ALMA Observations of a Quiescent Molecular Cloud in the Large Magellanic Cloud

Abstract

We present high-resolution (sub-parsec) observations of a giant molecular cloud in the nearest star-forming galaxy, the Large Magellanic Cloud. ALMA Band 6 observations trace the bulk of the molecular gas in ${}^{12}$CO(2-1) and high column density regions in ${}^{13}$CO(2-1). Our target is a quiescent cloud (PGCC G282.98-32.40, which we refer to as the "Planck cold cloud" or PCC) in the southern outskirts of the galaxy where star-formation activity is very low and largely confined to one location. We decompose the cloud into structures using a dendrogram and apply an identical analysis to matched-resolution cubes of the 30 Doradus molecular cloud (located near intense star formation) for comparison. Structures in the PCC exhibit roughly 10 times lower surface density and 5 times lower velocity dispersion than comparably sized structures in 30 Dor, underscoring the non-universality of molecular cloud properties. In both clouds, structures with relatively higher surface density lie closer to simple virial equilibrium, whereas lower surface density structures tend to exhibit super-virial line widths. In the PCC, relatively high line widths are found in the vicinity of an infrared source whose properties are consistent with a luminous young stellar object. More generally, we find that the smallest resolved structures ("leaves") of the dendrogram span close to the full range of line widths observed across all scales. As a result, while the bulk of the kinetic energy is found on the largest scales, the small-scale energetics tend to be dominated by only a few structures, leading to substantial scatter in observed size-linewidth relationships.

arXiv commentAccepted by ApJ; 21 pages in AASTeX two-column style

References in corpus (47)

• Astropy: A Community Python Package for Astronomy
• The CO-to-H2 Conversion Factor
• Density, Velocity, and Magnetic Field Structure in Turbulent Molecular Cloud Models
• Interpreting Spectral Energy Distributions from Young Stellar Objects. II. Fitting observed SEDs using a large grid of pre-computed models
• Spitzer Survey of the Large Magellanic Cloud, Surveying the Agents of a Galaxy's Evolution (SAGE) I: Overview and Initial Results
• Re-examining Larson's Scaling Relationships in Galactic Molecular Clouds
• Structural Analysis of Molecular Clouds: Dendrograms
• The CO-to-H2 Conversion Factor From Infrared Dust Emission Across the Local Group
• The global dust SED: Tracing the nature and evolution of dust with DustEM
• Molecular Cloud Evolution II. From cloud formation to the early stages of star formation in decaying conditions
• The Hubble Constant
• Bias-free Measurement of Giant Molecular Cloud Properties
• The Equilibrium State of Molecular Regions in the Outer Galaxy
• Accretion-Driven Turbulence as Universal Process: Galaxies, Molecular Clouds, and Protostellar Disks
• What controls star formation in the central 500 pc of the Galaxy?
• The Second Survey of the Molecular Clouds in the Large Magellanic Cloud by NANTEN I: Catalog of Molecular Clouds
• The Magellanic Mopra Assessment (MAGMA). I. The Molecular Cloud Population of the Large Magellanic Cloud
• Gravity or Turbulence? The velocity dispersion-size relation
• What Drives the Expansion of Giant HII Regions?: A Study of Stellar Feedback in 30 Doradus
• ALMA Reveals the Molecular Medium Fueling the Nearest Nuclear Starburst
• The link between turbulence, magnetic fields, filaments, and star formation in the Central Molecular Zone cloud G0.253+0.016
• A Comparative Study of Giant Molecular Clouds in M51, M33 and the Large Magellanic Cloud
• Dust and Gas in the Magellanic Clouds from the HERITAGE Herschel Key Project. I. Dust Properties and Insights into the Origin of the Submm Excess Emission
• Turbulent Driving Scales in Molecular Clouds
• Comparing molecular gas across cosmic time-scales: the Milky Way as both a typical spiral galaxy and a high-redshift galaxy analogue
• The linewidth-size relationship in the dense ISM of the Central Molecular Zone
• Revealing the physical properties of molecular gas in Orion with a large scale survey in J=2-1 lines of 12CO, 13CO and C18O
• The Global Evolution of Giant Molecular Clouds II: The Role of Accretion
• Physical Properties of Giant Molecular Clouds in the Large Magellanic Cloud
• Giant Molecular Clouds in M64
• The Virial Balance of Clumps and Cores in Molecular Clouds
• Interstellar Turbulence: II. Energy Spectra of Molecular Regions in the Outer Galaxy
• Graph-based interpretation of the Molecular Interstellar Medium Segmentation
• ALMA Resolves 30 Doradus: Sub-parsec Molecular Cloud Structure Near the Closest Super-Star Cluster
• A supersonic turbulence origin of Larson's laws
• Abundances and Isotope Ratios in the Magellanic Clouds: The Star Forming Environment of N113
• Does External Pressure Explain Recent Results for Molecular Clouds?
• Opacity broadening and interpretation of suprathermal CO linewidths: Macroscopic Turbulence and Tangled Molecular Clouds
• The Effect of Projection on Derived Mass-Size and Linewidth-Size Relationships
• Do Giant Molecular Clouds Care About the Galactic Structure?
• The Relationship Between Molecular Gas, HI, and Star Formation in the Low-Mass, Low-Metallicity Magellanic Clouds
• The Varying Mass Distribution of Molecular Clouds Across M83
• The Elongations and Supersonic Motions of Molecular Clouds
• What sets the massive star formation rates and efficiencies of giant molecular clouds?
• Dense Clumps in Giant Molecular Clouds in the Large Magellanic Cloud: Density and Temperature Derived from ${}^{13}$CO($J=3-2$) Observations
• Angular Momentum in Giant Molecular Clouds. II. M33
• The location, clustering, and propagation of massive star formation in giant molecular clouds

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• An Unbiased CO Survey Toward the Northern Region of the Small Magellanic Cloud with the Atacama Compact Array. II. CO Cloud Catalog
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• Tracing the Formation of Molecular Clouds in a Low-Metallicity Galaxy: A HI Narrow Self-Absorption Survey of the Large Magellanic Cloud
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