We have estimated the fractal dimension of the molecular clouds associated with the H ΙΙ region Sh 156 in the Outer Galaxy. We selected the 12CO cube data from the FCRAO CO Survey of the Outer Galaxy. Using a developed code within IRAF, we identified slice-clouds (2-dimensional clouds in velocity-channel maps) with two threshold temperatures to estimate the fractal dimension. With the threshold temperatures of 1.8 K, and 3 K, we identified 317 slice-clouds and 217 slice-clouds, respectively. There seems to be a turn-over location in fractional dimension slope around NP (area; number of pixel) = 40. The fractal dimensions was estimated to be D = 1.5 ∼ 1.53 for NP ≥ 40, where P ∝ AD/2 (P is perimeter and A is area), which is slightly larger than other results. The sampling rate (spatial resolution) of observed data must be an important parameter when estimating fractal dimension. Fractal dimension is apparently invariant when varying the threshold temperatures applied to slice-clouds identification.

We have calculated 2448 interstellar cloud models to investigate the formation and destruction of high rotational level H2 according to the combinations of five physical conditions: the input UV intensity, the H2 column density, cloud temperature, total density, and the H2 formation rate efficiency. The models include the populations of all the accessible states of H2 with the rotational quantum number J < 16 as a function of depth through the model clouds, and assume that the abundance of H2 is in a steady state governed primarily by the rate of formation on the grain surfaces and the rates of destruction by spontaneous fluorescent dissociation following absorption in the Lyman and Werner band systems. The high rotational levels J = 4 and J = 5 are both populated by direct formation into these levels of newly created molecules, and by pumping from J = 0 and J = 1, respectively The model results show that the high rotational level ratio N(4)/N(0) is proportional to the incident UV intensity, and is inversely proportional to the H2 molecular fraction, as predicted in theory.

We have estimated the fractal dimension of the molecular clouds in the Antigalactic Center based on the 12CO (J = 1- 0) and 13CO (J = 1- 0) database obtained using the 14m telescope at Taeduk Radio Astronomy Observatory. Using a developed code within IRAF, we were able to identify slice-clouds, and determined the dispersions of two spatial coordinates as well as perimeters and areas. The fractal dimension of the target region was estimated to be D = 1.34 for low resolution 12CO (J = 1 - 0) database, and D = 1.4 for higher resolution 12CO (J = 1 - 0) and 13CO (J = 1 - 0) database, where P ∝ AD/2. The sampling rate (spatial resolution) of observed data must be an important parameter when estimating fractal dimension. Our database with higher resolution of 1 arcminute, which is corresponding to 0.2 pc at a distance of 1.1 kpc, gives us the same estimate of fractal dimension to that of local dark clouds. Fractal dimension is apparently invariant when varying the threshold temperatures applied to cloud identification. According to the dispersion pattern of longitudes and latitudes of identified slice-clouds, there is no preference of elongation direction.

We have made an extensive mapping of the 13CO 13CO J=1-0 transition line in the dark cloud L1535. We also constructed the 100μm 100μm IRAS map in the region. We found a semi-detached cloud component of 13CO 13CO in the northeast direction of the 13CO 13CO main cloud which forms a dumbbell-like structure. This additional component with an angular size of 20′×16′ 20′×16′ has not been observed before in any molecular surveys of the cloud. The IRAS map shows a similar structure with two intensity peaks whose positions coincide with those of the 13CO 13CO clouds.

We present a code which identifies individual clouds in crowded region using IMFORT interface within Image Reduction and Analysis Facility (IRAF). We define a cloud as an object composed of all pixels in longitude, latitude, and velocity that are simply connected and that lie above some threshold temperature. The code searches the whole pixels of the data cube in efficient way to isolate individual clouds. Along with identification of clouds it is designed to estimate their mean values of longitudes, latitudes, and velocities. In addition, a function of generating individual images (or cube data) of identified clouds is added up. We also present identified individual clouds using a 12CO survey data cube of Galactic Anticenter Region (Lee et al. 1997) as a test example. We used a threshold temperature of 5σ 5σ rms noise level of the data With a higher threshold temperature, we isolated subclouds of a huge cloud identified originally. As the most important parameter to identify clouds is the threshold value, its effect to the size and velocity dispersion is discussed rigorously.

We have searched for the 2 mm transitions of H 2 C O H + ( 2 02 − 1 01 ) and H 2 13 C O ( 2 02 − 1 01 , 2 12 − 1 11 , a n d 2 11 − 1 10 ) toward the dense interstellar molecular clouds Orion A, TMC-1 and L134N using the FCRAO 14 m telescope. None of the transitions have been detected except the H 2 13 C O transitions toward Orion-KL. We set upper limits for the abundances of the protonated formaldehyde ion ( H 2 C O H + ) , which are close to the abundances expected from ion-molecule chemistry.

In order to know how the magnetic field increases with density in interstellar clouds, we have analyzed observations of extinction and polarization for stars in the ρ Oph molecular cloud complex. The size of grains in dense parts of the complex is estimated to be larger than the ones in diffuse interstellar clouds by about 15 percent in radii. Employing the Davis-Greenstein mechanism for grain alignment with this estimated grain size, we have put constraints on the exponent in the field-density relation B ∝ n x : 1 / 5 ≤ x ≤ 1 / 3 . It is concluded that magnetic field in gravitationally contracting clouds increases less steeply than the classical expectation based on the approximation of isotropic contraction with complete frozen-in flux.

The abundances of simple molecules are examined in terms of the time-dependent cloud evolution. The formation and destruction mechanisms of H 2 C O are reviewed. The average value of the fractional abundance of H 2 C O is derived to be in the range of 10 − 10 t o 5 × 10 − 9 . This is comparable to the observed values. The expected variations of the molecules formed from or destroyed by CO, CI, and C + whose abundances depend on the evolutionary state of the cloud are discussed.