A. S. Rastorguev

Kinematic parameters of young subsystems and the galactic rotation curve

We analyze the space velocities of blue supergiants, long-period Cepheids, and young open star clusters (OSCs), as well as the H I and H II radial-velocity fields by the maximum-likelihood method. The distance scales of the objects are matched both by comparing the first derivatives of the angular velocity Ω′ determined separately from radial velocities and proper motions and by the statistical-parallax method. The former method yields a short distance scale (for R0=7.5 kpc, the assumed distances should be increased by 4%), whereas the latter method yields a long distance scale (for R0=8.5 kpc, the assumed distances should be increased by 16%). We cannot choose between these two methods. Similarly, the distance scale of blue supergiants should be shortened by 9% and lengthened by 3%, respectively. The H II distance scale is matched with the distance scale of Cepheids and OSCs by comparing the derivatives Ω′ determined for H II from radial velocities and for Cepheids and OSCs from space velocities. As a result, the distances to H II regions should be increased by 5% in the short distance scale. We constructed the Galactic rotation curve in the Galactocentric distance range 2–14 kpc from the radial velocities of all objects with allowance for the difference between the residual-velocity distributions. The axial ratio of the Cepheid+OSC velocity ellipsoid is well described by the Lindblad relation, while σu≈σv for gas. The following rotation-curve parameters were obtained: Ω0=(27.5±1.4) km s−1 kpc−1 and A=(17.1±0.5) km s−1 kpc−1 for the short distance scale (R0=7.5 kpc); and Ω0=(26.6±1.4) km s−1 kpc−1 and A=(15.4±0.5) km s−1 kpc−1 for the long distance scale (R0=8.5 kpc). We propose a new method for determining the angular velocity Ω0 from stellar radial velocities alone by using the Lindblad relation. Good agreement between the inferred Ω0 and our calculations based on space velocities suggests that the Lindblad relation holds throughout the entire sample volume. Our analysis of the heliocentric velocities for samples of young objects reveals noticeable streaming motions (with a velocity lag of ∼7 km s−1 relative to the LSR), whereas a direct computation of the perturbation amplitudes in terms of the linear density-wave theory yields a small amplitude for the tangential perturbations.

RR Lyrae variables: visual and infrared luminosities, intrinsic colours and kinematics

We use UCAC4 proper motions and WISE W1-band apparent magnitudes intensity-mean for almost 400 field RR Lyrae variables to determine the parameters of the velocity distribution of Galactic RR Lyrae population and constrain the zero points of the metallicity- relation and those of the period-metallicity- -band and period-metallicity- -band luminosity relations via statistical parallax. We find the mean velocities of the halo- and thick-disc RR Lyrae populations in the solar neighbourhood to be (U0(Halo), V0(Halo), W0(Halo)) = (-7 +/- 9, -214 +/- 10, -10 +/- 6) km/s and (U0(Disc), V0(Disc), W0(Disc)) =(-13 +/- 7, -37 +/- 6, -17 +/- 4) km/s, respectively, and the corresponding components of the velocity-dispersion ellipsoids, (sigma VR(Halo), sigma Vphi(Halo), sigma Vtheta(Halo)) = (153 +/- 9, 101 +/- 6, 96 +/- 5) km/s and (sigma VR(Disc), sigma Vphi(Disc), sigma Vtheta(Disc)) = (46 +/- 7, 37 +/- 5, 27 +/- 4) km/s, respectively. The fraction of thick-disc stars is estimated at 0.22 +/- 0.03. The corrected IR period-metallicity-luminosity relations are = -0.769 +0.088 [Fe/H]- 2.33 mathoprm log PF and = -0.825 + 0.088 [Fe/H] -2.33 mathoprm log PF, and the optical metallicity-luminosity relation, [Fe/H]- , is = +1.094 + 0.232 [Fe/H], with a standard error of +/- 0.089, implying an LMC distance modulus of 18.32 +/- 0.09, a solar Galactocentric distance of 7.73 +/- 0.36 kpc, and the M31 and M33 distance moduli of DM(M31) = 24.24 +/- 0.09 (D = 705 +/- 30 kpc) and DM(M33) = 24.36 +/- 0.09 (D = 745 +/- 31 kpc), respectively. Extragalactic distances calibrated with our RR Lyrae star luminosity scale imply a Hubble constant of ~80 km/s/Mpc. Our results suggest marginal prograde rotation for the population of halo RR Lyraes in the Milky Way.

Trigonometric parallaxes and a kinematically adjusted distance sale for OB associations

By directly comparing the photometric distances of Blaha and Humphreys (1989) (BH) to OB associations and field stars with the corresponding Hipparcos trigonometric parallaxes, we show that the BH distance scale is overestimated, on average, by 10–20%. This result is independently corroborated by applying the rigorous statistical-parallax method and its simplified analog (finding a kinematically adjusted rotation-curve solution from radial velocities and proper motions) to a sample of OB associations. These two methods lead us to conclude that the BH distance scale for OB associations should be shrunk, on average, by 11±6 and 24±10%, respectively. Kinematical parameters have been determined for the system of OB associations: u0 = 8.2 ± 1.3 km s−1, v0 = 11.9 ± 1.1 km s−1, w0 = 9.5 ± 0.9 km s−1, σu = 8.2 ± 1.1 km s−1, σv = 5.8 ± 0.8 km s−1, σw = 5.0 ± 0.8 km s−1, Ω0 = 29.1 ± 1.0 km s−1 kpc−1, Ω0′ = −4.57 ± 0.20 km s−1 kpc−2, and Ω0″ = 1.32 ± 0.14 km s−1 kpc−3. The distance scale for OB associations reduced by 20% matches the short Cepheid distance scale (Berdnikov and Efremov 1985; Sitnik and Mel’nik 1996). Our results are a further argument for the short distance scale in the Universe.

Periodic pattern in the residual velocity field of OB-Associations

An analysis of the residual-velocity field of OB associations within 3 kpc of the Sun has revealed periodic variations in the radial residual velocities along the Galactic radius vector with a typical scale length of λ = 2.0 ± 0.2 kpc and a mean amplitude of fR = 7 ± 1 km s−1. The fact that the radial residual velocities of almost all OB associations in rich stellar-gas complexes are directed toward the Galactic center suggests that the solar neighborhood under consideration is within the corotation radius. The azimuthal-velocity field exhibits a distinct periodic pattern in the 0°<l<180° region, where the mean azimuthal-velocity amplitude is fθ = 6 ± 2 km s−1. There is no periodic pattern of the azimuthal-velocity field in the 180°<l<360° region. The locations of the Cygnus arm, as well as the Perseus arm, inferred from an analysis of the radial-and azimuthal-velocity fields coincide. The periodic patterns of the residual-velocity fields of Cepheids and OB associations share many common features.

BINARY PROPERTIES FROM CEPHEID RADIAL VELOCITIES (CRaV)

We have examined high accuracy radial velocities of Cepheids to determine the binary frequency. The data are largely from the CORAVEL spectrophotometer and the Moscow version, with a typical uncertainty of

SPIRAL-VORTEX STRUCTURE IN THE GASEOUS DISKS OF GALAXIES

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Mid-infrared period–luminosity relations for globular cluster RR Lyrae

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Galactic masers: Kinematics, spiral structure and the disk dynamic state

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Classical Cepheids and the spiral structure of the milky way

, and a time span from 1 to 20 years. A systemic velocity was obtained by removing the pulsation component using a high order Fourier series. From this data we have developed a list of stars showing no orbital velocity larger than

Classical Cepheids in the Galactic outer ring R1R ′2

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