The diversity of methanol maser morphologies  from VLBI observations

Bartkiewicz, A.; Szymczak, M.; Langevelde, H. J. van; Richards, A. M. S.; Pihlström, Y. M.

doi:10.1051/0004-6361/200912250

Cited by 115 publications

(286 citation statements)

References 41 publications

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“…7 we show the total flux spectra of the CH 3 OH masers detected with MERLIN and the EVN in 2005 and 2009, respectively. Generally, the EVN resolved out between 60% and 90% of the flux when 6.7-GHz CH 3 OH masers were observed with both these instruments (e.g., Minier et al 2002;Bartkiewicz et al 2009;Torstensson et al 2011). This indicates the presence of emission structures on scales that are resolved by the EVN, i.e.…”

Section: Discussionmentioning

confidence: 88%

The properties and polarization of the H₂O and CH₃OH maser environment of NGC 7538-IRS 1

Surcis

Vlemmings

Torres

et al. 2011

A&A

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Context. NGC 7538 is a complex massive star-forming region. The region is composed of several radio continuum sources, one of which is IRS 1, a high-mass protostar, from which a 0.3 pc molecular bipolar outflow was detected. Several maser species have been detected around IRS 1. The CH 3 OH masers have been suggested to trace a Keplerian-disk, while the H 2 O masers are almost aligned to the outflow. More recent results suggested that the region hosts a torus and potentially a disk, but with a different inclination than the Keplerian-disk that is supposed to be traced by the CH 3 OH masers. Aims. Tracing the magnetic field close to protostars is fundamental for determining the orientation of the disk/torus. Recent studies showed that during the protostellar phase of high-mass star formation the magnetic field is oriented along the outflows and around or on the surfaces of the disk/torus. The observations of polarized maser emissions at milliarcsecond resolution can make a crucial contribution to understanding the orientation of the magnetic field and, consequently, the orientation of the disk/torus in NGC 7538-IRS 1. Methods. The NRAO Very Long Baseline Array was used to measure the linear polarization and the Zeeman-splitting of the 22 GHz H 2 O masers toward NGC 7538-IRS 1. The European VLBI Network and the MERLIN telescopes were used to measure the linear polarization and the Zeeman-splitting of the 6.7 GHz CH 3 OH masers toward the same region. Results. We detected 17 H 2 O masers and 49 CH 3 OH masers at high angular resolution. We detected linear polarization emission toward two H 2 O masers and toward twenty CH 3 OH masers. The CH 3 OH masers, most of which only show a core structure, seem to trace rotating and potentially infalling gas in the inner part of a torus. Significant Zeeman-splitting was measured in three CH 3 OH masers. No significant (3σ) magnetic field strength was measured using the H 2 O masers. We also propose a new description of the structure of the NGC 7538-IRS 1 maser region.

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Section: Discussionmentioning

confidence: 88%

The properties and polarization of the H₂O and CH₃OH maser environment of NGC 7538-IRS 1

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Vlemmings

Torres

et al. 2011

A&A

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“…Class II CH 3 OH masers are seen to trace discs or disc-like features when observed on milli-arcsecond scales (e.g. Bartkiewicz et al 2009) and are uniquely associated with regions of massive star formation. H 2 O masers are typically associated with outflow regions in both high and low mass star-forming regions 16h30m57.00s 58.00s 59.00s 31m00.00s…”

Section: Results and Analysismentioning

confidence: 99%

Tightening the belt: Constraining the mass and evolution in SDC335

Avison

Peretto

Fuller

et al. 2015

A&A

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Aims. Recent ALMA observations identified one of the most massive star-forming cores yet observed in the Milky Way: SDC335-MM1, within the infrared dark cloud SDC335.579-0.292. Along with an accompanying core MM2, SDC335 appears to be in the early stages of its star formation process. We aim to constrain the properties of the stars forming within these two massive millimetre sources. Methods. Observations of SDC335 at 6, 8, 23 and 25 GHz were made with the Australia Telescope Compact Array. We report the results of these continuum measurements, which combined with archival data, allow us to build and analyse the spectral energy distributions (SEDs) of the compact sources in SDC335. Results. Three hyper-compact H regions within SDC335 are identified, two of which are within the MM1 core. For each HCH region, we fit a free-free emission curve to the data, providing the derivation of the sources' emission measure, ionising photon flux, and electron density. Using these physical properties we assign each HCH region a zero-age main sequence (ZAMS) spectral type, finding two protostars with characteristics of spectral type B1.5 and one with a lower limit of B1-B1.5. Ancillary data from infrared to mm wavelength are used to construct free-free component subtracted SEDs for the mm-cores, which allows us to calculate the bolometric luminosities and revise the previous gas mass estimates. Conclusions. The measured luminosities for the two mm-cores are lower than expected from accreting sources displaying characteristics of the ZAMS spectral type assigned to them. The protostars are still actively accreting, suggesting that a mechanism is limiting the accretion luminosity. We present the case for two different mechanisms capable of causing lower than expected accretion luminosity. Finally, using the ZAMS mass values as lower limit constraints, a final stellar population for SDC335 was synthesised finding SDC335 is likely to be in the process of forming a stellar cluster comparable to the Trapezium cluster and NGC 6334 I(N).

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“…G22.357+0.066, G25.411+0.105 and G45.473+0.134 have been observed at 6.7 GHz with milliarcsecond (mas) resolution (Bartkiewicz et al 2009. Their maser cloud maps are shown in Figure 9 together with the position of the nearest infrared source for which the spectral density distribution is consistent with an HMYSO candidate.…”

Section: Size Of Maser Region Showing Periodic Variabilitymentioning

confidence: 91%

“…The maser spectra obtained with the VLBI and single dish at nearly the same epoch are very similar. This means that almost all maser clouds have compact cores and the source structure was fully recovered with a 6 mas×12 mas beam (Bartkiewicz et al 2009). There is a 5 d delay in the peak of the flares between the 80.09 and 83.42 km s −1 features (Table 1) that can be explained by light travel time between the maser clouds of 80.23 and 83.57 km s −1 (Fig.…”

Section: Size Of Maser Region Showing Periodic Variabilitymentioning

confidence: 95%

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Discovery of four periodic methanol masers and updated light curve for a further one

Szymczak

Wolak

Bartkiewicz

2015

Monthly Notices of the Royal Astronomical Society

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We report the discovery of 6.7 GHz methanol maser periodic flares in four massive star forming regions and the updated light curve for the known periodic source G22.357+0.066. The observations were carried out with the Torun 32 m radio telescope between June 2009 and April 2014. Flux density variations with period of 120 to 245 d were detected for some or all spectral features. A variability pattern with a fast rise and relatively slow fall on time-scale of 30−60 d dominated. A reverse pattern was observed for some features of G22.357+0.066, while sinusoidal-like variations were detected in G25.411+0.105. A weak burst lasting ∼520 d with the velocity drift of 0.24 km s −1 yr −1 occurred in G22.357+0.066. For three sources for which high resolution maps are available, we found that the features with periodic behaviour are separated by more than 500 au from those without any periodicity. This suggests that the maser flares are not triggered by large-scale homogeneous variations in either the background seed photon flux or the luminosity of the exciting source and a mechanism which is able to produce local changes in the pumping conditions is required.

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The diversity of methanol maser morphologies from VLBI observations

Cited by 115 publications

References 41 publications

The properties and polarization of the H₂O and CH₃OH maser environment of NGC 7538-IRS 1

The properties and polarization of the H₂O and CH₃OH maser environment of NGC 7538-IRS 1

Tightening the belt: Constraining the mass and evolution in SDC335

Discovery of four periodic methanol masers and updated light curve for a further one

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The diversity of methanol maser morphologies from VLBI observations

Cited by 115 publications

References 41 publications

The properties and polarization of the H2O and CH3OH maser environment of NGC 7538-IRS 1

The properties and polarization of the H2O and CH3OH maser environment of NGC 7538-IRS 1

Tightening the belt: Constraining the mass and evolution in SDC335

Discovery of four periodic methanol masers and updated light curve for a further one

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Product

Resources

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The properties and polarization of the H₂O and CH₃OH maser environment of NGC 7538-IRS 1

The properties and polarization of the H₂O and CH₃OH maser environment of NGC 7538-IRS 1