MODERATE-DENSITY REGIONS IN THE LYNDS-134 CLOUD COMPLEX

IRAS images, carbon monoxide observations at 2.7 mm (CO, (CO)-C-13, an d (CO)-O-18), and blue extinction from star counts have been used for a large-scale study of the L134 complex of high-latitude clouds. We ha ve correlated the different tracers in order to investigate the range of physical conditions for which these tracers apply. We find tight li near correlations between (CO)-C-13 and A(B) and between (CO)-C-13 and Delta I-100. The quantity Delta I-100 is the infrared emission of inn er cloud regions obtained from the relationship Delta I-100 = I-60/The ta, where Theta is the value for I-60/I-100 in the outer regions of th e clouds. We find that Delta I-100 probes the same regions as (CO)-C-1 3 and can therefore be used to predict the (CO)-C-13 emission. From th e correlation between (CO)-C-13 and A(B) and the CO measurements we de termine an average (CO)-C-13 abundance in the complex which does not d iffer significantly from other studies. However, the abundance in the translucent cloud L1780 is about a factor of 4 lower than in the opaqu e clouds L134, L183, and L169. Using the (CO)-C-13 observations we hav e compiled the properties of 18 clumps in the complex. The clumps foll ow clear luminosity-size and size-line width relationships. The size-l ine width relationship is consistent with a power law with exponent 0. 5. The derived ambient pressure acting on the clumps is of order p/k = 2 x 10(4) K cm(-3). Both molecular and infrared data show that the UV radiation held in the complex is anisotropic. This is consistent with the presence of the nearby UV sources zeta Oph and the Upper Scorpius OB association. The densest regions in the complex as delineated by t he ammonia cores can be found close to the few-illumination edges of t he clouds. In addition, a higher density contrast on the shadow side c an be observed. These observations support the view that the anisotrop ic UV field affects the density distribution in the clouds and that th e increased strength of the UV field causes a bigger halo on the illum inated side. The influence of the UV field on the appearance of clouds is most evident in the outer layers of a cloud. The inner, denser, an d well-shielded parts seem much more similar, judging by the uniform b ehavior of most tracers. However, the displacement of the ammonia core s with respect to the cloud centers suggests the effects of the anisot ropy extend down to the densest layers of the clouds.