We analyzed the 3 mm wavelength spectral line survey of 408 clumps from the APEX telescope large area survey of the Galaxy, focusing on the methanol maser transitions. The main goals of this study are (1) to search for new methanol masers, (2) to statistically study the relationship between class I masers and shock tracers, (3) to study the properties between methanol masers and their host clumps, also as a function of their evolutionary stages and, (4) to better constrain the physical conditions using multiple co-spatial line pairs.

The dwarf galaxies in the Local Group (LG) reveal a surprising amount of spatial structuring. In particular, almost all non-satellite dwarfs belong to one of two planes that show a very pronounced symmetry. In order to determine if these structures in the LG are dynamically stable or, alternatively, if they only represent transient alignments, proper motion measurements of these galaxies are required. A viable method to derive proper motions is offered by VLBI studies of 22-GHz water (and 6.7-GHz methanol) maser lines in star-forming regions.

In 2016, in the framework of the Early Science Program of the Sardinia Radio Telescope (SRT), we have conducted an extensive observational campaign to map the entire optical body of all the LG dwarf galaxies that belong to the two planes, at C and K band, in a search for methanol and water maser emission.

Here, we outline the project and present its first results on 3 targets, NGC 6822, IC 1613, and WLM. While no luminous maser emission has been detected in these galaxies, a number of interesting weaker detections has been obtained, associated with particularly active star forming regions. In addition, we have produced deep radio continuum maps for these galaxies, aimed at investigating their star forming activity and providing an improved assessment of star formation rates in these galaxies.

In our attempt to investigate the basic active galactic nucleus (AGN) paradigm requiring a centrally located supermassive black hole (SMBH), a close to Keplerian accretion disk and a jet perpendicular to its plane, we have searched for radio continuum in galaxies with H2O megamasers in their disks. We observed 18 such galaxies with the Very Large Baseline Array in C band (5 GHz, ~2 mas resolution) and we detected 5 galaxies at 8 σ or higher levels. For those sources for which the maser data is available, the positions of masers and those of the 5 GHz radio continuum sources coincide within the uncertainties, and the radio continuum is perpendicular to the maser disk’s orientation within the position angle uncertainties.

The Central Molecular Zone (CMZ), the inner 450 pc of our Galaxy, is an exceptional region where the volume and column densities, gas temperatures, velocity dispersions, etc. are much higher than in the Galactic plane. It has been suggested that the formation of stars and clusters in this area is related to the orbital dynamics of the gas. The complex kinematic structure of the molecular gas was revealed by spectral line observations. However, these results are limited to the line-of-sight-velocities. To fully understand the motions of the gas within the CMZ, we have to know its location in 6D space (3D location + 3D motion). Recent orbital models have tried to explain the inflow of gas towards and its kinematics within this region. With parallax and proper motion measurements of masers in the CMZ we can discriminate among these models and constrain how our Galactic Center is fed with gas.

We present a case study of a single high-mass protostar associated with an infrared quiet massive clump selected from the ATLASGAL survey. The thermal dust emission reveals a single collapsing object associated with a prominent molecular outflow. We detect bright emission from a torsionally excited state transition of CH3OH offset from the protostar that is well explained by shocks at the transition from the infalling envelope onto an accretion disk.

We carried out a pivot experiment to select distant luminous late-type stars on the basis on their 2MASS and GLIMPSE photometry. Low-resolution infrared spectra enabled us to measure the equivalent widths (EWs) of their CO band-heads at 2.293 μm, and to confirm an extraordinarily high detection rate of red supergiants (RSGs), i.e. 61% (Messineo et al. (2016)).

We conducted infrared spectroscopic observations of bright stars in the direction of the molecular clouds W33 and GMC G23.3 − 0.3. We compared stellar spectro-photometric distances with parallactic distances to these regions, and we were able to assess the association of the detected massive stars with these molecular complexes. The spatial and temporal distributions of the detected stars enabled us to locate sources of ionizing radiation and to gather precise information on the star formation history of these clouds. The studied clouds present different distributions of massive stars.

The Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey aims to characterise the physical and chemical evolution of high-mass star-forming clumps. Exploiting the unique broad frequency range and on-the-fly mapping capabilities of the Australia Telescope National Facility Mopra 22 m single-dish telescope1, MALT90 has obtained 3′ × 3′ maps towards ~2 000 dense molecular clumps identified in the ATLASGAL 870 μm Galactic plane survey. The clumps were selected to host the early stages of high-mass star formation and to span the complete range in their evolutionary states (from prestellar, to protostellar, and on to $\mathrm{H\,{\scriptstyle {II}}}$ regions and photodissociation regions). Because MALT90 mapped 16 lines simultaneously with excellent spatial (38 arcsec) and spectral (0.11 km s−1) resolution, the data reveal a wealth of information about the clumps’ morphologies, chemistry, and kinematics. In this paper we outline the survey strategy, observing mode, data reduction procedure, and highlight some early science results. All MALT90 raw and processed data products are available to the community. With its unprecedented large sample of clumps, MALT90 is the largest survey of its type ever conducted and an excellent resource for identifying interesting candidates for high-resolution studies with ALMA.

We have used the Atacama Pathfinder Experiment (APEX) 12 m telescope at 218 GHz to observe molecular clouds simultaneously in the JKaKc = 303→202, 322→221, and 321→220 transitions of para-H2CO to determine kinetic temperatures of the dense gas in the central molecular zone of the Galaxy. Gas kinetic temperatures for individual molecular clouds range from 55 to 125 K or even higher. The molecular clouds at high temperatures may be heated by turbulent dissipation and/or cosmic-rays.

Using the IRAM 30 m telescope, we perform a molecular line survey of the 3 and 2 mm wavelength ranges towards 5 selected positions in the Galactic center region, sampling shocked regions, ultraviolet (UV) and X-ray pervaded regions, and positions with rich organic chemistry. These surveys have the potential to be used as chemical templates for different types of activity, such as photodissociated regions (PDRs), shocks and X-ray dominated regions (XDRs). Complementary, molecular surveys done towards extragalactic nuclei, that are also dominated by these physical activities, were carried by our group.

Attempting to distangle density and kinetic temperature of the star forming molecular gas in the central regions of galaxies, we have embarked on a project involving sensitive measurements of a variety of formaldehyde (H2CO) and ammonia (NH3) transitions. Preliminary results, based on observations from the Green Bank Telescope (GBT) and the Very Large Array (VLA) are summarized and an outline for the entire project is given.

The relationship between star formation rate (SFR) and the gas surface density (Σgas) is one of the most critical links between star formation and galaxy evolution. The observed SFR- Σgas relation, the “Schmidt-Kennicutt (S-K) law”, is tight when properties are averaged over kpc, but breaks down at the scale of giant molecular clouds (GMCs). To understand the physics governing the variations at GMC scales and the tight correlation at kpc scales, spatially and temporally resolved data covering a wide range of linear scale are needed. We have used the Spitzer surveys of the Large Magellanic Cloud and Magellanic Bridge to identify massive young stellar objects (YSOs), estimate “instantaneous” SFRs, and compare them to the S-K relation. These instantaneous SFRs are further compared to that estimated from integrated Hα and 24 μm luminosities to examine how SFRs vary on 10 Myr timescales. We have also used SINFONI near-IR integral field spectra of two Galactic mini-starbursts W31 and W43 to determine their underlying massive stellar content, estimate the SFRs, and compare to the S-K relation. To investigate evironmental effects on star formation, we have used complete YSO samples in the LMC and the Bridge to estimate global star formation efficiencies (SFE) in these two systems.

Due to their compactness, persistence and slow motion, Class II CH3OH masers are excellent targets for parallax and proper motion measurements for massive star-forming regions in the Galactic Disk. These measurements can be used to improve our understanding of the spiral structure and dynamics of the Milky Way. At the same time, Class II CH3OH masers can also be used to study gas kinematics close to the exciting star, tracing rotation, infall and/or outflow motions.

We present astrometric results of phase-referencing VLBI observations of 22 GHz H2O maser and 43 GHz SiO maser emission towards the red hypergiant NML Cyg using VLBA. We obtained an annual parallax of 0.62 ± 0.04 mas, corresponding to a distance of 1.61+0.13−0.11 kpc. With a VLA observation in its largest (A) configuration at 43 GHz, we barely resolve the radio photosphere of NML Cyg, and find a uniform-disk diameter of 44 ± 16 mas.

We report a trigonometric parallax measurement for the H2O masers around the protoplanetary nebula OH 231.8+4.2 carried out with the Very Long Baseline Array (VLBA). Based on astrometric monitoring for 1 year, we measured a parallax of 0.65 ± 0.01 mas, corresponding to a distance of 1.54 +0.02−0.01 kpc. The spatial distribution of H2O masers is consistent with that found in the previous studies. After removing the average proper motion of 1.4 mas yr−1, corresponding to 10 km s−1, the internal motions of the H2O maser spots indicate a bipolar outflow.

The massive star forming complex W33 contains several molecular clouds at different stages of star formation activity, ranging from quiescent to highly active clouds. Our trigonometric parallax observations of water masers in this complex, conducted with the VLBA at 22.2 GHz, show that all water masers have the same distance of 2.4 kpc, locating the W33 complex in the Sagittarius spiral arm.

We investigated the high-mass star-forming region G28.87+0.07 by means of maser kinematics, including H2O, CH3OH, and OH, and radio to infrared, continuum observations. All observational evidence suggests that these masers are associated with the same young star of 20-30 M⊙, still in the main accretion phase and surrounded by a rich stellar cluster.

As a part of the BeSSeL (Bar and Spiral Structure Legacy) survey, we report a trigonometric parallax for the massive star-forming region G348.70–1.04. Its distance is 3.38−0.27+0.33 kpc, indicating that it is in the Scutum-Centaurus arm. Its proper motion is −0.73 ± 0.04 mas yr−1 toward the east and −2.83 ± 0.50 mas yr−1 toward the north.

Submillimeter continuum emission traces high molecular column densities and, thus, dense cloud regions in which new stars are forming. Surveys of the Galactic plane in such emission have the potential of delivering an unbiased view of high-mass star formation throughout the Milky Way. Here we present the scope, current status and first results of ATLASGAL, an ongoing survey of the Galactic plane using the Large APEX Bolometer Camera (LABOCA) on the Atacama Pathfinder Experiment (APEX) telescope at the Chajnantor plateau in Chile. Aimed at mapping 360 square degrees at 870 μm, with a uniform sensitivity of 50 mJy/beam, this survey will provide the first unbiased sample of cold dusty clumps in the Galaxy at submillimeter wavelengths. These will be targets for molecular line follow-up observations and high resolution studies with ALMA and the EVLA.

We have measured the distance to the high-mass star-forming region G59.7+0.1 (IRAS 19410+2336) and W3OH. Their distances, 2.20 ± 0.11 kpc and 1.95 ± 0.04 kpc, respectively, were determined by triangulation using Very Long Baseline Array (VLBA) observations of 12.2 GHz methanol masers phase-referenced to compact extragalactic radio sources. In addition to the distances, we have also obtained their proper motions.