next previous
Up: Studies of dense

3. Results

 

3.1. Observational data

Most of the detected sources were mapped in the ammonia lines. In Fig. 1 (click here) we present the grey-scale maps of the tex2html_wrap_inline1913 (1, 1) emission. The positions of the tex2html_wrap_inline1915 masers (taken mainly from Palagi et al. 1993), IRAS point sources as well as near-IR sources from the CIO catalogue (Gezari et al. 1993) are indicated. We plot the following maps for most detected sources: maps of tex2html_wrap_inline1917 (1, 1) line intensity integrated over the main group of the hfs components and (1, 1) maps for the blue- and red-side velocity intervals which represent 1/3 of the total velocity range each. Thus, these maps give an impression of the source kinematics. To determine the total velocity range a composite spectrum was constructed for each source by overlaying all the measured (1, 1) spectra in one plot. Then, by visual inspection of this composite spectrum the velocity range was determined as the interval where a noticeable emission in the main group was present above the tex2html_wrap_inline1919 level (corresponding to tex2html_wrap_inline1921). For several sources CS J=2-1 maps from Paper II are overlayed on the ammonia maps. In Table 2 (click here) we present peak values of the tex2html_wrap_inline1925 (1, 1) integrated line intensites and locations of the peaks as given by the GAG routines. In Cols. (5) and (6) of Table 2 (click here) the lower and upper boundaries of the velocity ranges used for integrating the line intensities (tex2html_wrap_inline1927 and tex2html_wrap_inline1929) are indicated.

The tex2html_wrap_inline1931 (1, 1) and (2, 2) line parameters at the grid positions closest to the peaks of the ammonia emission are presented in Table 3 (click here). The typical rms noise was tex2html_wrap_inline1933 on the tex2html_wrap_inline1935 scale.

The non-detected sources are listed in Table 4 (click here).

In addition, in Tables 5-14 we give some results describing the structure of the sources: velocities and line widths for the (1, 1) lines at the observed positions (obtained from the fitting procedure) as well as estimates of the tex2html_wrap_inline1937 column densities and kinetic temperatures. The latter are presented only for those positions where reliable estimates of the optical depth in the (1, 1) line could be obtained.

3.2. Comments on individual objects

 

3.2.1. S 76 E

This source shows a very unusual HCN emission spectrum in which the main component (F=2-1) is practically absent (Zinchenko et al. 1993). Zinchenko et al. suggested that this effect can be caused by a foreground absorbing cloud with a velocity blue-shifted by tex2html_wrap_inline1943 relative to the HCN emitting core. In our tex2html_wrap_inline1945 (1, 1) spectra (Fig. 2 (click here)) a weak additional component can be seen.

 

Source

tex2html_wrap_inline1947 tex2html_wrap_inline1949 tex2html_wrap_inline1951 tex2html_wrap_inline1953 tex2html_wrap_inline1955
(tex2html_wrap2261) (tex2html_wrap2263) (Kkmstex2html_wrap_inline1961) (kmstex2html_wrap_inline1963) (kmstex2html_wrap_inline1965)

S 76 E

0 0 12.9 29.4 35.1
S 86 0 -40 5.3 26.0 30.0
S 87 10 40 7.6 20.0 27.0
S 88 B 50 40 1.2 20.0 24.0
S 145 0 0 1.6 -11.3 -7.5
S 199 10 10 2.2 -39.5 -36.5
S 231 10 30 7.0 -19.5 -13.5
S 255 0 80 4.7 4.8 10.8
RNO 1B 0 0 9.6 -19.6 -15.1
BFS 48 0 0 5.9 -11.5 -7.0

Table 2: Peak values of (1, 1) integrated line intensities, locations of the peaks and boundaries of the velocity ranges used for integrating the line intensities
 

In Fig. 3 (click here) we plot the average tex2html_wrap_inline1967 (1, 1) spectrum in this source and the residual tex2html_wrap_inline1969 (1, 1) spectrum obtained by subtracting the single gaussian tex2html_wrap_inline1971 pattern fit from the average spectrum. It clearly shows a weak tex2html_wrap_inline1973 line with a central velocity of tex2html_wrap_inline1975 and a width of tex2html_wrap_inline1977. This detection strongly supports the hypothesis of the foreground cloud mentioned above. There is no sign of this feature in the tex2html_wrap_inline1979 (2, 2) spectra, which implies an upper limit on the kinetic temperature of tex2html_wrap_inline1981. The inspection of our data shows that the intensity of this component grows from our central position towards the south-west. However, the fact that this component is especially pronounced in the average spectrum indicates that its spatial extension is not much less than the size of the mapped region.

  figure391
Figure 2: The tex2html_wrap_inline1983 (1, 1) and (2, 2) lines measured at the central position in S 76 E

  figure396
Figure 3: The average tex2html_wrap_inline1985 (1, 1) spectrum in S 76 E and the residual spectrum obtained by subtraction of the single tex2html_wrap_inline1987 gaussian pattern from the average spectrum

 

(1, 1)(2, 2)

Source

tex2html_wrap_inline1991 tex2html_wrap_inline1993 tex2html_wrap_inline1995 tex2html_wrap_inline1997tex2html_wrap_inline1999 tex2html_wrap_inline2001 tex2html_wrap_inline2003 tex2html_wrap_inline2005tex2html_wrap_inline2007 tex2html_wrap_inline2009
(tex2html_wrap_inline2011) (tex2html_wrap_inline2013) (K) (kmstex2html_wrap_inline2015)(kmstex2html_wrap_inline2017) (K) (kmstex2html_wrap_inline2019)(kmstex2html_wrap_inline2021) (K)

S 76 E

0 0 3.96(07) 32.04(01) 2.70(0.03) 0.83(0.05) 2.63(22) 32.09(02) 2.91(0.09) 27.2(1.3)
S 86 0 -40 2.65(21) 28.01(02) 1.48(0.07) 1.46(0.27) 1.87(44) 28.06(05) 1.62(0.17) 26.0(3.5)
S 87 0 40 2.93(16) 23.65(02) 1.48(0.05) 1.45(0.19) 1.96(07) 23.65(30) 1.61(1.03) 25.0(3.0)
0 40 1.31(16) 21.14(02) 0.81(0.11) 2.15(0.73) 0.72(07) 21.25(30) 0.89(1.03) 18.8(3.5)
S 88 B 40 40 0.45(14) 21.58(16) 2.50(0.39) 0.38(06) 21.43(21) 2.28(0.45) 38(10)
S 145 0 0 1.08(09) -9.77(04) 1.22(0.13) 0.45(08) -9.96(13) 1.71(0.39) 22(04)
S 199 0 0 1.23(12) -38.17(03) 1.48(0.09) 0.66(0.28) 0.81(07) -38.19(05) 1.55(0.15) 27.9(2.1)
S 201 40 0 0.76(13) -37.74(09) 1.16(0.23) 0.41(11) -37.91(25) 2.32(0.73) 54(27)
S 231 30 35 2.43(10) -16.37(02) 2.16(0.06) 0.97(0.13) 1.61(22) -16.24(03) 1.90(0.11) 26.5(2.1)
S 255 0 80 1.64(11) 8.65(03) 2.41(0.09) 0.85(0.19) 0.90(04) 8.69(05) 2.61(0.15) 23.0(1.0)
40 -40 1.34(14) 6.55(04) 1.83(0.11) 0.54(0.28) 0.75(06) 6.60(08) 1.91(0.21) 24.7(2.5)
RNO 1 B 0 0 3.85(16) -17.65(02) 2.09(0.05) 0.98(0.13) 1.93(46) -17.74(04) 2.21(0.18) 21.1(2.3)
BFS 48 0 0 2.53(17) -9.36(03) 1.85(0.07) 1.35(0.23) 1.16(32) -9.36(08) 1.99(0.21) 18.7(2.2)

Table 3: tex2html_wrap_inline1989 (1, 1) and (2, 2) line parameters at the grid positions closest to the emission peaks. The numbers in the brackets are the statistical uncertainties in the last digits (standard deviations). In the last column kinetic temperatures derived from these data are indicated

 

 

Source

tex2html_wrap_inline2257
(K)

S 74

0.16
S 90 0.16
S 93 0.17
S 100 0.23
S 146 0.20
S 161 B 0.20

Table 4: List of non-detected sources. Rms noise per channel is indicated

 

It is worth noting that S 76 E is the strongest source of ammonia emission in our sample. The maps in different velocity intervals reveal a slight velocity gradient approximately in the north-south direction.

3.2.2. S 87

Our data clearly show the presence of two kinematically distinct components which overlap partly spatially (Figs. 1 (click here), 4 (click here)). Similar structure has been seen in some other lines (e.g. Barsony 1989) including tex2html_wrap_inline2269 (Stutzki et al. 1984). However, to our knowledge the source has not been mapped in the ammonia lines yet. A submillimeter continuum map at tex2html_wrap_inline2271 (Jenness et al. 1995) shows a morphology which is very similar to our ammonia map.

  figure461
Figure 4: The tex2html_wrap_inline2273 (1, 1) and (2, 2) lines measured at the position (0,40tex2html_wrap2279) in S 87

3.2.3. RNO 1 B

This cloud was subject to detailed investigations in various molecular lines including the ammonia lines by Estalella et al. (1993) and Yang et al. (1991, 1995). Our ammonia data are very similar to the results obtained by Estalella et al. and we present them here just for the sake of the homogeneity for statistical analysis.

3.3. Physical properties of the sources

 

In Table 3 (click here) we present the values of the kinetic temperatures at the grid positions closest to the peaks of the ammonia emission. We estimate the uncertainties of these values in tex2html_wrap_inline2281 in most cases. The exceptions are S 88 B, S 145 and S 201 where the lines are too weak. For them we give kinetic temperatures derived in the optically thin approximation from the ratio of the (2, 2) and (1, 1) line areas (Harju et al. 1993).

The sizes, masses, mean densities, average line widths and virial masses determined in the way described in Sect. 2.3 (click here) are presented in Table 15 (click here).

 

Source

L tex2html_wrap_inline2285 M tex2html_wrap_inline2289 tex2html_wrap_inline2291
(pc) (cmtex2html_wrap_inline2293) (tex2html_wrap_inline2295) (kmstex2html_wrap_inline2297) (tex2html_wrap_inline2299)

S 76E

0.91 4.26 700 2.63 660
S 86 0.64 4.12 180 1.52 160
S 87 0.94 4.08 530 3.30 1080
S 88 B 1.10 3.02 74 2.42 680
S 145 0.40 3.63 14 1.22 62
S 199 1.28 3.31 230 1.36 250
S 231 1.24 3.84 690 1.96 500
S 255 1.43 3.60 600 3.00 1350
RNO1B 0.48 4.42 150 1.65 140
BFS 48 0.75 4.10 270 1.85 270

Table 15: Sizes, masses, mean densities, average line widths and virial masses of the clouds

 

The comparison with the CS J=2-1 results from Paper II for S 76 E, S 199 and S 255 shows that the ammonia lines are tex2html_wrap_inline2303 narrower than the CS lines. The source sizes are tex2html_wrap_inline2305 times smaller in ammonia. The core masses are correspondingly smaller. But the mean densities are similar. This is similar to the results of such comparison for other clouds in Paper II.


next previous
Up: Studies of dense

Copyright by the European Southern Observatory (ESO)
web@ed-phys.fr