Catherine Braiding

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

The Hall effect in accretion flows

Magnetic diffusion in accretion flows changes the structure and angular momentum of the accreting material. We present two power-law similarity solutions for flattened accretion flows in the presence of magnetic diffusion: a secularly evolving Keplerian disc and a magnetically diluted free fall on to the central object. The influence of Hall diffusion on the solutions is evident even when this is small compared to ambipolar and Ohmic diffusion, as the surface density, accretion rate and angular momentum in the flow all depend upon the product , and the inclusion of Hall diffusion may be the solution to the magnetic braking catastrophe of star formation simulations.

LORD OF THE RINGS: A KINEMATIC DISTANCE TO CIRCINUS X-1 FROM A GIANT X-RAY LIGHT ECHO

Circinus X-1 exhibited a bright X-ray flare in late 2013. Follow-up observations with Chandra and XMM-Newton from 40 to 80 days after the flare reveal a bright X-ray light echo in the form of four well-defined rings with radii from 5 to 13 arcmin, growing in radius with time. The large fluence of the flare and the large column density of interstellar dust toward Circinus X-1 make this the largest and brightest set of rings from an X-ray light echo observed to date. By deconvolving the radial intensity profile of the echo with the MAXI X-ray light curve of the flare we reconstruct the dust distribution toward Circinus X-1 into four distinct dust concentrations. By comparing the peak in scattering intensity with the peak intensity in CO maps of molecular clouds from the Mopra Southern Galactic Plane CO Survey we identify the two innermost rings with clouds at radial velocity and , respectively. We identify a prominent band of foreground photoelectric absorption with a lane of CO gas at . From the association of the rings with individual CO clouds we determine the kinematic distance to Circinus X-1 to be . This distance rules out earlier claims of a distance around , implies that Circinus X-1 is a frequent super-Eddington source, and places a lower limit of on the Lorentz factor and an upper limit of on the jet viewing angle.

The Carina Nebula and Gum 31 molecular complex – I. Molecular gas distribution, column densities, and dust temperatures

We report high resolution observations of the

The Mopra southern Galactic plane CO survey - data release 1

^{12}

Extended Carbon Line Emission in the Galaxy: Searching for Dark Molecular Gas along the G328 Sightline

CO

THE CARBON INVENTORY IN A QUIESCENT, FILAMENTARY MOLECULAR CLOUD IN G328

(1\rightarrow0)

ATLASGAL --- properties of a complete sample of Galactic clumps

and

RCW 36 in the Vela Molecular Ridge: Evidence for high-mass star-cluster formation triggered by cloud–cloud collision

^{13}

The Carina Nebula and Gum 31 molecular complex – II. The distribution of the atomic gas revealed in unprecedented detail

CO