The Thumbprint nebula: the distribution of molecular gas and dust in a regular BOK globule.

We have studied a regular bright-rimmed globule called Thumbprint Nebula, TPN, (size ~0.18pc, distance ~200pc) in millimeter molecular lines (CO isotopic lines), at optical wavelengths (scanned Schmidt plates) and at infrared wavelengths (IRAS maps and scans). The molecular line observations have been made with SEST in ^12^CO(J=1-0) and (J=2-1), ^13^CO(J=1-0) and (J=2-1), C^18^O(J=1-0), C^17^O(J=1-0), CS(J=2-1) and HNC(J=1-0) transitions. These observations reveal a centrally condensed cloud with an excitation temperature of T_ex_=~6.6K, and a mass of 6M_sun_. There is indication of a cloud rotation with a rotation rate of ~0.6km/s/pc, as measured using ^13^CO lines. The rotational axis (projection on sky) is parallel to the minor axis of the cloud. The ratio between the turbulent, thermal and rotational energies is E_turb_:E_therm_:E_rot_(sini)^-2^=1:0.6:0.03(sini)^-2^, where i is the angle between the rotational axis and the line of sight. As a result of the low kinetic temperature the turbulent energy is more important supporting force than the thermal energy. The ratio of the potential energy and the kinetic energy is found to be |E_pot_|/E_kin_=~0.9, thus the cloud is in or near the state of virial equilibrium. High angular resolution (20") C^18^O observations have enabled us to determine the spatial density distribution of the dense gas in the centre of the cloud. The distribution can be well fitted using a density law of the form n(r)=n_0_exp(-(r/r_0_)^gamma^), where n_0_ is the central density, r is the distance from the center, and r_0_ and γ are free parameters. Optical surface brightness distribution as measured from blue and red ESO/SRC Schmidt plates has been used to determine the distribution of the dust particles in comparison with the distribution of the gas component. The position of the surface brightness minimum, which corresponds to the dust density maximum, is found to be about 40" to 50" north of the ^13^CO and C^18^O column density maximum. Our interpretation is that the dust is protecting molecules against the UV-radiation coming from the galactic disk (on the northern side of the TPN), causing the molecular density maximum to shift towards south. We have made infrared surface brightness maps using the IRAS ISSA survey plates at 12, 25, 60 and 100μm and extracted individual IRAS scans crossing the TPN. The globule is seen at 100 and 60μm, but the dust is apparently too cold to be visible at shorter wavelengths.