Studies of ultracompact H II regions -- I. Methanol maser survey of IRAS-selected sources

Walsh, A. J.; Hyland, A. R.; Robinson, G.; Burton, M. G.

doi:10.1093/mnras/291.2.261

Cited by 238 publications

(320 citation statements)

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“…The data presented here as well as other studies (e.g., Walsh et al 1997;1998;Phillips et al 1998;Minier et al 2000a; indicate that the ignition of a massive star, and thus the formation of an ultracompact H region, alters these conditions swiftly and stops further CH 3 OH maser emission very soon.…”

Section: Discussionsupporting

confidence: 78%

“…Examples of these studies on the H 2 O side are, e.g., Torrelles et al (1997Torrelles et al ( , 1998, Codella & Felli (1995), and Codella et al (1996Codella et al ( , 1997, whereas recent studies of CH 3 OH masers include Walsh et al (1997Walsh et al ( , 1998, Send offprint requests to: H. Beuther, e-mail: beuther@mpifr-bonn.mpg.de Another finding is that both maser types are occasionally spatially coincident with ultracompact H regions, but more often with hot molecular cores and/or massive molecular outflows (Hofner & Churchwell 1996;Codella et al 1996Codella et al , 1997Walsh et al 1998;Garay & Lizano 1999;Minier et al 2001). Recent studies by Walsh et al (2001) indicate that CH 3 OH masers often are associated with mid-infrared sources that should be luminous enough to produce strong ionizing radiation.…”

Section: Introductionmentioning

confidence: 99%

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CH₃OH and H₂O masers in high-mass star-forming regions

Beuther

Walsh

Schilke

et al. 2002

A&A

183

280

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Abstract. We present a comparison of Class  CH 3 OH (6.7 GHz) and H 2 O (22.2 GHz) masers at high spatial resolution in a sample of 29 massive star-forming regions. Absolute positions of both maser types are compared with mm dust continuum, cm continuum and mid-infrared sources. All maser features -regardless of the species -are associated with massive mm cores, but only 3 out of 18 CH 3 OH masers and 6 out of 22 H 2 O masers are associated with cm emission likely indicating the presence of a recently ignited massive star. These observations of a homogenous sample of massive, young star-forming regions confirm earlier results, obtained for each maser species separately, that both maser types are signposts of high-mass star formation in very early evolutionary stages. The data are consistent with models that explain CH 3 OH maser emission by radiative pumping in moderately hot cores, requiring the absence, or only weak, free-free cm continuum radiation due to recently ignited stars. Mid-infrared sources are associated with both maser types in approximately 60% of the observed fields. Thus, mid-infrared objects may power maser sites, but the detection of strong mid-infrared emission is not strictly necessary because it might be heavily extincted. A comparison of the spatial separations between the di fferent observed quantities and other properties of the star-forming regions does not reveal any correlation. Our data suggest that CH 3 OH and H 2 O masers need a similar environment (dense and warm molecular gas), but that, due to the different excitation processes (radiative pumping for CH 3 OH and collisional pumping for H 2 O), no spatial correlations exist. Spatial associations are probably coincidences due to insufficient angular resolution and projection effects. The kinematic structures we find in the different maser species show no recognizable pattern, and we cannot draw firm conclusions as to whether the features are produced in disks, outflows or expanding shock waves.

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Section: Discussionsupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

CH₃OH and H₂O masers in high-mass star-forming regions

Beuther

Walsh

Schilke

et al. 2002

A&A

183

280

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“…High-velocity wings in CO lines detected by Urquhart et al (2009) and Otrupcek et al (2000) might indicate the presence of a molecular outflow. Methanol maser emission, which is believed to be associated with high-mass star formation, was also observed towards this source by Walsh et al (1997).…”

Section: Description Of the Samplementioning

confidence: 70%

Tracing the evolutionary stage of Bok globules: CCS and NH₃

Marka¹,

Schreyer²,

Launhardt

et al. 2011

A&A

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Aims. We investigate a previously proposed correlation between the chemical properties and the physical evolutionary stage of isolated low-mass star-forming regions. The N NH 3 /N CCS abundance ratio has been proposed to be a potentially useful indicator of the evolutionary stage of cloud cores, and we study its applicability for isolated Bok globules. Methods. We searched for CCS(2 1 -1 0 ) emission in 42 Bok globules both with and without signs of current star formation. A set of NH 3 measurements was compiled from measurements available in the literature and from our own observations. The abundance ratio of both molecules is discussed with respect to the evolutionary stage of the objects and in the context of chemical models.Results. We determine the N NH 3 /N CCS ratio for 18 Bok globules and find that it is moderately high and roughly similar across all evolutionary stages from starless and prestellar cores towards internally heated cores harboring protostars of Class 0, Class I, or later. We do not find any Bok globules with extremely high CCS abundances analogous to carbon-chain producing regions in dark cloud cores. The observed range of N NH 3 /N CCS implies that all of the observed Bok globules are in a relatively evolved chemical state.

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“…While various samples of high-mass proto-stellar objects have been defined based on various criteria, such as maser emission (e.g., Walsh et al 1997;Pestalozzi et al 2005) and infrared (IR) colors (Palla et al 1991;Molinari et al 1996;Sridharan et al 2002;Lumsden et al 2002;Robitaille et al 2008), an unbiased sample has not yet been assembled. Much effort has focused on follow-up studies of bright IR sources detected by the Infrared Astronomy Satellite (IRAS) and showing far-infrared (FIR) colors typical of ultra-compact H ii regions (Wood & Churchwell 1989), e.g., in high-density molecular tracers (Bronfman et al 1996;Molinari et al 1996), dust continuum emission , or maser emission (e.g., Palla et al 1993;Beuther et al 2002).…”

Section: Article Published By Edp Sciencesmentioning

confidence: 99%

ATLASGAL – The APEX telescope large area survey of the galaxy at 870 $\mathsf{\mu}$m

Schüller¹,

Menten²,

Contreras

et al. 2009

A&A

729

927

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Context. Thanks to its excellent 5100 m high site in Chajnantor, the Atacama Pathfinder Experiment (APEX) systematically explores the southern sky at submillimeter wavelengths, in both continuum and spectral line emission. Studying continuum emission from interstellar dust is essential to locating the highest density regions in the interstellar medium, and deriving their masses, column densities, density structures, and large-scale morphologies. In particular, the early stages of (massive) star formation remain poorly understood, mainly because only small samples of high-mass proto-stellar or young stellar objects have been studied in detail so far. Aims. Our goal is to produce a large-scale, systematic database of massive pre-and proto-stellar clumps in the Galaxy, to understand how and under what conditions star formation takes place. Only a systematic survey of the Galactic Plane can provide the statistical basis for unbiased studies. A well characterized sample of Galactic star-forming sites will deliver an evolutionary sequence and a mass function of high-mass, star-forming clumps. This systematic survey at submillimeter wavelengths also represents a preparatory work for Herschel and ALMA. Methods. The APEX telescope is ideally located to observe the inner Milky Way. The Large APEX Bolometer Camera (LABOCA) is a 295-element bolometer array observing at 870 μm, with a beam size of 19. 2. Taking advantage of its large field of view (11. 4) and excellent sensitivity, we started an unbiased survey of the entire Galactic Plane accessible to APEX, with a typical noise level of 50−70 mJy/beam: the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). Results. As a first step, we covered ∼95 deg 2 of the Galactic Plane. These data reveal ∼6000 compact sources brighter than 0.25 Jy, or 63 sources per square degree, as well as extended structures, many of them filamentary. About two thirds of the compact sources have no bright infrared counterpart, and some of them are likely to correspond to the precursors of (high-mass) proto-stars or protoclusters. Other compact sources harbor hot cores, compact H ii regions, or young embedded clusters, thus tracing more evolved stages after massive stars have formed. Assuming a typical distance of 5 kpc, most sources are clumps smaller than 1 pc with masses from a few 10 to a few 100 M . In this first introductory paper, we show preliminary results from these ongoing observations, and discuss the mid-and long-term perspectives of the survey.

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Studies of ultracompact H II regions -- I. Methanol maser survey of IRAS-selected sources

Cited by 238 publications

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CH₃OH and H₂O masers in high-mass star-forming regions

CH₃OH and H₂O masers in high-mass star-forming regions

Tracing the evolutionary stage of Bok globules: CCS and NH₃

ATLASGAL – The APEX telescope large area survey of the galaxy at 870 $\mathsf{\mu}$m

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Studies of ultracompact H II regions -- I. Methanol maser survey of IRAS-selected sources

Cited by 238 publications

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CH3OH and H2O masers in high-mass star-forming regions

CH3OH and H2O masers in high-mass star-forming regions

Tracing the evolutionary stage of Bok globules: CCS and NH3

ATLASGAL – The APEX telescope large area survey of the galaxy at 870 $\mathsf{\mu}$m

Contact Info

Product

Resources

About

CH₃OH and H₂O masers in high-mass star-forming regions

CH₃OH and H₂O masers in high-mass star-forming regions

Tracing the evolutionary stage of Bok globules: CCS and NH₃