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

Kraus, Stefan; Balega, Yu. Yu.; Elitzur, Moshe; Hofmann, Karl H.; Preibisch, Thomas; Rosén, Å.; Schertl, D.; Weigelt, G.; Young, Erick T.

doi:10.1051/0004-6361:20065068

Cited by 48 publications

(61 citation statements)

References 61 publications

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“…This can be a similar case as we found in G045.47+0.05 (Paron et al 2013) and others in the literature (e.g. Weigelt et al 2006;Kraus et al 2006). Therefore, we conclude that the misaligned CO outflows and the near-IR features related to the analysed source strongly suggest a jet-precession scenario.…”

Section: Outflows Morphologysupporting

confidence: 91%

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Discovering a misaligned CO outflow related to the red MSX source G034.5964-01.0292

Paron

Ortega

Petriella

et al. 2014

A&A

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Aims. The red MSX source G034.5964-01.0292 (MSXG34), catalogued as a massive young stellar object, was observed in molecular lines with the aim of discovering and studying molecular outflows. Methods. We mapped a region of 3 × 3 centred at MSXG34 using the Atacama Submillimeter Telescope Experiment in the 12 CO J = 3-2 and HCO + J = 4-3 lines with an angular and spectral resolution of 22 and 0.11 km s −1 . Additionally, public 13 CO J = 1-0 and near-IR UKIDSS data obtained from the Galactic Ring Survey and the WFCAM Sciencie Archive were analysed. Results. We found that the 12 CO spectra towards the YSO present a self-absorption dip, as is common in star-forming regions, and spectral wings that indicate outflow activity. The HCO + was detected only towards the MSXG34 position at v LSR ∼ 14.2 km s −1 , in coincidence with the 12 CO absorption dip and approximately with the velocity of previous ammonia observations. HCO + and NH 3 are known to be enhanced in molecular outflows. When we analysed the spectral wings of the 12 CO line, we discovered misaligned red-and blue-shifted molecular outflows associated with MSXG34. The near-IR emission shows a cone-like nebulosity composed of two arc-like features related to the YSO, which might be due to a cavity cleared in the circumstellar material by a precessing jet. This can explain the misalignment in the molecular outflows. From the analysis of the 13 CO J = 1-0 data we suggest that the YSO is very likely related to a molecular clump ranging between 10 and 14 km s −1 . This suggests that MSXG34, with an associated central velocity of about 14 km s −1 , may be located in the background of this clump. Thus, the blue-shifted outflow is probably deflected by the interaction with dense gas along the line of sight. From a spectral energy distribution analysis of MSXG34 we found that its central object probably is an intermediate-mass protostar.

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Section: Outflows Morphologysupporting

confidence: 91%

“…A jet precession, either produced by tidal interactions in a binary system or due to anisotropic accretion events (e.g. Papaloizou & Terquem 1995;Kraus et al 2006), can generate misaligned molecular outflows.…”

Section: Outflows Morphologymentioning

confidence: 99%

Discovering a misaligned CO outflow related to the red MSX source G034.5964-01.0292

Paron

Ortega

Petriella

et al. 2014

A&A

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“…A mid-infrared (IR) study however questioned the edge-on disk model traced by the CH 3 OH masers, suggesting that the radio continuum emission (elongated N-S) traces an ionized wind emanating from the surface of a disk with PA of ∼30 • perpendicular to the NW-SE CO-bipolar outflow (De Buizer & Minier 2005). In an attempt to explain the different orientation of the elongated structures observed in the CH 3 OH masers and in the near-IR emission, Kraus et al (2006) proposed that the edge-on disk is driving a precessing jet. Surcis et al (2011) however pointed out that, in addition to the linear CH 3 OH maser cluster proposed to trace the edge-on Keplerian disk, there are additional maser clusters in the region within 1 , and they proposed an alternative scenario where all the observed CH 3 OH maser clusters should mark the interface between the infalling envelope and a largescale torus, having a rotation axis with the same PA (≈-45 • ) of the elongated mid-IR emission observed by De Buizer & Minier (2005).…”

Section: Introductionmentioning

confidence: 99%

“…While the individual competing models explain some properties of the system, either the ordered structure of one maser cluster (e.g., Pestalozzi et al 2004), or the global spatial distribution of all clusters (e.g., Surcis et al 2011), or the complex pattern of molecular outflows emerging from IRS 1 (Kraus et al 2006), they fail to provide a clear picture of accretion/outflow in terms of a simple disk/jet system, as expected in the context of a canonical picture of star formation. Likewise, despite the plethora of interferometric studies on the region at (sub)mmwavelengths (with angular resolutions in the range 0.…”

Section: Introductionmentioning

confidence: 99%

A multiple system of high-mass YSOs surrounded by disks in NGC 7538 IRS1

Moscadelli

Goddi

2014

A&A

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Context. It has been claimed that NGC 7538 IRS1 is a high-mass young stellar object (YSO) with 30 M , surrounded by a rotating Keplerian disk, probed by a linear distribution of methanol masers. The YSO is also powering a strong compact Hii region or ionized wind, and is driving at least one molecular outflow. The axis orientations of the different structures (ionized gas, outflow, and disk) are, however, misaligned, which has led to the different competing models proposed to explain individual structures. Aims. We investigate the 3D kinematics and dynamics of circumstellar gas with very high linear resolution, from tens to 1500 AU, with the ultimate goal of building a comprehensive dynamical model for what is considered the best high-mass accretion disk candidate around an O-type young star in the northern hemisphere. Methods. We used high-angular resolution observations of 6.7 GHz CH 3 OH masers with the EVN, NH 3 inversion lines with the JVLA B-Array, and radio continuum with the VLA A-Array. In particular, we employed four different observing epochs of EVN data at 6.7 GHz, spanning almost eight years, which enabled us to measure line-of-sight (l.o.s.) accelerations and proper motions of CH 3 OH masers, besides l.o.s. velocities and positions (as done in previous works). In addition, we imaged highly excited NH 3 inversion lines, from (6,6) to (13,13), which enabled us to probe the hottest molecular gas very close to the exciting source(s). Results. We confirm previous results that five 6.7 GHz maser clusters (labeled from "A" to "E") are distributed over a region extended N-S across ≈1500 AU, and are associated with three components of the radio continuum emission. We propose that these maser clusters identify three individual high-mass YSOs in NGC 7538 IRS1, named IRS1a (associated with clusters "B" and "C"), IRS1b (associated with cluster "A"), and IRS1c (associated with cluster "E"). We find that the 6.7 GHz masers distribute along a line, with a regular variation in V LSR with position, along the major axis of the distribution of maser cluster "A" and the combined clusters "B" + "C". A similar V LSR gradient (although shallower) is also detected in the NH 3 inversion lines. Interestingly, the variation in V LSR with projected position is not linear but quadratic for both maser clusters. We measure proper motions for 33 maser features, which have an average amplitude (4.8 ± 0.6 km s −1 ) similar to the variation in V LSR across the maser cluster, and are approximately parallel to the clusters' elongation axes. By studying the time variation in the maser spectrum, we also derive l.o.s. accelerations for 30 features, with typical amplitude of ∼10 −3 −10 −2 km s −1 yr −1 . We modeled the masers in both clusters "A" and "B" + "C" in terms of an edge-on disk in centrifugal equilibrium. Based on our modeling, masers of clusters "B" + "C" may trace a quasi-Keplerian ∼1 M , thin disk, orbiting around a high-mass YSO, IRS1a, of up to ≈25 M . This YSO dominates the bolometric luminosity of the region. The d...

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“…This large-scale mid-infrared emission may stem from the inner walls of the outflow. The jet and outflow emission is interpreted from speckle data as due to a precessing jet (Kraus et al 2006). On smaller scales, the mid-infrared emission appears elongated almost perpendicular to that outflow axis which De Buizer & Minier (2005) interprete as an inner accretion disk of approximate size of ∼900 AU.…”

Section: Introductionmentioning

confidence: 99%

The high-mass disk candidates NGC 7538IRS1 and NGC 7538S

Beuther

Linz

Henning

2012

A&A

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Context. The nature of embedded accretion disks around forming high-mass stars is one of the missing puzzle pieces for a general understanding of the formation of the most massive and luminous stars. Aims. We want to dissect the small-scale structure of the dust continuum and kinematic gas emission toward two of the most prominent high-mass disk candidates. Methods. Using the Plateau de Bure Interferometer at ∼1.36 mm wavelengths in its most extended configuration we probe the dust and gas emission at ∼0.3 , corresponding to linear resolution elements of ∼800 AU.Results. Even at that high spatial resolution NGC 7538IRS1 remains a single compact and massive gas core with extraordinarily high column densities, corresponding to visual extinctions on the order of 10 5 mag, and average densities within the central 2000 AU of ∼2.1 × 10 9 cm −3 that have not been measured before. We identify a velocity gradient across in northeast-southwest direction that is consistent with the mid-infrared emission, but we do not find a gradient that corresponds to the proposed CH 3 OH maser disk. The spectral line data toward NGC 7538IRS1 reveal strong blue-and red-shifted absorption toward the mm continuum peak position. While the blue-shifted absorption is consistent with an outflow along the line of sight, the red-shifted absorption allows us to estimate high infall rates on the order of 10 −2 M yr −1 . Although we cannot prove that the gas will be accreted in the end, the data are consistent with ongoing star formation activity in a scaled-up low-mass star formation scenario. Compared to that, NGC 7538S fragments in a hierarchical fashion into several sub-sources. While the kinematics of the main mm peak are dominated by the accompanying jet, we find rotational signatures from a secondary peak. Furthermore, strong spectral line differences exist between the sub-sources which is indicative of different evolutionary stages within the same large-scale gas clump. Conclusions. NGC 7538IRS1 is one of the most extreme high-mass disk candidates known today. The large concentration of mass into a small area combined with the high infall rates are unusual and likely allow continued accretion. While the absorption is interesting for the infall studies, higher-excited lines that do not suffer from the absorption are needed to better study the disk kinematics. In contrast to that, NGC 7538S appears as a more typical high-mass star formation region that fragments into several sources. Many of them will form low-to intermediate-mass stars. The strongest mm continuum peak is likely capable to form a high-mass star, however, likely of lower mass than NGC 7538IRS1.

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

Cited by 48 publications

References 61 publications

Discovering a misaligned CO outflow related to the red MSX source G034.5964-01.0292

Discovering a misaligned CO outflow related to the red MSX source G034.5964-01.0292

A multiple system of high-mass YSOs surrounded by disks in NGC 7538 IRS1

The high-mass disk candidates NGC 7538IRS1 and NGC 7538S

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