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Astron. Astrophys. 349, L53-L56 (1999)

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3. Results

The CS maps and the C18O map are shown in Fig. 1. The CS core is 0.03 pc wide and extents over 0.15 pc. Three dense condensations are found in the CS (2[FORMULA]1) and (3[FORMULA]2) maps, labelled CS-A, CS-B, and CS-C. CS-C coincides with the maximum C18O intensity, whereas CS-A and CS-B are not that apparent in the C18O map. Parameters for the three CS lines observed towards the center positions of these dense condensations and the corresponding C18O (1[FORMULA]0) transition are listed in Table 1 ; the CS spectra of the centre positions are displayed in Fig. 2. The CS (5[FORMULA]4) transition is significantly detected only towards CS-C; towards CS-A and CS-B there is evidence for these lines however with less than the 3 [FORMULA] significance level.

[FIGURE] Fig. 1. Total integrated line intensities of the CS (2[FORMULA]1) (top left), (3[FORMULA]2) (top right), and (5[FORMULA]4) transitions (bottom left) and the C18O (1[FORMULA]0) transition. Beamsizes are indicated in the lower left corner, observed CS positions are marked in the (5[FORMULA]4) map. Contours are every 0.25 K km s-1 starting at 0.25 K km s-1 for the CS (2[FORMULA]1) and (3[FORMULA]2) and the C18O (1[FORMULA]0) maps, 0.6 K km s-1 starting at 0.6 K km s-1 for the CS (5[FORMULA]) map.

[FIGURE] Fig. 2. CS (J=2[FORMULA]1), (3[FORMULA]2), and (5[FORMULA]4) spectra towards the centre positions of CS-A, CS-B, and CS-C. Positions are offsets in arcsec relative to [FORMULA]). For displaying purpose the (2[FORMULA]1) spectra have been shifted in the temperature scale by 6 K and the (3[FORMULA]2) spectra by 3 K.


Table 1. CS and C18O line parameters for the centre positions of the three dense condensations.
Parameters are derived from a gaussian fit to the data, those for the lower CS transitions of CS-C adopt 2 components. Units for [FORMULA] are (K) and for [FORMULA] and [FORMULA] are ( km s-1). The CS (5[FORMULA]4) transition is detected only towards CS-C with more than 3 [FORMULA], there is however indication for this line towards CS-A and CS-B on a lower significance level, the values derived from a formal gaussian fit towards these two positions are therefore listed in square brackets.

Table 2 summarizes the physical parameters of the three condensations. The full widths at half maximum of the three condensations derived from the CS spectra are 5600 AU, 6100 AU, and 4500 AU for CS-A, CS-B, and CS-C, resp. The masses, estimated from the C18O (1[FORMULA]0) transition adopting an excitation temperature of [FORMULA] K and a C18O abundance of N(C18O)/N([FORMULA], are between 0.06 [FORMULA] and 0.12 [FORMULA] for the three condensations. Their virial masses are about 0.2 [FORMULA]; given the uncertainties in deriving these quantities it is not unreasonable to assume that they are really gravitationally bound. The H2 volume densities of about 105 cm-3 are derived by adopting the extent of the clumps to be the same in all three dimensions. These densities are of the same order as the critical density for the CS (3[FORMULA]2) transition.


Table 2. Physical parameters for the three condensations.
Adopted distance 150 pc.

The spectra towards CS-A and CS-B are well described by single gaussian lines. The spectra towards CS-C are clearly double-peaked in the CS (2[FORMULA]1) and (3[FORMULA]2) lines with the red shifted peak less intense than the blue shifted peak and only single peaked in the CS (5[FORMULA]4) line. Double-peaked (3[FORMULA]2) and (2[FORMULA]1) lines are only detected towards the immediate surrounding of CS-C (see Fig. 3).

[FIGURE] Fig. 3. CS (J=2[FORMULA]1) and (3[FORMULA]2) spectra towards CS-C. Positions are offsets in arcsec relative to [FORMULA]). The temperature scale is [FORMULA] K for both maps; velocity scale is [FORMULA] km s-1. The circles mark the position and size (FWHM) of CS-C.

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© European Southern Observatory (ESO) 1999

Online publication: September 2, 1999