Maser Sites Research Articles

MAGMO: coherent magnetic fields in the star-forming regions of the Carina-Sagittarius spiral arm tangent

We present the pilot results of the `MAGMO' project, targeted observations of ground-state hydroxyl masers towards sites of 6.7-GHz methanol maser emission in the Carina-Sagittarius spiral arm tangent, Galactic longitudes 280 degrees to 295 degrees. The `MAGMO' project aims to determine if Galactic magnetic fields can be traced with Zeeman splitting of masers associated with star formation. Pilot observations of 23 sites of methanol maser emission were made, with the detection of ground-state hydroxyl masers towards 11 of these and six additional offset sites. Of these 17 sites, nine are new detections of sites of 1665-MHz maser emission, three of them accompanied by 1667-MHz emission. More than 70% of the maser features have significant circular polarization, whilst only ~10% have significant linear polarization (although some features with up to 100% linear polarization are found). We find 11 Zeeman pairs across six sites of high-mass star formation with implied magnetic field strengths between -1.5 mG and +3.8 mG and a median field strength of +1.6 mG. Our measurements of Zeeman splitting imply that a coherent field orientation is experienced by the maser sites across a distance of 5.3+/-2.0 kpc within the Carina-Sagittarius spiral arm tangent.

An evolutionary sequence for high-mass star formation

AbstractDetermining an evolutionary clock for high-mass star formation is an important step towards realizing a unified theory of star formation, as it will enable qualitative studies of the associated high-mass stars to be executed. Our recent studies have shown that masers have great potential to accurately trace the evolution of these regions. We have investigated the relative evolutionary phases associated with the presence of combinations of water, methanol and hydroxyl masers. Comparison between the characteristics of coincident sources has revealed strong evidence for an evolutionary sequence for the different maser species, a result that we now aim to corroborate through comparisons with chemical clocks.Using our new, large samples of methanol masers at 6.7 GHz (MMB survey; Green et al. (2009)) and 12.2 GHz (Breen et al. 2012), 22 GHz water masers (Breen & Ellingsen 2012), OH masers together with complementary data, we find strong evidence that it is not only the presence or absence of the different maser species that indicates the evolutionary stage of the associated high-mass star formation region (see e.g. Breen et al. (2010)), but that the properties of those masers can give even finer evolutionary details. Most notably, the intensity and velocity range of detected maser emission increases as the star forming region evolves (Breen et al. 2011).Subsequent work we have undertaken (Ellingsen et al. 2011) has shown that the presence of rare 37.7 GHz methanol masers may signal the end of the methanol maser phase. They show that 37.7 GHz methanol masers are associated only with the most luminous 6.7 and 12.2 GHz methanol masers, which combined with the rarity of these objects is consistent with them being a short lived phase towards the end of the 6.7 GHz methanol maser lifetime.An independent confirmation of our maser evolutionary timeline can be gained through comparisons with chemical clocks. MALT90 is a legacy survey of 1000s of dense star forming cores at 90GHz, simultaneously observing 16 molecular lines with the Mopra radio telescope (see e.g. Foster et al. 2011). It provides the perfect dataset to test the maser evolutionary timeline due to the targeted lines and the fact that at least one-quarter of the MALT90 sources correspond to maser sites, providing a large enough sample for meaningful analysis. From our preliminary analysis, we find that star formation regions showing similar maser properties also show similar thermal line properties; as would be expected if our evolutionary scenario were accurate.

44-GHz class I methanol maser survey towards 6.7-GHz class II methanol masers

AbstractThe Class II 6.7-GHz methanol maser is a tracer of high mass young stellar objects. We present results of a 44-GHz class I methanol maser and 22-GHz water maser survey using the KVN (Korean VLBI Network) 21-m single dish radio telescopes towards 284 6.7-GHz maser sites. Class I methanol maser and water maser emission is detected towards 116 (41%) and 136 (48%) sources, respectively. About 50 sources have a peak flux density higher than 10 Jy at 44-GHz. They are candidates for VLBI studies using the KVN.

Intermittent maser flare around the high-mass young stellar object G353.273+0.641

AbstractThe water maser site associated with G353.273+0.641 is classified as a dominant blueshifted H2O maser, which shows an extremely wide velocity range (± 100 km s−1) with almost all flux concentrated in the highly blueshifted emission. The previous study has proposed that this peculiar H2O maser site is excited by a pole-on jet from high mass protostellar object. We report on the monitoring of 22-GHz H2O maser emission from G353.273+0.641 with the VLBI Exploration of Radio Astrometry (VERA) and the Tomakamai 11-m radio telescope. Our VLBI imaging has shown that all maser features are distributed within a very small area of 200 × 200 au2, in spite of the wide velocity range (> 100 km s−1). The light curve obtained by weekly single-dish monitoring shows notably intermittent variation. We have detected three maser flares during three years. Frequent VLBI monitoring has revealed that these flare activities have been accompanied by a significant change of the maser alignments. We have also detected synchronized linear acceleration (−5 km s−1yr−1) of two isolated velocity components, suggesting a lower-limit momentum rate of 10−3 M⊙ km s−1yr−1 for the maser acceleration. All our results support the previously proposed pole-on jet scenario, and finally, a radio jet itself has been detected in our follow-up ATCA observation. If highly intermittent maser flares directly reflect episodic jet-launchings, G353.273+0.641 and similar dominant blueshifted water maser sources can be suitable targets for a time-resolved study of high mass protostellar jet.

Constraining the properties of 1.2-mm dust clumps that contain luminous water masers

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 correspondence between the locations of the detected water masers with the peak of the target 1.2-mm dust clump sources. As expected from previous similar studies, the water masers are chiefly detected towards the bigger, brighter and more massive 1.2-mm dust clumps. We find further evidence that the water masers tend to increase in flux density (and therefore luminosity), as well as velocity range, as the sources evolve. We also show that the current sample of water maser sources suffer less from evolutionary biases than previous targeted searches. A higher fraction of dust clump sources in our sample are only associated with water masers (41) than only associated with methanol masers (13). This suggests that water masers can be present at an even earlier evolutionary stage than 6.7-GHz methanol masers. Comparison of the water maser detection rates associated with different combinations of methanol maser and radio continuum, as well as those with neither tracer, shows that the highest detection rate is towards those sources which also exhibit methanol maser emission. We have tested a previously hypothesised model for water maser presence towards 1.2-mm dust clumps. We suggest refinements and future work which will further constrain the nature of the driving sources associated with water masers.

The H2O Southern Galactic Plane Survey (HOPS) - I. Techniques and H2O maser data

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 is 0.7Jy, with 62 masers over 100Jy. In 14 maser sites, the spread in velocity of the water maser emission exceeds 100km/s. In one region, the water maser velocities are separated by 351.3km/s. The rms noise levels are typically between 1-2Jy, with 95% of the survey under 2Jy. We estimate completeness limits of 98% at around 8.4Jy and 50% at around 5.5Jy. We estimate that there are between 800 and 1500 water masers in the Galaxy that are detectable in a survey with similar completeness limits to HOPS. We report possible masers in NH_3 (11,9) and (8,6) emission towards G19.61-0.23 and in the NH_3 (3,3) line towards G23.33-0.30.

Maser maps and magnetic field of OH 337.705−0.053

New high resolution studies of the Galactic maser site 337.705−0.053 reveal its magnetic field and velocity morphology. The long baseline array of the Australia Telescope National Facility provided simultaneous observations of both the 1665- and 1667-MHz OH transitions which yielded a sequence of maps at velocity spacing 0.09 km s−1, in both senses of circular polarization, with tenth-arcsec spatial resolution. 38 small diameter maser spots were detected, spread over an ellipse with largest dimension of 1.5 arcsec. Pairs of spots with the same position, but with right and left circular polarization at different frequency, reveal Zeeman splitting. Five pairs at 1665 MHz and four at 1667 MHz are seen; at one position, pairs at both transitions indicate a comparable magnetic field and similar (central) velocity. All estimates of magnetic field are in the same sense, with a median value of −2.5 mG (pointing towards the earth), confirming an interpretation from single-dish observations. The morphology and kinematics have been compared with that of maser emission from the excited state of OH at 6035 MHz, with methanol at 6668 MHz and 12 GHz, and with water at 22 GHz. All species are intermingled, and associated with an ultracompact H ii region. The site most likely lies near the tangent point of the Galactic 3-kpc ring, at a distance of 7.9 kpc. The maser spot distribution over 1.5 arcsec then corresponds to a diameter of 60 mpc, amongst the largest known, and likely to be approaching the end of the maser emitting phase. 337.705−0.053 adds to the maser sites studied in sufficient detail to explore ordered patterns in the global Galactic magnetic field.

Blueshifted outflow from 24.329+0.145

New studies of an hydroxyl (OH) maser site that has puzzled astronomers for more than 40 yr demonstrate that its emission arises in a unique strong blueshifted outflow. Measurements with the Australia Telescope Compact Array (ATCA) locate this enigmatic OH 1667-MHz maser at 24.329+0.145 (Galactic coordinates). This is coincident (to arcsecond accuracy) with maser emission at the 6668-MHz transition of methanol and a newly discovered maser at the 22-GHz transition of water. The methanol maser establishes the site as one of high-mass star formation, and the small spread of methanol features about a median velocity of +113 km s−1 defines its systemic velocity. The water maser shows a combination of some emission arising near this systemic velocity, and the remainder arising in the blueshifted outflow. The 1667-MHz OH emission extends over more than 20 km s−1, and our demonstrated association with the methanol maser reveals that this is offset from the systemic velocity by as much as 50 km s−1. The implied energetic blueshifted outflow is unprecedented in OH masers of this class. Our spectral studies using the ATCA, with a new high-resolution spectrometer, achieve full polarization observations of the 1665- and 1667-MHz OH ground-state transitions. The dominance of 1667-MHz emission, with no detection at 1665 MHz, suggests unusual physical properties in the ouflow region. Likewise, the prevalence of linear polarization may be a consequence of emission arising in a fast-moving outflow, with perhaps a link between linear polarization orientation and outflow orientation. We also present new observations of maser sites 24.494−0.039 and 24.790+0.083. These close neighbours of 24.329+0.145, with methanol maser emission at a similar systemic velocity, are also accompanied by masers of water and OH, but have no unusual maser properties. The velocity and Galactic longitude of all three sites, and of the H ii complex W42, correspond to an especially interesting Galactic location near the tangent point of the 3-kpc arm (expanding ring), at a distance of 7.7 kpc.

A STRING OF RADIO EMISSION ASSOCIATED WITH IRAS 16562–3959: A COLLIMATED JET EMANATING FROM A LUMINOUS MASSIVE YOUNG STELLAR OBJECT

We report the discovery made using the Australia Telescope Compact Array of a remarkable string of radio emission towards IRAS 16562-3959, a luminous infrared source with a bolometric luminosity of $7.0\times10^4$ \Lsun. The radio emission arises from a compact, bright central component, two inner lobes, which are separated by about 7\arcsec\ and symmetrically offset from the central source, and two outer lobes which are separated by about 45\arcsec. The emission from the central object has a spectral index between 1.4 and 8.6 GHz of $0.85\pm0.15$, consistent with free-free emission from a thermal jet. The radio emission from the lobes have spectral indices in the range characteristic of thermal emission. We suggest that the emission from the lobes arises in shocks resulting from the interaction of a collimated wind with the surrounding medium. The radio string is located within a massive dense molecular core, and is associated with extended green emission (Spitzer 3-color), Herbig-Haro type emission (2MASS K$_s$-band) and OH maser sites -- all phenomena readily observed towards sites of massive star formation. We conclude that the massive core hosts a high-mass star in an early stage of evolution in which it is undergoing the ejection of a powerful collimated stellar wind, showing that jets found in the formation of low-mass stars are also produced in high-mass stars.

A water maser survey towards the Galactic Centre

We have used the Australia Telescope Compact Array to survey the Galactic Centre for the 22-GHz transition of water. The survey provides an unbiased search for water masers within a 0.5 deg2 region about the Centre, and the small synthesized beam directly yields positions to arcsecond accuracy. The detected sources were re-observed 4 months later and showed considerable changes in their spectra, with two sources found in the follow-up that were not seen in the original survey, yielding a total of 27 maser detections. Comparison with methanol and OH surveys shows that, at current sensitivity levels, water masers greatly outnumber the other species. 12 of our maser detections had previously been reported, discovered during searches towards interesting targets in the survey area. The majority of our sources are quite weak, consistent with excitation by young massive stars mostly near the Galactic Centre. Our spectra reveal high-velocity outflows at one-quarter of the water maser sites, a statistic similar to sites in the remainder of the Galaxy.

GLOBAL VERY LONG BASELINE INTERFEROMETRY OBSERVATIONS OF THE 6.0 GHz HYDROXYL MASERS IN ONSALA 1

We present global very long baseline interferometry observations of the first excited-state hydroxyl (OH) masers in the massive star-forming region Onsala 1 (ON 1). The 29 masers detected are nearly all from the 6035 MHz transition and nearly all are identifiable as Zeeman pair components. The 6030 and 6035 MHz masers are coincident with previously published positions of ground-state masers to within a few milliarcseconds, and the magnetic fields deduced from Zeeman splitting are comparable. The 6.0 GHz masers in ON 1 are always found in close spatial association with 1665 MHz OH masers, in contrast to the situation in the massive star-forming region W3(OH), suggesting that extreme high density OH maser sites (excited-state masers with no accompanying ground-state maser, as seen in W3(OH)) are absent from ON 1. The large magnetic field strength among the northern, blueshifted masers is confirmed. The northern masers may trace an outflow or be associated with an exciting source separate from the other masers, or the relative velocities of the northern and southern masers may be indicative of expansion and rotation. High angular resolution observations of nonmasing material will be required in order to understand the complex maser distribution in ON 1.

The 6-GHz methanol multibeam maser catalogue - I. Galactic Centre region, longitudes 345° to 6°

We have conducted a Galactic plane survey of methanol masers at 6668 MHz using a 7-beam receiver on the Parkes telescope. Here we present results from the first part, which provides sensitive unbiased coverage of a large region around the Galactic Centre. Details are given for 183 methanol maser sites in the longitude range 345$^{\circ}$ through the Galactic Centre to 6$^{\circ}$. Within 6$^{\circ}$ of the Centre, we found 88 maser sites, of which more than half (48) are new discoveries. The masers are confined to a narrow Galactic latitude range, indicative of many sources at the Galactic Centre distance and beyond, and confined to a thin disk population; there is no high latitude population that might be ascribed to the Galactic Bulge. Within 2$^{\circ}$ of the Galactic Centre the maser velocities all lie between -60 and +77 \kms, a range much smaller than the 540 \kms range observed in CO. Elsewhere, the maser with highest positive velocity (+107 \kms) occurs, surprisingly, near longitude 355$^{\circ}$ and is probably attributable to the Galactic bar. The maser with the most negative velocity (-127 \kms) is near longitude 346$^{\circ}$, within the longitude-velocity locus of the near side of the `3-kpc arm'. It has the most extreme velocity of a clear population of masers associated with the near and far sides of the 3-kpc arm. Closer to the Galactic Centre the maser space density is generally low, except within 0.25 kpc of the Centre itself, the `Galactic Centre Zone', where it is 50 times higher, which is hinted at by the longitude distribution, and confirmed by the unusual velocities.

Water masers accompanying OH and methanol masers in star formation regions

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 a year apart, spectra are often dissimilar, but positions at the later epoch, even when measured for slightly different features, mostly correspond to the detected maser site measured earlier, to within the typical extent of the whole site, of a few arcseconds. The precise water positions show that approximately 79% (160 of 202) of the OH maser sites show coincident water maser emission, the best estimate yet obtained for this statistic; however, there are many instances where additional water sites are present offset from the OH target, and consequently less than half of the water masers coincide with a 1665-MHz ground-state OH maser counterpart. We explore the differences between the velocities of peak emission from the three species (OH, methanol and water), and quantify the typically larger deviations shown by water maser peaks from systemic velocities. Clusters of two or three distinct but nearby sites, each showing one or several of the principal molecular masing transitions, are found to be common. In combination with an investigation of correlations with IR sources from the GLIMPSE catalogue, these comparative studies allow further progress in the use of the maser properties to assign relative evolutionary stages in star formation to individual sites.

LBA observations of the maser cluster OH 330.953−0.182

The maser spot distribution of OH 330.953-0.182 provides a valuable probe of its massive star-forming host. We present observations with the Long Baseline Array of the Australia Telescope National Facility, of both the 1665- and 1667-MHz hydroxyl ground-state transitions, yielding a series of maps in both right- and left-hand circular polarization at velocity spacing 0.09 km s -1 with 0.1 arcsec spatial resolution. A total of 53 maser spots are spread over a remarkably large region exceeding 6 arcsec diameter. At the minimum distance estimate of 5.6 kpc, 6 arcsec corresponds to 163 mpc, much larger than the extents of previously mapped individual sites, which rarely exceed 40 mpc. Seven locations show Zeeman pairs, one of them at both 1665 and 1667 MHz corroborating the same magnetic field estimate. All measured magnetic fields are towards us (negative), and range from -3.7 to -5.8 mG. Comparisons of the morphology and kinematics of the 1665- and 1667-MHz maser spots have been made with those of the OH 1720-MHz transition, the excited state of OH at 6035 MHz, methanol at 6668 MHz, water at 22 GHz and with extensive H II emission, all of which contribute to a better understanding of the region. We interpret the overall complexity of the region as evidence for several distinct sites of excitation, similar to the remarkable W51 complex, and in contrast to the simple morphologies of previously studied single maser sites such as OH 300.969+1.147 and W3(OH).

Maser maps and magnetic field of OH 300.969+1.147

The southern maser site OH 300.969+1.147 has been studied using the Long Baseline Array of the Australia Telescope National Facility. The 1665- and 1667-MHz hydroxyl ground-state transitions were observed simultaneously. A series of maps with tenth-arcsec spatial resolution, at velocity spacing 0.09 km/s, and in both senses of circular polarization, reveal 59 small diameter maser spots. The spots are scattered over 2-arcsec, coincident with a strong ultracompact HII region, at a distance of 4.3 kpc. 17 Zeeman pairs of oppositely polarized spots were found, all yielding magnetic field estimates towards us (negative), ranging from -1.1 to -4.7 mG, with a median value of -3.5 mG. Excited state masers of OH at 6035 MHz and 6030 MHz at this site also display Zeeman pairs revealing a magnetic field of -5.0 mG. Weak methanol maser emission is intermingled with the OH masers, but there is no detectable closely related water maser. The consistent magnetic field direction found within this site is a striking feature of several other maser sites associated with strong HII regions studied in comparable detail. We interpret the site as a mature region nearing the end of the brief evolutionary stage that can support maser emission.

Precise Positions of Methanol Masers

AbstractThe Australia Telescope Compact Array (ATCA) has been used to determine positions for many southern methanol maser sites, with accuracy better than 1 arcsec. The results are presented here as a catalogue of more than 350 distinct sites, some of them new discoveries, and many others with positional precision 10-times better than existing published values. Clusters of 2 or 3 sites are occasionally found to account for single previously listed sources. This in turn reveals that the velocity range for each individual site is sometimes smaller than that of the originally tabulated (blended) source. Only a handful of examples then remain with a velocity range of more than 16 km s−1 at a single compact (less than 2 arcsec) site. The precise methanol positions now allow apparent coincidences with OH masers to be confidently accepted or rejected; this has led to the important conclusion that, where a 1665-MHz OH maser lies in a massive star formation region, at more than 80 percent of the OH sites there is a precisely coincident methanol maser. The methanol precision achieved here will also allow clear comparisons with likely associated IR sources when the next generation of far-IR surveys produce precise positions.

SiO maser emission in Miras

We describe a combined dynamic atmosphere and maser propagation model of SiO maser emission in Mira variables. This model rectifies many of the defects of an earlier model of this type, particularly in relation to the infra-red (IR) radiation field generated by dust and various wavelength-dependent, optically thick layers. Modelled masers form in rings with radii consistent with those found in VLBI observations and with earlier models. This agreement requires the adoption of a radio photosphere of radius approximately twice that of the stellar photosphere, in agreement with observations. A radio photosphere of this size renders invisible certain maser sites with high amplification at low radii, and conceals high-velocity shocks, which are absent in radio continuum observations. The SiO masers are brightest at an optical phase of 0.1 to 0.25, which is consistent with observed phase-lags. Dust can have both mild and profound effects on the maser emission. Maser rings, a shock and the optically thick layer in the SiO pumping band at 8.13µmappear to be closely associated in three out of four phase samples.

LBA observations of OH masers in the star-forming region OH 330.953–0.182

AbstractOH masers are sensitive probes of the kinematics, physical conditions, and magnetic fields in star-forming regions. The maser site OH 330.953-0.182 has been studied using the Long Baseline Array of the Australia Telescope National Facility. Simultaneous observations of the 1665- and 1667-MHz hydroxyl ground-state transitions yield a series of maps at velocity spacing 0.09kms−1, in both right- and left-hand circular polarization, with tenth-arcsec spatial resolution. Several clusters of maser spots have been detected within a five-arcsec region. Eight Zeeman pairs were found, and in one case, at 1665 MHz, there is a nearby 1667-MHz pair indicating a similar value of magnetic field and velocity. Over the whole site, all magnetic field estimates are toward us (negative), and range from -3.7 to -5.8 mG. We also compared the morphology and kinematics of the 1665- and 1667-MHz maser spots with those from the excited state of OH at 6035 MHz and from methanol at 6668 MHz.

Japanese VLBI network observations of 6.7-GHz methanol masers I. Array

AbstractThe Japanese VLBI network (JVN) has begun observations of 6.7-GHz methanol masers associated with massive star-forming regions. The JVN is a newly-established VLBI array with baselines ranging from 50 to 2560 km spread across the Japanese islands. Three observing bands of 6.7, 8.4, and 22 GHz are now available. The array consists of ten antennas: VERA Mizusawa 20 m, VERA Ishigaki 20 m, VERA Iriki 20 m, Usuda 64 m, Yamaguchi 32 m, Tomakomai 11 m, Tsukuba 32 m, Kashima 34 m, VERA Ogasawara 20 m, and Gifu 11 m, the first five of which have 6.7-GHz receiving systems. In summer 2005, we obtained the first fringes at 6.7 GHz, and VLBI images of 12 methanol maser sites including seven that had not previously been imaged with VLBI at this band. In 2006 summer, we obtained phase-reference observations toward several methanol maser sites.

Mopra observations of G305.2+0.2: massive star formation at different evolutionary stages?

We have successfully used a new on-the-fly mapping technique with the Mopra radiotelescope to image G305.2+0.2 in transitions of 13CO, HCO+, N2H+, CH3CN and CH3OH. All these species appear to be concentrated towards the infrared-quiet methanol maser site G305A (G305.21+0.21). We suggest that this region contains an extremely deeply embedded site of massive star formation, with comparable qualities to the low mass Class 0 stage. The infrared-bright methanol maser site G305B (G305.21+0.20) also exhibits emission in all the mapped transitions, but always at a lower level. We suggest this is because it harbours a site of massive star formation older and more developed than G305.21+0.21. All transitions appear to be extended beyond the size of the Mopra beam (30). 13CO and HCO+ line wings are suggestive of an outflow in the region, but the spatial resolution of these data is insufficient to identify the powering source. A narrow-lined (1.6 km/s compared to a typical line FWHM of 6.4 km/s) N2H+ source (G305SW) is found 90 to the south-west of the main star forming centres, which does not correspond to any CH3CN or CH3OH source, nor does it correspond well to 13CO or HCO+ emission in the vicinity. We suggest this may be a massive, cold, quiescent and possibly prestellar core.