Astrophysics (index)

Molecular Cloud

(interstellar gas cloud including molecules)

A Molecular Cloud is a gas cloud of sufficient size and density that molecules form, particularly molecular Hydrogen (H) (aka HH or H2). They can be assumed to be cool as compared HI Region (HI) or HII Region (HII), as too high a temperature would dissociate all the molecules. Stars are typically formed in molecular clouds, where the lower Temperature leads to a higher density.

They are typically detected by observing the Luminosity (L) of Carbon Monoxide (CO) which is assumed to be present in molecular clouds and applying the CO to H2 Factor (Xco). Their temperature and density are of interest with respect to Star Formation (SF) activity/potential and can be determined from the relative strength of various molecular Spectral Lines.

Their diameter is typically in the 5 to 200 Parsec (pc) range. The larger end includes Giant Molecular Clouds (GMC) which are those on the order of a thousand solar masses and above, and can be as much as ten million solar masses.

A Magnetized Molecular Cloud is a cloud with a magnetic field. If incoming Electromagnetic Radiation (EMR) ionizes some of the cloud matter making it conductive, an external magnetic field can interact with the cloud, affecting its behavior, perhaps helping or hindering a collapse leading to star formation. A cloud's magnetism can be inferred from the Zeeman Effect, presumably observed through Zeeman-Doppler Imaging (ZDI).


(hydrogen,star formation,clouds,molecular hydrogen,gas)
http://en.wikipedia.org/wiki/Molecular_cloud

Referenced by:
Abundances
Atacama Pathfinder Experiment (APEX)
Carbon (C)
Cloud Fragmentation
Carbon Monoxide (CO)
Cold Gas
COMPLETE Survey
Dense Core Mass Function (DCMF)
DeGaS-MC
Dendrogram
Dense Core
Filament
FIRE Simulations
Gas Flow
Glycine (Gly)
Giant Molecular Cloud (GMC)
The H2O Southern Galactic Plane Survey (HOPS)
HII Region (HII)
HI Region (HI)
Hydrogen (H)
Infrared Dark Cloud (IRDC)
Interstellar Medium (ISM)
Lyman-Werner Photon
Messier 100 (M100)
Whirlpool Galaxy (M51a)
Messier 74 (M74)
Mach Number
Main Sequence Fitting
Maser
Molecular Cloud Turbulence
Metallicity (Z)
Open Cluster
Polycyclic Aromatic Hydrocarbon (PAH)
Photodissociation
Protostar
Quenched Galaxy
Rho Ophiuchi Cloud Complex
Star Formation Rate (SFR)
Star-Forming Region (SFR)
Shock Wave
Spectral Line
Star Formation (SF)
Stellar Age Determination
Stellar Association
Submillimeter Astronomy
Surface Density (Σ)
Taurus-Auriga Complex
Three Dimensional Model
Taurus Molecular Cloud 1 (TMC-1)
Toomre Q Parameter (Q)
T-Tauri Star (TTS)
Virial Parameter
CO to H2 Factor (Xco)

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