EVN observations of 6.7 GHz methanol maser polarization in massive star-forming regions

Surcis, G.; Vlemmings, Wouter; Langevelde, H. J. van; Kramer, B. Hutawarakorn; Quiroga-Nuñez, Luis Henry

doi:10.1051/0004-6361/201321501

Cited by 24 publications

(40 citation statements)

References 103 publications

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“…In these models, the collapsing core flattens preferably along a direction perpendicular to that of the magnetic field lines. These predictions are consistent with the general result of a polarimetric survey of CH 3 OH masers towards highmass star forming regions (Surcis et al 2013) and suggest that the magnetic field may be important in regulating the dynamics of the mass-accretion and mass-loss in high-mass YSOs. In this framework, an edge-on geometry for protostellar disks could be favoured if the magnetic field in the natal core (before collapse) was oriented near the plane of the sky.…”

Section: General Implications Of the Model For Ngc 7538 Irs1supporting

confidence: 88%

A multiple system of high-mass YSOs surrounded by disks in NGC 7538 IRS1

Moscadelli

Goddi

2014

A&A

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Context. It has been claimed that NGC 7538 IRS1 is a high-mass young stellar object (YSO) with 30 M , surrounded by a rotating Keplerian disk, probed by a linear distribution of methanol masers. The YSO is also powering a strong compact Hii region or ionized wind, and is driving at least one molecular outflow. The axis orientations of the different structures (ionized gas, outflow, and disk) are, however, misaligned, which has led to the different competing models proposed to explain individual structures. Aims. We investigate the 3D kinematics and dynamics of circumstellar gas with very high linear resolution, from tens to 1500 AU, with the ultimate goal of building a comprehensive dynamical model for what is considered the best high-mass accretion disk candidate around an O-type young star in the northern hemisphere. Methods. We used high-angular resolution observations of 6.7 GHz CH 3 OH masers with the EVN, NH 3 inversion lines with the JVLA B-Array, and radio continuum with the VLA A-Array. In particular, we employed four different observing epochs of EVN data at 6.7 GHz, spanning almost eight years, which enabled us to measure line-of-sight (l.o.s.) accelerations and proper motions of CH 3 OH masers, besides l.o.s. velocities and positions (as done in previous works). In addition, we imaged highly excited NH 3 inversion lines, from (6,6) to (13,13), which enabled us to probe the hottest molecular gas very close to the exciting source(s). Results. We confirm previous results that five 6.7 GHz maser clusters (labeled from "A" to "E") are distributed over a region extended N-S across ≈1500 AU, and are associated with three components of the radio continuum emission. We propose that these maser clusters identify three individual high-mass YSOs in NGC 7538 IRS1, named IRS1a (associated with clusters "B" and "C"), IRS1b (associated with cluster "A"), and IRS1c (associated with cluster "E"). We find that the 6.7 GHz masers distribute along a line, with a regular variation in V LSR with position, along the major axis of the distribution of maser cluster "A" and the combined clusters "B" + "C". A similar V LSR gradient (although shallower) is also detected in the NH 3 inversion lines. Interestingly, the variation in V LSR with projected position is not linear but quadratic for both maser clusters. We measure proper motions for 33 maser features, which have an average amplitude (4.8 ± 0.6 km s −1 ) similar to the variation in V LSR across the maser cluster, and are approximately parallel to the clusters' elongation axes. By studying the time variation in the maser spectrum, we also derive l.o.s. accelerations for 30 features, with typical amplitude of ∼10 −3 −10 −2 km s −1 yr −1 . We modeled the masers in both clusters "A" and "B" + "C" in terms of an edge-on disk in centrifugal equilibrium. Based on our modeling, masers of clusters "B" + "C" may trace a quasi-Keplerian ∼1 M , thin disk, orbiting around a high-mass YSO, IRS1a, of up to ≈25 M . This YSO dominates the bolometric luminosity of the region. The d...

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Section: General Implications Of the Model For Ngc 7538 Irs1supporting

confidence: 88%

A multiple system of high-mass YSOs surrounded by disks in NGC 7538 IRS1

Moscadelli

Goddi

2014

A&A

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“…In addition to being bright, water masers can be associated with high mass star forming regions (HMSFRs), while class II 6.7 and 12 GHz methanol masers are uniquely associated with HMSFRs (e.g. Breen et al 2013;Surcis et al 2013). By detecting 6.7 GHz methanol masers, we trace the Galactic spiral structure because HMSFRs are expected to be born close to a spiral arm and evolve more quickly than low-mass stars ( et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Simulated Galactic methanol maser distribution to constrain Milky Way parameters

Quiroga-Nuñez

Langevelde

Reid

et al. 2017

A&A

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Context. Using trigonometric parallaxes and proper motions of masers associated with massive young stars, the Bar and Spiral Structure Legacy (BeSSeL) survey has reported the most accurate values of the Galactic parameters so far. The determination of these parameters with high accuracy has a widespread impact on Galactic and extragalactic measurements. Aims. This research is aimed at establishing the confidence with which such parameters can be determined. This is relevant for the data published in the context of the BeSSeL survey collaboration, but also for future observations, in particular from the southern hemisphere. In addition, some astrophysical properties of the masers can be constrained, notably the luminosity function. Methods. We have simulated the population of maser-bearing young stars associated with Galactic spiral structure, generating several samples and comparing them with the observed samples used in the BeSSeL survey. Consequently, we checked the determination of Galactic parameters for observational biases introduced by the sample selection. Results. Galactic parameters obtained by the BeSSeL survey do not seem to be biased by the sample selection used. In fact, the published error estimates appear to be conservative for most of the parameters. We show that future BeSSeL data and future observations with southern arrays will improve the Galactic parameters estimates and smoothly reduce their mutual correlation. Moreover, by modeling future parallax data with larger distance values and, thus, greater relative uncertainties for a larger numbers of sources, we found that parallax-distance biasing is an important issue. Hence, using fractional parallax uncertainty in the weighting of the motion data is imperative. Finally, the luminosity function for 6.7 GHz methanol masers was determined, allowing us to estimate the number of Galactic methanol masers.

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“…In fact, 70% of their total Effelsberg+Parkes flux-limited (>50 Jy) sample (51 sources) show circularly polarized emission. This has also been confirmed at milliarcsecond scale via interferometric observations for a smaller number of sources (Surcis et al 2012(Surcis et al , 2013. However, the exact proportionality between the measured Zeeman-splitting of the methanol maser emission and the magnetic field strength is still under investigation by a team of theoretical chemists and astrophysicists and the final results will be published in 2015.…”

Section: Pos(aaska14)110mentioning

confidence: 66%

“…The role of magnetic fields during the formation of high-mass stars (M > 8M ) is still a matter of debate, even in the face of many recent investigations, both theoretical and observational (Seifried et al 2012;Surcis et al 2013). Recent magnetohydrodynamical simulations show that the collimation of outflows and the formation of accretion discs strongly depend on the strength of magnetic fields (Seifried et al 2012).…”

Section: Molecular Clouds and Star Forming Regions In The Milky Waymentioning

confidence: 99%

“…The best probes of magnetic fields at small scales close to YSOs are masers, in particular the Class II methanol maser transition at 6.7 GHz and 22 GHz water masers (Vlemmings et al 2006a;Surcis et al 2011Surcis et al , 2013Surcis et al , 2014. Methanol masers, which are the most numerous high-mass star formation (HMSF) maser species, are playing a crucial role in determining the magnetic field morphology (Vlemmings et al 2010;Surcis et al 2012Surcis et al , 2013.…”

Section: Pos(aaska14)110mentioning

confidence: 99%

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Measuring Magnetic Fields Near and Far with the SKA via the Zeeman Effect

Robishaw¹,

Green²,

Surcis³

et al. 2015

Proceedings of Advancing Astrophysics With the Square Kilometre Array — PoS(AASKA14)

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The measurement of Zeeman splitting in spectral lines-both in emission and absorption-can provide direct estimates of the magnetic field strength and direction in atomic and molecular clouds, both in our own Milky Way and in external galaxies. This method will probe the magnetic field in the warm and cold neutral components of the interstellar medium, providing a complement to the extensive SKA Faraday studies planning to probe the field in the ionized components.Advancing Astrophysics with the Square Kilometre Array

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EVN observations of 6.7 GHz methanol maser polarization in massive star-forming regions

Cited by 24 publications

References 103 publications

A multiple system of high-mass YSOs surrounded by disks in NGC 7538 IRS1

A multiple system of high-mass YSOs surrounded by disks in NGC 7538 IRS1

Simulated Galactic methanol maser distribution to constrain Milky Way parameters

Measuring Magnetic Fields Near and Far with the SKA via the Zeeman Effect

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