Observations of warm dust near methanol masers

Walsh, A. J.; Macdonald, G. H.; Alvey, N. D. S.; Burton, M. G.; Lee, J.-K.

doi:10.1051/0004-6361:20031191

Cited by 99 publications

(158 citation statements)

References 39 publications

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“…Their derived values are about one order of magnitude smaller than the those derived by us, a difference most likely due to the difference in luminosity of the two samples. Walsh et al (2003) mapped continuum emission at 1200, 850 and 450 µm toward 71 fields of methanol masers. A comparison of the maps at 1200, 850 and 450 µm of the 14 sources in common between this and our survey shows a very good agreement in the morphologies of the dust emission.…”

Section: Comparison With Previous Workmentioning

confidence: 99%

SIMBA survey of southern high-mass star forming regions

Faundez

Bronfman

Garay

et al. 2004

A&A

244

334

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Abstract.We report the results of a 1.2 mm continuum emission survey toward 146 IRAS sources thought to harbour highmass star forming regions. The sources have FIR colors typical of UCHII regions and were detected in the CS(2 → 1) line survey of Bronfman et al. (1996). Regions of 15 × 10 , centered on each IRAS source, were mapped with an angular resolution of ∼24 , using the SIMBA array on the SEST telescope. 1.2 mm emission was detected toward all IRAS sources. We find that the dust cores associated with these sources have typical sizes of 0.4 pc and masses of 5 × 10 3 M . Dust temperatures and luminosities, derived from the SED, are typically 32 K and 2.3 × 10 5 L .

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Section: Comparison With Previous Workmentioning

confidence: 99%

SIMBA survey of southern high-mass star forming regions

Faundez

Bronfman

Garay

et al. 2004

A&A

244

334

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“…While the SE emission is associated with an MSX point source (Walsh et al 2003), the fainter NW source (≈0.2 Jy at 18.1 μm) is associated with weak, reddened NIR emission (Testi et al 1994) and was tentatively classified as a Class I object (De Buizer et al 2005). The NW source is also coincident with the submillimeter (450 and 850 μm) continuum emission from the region, which may indicate that this is a younger, more embedded source than the one responsible for the SE emission (Walsh et al 2003;Williams et al 2004Williams et al , 2005. Single-dish surveys toward G16.59-0.05 detected redshifted self-absorption in N 2 H + , HCO + , H 13 CO + , and H 2 CO rotational lines, which suggests there are inflow motions Wu et al 2007; Thomas & Fuller 2008).…”

Section: The Hmsfr G1659-005mentioning

confidence: 99%

VLBI study of maser kinematics in high-mass star-forming regions

Sanna

Moscadelli

Cesaroni

et al. 2010

A&A

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Aims. To study the high-mass star-forming process, we started a large project to unveil the gas kinematics close to young stellar objects (YSOs) through the Very Long Baseline Interferometry (VLBI) of maser associations. By comparing the high spatial resolution maser data that traces the inner kinematics of the (proto)stellar cocoon with interferometric thermal data that traces the large-scale environment of the hot molecular core (HMC) harboring the (proto)stars, we can investigate the nature and identify the sources of large-scale motions. The present paper focuses on the high-mass star-forming region G16.59-0.05. Methods. Using the VLBA and the EVN arrays, we conducted phase-referenced observations of the three most powerful maser species in G16.59-0.05: H 2 O at 22.2 GHz (4 epochs), CH 3 OH at 6.7 GHz (3 epochs), and OH at 1.665 GHz (1 epoch). In addition, we performed high-resolution (≥0. 1), high-sensitivity (<0.1 mJy) VLA observations of the radio continuum emission from the starforming region at 1.3 and 3.6 cm.Results. This is the first work to report accurate measurements of the relative proper motions of the 6.7 GHz CH 3 OH masers. The different spatial and 3-D velocity distributions clearly indicate that the 22 GHz water and 6.7 GHz methanol masers trace different kinematic environments. The bipolar distribution of 6.7 GHz maser line-of-sight velocities and the regular pattern of observed proper motions suggest that these masers are tracing rotation around a central mass of about 35 M . The flattened spatial distribution of the 6.7 GHz masers, oriented NW−SE, suggests that they can originate in a disk/toroid rotating around the massive YSO that drives the 12 CO (2−1) outflow, oriented NE−SW, observed on an arcsec scale. The extended, radio continuum source observed close to the 6.7 GHz masers could be excited by a wide-angle wind emitted from the YSO associated with the methanol masers, and such a wind has proven to be energetic enough to drive the NE−SW 12 CO (2−1) outflow. The H 2 O masers are distributed across a region offset about 0. 5 to the NW of the CH 3 OH masers, in the same area as where the emission of high-density molecular tracers, typical of HMCs, was detected. We postulate that a distinct YSO, possibly in an earlier evolutionary phase than what excites the methanol masers, is responsible for the excitation of the water masers and the HMC molecular lines.

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“…Interstellar 22.2 GHz water maser emission represents an excellent tool to search for young protostars, because it is associated with hot molecular cores (HMCs) where the newly formed star is efficiently heating the surrounding medium up to temperatures of hundreds of Kelvin (Cesaroni et al 1994;Hofner & Churchwell 1996;Kurtz et al 2000). Several sources of the observed sample are also associated with OH masers at 1.7 GHz (Forster & Caswell 1989), which are usually excited in the material surrounding already formed UC Hii regions as well as molecular outflows (e.g., Walsh et al 2003). Finally, in some sources of the present sample, Class II 6.7 GHz methanol (CH 3 OH) masers have also been detected (Walsh et al 1998), which are another excellent tool for the earliest phases of OB-type star formation (e.g., Walsh et al 2001Walsh et al , 2003.…”

Section: Source Selectionmentioning

confidence: 99%

“…Several sources of the observed sample are also associated with OH masers at 1.7 GHz (Forster & Caswell 1989), which are usually excited in the material surrounding already formed UC Hii regions as well as molecular outflows (e.g., Walsh et al 2003). Finally, in some sources of the present sample, Class II 6.7 GHz methanol (CH 3 OH) masers have also been detected (Walsh et al 1998), which are another excellent tool for the earliest phases of OB-type star formation (e.g., Walsh et al 2001Walsh et al , 2003.…”

Section: Source Selectionmentioning

confidence: 99%

Looking for high-mass young stellar objects: H$_{\sf 2}$O and OH masers in ammonia cores

Codella

Cesaroni

López-Sepulcre

et al. 2010

A&A

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Context. The earliest stages of high-mass star formation have yet to be characterised well, because high-angular resolution observations are required to infer the properties of the molecular gas hosting the newly formed stars. Aims. We search for high-mass molecular cores in a large sample of 15 high-mass star-forming regions that are observed at highangular resolution, extending a pilot survey based on a smaller number of objects. Methods. The sample was chosen from surveys of H 2 O and OH masers to favour the earliest phases of high-mass star formation. Each source was first observed with the 32-m single-dish Medicina antenna in the (1, 1) and (2, 2) inversion transitions at 1.3 cm of ammonia, which is an excellent tracer of dense gas. High-resolution maps in the NH 3 (2, 2) and (3, 3) lines and the 1.3 cm continuum were obtained successively with the VLA interferometer. Results. We detect continuum emission in almost all the observed star-forming regions, which corresponds to extended and UCHii regions created by young stellar objects with typical luminosities of ∼10 4 L . However, only in three cases do we find a projected overlap between Hii regions and H 2 O and OH maser spots. On the other hand, the VLA images detect eight ammonia cores closely associated with the maser sources. The ammonia cores have sizes of ∼10 4 AU, and high masses (up to 10 4 M ), and are very dense (from ∼10 6 to a few ×10 9 cm −3 ). The typical relative NH 3 abundance is ≤10 −7 , in agreement with previous measurements in highmass star-forming regions.Conclusions. The statistical analysis of the distribution between H 2 O and OH masers, NH 3 cores, and Hii regions confirms that the earliest stages of high-mass star formation are characterised by high-density molecular cores with temperatures of on average ≥30 K, either without a detectable ionised region or associated with a hypercompact Hii region.

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Observations of warm dust near methanol masers

Cited by 99 publications

References 39 publications

SIMBA survey of southern high-mass star forming regions

SIMBA survey of southern high-mass star forming regions

VLBI study of maser kinematics in high-mass star-forming regions

Looking for high-mass young stellar objects: H$_{\sf 2}$O and OH masers in ammonia cores

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