We present the results of a high sensitivity survey for 6.7 GHz methanol masers towards 22 GHz water masers using the 100 m Efflesberg telescope. A total of 89 sources were observed and 10 new methanol masers were detected. The new detections are relatively faint with peak flux densities of between 0.5 and 4.0 Jy. A nil detection rate from low-mass star forming regions enhances the conclusion that the masers are only associated with massive star formation. Even the faintest methanol maser in our survey, with a luminosity of 1.1 × 10 −9 L , is associated with massive stars, as inferred from its infrared luminosity.

The CORNISH project is the highest resolution radio continuum survey of the Galactic plane to date. It is the 5 GHz radio continuum part of a series of multi-wavelength surveys that focus on the northern GLIMPSE region (10 • < l < 65 • ), observed by the Spitzer satellite in the mid-infrared. Observations with the Karl G. Jansky Very Large Array (VLA) in B and BnA configurations have yielded a 1.5 ′′ resolution Stokes I map with a root-mean-squared noise level better than 0.4 mJy beam −1 . Here we describe the data-processing methods and data characteristics, and present a new, uniform catalogue of compact radioemission. This includes an implementation of automatic deconvolution that provides much more reliable imaging than standard CLEANing. A rigorous investigation of the noise characteristics and reliability of source detection has been carried out. We show that the survey is optimised to detect emission on size scales up to 14 ′′ and for unresolved sources the catalogue is more than 90 percent complete at a flux density of 3.9 mJy. We have detected 3,062 sources above a 7σ detection limit and present their ensemble properties. The catalogue is highly reliable away from regions containing poorly-sampled extended emission, which comprise less than two percent of the survey area. Imaging problems have been mitigated by downweighting the shortest spacings and potential artefacts flagged via a rigorous manual inspection with reference to the Spitzer infrared data. We present images of the most common source types found: H II regions, planetary nebulae and radio-galaxies. The CORNISH data and catalogue are available online at http://cornish.leeds.ac.uk.Note.-The properties of the data differ in the combination of antenna types included in the array, the configuration of the array, the weather experienced and the declination range observed. Unless otherwise noted the weather during the observations was reasonable.

We present the results of an unbiased survey for 6.7 GHz methanol masers in the Galactic plane carried out using the 305 m Arecibo radio telescope. A total of 18.2 deg 2 was surveyed with uniform sampling at 35:2 l 53:7 , jbj 0:41 . The large collecting area of Arecibo and the sensitive C-Band High receiver allowed the survey to be complete at the level of 0.27 Jy, making this the most sensitive blind survey carried out to date. We detected a total of 86 sources, 48 of which are new detections. Most of the new detections have a peak flux density below 2 Jy. Many methanol masers are clustered, reflecting the formation of massive stars in clusters.

We present accurate absolute astrometry of 6.7 GHz methanol masers detected in the Arecibo Methanol Maser Galactic Plane Survey using MERLIN and the Expanded Very Large Array (EVLA). We estimate the absolute astrometry to be accurate to better than 15 and 80 milliarcseconds for the MERLIN and EVLA observations respectively. We also derive the morphologies of the maser emission distributions for sources stronger than ∼ 1 Jy. The median spatial extent along the major axis of the regions showing maser emission is ∼ 775 AU. We find a majority of methanol maser morphologies to be complex with some sources previously determined to have regular morphologies in fact being embedded within larger structures. This suggests that some maser spots do not have a compact core, which leads them being resolved in high angular resolution observations. This also casts doubt on interpretations of the origin of methanol maser emission solely based on source morphologies. We also investigate the association of methanol masers with mid-infrared emission and find very close correspondence between methanol masers and 24 µm point sources. This adds further credence to theoretical models that predict methanol masers to be pumped by warm dust emission and firmly reinforces the finding that Class II methanol masers are unambiguous tracers of embedded high-mass protostars.

The consortium for Galactic studies with the Arecibo L-band Feed Array (ALFA) is conducting a neutral hydrogen (HI) survey of the whole Arecibo sky (declination range from −1 • to 38 • ), with high angular (3.5 ′ ) and velocity resolution (0.2 km s −1 ). The precursor observations with ALFA of a region in the Galactic anti-center reveal numerous isolated, small (a few pc in size), and cold (T k < 400 K) HI clouds at low negative velocities, distinctly separated from the HI disk emission ('low-velocity clouds', LVCs). These clouds are most likely located in the transition region between the Galactic disk and halo (at scale heights of 60-900 pc), yet they have properties of typical cold neutral clouds. LVCs are colder and, most likely, smaller and less massive than Lockman's clouds in the disk/halo interface region of the inner Galaxy. Our observations demonstrate that the cloudy structure of the interface region is most likely a general phenomenon, not restricted to the inner Galaxy. LVCs have sizes and radial velocities in agreement with the expectations for clouds formed in low-temperature fountain flows, although we measure a factor of ten higher HI column densities. Alternatively, LVCs could represent the final stages of the infalling intergalactic material in the on-going construction of the Galaxy.In the same dataset at higher negative velocities, we have discovered a 'companion' HI cloud located 50 ′ southwest of CHVC186+19-114. CHVC186+19-114 is a typical compact high velocity cloud (HVC) with a well-defined core/envelope structure. The companion cloud has a diameter of only 7 ′ × 9 ′ , and is one of the smallest HVCs known, most likely stripped from the main cloud through the interactions with the halo medium.