2.2. The Models
The constraints on the family of models presented here are such that
they are useful to explain emissions from compact H II regions, for
which both total luminosity and mass (gas+dust) are available from
observations. All models are constrained by a total mass,
MT, of 2.7 x 104
M and the
luminosity is constrained by the type of ZAMS
star embedded at the centre. The outer boundary condition is provided
by the ISRF taken from
Mathis et al., 1983.
Three types of ZAMS stars, viz., O4, O7 and B0.5,
with luminosity covering a range of two orders of magnitude,
are considered. The stellar type also determines the flux of
photons with
< 912 Å
and hence has a direct bearing on
the radio continuum calculations. In this study, stellar parameters
like luminosity, effective temperature and number of Lyman continuum
photons emitted per sec, have been taken from
Thompson (1984) and
the stellar luminosity for
< 912 Å has been obtained from
Panagia (1973). The stellar characteristics used here, are
presented in Table 1. For each stellar
type, both r0 and r-1 density distributions are
considered. Again, for each density distribution, a family of 12 models with
the total radial optical depth
(defined at the wavelength of 100 µm, hereafter
100)
ranging from 0.005
to 0.260 are considered. The r-2 density distribution has not
been considered here, since for the MT and range of
100
explored, the cloud sizes become too large and unphysical.
Spectral type | Luminosity | Teff | NLyc |
L![]() | K | sec-1 | |
O4 | 1.260 x 106 | 50000 | 5.811 x 1049 |
O7 | 1.000 x 105 | 38500 | 3.630 x 1048 |
B0.5 | 1.064 x 104 | 26200 | 1.318 x 1046 |
The geometrical details of the models are determined as follows:
Rmin
is determined by the sublimation temperature of dust and the stellar
luminosity, hence it remains the same for each stellar type;
Rmax for each model is determined from the total mass,
100,
and the radial density distribution;
the extent of the H II region (RHII) is determined by the embedded
stellar type and the radial density profiles of the interstellar material
of the cloud. All these parameters
are presented in Tables 2,
3 and 4 for embedded
stellar types O4, O7 and B0.5 respectively.
![]() | r0 | r-1 | ||||||
Rmin | Rmax | RHII | nd(Rmin) | Rmin | Rmax | RHII | nd(Rmin) | |
(10-4) | (pc) | (10-2 pc) | (10-7 cm-3) | (10-4) | (pc) | (10-2 pc) | (10-7 cm-3) | |
0.005 | 2.10 | 14.21 | 341 | 0.122 | 2.40 | 35.99 | 410 | 0.752 |
0.0075 | 2.10 | 11.60 | 209 | 0.224 | 2.40 | 29.05 | 108 | 1.153 |
0.010 | 2.20 | 10.05 | 148 | 0.345 | 2.40 | 24.96 | 48.1 | 1.563 |
0.015 | 2.20 | 8.20 | 89.6 | 0.635 | 2.40 | 20.14 | 19.0 | 2.399 |
0.020 | 2.20 | 7.10 | 62.7 | 0.977 | 2.40 | 17.29 | 11.4 | 3.254 |
0.040 | 2.30 | 5.02 | 26.3 | 2.765 | 2.20 | 12.04 | 4.71 | 7.328 |
0.060 | 2.30 | 4.10 | 15.7 | 5.080 | 2.10 | 9.73 | 3.42 | 11.74 |
0.080 | 2.30 | 3.55 | 10.9 | 7.822 | 2.00 | 8.38 | 2.85 | 16.64 |
0.100 | 2.30 | 3.18 | 8.22 | 10.93 | 1.80 | 7.49 | 2.38 | 23.13 |
0.150 | 2.30 | 2.59 | 4.92 | 20.09 | 1.70 | 6.06 | 2.02 | 37.43 |
0.200 | 2.40 | 2.25 | 3.44 | 30.94 | 1.50 | 5.24 | 1.70 | 56.69 |
0.260 | 2.40 | 1.97 | 2.49 | 45.87 | 1.30 | 4.60 | 1.43 | 84.91 |
![]() | r0 | r-1 | ||||||
Rmin | Rmax | RHII | nd(Rmin) | Rmin | Rmax | RHII | nd(Rmin) | |
(10-4) | (pc) | (10-2 pc) | (10-7 cm-3) | (10-4) | (pc) | (10-2 pc) | (10-7 cm-3) | |
0.005 | 5.00 | 14.21 | 165 | 0.122 | 6.20 | 38.56 | 654 | 0.268 |
0.0075 | 5.40 | 11.60 | 105 | 0.224 | 6.20 | 31.18 | 198 | 0.411 |
0.010 | 5.40 | 10.05 | 75.7 | 0.345 | 6.20 | 26.81 | 95.2 | 0.564 |
0.015 | 5.60 | 8.20 | 47.5 | 0.635 | 6.20 | 21.67 | 40.9 | 0.877 |
0.020 | 5.60 | 7.11 | 34.0 | 0.977 | 6.20 | 18.63 | 25.6 | 1.226 |
0.040 | 5.80 | 5.02 | 15.0 | 2.763 | 5.80 | 12.99 | 11.5 | 2.772 |
0.060 | 5.80 | 4.10 | 9.22 | 5.077 | 5.60 | 10.51 | 8.61 | 4.583 |
0.080 | 5.80 | 3.55 | 6.50 | 7.817 | 5.20 | 9.07 | 7.10 | 6.743 |
0.100 | 5.80 | 3.18 | 4.96 | 10.92 | 4.80 | 8.10 | 6.11 | 9.128 |
0.150 | 5.80 | 2.59 | 3.01 | 20.07 | 4.40 | 6.57 | 5.09 | 16.31 |
0.200 | 5.90 | 2.25 | 2.12 | 30.90 | 3.80 | 5.69 | 4.21 | 24.88 |
0.260 | 5.90 | 1.97 | 1.53 | 45.81 | 3.50 | 4.98 | 3.75 | 36.30 |
![]() | r0 | r-1 | ||||||
Rmin | Rmax | RHII | nd(Rmin) | Rmin | Rmax | RHII | nd(Rmin) | |
(10-4) | (pc) | (10-2 pc) | (10-7 cm-3) | (10-4) | (pc) | (10-2 pc) | (10-7 cm-3) | |
0.005 | 1.40 | 14.21 | 323 | 0.122 | 1.80 | 40.75 | 2320 | 0.781 |
0.0075 | 1.40 | 11.60 | 213 | 0.224 | 1.80 | 32.99 | 1070 | 1.192 |
0.010 | 1.40 | 10.05 | 158 | 0.345 | 1.80 | 28.39 | 675 | 1.609 |
0.015 | 1.40 | 8.20 | 104 | 0.635 | 1.80 | 22.97 | 405 | 2.457 |
0.020 | 1.50 | 7.11 | 76.7 | 0.977 | 1.80 | 19.77 | 305 | 3.319 |
0.040 | 1.50 | 5.02 | 36.8 | 2.763 | 1.70 | 13.79 | 132 | 7.217 |
0.060 | 1.50 | 4.10 | 23.9 | 5.076 | 1.60 | 11.19 | 57.0 | 11.66 |
0.080 | 1.50 | 3.55 | 17.5 | 7.815 | 1.50 | 9.65 | 31.6 | 16.70 |
0.100 | 1.50 | 3.18 | 13.8 | 10.92 | 1.50 | 8.59 | 19.8 | 21.10 |
0.150 | 1.60 | 2.59 | 8.85 | 20.07 | 1.30 | 6.99 | 8.69 | 36.73 |
0.200 | 1.60 | 2.25 | 6.45 | 30.89 | 1.20 | 6.04 | 4.83 | 53.38 |
0.260 | 1.60 | 1.97 | 4.82 | 45.79 | 1.10 | 5.28 | 2.83 | 76.03 |