en:praktikum:ism

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision		 Previous revision
Last revisionBoth sides next revision
en:praktikum:ism [2016/10/07 21:56] – [Evaluation: Metal abundances in the interstellar gas] rhainichen:praktikum:ism [2016/10/08 00:06] – rhainich
Line 1: Line 1:
 ====== D1 - Interstellar absorption spectroscopy ====== ====== D1 - Interstellar absorption spectroscopy ======
  
-==== Task ====+===== Task =====
  
 A UV spectrum of Delta Orionis (a nearby star) is given, showing several interstellar absorption lines A UV spectrum of Delta Orionis (a nearby star) is given, showing several interstellar absorption lines
Line 9: Line 9:
 further physical properties are deduced.  further physical properties are deduced. 
  
-==== Evaluation: Metal abundances in the interstellar gas ====+===== Evaluation: Metal abundances in the interstellar gas =====
  
 /* /*
Line 17: Line 17:
 */ */
  
-Search for a UV spectrum of Delta Orionis in the [[https://archive.stsci.edu/iue/search.php|IUE database]] (use a radius of a few arc second). By clicking on the ''dataID'', a preview will open, offering the possibility to download the spectrum as an ASCII file. The data needs to be converted to final spectra (flux over wavelength) with the script ''iue-makelambdascale.plot'' that can be found in ''~/scripts/d1/''. The header of the downloaded file needs to be commented out before it can be read by the script. Moreover, the corresponding file name needs to be stated in the script. The script can be run with+Search for a UV spectrum of Delta Orionis in the [[https://archive.stsci.edu/iue/search.php|IUE database]] (use a radius of a few arc second). By clicking on the ''dataID'', a preview will open, offering the possibility to download the spectrum as an ASCII file. The data needs to be converted to final spectra (flux over wavelength) with the script ''iue-makelambdascale.plot'' that can be found in ''~/scripts/d1/''. The header of the downloaded file needs to be commented out (with * in //WRplot//) before it can be read by the script. Moreover, the corresponding file name needs to be stated in the script. The script can be run with
   wrplot filename.plot   wrplot filename.plot
 or or
Line 23: Line 23:
 The resolution of the IUE spectrograph in the high dispersion mode is $R = \frac{\Delta \lambda}{\lambda} = 10000$. Identify the lines by of the line list (''lines.txt''), which also can be found in the scripts directory. Determine the line center of several lines and calculate the shifts with respect to values given in the line list. Determine the radial velocity of the absorbing cloud by means of the Doppler formula. Measure the equivalent width of the absorption lines of the following ions:  FeII, SiII, OI, AlI, SI, and NI. Create a curve of growth and determine the (logarithmic) column density for the elements listed before, i.e. log N(FeII), log N(SiII), etc. What is the Doppler parameter (b value) of the curve of growth?  The resolution of the IUE spectrograph in the high dispersion mode is $R = \frac{\Delta \lambda}{\lambda} = 10000$. Identify the lines by of the line list (''lines.txt''), which also can be found in the scripts directory. Determine the line center of several lines and calculate the shifts with respect to values given in the line list. Determine the radial velocity of the absorbing cloud by means of the Doppler formula. Measure the equivalent width of the absorption lines of the following ions:  FeII, SiII, OI, AlI, SI, and NI. Create a curve of growth and determine the (logarithmic) column density for the elements listed before, i.e. log N(FeII), log N(SiII), etc. What is the Doppler parameter (b value) of the curve of growth? 
  
-==== Evaluation ====+===== Evaluation =====
  
 Assume that the column density of neutral hydrogen in the cloud is log N(HI) = 19.92. Estimate the relative abundances of elements X in comparison to the sun, Assume that the column density of neutral hydrogen in the cloud is log N(HI) = 19.92. Estimate the relative abundances of elements X in comparison to the sun,
Line 33: Line 33:
 The evaluation shall be done using the ESO software package //Midas// which is installed at the [[en:praktikum:zugang |Laboratory course computer]] or can be [[en:software:howto_midas_install| installed]] at the own computer. The required data and scripts are being provided by the instructors.  The evaluation shall be done using the ESO software package //Midas// which is installed at the [[en:praktikum:zugang |Laboratory course computer]] or can be [[en:software:howto_midas_install| installed]] at the own computer. The required data and scripts are being provided by the instructors. 
  
-==== Protocol ====+===== Protocol =====
  
 First, describe the background of this experiment. Estimate the wavelength shifts, the resulting velocity including the error margins (non-linear error propagation!). Determine the b parameters of the curve of growths and the column densities of the different elements. Use the above formula to calculate the relative abundances in respect to solar values and their deviation from those values in percent. First, describe the background of this experiment. Estimate the wavelength shifts, the resulting velocity including the error margins (non-linear error propagation!). Determine the b parameters of the curve of growths and the column densities of the different elements. Use the above formula to calculate the relative abundances in respect to solar values and their deviation from those values in percent.
  
 [[en:praktikum:index|Overview: Laboratory Courses]] [[en:praktikum:index|Overview: Laboratory Courses]]
  • en/praktikum/ism.txt
  • Last modified: 2017/09/07 15:39
  • by rhainich