Katz et al. Respond

Mapping the Galactic disc with the LAMOST and Gaia red clump sample: II. 3D asymmetrical kinematics of mono-age populations in the disc between 6–14 kpc

“…The Milky Way's non-axisymmetric kinematics have also been mapped with data from Gaia DR2 (López-Corredoira & Sylos Labini 2019; Katz et al 2018). Gaia DR2 provides unprecedented accuracy proper motions, positions, parallaxes, and line-of-sight velocities for 7.2 million stars brighter than G RV S = 12 mag (Lindegren et al 2018), with this, Katz et al (2018) showed detailed 3D kinematics and asymmetries.…”

“…The Milky Way's non-axisymmetric kinematics have also been mapped with data from Gaia DR2 (López-Corredoira & Sylos Labini 2019; Katz et al 2018). Gaia DR2 provides unprecedented accuracy proper motions, positions, parallaxes, and line-of-sight velocities for 7.2 million stars brighter than G RV S = 12 mag (Lindegren et al 2018), with this, Katz et al (2018) showed detailed 3D kinematics and asymmetries. Some similar results are also presented by Wang et al (2018a), who found that Galactic outer disc stars in the range of Galactocentric distance between R = 8 and 13 kpc and vertical position between Z = −2 and 2 kpc exhibit asymmetrical motions in the Galactocentric radial, azimuthal, and vertical directions before Gaia DR2.…”

“…For the stars with available radial heliocentric velocities (7 224 631 sources), the parallax error is less than 100% for 7 103 123 of them. The Radial Velocity Spectrometer collects mediumresolution spectra with R 11700 which cover the wavelength range 845-872 nm centered on the calcium triplet region (Gaia Collaboration 2018; Katz et al 2018;López-Corredoira & Sylos Labini 2019). The sources are nominally brighter than 12 mag in the G RV S photometric band.…”

“…3. RECONSTRUCTING GAIA DR2 WORK We reconstruct recent Katz et al (2018) work by using stars in common between LAMOST and Gaia in Fig. 3.…”

“…For example, Siebert et al (2011) found a radial velocity gradient in the direction of the Galactic center by using RAVE (Kunder et al 2017) red clump stars. Many diagonal ridge features were found in the R − V rot map, the locations of which were compared with the locations of the spiral arms and the expected outer Lindblad resonance of the Galactic bar (Kawata et al 2018). Some possible mechanisms such as the Galactic bar's outer Lindblad resonance, perturbations due to the bar or spiral arms (Denhen 2000;Fux et al 2001;Quillen & Minchev 2005), by external minor mergers such as the Sagittarius dwarf galaxy passing by, or by interaction with the Magellanic Clouds (Gómez, Minchev & Villalobos 2012;Gómez et al 2012;Minchev et al 2009Minchev et al , 2010 are proposed for these in-plane non-axisymmetries.…”