Radio observations of some details in the H I local spiral arm

Extract

The observations were made with the large Pulkovo radiotelescope (beamwidth 7′, bandwidth 20 and 10 kHz). Figure 1 contains our drift curves across the cluster NGC 2264. The details on them may be identified with Raimond's (1966) clouds, but the proofs for the reality of the connection between the cluster and the clouds are not very reliable. The cloud ‘b’ is believed to be connected with NGC 2264 because of their close neighborhood. But on the other side of the galactic plane in this region we have found a bright and narrow (∼1°) detail, whose middle falls exactly on the western border of the H II region around the star λ Orionis (Figure 2). Figure 3 contains the computed drift curves at different velocities for Δf = 20 kHz according to the model of the neutral hydrogen expanding envelope proposed by Wade (1957) around the H II region λ Ori. Figure 4 represents our observations. Although some details, in particular the narrow detail at the velocity −1.4 km s⁻¹, are very similar to the calculated ones, our observations differ from Wade's model in that they do not have any velocity symmetry relative to zero; in fact the details are situated only at the positive side. This fact may eliminate one half of the proposed envelope. There is no symmetry relative to the central star and no coincidence of the velocity of the narrowest detail with the velocities of the central star and nebula.