Документ взят из кэша поисковой машины. Адрес
оригинального документа
: http://www.stsci.edu/stsci/meetings/irw/proceedings/fusipeccif.dir/section3_3.html
Дата изменения: Sat Apr 16 01:43:09 1994 Дата индексирования: Sun Dec 23 20:42:45 2007 Кодировка: Поисковые слова: aircraft |
From the data taken during Cycle 1, surface brightness profiles have been obtained for 13 globular clusters in M31 (Fusi Pecci et al. 1993), leading also to the detection of a central cusp in a candidate post-core-collapse cluster (Bendinelli et al. 1993). Detailed tests and simulations have been carried out to verify the reliability of the quoted results obtained by applying various deconvolution methods to the observed data.
To further explore the influence on the various procedures of any variation in the size of the adopted PSF compared to the data matrix and in the adopted background, we have carried out here a new set of simulations based on the following assumptions:
As shown in Figs. 3 and 4, the following results have been obtained:
In Fig. 4d we show the profiles of Fig. 4a differentially with respect to the results of the R-L over 512512. The models indicate that the use of smaller data matrices produces a shift in the overall brightness profile, which is found also when this test is performed on real data (e.g., the cluster Bo373 = G305).
In summary, it is evident that much care must be taken in order to ensure that all the necessary information is amply contained in the frames to be analyzed. The combination of an overestimated background (such as our ``local'' sky) coupled with an insufficiently extended PSF may lead to large discrepancies in the derived profiles, which could be partially reduced by the the use of the RMG deconvolution method, as all the profiles are implicitly extrapolated outside the actual matrix size, albeit with a Gaussian falloff.