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Results scientific researchs 19
Scaling relations and intrinsic motions in the interstellar neutral hydrogen clouds
(1999)

Diameters, masses and velocity dispersions of about 7600 HI clouds were determined on the base of HI RATAN-600 Survey in the second and third quadrants of galactic longitudes in 180 degree < l < 260 degree, -15 dg. < b < +15 dg. and
100 dg. < l < 150 dg., -10 dg. < b < +10 dg..
It is found that mean clouds linear diameters along Galactic plane are 2.5 times greater than in transverse direction.
The relation between HI concentrations and cloud diameters in the form of nH proportionalli d-1.25+-0.01 is confirmed regardless of selection effects. The correlation coefficient between log nH and log d is equal -0.87 (figure 1).
It is shown that other important dependence - velocity dispersion versus cloud diameters, that is found from molecular clouds, in the case of HI clouds is completely absent ( figure 2 ).
This is probably due to negligible role of intrinsic turbulence in the HI clouds. It is found that 36% of HI clouds have systematic velocity gradient across cloud disks that is may be due to clouds rotation. This phenomenon may explain rather high velocity widths of HI line profiles. Mean clouds angular rotational velocity is about 10-13 radians * s-1, mean rotational energy is about 1048 ergs, that is comparable to the energy of random cloud motions. Finally, observable quantities of clouds with opposite directions of rotation are equal within 5% in both galactic quadrants investigated.


Figure 1. The dependence of HI atomic density in the clouds from their linear diameters for 7710 clouds at II and III galactic quadrants.



Figure 2. The dependence of HI emission line halfwidths in the clouds from their linear diameters.