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Exercices Astro plotting

Make a plot of the energy distribution functions B_nu, B_lam, and N_lam, which are the flux per unit frequency, the flux per unit wavelength, and the number of photons per unit wavelength, respectively, for a black body (Planck law) at a temperature of 10000 K.  

All three functions should be displayed on a convenient scale on the same plot; each function should be normalized to its maximum.  Plot against wavelength in Angstroms, covering the range 1000 to 10000 A.  Label the plot properly.  Make a hardcopy of the plot and save the resulting PostScript file.  

Optional:  write an IDL "procedure" which will compute any of the three versions of the Planck function listed above for a given wavelength vector and temperature.  Use a "keyword" input parameter to select between the three functions.  To verify  performance and documentation, let someone else try to use your procedure.

Explore the sensitivity of optical band "colors" to the temperature of a black body as follows.  Compute the Planck function B_lam for selected temperatures in the range 1000 K to 100000 K for wavelengths of 1500, 3600, 4400, 5500, 10000, and 22000 Angstroms.  (It's up to you to choose appropriate intervals for the T grid.)   Compute "colors" in the form 

 ALOG10( B_LAM[LAM(I)] / B_LAM[5500] )

for each T.  Plot these against T or LOG T on the same plot. Label the axes.  Label each curve (see the XYOUTS procedure). Make a hardcopy of the plot and save the resulting PostScript file.  Discuss the usefulness of the various combinations.  Which is most sensitive over the T range 3000-30000K appropriate for normal stars? 



IDL courses C. Morisset 2004 IA/UNAM V 2.2

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