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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Luminosity function (astronomy) ： ウィキペディア英語版 Luminosity function (astronomy) In astronomy, the luminosity function gives the number of stars or galaxies per luminosity interval. Luminosity functions are used to study the properties of large groups or classes of objects, such as the stars in clusters or the galaxies in the Local Group. Note that the term "function" is slightly misleading, and the luminosity function might better be described as a luminosity ''distribution''. Given a luminosity as input, the luminosity function essentially returns the abundance of objects with that luminosity (specifically, number density per luminosity interval). ==Schechter luminosity function== The Schechter luminosity function provides a parametric description of the space density of galaxies as a function of their luminosity. The form of the function is :$n(x)\; \backslash \; \backslash mathrmx\; =\; \backslash phi^$ * x^\alpha \mathrm^ \mathrmx, where $x\; =\; L/L^$ *, and $L^$ * is a characteristic galaxy luminosity where the power-law form of the function cuts off. The parameter $\backslash ,\backslash !\backslash phi^$ * has units of number density and provides the normalization. The galaxy luminosity function may have different parameters for different populations and environments; it is not a universal function. One measurement from field galaxies is $\backslash alpha=-1.25,\backslash \; \backslash phi^$ * = 1.2 \times 10^ h^3 \mathrm^.〔 〕 It is often more convenient to rewrite the Schechter function in terms of magnitudes, rather than luminosities. In this case, the Schechter function becomes: :$n(M)\; \backslash \; \backslash mathrmM\; =\; 0.4\; \backslash \; \backslash ln\; 10\; \backslash \; \backslash phi^$ * (10^ )^ \exp (-10^ ) \ \mathrmM . Note that because the magnitude system is logarithmic, the power law has logarithmic slope $\backslash alpha\; +\; 1$. This is why a Schechter function with $\backslash alpha\; =\; -1$ is said to be flat. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Luminosity function (astronomy)」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.