A CH3CN and HCO+ survey towards southern methanol masers associated with star formation

Abstract

We present the initial results of a 3-mm spectral line survey towards 83 methanol maser selected massive star-forming regions. Here we report observations of the J=5-4 and 6-5 rotational transitions of methyl cyanide (CH3CN) and the J=1-0 transition of HCO+and H13CO+. CH3CN emission is detected in 58 sources (70 %) of our sample). We estimate the temperature and column density for 37 of these using the rotational diagram method. The temperatures we derive range from 28-166 K, and are lower than previously reported temperatures, derived from higher J transitions. We find that CH3CN is brighter and more commonly detected towards ultra-compact HII (UCHII) regions than towards isolated maser sources. Detection of CH3CN towards isolated maser sources strongly suggests that these objects are internally heated and that CH3CN is excited prior to the UCHII phase of massive star-formation. HCO+ is detected towards 82 sources (99 % of our sample), many of which exhibit asymmetric line profiles compared to H13CO+. Skewed profiles are indicative of inward or outward motions, however, we find approximately equal numbers of red and blue-skewed profiles among all classes. Column densities are derived from an analysis of the HCO+ and H13CO+ line profiles. 80 sources have mid-infrared counterparts: 68 seen in emission and 12 seen in absorption as `dark clouds'. Seven of the twelve dark clouds exhibit asymmetric HCO+ profiles, six of which are skewed to the blue, indicating infalling motions. CH3CN is also common in dark clouds, where it has a 90 % detection rate.

29 pages, 16 figures. Accepted for publication in MNRAS. For associated online figures please see http://www.phys.unsw.edu.au/~crp/papers/cpurcell_2005_online.pdf

References in corpus (10)

• The SCUBA Local Universe Galaxy Survey I: First Measurements of the Submillimetre Luminosity and Dust Mass Functions
• A Search for Infall Motions Toward Nearby Young Stellar Objects
• SCUBA observations of galaxies with metallicity measurements: a new method for determining the relation between submm luminosity and dust mass
• The Population of the Galactic Plane as Seen by MSX
• Millimetre continuum observations of southern massive star formation regions. I. SIMBA observations of cold cores
• A detailed study of the rotating toroids in G31.41+0.31 and G24.78+0.08
• Star-forming protoclusters associated with methanol masers
• The HCO+ emission excess in bipolar outflows
• Indications of Inflow Motions in Regions Forming Massive Stars
• Molecular Line Profile Fitting with Analytic Radiative Transfer Models

Cited by in corpus (90)

• Star Formation in the Milky Way and Nearby Galaxies
• The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers
• A Class I and Class II Methanol Maser Survey of Extended Green Objects (EGOs) from the GLIMPSE Survey
• Chemistry in Infrared Dark Cloud Clumps: a Molecular Line Survey at 3 mm
• MALT90: The Millimetre Astronomy Legacy Team 90 GHz Survey
• The 6-GHz Multibeam Maser Survey I. Techniques
• The Millimeter Astronomy Legacy Team 90 GHz (MALT90) Pilot Survey
• G0.253+0.016: a molecular cloud progenitor of an Arches-like cluster
• The linewidth-size relationship in the dense ISM of the Central Molecular Zone
• Chemistry in Infrared Dark Clouds
• Multi-wavelength observations of Southern Hot Molecular Cores traced by methanol masers - I. Ammonia and 24 GHz Continuum Data
• Outflow and Infall in a Sample of Massive Star Forming Regions
• The IRAM-30m line survey of the Horsehead PDR: III. High abundance of complex (iso-)nitrile molecules in UV-illuminated gas
• A Molecular Line Observation toward Massive Clumps Associated with Infrared Dark Clouds
• SMA millimeter observations of Hot Molecular Cores
• Is protostellar heating sufficient to halt fragmentation? A case study of the massive protocluster G8.68-0.37
• Molecular line mapping of the giant molecular cloud associated with RCW 106 - III. Multi-molecular line mapping
• Chasing discs around O-type (proto)stars - ALMA evidence for an SiO disc and disc wind from G17.64+0.16
• Chemical complexity in the Horsehead photodissociation region
• A Search for Infall Evidence in EGOs I: the Northern Sample
• Statistical properties of 12.2 GHz methanol masers associated with a complete sample of 6.7 GHz methanol masers
• Rotation of the Warm Molecular Gas Surrounding Ultracompact HII Regions
• A MALT90 study of the chemical properties of massive clumps and filaments of infrared dark clouds
• Nitrogen fractionation in high-mass star-forming cores across the Galaxy
• Methanol Maser Associated Outflows: Detection statistics and properties
• Radiative transfer modelling of W33A MM1: 3-D structure and dynamics of a complex massive star forming region
• Initial phases of massive star formation in high infrared extinction clouds. II. Infall and onset of star formation
• Feedback from OB stars on their parent cloud: Gas exhaustion rather than gas ejection
• DNC/HNC Ratio of Massive Clumps in Early Evolutionary Stages of High-Mass Star Formation
• A multi-transition molecular line study of candidate massive young stellar objects associated with methanol masers
• 13C Isotopic Fractionation of HC3N in Star-Forming Regions -Low-Mass Star Forming Region L1527 and High-Mass Star Forming Region G28.28-0.36-
• Hot high-mass accretion disk candidates
• SiO Outflow Signatures Toward Massive Young Stellar Objects with Linearly Distributed Methanol Masers
• A new study of the chemical structure of the Horsehead nebula: the influence of grain-surface chemistry
• A Search for H2CO 6cm Emission toward Young Stellar Objects III: VLA Observations
• 6.7GHz Methanol Maser Associated Outflows: An evolutionary sequence
• Looking for outflow and infall signatures in high mass star forming regions
• High-Mass Star Formation in the Near and Far 3-KPC Arms
• The evolution of temperature and density structures of OB cluster-forming molecular clumps
• A molecular line study towards massive extended green object clumps in the southern sky: chemical properties
• The molecular distribution of the IRDC G351.77-0.51
• Simultaneous observation of water and class I methanol masers toward class II methanol maser sources
• Chemical Diversity in Three Massive Young Stellar Objects associated with 6.7 GHz CH${}_3$OH Masers
• VLA Survey of Dense Gas in Extended Green Objects: Prevalence of 25 GHz Methanol Masers
• The SOFIA Massive (SOMA) Star Formation Survey. IV. Isolated Protostars
• G30.79~FIR~10: A gravitationally bound infalling high-Mass star forming clump
• Simultaneous Survey of Water and Class I Methanol Masers toward Red MSX Sources
• Observations of Cyanopolyynes toward Four High-Mass Star-Forming Regions Containing Hot Cores
• High Resolution CO Observations of Massive Star Forming Regions
• PdBI U/LIRG Survey (PULS): Dense Molecular Gas in Arp 220 and NGC 6240
• Photodesorption of acetonitrile CH3CN in UV-irradiated regions of the Interstellar Medium: an experimental evidence
• The molecular emissions and the infall motion in the high-mass young stellar object G8.68-0.37
• Initial phases of high-mass star formation: A multiwavelength study towards the extended green object G12.42+0.50
• Probing the massive star forming environment - a multiwavelength investigation of the filamentary IRDC G333.73+0.37
• The Hot and Clumpy Molecular Cocoon Surrounding the Ultracompact HII Region G5.89-0.39
• The inflow signature toward different evolutionary phases of massive star formation
• A large, massive, rotating disk around an isolated young stellar object
• Searching for Inflow Towards Massive Starless Clump Candidates Identified in the Bolocam Galactic Plane Survey
• New detections of HC${}_5$N toward hot cores associated with 6.7 GHz methanol masers
• Sub-Alfvenic Non-Ideal MHD Turbulence Simulations with Ambipolar Diffusion: III. Implications for Observations and Turbulent Enhancement
• Chemical evolution of Red MSX Sources in the southern sky
• A Catalog of CH_3OH 7_0-6_1 A^+ Maser Sources in Massive Star-Forming Regions. II. Masers in NGC 6334F, G8.67-0.36, and M17
• Methyl Cyanide Observations Toward Massive Protostars
• Infrared dust bubble CS51 and its interaction with the surrounding interstellar medium
• The TOPGöt high-mass star-forming sample. I. Methyl cyanide emission as tracer of early phases of star formation
• Infrared Dark Clouds in the Small Magellanic Cloud?
• Inflow Motions associated with High-mass Protostellar Objects
• Analysis and test of the central-blue-spot infall hallmark
• Destruction of interstellar methyl cyanide (CH3CN) via collisions with He+ ions
• A Herschel and BIMA study of the sequential star formation near the W48A HII region
• Carbon Chain Chemistry in Hot-Core Regions around Three Massive Young Stellar Objects Associated with 6.7 GHz Methanol Masers
• HNCO: A Molecule Traces Low-velocity Shock
• A new analytic approach to infer the cosmic-ray ionization rate in hot molecular cores from HCO${}^{+}$, N${}_2$H${}^{+}$, and CO observations
• Gas Kinematics in the HII regions G351.69-1.15 and G351.63-1.25
• A study of three southern high-mass star-forming regions
• Too large and overlooked? Extended free-free emission towards massive star formation regions
• Sulfur-bearing molecules in a sample of early star-forming cores
• The physical and chemical structure of high-mass star-forming regions. Unraveling chemical complexity with the NOEMA large program "CORE"
• Ks-band (2.14 micron) imaging of southern massive star formation regions traced by methanol masers
• Multiwavelength study of low-luminosity 6.7-GHz methanol masers
• Long-term Variability of H${}_2$CO Masers in Star-forming Regions
• Physical and chemical properties of Red MSX Sources in the southern sky: HII regions
• Studying Infall in Infrared Dark Clouds with Multiple HCO+ Transitions
• A statistical study towards the high-mass BGPS clumps with the MALT90 survey
• A multi-transition molecular line study of infrared dark cloud G331.71+00.59
• Imaging Molecular Outflow in Massive Star-forming Regions with HNCO Lines
• A CO observation of the galactic methanol masers
• Erosion of a dense molecular core by a strong outflow from a massive protostar
• Methanol masers as tools to study high-mass star formation
• Simultaneous 22 GHz Water and 44 GHz Methanol Masers Survey of Ultracompact HII Regions