The structure and kinematics of the the Galaxy thin gaseous disc outside the solar orbit

Abstract

The rotation curve of the Galaxy is generally thought to be flat. However, using radial velocities from interstellar molecular clouds, which is common in rotation curve determination, seems to be incorrect and may lead to incorrectly inferring that the rotation curve is flat indeed. Tests basing on photometric and spectral observations of bright stars may be misleading. The rotation tracers (OB stars) are affected by motions around local gravity centers and pulsation effects seen in such early type objects. To get rid of the latter a lot of observing work must be involved. We introduce a method of studying the kinematics of the thin disc of our Galaxy outside the solar orbit in a way that avoids these problems. We propose a test based on observations of interstellar CaII H and K lines that determines both radial velocities and distances. We implemented the test using stellar spectra of thin disc stars at galactic longitudes of 135{\degr} and 180{\degr}. Using this method, we constructed the rotation curve of the thin disc of the Galaxy. The test leads to the obvious conclusion that the rotation curve of the thin gaseous galactic disk, represented by the CaII lines, is Keplerian outside the solar orbit rather than flat.

33 pages, 18 figures, accepted for publication in Publications of the Astronomical Society of the Pacific, 2015. February 1

References in corpus (19)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• Rotation Curves of Spiral Galaxies
• New catalogue of optically visible open clusters and candidates
• The Milky Way's Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from Kinematics of ~2400 SDSS Blue Horizontal Branch Stars
• Astrophysical parameters of Galactic open clusters
• The Milky Way's circular velocity curve between 4 and 14 kpc from APOGEE data
• On the local dark matter density
• The local density of matter mapped by Hipparcos
• Unified Rotation Curve of the Galaxy -- Decomposition into de Vaucouleurs Bulge, Disk, Dark Halo, and the 9-kpc Rotation Dip --
• HI kinematics and dynamics of Messier 31
• Abundances and Behavior of 12CO, 13CO, and C2 in Translucent Sight Lines
• Direct Measurement of the Ratio of Carbon Monoxide to Molecular Hydrogen in the Diffuse Interstellar Medium
• 109 new Galactic open clusters
• Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood
• The BOES spectropolarimeter for Zeeman measurements of stellar magnetic fields
• High-Resolution Observations of Interstellar Ca I Absorption -- Implications for Depletions and Electron Densities in Diffuse Clouds
• Hubble Space Telescope Survey of Interstellar ^12CO/^13CO in the Solar Neighborhood
• Milky Way rotation curve from proper motions of red clump giants
• Photometric study of distant open clusters in the second quadrant: NGC 7245, King 9, King 13 and IC 166

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• Gaia-DR2 extended kinematical maps. Part I: Method and application
• Determination of the Galactic Rotation Curve from OB Stars
• The Galaxy Kinematics from OB Stars with Proper Motions from the Gaia DR1 Catalog
• Kinematics of the Galaxy from OB Stars with Data from the Gaia DR2 Catalogue
• 3-D kinematics of classical Cepheids according to Gaia, EDR3 catalog
• Chemical Composition of Young Stars in the Leading Arm of the Magellanic System
• Galaxy rotation curve from classical Cepheids
• On the intrinsic rest wavelengths of diffuse interstellar bands