Formation of the Musca filament: Evidence for asymmetries in the accretion flow due to a cloud-cloud collision

Abstract

Context. Dense molecular filaments are ubiquituous in the interstellar medium, yet their internal physical conditions and formation mechanism remain debated. Aims. We study the kinematics and physical conditions in the Musca filament and the Chamaeleon-Musca complex to constrain the physics of filament formation. Methods. We produced CO(2-1) isotopologue maps with the APEX telescope that cut through the Musca filament. We further study a NANTEN2 ${}^{12}$CO(1-0) map of the Musca cloud and the HI emission of the Chamaeleon-Musca complex. Results. The Musca cloud contains multiple velocity components. Radiative transfer modelling of the CO emission indicates that the Musca filament consists of a cold ($\sim$10 K), dense (n${}_{H_2}\sim$10${}^4$ cm${}^{-3}$) crest, which is best described with a cylindrical geometry. Connected to the crest, a separate gas component at T$\sim$15 K and n${}_{H_2}\sim$10${}^3$ cm${}^{-3}$ is found, the so-called strands. The filament crest has a transverse velocity gradient that is linked to the kinematics of the nearby ambient cloud. Studying the large scale kinematics, we find coherence of the asymmetric kinematics from the 50 pc HI cloud down to the Musca filament. We also report a strong [C${}^{18}$O]/[${}^{13}$CO] abundance drop by an order of magnitude from the filament crest to the strands over a distance $<$ 0.2 pc in a weak far-ultraviolet (FUV) field. Conclusions. The dense Musca filament crest is a long-lived (several crossing times), dynamic structure that can form stars in the near future because of continuous mass accretion. This mass accretion appears to be triggered by a HI cloud-cloud collision, which bends the magnetic field around dense filaments. This bending of the magnetic field is then responsible for the observed asymmetric accretion scenario of the Musca filament, which is, for instance, seen as a V-shape in the position-velocity (PV) diagram.

24 pages, 26 figures

References in corpus (26)

• Filamentary structure of star-forming complexes
• A Large Catalog of Accurate Distances to Local Molecular Clouds: The Gaia DR2 Edition
• From the warm magnetized atomic medium to molecular clouds
• Magnetically Regulated Star Formation in 3D: The Case of Taurus Molecular Cloud Complex
• On the nature of star-forming filaments: I. Filament morphologies
• Chains of dense cores in the Taurus L1495/B213 complex
• GASS: The Parkes Galactic All-Sky Survey. Update: improved correction for instrumental effects and new data release
• Formation of Magnetized Prestellar Cores with Ambipolar Diffusion and Turbulence
• The Earliest Phases of Star formation observed with Herschel (EPoS): The dust temperature and density distributions of B68
• Aspect Ratio Dependence of the Free-Fall Time for Non-Spherical Symmetries
• A closer look at the "characteristic" width of molecular cloud filaments
• Herschel's view of the large-scale structure in the Chamaeleon dark clouds
• Unveiling the Early-Stage Anatomy of a Protocluster Hub with ALMA
• Investigating the Global Collapse of Filaments Using Smoothed Particle Hydrodynamics
• The Distances to Molecular Clouds at High Galactic Latitudes based on GAIA DR2
• The evolution of Giant Molecular Filaments
• Are fibres in molecular cloud filaments real objects?
• Gas and dust temperature in pre-stellar cores revisited: New limits on cosmic-ray ionization rate
• Oxygen fractionation in dense molecular clouds
• Striations in molecular clouds: Streamers or MHD waves?
• Rotation of molecular clouds in M~51
• Thermal balance and comparison of gas and dust properties of dense clumps in the Hi-GAL survey
• Dense gas formation in the Musca filament due to the dissipation of a supersonic converging flow
• On the equilibrium of rotating filaments
• Standing in the shadow of dark gas: ALMA observations of absorption from dark CO in the molecular DNM of Chamaeleon
• Modelling the chemistry of star-forming filaments - II. Testing filament characteristics with synthetic observations

Cited by in corpus (34)

• ALMA-IMF I -- Investigating the origin of stellar masses: Introduction to the Large Program and first results
• Dust polarized emission observations of NGC 6334; BISTRO reveals the details of the complex but organized magnetic field structure of the high-mass star-forming hub-filament network
• Classification of Filament Formation Mechanisms in Magnetized Molecular Clouds
• Ionized carbon as a tracer of the assembly of interstellar clouds
• JCMT BISTRO Observations: Magnetic Field Morphology of Bubbles Associated with NGC 6334
• The SOFIA FEEDBACK Legacy Survey: Dynamics and mass ejection in the bipolar HII region RCW 36
• Velocity structure of the 50 pc-long NGC 6334 filamentary cloud: Hints of multiple compressions and their impact on the cloud properties?
• Witnessing the fragmentation of a filament into prestellar cores in Orion B/NGC 2024
• SOFIA observations of 30 Doradus: II -- Magnetic fields and large scale gas kinematics
• Physical and chemical structure of the Serpens filament -- fast formation and gravity-driven accretion
• Formation of the SDC13 Hub-Filament System: A Cloud-Cloud Collision Imprinted on The Multiscale Magnetic Field
• Unveiling the formation of the massive DR21 ridge
• Clustered star formation at early evolutionary stages. Physical and chemical analysis of the young star-forming regions ISOSS J22478+6357 and ISOSS J23053+5953
• The SEDIGISM survey: Molecular cloud morphology. I. Classification and star formation
• ALMA-IMF XIII: N${}_2$H${}^{+}$ kinematic analysis on the intermediate protocluster G353.41
• Description of turbulent dynamics in the interstellar medium: multifractal/microcanonical analysis I. Application to Herschel observations of the Musca filament
• Three-dimensional magnetic fields of molecular clouds
• On the evolution of the observed Mass-to-Length relationship for star-forming filaments
• ALMA-IMF XVIII: The assembly of a star cluster: Dense N${}_2$H${}^{+}$ (1-0) kinematics in the massive G351.77 protocluster
• On the 3D Curvature and Dynamics of the Musca filament
• A Herschel study of G214.5-1.8: a young, cold and quiescent giant molecular filament on the shell of a HI superbubble
• The "C": The large Chameleon-Musca-Coalsack cloud
• The Musca molecular cloud: The perfect "filament" is still a sheet
• Emergence of high-mass stars in complex fiber networks (EMERGE) V. From filaments to spheroids: the origin of the hub-filament systems
• Neutral hydrogen filaments in interstellar media: Are they physical?
• Constraints on the non-thermal desorption of methanol in the cold core LDN 429-C
• HP2 Survey V. Ophiuchus: Filament formation in a dispersing cloud complex
• A new phase of massive star formation? A luminous outflow cavity centred on an infrared quiet core
• Different molecular filament widths as tracers of accretion onto filaments
• Emergence of high-mass stars in complex fiber networks (EMERGE) IV. Environmental dependence of the fiber widths
• The Formation of Filaments and Dense cores in the Cocoon Nebula (IC~5146)
• ArTéMiS imaging of the filamentary infrared dark clouds G1.75-0.08 and G11.36+0.80: Dust-based physical properties of the clouds and their clumps
• Description of turbulent dynamics in the interstellar medium: Multifractal microcanonical analysis: II. Sparse filtering of Herschel observation maps and visualization of filamentary structures at different length scales
• The influence of magnetic fields in Cloud-Cloud Collisions