Discovery of the Large-Scale Vortices in the Gaseous Disk Component of the Spiral Galaxy Markarian 1040

The velocity field of the nearby Seyfert galaxy Markarian 1040 = NGC 931 has been investigated using the CIGALE instrument [1] at the prime focus of the 6-m Telescope. The Hα- image of the galaxy shows a well developed two-armed spiral pattern (Fig.1a) in the extended (size ≈ 55 kpc, assuming Ho=50 km/s Mpc) gaseous disc. In the velocity field two local velocity maxima at a distance of 20″ from the center are evident relative to the systemic velocity of 4930 ± 5 km/s (Fig.1b) which are located nonsymmetrically to the line of nodes. This results in a decrease of the rotation velocity as a function of radius two times faster than keplerian in the interval between 6 and 12 kpc at the Markarian 1040 rotation curve along the line of nodes (Fig.2). The local maximum at 1 kpc is caused by the compact bulge. The analysis of the velocity field shows strong deviations from an azimuthal symmetry in the mentioned distance interval. Velocities are subtracted from the observed radial velocity field according to an azimuthally symmetric rotation curve defined for each distance interval by the amplitude of the sinus-like dependence on the position angle. It has been found that the rotation curve determined in such a way is in agreement with the rotation curve of an exponential disc with a scale length of 7.5 kpc derived from the galaxy photometry in the continuum.