 38 RR Lyrae (RRL) stars and 79 blue horizontal branch (BHB) stars in a ~200 deg2 area around the North Galactic Pole (NGP) using a homogeneous distance scale consistent with (m-M)0=18.52 for the LMC. The kinematics of the 26 RRL and 52 BHB stars in the 10.4 cubic kpc volume that have Z<8 kpc are not homogeneous. Our BHB sample (like that of Sirko et al. 2004b) has a zero galactic rotation (V_phi) and roughly isotropic velocity dispersions. The RRL sample shows a definite retrograde rotation (V_phi = -95+/-29 km/s) and non-isotropic velocity dispersions. The combined…
The galactic kinematics of Mira variables derived from radial velocities, Hipparcos proper motions and an infrared period-luminosity relation are reviewed. Local Miras in the 145-200day period range show a large asymmetric drift and a high net outward motion in the Galaxy. Interpretations of this phenomenon are considered and (following Feast and Whitelock 2000) it is suggested that they are outlying members of the bulge-bar population and indicate that this bar extends beyond the solar circle.
The kinematics of galactic rings were studied with a scanning Fabry-Perot interferometer mounted in the multi-mode focal reducer SCORPIO (Afanasiev & Moiseev 2005) at the SAO RAS 6-m telescope. The analysis of the ionized gas velocity fields allows us to understand the nature of the ring formation in several galaxies. The different types of the rings in the presented objects (resonanced, collisional, polar) were caused by the various sorts of interactions: merging, head-on collisions.
A catalog of Cepheid variables is used to probe the kinematics of the Galactic disk. Radial velocities are measured for eight distant Cepheids toward l = 300; these new Cepheids provide a particularly good constraint on the distance to the Galactic center, R_0. We model the disk with both an axisymmetric rotation curve and one with a weak elliptical component, and find evidence for an ellipticity of 0.043 +/- 0.016 near the Sun. Using these models, we derive R_0 = 7.66 +/- 0.32 kpc and v_circ = 237 +/- 12 km/s. The distance to the Galactic center agrees well with recent determinations from the…
The kinematic evolution of axisymmetric magnetic fields in rotating magnetospheres of relativistic compact objects is analytically studied, based on relativistic Ohm's law in stationary axisymmetric geometry. By neglecting the poloidal flows of plasma in simplified magnetospheric models, we discuss self-excited dynamos due to the frame-dragging effect (originally pointed out by Khanna & Camenzind), and we propose alternative processes to generate axisymmetric magnetic fields against ohmic dissipation. The first process (which may be called induced excitation) is caused by the help of a backgro…
We build a stellar-dynamical model of the Milky Way barred bulge and disk, using a newly implemented adaptive particle method. The underlying mass model has been previously shown to match the Galactic near-infrared surface brightness as well as gas-kinematic observations. Here we show that the new stellar-dynamical model also matches the observed stellar kinematics in several bulge fields, and that its distribution of microlensing event timescales reproduces the observed timescale distribution of the {\it MACHO} experiment with a reasonable stellar mass function. The model is therefore an exce…
The disks of galaxies are primarily stellar systems, and fundamentally dynamical entities. Thus, to fully understand galactic disks, we must study their stellar kinematics as well as their morphologies. Observational techniques have now advanced to a point where quite detailed stellar-kinematic information can be extracted from spectral observations. This review presents three illustrative examples of analyses that make use of such information to study the formation and evolution of these systems: the derivation of the pattern speed of the bar in NGC 936; the calculation of the complete veloci…
The kinematics of jets in active galactic nuclei (QSOs, BL Lacs, Radio Galaxies and Empty Field objects) on parsec scales is being studied with Very Long Baseline Array observations at 15 GHz of a sample of more than 170 radio sources. More than 1000 images have been taken since 1994. Here we present an overview of the results of our study, including the proper motions of components in the jets, and their relationship with other source properties.
We have performed Smoothed Particle Hydrodynamic (SPH) simulations to study the response of molecular clouds in the Galactic disk to a rotating bar and their subsequent evolution in the Galactic Center (GC) region. The Galactic potential in our models is contributed by three axisymmetric components (massive halo, exponential disk, compact bulge) and a non-axisymmetric bar. These components are assumed to be invariant in time in the frame corotating with the bar. Some noticeable features such as an elliptical outer ring, spiral arms, a gas-depletion region, and a central concentration have been…
The method of constructing of rotation curve for our galactic disc is discussed. Simple physical model shows that the velocity of the Sun around the center of the Galaxy must be less than currently accepted IAU value 220 km/s. Independently obtained result for neutral hydrogen (λ= 21.1 cm) confirms the previous statement. The values of the Sun's velocity is about 110 km/s. As a consequence, the rotation curve for the disc of our Galaxy is not flat, but it is a decreasing function of the distance from the center of the Galaxy. This conclusion seems to be consistent also with other galaxies.
The predictions from a Galactic Structure and Kinematic model code are compared to the color counts and absolute proper-motions derived from the Southern Proper-Motion survey covering more than 700 $°^2$ toward the South Galactic Pole in the range $9 < B_{\rm J} \le 19$. The theoretical assumptions and associated computational procedures, the geometry for the kinematic model, and the adopted parameters are presented in detail and compared to other Galactic Kinematic models of its kind. The data to which the model is compared consists of more than 30,000 randomly selected stars, and it is best …
The kinematic properties of tidal debris from an orbiting Galactic satellite is presented, on the assumption that its central part once contained the most massive Galactic globular cluster, omega Cen. We simulate dynamical evolution of a satellite galaxy that follows the present-day and likely past orbits of omega Cen and analyze the kinematic nature of their tidal debris and randomly generated Galactic stars comprising spheroidal halo and flat disk components. It is found that the debris stars show a retrograde rotation at about -100 km/s, which may accord with a recently discovered stellar s…
We present radial velocities for approximately 40 stars in each of three optically obscured, off-axis, fields toward the Galactic bulge. Combined with the data presented by Blum et al. (1994), we now have mean radial velocities and radial velocity dispersions in four fields towards the Galactic bulge. These four fields lie nearly along an axis whose position angle from the major axis of the Galaxy is 55°. The observed kinematics generally match both Kent's (1992) axisymmetric and Zhao's (1994) barred dynamical model predictions, but are marginally better described by the latter. The velocity d…
We present a method for recovering the distribution functions of edge-on thin axisymmetric disks directly from their observable kinematic properties. The most generally observable properties of such a stellar system are the line-of-sight velocity distributions of the stars at different projected radii along the galaxy. If the gravitational potential is known, then the general two-integral distribution function can be reconstructed using the shapes of the high-velocity tails of these line-of-sight distributions. If the wrong gravitational potential is adopted, then a distribution function can s…
Recent studies of elemental abundances in the Galactic halo and in the Galactic disk have underscored the possibility to kinematically separate different Galactic subcomponents. Correlations between the galactocentric rotation velocity and various element ratios were found, providing an important means to link different tracers of star formation and metal enrichment to the Galactic components of different origin (collapse vs. accretion). In the present work we determine stellar kinematics for a sample of 124 disk stars, which we derive from their orbits based on radial velocities and proper mo…
Large samples of Field Horizontal Branch (FHB) stars make excellent tracers of the Galactic halo; by studying their kinematics, one can infer important physical properties of our Galaxy. Here we present the results of a medium-resolution spectroscopic survey of 530 FHB stars selected from the Hamburg/ESO survey. The stars have a mean distance of ~7 kpc and thus probe the inner parts of the Milky Way halo. We measure radial velocities from the spectra in order to test the model of Sommer-Larsen et al., who suggested that the velocity ellipsoid of the halo changes from radially-dominated orbits …
A quasi self-consistent model for a barred structure in the central regions of our Galaxy is used to calculate the signature of such a triaxial structure on the kinematical properties of star samples. We argue that, due to the presence of a velocity dispersion, such effects are much harder to detect in the stellar component than in the gas. It might be almost impossible to detect stellar kinematical evidence for a bar using only l-v diagrams, if there is no a priori knowledge of the potential. Therefore, we propose some test parameters that can easily be applied to observed star samples, and t…
The young star velocity field is analysed by means of a galactic model which takes into account solar motion, differential galactic rotation and spiral arm kinematics. We use two samples of Hipparcos data, one containing O- and B-type stars and another one composed of Cepheid variable stars. The robustness of our method is tested through careful kinematic simulations. Our results show a galactic rotation curve with a classical value of $A$ Oort constant for the O and B star sample ($A^{\mathrm{OB}} =$ 13.7-13.8 km s$^{-1}$ kpc $^{-1}$) and a higher value for Cepheids ($A^{\mathrm{Cep}} =$ 14.9…
We present the results of a kinematic survey of the dwarf spheroidal satellite of M31, And-IX, which appears to be the lowest surface brightness and also the faintest galaxy (M_V = -8.3) found to date. Using Keck/DEIMOS spectroscopic data, we have measured its velocity relative to M31, its velocity dispersion, and its metallicity. It exhibits a significant velocity dispersion sigma_v = 6.8+3.0-2.0km/s, which coupled with the low luminosity implies a very high mass to V-band light ratio, M/L ~ 93+120-50msun/lsun (M/L > 17msun/lsun at 99% confidence). Unless strong tidal forces have perturbed th…
The Hipparcos proper motions of 220 galactic Cepheids, together with relevant ground-based photometry, have been analysed. The effects of galactic rotation are very clearly seen. Mean values of the Oort constants, A = 14.82 +/- 0.84 km/s/kpc, and B = -12.37 +/- 0.64 km/s/kpc, and of the angular velocity of circular rotation at the Sun, Omega_0 = 27.19 +/- 0.87 km/s/kpc, are derived. Comparison of the value of A with values derived from recent radial velocity solutions confirm, within the errors, the zero-points of the PL and PLC relations derived directly from the Hipparcos trigonometrical par…
We describe a method for parameterizing two-integral distribution functions, based on triangular tesselations of the integral plane. We apply the method to the axisymmetric isotropic rotator model for the Galactic bulge of Kent~(1992), and compare the results with observations of proper motions in Baade's Window, and with radial velocity surveys. In spite of mounting evidence from surface photometry and from study of the gas kinematics that the Galactic bulge is not axisymmetric, the stellar kinematics in Baade's Window are very similar to those of an isotropic oblate rotator. Another field at…
I report on an ongoing programme of proper motion measurements in the Galactic Bulge, using HST images. As a first application, the data are used to derive the vertical gravitational acceleration on the minor axis of the Galaxy. Implications of the measurement for the flattening of the Galactic potential are discussed.
HIRES on the Keck I telescope has been used to measure the first radial velocities for stars belonging to eleven, heavily-reddened globular clusters in the direction of the inner Galaxy. The question of kinematic substructuring among the Galactic globular cluster system is investigated using an updated catalog of globular cluster distances, metallicities and velocities. It is found that the population of metal-rich globular clusters shows significant rotation at all Galactocentric radii. For the metal-rich clusters within 4 kpc of the Galactic center, the measured rotation velocity and line-of…
Nearly 400 Tycho-2 stars have been observed in a 720 square degree field in the direction of the North Galactic Pole with the high resolution echelle spectrograph ELODIE. Absolute magnitudes, effective temperatures, gravities and metallicities have been estimated, as well as distances and 3D velocities. Most of these stars are clump giants and span typical distances from 200pc to 800pc to the galactic mid-plane. This new sample, free of any kinematical and metallicity bias, is used to investigate the vertical distribution of disk stars. The old thin disk and thick disk populations are deconvol…
As part of a radial velocity survey of low Galactic latitude structures that we undertook with the 2dF spectrograph on the AAT, we present the radial velocities of more than 1500 Red Giant Branch and Red Clump stars towards the centre of the Canis Major dwarf galaxy. With a mean velocity of 72\pm7 km/s at a Heliocentric distance of 5.5 kpc and 114\pm2 km/s at 8.5 kpc, these stars present a peculiar distance -- radial velocity relation that is unlike that expected from thin or thick disc stars. Moreover, they belong to a kinematically cold population with an intrinsic dispersion that may be as …
(Abridged) The building blocks of galaxies are star clusters. These form with low-star formation efficiencies and, consequently, loose a large part of their stars that expand outwards once the residual gas is expelled by the action of the massive stars. Massive star clusters may thus add kinematically hot components to galactic field populations. This kinematical imprint on the stellar distribution function is estimated here by calculating the velocity distribution function for ensembles of star-clusters distributed as power-law or log-normal initial cluster mass functions (ICMFs). The resulti…
We consider the relationship between the total HI mass in late-type galaxies and the kinematic properties of their disks. The mass $M_HI$ for galaxies with a wide variety of properties, from dwarf dIrr galaxies with active star formation to giant low-brightness galaxies, is shown to correlate with the product $V_c R_0$ ($V_c$ is the rotational velocity, and $R_0$ is the radial photometric disks scale length), which characterizes the specific angular momentum of the disk. This relationship, along with the anticorrelation between the relative mass of HI in a galaxy and $V_c$, can be explained in…
We study the formation of disks via the cooling flow of gas within galactic haloes using smoothed particle hydrodynamics simulations. These simulations resolve mass scales of a few thousand solar masses in the gas component for the first time. Thermal instabilities result in the formation of numerous warm clouds that are pressure confined by the hot ambient halo gas. The clouds fall slowly onto the disk through non-spherical accretion from material flowing preferentially down the angular momentum axis. The rotational velocity of the infalling cold gas decreases as a function of height above th…
We re-analyse the kinematics of the system of blue horizontal branch field (BHBF) stars in the Galactic halo (in particular the outer halo), fitting the kinematics with the model of radial and tangential velocity dispersions in the halo as a function of galactocentric distance r proposed by Sommer-Larsen, Flynn & Christensen (1994), using a much larger sample (almost 700) of BHBF stars. The basic result is that the character of the stellar halo velocity ellipsoid changes markedly from radial anisotropy at the sun to tangential anisotropy in the outer parts of the Galactic halo (r greater than …
We have derived a new photographic photometry and proper motions for 20000 stars with completeness to V = 18 in the direction of galactic center at the intermediate latitude (l = 3 deg,b = 47 deg; alpha(1950)=15h 18m, delta(1950) = +02deg 16') for a 15.5 sq deg field. The combination of four glass copies of the Palomar Observatory Sky Survey (i.e. POSS 1402 E&O and POSS 1429 E&O) has been used as a first epoch for proper motion determination. The random error of the proper motions is approximately 0.''3/cen to V=17. The photometric accuracy ranges between 0.07 to 0.10 in the V, B and U bands. …
Small number statistics may heavily affect the structure of the broadening function in integrated spectra of galactic globular cluster centers. As a consequence, it is a priori unknown how closely line broadening measure- ments gauge the intrinsic velocity dispersions at the cores of these stel- lar systems. We have tackled this general problem by means of Monte Carlo simulations. An examination of the mode and the frequency distribution of the measured values of the simulations indicates that the low value measured for the velocity dispersion of M30 (Zaggia etal 1992) is likely a reliable est…
We aim at a detailed description of the kinematic properties of the old, (several Gyrs) late-type CO-absorption star population among the Galactic centre (GC) cluster stars. We applied AO-assisted, near-infrared imaging and integral-field spectroscopy using the instruments NAOS/CONICA and SINFONI at the VLT. We obtained proper motions for 5445 stars, 3D velocities for 664 stars, and acceleration limits (in the sky plane) for 750 stars. We detect for the first time significant cluster rotation in the sense of the general Galactic rotation in proper motions. Out of the 3D velocity dispersion, we…
We present recent results from a Keck study of the composition of the Galactic bulge, as well as results from the bulge Bulge Radial Velocity Assay (BRAVA). Culminating a 10 year investigation, Fulbright, McWilliam, & Rich (2006, 2007) solved the problem of deriving the iron abundance in the Galactic bulge, and find enhanced alpha element abundances, consistent with the earlier work of McWilliam & Rich (1994). We also report on a radial velocity survey of {\sl 2MASS}-selected M giant stars in the Galactic bulge, observed with the CTIO 4m Hydra multi-object spectrograph. This program is to test…
In this paper HIPPARCOS astrometric and kinematic data are used to calibrate both infrared luminosities and kinematical parameters of Long Period Variable stars (LPVs). Individual absolute K and IRAS 12 and 25 luminosities of 800 LPVs are determined and made available in electronic form. The estimated mean kinematics is analyzed in terms of galactic populations. LPVs are found to belong to galactic populations ranging from the thin disk to the extended disk. An age range and a lower limit of the initial mass is given for stars of each population. A difference of 1.3mag in K for the upper limit…
We present the kinematic properties of a tidally disrupted dwarf galaxy in the Milky Way, based on the hypothesis that its central part once contained the most massive Galactic globular cluster, omega Cen. Dynamical evolution of a self-gravitating progenitor galaxy that follows the present-day and likely past orbits of omega Cen is calculated numerically and the kinematic nature of their tidal debris is analyzed, combined with randomly generated stars comprising spheroidal halo and flat disk components. We show that the retrograde rotation of the debris stars at $\sim -100$ km/s accords with a…
We build and test Parker-wind models to apply to observations of large-scale (of order 100 pc) outflows from Active Galactic Nuclei (AGNs). These models include detailed photoionization simulations, the observed radially varying mass profile, adiabatic cooling, and approximations for clouds dragged along in the wind and the interaction of the wind with the circumnuclear ISM of the galaxy. We test this model against recent HST/STIS observations of [O III] emission-line kinematics (in particular, we test against those observed in NGC 4151, but approximately the same kinematics is observed in NGC…
We perform numerical simulations for the formation of the Galactic stellar halo, based on the currently favored cold dark matter (CDM) theory of galaxy formation. Our numerical models, taking into account both dynamical and chemical evolution processes in a consistent manner, are aimed at explaining observed structure and kinematics of the stellar halo in the context of hierarchical galaxy formation. The main results of the present simulations are summarized as follows. (1) Basic physical processes involved in the formation of the stellar halo, composed of metal-deficient stars with [Fe/H] $\l…
We report proper motion dispersions for stars in the direction of two fields of the Galactic bulge, using HST/WFPC2 images taken six years apart. Our two fields are Baade's Window (l,b)=(1.13,-3.77) and Sgr I (l,b)=(1.25 ,-2.65). Our proper motion dispersions are in good agreement with prior ground- and space-based proper motion studies in bulge fields, but in contrast to some prior studies, we do not exclude any subset of stars from our studies. In Baade's Window, we find the $l$ and $b$ proper motion dispersions are 2.9 and 2.5 mas/yr, while in Sgr I, they are 3.3 and 2.7 mas/yr, respectivel…
This paper continues the analysis of faint high latitude B stars from Martin (2004). Here we analyze the kinematics of the stars and combine them with the abundance information from the first paper to classify each one. The sample contains 31 Population I runaways, fifteen old evolved stars (including five BHB stars, three post-HB stars, a pulsating helium dwarf, and six stars of ambiguous classification), one F-dwarf, and two stars which do not easily fit in one of the other categories. No star in the sample unambiguously shows the characteristics of a young massive star formed in situ in the…
We have tested whether the simple model for the kinematics of the Galactic stellar halo (in particular the outer halo) proposed by Sommer-Larsen, Flynn and Christensen (SLFC) is physically realizable, by directly integrating particles in a 3-D model of the Galactic potential. We are able to show that the SLFC solution can be realized in terms of a distribution of particles with stationary statistical properties in phase-space. Hence, the SLFC model, which shows a notable change in the anisotropy from markedly radial at the sun to markedly tangential beyond about Galactocentric radius r=20 kpc,…
Energetics considerations imply that the broad-line region (BLR) has a high covering factor. The absence of absorption from the BLR means that the BLR has to have a flattened distribution and be seen through a polar hole. The BLR is the inward extension of the torus and they have similar geometries and covering factors. Reconciling velocity-resolved reverberation mapping, spectropolarimetry, and the increasing blueshifting of BLR lines with decreasing distance from the centre, implies that the BLR has a significant inflow component. This inflow provides the mass inflow rate needed to power the…
If a class of stars orbits the central black hole in our galaxy in short period (~ 0.1 year), high eccentricity (~ 0.9) orbits, they will experience precessions of their orbital planes induced by both relativistic frame-dragging and the quadrupolar gravity of the hole, at levels that could be as large as 10 microarcseconds per year, if the black hole is rotating faster than 1/2 of its maximum rotation rate. Astrometric observations of the orbits of at least two such stars can in principle lead to a determination of the angular momentum vector J of the black hole and its quadrupole moment Q_2. …
