Massive star outflows

Shepherd, D. S.

doi:10.1017/s174392130500459x

Cited by 22 publications

(12 citation statements)

References 53 publications

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“…Since only shock excited gas has been included this is a lower limit. This figure for the outflow rate is comparable to estimates given in Shepherd (2005) for stars of the luminosity associated with source I ( 10 L ). This estimate also agrees with the estimated mass loss of 10 −2 -10 −4 M yr −1 given in Genzel et al (1981).…”

Section: The Outflow Zone Region Bsupporting

confidence: 87%

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Observations of spatial and velocity structure in the Orion molecular cloud

Nissen¹,

Gustafsson²,

Lemaire

et al. 2007

A&A

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Observations are reported of H 2 IR emission in the S(1) v = 1−0 line at 2.121 µm in the Orion Molecular Cloud, OMC1, using the GriF instrument on the Canada-France-Hawaii Telescope. GriF uses a combination of adaptive optics and Fabry-Perot interferometry, yielding a spatial resolution of 0.15 to 0.18 and velocity discrimination as high as 1 km s −1 . 193 bright H 2 emission regions can be identified in OMC1. The general characteristics of these features are described in terms of radial velocities, brightness and spatial displacement of maxima of velocity and brightness, the latter to yield the orientation of flows in the plane of the sky. Strong spatial correlation between velocity and bright H 2 emission is found and serves to identify many features as shocks. Important results are: (i) velocities of the excited gas illustrate the presence of a zone to the south of BN-IRc2 and Peak 1, and the west of Peak 2, where there is a powerful blue-shifted outflow with an average velocity of −18 km s −1 . This is shown to be the NIR counterpart of an outflow previously identified in the radio, originating from either source I or source n. (ii) There is a band of weak radial velocity features (<5 km s −1 ) in Peak 1. (iii) A small proportion of the flows may represent sites of low mass star formation and one region shows evidence of multiple flows which may indicate multiple low mass star formation within OMC1.

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Section: The Outflow Zone Region Bsupporting

confidence: 87%

“…These values are typical of an early-type B-star (Shepherd 2005). The much debated issue of the origin of large scale outflows in OMC1, see for example Shuping et al (2004), has recently achieved a new perspective with high spatial resolution (0.3-0.5 ) IR measurements in Shuping et al (2004) and Greenhill et al (2004a).…”

Section: The Outflow Zone Region Bmentioning

confidence: 96%

Observations of spatial and velocity structure in the Orion molecular cloud

Nissen¹,

Gustafsson²,

Lemaire

et al. 2007

A&A

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“…The observed widening in HMPO outflows might be due to selection effects (Shepherd 2005) and/or precession of a collimated jet. The large precession angles reported for IRAS 20126+4104 (Shepherd et al 2000), S140 IRS1 (Weigelt et al 2002), IRAS 23151+5912 (Weigelt et al 2005), and now NGC 7538 IRS1 (this paper) might point towards a rather dramatic precession mechanism, maybe the presence of very close, high-mass companions on non-coplanar orbits.…”

Section: Discussionmentioning

confidence: 96%

Outflows from the high-mass protostars NGC 7538 IRS1/2 observed with bispectrum speckle interferometry

Kraus¹,

Balega

Elitzur

et al. 2006

A&A

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Context. NGC 7538 IRS1 is a high-mass (30 M ) protostar with a CO outflow, an associated ultracompact H  region, and a linear methanol maser structure, which might trace a Keplerian-rotating circumstellar disk. The directions of the various associated axes are misaligned with each other. Aims. We investigate the near-infrared morphology of the source to clarify the relations among the various axes. Methods. K -band bispectrum speckle interferometry was performed at two 6-meter-class telescopes -the BTA 6 m telescope and the 6.5 m MMT. Complementary IRAC images from the Spitzer Space Telescope Archive were used to relate the structures detected with the outflow at larger scales. Results. High-dynamic range images show fan-shaped outflow structure in which we detect 18 stars and several blobs of diffuse emission. We interpret the misalignment of various outflow axes in the context of a disk precession model, including numerical hydrodynamic simulations of the molecular emission. The precession period is ∼280 years and its half-opening angle is ∼40• . A possible triggering mechanism is non-coplanar tidal interaction of an (undiscovered) close companion with the circumbinary protostellar disk. Our observations resolve the nearby massive protostar NGC 7538 IRS2 as a close binary with separation of 195 mas. We find indications for shock interaction between the outflow activities in IRS1 and IRS2. Finally, we find prominent sites of star formation at the interface between two bubble-like structures in NGC 7538, suggestive of a triggered star formation scenario. Conclusions. Indications of outflow precession have been discovered to date in a number of massive protostars, all with large precession angles (∼20-45• ). This might explain the difference between the outflow widths in low-and high-mass stars and add support to a common collimation mechanism.

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“…During the last few decades, many efforts have been devoted to studying and describing the physical properties of embedded low-mass protostars and their molecular outflows (e.g., Bachiller 1996;Richer et al 2000). In recent years, high-mass molecular outflows have also been studied in detail, and many surveys have been carried out towards massive star-forming regions to achieve a more accurate picture of their morphology and properties (e.g., Shepherd & Churchwell 1996a,b;Zhang et al 2001;Shepherd 2005). In recent years, there has been a growing interest in the young stellar objects (YSOs) located at the lower and the higher ends of the stellar mass spectrum.…”

Section: Introductionmentioning

confidence: 99%

On the nature of outflows in intermediate-mass protostars: a case study of IRAS 20050+2720

Beltrán

Estalella

Girart

et al. 2008

A&A

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Context. This is the third in a series of papers devoted to studying intermediate-mass molecular outflows and their powering sources in detail and with high-angular resolution. Aims. This paper studies the intermediate-mass YSO IRAS 20050+2720 and its molecular outflow and puts the results of this and the previous studied sources in the context of intermediate-mass star formation. Methods. We carried out VLA observations of the 7 mm continuum emission and OVRO observations of the 2.7 mm continuum emission, CO (J = 1 → 0), C 18 O (J = 1 → 0), and HC 3 N (J = 12 → 11) to map the core towards IRAS 20050+2720. The highangular resolution of the observations allowed us to derive the properties of the dust emission, the molecular outflow, and the dense protostellar envelope. By adding this source to the sample of intermediate-mass protostars with outflows, we compared their properties and evolution with those of lower mass counterparts. Results. The 2.7 mm continuum emission has been resolved into three sources, labeled OVRO 1, OVRO 2, and OVRO 3. Two of them, OVRO 1 and OVRO 2, have also been detected at 7 mm. OVRO 3, which is located close to the C 18 O emission peak, could be associated with IRAS 20050+2720. The mass of the sources, estimated from the dust continuum emission, is 6.5 M for OVRO 1, 1.8 M for OVRO 2, and 1.3 M for OVRO 3. The CO (J = 1 → 0) emission traces two bipolar outflows within the OVRO field of view, a roughly east-west bipolar outflow, labeled A, driven by the intermediate-mass source OVRO 1, and a northeast-southwest bipolar outflow, labeled B, probably powered by a YSO engulfed in the circumstellar envelope surrounding OVRO 1. Conclusions. The multiplicity of sources observed towards IRAS 20050+2720 appears to be typical of intermediate-mass protostars, which form in dense clustered environments. In some cases, as for example IRAS 20050+2720, intermediate-mass protostars would start forming after a first generation of low-mass stars has completed their main accretion phase. The properties of intermediate-mass protostars and their outflows are not significantly different from those of low-mass stars. Although intermediate-mass outflows are intrinsically more energetic than those driven by low-mass YSOs, they do not show intrinsically more complex morphologies when observed at high angular resolution. Known intermediate-mass protostars do not form a homogeneous group. Some objects are likely in an earlier evolutionary stage as suggested by the infrared emission and the outflow properties.

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Massive star outflows

Cited by 22 publications

References 53 publications

Observations of spatial and velocity structure in the Orion molecular cloud

Observations of spatial and velocity structure in the Orion molecular cloud

Outflows from the high-mass protostars NGC 7538 IRS1/2 observed with bispectrum speckle interferometry

On the nature of outflows in intermediate-mass protostars: a case study of IRAS 20050+2720

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