## 5. Discussion## 5.1. Comparison of various bandsWe calculated the ratio between the dust mass and the mass of the
gas in the Kh 15 core (see Sects. 4.2 and 4.3) and obtained
1:50 and
1:120 using the 15 K and the 17 K
dust temperatures, respectively. Derivation of the mass of the gas
using Several papers investigated the relationship between the FIR
intensities, the column density of CO isotopic lines and the visual
extinction (see e.g. Laureijs et al. 1989, 1991, 1995). The ratio of
the 100 To probe a larger area around Kh 15, we have constructed a scatter
plot of the 100 We have also investigated these correlations using our DSS star
counts (See Sect. 3.1.2). Comparing the COBE calibrated HIRES
100 (see also Fig. 8). The correlation coefficient is 0.72. The
value of the slope is in a good agreement with the values found by
Laureijs et al. (1995) towards the L134 cloud complex (2.1, 2.9 and
3.7 for LDN 183, LDN 134 and
LDN 169, respectively; see their Table 2). The two distinct
values of the slopes (5.1 and
2.5 from Wolf-diagrams and DSS star
counts, respectively) are not in contradiction if we note that they
probe regions of different densities and probably different dust
compositions. In the outer regions of Kh 15 the 60
Assuming that integrated intensities of CO isotopic lines are
proportional to or
, we have derived regression
parameters from least-squares fits, presented in Fig. 9 and
Table 6. To compare the Nagoya
## 5.2. Stability of Kh 15:The dynamical state of the Kh 15 core was investigated following
Liljeström (1991). If the gas motions in the The analysis can be repeated following Spitzer (1978, Eq. [11-24]), taking into account the external pressure as well. In this case we assumed spherical symmetry, uniform external pressure and no magnetic field or rotation. We defined a "dynamical" temperature of the core as the Doppler temperature corresponding to the line width of the emission at the peak intensity (see e.g. Nozawa et al. 1991, Eq. [10]): , where is the mean molecular mass, is the full linewidth at half-maximum and is the Boltzmann constant. This yielded . The external pressure and its maximum value have been estimated in the same manner as described by Nozawa et al. (1991, Sect. 4.2, Eq. [10-13]). We derived and for Kh 15. We conclude that the cloud is in stable equilibrium, since and . ## 5.3. Connection of Kh 15 to its neighbourhoodWe have shown in Sect. 4.1, that Kh 15 and the NW-part of GIRL126+10 are at similar distances ( and respectively) within the uncertainities and taking into account the 25 pc size of the loop. These distance of the loop is in an excellent agreement with the distance of LDN 1333. Additional pointed
We conclude from the collected multiwavelength data that Kh 15 is
part of the loop structure seen at l=126 ## 5.4. The wall of the Local Bubble?Table 4 shows the presence of a nearby extinction layer (at pc) appearing in most of the subfields of the Schmidt-plate. Sfeir et al. (1999) estimated the distance to the wall of the Local Bubble (LB) based on measurements of the equivalent widths of the NaI D line doublet, and distances measured by Hipparcos. They have found that the wall of the LB is located at 130 pc at this galactic longitude, at . This is in agreement with our estimation, thus we may consider this layer as the wall of the LB. © European Southern Observatory (ESO) 2000 Online publication: December 11, 2000 |