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Optical depth in astrophysics refers to a specific level of transparency.Optical depth and actual depth, and respectively, can vary widely depending on the absorptivity of the astrophysical environment.
In astronomy, the curve of growth describes the equivalent width of a spectral line as a function of the column density of the material from which the spectral line is observed. [ 1 ] Shape
A special type of area density is called column density (also columnar mass density or simply column density), denoted ρ A or σ. It is the mass of substance per unit area integrated along a path; [ 1 ] It is obtained integrating volumetric density ρ {\displaystyle \rho } over a column: [ 2 ] σ = ∫ ρ d s . {\displaystyle \sigma =\int \rho ...
The density as a function of elevation is = / (), where is the polytropic exponent (or polytropic index). The air mass integral for the polytropic model does not lend itself to a closed-form solution except at the zenith, so the integration usually is performed numerically.
ρ 0 is the density of air at sea level; H is the scale height of the atmosphere; z is the height in question; The optical depth of a plane parallel cloud layer is given by [3] = [] / where: Q e is the extinction efficiency; L is the liquid water path
The Lockman Hole is located at about RA 10h 45m, Dec. +58° and is defined by a region of low neutral hydrogen gas and dust column density. [3] Column density is a commonly used measure in astronomy for the quantity of a given chemical element or molecule in a certain direction. In this region, the typical column density of neutral hydrogen is ...
Column number density is a kind of areal density, the number or count of a substance per unit area, obtained integrating volumetric number density along a vertical path: ′ =. It's related to column mass density , with the volumetric number density replaced by the volume mass density.
the column density of squared electron number density. Exceptionally dense nebulae can become optically thick at centimetre wavelengths: these are just-formed and so both rare and small ('Ultra-compact H II regions')