S-ARC FJS

Fernando J. Selman

Staff Astronomer

European Southern Observatory


Duties

  • Instrument Scientist for OMEGACAM at VST.
  • Instrument Scientist for VIMOS at UT3@VLT.
  • Prior Instrument Scientist for HAWK-I at UT4@VLT.
  • Scientific Interests

    Technological Interests

    • Wide Field Photometry.

      The photometry with wide-field cameras suffer the particularly troublesome problem of light concentration: the effective illumination on the focal plane is not uniform and tends to be concentrated toward the center. This gives the mistaken impression that the relative sensitivity near the center of the field is larger than it really is. Because the problem affects both flat-field and science frames we do not notice it unless we do aperture photometry of the same stars across the field. I have developed a method to determine the correction as a function of position which allow me to correct to better than 1%. These results are presented with some detail in a paper at the 2004 SPIE meeting in Glasgow.
    • Visualization of scientific data.
    • When the amount of data to be analyzed is large it becomes imperative to have powerful means of visualization. I am developing tools based on VTK, and written in C++, Tcl, and Python to visualize the large amounts of data that come out of WFI. You can see an example in the previous section. Here I present a slightly more elaborated one in which I super-impose on the data the evolutionary track of a 12Msun star. The color of the tube represents the luminosity class: I, red; III, yellow; and V, blue; the width of the track represents the speed at which the star is traveling in the stereogram, as it evolves. I have painted the star of different colors according to their V magnitude so that they can retain this information when seen from another perspective.

    • Statistical techniques.
    • It is not enough to visualize the data, but we must be able to extract the information in an optimal way. I have developed a Bayesian technique that allow us to go from classical UBV photometry to masses, ages, and extinctions. This technique is presented in Paper III.


    Last updated 2008-May-15
    fselman@eso.org