Spectral energy distribution

For other uses, see Sed (disambiguation).

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

A spectral energy distribution (SED) is a plot of energy versus frequency or wavelength of electromagnetic or mechanical radiation, most commonly 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.

Detector for spectral energy distribution

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

• Astronomical radio source
• Astronomical X-ray sources
• Background radiation
• Bremsstrahlung
• Cosmic microwave background spectral distortions
• Cyclotron radiation
• Electromagnetic radiation
• Synchrotron radiation
• Wavelength dispersive X-ray spectroscopy

References

1. "SED plots - CoolWiki". coolwiki.ipac.caltech.edu. Retrieved 27 February 2018.
2. 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

• 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

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