Question ID = 0081
Question ID = 0081
Assigned Member (担当者)2007-11-12 M. KawaharadaName and Institute (質問者/機関)T. Lehto / University of Helsinki, FinlandQuestion (質問)We are doing arfs for the galaxy cluster A2104 and we are wondering what is the exact meaning of the parameter SOURCE_RATIO_REG? In this example (see figure) we used an 8 arcminutes circle as a source_image and two 2 arcminutes regions as regfile1 and regfile2. The only difference between those two arfs is the location of the 2 arcminutes region. However, SOURCE_RATIO_REGs are different. The region located lower left in the image gives SOURCE_RATIO_REG = 0.023 and the region located near the center of the image gives SOURCE_RATIO_REG = 0.041.In paper Y. Ishisaki et al. astro-ph/0610118 is written: "SOURCE_RATIO_REG holds the ratio of the source image inside the specified accumulation region for the ARF". So, shouldn't those two SOURCE_RATIO_REG values be the same? Answer from(回答の文責)Dr. IshisakiAnswer (答え)The definition of SOURCE_RATIO_REG isSOURCE_RATIO_REG = ∫ S(x,y) dx dy / ∫ S(x,y) dx dy, extract region all region of input image where S(x,y) is the source count at (x,y) position of the input image (please see the part below Table 4 in Sato et al. 2007, PASJ Vol.59, No.2, pp.299-317 ; astro-ph/0701328). Therefore, when you input a cluster image and extract two regions with the same area, SOURCE_RATIO_REG of the nearer region to the center becomes larger because S(x,y) in the central region is larger than the peripheral one. Status （詳細なステータス）2007-11-12 Accept2007-11-16 Reso 2007-11-16 Done 
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