CO-0.30-0.07: A Peculiar Molecular Clump with an Extremely Broad Velocity Width

Abstract

The high velocity dispersion compact cloud CO-0.30-0.07 is a peculiar molecular clump discovered in the central moleculr zone of the Milky Way, which is characterized by its extremely broad velocity emissions ($\sim 145\mathrm{km}{\mathrm{s}}^{-1}$) despite the absence of internal energy sources. We present new interferometric maps of the cloud in multiple molecular lines in frequency ranges of 265--269 GHz and 276--280 GHz obtained using the Sumbmillimeter Array, along with the single-dish images previously obtained with the ASTE 10-m telescope. The data show that the characteristic broad velocity emissions are predominantly confined in two parallel ridges running through the cloud center. The central ridges are tightly anti-correlated with each other in both space and velocity, thereby sharply dividing the entire cloud into two distinct velocity components (+15 km s${}^{-1}$ and +55 km s${}^{-1}$). This morphology is consistent with a model in which the two velocity components collide with a relative velocity of 40 $\mathrm{km}{\mathrm{s}}^{-1}$ at the interface defined by the central ridges, although an alternative explanation with a highly inclined expanding-ring model is yet to be fully invalidated. We have also unexpectedly detected several compact clumps ($\lesssim 0.1$pc in radius) likely formed by shock compression. The clumps have several features in common with typical star-forming clouds: high densities ($10^{6.5-7.5}\mathrm{c}{\mathrm{m}}^{-3}$), rich abundances of hot-core-type molecular species, and relatively narrow velocity widths apparently decoupled from the furious turbulence dominating the cloud. The cloud CO-0.30-0.07 is possibly at an early phase of star formation activity triggered by the shock impact.

29 pages, 10 figures, accepted for publication in ApJ

References in corpus (10)

• Molecular clouds towards RCW 49 and Westerlund 2; Evidence for cluster formation triggered by cloud-cloud collision
• Organic Molecules in the Galactic Center. Hot Core Chemistry without Hot Cores
• Turbulence sets the initial conditions for star formation in high-pressure environments
• A Chandra Catalog of X-ray Sources in the Central 150 pc of the Galaxy
• G0.253+0.016: A centrally condensed, high-mass protocluster
• Cosmic-Ray Heating of Molecular Gas in the Nuclear Disk: Low Star Formation Efficiency
• Coupling the dynamics and the molecular chemistry in the Galactic center
• Diversity of chemistry and excitation conditions in the high-mass star forming complex W33
• ALMA view of G0.253+0.016: Can cloud-cloud collision form the cloud?
• ALMA Observations of the IRDC Clump G34.43+00.24 MM3: 278 GHz Class I Methanol Masers

Cited by in corpus (8)

• Search for Gamma-Ray Emission from DES Dwarf Spheroidal Galaxy Candidates with Fermi-LAT Data
• Indication of Another Intermediate-mass Black Hole in the Galactic Center
• The Fifth Candidate for an Intermediate-mass Black Hole in the Galactic Center
• HCN $J$=4-3, HNC $J$=1-0, ${\mathrm{H}}^{13}\mathrm{CN}$ $J$=1-0, and $\mathrm{H}{\mathrm{C}}_3\mathrm{N}$ $J$=10-9 Maps of Galactic Center Region I: Spatially-Resolved Measurements of Physical Conditions and Chemical Composition
• ALMA Images of the Host Cloud of the Intermediate-mass Black Hole Candidate CO-0.40-0.22$^* : No Evidence for Cloud-Black Hole Interaction, but Evidence for a Cloud-Cloud Collision
• Identifying Bound Stellar Companions to Kepler Exoplanet Host Stars Using Speckle Imaging
• Atomic Carbon in the Central Molecular Zone of the Milky Way : Possible Cosmic-ray Induced Chemistry or Time-Dependent Chemistry Associated with SNR Sagittarius A East
• HCN $J$=4-3, HNC $J$=1-0, ${\mathrm{H}}^{13}\mathrm{CN}$ $J$=1-0, and $\mathrm{H}{\mathrm{C}}_3\mathrm{N}$ $J$=10-9 Maps of Galactic Center Region II.: Physical Properties of Dense Gas Clumps and Probability of Star Formation