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

Abstract

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 .

Galactic Rotation Based on OB Stars from the Gaia DR2 Catalogue

“…A new estimate of the Galactic mass, 9.8 +6. 7 −2.7 × 10 11 M ⊙ , was obtained by analyzing their space velocities. Based on a kinematic analysis of the space velocities from the Gaia DR2 catalogue, detected some manifestations of the still ongoing wobble of the Milky Way disk after the passage of the Sagittarius dwarf galaxy through it.…”

“…A sample containing ∼500 OB stars with parallaxes and proper motions from the Gaia DR2 catalogue was studied by Bobylev and Bajkova (2018b). The goal of this paper is to improve the Galactic rotation parameters and the parameters of the Galactic spiral density wave based on a huge sample of OB stars for which the trigonometric parallaxes and proper motions are available in the Gaia DR2 catalogue.…”

Galactic Rotation Parameters Based on Stars from Activ Star-Forming Regions with Data from the Gaia DR2 Catalogue

“…Having analyzed more than 50 000 stars from the TGAS catalogue (Brown et al 2016), Bobylev and Bajkova (2018) obtained an estimate of p = 0.97 ± 0.04 by this method. From open star clusters with data from the Gaia DR2 catalogue Bobylev and Bajkova (2018b) found p = 1.00 ± 0.04.…”

Kinematics of the Galaxy from a Sample of Young Open Star Clusters with Data from the Gaia DR2 Catalogue

“…Previously (Bobylev and Bajkova 2018), based on a sample of ∼500 OB stars with proper motions and parallaxes from the Gaia DR2 catalogue, we refined the Galactic rotation parameters and the parameters of the spiral density wave. One might expect that, given the necessary statistics, a kinematic analysis of OSCs using the parameters calculated from Ga-iaDR2 data will allow these results to be confirmed or even improved, because the velocities of OSCs are determined with a higher accuracy than are the velocities of single stars.…”