2006A&A...450..193H

Small-area molecular structures (SAMS) resembling clumpuscules proposed as candidates for baryonic dark matter, have been detected in an area where the shielding is too low for them to survive for a long time. I present the results of an unbiased deep search for molecular clumpuscules to study the frequency of occurence of such structures. The area surrounding these structures has been surveyed using the FCRAO 14m telescope in the CO (1-0) transition. The field covered is 20' by 20'. The resulting rms of the data is only 0.04K in a 0.127km/s wide channel. Additionally, high-angular resolution observations of the ¹³CO and C¹⁸O (J=1-0) transitions were obtained with the IRAM Plateau-de-Bure Interferometer. 3 new SAMS have been detected. The structures have very low intensities which makes it impossible to detect them in large scale CO surveys conducted to map the molecular gas of the Milky Way. Their radial velocity is similar to that of the surrounding HI gas. The clouds follow the same size-linewidth relation as found for giant molecular clouds or Galactic cirrus clouds. The observations clearly show that most of the large linewidths observed at low angular resolution are caused by a large velocity difference between the clumps seen at highest angular resolution. The non-detection of the structures in the high-angular resolution observations of the ¹³CO and C¹⁸O (J=1-0) transitions shows that the ¹²CO