The aim of this study is to investigate the distribution and excitation of the methanol gas around Cep A and to describe the physical conditions of the region. In addition the large scale abundance distribution is determined in order to understand the morphology and kinematics of star forming regions in which methanol masers occur. The spatial distribution of the methanol is studied by mapping line emission, as well as the column density and excitation temperature, which are estimated using rotation diagrams. For a limited number of positions the parameters are checked with non-LTE models. Furthermore, the distribution of the methanol abundance is derived in comparison with archival dust continuum maps. Methanol is detected over a 0.3x0.15 pc area centred on the Cep A HW2 source, showing an outflow signature. Most of the gas can be characterized by a moderately warm rotation temperature (30-60K). At the central position two velocity components are detected with different excitation characteristics, the first related to the large-scale outflow. The second component, uniquely detected at the central location, is probably associated with the maser emission on much smaller scales of 2". Detailed analysis reveals that the highest densities and temperatures occur for these inner components. In the inner region the dust and gas are shown to have different physical parameters. Abundances of methanol in the range 10E-9 - 10E-7 are inferred, with the abundance peaking at the maser position. The geometry of the large-scale methanol is in accordance with previous determinations of the Cep A geometry, in particular those from methanol masers. The dynamical and chemical time-scales are consistent with the methanol originating from a single driving source associated with the HW2 object and the masers in its equatorial region.
We present a simultaneous single-dish survey of 22 GHz water maser and 44 GHz and 95 GHz class I methanol masers toward 77 6.7 GHz class II methanol maser sources, which were selected from the Arecibo methanol maser Galactic plane survey (AMGPS) catalog.Water maser emission is detected in 39 (51%) sources, of which 15 are new detections. Methanol maser emission at 44 GHz and 95 GHz is found in 25 (32%) and 19 (25%) sources, of which 21 and 13 sources are newly detected, respectively. We find 4 high-velocity (> 30 km/s) water maser sources, including 3 dominant blue- or redshifted outflows.The …
We present a continuing study of a sample 44 molecular outflows, observed in 13CO lines, closely associated with 6.7GHz methanol masers, hence called Methanol Maser Associated Outflows (MMAOs). We compare MMAO properties with those of outflows from other surveys in the literature. In general, MMAOs follow similar trends, but show a deficit in number at low masses and momenta, with a corresponding higher fraction at the high end of the distributions. A similar trend is seen for the dynamical timescales of MMAOs. We argue that the lack of relatively low mass and young flows in MMAOs is due to th…
We report the result of a systematic methanol observation toward IRAS 19312+1950. The properties of the SiO, H2O and OH masers of this object are consistent with those of mass-losing evolved stars, but some other properties are difficult to explain in the standard scheme of stellar evolution in its late stage. Interestingly, a tentative detection of radio methanol lines was suggested toward this object by a previous observation. To date, there are no confirmed detections of methanol emission towards evolved stars, so investigation of this possible detection is important to better understand th…
Ten new class II methanol masers from the 6.7-GHz Methanol Multibeam survey catalogues III and IV were selected for a monitoring programme at both 6.7 and 12.2 GHz with the 26m Hartebeesthoek Radio Astronomy Observatory (HartRAO) radio telescope for two years and nine months, from August 2012 to May 2015. In the sample, only masers associated with G339.986-0.425 were found to show periodic variability at both 6.7 and 12.2 GHz. The existence of periodic variation was tested with four independent methods. The analytical method gave the best estimation of the period, which was 246 $\pm$ 1 days. T…
Eight new class II methanol masers selected from the 6.7 GHz Methanol Multibeam survey catalogues I and II were monitored at 6.7 GHz with the 26m Hartebeesthoek Radio Astronomy Observatory (HartRAO) radio telescope for three years and seven months, from February 2011 to September 2014. The sources were also observed at 12.2 GHz and two were sufficiently bright to permit monitoring. One of the eight sources, namely G358.460-0.391, was found to show periodic variations at 6.7 GHz. The period was determined and tested for significance using the Lomb-Scargle, epoch-folding and Jurkevich methods, a…
Context: Class II methanol masers at 6.7 GHz originate close to high-mass young stellar objects (HMYSOs). Their high sensitivity to local condition variations makes them a useful marker of the activity of the emerging massive stars. Aims: We aim to closely examine the variability of the 6.7 GHz methanol masers in Cep A HW2 using the new and archival single-dish and high-resolution Very-Long-Baseline Interferometry (VLBI) datasets. Methods: We monitored 6.7 GHz methanol masers towards the target between 2009 and 2021 using the Torun 32 m radio telescope, and analysed nine datasets of VLBI obser…
The Purple Mountain Observatory 13.7 m radio telescope has been used to search for 95 GHz (8$_0$--7$_1$A$^+$) class I methanol masers towards 1020 Bolocam Galactic Plane Survey (BGPS) sources, leading to 213 detections. We have compared the line width of the methanol and HCO$^+$ thermal emission in all of the methanol detections and on that basis we find 205 of the 213 detections are very likely to be masers. This corresponds to an overall detection rate of 95 GHz methanol masers towards our BGPS sample of 20%. Of the 205 detected masers 144 (70%) are new discoveries. Combining our results wit…
In this paper, we present a database of class I methanol masers. The compiled information from the available literature provides an open and fast access to the data on class I methanol maser emission, including search, analysis and visualization of the extensive maser data set. There is information on individual maser components detected with single-dish observations and maser spots obtained from interferometric data. At the moment the database contains information from ~100 papers, i.e. ~7500 observations and ~650 sites of class I methanol masers. Analysis of the data collected in the databas…
We report a simultaneous 44 and 95 GHz class I methanol maser survey toward 144 sources from the 95 GHz class I methanol maser catalog. The observations were made with the three telescopes of the Korean very long baseline interferometry network operating in single-dish mode. The detection rates are 89% at 44 GHz and 77% at 95 GHz. There are 106 new discoveries at 44 GHz. Comparing the previous 95 GHz detections with new observations of the same transitions made using the Purple Mountain Observatory 13.7 m radio telescope shows no clear evidence of variability on a timescale of six years. Emiss…
We detail interferometric observations of 44GHz class I methanol masers detected by MALT-45 (a 7mm unbiased auto-correlated spectral-line Galactic-plane survey) using the Australia Telescope Compact Array. We detect 238 maser spots across 77 maser sites. Using high-resolution positions, we compare the class I CH$_3$OH masers to other star formation maser species, including CS (1-0), SiO $v=0$ and the H53$α$ radio-recombination line. Comparison between the cross- and auto-correlated data has allowed us to also identify quasi-thermal emission in the 44GHz class I methanol maser line. We find tha…
We present a study of the association between class I methanol masers and cold dust clumps from the ATLASGAL survey. It was found that almost 100% of class I methanol masers are associated with objects listed in the ATLASGAL compact source catalog. We find a statistically significant difference in the flux density, luminosity, number and column density and temperature distributions of ATLASGAL sources associated with 95/44 GHz methanol masers compared with those ATLASGAL sources devoid of 95 GHz methanol masers. The masers tend to arise in clumps with higher densities, luminosities and tempera…
We have performed a molecular line search toward the flaring 6.7-GHz masers G24.33+0.13 and G359.62-0.24 using the Australia Telescope Compact Array. We present spectra of the 6.7-GHz class~II methanol and 22.2-GHz water masers toward these sources and provide comparison with other recent flaring events these sources have experienced. We also detect the fourth example of a 23.4-GHz class~I methanol maser, and the eleventh example of a 4.8-GHz formaldehyde maser toward G24.33+0.13. Alongside these results, we observe the previously detected ammonia (3,3) emission and report upper limits on the …
Methanol and water vapour masers are signposts of early stages of high-mass star formation but it is generally thought that due to different excitation processes they probe distinct parts of stellar environments. Here we present observations of the intermediate-mass young stellar object G107.298+5.639, revealing for the first time that 34.4 d flares of the 6.7 GHz methanol maser emission alternate with flares of individual features of the 22 GHz water maser. High angular resolution data reveal that a few components of both maser species showing periodic behaviour coincide in position and veloc…
A 3D maser model has been used to perform an inverse problem on the light curves from three high-amplitude maser flares, selected on the basis of contemporaneous infra-red observations. Plots derived from the model recover the size of the maser cloud, and two parameters linked to saturation, from three observational properties of the light curve. Recovered sizes are consistent with independent interferometric measurements. Maser objects transition between weak and moderate saturation during a flare.
We report the detection of new 12.178, 12.229, 20.347, and 23.121 GHz methanol masers in the massive star-forming region G358.93-0.03, which are flaring on similarly short timescales (days) as the 6.668 GHz methanol masers also associated with this source. The brightest 12.178 GHz channel increased by a factor of over 700 in just 50 d. The masers found in the 12.229 and 20.347 GHz methanol transitions are the first ever reported and this is only the fourth object to exhibit associated 23.121 GHz methanol masers. The 12.178 GHz methanol maser emission appears to have a higher flux density than …
G111.256-0.770 is a high-mass young stellar object associated with a weak 6.7 GHz methanol maser showing strong variability. We present results of a multi-epoch monitoring program of the target, conducted with the Torun 32 m telescope for more than a decade. We found that the isotropic maser luminosity varied by a factor 16 on a timescale of 5-6 yr and individual features showed small amplitude short-lived (about 0.2 yr) bursts superimposed on higher amplitude slow (>5 yr) variations.
As a product of the maser monitoring program with the 26m telescope of the Hartebeesthoek Radio Astronomy Observatory (HartRAO), we present an unprecedented, contemporaneous flaring event of 10 maser transitions in hydroxyl, methanol, and water that began in 2015 January in the massive star-forming region NGC6334I in the velocity range -10 to -2 km/s. The 6.7 GHz methanol and 22.2 GHz water masers began flaring within 22 days of each other, while the 12.2 GHz methanol and 1665 MHz hydroxyl masers flared 80 and 113 days later respectively. The 1665 MHz, 6.7 GHz, and 22.2 GHz masers have all rem…
Context. Class II methanol masers at 6.7 and 12.2 GHz occur close to high-mass young stellar objects (HMYSOs). When they are observed simultaneously, such studies may contribute to refining the characterisation of local physical conditions. Aims. We aim to search for the 12.2 GHz methanol emission in 6.7 GHz methanol masers that might have gone undetected in previous surveys of northern sky HMYSOs, mainly due to their variability. Contemporaneous observations of both transitions are used to refine the flux density ratio and examine the physical parameters. Methods. We observed a sample of 153 …
We present the results of a monitoring campaign using the KAT-7 and HartRAO 26m telescopes, of hydroxyl, methanol and water vapour masers associated with the high-mass star forming region G9.62+0.20E. Periodic flaring of the main line hydroxyl masers were found, similar to that seen in the 6.7 and 12.2 GHz methanol masers. The 1667 MHz flares are characterized by a rapid decrease in flux density which is coincident with the start of the 12.2 GHz methanol maser flare. The decrease in the OH maser flux density is followed by a slow increase till a maximum is reached after which the maser decays …
We present the most complete to date interferometric study of the centimeter wavelength methanol masers detected in G358.93-0.03 at the burst and post-burst epochs. A unique, NIR/(sub)mm-dark and FIR-loud MYSO accretion burst was recently discovered in G358.93-0.03. The event was accompanied by flares of an unprecedented number of rare methanol maser transitions. The first images of three of the newly-discovered methanol masers at 6.18, 12.23, and 20.97 GHz are presented in this work. The spatial structure evolution of the methanol masers at 6.67, 12.18, and 23.12 GHz is studied at two epochs.…
The Cygnus X complex is covered by the Global View of Star Formation in the Milky Way (GLOSTAR) survey, an unbiased radio-wavelength Galactic plane survey, in 4--8 GHz continuum radiation and several spectral lines. The GLOSTAR survey observed the 6.7~GHz transition of methanol (CH$_3$OH), an exclusive tracer of high-mass young stellar objects. Using the Very Large Array in both the B and D configurations, we observed an area in Cygnus~X of $7^{\rm o}\times3^{\rm o}$ in size and simultaneously covered the methanol line and the continuum, allowing cross-registration. We detected thirteen source…
We present observations of massive star-forming regions selected from the IRAS Point Source Catalog. The observations were made with the Very Large Array and the Large Millimeter Telescope to search for Class I methanol masers. We made interferometric observations of 125 massive star-forming regions in the 44 GHz methanol maser transition; 53 of the 125 fields showed emission. The data allow us to demonstrate associations, at arcsecond precision, of the Class I maser emission with outflows, HII regions and shocks traced by 4.5 $μ$m emission. We made single-dish observations toward 38 of 53 reg…
We report the first sub-arcsecond VLA imaging of 6 GHz continuum, methanol maser, and excited-state hydroxyl maser emission toward the massive protostellar cluster NGC6334I following the recent 2015 outburst in (sub)millimeter continuum toward MM1, the strongest (sub)millimeter source in the protocluster. In addition to detections toward the previously known 6.7 GHz Class II methanol maser sites in the hot core MM2 and the UCHII region MM3 (NGC6334F), we find new maser features toward several components of MM1, along with weaker features $\sim1''$ north, west, and southwest of MM1, and toward …
(Abridged) Astronomical masers have been effective tools to study magnetic fields for many years. In particular, methanol can be used to probe different parts of protostars such as accretion discs and outflows, since it produces one of the strongest and the most commonly observed masers in massive star-forming regions. We investigate the polarization properties of selected methanol maser transitions in light of newly calculated methanol Landé g-factors and considering hyperfine components. We compare our results with previous observations and we evaluate the effect of preferred hyperfine pumpi…
Single point observations are presented in NH3 (1,1) and (2,2) inversion transitions using the Effelsberg 100 m telescope for a sample of 100 6.7 GHz methanol masers and mapping observations in the 12CO and 13CO (1-0) transitions using the PMO Delingha 13.7 m telescope for 82 sample sources with detected ammonia. A further 62 sources were selected for either 12CO or 13CO line outflow identification, producing 45 outflow candidates, 29 using 12CO and 16 using 13CO data. Twenty-two of the outflow candidates were newly identified, and 23 had trigonometric parallax distances. Physical properties w…
We present results from calculations of the physical conditions necessary for the occurrence of 36.169 ($4_{-1}-3_{0}\, E$), 44.070 ($7_{0}-6_{1}\,A^+$), 84.521 ($5_{-1}-4_{0}\,E$), and 95.169 ($8_{0}-7_{1}\,A^+$) GHz methanol (CH$_3$OH) maser emission lines near supernova remnants (SNRs), using the MOLPOP-CEP program. The calculations show that given a sufficient methanol abundance, methanol maser emission arises over a wide range of densities and temperatures, with optimal conditions at $n\sim 10^4-10^6$ cm$^{-3}$ and $T>60$ K. The 36~GHz and 44~GHz transitions display more significant maser…
We investigate the kinematics of high mass protostellar objects within the high mass star forming region IRAS 19410+2336. We performed high angular resolution observations of 6.7-GHz methanol and 22 GHz water masers using the MERLIN (Multi-Element Radio Linked Interferometer Network) and e-MERLIN interferometers. The 6.7-GHz methanol maser emission line was detected within the $\sim$ 16--27 km s$^{-1}$ velocity range with a peak flux density $\sim$50 Jy. The maser spots are spread over $\sim$1.3 arcsec on the sky, corresponding to $\sim$2800 au at a distance of 2.16 kpc. These are the first as…
The Methanol MultiBeam survey (MMB) provides the most complete sample of Galactic massive young stellar objects (MYSOs) hosting 6.7GHz class II methanol masers. We characterise the properties of these maser sources using dust emission detected by the Herschel Infrared Galactic Plane Survey (Hi-GAL) to assess their evolutionary state. Associating 731 (73%) of MMB sources with compact emission at four Hi-GAL wavelengths, we derive clump properties and define the requirements of a MYSO to host a 6.7GHz maser. The median far-infrared (FIR) mass and luminosity are 630M$_{\odot}$ and 2500L$_{\odot}$…
