D. J. Eden

ATLASGAL – properties of compact H ii regions and their natal clumps

We present a complete sample of molecular clumps containing compact and ultracompact (UC) Hii regions betweenl = 10 ◦ and 60 ◦ and|b|< 1 ◦ , identified by combining the the ATLASGAL sub-mm and CORNISH radio continuum surveys wit h visual examination of archival infrared data. Our sample is complete to optically thin, compact and UC Hii regions driven by a zero age main sequence star of spectral type B0 or earlier embedded within a 1,000 M⊙ clump. In total we identify 213 compact and UC Hii regions, associated with 170 clumps. Unambiguous kinematic distances are derived for these clumps and used to estimate their masses and physical sizes, as well as the Lyman continuum fluxes and sizes of their embedded Hii regions. We find a clear lower envelope for the surface densit y of molecular clumps hosting massive star formation of 0.05 g cm −2 , which is consistent with a similar sample of clumps associated with 6.7 GHz masers. The mass of the most massive embedded stars is closely correlated with the mass of their natal clump. Young B stars appear to be significantly more luminous in the ultraviolet than predicted by current stellar atmosphere models. The properties of clumps associated with compact and UC Hii regions are very similar to those associated with 6.7 GHz methanol masers and we speculate that there is little evolution in the structure of the molecular clumps between these two phases. Finally, we identify a significant peak in the surface density of compact and UC Hii regions associated with the W49A star-forming complex, noting that this complex is truly one of the most massive and intense regions of star formation in the Galaxy.

Star formation towards the Scutum tangent region and the effects of Galactic environment

By positional matching to the catalogue of Galactic Ring Survey molecular clouds, we have derived distances to 793 Bolocam Galactic Plane Survey (BGPS) sources out of a possible 806 located within the region defined by Galactic longitudes l= 28°.5–31°.5 and latitudes |b|≤ 1°. This section of the Galactic plane contains several major features of Galactic structure at different distances, mainly mid-arm sections of the Perseus and Sagittarius spiral arms and the tangent of the Scutum–Centaurus arm, which is coincident with the end of the Galactic long bar. By utilizing the catalogued cloud distances plus new kinematic distance determinations, we are able to separate the dense BGPS clumps into these three main line-of-sight components to look for variations in star formation properties that might be related to the different Galactic environments. We find no evidence of any difference in either the clump mass function or the average clump formation efficiency (CFE) between these components that might be attributed to environmental effects on scales comparable to Galactic structure features. Despite having a very high star formation rate, and containing at least one cloud with a very high CFE, the star formation associated with the Scutum–Centaurus tangent does not appear to be in any way abnormal or different to that in the other two spiral arm sections. Large variations in the CFE are found on the scale of individual clouds, however, which may be due to local triggering agents as opposed to the large-scale Galactic structure.

Star formation in Galactic spiral arms and the interarm regions

The line of sight through the Galactic plane between longitudes l = 37°83 and 42°50 allows for the separation of Galactic Ring Survey molecular clouds into those that fall within the spiral arms and those located in the interarm regions. By matching these clouds in both position and velocity with dense clumps detected in the mm continuum by the Bolocam Galactic Plane Survey, we are able to look for changes in the clump formation efficiency (CFE), the ratio of clump to cloud mass, with Galactic environment. We find no evidence of any difference in the CFE between the interarm and spiral-arm regions along this line of sight. This is further evidence that, outside the Galactic Centre region, the large-scale structures of the Galaxy play little part in changing the dense, potentially star-forming structures within molecular clouds.

CHIMPS: the 13CO/C18O (J = 3 → 2) Heterodyne Inner Milky Way Plane Survey

We present the

The almost ubiquitous association of 6.7-GHz methanol masers with dust

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The JCMT Plane Survey: early results from the ℓ = 30° field

CO/C

Star formation scales and efficiency in Galactic spiral arms

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The RMS survey: ammonia mapping of the environment of massive young stellar objects

O (J=3-2) Heterodyne Inner Milky Way Plane Survey (CHIMPS) which has been carried out using the Heterodyne Array Receiver Program on the 15 m James Clerk Maxwell Telescope (JCMT) in Hawaii. The high-resolution spectral survey currently covers |b| < 0.5 deg and 28 < l < 46 deg, with an angular resolution of 15 arcsec in 0.5 km/s velocity channels. The spectra have a median rms of

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

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Spatial distribution of star formation related to ionized regions throughout the inner Galactic plane

0.6 K at this resolution, and for optically thin gas at an excitation temperature of 10 K, this sensitivity corresponds to column densities of