Star Formation in NGC 6334 I and I(N)

The northern section of the molecular cloud complex NGC 6334 has been mapped in the CO and CS spectral line emission and in continuum emission at a wavelength of 1300um. Our observations highlight the two dominant sources, I and I(N), and a host of weaker sources. NGC 6334 I is associated with a cometary ultra-compact HII region and a hot, compact core $lt;~10" in size. Mid-IR and CH3OH observations indicate that it is also associated with at least two protostellar sources, each of which may drive a molecular outflow. For region I we confirm the extreme high velocity outflow first discovered by Bachiller & Cernicharo (1990) and find that it is very energetic with a mechanical luminosity of 390 L_o. A dynamical age for the outflow is ~3000 years. We also find a weaker outflow originating from the vicinity of NGC 6334 I. In CO and CS this outflow is quite prominent to the NW, but much less so on the eastern side of I, where there is very little molecular gas. Spectral survey data show a molecular environment at position I which is rich in methanol, methyl formate, and dimethyl ether, with lines ranging in energy up to 900 K above the ground state. NGC 6334 I(N) is more dense than I, but cooler, and has none of the high excitation lines observed toward I. I(N) also has an associated outflow, but it is less energetic than the outflow from I. The fully sampled continuum map shows a network of filaments, voids, and cores, many of which are likely to be sites of star formation. A striking feature is a narrow, linear ridge that defines the western boundary. It is unclear if there is a connection between this filament and the many potential sites of star formation, or if the filament existed prior to the star formation activity.

Fig. 1 (left): Map of the CO J=3-2 line emission integrated over the velocity ranges -40 to -12 km s^-1 (blue), and +3-+35 km s^-1 (red) to indicate the blue and red shifted wings. The contour levels are 20, 40, 60, 80, 100, 150, 200, 250, 500, 750, 1000, 1250, 1500, and 2000 K km s^-1. The sampling interval over most of the map is 10". The principal features, NGC 6334I, I(N), and I(NW), are labelled. Also shown are the positions of the HII-regions E and F (Rodriguez, Canto & Moran 1982; Harvey & Gatley 1983), CH₃OH maser (Menten & Batrla 1989; Norris et al. 1993; Ellingsen et al. 1996; Norris et al. 1998; Kogan & Slysh 1998), OH maser (Forster & Caswell 1989), H₂O maser (Moran & Rodriguez 1980; Forster & Caswell 1989), NH₃ maser (Kraemer & Jackson 1995), H₂ knot (Davis & Eisloffel 1995), 20 um sources IRS-I-1,2,3 (Harvey & Gatley 1983), and sub-mm sources (this paper; Sandell 2000). For the methanol masers in I(N), the one labelled is believed to be Class II. The others in I(N) are Class I. The methanol masers in I belong to both classes.

Fig. 2 (right): Map of the 1300 um emission around both I(N) and I. The contours are 0.05, 0.1, 0.15, 0.2, 0.25, 0.35, 0.45, 0.6, 0.8, 1.0, 1.25, 1.5, 2.0, 3.0, 4.0, 4.5 Jy/beam. The map has been reduced with DBMEM and smoothed with a 6", Gaussian. All continuum sources identified by Sandell (2000) are marked by the star symbol (black or white) and all sources except I and I(N) are labelled with the prefix SM.