Kinematics and Distance of Water Masers in W3 IRS 5

Imai, Hiroshi; Kameya, Osamu; Sasao, Tetsuo; Miyoshi, Makoto; Deguchi, Shuji; Horiuchi, S.; Asaki, Y.

doi:10.1086/309165

Cited by 91 publications

(122 citation statements)

References 42 publications

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“…W3 IRS5 is a massive star-forming region located in the Perseus arm at a distance of 1.83 ± 0.14 kpc (Imai et al 2000) with a total luminosity of 2 × 10 5 L (Campbell et al 1995). A cluster of hypercompact (<240 AU) H II regions are found from high-resolution cm-wavelength observations (Claussen et al 1994;Wilson et al 2003;van der Tak et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Dense molecular cocoons in the massive protocluster W3 IRS5: a test case for models of massive star formation

Wang

Bourke

Hogerheijde

et al. 2013

A&A

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Context. Two competing models describe the formation of massive stars in objects like the Orion Trapezium. In the turbulent core accretion model, the resulting stellar masses are directly related to the mass distribution of the cloud condensations. In the competitive accretion model, the gravitational potential of the protocluster captures gas from the surrounding cloud for which the individual cluster members compete. Aims. With high resolution submillimeter observations of the structure, kinematics, and chemistry of the proto-Trapezium cluster W3 IRS5, we aim to determine which mode of star formation dominates. Methods. We present 354 GHz Submillimeter Array observations at resolutions of 1 -3 (1800-5400 AU) of W3 IRS5. The dust continuum traces the compact source structure and masses of the individual cores, while molecular lines of CS, SO, SO 2 , HCN, H 2 CS, HNCO, and CH 3 OH (and isotopologues) reveal the gas kinematics, density, and temperature. Results. The observations show five emission peaks (SMM1-5). SMM1 and SMM2 contain massive embedded stars (∼20 M ); SMM3-5 are starless or contain low-mass stars (<8 M ). The inferred densities are high, ≥10 7 cm −3 , but the core masses are small, 0.2−0.6 M . The detected molecular emission reveals four different chemical zones. Abundant (X ∼ few 10 −7 to 10 −6 ) SO and SO 2 are associated with SMM1 and SMM2, indicating active sulfur chemistry. A low abundance (5 × 10 −8 ) of CH 3 OH concentrated on SMM3/4 suggest the presence of a hot core that is only just turning on, possibly by external feedback from SMM1/2. The gas kinematics are complex with contributions from a near pole-on outflow traced by CS, SO, and HCN; rotation in SO 2 , and a jet in vibrationally excited HCN. Conclusions. The proto-Trapezium cluster W3 IRS5 is an ideal test case to discriminate between models of massive star formation. Either the massive stars accrete locally from their local cores; in this case the small core masses imply that W3 IRS5 is at the very end stages (1000 yr) of infall and accretion, or the stars are accreting from the global collapse of a massive, cluster forming core. We find that the observed masses, densities and line widths observed toward W3 IRS 5 and the surrounding cluster forming core are consistent with the competitive accretion of gas at rates ofṀ ∼10 −4 M yr −1 by the massive young forming stars. Future mapping of the gas kinematics from large to small scales will determine whether large-scale gas inflow occurs and how the cluster members compete to accrete this material.

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Section: Introductionmentioning

confidence: 99%

Dense molecular cocoons in the massive protocluster W3 IRS5: a test case for models of massive star formation

Wang

Bourke

Hogerheijde

et al. 2013

A&A

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“…Based on these predictions, the "Radiation Diagnostics" observations started with deep integrations of a large number of hydrides that was to be followed by a survey of a few species in many sources of various ages and masses. Here we present exploratory observations towards W3 IRS5, a nearby region (1.83 kpc, Imai et al 2000) of high-mass star formation, moving at -38.4 km s −1 in the local standard of rest (LSR). W3 IRS5 resembles the Trapezium cluster in Orion but is considerably younger.…”

Section: Introductionmentioning

confidence: 99%

Hydrides in young stellar objects: Radiation tracers in a protostar-disk-outflow system

Benz¹,

Bruderer²,

Dishoeck

et al. 2010

A&A

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Context. Hydrides of the most abundant heavier elements are fundamental molecules in cosmic chemistry. Some of them trace gas irradiated by UV or X-rays. Aims. We explore the abundances of major hydrides in W3 IRS5, a prototypical region of high-mass star formation. Methods. W3 IRS5 was observed by HIFI on the Herschel Space Observatory with deep integration ( 2500 s) in 8 spectral regions. Results. The target lines including CH, NH, H 3 O + , and the new molecules SH + , H 2 O + , and OH + are detected. The H 2 O + and OH + J = 1−0 lines are found mostly in absorption, but also appear to exhibit weak emission (P-Cyg-like). Emission requires high density, thus originates most likely near the protostar. This is corroborated by the absence of line shifts relative to the young stellar object (YSO). In addition, H 2 O + and OH + also contain strong absorption components at a velocity shifted relative to W3 IRS5, which are attributed to foreground clouds. Conclusions. The molecular column densities derived from observations correlate well with the predictions of a model that assumes the main emission region is in outflow walls, heated and irradiated by protostellar UV radiation.

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“…The W3 giant molecular cloud (GMC) complex is located in the Perseus spiral arm at a distance of 1:83 AE 0:14 kpc from the Sun (Imai et al 2000). The W3 GMC hosts two massive and active star-forming regions, W3 Main in the north and W3(OH) in the south.…”

Section: Introductionmentioning

confidence: 99%

Deep Near‐Infrared Observations of the W3 Main Star‐forming Region

Ojha

Tamura

Nakajima

et al. 2004

ApJ

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We present a deep JHK s -band imaging survey of the W3 Main star-forming region, using the near-infrared camera SIRIUS mounted on the University of Hawaii 2.2 m telescope. The near-infrared survey covers an area of $24 arcmin 2 with 10 limiting magnitudes of $19.0, 18.1, and 17.3 in the J, H, and K s bands, respectively. We construct JHK color-color and J versus JÀH and K versus HÀK color-magnitude diagrams to identify young stellar objects and estimate their masses. Based on these color-color and color-magnitude diagrams, a rich population of young stellar objects is identified that is associated with the W3 Main region. A large number of previously unreported red sources (HÀK > 2) have also been detected around W3 Main. We argue that these red stars are most probably pre-main-sequence stars with intrinsic color excesses. We find that the slope of the K s -band luminosity function (KLF) of W3 Main is lower than the typical values reported for young embedded clusters. The derived slope of the KLF is the same as that found in 1996 by Megeath and coworkers, from which analysis indicated that the W3 Main region has an age in the range of 0.3-1 Myr. Based on the comparison between models of pre-main-sequence stars and the observed color-magnitude diagram, we find that the stellar population in W3 Main is primarily composed of low-mass pre-main-sequence stars. We also report the detection of isolated young stars with large infrared excesses that are most probably in their earliest evolutionary phases.

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Kinematics and Distance of Water Masers in W3 IRS 5

Cited by 91 publications

References 42 publications

Dense molecular cocoons in the massive protocluster W3 IRS5: a test case for models of massive star formation

Dense molecular cocoons in the massive protocluster W3 IRS5: a test case for models of massive star formation

Hydrides in young stellar objects: Radiation tracers in a protostar-disk-outflow system

Deep Near‐Infrared Observations of the W3 Main Star‐forming Region

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