The spiral pattern rotation speed of the Galaxy and the corotation radius with GAIA DR2

Abstract

In this work we revisit the issue of the rotation speed of the spiral arms and the location of the corotation radius of our Galaxy. This research was performed using homogeneous data set of young open clusters (age < 50 Myr) determined from Gaia DR2 data. The stellar astrometric membership were determined using proper motions and parallaxes, taking into account the full covariance matrix. The distance, age, reddening and metallicity of the clusters were determined by our non subjective multidimensional global optimization tool to fit theoretical isochrones to Gaia DR2 photometric data. The rotation speed of the arms is obtained from the relation between age and angular distance of the birthplace of the clusters to the present-day position of the arms. Using the clusters belonging to the Sagittarius-Carina, Local and Perseus arms, and adopting the Galactic parameters $R_0$ = 8.3 kpc and $V_0$ = 240 km\,s${}^{-1}$, we determine a pattern speed of $28.2\pm 2.1$ km\,s${}^{-1}$\,kpc${}^{-1}$, with no difference between the arms. This implies that the corotation radius is $R_c=8.51\pm 0.64$ kpc, close to the solar Galactic orbit ($R_c/R_0=1.02\pm 0.07$).

13 pages, accepted for publication in Monthly Notices of The Royal Astronomical Society,

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• Photometric study of the young open clusters IC 1442, King 21, and Trumpler 7
• Quantifying torque from the Milky Way bar using Gaia DR2
• Interarm islands in the Milky Way -- the one near the Cygnus spiral arm
• Local metallicity distribution function derived from Galactic large-scale radial iron pattern modelling