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Spectral energy distribution

Summary

A spectral energy distribution (SED) is a plot of energy versus frequency or wavelength of light (not to be confused with a 'spectrum' of flux density vs frequency or wavelength).[1] It is used in many branches of astronomy to characterize astronomical sources. For example, in radio astronomy they are used to show the emission from synchrotron radiation, free-free emission and other emission mechanisms. In infrared astronomy, SEDs can be used to classify young stellar objects.

The SED of M51 (upper right) obtained by combining data at many different wavelengths, e.g. UV, visible, and infrared (left)

Detector for spectral energy distribution edit

The count rates observed from a given astronomical radiation source have no simple relationship to the flux from that source, such as might be incident at the top of the Earth's atmosphere.[2] This lack of a simple relationship is due in no small part to the complex properties of radiation detectors.[2]

These detector properties can be divided into

  • those that merely attenuate the beam, including
    1. residual atmosphere between source and detector,
    2. absorption in the detector window when present,
    3. quantum efficiency of the detecting medium,[2]
  • those that redistribute the beam in detected energy, such as
    1. fluorescent photon escape phenomena,
    2. inherent energy resolution of the detector.[2]

See also edit

References edit

  1. ^ "SED plots - CoolWiki". coolwiki.ipac.caltech.edu. Retrieved 27 February 2018.
  2. ^ a b c d Dolan JF (Aug 1972). "The Direct Reduction of Astronomical X-Ray Spectra". Astrophys. Space Sci. 17 (2): 472–81. Bibcode:1972Ap&SS..17..472D. doi:10.1007/BF00642917. S2CID 123125127.

Further reading edit

  • Eberhard Haug & Werner Nakel (2004). The elementary process of Bremsstrahlung. River Edge NJ: World Scientific. p. Scientific lecture notes in physics, vol. 73. ISBN 978-981-238-578-9.
  • Jakob Walcher; Brent Groves; Tamás Budavári; Daniel Dale. "Fitting the spectral energy distributions of galaxies". Archived from the original on 2014-08-14.

External links edit

  • The High Energy Astrophysics Science Archive Research Center (HEASARC) at NASA
  • The Science of Spectroscopy Archived 2019-03-23 at the Wayback Machine