ar X iv : a st ro - p h / 06 10 08 3 v 1 3 O ct 2 00 6 Mapping molecular emission in Vela Molecular Ridge Cloud D

We present the CO(1-0) and CO(2-1) line maps obtained observing with the SEST a ∼ 1 × 1 region of the Vela Molecular Ridge, Cloud D. This cloud is part of an intermediate-mass star forming region that is relatively close to the Sun. Our observations reveal, over a wide range of spatial scales (from ∼ 0.1 to a few parsecs), a variety of dense structures such as arcs, filaments and clumps, that are in many cases associated with far-IR point-like sources, recognized as young stellar objects and embedded star clusters. The velocity field analysis highlights the presence of possible expanding shells, extending over several parsecs, probably related to the star forming activity of the cloud. Furthermore, the analysis of the line shapes in the vicinity of the far-IR sources allowed the detection of 13 molecular outflows. Considering a hierarchical scenario for the gas structure, a cloud decomposition was obtained for both spectral lines by means of the CLUMPFIND algorithm. The CLUMPFIND output has been discussed critically and a method is proposed to reasonably correct the list of the identified clumps. We find that the corresponding mass spectrum shows a spectral index α ∼ 1.3÷ 2.0 and the derived clump masses are below the corresponding virial masses. The mass-radius and velocity dispersion-radius relationships are also briefly discussed for the recovered clump population. Subject headings: ISM: clouds — ISM: individual (Vela Molecular Ridge) — Stars: formation — radio lines: ISM — Submillimeter Dipartimento di Fisica, Università di Lecce, CP 193, I-73100 Lecce, Italy INAF Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy INAF Istituto di Fisica dello Spazio Interplanetario, Via Fosso del Cavaliere 100, I-00133 Roma, Italy Dipartimento di Fisica, Università degli Studi di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma, Italy INAF Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monteporzio Catone, Italy