The PdBI arcsecond whirlpool survey (PAWS): Multi-phase cold gas kinematic of M51
- Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)
- Observatorio Astronómico Nacional-OAN, Observatorio de Madrid Alfonso XII, 3, E-28014 Madrid (Spain)
- Institut de Radioastronomie Millimétrique, 300 Rue de la Piscine, F-38406 Saint Martin d'Hères (France)
- National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
- School of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom)
- Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)
- Instituto Radioastronomía Milimétrica, Av. Divina Pastora 7, Nucleo Central, E-18012 Granada (Spain)
The kinematic complexity and the favorable position of M51 on the sky make this galaxy an ideal target to test different theories of spiral arm dynamics. Taking advantage of the new high-resolution PdBI Arcsecond Whirlpool Survey data, we undertake a detailed kinematic study of M51 to characterize and quantify the origin and nature of the non-circular motions. Using a tilted-ring analysis supported by several other archival data sets, we update the estimation of M51's position angle (P.A. = (173 ± 3)°) and inclination (i = (22 ± 5)°). Harmonic decomposition of the high-resolution (∼40 pc) CO velocity field shows the first kinematic evidence of an m = 3 wave in the inner disk of M51 with a corotation at R {sub CR,} {sub m} {sub =} {sub 3} = 1.1 ± 0.1 kpc and a pattern speed of Ω {sub p,} {sub m} {sub =} {sub 3} ≈ 140 km s{sup –1} kpc{sup –1}. This mode seems to be excited by the nuclear bar, while the beat frequencies generated by the coupling between the m = 3 mode and the main spiral structure confirm its density-wave nature. We observe also a signature of an m = 1 mode that is likely responsible for the lopsidedness of M51 at small and large radii. We provide a simple method to estimate the radial variation of the amplitude of the spiral perturbation (V {sub sp}) attributed to the different modes. The main spiral arm structure has (V {sub sp}) = 50-70 km s{sup –1}, while the streaming velocity associated with the m = 1 and m = 3 modes is, in general, two times lower. Our joint analysis of H I and CO velocity fields at low and high spatial resolution reveals that the atomic and molecular gas phases respond differently to the spiral perturbation due to their different vertical distribution and emission morphology.
- OSTI ID:
- 22351539
- Journal Information:
- Astrophysical Journal, Vol. 784, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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