|
Документ взят из кэша поисковой машины. Адрес
оригинального документа
: http://www.stsci.edu/stsci/meetings/irw/proceedings/moj.dir/section3_4.html
Дата изменения: Sat Apr 16 03:45:04 1994 Дата индексирования: Sun Dec 23 18:50:21 2007 Кодировка: Поисковые слова: п п п п п п п п п п п п п п п п п п п |
Fig. 6 gives three sets of the azimuthally averaged profiles and the encircled
energy plots. These are shown for (1) the PSFs (Image, Library, and Tiny TIM)
for the image R136 F555W, and (2) the vicinity of the restored PSF star,
centering on the PSF star with a radius 2 5, for the image R136 F555W,
and (3) the PSF star area in the restored image of R136 F547W.
The FWHM of the PSFs generated from different methods are all nearly the same
(0 1). The radius of the first ring of the Image PSF is very close to that
in the Tiny TIM model (
0
6) and smaller than the radius measured
for the Library PSF (
0
75). The second ring can clearly be seen in
the Tiny TIM PSF but not in the others because of the noise and background (see
Fig. 6, top left panel).
On the basis of the effective resolution and enhancement in dynamic range, the empirical PSF extracted from the data frame gives the best result. The peak value of the brightest star in the image restored using a PSF extracted from the same image is about four times higher than that obtained using the Library or Tiny TIM PSFs.
More residual PSF structures appear in the image restored using the Library and Tiny TIM PSFs. Bright stars sometimes split into a bright core with several faint neighbors. This may lead to the generation of a number of erroneous detections of faint stars in the restored images.
The encircled energy plot and the profile of the jet of M87 are illustrated in Fig. 7. The left panel shows the encircled energy plots in the vicinity of the galaxy nucleus in the restored images, and the profiles of the jet in the restorations are given in the right frame. The solid line in Fig. 7 shows the Library PSF for PC6, F547M, centered on pixel (337,328), and the dashed line shows the Tiny TIM PSF. The differences between the two encircled energy curves are minor. The structure of the faint jet is consistent in both M87 restorations.
There are several rings surrounding the nucleus of the galaxy in each restored image of M87. This is almost certainly an artifact of the mismatch between the true PSF and the models used, since the structure of the unrestored image is clearly dominated by the familiar features of the PSF (Fig. 8).
