查看“Ew(Hα) of one star forming galaxy”的源代码

* Equivalent Width : EW(Hα)
Recall EW(Hα) measures the relative strength of Hα to the continuum under the line 
It therefore acts like a long baseline color index UV(Hα)<--> λ6550 A 

Although it cannot be converted to a current SFR, it has another important use : 
It measures the ratio of the current SFR (from Hα) to the integrated past SF (from the continuum) 
Using synthesis models, this relation can be quantified, to give : 
EW(Hα)--> (current SFR) / (mean past SFR)   ; written SFR/<SFR> or "b" 
http://www.astro.virginia.edu/class/whittle/astr553/Topic11/Lecture_11.html

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