View source for Spectral energy distribution

{{Other uses|Sed (disambiguation)}}
{{More citations needed|date=December 2009}}

[[File:Example data processed by theSkyNet POGS distributed computing project.png|thumb|right|358x358px|The SED of [[Whirlpool Galaxy|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 light (not to be confused with a 'spectrum' of [[flux]] density vs frequency or wavelength).<ref>{{cite web|title=SED plots - CoolWiki|url=http://coolwiki.ipac.caltech.edu/index.php/SED_plots|website=coolwiki.ipac.caltech.edu|language=en|accessdate=27 February 2018}}</ref>  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 object]]s.

==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]].<ref name=Dolan>{{ cite journal |author=Dolan JF |title=The Direct Reduction of Astronomical X-Ray Spectra |journal= Astrophys. Space Sci. |date=Aug 1972 |volume=17 |issue=2 |pages=472–81 |doi=10.1007/BF00642917 |bibcode=1972Ap&SS..17..472D |s2cid=123125127 }}</ref> This lack of a simple relationship is due in no small part to the complex properties of radiation detectors.<ref name=Dolan/>

These detector properties can be divided into
*those that merely attenuate the beam, including
*#residual atmosphere between source and detector,
*#absorption in the detector window when present,
*#quantum efficiency of the detecting medium,<ref name=Dolan/>
*those that redistribute the beam in detected energy, such as
*#fluorescent photon escape phenomena,
*#inherent energy resolution of the detector.<ref name=Dolan/>

==See also==
{{div col|colwidth=25em}}
* [[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]]
{{Div col end}}

==References==
{{Reflist}}

==Further reading==
*{{ cite book |author=Eberhard Haug|author2=Werner Nakel|name-list-style=amp|title=The elementary process of Bremsstrahlung |date= 2004 |page =Scientific lecture notes in physics, vol. 73 |publisher=[[World Scientific]] |location=River Edge NJ |isbn=978-981-238-578-9 |url=https://books.google.com/books?id=v4FMtIwTri8C&q=bremsstrahlung+haug }}
*{{cite web|title=Fitting the spectral energy distributions of galaxies|url=http://www.sedfitting.org/SED08/Paper_vs1.0_online/walcher_ms.html|author=Jakob Walcher|author2=Brent Groves|author3=Tamás Budavári|author4=Daniel Dale|url-status=dead|archiveurl=https://web.archive.org/web/20140814041031/http://www.sedfitting.org/SED08/Paper_vs1.0_online/walcher_ms.html|archivedate=2014-08-14}}

==External links==
*[https://web.archive.org/web/20031108030727/http://heasarc.nasa.gov/ The High Energy Astrophysics Science Archive Research Center (HEASARC) at NASA]
*[http://www.scienceofspectroscopy.info The Science of Spectroscopy] {{Webarchive|url=https://web.archive.org/web/20190323134512/http://www.scienceofspectroscopy.info/ |date=2019-03-23 }}

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[[Category:Applied and interdisciplinary physics]]
[[Category:Observational astronomy]]
[[Category:Optical phenomena]]
[[Category:Radiation]]
[[Category:Scattering]]
[[Category:Spectroscopy]]


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