The standard model of low-mass star formation applied to massive stars: a multi-wavelength picture of AFGL 2591

Johnston, K. G.; Shepherd, D. S.; Robitaille, Thomas; Wood, Kenneth

doi:10.1051/0004-6361/201219657

Cited by 40 publications

(66 citation statements)

References 60 publications

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“…1 from this compact continuum emission, and in most cases the maser proper motions clearly indicate that a molecular outflow is emerging from a position consistent with that of the radio continuum. Our finding is consistent with previous observations of the few known jets from high-mass YSO, where the YSO position is coincident with compact sources detected from the radio to the near-infrared (see, e.g., the case of the massive jet in AFGL5129, Johnston et al 2013).…”

Section: Nature Of the Radio Continuumsupporting

confidence: 93%

Outflow structure within 1000 au of high-mass YSOs

Moscadelli

Sánchez-Monge

Goddi

et al. 2015

A&A

132

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Context. In high-mass (≥7 M ) star formation (SF) studies, high-angular resolution is crucial for resolving individual protostellar outflows (and possibly accretion disks) from the complex contribution of nearby (high-and low-mass) young stellar objects (YSO). Previous interferometric studies have focused mainly on single objects. Aims. A sensitive survey at high angular resolution is required to investigate outflow processes in a statistically significant sample of high-mass YSOs and on spatial scales relevant to testing theories. Methods. We selected a sample of 40 high-mass YSOs from water masers observed within the BeSSeL Survey. We investigated the 3D velocity and spatial structures of the molecular component of massive outflows at milli-arcsecond angular resolution using multi-epoch Very Long Baseline Array (VLBA) observations of 22 GHz water masers. We also characterize the ionized component of the flows using deep images of the radio continuum emission with resolutions of ∼0. 2, at 6, 13, and 22 GHz with the Jansky Very Large Array (JVLA). Results. We report the first results obtained for a subset of 11 objects from the sample. The water maser measurements provide us with a very accurate description of the molecular gas kinematics. This in turn enables us to estimate the momentum rate of individual outflows, varying in the range 10 −3 -10 0 M yr −1 km s −1 , among the highest values reported in the literature. In all the observed objects, the continuum emission at 13 and 22 GHz has a compact structure, with its position coincident with that of the water masers. The 6 GHz continuum consists of either compact components (mostly well aligned with the 13 and/or 22 GHz sources) or extended emission (either highly elongated or approximately spherical), which can be offset by up to a few arcseconds from the water masers. The unresolved continuum emission associated with the water masers likely points to the YSO location. The comparison of the radio continuum morphology to the maser spatial and 3D velocity distribution shows that five out of eleven high-mass YSOs emit a collimated outflow, with a flow semi-opening angle in the range 10• -30• . The remaining six sources present a more complicated relationship between the geometry of the radio continuum and water maser velocity pattern; therefore, no firm conclusions can be drawn regarding their outflow structure. In two sources, the 6 GHz continuum emission shows a highly elongated structure with a negative spectral index down to −1.2. We interpret this finding in terms of synchrotron emission from relativistic electrons accelerated in strong shocks, which indicates that non-thermal continuum emission could be common in high-mass protostellar jets. The Lyman continua derived from bolometric luminosities always exceed those obtained from the radio luminosities. Conclusions. These first results suggest that collimated outflows or jets can be common in high-mass YSOs and, in a couple of cases, provide hints that magnetic fields could be important in driving ...

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Section: Nature Of the Radio Continuumsupporting

confidence: 93%

Outflow structure within 1000 au of high-mass YSOs

Moscadelli

Sánchez-Monge

Goddi

et al. 2015

A&A

132

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“…In the past years, the formation of high-mass stars has been at the center of numerous studies, both observational and theoretical. The observations reveal that the structure of massive protostars is probably similar to that of their less massive counterpart (e.g., Tang et al 2009;Keto & Zhang 2010;Johnston et al 2013), and the theoretical simulations match the observations as long as the magnetic field is taken into consideration (e.g., Peters et al 2011;Seifried et al 2012a;Myers et al 2013).…”

Section: Introductionmentioning

confidence: 63%

The magnetic field at milliarcsecond resolution around IRAS 20126+4104

Surcis

Vlemmings

Langevelde

et al. 2014

A&A

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Context. IRAS 20126+4104 is a well studied B0.5 protostar that is surrounded by a ∼1000 au Keplerian disk and is where a largescale outflow originates. Both 6.7-GHz CH 3 OH masers and 22-GHz H 2 O masers have been detected toward this young stellar object. The CH 3 OH masers trace the Keplerian disk, while the H 2 O masers are associated with the surface of the conical jet. Recently, observations of dust polarized emission (350 μm) at an angular resolution of 9 arcsec (∼15 000 au) have revealed an S -shaped morphology of the magnetic field around IRAS 20126+4104. Aims. The observations of polarized maser emissions at milliarcsecond resolution (∼20 au) can make a crucial contribution to understanding the orientation of the magnetic field close to IRAS 20126+4104. This will allow us to determine whether the magnetic field morphology changes from arcsecond resolution to milliarcsecond resolution. Methods. The European VLBI Network was used to measure the linear polarization and the Zeeman splitting of the 6.7-GHz CH 3 OH masers toward IRAS 20126+4104. The NRAO Very Long Baseline Array was used to measure the linear polarization and the Zeeman splitting of the 22-GHz H 2 O masers toward the same region. Results. We detected 26 CH 3 OH masers and 5 H 2 O masers at high angular resolution. Linear polarization emission was observed toward three CH 3 OH masers and toward one H 2 O maser. Significant Zeeman splitting was measured in one CH 3 OH maser (ΔV Z = −9.2 ± 1.4 m s −1 ). No significant (5σ) magnetic field strength was measured using the H 2 O masers. We found that in IRAS 20126+4104 the rotational energy is less than the magnetic energy.

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“…Since we only detect the SW lobe of the jet emission at Q-band, we multiply the mechanical properties of the radio jet by a factor of 2, to compare with the large-scale bipolar outflow. Asymmetric radio continuum emission is frequently observed around YSOs of different masses (e.g., Hofner et al 2007;Johnston et al 2013), and may be due to density inhomogeneity of the protostellar environment. Figure 2 allows one to trace backward the outflow emission, down to its driving source, over more than two order of magnitude of distance from the HMC center (0.2 pc-500 AU).…”

Section: Discussionmentioning

confidence: 99%

Momentum-driven outflow emission from an O-type YSO

Sanna¹,

Moscadelli²,

Cesaroni³

et al. 2016

A&A

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Aims. We want to study the physical properties of the ionized jet emission in the vicinity of an O-type young stellar object (YSO), and estimate how efficient is the transfer of energy and momentum from small-to large-scale outflows. Methods. We conducted Karl G. Jansky Very Large Array (VLA) observations, at both 22 and 45 GHz, of the compact and faint radio continuum emission in the high-mass star-forming region G023.01−00.41, with an angular resolution between 0 . 3 and 0 . 1, and a thermal rms of the order of 10 µJy beam −1 . Results. We discovered a collimated thermal (bremsstrahlung) jet emission, with a radio luminosity (L rad ) of 24 mJy kpc 2 at 45 GHz, in the inner 1000 AU from an O-type YSO. The radio thermal jet has an opening angle of 44• and brings a momentum rate of 8×10 −3 M yr −1 km s −1 . By combining the new data with previous observations of the molecular outflow and water maser shocks, we can trace the outflow emission from its driving source through the molecular clump, across more than two order of magnitude in length (500 AU-0.2 pc). We find that the momentum-transfer efficiency, between the inner jet emission and the extended outflow of entrained ambient gas, is near unity. This result suggests that the large-scale flow is swept-up by the mechanical force of the radio jet emission, which originates in the inner 1000 AU from the high-mass YSO.

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The standard model of low-mass star formation applied to massive stars: a multi-wavelength picture of AFGL 2591

Cited by 40 publications

References 60 publications

Outflow structure within 1000 au of high-mass YSOs

Outflow structure within 1000 au of high-mass YSOs

The magnetic field at milliarcsecond resolution around IRAS 20126+4104

Momentum-driven outflow emission from an O-type YSO

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