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Spiral arm amplitude variations and pattern speeds in the grand design galaxies M51, M81, and M100

1989; IOP Publishing; Volume: 343; Linguagem: Inglês

10.1086/167733

1538-4357

Bruce G. Elmegreen, P. E. Seiden, D. M. Elmegreen,

Stellar, planetary, and galactic studies

view Abstract Citations (157) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spiral-Arm Amplitude Variations and Pattern Speeds in the Grand Design Galaxies M51, M81, and M100 Elmegreen, Bruce G. ; Elmegreen, Debra Meloy ; Seiden, Philip E. Abstract The amplitudes of the spiral arms in M51, M81, and M100 have been found to oscillate smoothly around their mean radial variations with a characteristic wavelength of ~5 kpc and a relative amplitude of 100%. The phases of the spirals and the relative amplitudes of the m = 4 and m = 2 Fourier components oscillate slightly too. The absence of corresponding color variations and the symmetry of the amplitude peaks with respect to the galaxy centers suggest that the oscillations are an intrinsic part of the stellar spiral density wave. ThIs observation confirms predictions of both the modal and stellar dynamical theories of spiral structure. The radial positions of the prominent gaps in the spiral arm amplitudes are compared to the expected positions of various wave resonances. Excellent fits are obtained for M81 and M100 if the gaps are at the 4:1 resonances; then the spirals end at the outer Lindblad resonances, the inner Lindblad resonances are well shielded, and the primary star formation ridges and dust lanes are between the 4:1 and corotation resonances. Prominent interarm features and spurs also occur at the 4:1 and corotation resonances in these galaxies. The situation is similar but more complicated in M51, which requires two spiral systems to cover the disk. The best fit is for an inner spiral mode that has an outer Lindblad resonance at the position of a prominent arm intensity gap, and an outer material spiral that corotates with the companion. Then the average position of the inner Lindblad resonances of the outer material arms occurs at the same radius as the corotation resonances of the inner mode. This conjunction of resonances may explain how the companion to M51 triggered a strong spiral throughout most of the disk. Publication: The Astrophysical Journal Pub Date: August 1989 DOI: 10.1086/167733 Bibcode: 1989ApJ...343..602E Keywords: Andromeda Galaxy; Galactic Structure; Spiral Galaxies; Interstellar Gas; Orbital Resonances (Celestial Mechanics); Star Formation; Astrophysics; GALAXIES: INDIVIDUAL MESSIER NUMBER: M51; GALAXIES: INDIVIDUAL MESSIER NUMBER: M81; GALAXIES: INDIVIDUAL MESSIER NUMBER: M100; GALAXIES: INTERNAL MOTIONS; GALAXIES: STRUCTURE full text sources ADS | data products SIMBAD (4) NED (4)