Molecular-Cloud-Scale Chemical Composition I: Mapping Spectral Line Survey toward W51 in the 3 mm Band

Abstract

We have conducted a mapping spectral line survey toward the Galactic giant molecular cloud W51 in the 3 mm band with the Mopra 22 m telescope in order to study an averaged chemical composition of the gas extended over a molecular cloud scale in our Galaxy. We have observed the area of $25^{\prime }\times 30^{\prime }$, which corresponds to 39 pc $\times$ 47 pc. The frequency ranges of the observation are 85.1 - 101.1 GHz and 107.0 - 114.9 GHz. In the spectrum spatially averaged over the observed area, spectral lines of 12 molecular species and 4 additional isotopologues are identified. An intensity pattern of the spatially-averaged spectrum is found to be similar to that of the spiral arm in the external galaxy M51, indicating that these two sources have similar chemical compositions. The observed area has been classified into 5 sub-regions according to the integrated intensity of ${}^{13}$CO($J=1-0$) ($I_{{}^{13}\mathrm{CO}}$), and contributions of the fluxes of 11 molecular lines from each sub-region to the averaged spectrum have been evaluated. For most of molecular species, 50 % or more of the flux come from the sub-regions with $I_{{}^{13}\mathrm{CO}}$ from 25 K km s${}^{-1}$ to 100 K km s${}^{-1}$, which does not involve active star forming regions. Therefore, the molecular-cloud-scale spectrum observed in the 3 mm band hardly represents the chemical composition of star forming cores, but mainly represents the chemical composition of an extended quiescent molecular gas. The present result constitutes a sound base for interpreting the spectra of external galaxies at a resolution of a molecular cloud scale ($\sim 10$ pc) or larger.

arXiv commentAccepted for publication in ApJ

References in corpus (46)

• The Milky Way in Molecular Clouds: A New Complete CO Survey
• A computer program for fast non-LTE analysis of interstellar line spectra
• An eclipsing binary distance to the Large Magellanic Cloud accurate to 2 per cent
• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• Physical Conditions in Regions of Star Formation
• The ACS Nearby Galaxy Survey Treasury
• Molecular line emission in NGC1068 imaged with ALMA. I An AGN-driven outflow in the dense molecular gas
• The present-day star formation rate of the Milky-Way determined from Spitzer detected young stellar objects
• The Second Survey of the Molecular Clouds in the Large Magellanic Cloud by NANTEN I: Catalog of Molecular Clouds
• Molecular Evolution in Collapsing Prestellar Cores
• Abundances of metal-rich H II regions in M51
• The largest oxigen bearing organic molecule repository
• A 2 mm spectral line survey of the starburst galaxy NGC 253
• Abundant H2D+ in the pre-stellar core L1544
• Spatially Resolved Chemistry in Nearby Galaxies I. The Center of IC 342
• The anatomy of the Orion B Giant Molecular Cloud: A local template for studies of nearby galaxies
• The Abundance Properties of Nearby Late-Type Galaxies.I. The Data
• Trigonometric Parallax of W51 Main/South
• Star Formation in Massive Clusters via the Wilkinson Microwave Anisotropy Probe and the Spitzer Glimpse Survey
• Vibrationally Excited HCN in the Luminous Infrared Galaxy NGC 4418
• SMA/PdBI multiple line observations of the nearby Seyfert2 galaxy NGC 1068: Shock related gas kinematics and heating in the central 100pc?
• ALMA Multi-line Imaging of the Nearby Starburst Galaxy NGC 253
• Trigonometric Parallaxes of Massive Star Forming Regions: III. G59.7+0.1 and W 51 IRS2
• Organic Molecules in the Galactic Center. Hot Core Chemistry without Hot Cores
• First detections of the key prebiotic molecule PO in star-forming regions
• Lambda = 3 mm line survey of nearby active galaxies
• The Submillimeter Array 1.3 mm line survey of Arp 220
• Submillimeter Interferometry of the Luminous Infrared Galaxy NGC 4418: A Hidden Hot Nucleus with an Inflow and an Outflow
• The W51 Giant Molecular Cloud
• SMA millimeter observations of Hot Molecular Cores
• Spectral imaging of the Sagittarius B2 region in multiple 3-mm molecular lines with the Mopra telescope
• Spectroscopic observations of ices around embedded young stellar objects in the Large Magellanic Cloud with AKARI
• Toward gas exhaustion in the W51 high-mass protoclusters
• A ring/disk/outflow system associated with W51 North: a very massive star in the making
• Exploring the molecular chemistry and excitation in obscured luminous infrared galaxies: An ALMA mm-wave spectral scan of NGC 4418
• Spatially Resolved Chemistry in Nearby Galaxies II. The Nuclear Bar in Maffei 2
• Vibrationally excited HC3N in NGC 4418
• Spectral Line Survey toward Spiral Arm of M51 in the 3 mm and 2 mm Bands
• The dense gas mass fraction in the W51 cloud and its protoclusters
• Detection of vibrationally excited methyl formate in W51 e2
• Spectral Line Survey toward Molecular Clouds in the Large Magellanic Cloud
• On the chemical ladder of esters. Detection and formation of ethyl formate in the W51 e2 hot molecular core
• A Multi-Transition Study of Molecules toward NGC 1068 based on High-Resolution Imaging Observations with ALMA
• VLT/ISAAC infrared spectroscopy of embedded high-mass YSOs in the Large Magellanic Cloud: Methanol and the 3.47 micron band
• Tentative detection of ethylene glycol toward W51/e2 and G34.3+0.2
• Molecular Distribution in the Spiral Arm of M51

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