Spectral energy distribution explained

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.

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

Further reading

• Book: Eberhard Haug. Werner Nakel. amp. The elementary process of Bremsstrahlung . 2004 . Scientific lecture notes in physics, vol. 73 . . River Edge NJ . 978-981-238-578-9 .
• Web site: Fitting the spectral energy distributions of galaxies. Jakob Walcher. Brent Groves. Tamás Budavári. Daniel Dale. dead. https://web.archive.org/web/20140814041031/http://www.sedfitting.org/SED08/Paper_vs1.0_online/walcher_ms.html. 2014-08-14.

External links

• The High Energy Astrophysics Science Archive Research Center (HEASARC) at NASA
• The Science of Spectroscopy

Notes and References

1. Web site: SED plots - CoolWiki. coolwiki.ipac.caltech.edu. en. 27 February 2018.
2. Dolan JF . The Direct Reduction of Astronomical X-Ray Spectra . Astrophys. Space Sci. . Aug 1972 . 17 . 2 . 472–81 . 10.1007/BF00642917 . 1972Ap&SS..17..472D . 123125127 .