Studying Infall in Infrared Dark Clouds with Multiple HCO+ Transitions

Abstract

We investigate the infall properties in a sample of 11 infrared dark clouds (IRDCs) showing blue-asymmetry signatures in HCO${}^{+}$ J=1--0 line profiles. We used JCMT to conduct mapping observations in HCO${}^{+}$ J=4--3 as well as single-pointing observations in HCO${}^{+}$ J =3--2, towards 23 clumps in these IRDCs. We applied the HILL model to fit these observations and derived infall velocities in the range of 0.5-2.7 km s${}^{-1}$, with a median value of 1.0 km s${}^{-1}$, and obtained mass accretion rates of 0.5-14$\times$10${}^{-3}$ Msun yr${}^{-1}$. These values are comparable to those found in massive star forming clumps in later evolutionary stages. These IRDC clumps are more likely to form star clusters. HCO${}^{+}$ J =3--2 and HCO${}^{+}$ J =1--0 were shown to trace infall signatures well in these IRDCs with comparable inferred properties. HCO${}^{+}$ J=4--3, on the other hand, exhibits infall signatures only in a few very massive clumps, due to smaller opacties. No obvious correlation for these clumps was found between infall velocity and the NH3/CCS ratio.

arXiv comment22 pages, 14 figures, accepted by RAA

References in corpus (37)

• A computer program for fast non-LTE analysis of interstellar line spectra
• Competitive accretion in embedded stellar cluster
• High-Mass Star and Massive Cluster Formation in the Milky Way
• Infrared Dark Clouds: precursors to star clusters
• Global collapse of molecular clouds as a formation mechanism for the most massive stars
• A Search for Infall Motions Toward Nearby Young Stellar Objects
• The initial conditions of stellar protocluster formation. I. A catalogue of Spitzer dark clouds
• Hi-GAL, the Herschel infrared Galactic Plane Survey: photometric maps and compact source catalogues. First data release for Inner Milky Way: +68°> l > -70°
• The Properties of Massive, Dense, Clumps: Mapping Surveys of HCN and CS
• HARP/ACSIS: A submillimetre spectral imaging system on the James Clerk Maxwell Telescope
• The Circumstellar Environment of High Mass Protostellar Objects. III Evidence of Infall?
• A CH3CN and HCO+ survey towards southern methanol masers associated with star formation
• Infall through the evolution of high-mass star-forming clumps
• Indications of Inflow Motions in Regions Forming Massive Stars
• Outflow and Infall in a Sample of Massive Star Forming Regions
• Infall Signatures in a Prestellar Core embedded in the High-Mass 70 $\mu$m Dark IRDC G331.372-00.116
• Testing Larson's relationships in massive clumps
• A Molecular Line Observation toward Massive Clumps Associated with Infrared Dark Clouds
• Molecular Line Profile Fitting with Analytic Radiative Transfer Models
• Line Profiles of Cores within Clusters: I. The Anatomy of a Filament
• Line Profiles of Cores within Clusters: II Signatures of Dynamical Collapse during High Mass Star Formation
• Massive Quiescent Cores in Orion. I. Temperature Structure
• The Initial Conditions of Stellar Protocluster Formation: III. The Herschel counterparts of the Spitzer Dark Cloud catalogue
• Automated reduction of submillimetre single-dish heterodyne data from the James Clerk Maxwell Telescope using ORAC-DR
• Evidence for Inflow in High-Mass Star-Forming Clumps
• Line Profiles of Cores within Clusters. III. What is the most reliable tracer of core collapse in dense clusters?
• Discovery of Large-Scale Gravitational Infall in a Massive Protostellar Cluster
• Chemical modeling of Infrared Dark Clouds: the Role of Surface Chemistry
• Molecular line profiles as diagnostics of protostellar collapse: modelling the `blue asymmetry' in inside-out infall
• Dichotomy in the Dynamical Status of Massive Cores in Orion
• Looking for outflow and infall signatures in high mass star forming regions
• SMA observations of the W3(OH) complex: Dynamical differentiation between W3(H${}_2$O) and W3(OH)
• Kinematics of a young low-mass star forming core: Understanding the evolutionary state of the First Core Candidate L1451-mm
• Molecular Line Profiles from Contracting Dense Cores
• Infrared dark clouds on the far side of the Galaxy
• Searching for Inflow Towards Massive Starless Clump Candidates Identified in the Bolocam Galactic Plane Survey
• Infall/Expansion Velocities in the Low-Mass Dense Cores L492, L694-2, and L1521F: Dependence on Position and Molecular Tracer