We have constructed the largest sample of dust-associated class II 6.7 GHz methanol masers yet obtained. New measurements from the the Methanol MultiBeam (MMB) Survey were combined with the 870 µm APEX Telescope Large Area Survey of the Galaxy (AT-LASGAL) and the 850 µm JCMT Plane Survey (JPS). Together with two previous studies we have now identified the host clumps for 958 methanol masers across the Galactic Plane, covering approximately 99 per cent of the MMB catalogue and increasing the known sample of dust-associated masers by over 30 per cent. We investigate correlations between the physical properties of the clumps and masers using distances and luminosities drawn from the literature. Clumps hosting methanol masers are significantly more compact and have higher volume densities than the general population of clumps. We determine a minimum volume density threshold of n(H 2 )≥ 10 4 cm −3 for the efficient formation of intermediate-and highmass stars. We find 6.7 GHz methanol masers are associated with a distinct part of the evolutionary process (L bol /M fwhm ratios of between 10 0.6 and 10 2.2 ) and have well defined turning on and termination points. We estimate the lower limit for the mass of embedded objects to be ≥ 6 M and the statistical lifetime of the methanol maser stage to be ∼ 3.3×10 4 yrs. This suggests that methanol masers are indeed reliable tracers of high mass star formation, and indicates that the evolutionary period traced by this marker is relatively rapid.

Aims. Surveys of the Milky Way at various wavelengths have changed our view of star formation in our Galaxy considerably in recent years. In this paper we give an overview of the GLOSTAR survey, a new survey covering large parts (145 square degrees) of the northern Galactic plane using the Karl G. Jansky Very Large Array (JVLA) in the frequency range 4 − 8 GHz and the Effelsberg 100m telescope. This provides for the first time a radio survey covering all angular scales down to 1.5 arcsecond, similar to complementary near-IR and mid-IR galactic plane surveys. We outline the main goals of the survey and give a detailed description of the observations and the data reduction strategy. Methods. In our observations we covered the radio continuum in full polarization, as well as the 6.7 GHz methanol maser line, the 4.8 GHz formaldehyde line, and seven radio recombination lines. The observations were conducted in the most compact D configuration of the VLA and in the more extended B configuration. This yielded spatial resolutions of 18" and 1.5" for the two configurations, respectively. We also combined the D configuration images with the Effelsberg 100-m data to provide zero spacing information, and we jointly imaged the D-and B-configuration data for optimal sensitivity of the intermediate spatial ranges. Results. Here we show selected results for the first part of the survey, covering the range of 28 • < l < 36 • and |b| < 1 • , including the full low-resolution continuum image, examples of high-resolution images of selected sources, and the first results from the spectral line data.

Variability in Young Stellar Objects (YSOs) is one of their primary characteristics. Longterm, multi-filter, high-cadence monitoring of large YSO samples is the key to understand the partly unusual light-curves that many of these objects show. Here we introduce and present the first results of the HOYS-CAPS citizen science project which aims to perform such monitoring for nearby (d < 1 kpc) and young (age < 10 Myr) clusters and star forming regions, visible from the northern hemisphere, with small telescopes. We have identified and characterised 466 variable (413 confirmed young) stars in 8 young, nearby clusters. All sources vary by at least 0.2 mag in V, have been observed at least 15 times in V, R and I in the same night over a period of about 2 yrs and have a Stetson index of larger than 1. This is one of the largest samples of variable YSOs observed over such a time-span and cadence in multiple filters. About two thirds of our sample are classical T-Tauri stars, while the rest are objects with depleted or transition disks. Objects characterised as bursters show by far the highest variability. Dippers and objects whose variability is dominated by occultations from normal interstellar dust or dust with larger grains (or opaque material) have smaller amplitudes. We have established a hierarchical clustering algorithm based on the light-curve properties which allows the identification of the YSOs with the most unusual behaviour, and to group sources with similar properties. We discuss in detail the light-curves of the unusual objects V2492 Cyg, V350 Cep and 2MASS J21383981+5708470.

Context. Radio continuum surveys of the Galactic plane are an excellent way to identify different source populations such as planetary nebulae, H ii regions, and radio stars and characterize their statistical properties. The GLOSTAR survey will study the star formation in the Galactic plane between −2 • < < 85 • and |b| < 1 • with unprecedented sensitivity in both, flux density (∼40 µJy beam −1 ) and range of angular scales (∼1. 5 to the largest radio structures in the Galaxy). Aims. In this paper we present the first results obtained from a radio continuum map of a 16 square degree sized region of the Galactic plane centered on = 32 • and b = 0 • (28 • < < 36 • and |b| < 1 • ). This map has a resolution of 18 and a sensitivity of ∼60-150 µJy beam −1 . Methods. We present data acquired in 40 hours of observations with the VLA in D-configuration. Two 1 GHz wide sub-bands were observed simultaneously and they were centred at 4.7 and 6.9 GHz. These data were calibrated and imaged using the Obit software package. The source extraction has been performed using the BLOBCAT software package and verified through a combination of visual inspection and cross-matching with other radio and mid-infrared surveys. Results. The final catalog consists of 1575 discrete radio sources and 27 large scale structures (including W43 and W44). By crossmatching with other catalogs and calculating the spectral indices (S (ν) ∝ ν α ), we have classified 231 continuum sources as H ii regions, 37 as ionization fronts, and 46 as planetary nebulae. The longitude and latitude distribution and negative spectral indices are all consistent with the vast majority of the unclassified sources being extragalactic background sources. Conclusions. We present a catalog of 1575 radio continuum sources and discuss their physical properties, emission nature and relation with previously reported. These first GLOSTAR results have increased the number of reliable H ii regions in this part of the Galaxy by a factor of four.

Context. OH masers trace diverse physical processes, from the expanding envelopes around evolved stars to star-forming regions or supernovae remnants. Providing a survey of the ground-state OH maser transitions in the northern hemisphere inner Milky Way facilitates the study of a broad range of scientific topics. Aims. We want to identify the ground-state OH masers at ∼18 cm wavelength in the area covered by "The HI/OH/Recombination line survey of the Milky Way (THOR)". We will present a catalogue of all OH maser features and their possible associated environments. Methods. The THOR survey covers longitude and latitude ranges of 14. • 3 < l < 66. • 8 and b < ±1. • 25. All OH ground state lines 2 Π 3/2 (J=3/2) at 1612 (F=1-2), 1665 (F=1-1), 1667 (F=2-2) and 1720 MHz (F=2-1) have been observed, employing the Very Large Array (VLA) in its C configuration. The spatial resolution of the data varies between 12.5 and 19 , the spectral resolution is 1.5 km s −1 , and the rms sensitivity of the data is ∼10 mJy beam −1 per channel. Results. We identify 1585 individual maser spots (corresponding to single spectral features) distributed over 807 maser sites (regions of size ∼ 10 3 − 10 4 AU). Based on different criteria from spectral profiles to literature comparison, we try to associate the maser sites with astrophysical source types. Approximately 51% of the sites exhibit the double-horned 1612 MHz spectra typically emitted from the expanding shells of evolved stars. The separations of the two main velocity features of the expanding shells typically vary between 22 and 38 km s −1 . In addition to this, at least 20% of the maser sites are associated with star-forming regions. While the largest fraction of 1720 MHz maser spots (21 out of 53) is associated with supernova remnants, a significant fraction of the 1720 MHz maser spots (17) are also associated with star-forming regions. We present comparisons to the thermal 13 CO(1-0) emission as well as to other surveys of class II CH 3 OH and H 2 O maser emission. The catalogue attempts to present associations to astrophysical sources where available, and the full catalogue is available in electronic form.Conclusions. This OH maser catalogue presents a unique resource of stellar and interstellar masers in the northern hemisphere. It provides the basis for a diverse range of follow-up studies from envelopes around evolved stars to star-forming regions and Supernova remnants.