The PdBI Arcsecond Whirlpool Survey (PAWS): The Role of Spiral Arms in Cloud and Star Formation
- MPI for Astronomy, Königstuhl 17, D-69117, Heidelberg (Germany)
- MPI for Radioastronomy, Auf dem Hgel, Bonn (Germany)
- Department of Physics and Astronomy, The University of Toledo, RO 106, Toledo, OH 43606 (United States)
- School of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom)
- Observatorio Astronómico Nacional—OAN, Observatorio de Madrid Alfonso XII, 3, E-28014, Madrid (Spain)
- IRAP, 9, avenue du Colonel Roche, BP 44346-31028 Toulouse cedex 4 (France)
- Department of Astronomy, The Ohio State University, 140 W. 18th Avenue, Columbus, OH 43210 (United States)
- Institut de Radioastronomie Millimétrique, 300 Rue de la Piscine, F-38406, Saint Martin d’Hères (France)
- Instituto Radioastronomía Milimétrica, Av. Divina Pastora 7, Nucleo Central, E-18012, Granada (Spain)
- Observatoire de Paris, 61 Avenue de l’Observatoire, F-75014, Paris (France)
The process that leads to the formation of the bright star-forming sites observed along prominent spiral arms remains elusive. We present results of a multi-wavelength study of a spiral arm segment in the nearby grand-design spiral galaxy M51 that belongs to a spiral density wave and exhibits nine gas spurs. The combined observations of the (ionized, atomic, molecular, dusty) interstellar medium with star formation tracers (H ii regions, young <10 Myr stellar clusters) suggest (1) no variation in giant molecular cloud (GMC) properties between arm and gas spurs, (2) gas spurs and extinction feathers arising from the same structure with a close spatial relation between gas spurs and ongoing/recent star formation (despite higher gas surface densities in the spiral arm), (3) no trend in star formation age either along the arm or along a spur, (4) evidence for strong star formation feedback in gas spurs, (5) tentative evidence for star formation triggered by stellar feedback for one spur, and (6) GMC associations being not special entities but the result of blending of gas arm/spur cross sections in lower resolution observations. We conclude that there is no evidence for a coherent star formation onset mechanism that can be solely associated with the presence of the spiral density wave. This suggests that other (more localized) mechanisms are important to delay star formation such that it occurs in spurs. The evidence of star formation proceeding over several million years within individual spurs implies that the mechanism that leads to star formation acts or is sustained over a longer timescale.
- OSTI ID:
- 22663846
- Journal Information:
- Astrophysical Journal, Vol. 836, 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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