The emergent continuum Spectral Energy Distribution (SED) from each model, as
resulting from the radiation transfer calculations through the
dust component have been translated into directly measurable
quantities keeping in mind the photometer ISOPHOT
(Lemke et al., 1996)
onboard the space mission, ISO.
This photometer covers wavebands between 2.5 and
240 µm, and hence is well suited to sample the entire infrared SED.
A set of ISOPHOT filters have been carefully selected
for this purpose, which represent the continuum SED
originating from the dust grains in
thermal equilibrium (e.g. avoiding filters specially planned
for features due to the non-equilibrium processes of Polycyclic
Aromatic Hydrocarbon (PAH) or Very Small Grains (VSG) etc;
Puget & Leger, 1989).
The predicted spectrum has been convolved with the ISOPHOT
filter responses (as a function of wavelength;
Klaas et al., 1994) to
calculate the expected signals.
A list of these filters and their respective specifications
are presented in Table 5. In all, five PHT-P
filters and three PHT-C filters have been chosen to cover
the entire mid to far infrared region. The predicted colours
between the selected PHT-P and PHT-C bands,
are presented as a function of
100,
in Figures 2-4 for the
families of models explored here.
Throughout the present paper, by ``colour'',
we refer to the logarithm (to the base of 10) of the ratio of
flux densities. The colours have been selected such that (i) both the
filters defining a particular colour correspond to the
same sub-instrument (e.g. either PHT-P or PHT-C); and
(ii) the colours represent local slopes of the SEDs (i.e. using filters
neighbouring in effective wavelength).
Figures 2, 3 and
4 represent
the variation of colours as a function of
100
corresponding to a central star of type, O4, O7 and B0.5 respectively.
Only those colours which are sensitive to
100, and hence have
important diagnostic value, have been presented here.
In each figure, two sets of model predictions are presented corresponding to
the dust density distribution laws proportional to
r0 and r-1 (with all other constraints being identical).
Instrument | Filter # | ![]() | ![]() ![]() |
µm | µm | ||
PHT-P | 3 | 4.86 | 1.55 |
9 | 12.83 | 2.33 | |
12 | 23.81 | 9.18 | |
13 | 60.06 | 25.48 | |
14 | 101.63 | 40.15 | |
PHT-C | 4 | 95.1 | 51.4 |
8 | 161.0 | 82.5 | |
11 | 204.6 | 67.3 | |
CAM-SW | 3 | 4.50 | 1.00 |
4 | 2.77 | 0.55 | |
9 | 3.88 | 0.24 | |
CAM-LW | 5 | 6.75 | 0.50 |
5 | 6.75 | 0.50 | |
8 | 11.4 | 1.30 | |
9 | 15.0 | 2.00 | |
The results of the radiative transfer of Lyman continuum photons
through the gas (pure hydrogen) and the dust where it co-exists,
as described in Appendix-A, are presented in terms of
ratio of radio to far-IR emission.
In Figure 5 the ratio of the predicted flux
densities at 5 GHz and
60 µm are displayed as a function of
100. Once again different
curves correspond to different density distribution laws as
explained in their captions.