Galactic Kinematics Derived From Data in the RAVE5, UCAC4, PPMXL, and Gaia TGAS Catalogs

2018

Astron. Lett.

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We have studied the simultaneous and separate solutions of the basic kinematic equations obtained using the stellar velocities calculated on the basis of data from the Gaia TGAS and RAVE5 catalogues. By comparing the values of Ω ′ 0 found by separately analyzing only the line-of-sight velocities of stars and only their proper motions, we have determined the distance scale correction factor p to be close to unity, 0.97 ± 0.04. Based on the proper motions of stars from the Gaia TGAS catalogue with relative trigonometric parallax errors less than 10% (they are at a mean distance of 226 pc), we have found the components of the group velocity vector for the sample stars relative to the Sun (U, V, W ) ⊙ = (9.28, 20.35, 7.36) ± (0.05, 0.07, 0.05) km s −1 , the angular velocity of Galactic rotation Ω 0 = 27.24 ± 0.30 km s −1 kpc −1 , and its first derivative Ω ′ 0 = −3.77 ± 0.06 km s −1 kpc −2 ; here, the circular rotation velocity of the Sun around the Galactic center is V 0 = 218 ± 6 km s −1 kpc (for the adopted distance R 0 = 8.0 ± 0.2 kpc), while the Oort constants are A = 15.07 ± 0.25 km s −1 kpc −1 and B = −12.17 ± 0.39 km s −1 kpc −1 , p = 0.98 ± 0.08. The kinematics of Gaia TGAS stars with parallax errors more than 10% has been studied by invoking the distances from a paper by Astraatmadja and Bailer-Jones that were corrected for the Lutz-Kelker bias. We show that the second derivative of the angular velocity of Galactic rotation Ω ′′ 0 = 0.864 ± 0.021 km s −1 kpc −3 is well determined from stars at a mean distance of 537 pc. On the whole, we have found that the distances of stars from the Gaia TGAS catalogue calculated using their trigonometric parallaxes do not require any additional correction factor. METHODSWe know three stellar velocity components from observations: the line-of-sight velocity V r and the two tangential velocity components V l = 4.74rµ l cos b and V b = 4.74rµ b along the Galactic longitude l and latitude b, respectively, expressed in km s −1 . Here, the coefficient 4.74 is the ratio of the number of kilometers in an astronomical unit to the number of seconds in a tropical year, and r is the stellar heliocentric distance in kpc. The proper motion components µ l cos b and µ b are expressed in mas yr −1 .

Section: Resultsmentioning

confidence: 99%

Testing the Distance Scale of the Gaia TGAS Catalogue by the Kinematic Method

2018

Astron. Lett.

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“…For some of the stars (TGAS, Tycho-Gaia Astrometric Solution) their proper motions were determined with a mean epoch difference of about 24 years with a mean error of about 0.06 mas yr −1 for the stars common to the Hipparcos catalogue (1997) and ∼mas yr −1 for the remaining stars . Using these data, various authors performed a number of important studies devoted to the kinematics of stars from the solar neighborhood (Bovy 2017;Hunt et al 2017; Bobylev and Bajkova 2017; Vityazev et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Kinematics of the Galaxy from OB Stars with Data from the Gaia DR2 Catalogue

2018

Astron. Lett.

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We have selected and analyzed a sample of OB stars with known line-of-sight velocities determined through ground-based observations and with trigonometric parallaxes and proper motions from the Gaia DR2 catalogue. Some of the stars in our sample have distance estimates made from calcium lines. A direct comparison with the trigonometric distance scale has shown that the calcium distance scale should be reduced by 13%. The following parameters of the Galactic rotation curve have been determined from 495 OB stars with relative parallax errors less than 30%: (U, V, W ) ⊙ = (8. 16, 11.19, 8.55)±(0.48, 0.56, 0.48) km s −1 , Ω 0 = 28.92 ± 0.39 km s −1 kpc −1 , Ω ′ 0 = −4.087 ± 0.083 km s −1 kpc −2 and Ω ′′ 0 = 0.703 ± 0.067 km s −1 kpc −3 , where the circular velocity of the local standard of rest is V 0 = 231 ± 5 km s −1 (for the adopted R 0 = 8.0 ± 0.15 kpc). The parameters of the Galactic spiral density wave have been found from the series of radial, V R , residual tangential, ∆V circ , and vertical, W, velocities of OB stars by applying a periodogram analysis. The amplitudes of the radial, tangential, and vertical velocity perturbations are f R = 7.1 ± 0.3 km s −1 , f θ = 6.5 ±0.4 km s −1 , and f W = 4.8 ±0.8 km s −1 , respectively; the perturbation wavelengths are λ R = 3.3±0.1 kpc, λ θ = 2.3±0.2 kpc, and λ W = 2.6±0.5 kpc; and the Sun's radial phase in the spiral density wave is (χ ⊙ ) R = −135±5 • , (χ ⊙ ) θ = −123±8 • , and (χ ⊙ ) W = −132±21 •

“…The signs of the unknowns were chosen so that rotations from the x axis to the y axis, from y to z, and from z to x are positive. Thus, the angular velocity of the Galactic rotation will be negative here, in contrast to many other studies in which the Galactic rotation was taken to be positive, for convenience [27][28][29].…”

Section: Galactic Rotation Parametersmentioning

confidence: 85%

Features of the Residual Velocity Ellipsoid of Hot Subdwarfs from the Gaia DR2 Catalog

2019

Astron. Rep.

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The evolution of the parameters of the residual velocity ellipsoid of hot subdwarfs (HSDs) with their position relative to the Galactic plane is traced, using the HSDs selected by Geier et al. from the Gaia DR2 catalog. Parameters of the Galactic rotation are determined for two |z| zones. These are used to estimate the gradient of the circular rotation velocity, V 0 , versus |z|, found to be ∆V 0 /∆|z| = −71 ± 7 km s −1 kpc −1 . The size of the residual velocity ellipsoid is (σ 1 , σ 2 , σ 3 ) = (36.1, 27.6, 22.8) ± (0.4, 0.8, 0.6) km/s for HSDs at |z| < 0.5 kpc and (σ 1 , σ 2 , σ 3 ) = (56.9, 55.8, 39.7) ± (0.9, 1.1, 0.8) km/s for HSDs at |z| ≥ 0.5 kpc. When forming the HSD residual velocities, the Galactic rotation was taken into account using individual approaches for each z zone. Parameters of the residual velocity ellipsoids for HSDs located in four plane-parallel layers are also determined. The size of the ellipsoid increases with z, and the inclination of the first axis relative to the Galactic plane also increases. This inclination is close to zero in zones close to the Galactic plane, z ∼ ±0.2 kpc, and rises to ∓12 ± 4 • for z ∼ ±0.9 kpc.