The Structure and Evolution of the Lagoon Nebula. I. Submillimeter Continuum and CO Line Mapping

Abstract

We present submillimeter-and millimeter-wave maps tracing the molecular gas and dust around the edge of the H ii region M8. The molecular material is clumped into cores on the scale of the beam (about 0.1 pc) whose temperatures can be estimated from CO observations. The masses of the clumps, estimated from their continuum fluxes, are consistent with a power-law mass function with index À1:7 AE 0:6, which agrees with determinations for other molecular clouds at similar resolutions, using molecular lines as tracers. The submillimeter clumps are sited at the interface between the H ii region and the background molecular cloud, where they are exposed to the ultraviolet flux of OB stars. The physical parameters of the clumps are compared to published models of molecular clouds undergoing photoevaporation, suggesting that the pressure of the ionized gas exceeds the internal pressure of the clumps and, therefore, that a shock front will be driven into the clumps. The clumps themselves currently appear to be gravitationally unbound, but the compression may be sufficient to induce collapse.

Classical T Tauri stars with VPHAS+ – I. H α andu-band accretion rates in the Lagoon Nebula M8

“…A HerbigHaro object has also been reportedly found by Arias et al (2006). The O6 Ve star HD 165052, which is a confirmed member of the Lagoon nebula (Tothill et al 2002) lies at the eastern edge of the rim.…”

“…Adopting the mean molecular cloud properties of the south eastern gas clumps derived by Tothill et al (2002), where the mean molecular density is 4.46 × 10 4 cm −3 , and mean gas temperature around 25 K we find the Jeans length (Jeans 1928) to be 0.15 pc. The median observed spacing of Class I objects is roughly similar to the Jeans length.…”

“…(i) in the southern bright rim M8 E. Tothill et al (2002) identified several gas clumps within this region. A HerbigHaro object has also been reportedly found by Arias et al (2006).…”

“…In Fig. 20, 850 µm SCUBA contours spanning the southern filamentary arc (Tothill et al 2002) are overlaid on the Hα image. Protostars are located within the molecular gas clumps, while CTTS are situated at the edges.…”

The Giant Molecular Cloud associated with RCW 106

“…6 and n is the density in cm −3 . Tothill et al (2002) and gaussclumps (Stutzki & Güsten 1990;Kramer et al 1998) both of which decompose the observed emission into discrete clumps. The masses derived using clumpfind are already presented in Table 1.…”