Appendix A: Distribution of the HI around L 1340

Figure A.1: H I spectrum at $l=130\hbox{$.\!\!^\circ$ }5, b=+11\hbox{$.\!\!^\circ$ }5$ taken from the Leiden-Dwingeloo survey. The angular resolution of the survey is 0 $.\!\!^\circ$5, and the spectral resolution is 1.03 km s-1. Dotted vertical lines indicate the radial velocity range of the molecular cloud.

The angular resolution of the Leiden-Dwingeloo H I survey data is 0 $.\!\!^\circ$6, corresponding to 6.3 pc at the distance of L 1340, and the velocity resolution is 1.03 km s^-1. Figure A.1 shows the H I spectrum at (130 $.\!\!^\circ$5,+11 $.\!\!^\circ$5), and in the velocity interval $-40~{\rm km~s}^{-1} < v_{{\rm LSR}} < +10~{\rm km~s}^{-1}$. The peak at 0 km s^-1 probably corresponds to the atomic cloud associated with the molecular cloud L 1333 located at a distance of 180 pc around (l,b) = (128 $.\!\!^\circ$9,13 $.\!\!^\circ$7), and at the same mean radial velocity (Obayashi et al. 1998). The highest peak of the spectrum at $v_{{\rm LSR}}=-13$ km s^-1 represents the H I cloud enveloping L 1340. The characteristic line width of this spectral feature is $\sim$7 km s^-1.

Figure A.2 shows the distribution of the neutral hydrogen integrated over the velocity interval $-18~{\rm km~s}^{-1} < v_{{\rm LSR}} < -8~{\rm km~s}^{-1}$. A large, elongated H I structure can be seen in the area $126\hbox{$^\circ$ }\leq l \leq 142\hbox{$^\circ$ }$ and $+7\hbox{$^\circ$ }\leq b \leq +13\hbox{$^\circ$ }$ in this radial velocity interval. Its radius, derived from the area within the half-maximum contour, is $\sim$38 pc. The apparent local minimum in H I near the molecular cloud may result both from self-absorption and conversion of a part of hydrogen into molecules. The H I column densities displayed in Fig. A.2 were estimated assuming optically thin emission, i.e. using the relationship

$$% N(\mbox{H {\sc i}})=1.8224\times10^{18} \int \!T_b {\rm d}v~ {\rm cm^{-2}\left(K~km~s^{-1}\right)^{-1}}$$ (A.1)

(Rohlfs & Wilson 2000). The mass of the H I structure, estimated via summing up the column densities inside the half-maximum contour is M(H I) $\geq 2~\times 10^{4}~M_{\odot}$, comparable with those of some well known nearby molecular cloud complexes (e.g. Taurus), and an order of magnitude larger than the mass of the molecular cloud.

Figure A.2: Distribution of the neutral hydrogen over a $30\hbox {$^\circ $ }\times 15\hbox {$^\circ $ }$area including L 1340, integrated over the velocity interval $-18~{\rm km~s}^{-1} < v_{{\rm LSR}} < -8~{\rm km~s}^{-1}$, taken from the Leiden-Dwingeloo survey. The only known molecular cloud in this area is L 1340, marked by the circle. Column densities were derived assuming optically thin emission. The lowest contour is at $3\times~10^{20}$ cm-2, and the increment is 1020 cm-2.