Masers in Massive Star-forming Regions Associated with the Brightest Steep-Spectrum [ITAL]IRAS[/ITAL] Point Sources

MacLeod, G. C.; Scalise, E.; Saedt, Sharon; Galt, John; Gaylard, M. J.

doi:10.1086/300538

Cited by 44 publications

(48 citation statements)

References 50 publications

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“…The latter assumes a flat rotation curve with as distance of the Sun to the Galactic center, R 0 = 8.5 kpc, and for the Galactic rotation speed, Θ 0 = 220 km s −1 . However, it is farther than the commonly adopted (near) kinematic distance of 1.8 kpc based on formaldehyde at v LSR = 11.2 km s −1 (MacLeod et al 1998) using the Galactic rotation curve of Wouterloot & Brand (1989), with R 0 = 8.5 kpc, Θ 0 = 220 km s −1 . Our result resolves the near/far kinematic distance ambiguity and locates ON 1 in the Local spur consistent with the near kinematic distance.…”

Section: Onsalamentioning

confidence: 70%

Trigonometric parallaxes of 6.7 GHz methanol masers

Rygl

Brunthaler

Reid³

et al. 2010

A&A

153

131

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Aims. Emission from the 6.7 GHz methanol maser transition is very strong, is relatively stable, has small internal motions, and is observed toward numerous massive star-forming regions in the Galaxy. Our goal is to perform high-precision astrometry using this maser transition to obtain accurate distances to their host regions. −0.06 kpc for S 255. The distances and proper motions yield the full space motions of the star-forming regions hosting the masers, and we find that these regions lag circular rotation on average by ∼17 km s −1 , a value comparable to those found recently by similar studies.

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Section: Onsalamentioning

confidence: 70%

Trigonometric parallaxes of 6.7 GHz methanol masers

Rygl

Brunthaler

Reid³

et al. 2010

A&A

153

131

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“…Previous studies seem to agree that IRAS 17233 is located at the near kinematic distance (between 700 pc and 2.2 kpc, Miettinen et al 2006;Forster & Caswell 1989) rather than at the far distance (∼16 kpc, e.g. MacLeod et al 1998). This is suggested by the high measured intensities of continuum and line emission at practically all the observed wavelengths, which would indicate exceedingly high luminosities if the source were at the far distance and, persuasively, by the fact that it is at an angular distance of more than 0.5 degrees below the Galactic plane.…”

Section: Introductionmentioning

confidence: 90%

Extremely high velocity gas from the massive young stellar objects in IRAS 17233-3606

Leurini¹,

Codella

Zapata

et al. 2009

A&A

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Context. Molecular outflows from high-mass young stellar objects provide an excellent way to study the star formation process, and investigate if they are scaled-up versions of their low-mass counterparts. Aims. We selected the nearby massive star forming region IRAS 17233−3606 in order to study the kinematics and physics along the molecular outflow(s) originating from this source. Methods. We observed IRAS 17233−3606 in CO, a typical tracer of gas associated with molecular outflow, with the Submillimeter Array in the (2−1) transition, and with the APEX telescope in the higher excitation (6-5) line. Additional infrared H 2 observations were performed with the UKIRT telescope. The CO data were analysed using a LVG approach. Results. Our data resolve the previously detected molecular outflow into at least three different components, one of them with a high collimation factor (∼4), and characterised by emission at extremely high velocities (|v − v LSR | > 120 km s −1 ). The estimate of the kinematical outflow parameters are typical of massive YSOs, and in agreement with the measured bolometric luminosity of the source. The kinematic ages of the flows are in the range 10 2 −10 3 yr, and therefore point to young objects that still have not reached the main sequence.

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“…(1) Osterloh et al (1997); (2) Faúndez et al (2004); (3) Simpson & Rubin (1990); (4) Wyrowski et al (2006); (5) Neckel (1978); (6) Sandell (2000); (7) MacLeod et al (1998); (8) Reid et al (2009); (9) Goldsmith et al (1992); (10) Pandian et al (2008); (11) Cesaroni et al (2010); (12) Churchwell et al (1990); (13) Cesaroni et al (1994); (14) Watt & Mundy (1999); (15) Sato et al (2010); (16) Rudolph et al (1990).…”

Section: Introductionmentioning

confidence: 99%

Structure of evolved cluster-forming regions

Rolffs

Schilke

Wyrowski

et al. 2011

A&A

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Context. An approach towards understanding the formation of massive stars and star clusters is to study the structure of their hot core phase, an evolutionary stage where dust has been heated, but molecules have not yet been destroyed by ultraviolet radiation. These hot molecular cores are very line-rich, but the interpretation of line surveys is also hampered by poor knowledge of the physical and chemical structure. Aims. To constrain the radial structure of high-mass star-forming regions containing hot cores, we attempt to reproduce by radiative transfer modeling both the intensity and shape of a variety of molecular lines. Methods. We observed 12 hot cores with the Atacama Pathfinder EXperiment (APEX) in lines of HCN, HCO + , CO, and their isotopologues, including high-J lines and vibrationally excited HCN. We investigate how well the sources can be modeled as centrally heated spheres with a power-law density gradient, making use of the radiative transfer code RATRAN and the radial profile of the submm continuum emission, taken from the APEX Telescope Large Area Survey of the GALaxy (ATLASGAL). Results. Most of the observed lines have complicated shapes that incorporate self-absorption, asymmetries, and line wings. Vibrationally excited HCN is detected in all sources, and vibrationally excited H 13 CN in half of the sources. We are able to successfully model most features seen in the APEX data, such as the ratio of the isotopologue lines (very high optical depths), self-absorption (temperature gradient), blue asymmetries (moderate infall), vibrationally excited HCN (high inner temperatures), and H 13 CN (high HCN abundance under dense and hot conditions). Other features could not be reproduced, such as an occasional lack of self-absorption, the emission from high-J lines in the outer pixels of the CHAMP+ receiver (15 −20 from the center), the outflow wings, and the red asymmetric profiles. Conclusions. The amount of molecular gas, in particular of HCN, at very high temperatures is larger than previously thought. A complex interplay between infall and outflow motions is present. Our basic model assumptions of pure central heating and a power-law radial density distribution can serve as approximations for most sources, but are too simple to explain all observed lines. In particular, taking into account clumpiness, multiplicity of heating sources and a more complex velocity field seems to be necessary to more closely match model calculations to observations. This would require three-dimensional radiative transfer modeling of high-resolution interferometric data.

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Masers in Massive Star-forming Regions Associated with the Brightest Steep-Spectrum [ITAL]IRAS[/ITAL] Point Sources

Cited by 44 publications

References 50 publications

Trigonometric parallaxes of 6.7 GHz methanol masers

Trigonometric parallaxes of 6.7 GHz methanol masers

Extremely high velocity gas from the massive young stellar objects in IRAS 17233-3606

Structure of evolved cluster-forming regions

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