Accurate H2O source positions in W3

Forster, J. R.; Welch, W. J.; Wright, M. C. H.

doi:10.1086/182493

Cited by 14 publications

(8 citation statements)

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“…On the other side of this cavity lies W3 (OH) ( l = 133.9515°, b = 1.0600°), another active high‐mass star‐forming region and also the host of OH and H 2 O masers that point towards two centres of high‐mass star formation separated by 0.07 pc (Forster, Welch & Wright 1977; Norris & Booth 1981). The molecular cloud associated with W3 (OH) is clearly elongated north–south, which is consistent with it being part of the large‐scale, compressed shell produced by the winds of the nearby IC 1804 OB association responsible for the W4 H ii shell.…”

Section: Results and Analysismentioning

confidence: 99%

The gas properties of the W3 giant molecular cloud: a HARP study

Polychroni

Moore

Allsopp

2012

Monthly Notices of the Royal Astronomical Society

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We present 12CO, 13CO and C18O J= 3 → 2 maps of the W3 giant molecular cloud (GMC) made at the James Clerk Maxwell Telescope. We combine these observations with Five College Radio Astronomy Observatory CO J= 1→0 data to produce the first map of molecular‐gas temperatures across a GMC and the most accurate determination of the mass distribution in W3 yet obtained. We measure excitation temperatures in the part of the cloud dominated by triggered star formation (the high‐density layer, HDL) of 15–30 K, while in the rest of the cloud, which is relatively unaffected by triggering (low‐density layer), the excitation temperature is generally less than 12 K. We identify a temperature gradient in the HDL which we associate with an age sequence in the embedded massive star‐forming regions. We measure the mass of the cloud to be 4.4 ± 0.4 × 105 M⊙, in agreement with previous estimates. Existing submillimetre continuum data are used to derive the fraction of gas mass in dense clumps as a function of position in the cloud. This fraction, which we interpret as a clump formation efficiency (CFE), is significantly enhanced across the HDL, probably due to the triggering. Finally, we measure the 3D rms Mach number, , as a function of position and find a correlation between and the CFE within the HDL only. This correlation is interpreted as due to feedback from the newly formed stars, and a change in its slope between the three main star‐forming regions is construed as another evolutionary effect. We conclude that triggering has affected the star formation process in the W3 GMC primarily by creating additional dense structures that can collapse into stars. Any traces of changes in CFE due to additional turbulence have since been overruled by the feedback effects of the star‐forming process itself.

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Section: Results and Analysismentioning

confidence: 99%

The gas properties of the W3 giant molecular cloud: a HARP study

Polychroni

Moore

Allsopp

2012

Monthly Notices of the Royal Astronomical Society

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“…The W3 GMC hosts two massive and active star-forming regions, W3 Main in the north and W3(OH) in the south. The W3 Main star-forming region contains objects such as H ii regions, embedded infrared sources (including the extremely luminous cluster of sources W3 IRS 5), and OH and water masers (Wynn-Williams et al 1974;Forster et al 1977;Gaume & Mutel 1987), which are in different stages of evolution.…”

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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“…In W3(OH) region, OH masers and H 2 O masers are localized within 0.1 pc (Forster et al 1977;Reid et al 1980). In addition, it is known that the OH maser is excited by an O9 star (Hirsch et al 2012) and is associated with a ultra-compact Hii region of 0.012 pc diameter.…”

Section: The W3 Giant Molecular Complexmentioning

confidence: 99%

A Kinematic Analysis of the Giant Molecular Complex W3; Possible Evidence for Cloud-Cloud Collisions that Triggered OB Star Clusters in W3 Main and W3(OH)

Yamada,

Sano,

Tachihara

et al. 2021

Preprint

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The Hii region W3 is one of the most outstanding regions of high-mass star formation. Based on a new analysis of the 12 CO(J = 2-1) data obtained at 38 ′′ resolution, we have found that 1 each of the two active regions of high-mass star formation, W3 Main and W3(OH), is associated with two clouds of different velocities separated by 3-4 km s −1 , having cloud mass of 2000-4000 M ⊙ in each. In the two regions we have found typical signatures of a cloudcloud collision, i.e.,the complementary distribution with/without a displacement between the two clouds and/or a V-shape in the position-velocity diagram. We frame a hypothesis that a cloud-cloud collision triggered the high-mass star formation in the two regions. The collision in W3 Main involves a small cloud of ∼5 pc in diameter which collided with a large cloud of 10 pc × 20 pc. The collision in W3 Main compressed the gas in the direction of the collision path toward the west over a timescale of ∼1 Myr, where the dense gas W3 core associated with ten O stars are formed. The collision also produced a cavity in the large cloud having a size similar to the small cloud. The collision in W3(OH) has a younger timescale of ∼0.5 Myr and the forming-star candidates are heavily embedded in the clouds. The results reinforce the idea that a cloud-cloud collision is an essential process in high-mass star formation by rapidly creating the initial condition of 1 g cm −2 in the natal gas.

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Accurate H2O source positions in W3

Cited by 14 publications

References 0 publications

The gas properties of the W3 giant molecular cloud: a HARP study

The gas properties of the W3 giant molecular cloud: a HARP study

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

A Kinematic Analysis of the Giant Molecular Complex W3; Possible Evidence for Cloud-Cloud Collisions that Triggered OB Star Clusters in W3 Main and W3(OH)

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