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Homework Help: Gaussian emission lines

  1. Nov 29, 2011 #1


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    1. The problem statement, all variables and given/known data
    The spectroscopic observation of an interstellar gas cloud shows emission lines H (λ=6563 A), Hβ λ=4862 A) e OI (λ=1304 A), each one with a gaussian profile of the kind:

    [itex] g(\nu)=A e^[-\frac{(\nu-\nu_0)^2}{2\sigma^2}] [/itex]

    Per Hα si osserva [itex]σ_{Hα} = 1.2 \times 10^{10} Hz[/itex].
    Supposing that gas is in thermodynamic equilibrium at a temperature T, uniform in the whole cloud, determine:

    1) the T value;
    2) the [itex]σ_{OI}[/itex] value;
    3) the Full Width at Half Maximum of the Hβ line.

    2. Relevant equations

    The Doppler broadening [itex]Δ\nu/\nu = v/c[/itex].
    The Virial temperature: [itex] 1/2 m v^2 = 3/2 k T[/itex].

    3. The attempt at a solution

    Regarding only the first point, can I proceed with the above-mentioned formulas?
    If yes, I find a temperature of T≈2500 K, that is an order of magnitude higher then the typical temperature of interstellar clouds...
    If not (and this is), why not?

    Thanks in advance :)

    PS: I don't like this formulas editor et all :D
  2. jcsd
  3. Dec 3, 2011 #2


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    Any ideas please?
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