Detection of Dense Molecular Gas in Inter-Arm Spurs in M51

Abstract

Spiral arm spurs are prominent features that have been observed in extinction and 8$\mu$m emission in nearby galaxies. In order to understand their molecular gas properties, we used the Owens Valley Radio Observatory to map the CO(J=1--0) emission in three spurs emanating from the inner northwestern spiral arm of M51. We report CO detections from all three spurs. The molecular gas mass and surface density are M${}_{H2}\sim 3\times 10^6$ M$_{\sun}$ and ${\Sigma }_{H2}\sim$50 M$_{\sun}$ pc${}^{-2}$. Thus, relative to the spiral arms, the spurs are extremely weak features. However, since the spurs are extended perpendicular to the spiral arms for $\sim$500 pc and contain adequate fuel for star formation, they may be the birthplace for observed inter-arm HII regions. This reduces the requirement for the significant time delay that would be otherwise needed if the inter-arm star formation was initiated in the spiral arms. Larger maps of galaxies at similar depth are required to further understand the formation and evolution of these spurs and their role in star formation - such data should be forthcoming with the new CARMA and future ALMA telescopes and can be compared to several recent numerical simulations that have been examining the evolution of spiral arm spurs.

arXiv comment6 pages, 3 figures, emulate-apj format, accepted in ApJ

References in corpus (13)

• The BIMA Survey of Nearby Galaxies (BIMA SONG): I. The Radial Distribution of CO Emission in Spiral Galaxies
• High Mass, OB Star Formation in M51 : HST Halpha and Palpha Imaging
• Formation and Fragmentation of Gaseous Spurs in Spiral Galaxies
• Formation of Spiral-Arm Spurs and Bound Clouds in Vertically Stratified Galactic Gas Disks
• Molecular Gas and Star Formation in Bars of Nearby Spiral Galaxies
• Instabilities of Spiral Shocks I: Onset of Wiggle Instability and its Mechanism
• Global Modeling of Spur Formation in Spiral Galaxies
• Spurs and feathering in spiral galaxies
• Molecular Gas, Dust and Star Formation in the Barred Spiral NGC 5383
• An HST Archival Survey of Feathers in Spiral Galaxies
• Instabilities of Spiral Shocks -- II. A quasi-steady State in the multi-phase inhomogeneous ISM
• Comparative Analysis of Molecular Clouds in M31, M33 and the Milky Way
• Warm Molecular Gas in M51: Mapping the Excitation Temperature and Mass of H_2 with the Spitzer Infrared Spectrograph

Cited by in corpus (19)

• Painting a portrait of the Galactic disc with its stellar clusters
• Secular Evolution in Disk Galaxies
• Simulations of the grand design galaxy M51: a case study for analysing tidally induced spiral structure
• Dynamically Driven Evolution of the Interstellar Medium in M51
• The Bones of the Milky Way
• Star formation in Galactic spiral arms and the inter-arm regions
• The PdBI Arcsecond Whirlpool Survey (PAWS). The Role of Spiral Arms in Cloud and Star Formation
• Multi-Transition Study of M51's Molecular Gas Spiral Arms
• Nature of the Wiggle Instability of Galactic Spiral Shocks
• New Constraints on Mass-Dependent Disruption of Star Clusters in M51
• The evolution of Giant Molecular Filaments
• Evolutionary Description of Giant Molecular Cloud Mass Functions on Galactic Disks
• Galactic Spiral Shocks with Thermal Instability in Vertically Stratified Galactic Disks
• Diverse Molecular Structures Across The Whole Star-Forming Disk of M83: High fidelity Imaging at 40pc Resolution
• A new method to estimate local pitch angles in spiral galaxies: Application to spiral arms and feathers in M81 and M51
• Feathering Instability of Spiral Arms. II. Parameter Study
• PHANGS-JWST First Results: Spurring on Star Formation: JWST Reveals Localised Star Formation in a Spiral Arm Spur of NGC 628
• Wiggle Instability of Galactic Spiral Shocks: Effects of Magnetic Fields
• PHANGS-ALMA: Arcsecond CO(2-1) Imaging of Nearby Star-Forming Galaxies