Mapping Observations of 6.7GHz Methanol Masers with the Japanese VLBI
                    Network

Sugiyama, Koichiro; Fujisawa, Kenta; Doi, Akira; Honma, Mareki; Kobayashi, Hideyuki; Bushimata, Takeshi; Mochizuki, Nobutatsu; Murata, Yasuhiro

doi:10.1093/pasj/60.1.23

Cited by 36 publications

(45 citation statements)

References 66 publications

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“…The emission is constrained to the velocity interval −1.5 km s −1 and −4.5 km s −1 . The morphology and velocity field that we find of the 6.7 GHz methanol masers agree well with previous measurements using different telescopes: Vlemmings et al (2010) (MERLIN); Sugiyama et al (2007Sugiyama et al ( , 2008b (VERA). One notable difference between our spectrum and earlier measurements is the lack of a feature at ∼ −4.6 km s −1 as seen by both Vlemmings et al (2010) and Sugiyama et al (2008a).…”

Section: 7 Ghz Resultssupporting

confidence: 91%

“…Recent multi-epoch observations of water masers in the region indicate the presence of a slower wide-angle outflow in addition to the high-velocity collimated jet observed in radio continuum (Torrelles et al 2010). Sugiyama et al (2008b) find the 6.7 GHz methanol maser emission to be constrained to two individual clumps with blueshifted masers to the east and redshifted masers in a linear configuration to the west. Moreover, single-dish monitoring of the 6.7 GHz methanol masers has shown the variation in the maser emission in the blueshifted and redshifted cluster to be synchronised and anti-correlated (Sugiyama et al 2008a).…”

Section: Introductionmentioning

confidence: 84%

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Methanol masers and millimetre lines: a common origin in protostellar envelopes

Torstensson¹,

Langevelde²,

Tak³

et al. 2012

Proc. IAU

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To understand the origin of the CH3OH maser emission, we map the distribution and excitation of the thermal CH3OH emission in a sample of 14 relatively nearby (<6 kpc) high-mass star forming regions that are identified through 6.7 GHz maser emission. The images are velocity-resolved and allow us to study the kinematics of the regions. Further, rotation diagrams are created to derive rotation temperatures and column densities of the large scale molecular gas. The effects of optical depth and subthermal excitation are studied with population diagrams. For eight of the sources in our sample the thermal CH3OH emission is compact and confined to a region <0.4 pc and with a central peak close (<0.03 pc) to the position of the CH3OH maser emission. Four sources have more extended thermal CH3OH emission without a clear peak, and for the remaining two sources, the emission is too weak to map. The compact sources have linear velocity gradients along the semi-major axis of the emission of 0.3 – 13 kms−1 pc−1. The rotation diagram analysis shows that in general the highest rotation temperature is found close to the maser position. The confined and centrally peaked CH3OH emission in the compact sources indicates a single source for the CH3OH gas and the velocity fields show signs of outflow in all but one of the sources. The high detection rate of the torsionally excited vt = 1 line and signs of high-K lines at the maser position indicate radiative pumping, though the general lack of measurable beam dilution effects may mean that the masing gas is not sampled well and originates in a very small region.

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Section: 7 Ghz Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 84%

Methanol masers and millimetre lines: a common origin in protostellar envelopes

Torstensson¹,

Langevelde²,

Tak³

et al. 2012

Proc. IAU

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“…Kinematics of the maser spots revealed that outflow/infall dominates over the possible Keplerian rotation in a disc. A similar morphology with a similar kinematic signature was found in the well-known HMSFR Cep A, where, due to additional constraints on the orientation, the radial motions are more likely resulting from infall (Torstensson et al 2011a, Sugiyama et al 2008. Moreover, it seems that the magnetic field plays a role in shaping this morphology (Vlemmings et al 2010).…”

Section: The Morphology Of 67 Ghz Maserssupporting

confidence: 71%

Masers in star forming regions

Bartkiewicz

Langevelde

2012

Proc. IAU

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Abstract. Maser emission plays an important role as a tool in star formation studies. It is widely used for deriving kinematics, as well as the physical conditions of different structures, hidden in the dense environment very close to the young stars, for example associated with the onset of jets and outflows. We will summarize here the recent observational and theoretical progress on this topic since the last maser symposium: the IAU Symposium 242 in Alice Springs.

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“…1c). There are some morphological differences to the southeast of the elongated 3 The 6.7 GHz CH 3 OH maser observations carried out with the Japanese VLBI Network (JVN; Sugiyama et al 2008) and the European VLBI Neatwork (EVN; Surcis et al 2012) were performed without phase-referencing and it is thus impossible to establish the absolute position of the masers. However, the CH 3 OH maser distribution seems to match the OH maser distribution (Brebner et al 1987;Hutawarakorn & Cohen 1999); since the latter are associated with cores A and B, it seems likely that the methanol masers are also associated with these two cores.…”

Section: Continuum Emissionmentioning

confidence: 99%

A necklace of dense cores in the high-mass star forming region G35.20−0.74 N: ALMA observations

Sánchez-Monge

Beltrán

Cesaroni

et al. 2014

A&A

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Context. The formation process of high-mass stars (with masses >8 M ) is still poorly understood, and represents a challenge from both the theoretical and observational points of view. The advent of the Atacama Large Millimeter Array (ALMA) is expected to provide observational evidence to better constrain the theoretical scenarios. Aims. The present study aims at characterizing the high-mass star forming region G35.20−0.74 N, which is found associated with at least one massive outflow and contains multiple dense cores, one of them recently found associated with a Keplerian rotating disk. Methods. We used the radio-interferometer ALMA to observe the G35.20−0.74 N region in the submillimeter continuum and line emission at 350 GHz. The observed frequency range covers tracers of dense gas (e.g., H 13 CO + , C 17 O), molecular outflows (e.g., SiO), and hot cores (e.g., CH 3 CN, CH 3 OH). These observations were complemented with infrared and centimeter data. Results. The ALMA 870 μm continuum emission map reveals an elongated dust structure (∼0.15 pc long and ∼0.013 pc wide; full width at half maximum) perpendicular to the large-scale molecular outflow detected in the region, and fragmented into a number of cores with masses ∼1-10 M and sizes ∼1600 AU (spatial resolution ∼960 AU). The cores appear regularly spaced with a separation of ∼0.023 pc. The emission of dense gas tracers such as H 13 CO + or C 17 O is extended and coincident with the dust elongated structure. The three strongest dust cores show emission of complex organic molecules characteristic of hot cores, with temperatures around 200 K, and relative abundances 0.2-2 × 10 −8 for CH 3 CN and 0.6-5 × 10 −6 for CH 3 OH. The two cores with highest mass (cores A and B) show coherent velocity fields, with gradients almost aligned with the dust elongated structure. Those velocity gradients are consistent with Keplerian disks rotating about central masses of 4-18 M . Perpendicular to the velocity gradients we have identified a large-scale precessing jet/outflow associated with core B, and hints of an east-west jet/outflow associated with core A. Conclusions. The elongated dust structure in G35.20−0.74 N is fragmented into a number of dense cores that may form high-mass stars. Based on the velocity field of the dense gas, the orientation of the magnetic field, and the regularly spaced fragmentation, we interpret this elongated structure as the densest part of a 1D filament fragmenting and forming high-mass stars.

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Mapping Observations of 6.7GHz Methanol Masers with the Japanese VLBI Network

Cited by 36 publications

References 66 publications

Methanol masers and millimetre lines: a common origin in protostellar envelopes

Methanol masers and millimetre lines: a common origin in protostellar envelopes

Masers in star forming regions

A necklace of dense cores in the high-mass star forming region G35.20−0.74 N: ALMA observations

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