We report the results of a sensitive search for water maser emission in the Local Group Galaxy NGC 6822 with the Karl G. Jansky Very Large Array. The observations provide tentative single-epoch detections of four candidates, associated with two infrared-bright star formation regions (Hubble I/III and Hubble IV). The candidate maser detections are all offset from the velocity range where strong emission from HI neutral gas is observed toward NGC 6822, with the closest offset by 40 kms$^{-1}$. Our observations include the location of NL1K, a previous tentative water maser detection in NGC 6822. We do not detect any emission from this location with a sensitivity limit approximately a factor of 5 better than the original Sardina Radio Telescope observations.
We present Very Large Array observations of the 7_0-6_1 A^+ methanol maser transition at 44 GHz towards NGC 6334F, G8.67-0.36, and M17. These arcsecond resolution observations complete a previous, larger VLA survey of this maser transition in high-mass star-forming regions reported by Kurtz et al. We confirm the presence of 44 GHz methanol maser emission in all three sources, detecting eight distinct maser components in NGC 6334F, twelve components in G8.67-0.36 and one in M17.
We have used the Australia Telescope Compact Array (ATCA) to make new observations of the 36.2-GHz ($4_{-1}\rightarrow3_0$E) methanol transition toward NGC 4945 and NGC 253. These observations have revealed the presence of new maser components toward these galaxies, and have provided the first clear evidence for variability in extragalactic class~I methanol masers. Alongside the new observations of NGC 4945 and NGC 253, we present the results of recent 36.2-GHz methanol maser searches toward 12 galaxies, placing upper limits on the emission from the 36.2-GHz class~I transition and the 37.7-GHz…
The Extraordinary Maser Flaring Event in the Massive Protostellar System NGC6334I: Multi-Epoch Milliarcsecond Resolution Investigation of the 6.7-GHz Methanol Masers
We have used the Australia Telescope Compact Array (ATCA) to observe the 36.2-GHz class I methanol maser emission towards NGC253 and find that it is located at the interface between the nuclear ring and both ends of the galactic bar. This is thought to be the location of the inner Linblad resonance and we suggest that the maser emission in this region is likely due to large-scale cloud-cloud collisions. We have detected the first extragalactic 44.1-GHz class I methanol maser and find that it is associated with the 36.2-GHz maser emission. In contrast to the class I methanol masers found in Gal…
We present the first detection of extragalactic hydrogen recombination line maser emission in the H26alpha transition toward the inner 13.5 pc nuclear region of the starburst galaxy NGC 253 using ALMA data. In regions with complex continuum emission (dust, free-free and synchrotron) we propose to use the recombination line spectral index, $α_\mathrm{L}$ ($S_\mathrm{L}\cdot Δv \propto ν^{α_\mathrm{L}}$), between the H30alpha and the H26alpha lines to study the structure of ultra-compact HII regions and to identify maser emission ($α_\mathrm{L}> 2.1$) from ionized winds. The measured values of $…
We present the first interferometric observations at 18.5 GHz of IRS 1 in NGC 7538. These observations include images of the nonmetastable ^{14}NH_3 (9,6) masers with a synthesized beam of 2 arcseconds and images of the continuum emission with a synthesized beam of 150 milliarcseconds. Of the maser emission, the previously known feature near v_LSR = -60 km/s is spectrally resolved into at least two components and we observe several new maser emission features near v_LSR = -57 km/s. The new maser emission near -57 km/s lies 250 +/- 90 milliarcseconds northwest of the maser emission near -60 km/…
We report the detection of maser emission from the $J=4-3$ transition of HC$_3$N at 36.4~GHz towards the nearby starburst galaxy NGC253. This is the first detection of maser emission from this transition in either a Galactic or extragalactic source. The HC$_3$N maser emission has a brightness temperature in excess of 2500 K and is offset from the center of the galaxy by approximately 18 arcsec (300 pc), but close to a previously reported class~I methanol maser. Both the HC$_3$N and methanol masers appear to arise near the interface between the galactic bar and the central molecular zone, where…
We have investigated the central region of NGC 253 for the presence of 84.5-GHz ($5_{-1}\rightarrow4_0$E) methanol emission using the Australia Telescope Compact Array. We present the second detection of 84.5-GHz class~I methanol maser emission outside the Milky Way. This maser emission is offset from dynamical centre of NGC 253, in a region with previously detected emission from class~I maser transitions (36.2-GHz $4_{-1}\rightarrow3_0$E and 44.1-GHz $7_{0}\rightarrow6_1$A$^{+}$ methanol lines) . The emission features a narrow linewidth ($\sim$12 km s$^{-1}$) with a luminosity approximately 5…
We present the results of observations of 22GHz H2O maser emission in NGC 6240 and M51 made with the Karl G. Jansky Very Large Array. Two major H2O maser features and several minor features are detected toward the southern nucleus of NGC 6240. These features are redshifted by about 300 km/s from the galaxy's systemic velocity and remain unresolved at the synthesized beam size. A combination of our two-epoch observations and published data reveals an apparent correlation between the strength of the maser and the 22GHz radio continuum emission, implying that the maser excitation relates to the a…
The NGC 2024 FIR 6 region was observed in the water maser line at 22 GHz and the methanol class I maser lines at 44, 95, and 133 GHz. The water maser spectra displayed several velocity components and month-scale time variabilities. Most of the velocity components may be associated with FIR 6n, while one component was associated with FIR 4. A typical life time of the water-maser velocity-components is about 8 months. The components showed velocity fluctuations with a typical drift rate of about 0.01 km/s/day. The methanol class I masers were detected toward FIR 6. The methanol emission is confi…
We report the results of a Green Bank Telescope survey for water masers, ammonia (1,1) and (2,2), and the H66-alpha recombination line toward 506 luminous compact 24 micron-emitting regions in the Andromeda Galaxy (M31). We include the 206 sources observed in the Darling (2011) water maser survey for completeness. The survey was sensitive enough to detect any maser useful for ~10 microarcsecond/yr astrometry. No new water masers, ammonia lines, or H66-alpha recombination lines were detected individually or in spectral stacks reaching rms noise levels of ~3 mJy and ~0.2 mJy, respectively, in 3.…
22 GHz water and 6.7 GHz methanol masers are usually thought as signposts of early stages of high-mass star formation but little is known about their associations and the physical environments they occur in. The aim was to obtain accurate positions and morphologies of the water maser emission and relate them to the methanol maser emission recently mapped with Very Long Baseline Interferometry. A sample of 31 methanol maser sources was searched for 22 GHz water masers using the VLA and observed in the 6.7 GHz methanol maser line with the 32 m Torun dish simultaneously. Water maser clusters were…
Four Class I maser sources were detected at 44, 84, and 95 GHz toward chemically rich outflows in the regions of low-mass star formation NGC 1333I4A, NGC 1333I2A, HH25, and L1157. One more maser was found at 36 GHz toward a similar outflow, NGC 2023. Flux densities of the newly detected masers are no more than 18 Jy, being much lower than those of strong masers in regions of high-mass star formation. The brightness temperatures of the strongest peaks in NGC 1333I4A, HH25, and L1157 at 44 GHz are higher than 2000 K, whereas that of the peak in NGC 1333I2A is only 176 K. However, rotational diag…
This is the second paper in a series of catalogues of 22-GHz water maser observations towards the 6.7-GHz methanol masers from the Methanol Multibeam (MMB) Survey. In this paper we present our water maser observations made with the Australia Telescope Compact Array towards the masers from the MMB survey between l = 341$^{\circ}$ through the Galactic centre to l = 6$^{\circ}$. Of the 204 6.7-GHz methanol masers in this longitude range we found 101 to have associated water maser emission (~ 50 per cent). We found no difference in the 6.7-GHz methanol maser luminosities of those with and without …
We have conducted a sensitive water maser search with the ATCA towards 267 1.2-mm dust clumps presented in the literature. We combine our new observations with previous water maser observations to extend our sample to 294 1.2-mm dust clumps, towards which we detect 165 distinct water maser sites towards 128 1.2-mm dust clumps. Within the fields of our observations, we additionally find four water masers with no apparent associated 1.2-mm dust continuum emission. Our overall detection rate of 44 per cent appears to vary as a function of Galactic longitude. We find that there is an excellent cor…
We present the results of unbiased 22 GHz H2O water and 44 GHz class I CH3OH methanol maser surveys in the central 7x10 arcmin area of NGC 1333 and two additional mapping observations of a 22 GHz water maser in a ~3x3arcmin area of the IRAS4A region. In the 22 GHz water maser survey of NGC 1333 with sensitivity of sigma~0.3Jy, we confirmed masers toward H2O(B) in the region of HH 7-11 and IRAS4B. We also detected new water masers at ~20arcsec away in the western direction of IRAS4B or ~25arcsec away in the southern direction of IRAS4A. We could not however find young stellar objects or molecul…
We present a comparative multi-wavelength analysis of water maser-emitting regions and non-maser-emitting luminous 24 micron star-forming regions in the Andromeda Galaxy (M31) to identify the sites most likely to produce luminous water masers useful for astrometry and proper motion studies. Included in the analysis are Spitzer 24 micron photometry, Herschel 70 and 160 micron photometry, H$α$ emission, dust temperature, and star formation rate. We find significant differences between the maser-emitting and non-maser-emitting regions: water maser-emitting regions tend to be more IR-luminous and …
We present new maser emission from ^{14}NH_3 (9,6) in NGC 7538. Our observations include the known spectral features near v_LSR = -60 km/s and -57 km/s and several more features extending to -46 km/s. In three epochs of observation spanning two months we do not detect any variability in the ammonia masers, in contrast to the >10-fold variability observed in other ^{14}NH_3 (9,6) masers in the Galaxy over comparable timescales. We also present observations of water masers in all three epochs for which emission is observed over the velocity range -105 km/s < v_LSR < -4 km/s, including the highes…
The Survey of Water and Ammonia in Nearby galaxies (SWAN) studies atomic and molecular species across the nuclei of four star forming galaxies: NGC\,253, IC\,342, NGC\,6946, and NGC\,2146. As part of this survey, we present Karl G. Jansky Very Large Array (VLA) molecular line observations of three galaxies: IC\,342, NGC\,6946 and NGC\,2146. NGC\,253 is covered in a previous paper. These galaxies were chosen to span an order of magnitude in star formation rates and to select a variety of galaxy types. We target the metastable transitions of ammonia NH$_{3}$(1,1) to (5,5), the 22\,GHz water (H$_…
The 22.2 GHz water masers are often associated with the 6.7 GHz methanol masers but owing to the different excitation conditions they likely probe independent spatial and kinematic regions around the powering young massive star. We compared the emission of these two maser species on milliarcsecond scales to determine in which structures the masers arise and to test a disc-outflow scenario where the methanol emission arises in a circumstellar disc while the water emission comes from an outflow. We obtained high-angular and spectral resolution 22.2 GHz water maser observations of the two sources…
The ATCA has been used to measure positions with arcsecond accuracy for 379 masers at the 22-GHz transition of water. The principal observation targets were 202 OH masers of the variety associated with star formation regions (SFR)s in the Southern Galactic plane. At a second epoch, most of these targets were observed again, and new targets of methanol masers were added. Many of the water masers reported here are new discoveries. Variability in the masers is often acute, with very few features directly corresponding to those discovered two decades ago. Within our current observations, less than…
We present 321 GHz observations of five AGN from ALMA Cycle 0 archival data: NGC 5793, NGC 1068, NGC 1386, NGC 4945, and the Circinus galaxy. Submillimeter maser emission is detected for the first time towards NGC 4945, and we present a new analysis of the submillimeter maser system in Circinus. None of the other three galaxies show maser emission, though we have detected and imaged the continuum from every galaxy. Both NGC 4945 and Circinus are known to host strong ($\gtrsim 10$ Jy) 22 GHz megamaser emission, and VLBI observations have shown that the masers reside in the innermost $\sim 1$ pa…
We present further results of a search for extragalactic submillimeter H2O masers using the Atacama Large Millimeter/Submillimeter Array (ALMA). The detection of a 321 GHz H2O maser in the nearby Type 2 Seyfert galaxy, the Circinus galaxy, has previously been reported, and here the spectral analysis of four other galaxies is described. We have discovered H2O maser emission at 321 GHz toward the center of NGC 4945, a nearby Type 2 Seyfert. The maser emission shows Doppler-shifted velocity features with velocity ranges similar to those of the previously reported 22 GHz H2O masers, however the no…
An Australia Telescope Compact Array search for 22 GHz water masers towards 6.7 GHz class II methanol masers detected in the Methanol Multibeam (MMB) survey has resulted in the detection of extremely high velocity emission from one of the sources. The water maser emission associated with this young stellar object covers a velocity span of nearly 300 km/s. The highest velocity water maser emission is red-shifted from the systemic velocity by 250 km/s, which is a new record for high-mass star formation regions. The maser is associated with a very young late O, or early B star, which may still be…
We describe a method to identify inclined water maser disks orbiting massive black holes and to potentially use them to measure black hole masses. Due to the geometry of maser amplification pathways, the minority of water maser disks are observable: only those viewed nearly edge-on have been identified, suggesting that an order of magnitude additional maser disks exist. We suggest that inward-propagating masers will be gravitationally deflected by the central black hole, thereby scattering water maser emission out of the disk plane and enabling detection. The signature of an inclined water mas…
We present the first detection of para-ammonia masers in NGC 7538: multiple epochs of observation of the 14NH3 (J,K) = (10,8) and (9,8) lines. We detect both thermal absorption and nonthermal emission in the (10,8) and (9,8) transitions and the absence of a maser in the (11,8) transition. The (9,8) maser is observed to increase in intensity by 40% over six months. Using interferometric observations with a synthesized beam of 0.25", we find that the (10,8) and (9,8) masers originate at the same sky position near IRS1. With strong evidence that the (10,8) and (9,8) masers arise in the same volum…
We have used the Australia Telescope Compact Array (ATCA) to conduct further observations of the 36.2-GHz ($4_{-1}\rightarrow3_0$E) methanol transition towards the nearby active galaxy NGC 4945. These observations have led to a more accurate determination of the offset between the maser emission and the nucleus of NGC 4945 with a typical synthesised beam of $6^{\prime\prime} \times 4^{\prime\prime}$ ($108\times72$ pc). This corresponds to a factor of 4 improvement with respect to the major-axis of the beam. Other transitions of methanol and lines of other molecular species were obtained alongs…
We have searched for emission from the 36.2 GHz ($4_{-1} \rightarrow 3_0$E) methanol transition towards NGC 4945, using the Australia Telescope Compact Array. 36.2 GHz methanol emission was detected offset south-east from the Galactic nucleus. The methanol emission is narrow, with a linewidth <10 kms$^{-1}$, and a luminosity five orders of magnitude higher than Galactic class I masers from the same transition. These characteristics combined the with physical separation from the strong central thermal emission suggests that the methanol emission is a maser. This emission is a factor of $\sim90$…
We have analysed archival data taken with the Australia Telescope Compact Array (ATCA) during 2001--2003 and detected nine new interstellar and circumstellar water masers in the LMC. This takes the total number of star formation water masers in the LMC to 23, spread over 14 different star forming regions and three evolved stars. Three water maser sources (N105a/MC23, N113/MC24, N157a/MC74) have been detected in all the previous observations that targeted these sites, although all show significant variability on timescales of decades. The total number of independent water maser sources now know…
We present the results of second epoch ALMA observations of 321 GHz H$_2$O emission toward two nearby active galactic nuclei, NGC 4945 and the Circinus galaxy, together with Tidbinbilla 70-m monitoring of their 22 GHz H$_2$O masers. The two epoch ALMA observations show that the strengths of the 321 GHz emission are variable by a factor of at least a few, confirming a maser origin. In the second epoch, 321 GHz maser emission from NGC 4945 was not detected, while for the Circinus galaxy the flux density significantly increased and the velocity gradient and dispersion have been measured. With the…
The results of a maser survey toward ninety-nine protostars in the Orion molecular cloud complex are presented. The target sources are low-mass protostars identified from infrared observations. Single-dish observations were carried out in the water maser line at 22 GHz and the methanol class I maser lines at 44, 95, and 133 GHz. Most of the detected sources were mapped to determine the source positions. Five water maser sources were detected, and they are excited by HH 1-2 VLA 3, HH 1-2 VLA 1, L1641N MM1/3, NGC 2071 IRS 1/3, and an object in the OMC 3 region. The water masers showed significan…
We present Karl G Jansky Very Large Array molecular line observations of the nearby starburst galaxy NGC 253, from SWAN: "Survey of Water and Ammonia in Nearby galaxies". SWAN is a molecular line survey at centimeter wavelengths designed to reveal the physical conditions of star forming gas over a range of star forming galaxies. NGC 253 has been observed in four 1GHz bands from 21 to 36 GHz at 6" ($\sim100$pc) spatial and 3.5 km s$^{-1}$ spectral resolution. In total we detect 19 transitions from seven molecular and atomic species. We have targeted the metastable inversion transitions of ammon…
We report the detection of four water masers within the Small Magellanic Cloud (SMC); two discovered with the 70-m Tidbinbilla radio telescope, and two discovered with the Australia Telescope Compact Array (ATCA). Precise positions of all four masers have been derived from ATCA observations, and the characteristics of each water maser have been monitored over a period of several years. Sensitive observations towards two previously detected water masers reported in the literature failed to detect any emission. The detected water masers show evidence of higher levels of temporal variability than…
The Galactic Center contains large amounts of molecular and ionized gas as well as a plethora of energetic objects. Water masers are an extinction-insensitive probe for star formation and thus ideal for studies of star formation stages in this highly obscured region. With the Australia Telescope Compact Array, we observed 22 GHz water masers in the entire Central Molecular Zone with sub-parsec resolution as part of the large SWAG survey: ``Survey of Water and Ammonia in the Galactic Center''. We detect of order 600 22 GHz masers with isotropic luminosities down to ~10^-7 Lo. Masers with lumino…
We identify and phase a sample of 81 Cepheids in the maser-host galaxy NGC 4258 using the Large Binocular Telescope (LBT), and obtain calibrated mean magnitudes in up to 4 filters for a subset of 43 Cepheids using archival HST data. We employ 3 models to study the systematic effects of extinction, the assumed extinction law, and metallicity on the Cepheid distance to NGC 4258. We find a correction to the Cepheid colors consistent with a grayer extinction law in NGC 4258 compared to the Milky Way ($R_V =4.9$), although we believe this is indicative of other systematic effects. If we combine our…
A survey of young bipolar outflows in regions of low-to-intermediate-mass star formation has been carried out in two class I methanol maser transitions: 7_0-6_1A+ at 44 GHz and 4_{-1}-3_0E at 36 GHz. We detected narrow features towards NGC 1333I2A, NGC 1333I4A, HH25MMS, and L1157 at 44 GHz, and towards NGC 2023 at 36 GHz. Flux densities of the lines detected at 44 GHz are no higher than 11 Jy and the relevant source luminosities are about 10^{22} erg s{-1}, which is much lower than those of strong masers in high-mass star formation regions. No emission was found towards 39 outflows. All masers…
Context: Methanol masers of Class I (collisionally-pumped) and Class II (radiatively-pumped) have been studied in great detail in our Galaxy in a variety of astrophysical environments such as shocks and star-forming regions and are helpful to analyze the properties of the dense interstellar medium. However, the study of methanol masers in external galaxies is still in its infancy. Aims: Our main goal is to search for methanol masers in the central molecular zone (CMZ; inner 500 pc) of the nearby starburst galaxy NGC 253. Methods: Covering a frequency range between 84 and 373 GHz ($λ$ = 3.6 to …
A 22 GHz water maser survey was conducted towards 178 O-rich AGB stars with the aim of identifying maser emission associated with the Sagittarius stellar stream. In this survey, maser emissions were detected in 21 targets, of which 20 were new detections. We studied the Galactic distributions of H2O and SiO maser-traced AGBs towards the Sgr orbital plane, and found an elongated structure towards the (l, b)~(340, 40) direction. In order to verify its association with the Sagittarius tidal stream, we further studied the 3D motions of these sources, but found, kinematically, these maser-traced AG…
We test models of starburst driven outflows using observations of the 22.2 GHz H$_2$O and 36.2 GHz class I CH$_3$OH maser lines. We have observed the starburst galaxy NGC 253 using the Karl G. Jansky Very Large Array. We present evidence for entrainment of star-forming dense-molecular gas in the outflow of NGC 253. We also show that H$_2$O masers are associated with forming super star clusters and not with supernova remnants. We detect four new 36 GHz CH$_3$OH masers in the central kpc and show possible evidence for a star-formation origin of two class I CH$_3$OH masers. Such high resolution o…
We report on high spatial resolution water maser observations, using the Australia Telescope Compact Array, towards water maser sites previously identified in the H2O southern Galactic Plane Survey (HOPS). Of the 540 masers identified in the single-dish observations of Walsh et al. (2011), we detect emission in all but 31 fields. We report on 2790 spectral features (maser spots), with brightnesses ranging from 0.06 Jy to 576Jy and with velocities ranging from -238.5 to +300.5km/s. These spectral features are grouped into 631 maser sites. We have compared the positions of these sites to the lit…
Aim: The aim of this work is to search Seyfert 2 galaxy NGC 4945, a well-known 22 GHz water megamaser galaxy, for water (mega)maser emission at 183 GHz. Method: We used APEX SEPIA Band 5 to perform the observations. Results: We detected 183 GHz water maser emission towards NGC 4945 with a peak flux density of ~3 Jy near the galactic systemic velocity. The emission spans a velocity range of several hundred km/s. We estimate an isotropic luminosity of > 1000 Lsun, classifying the emission as a megamaser. A comparison of the 183 GHz spectrum with that observed at 22 GHz suggests that 183 GHz emis…
We present high angular resolution (FWHM_beam < 0.2") observations of the 23.1-GHz methanol (CH_3OH) transition toward the massive-star forming region NGC 7538 IRS 1. The two velocity components previously reported by Wilson et al. are resolved into distinct spatial features with brightness temperatures (T_B) greater than 10^4 K, proving their maser nature. Thus, NGC 7538 IRS 1 is the third region confirmed to show methanol maser emission at this frequency. The brighter 23.1-GHz spot coincides in position with a rare formaldehyde (H_2CO) maser, and marginally with a 22.2-GHz water (H_2O) maser…
We present observational results of water vapor maser emission with our high-sensitivity 22 GHz VLBI imaging of the Seyfert galaxy NGC 1068. In this galaxy, there are the following four nuclear radio sources; NE, C, S1, and S2. Among them, the S1 component has been identified as the nucleus while the C component has been considered as attributed to the radio jet. In our VLBI observation, we find the following two types of the water maser emission at the S1 component. One is the linearly aligned component that is considered as an edge-on disk with the inner radius of 0.62 pc. The dynamical mass…
A relationship between the water maser detection rate and large nuclear column densities in AGN has often been cited in the literature. Indeed, detailed studies of luminous water masers, typically associated with the nuclear activity, allow us to investigate the innermost regions of AGN, with an impact on the still debated Unified Model for this class of objects.We have recently entertained a search for maser emission in a well-defined sample of Compton-thick AGN aimed at investigating, on firm statistical bases, the aforementioned relationship. While the survey is still ongoing, and is matter…
We present the first astronomical detection of the 14NH3 (J,K) = (10,6) line: nonthermal emission at several velocities in the Galactic star-forming region NGC 7538. Using the VLA we have imaged the (10,6) and (9,6) ammonia masers at several positions within NGC 7538 IRS 1. The individual sources have angular sizes < 0.1 arcseconds corresponding to brightness temperatures T_B > 1E6 K. We apply the pumping model of Brown & Cragg, confirming the conjecture that multiple ortho-ammonia masers can occur with the same value of K. The positions and velocities of the (10,6) and (9,6) masers are modele…
We present first results of the H_2O Southern Galactic Plane Survey (HOPS), using the Mopra radiotelescope with a broad band backend and a beam size of about 2'. We have observed 100 square degrees of the southern Galactic plane at 12mm (19.5 to 27.5GHz), including spectral line emission from water masers, multiple metastable transitions of ammonia, cyanoacetylene, methanol and radio recombination lines. In this paper, we report on the characteristics of the survey and water maser emission. We find 540 water masers, of which 334 are new detections. The strongest maser is 3933Jy and the weakest…
Investigations of H$_2$O maser galaxies at X-ray energies reveal that most AGN associated with water masers are characterized by high levels of absorption. With the aim of finding new maser sources for possible interferometric follow-ups, we have searched for water maser emission in a well-defined sample of heavily absorbed AGN ($N_{\rm H} > 10^{23}$ cm$^{-2}$), including Compton-thick (CT) sources. All the galaxies in the sample were already searched for 22 GHz water maser emission in previous surveys. With the goal of providing a detection or a stringent upper limit on the H$_2$O luminosity,…
The Australia Telescope Compact Array has been used to search for 22-GHz water masers towards the 119 6.7-GHz methanol masers detected in the Methanol Multi-Beam survey between Galactic longitudes 6 and 20 degrees; we find water masers associated with 55 (~46 per cent). Methanol masers with associated water masers have a higher mean integrated luminosity than those without and there is a general trend for sources with more luminous 6.7-GHz methanol masers to be associated with more luminous water maser emission. We have inspected the GLIMPSE three colour images of the regions surrounding the m…
Water masers are good tracers of high-mass star-forming regions. Water maser VLBI observations provide a good probe to study high-mass star formation and the galactic structure. We plan to make a blind survey toward the northern Galactic plane in future years using 25m radio telescope of Xinjiang Astronomical Observatory. We will select some water maser sources discovered in the survey and make high resolution observations and study the gas kinematics close to the high-mass protostar.
Following an eruptive accretion event in NGC6334I-MM1, flares in the various maser species, including water masers, were triggered. We report the observed relative proper motion of the highly variable water masers associated with the massive star-forming region, NGC6334I. High velocity H$_2$O maser proper motions were detected in 5 maser clusters, CM2-W2 (bow-shock structure), MM1-W1, MM1-W3, UCHII-W1 and UCHII-W3. The overall average of the derived relative proper motion is 85 km s$^{-1}$. This mean proper motion is in agreement with the previous results from VLA multi-epoch observations. Our…
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…
