3.2. Spatial / Structural Information
Next, the diagnostic power of spatial / structural
information has been assessed quantitatively.
The structural information of the gas+dust cloud
models considered here consist of spatial
variation of intensity across the source at different
wavelengths. Since all models are spherically symmetric,
the structural information is basically one dimensional.
In order to concisely present these information, the
half width at half maximum (HWHM) as a function of wavelength,
has been considered to be the primary parameter.
The imaging instrument onboard ISO, the ISOCAM, is well
suited for studying structural details in the wavelength
range 2.5 to 18 µm. This instrument images regions
of ~ 3' x 3' with an angular resolution of
~ 6" in various filters (CAM-SW covers 2.5 to 5.5 µm ;
CAM-LW covers 4 to 18 µm ;
Cesarsky et al., 1996).
Three bands each of CAM-SW as well as CAM-LW have been selected
(see Table 5) for predicting
HWHM sizes at their corresponding central wavelengths.
In order to get an insight into these size information,
as well as for ease of comprehension, the HWHM size dependence on
wavelength has been fitted by a power law of the form
1/2
(
) = b x
a. The
best fit values of `a' and `b' are listed in
Table 6
for a few selected models. One typical example for each stellar type for
uniform density case are also shown in Figure 6.
The usefulness of the values of `a' & `b' are discussed
in section 4.2.
| Spectral type | r0 | r-1 | ||
 100 = 0.040
| 100 = 0.26
| 100 = 0.040
| 100 = 0.26
| |
| O4 | a = 0.54 b = 15.96 | a = 0.24 b = 16.02 | a = 0.12 b = 15.86 | a = 0.42 b = 15.48 |
| O7 | a = 0.69 b=15.28 | a = 0.38 b=15.45 | a = 0.14 b=15.28 | a = 0.41 b=14.93 |
| B0.5 | a = 0.99 b=14.28 | a = 0.53 b=14.82 | a = 0.16 b=14.76 | a = 0.38 b=14.45 |
|
Figure 6. Plots of logarithms of half sizes
(shown as points), as a function of
log |