J. Hawkes

The Mopra southern Galactic plane CO survey

We present the first results from a new carbon monoxide (CO) survey of the southern Galactic plane being conducted with the Mopra radio telescope in Australia. The 12 CO, 13 CO, and C 18 O J = 1‐0 lines are being mapped over the l = 305 ◦ ‐345 ◦ ,b =± 0.5 ◦ portion of the fourth quadrant of the Galaxy, at 35 arcsec spatial and 0.1 km s −1 spectral resolution. The survey is being undertaken with two principal science objectives: (i) to determine where and how molecular clouds are forming in the Galaxy and (ii) to probe the connection between molecular clouds and the ‘missing’ gas inferred from gamma-ray observations. We describe the motivation for the survey, the instrumentation and observing techniques being applied, and the data reduction and analysis methodology. In this paper, we present the data from thefirst degree surveyed, l = 323 ◦ ‐324 ◦ ,b =± 0.5 ◦ . We compare the data to the previous CO survey of this region and present metrics quantifying the performance being achieved; the rms sensitivity per 0.1 km s −1 velocity channel is 1.5 K for 12 CO and 0.7 K for the other lines. We also present some results from the region surveyed, including line fluxes, column densities, molecular masses, 12 CO/ 13 CO line ratios, and 12 CO optical depths. We also examine how these quantities vary as a function of distance from the Sun when averaged over the 1 square degree survey area. Approximately 2 × 10 6 M� of molecular gas is found along the G323 sightline, with an average H2 number density of nH 2 ∼ 1c m −3 within the Solar

Investigation of Dense Gas Towards Relativistic Outflow Sources

We probe the interstellar medium towards the objects Circinus X-1, a low-mass X-ray binary with relativistic jets; and the highly energetic Westerlund 2 stellar cluster, which is located towards TeV gamma-ray emission and interesting arc- and jet-like features seen in Nanten 12CO data. We have mapped both regions with the Mopra radio telescope, in 7 mm and 12 mm wavebands, looking for evidence of disrupted/dense gas caused by the interaction between high energy outflows and the ISM. Towards Westerlund 2, peaks in CS(J=1-0) emission indicate high density gas towards the middle of the arc and the endpoint of the jet; and radio recombination line emission is seen overlapping the coincident HII region RCW49. Towards Circinus X-1, 12CO(J = 1-0) Nanten data reveals three molecular clouds that lie in the region of Cir X-1. Gas parameters for each cloud are presented here.