A Microjet: A Protostar’s Cry at Birth

Furuya, Ray S.; Kitamura, Yoshihisa; Wootten, Alwyn; Claussen, M. J.; Saito, Masao; Marvel, Kevin B.; Kawabe, Ryohei

doi:10.1086/312925

Cited by 62 publications

(69 citation statements)

References 18 publications

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“…Therefore, we suggest that a wind associated with an unknown energy source, which should be located very close but displaced to the southeast of R4-A (at some point along the symmetry axis of the arcuate structure), is shocking against the massive circumstellar molecular disk around HW2, producing a bow shock of water masers moving with velocities D10È30 km s~1. The R4-A structure in Cepheus A also resembles the U-shaped distribution of water masers found by Furuya et al (2000) in the star-forming region S106 (source S106 FIR), which they interpret as a "" microÈbow-shock ÏÏ created by the impact of a recently formed jet on the ambient molecular cloud.…”

Section: D28supporting

confidence: 55%

Discovery of Linear “Building Blocks” of Water Masers Shaping Linear/Arcuate Microstructures in Cepheus A

Torrelles

Patel

Gómez

et al. 2001

ApJ

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We report three epochs of VLBA water maser observations toward the radio jet Cepheus A HW2. The VLBA data show that some of the masers detected previously with the VLA unfold into unexpected and remarkable linear/arcuate "" microstructures,ÏÏ revealing, in particular three Ðlaments (R1, R2, R3) with length sizes^3È25 mas (2È18 AU) and unresolved in the perpendicular direction AU), an ([0.1 arcuate structure (R4-A) of^20 mas size (15 AU), and a curved chain of masers (R5 ; which we have previously reported) of^100 mas size (^72 AU). Some of these structures unfold into even smaller linear "" building blocks ÏÏ (down to scales of 0.4 AU) shaping the "" larger ÏÏ structures. The Ñattened appearance of these small pieces argues strongly for a shock nature. Both the morphology and the observed proper motions found in these water maser structures have allowed us to identify at least three di †erent centers of star formation activity in a region of^300 mas (200 AU) projected radius, unknown previously, and that could constitute a triple star system. We suggest that R1, R2, and R3, which are located close to the HW2 radio jet but o †set by^200 mas with respect to its axis, could originate at the shocked walls of an inner cavity excavated by the HW2 wind in the circumstellar molecular gas. The presence of a wide-angle wind associated with the central HW2 object is implied. We also propose that the arcuate structure R4-A corresponds to a bow-shock structure produced by the wind of an undetected protostar (which we predict to be located toward the southeast of R4-A,^200 mas south from HW2). Finally, the third energy source of this small region could be that one exciting the arc R5, which, as we have previously reported, is expanding and related to an unidentiÐed protostar located^600 mas south of HW2. The Ñux density of the water masers of the R5 arc excited by this unknown protostar (D500 Jy) represents an important fraction (D50%) of the total Ñux density of the maser emission in the entire Cepheus A star-forming region, suggesting that the exciting object could be a high-mass star. Furthermore, we Ðnd that the center of the circle, which Ðt the R5 arc structure for each epoch, is moving with a velocity of D6 km s~1. This could be caused by proper motions of the associated protostar because of relative orbital motions within the triple star system formed by HW2 and the energy sources of the R4-A and R5 structures.

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Section: D28supporting

confidence: 55%

Discovery of Linear “Building Blocks” of Water Masers Shaping Linear/Arcuate Microstructures in Cepheus A

Torrelles

Patel

Gómez

et al. 2001

ApJ

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“…High-resolution 1.3 cm mapping of S106 region reveals a well-defined bipolar-shaped HII region (Felli et al 1984). The optical and near-infrared dark patch at the midriff of the S106 compact HII region is found to represent a large toroid traced by 2 mm dust continuum emission (Furuya et al 2002). Similarly, the dark patch here in G333.6-0.2 may represent a large toroid; uncovering it will require high-spatial-resolution observations with appropriate molecular-line and dust tracers.…”

Section: Characteristics Of the G3336-02 Regionmentioning

confidence: 82%

Radiatively driven Rayleigh-Taylor instability candidates around a forming massive star system

Kumar¹

2013

A&A

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The formation of the highest mass stars are thought to be dominated by instabilities resulting from gravitation and radiation. Instabilities due to gravitation are commonly demonstrated by observations of fragmentation, but those due to effects of radiation have thus far not been found. Here I report on the NACO adaptive optics and mid-infrared diffraction-limited VISIR imaging data of an extemely luminous ultra-compact HII region G333.6-0.2. Two infrared sources, one bright in the near-infrared (appearing pointlike) and another in the mid-infrared (resolved with an elliptical shape) are uncovered through this data, which are located at the heart of this region. These infrared sources appear to be embedded in the waist of a bipolar-shaped nebula and UCHII region, the lobes of which are separated by a dark patch. Dense filamentary features with finger/hook morphology are found; they appear to be connected to the two bright infrared sources and the sizes of these hook features are sharply limited to <5000 AU. The observed properties of this target and a large amount of previous data obtained from the literature are compared together with the results of various numerical simulations of high-mass star formation. This comparison favours the interpretation that the finger/hook-like structures likely represent radiatively driven Rayleigh-Taylor instabilities arising in the outflow cavity of a forming high-mass binary star system.

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“…Claussen et al (1998) and Furuya et al (2000) observed respectively the HH212 and S106 FIR protostars, tracing with the H 2 O maser spots the curved bow shocks thought to travel along a jet. More recently, Moscadelli et al (2006) reported multi-epoch VLBI observations of water masers towards a sample of lowmass protostars in the Serpens region and towards RNO 15-FIR.…”

Section: Introductionmentioning

confidence: 86%

The extremely collimated bipolar H$_{\sf 2}$O jet from the NGC 1333–IRAS 4B protostar

Desmurs

Codella

Santiago-García

et al. 2009

A&A

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Context. We have performed observations of water maser emission towards a sample of low-mass protostars, in order to investigate the properties of jets associated with the earliest stages of star formation and their interaction with the surrounding medium. Aims. The main aim is to measure the absolute positions and proper motions of the H 2 O spots in order to investigate the kinematics of the region from where the jet is launched. Methods. We imaged the protostars in the nearby region NGC 1333-IRAS 4 in the water maser line at 22.2 GHz by using the VLBA in phase-reference mode at the milliarcsecond scale over four epochs, spaced by one month to measure proper motions. Results. Two protostars (A2 and B) were detected in a highly variable H 2 O maser emission, with an active phase shorter than four weeks. The H 2 O maps allow us to trace the fast jet driven by the B protostar: we observed both the red-and blue-shifted lobes very close to the protostar, ≤35 AU, moving away with projected velocities of ∼10-50 km s −1 . The comparison with the molecular outflow observed at larger scale suggests a jet precession with a 18 yr −1 rate. By measuring the positional spread of the H 2 O spots we estimate a jet width of ∼2 AU at a distance of ∼12 AU from the driving protostar.

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A Microjet: A Protostar’s Cry at Birth

Cited by 62 publications

References 18 publications

Discovery of Linear “Building Blocks” of Water Masers Shaping Linear/Arcuate Microstructures in Cepheus A

Discovery of Linear “Building Blocks” of Water Masers Shaping Linear/Arcuate Microstructures in Cepheus A

Radiatively driven Rayleigh-Taylor instability candidates around a forming massive star system

The extremely collimated bipolar H$_{\sf 2}$O jet from the NGC 1333–IRAS 4B protostar

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