Molecular line signatures of cloud-cloud collisions

Abstract

Collisions between interstellar gas clouds are potentially an important mechanism for triggering star formation. This is because they are able to rapidly generate large masses of dense gas. Observationally, cloud collisions are often identified in position-velocity (PV) space through bridging features between intensity peaks, usually of CO emission. Using a combination of hydrodynamical simulations, time-dependent chemistry, and radiative transfer, we produce synthetic molecular line observations of overlapping clouds that are genuinely colliding, and overlapping clouds that are just chance superpositions. Molecules tracing denser material than CO, such as NH${}_3$ and HCN, reach peak intensity ratios of $0.5$ and $0.2$ with respect to CO in the `bridging feature' region of PV space for genuinely colliding clouds. For overlapping clouds that are just chance superpositions, the peak NH${}_3$ and HCN intensities are co-located with the CO intensity peaks. This represents a way of confirming cloud collisions observationally, and distinguishing them from chance alignments of unrelated material.

arXiv comment7 pages, 4 figures, MNRAS accepted

References in corpus (26)

• The Global Schmidt Law in Star Forming Galaxies
• An atomic and molecular database for analysis of submillimetre line observations
• The UMIST database for astrochemistry 2012
• The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers
• Phantom: A smoothed particle hydrodynamics and magnetohydrodynamics code for astrophysics
• Star Formation in Disk Galaxies. I. Formation and Evolution of Giant Molecular Clouds via Gravitational Instability and Cloud Collisions
• LIME - a flexible, non-LTE line excitation and radiation transfer method for millimeter and far-infrared wavelengths
• Global Star Formation Rates in Disk Galaxies and Circumnuclear Starbursts from Cloud Collisions
• Do cloud-cloud collisions trigger high-mass star formation? I. Small cloud collisions
• The Green Bank Ammonia Survey (GAS): First Results of NH3 mapping the Gould Belt
• Parsec-scale SiO Emission in an Infrared Dark Cloud
• Isolating signatures of major cloud-cloud collisions using position-velocity diagrams
• UCLCHEM: A Gas-Grain Chemical Code
• Cloud-cloud collisions and triggered star formation
• The frequency and nature of `cloud-cloud collisions' in galaxies
• Molecular clouds in the Trifid nebula M20; Possible evidence for a cloud-cloud collision in triggering the formation of the first generation stars
• Isolating signatures of major cloud-cloud collisions II: The lifetimes of broad bridge features
• Star Formation triggered by cloud-cloud collisions
• GMC Collisions as Triggers of Star Formation. V. Observational Signatures
• Environmental dependence of star formation induced by cloud collisions in a barred galaxy
• Cloud-cloud collision in the DR 21 cloud as a trigger of massive star formation
• The role of collision speed, cloud density, and turbulence in the formation of young massive clusters via cloud-cloud collisions
• Widespread SiO and CH3OH emission in Filamentary Infrared Dark Clouds
• SiO emission as a probe of Cloud-Cloud Collisions in Infrared Dark Clouds
• Synthetic line and continuum observations of simulated turbulent clouds: the apparent widths of filaments
• G133.50+9.01: A likely cloud-cloud collision complex triggering the formation of filaments, cores and a stellar cluster

Cited by in corpus (13)

• Velocity structure of the 50 pc-long NGC 6334 filamentary cloud: Hints of multiple compressions and their impact on the cloud properties?
• On the density regime probed by HCN emission
• Unraveling the observational signatures of cloud-cloud collision and hub-filament systems in W31
• AFGL 5180 and AFGL 6366S: sites of hub-filament systems at the opposite edges of a filamentary cloud
• Do simulated molecular clouds look like real ones?
• Nobeyama 45 m Local Spur CO survey. I. Giant molecular filaments and cluster formation in the Vulpecula OB association
• Structure and Kinematics of Sh2-138 -- A distant hub-filament system in the outer Galactic plane
• Gas and star kinematics in cloud-cloud collisions
• Ionized filaments and ongoing physical processes in massive star-forming sites around l = 345.5 degree
• Gas dynamics in the star forming region G18.148$-$0.283: Is it a manifestation of two colliding molecular clouds?
• Ammonia mapping observations of the Galactic infrared bubble N49: Three NH${}_3$ clumps along the molecular filament
• Low-velocity large-scale shocks in the infrared dark cloud G035.39-00.33: bubble-driven cloud-cloud collisions
• The influence of magnetic fields in Cloud-Cloud Collisions