The distribution of warm gas in the G327.3–0.6 massive star-forming region

Abstract

Aims. Most studies of high-mass star formation focus on massive and/or luminous clumps, but the physical properties of their larger scale environment are poorly known. In this work, we aim at characterising the effects of clustered star formation and feedback of massive stars on the surrounding medium by studying the distribution of warm gas through mid-J 12 CO and 13 CO observations. Methods. We present APEX 12 CO(6-5), (7-6), 13 CO(6-5), (8-7) and HIFI 13 CO(10-9) maps of the star forming region G327.36-0.6 with a linear size of ∼3 pc × 4 pc. We infer the physical properties of the emitting gas on large scales through a local thermodynamic equilibrium analysis, while we apply a more sophisticated large velocity gradient approach on selected positions. Results. Maps of all lines are dominated in intensity by the photon dominated region around the Hii region G327.3-0.5. Mid-J 12 CO emission is detected over the whole extent of the maps with excitation temperatures ranging from 20 K up to 80 K in the gas around the Hii region, and H 2 column densities from few 10 21 cm −2 in the inter-clump gas to 3 × 10 22 cm −2 towards the hot core G327.3-0.6. The warm gas (traced by 12 and 13 CO(6-5) emission) is only a small percentage (∼10%) of the total gas in the infrared dark cloud, while it reaches values up to ∼35% of the total gas in the ring surrounding the Hii region. The 12 CO ladders are qualitatively compatible with photon dominated region models for high density gas, but the much weaker than predicted 13 CO emission suggests that it comes from a large number of clumps along the line of sight. All lines are detected in the inter-clump gas when averaged over a large region with an equivalent radius of 50 (∼0.8 pc), implying that the mid-J 12 CO and 13 CO inter-clump emission is due to high density components with low filling factor. Finally, the detection of the 13 CO(10-9) line allows to disentangle the effects of gas temperature and gas density on the CO emission, which are degenerate in the APEX observations alone.

ATLASGAL-selected massive clumps in the inner Galaxy

“…Our study extends the work of Leurini et al (2013) on one source of our sample, AGAL327.293−00.579. They mapped in CO (3-2), CO (6-5), CO (7-6) and in 13 CO (6-5), 13 CO (8-7) and 13 CO (10-9) a larger area of the source than that presented here and found that, for all transitions, the spectra are dominated in intensity by the H II region rather than by younger sources (a hot core and an infrared dark cloud are also present in the area).…”

HERSCHELSURVEY OF GALACTIC OH+, H2O+, AND H3O+: PROBING THE MOLECULAR HYDROGEN FRACTION AND COSMIC-RAY IONIZATION RATE

“…G327.3-0.6 G327.3−0.6 is a hot core within a region of active star formation, and provides the longest line of sight probing the fourth Galactic quadrant in our study. Molecular emission lines give a systemic velocity of −44.5 km s −1 (San José-García et al 2013; Leurini et al 2013), and a distance of 3.3 kpc was determined via a kinematic analysis of H i absorption data (Urquhart et al 2012). OH + and o-H 2 O + show similar absorption profiles for the most part ( Figure 19).…”

Distribution of water in the G327.3–0.6 massive star-forming region

“…In addition to the water lines, a few lines from carbon species have been observed and are shown in Fig.13: 13 CO J=10-9, C 18 O J=9-8, and CS J=11-10. These three lines are in emission and centered at -44.8 km s −1 , hence at a slightly redshifted velocity compared to what derived Rolffs et al (2011) and Leurini et al (2013) from ground observations. Line profiles exhibit a cavity shock component of 5.3-6.5 km s −1 , but a broader component (FWHM∼11 km s −1 ) is also observed for the 13 CO J=10-9 line.…”

“…Interestingly, the emission detected in H 2 O is always redshifted compared to the 13 CO(10-9) line ( Fig. 11(b)), which was observed simultaneously to the 1113 GHz line (presented in Leurini et al, 2013). The 13 CO(10-9) seems to be associated with the absorption at ∼ −50 km s −1 and peaked at the same velocity as the CO lines observed in Leurini et al (2013).…”

“…Three water lines as well as the 13 CO(10-9) (Leurini et al, 2013) and C As with all massive protostars observed by the WISH GT-KP, 14 water lines (see Table 1) were observed with HIFI in the pointed mode at frequencies between 547 and 1670 GHz in 2010 and 2011 (list of observation identification numbers, obsids, are given in Table 1) toward the G327 hot core region (RA=15h53m08.8s, DEC= -54 • 37'01"), between SMM2 and the hot core position (see Sect. 3.3) because of a confusion between different references (e.g., Bergman, 1992).…”