Properties of the UCHII region G25.4NW and its associated molecular cloud

Ai, Mei; Zhu, Meiping; Xiao, Li; Su, H.

doi:10.1088/1674-4527/13/8/005

Cited by 9 publications

(11 citation statements)

References 18 publications

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“…Furthermore, the 24 µm emission is enclosed by the 8.0 µm emission. The G25.4NW region lies in the direction of the W42 complex, but is not associated with it, as can be seen from its very different velocity (Ai et al 2013) which indicates a very different distance. Therefore, the results of G25.4NW region are not discussed in this work.…”

Section: 1mentioning

confidence: 99%

“…The 13 CO profile along the line of sight to W42 shows two well-separated velocity components; one at 58-69 km s −1 that is physically associated with W42, and the other at 88-109 km s −1 , that is associated with G25.4NW (e.g. Ai et al 2013) located at the northwest edge of the extended bipolar nebula (e.g., Deharveng et al 2010). Different velocity values suggest that these regions are not physically associated and are not part of the same star-forming complex (e.g., Ai et al 2013).…”

Section: Introductionmentioning

confidence: 99%

“…Ai et al 2013) located at the northwest edge of the extended bipolar nebula (e.g., Deharveng et al 2010). Different velocity values suggest that these regions are not physically associated and are not part of the same star-forming complex (e.g., Ai et al 2013). Using the C ii and 3 He radio recombination lines, Quireza et al (2006) measured the velocity of the ionized gas to be ∼59.6 km s −1 in W42.…”

Section: Introductionmentioning

confidence: 99%

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The Physical Environment of the Massive Star-Forming Region W42

Dewangan

Luna

Ojha

et al. 2015

ApJ

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We present an analysis of multi-wavelength observations from various datasets and Galactic plane surveys to study the star formation process in the W42 complex. A bipolar appearance of W42 complex is evident due to the ionizing feedback from the O5-O6 type star in a medium that is highly inhomogeneous. The VLT/NACO adaptive-optics K and L images (resolutions ∼0. 2-0. 1) resolved this ionizing source into multiple point-like sources below ∼5000 AU scale. The position angle ∼15 • of W42 molecular cloud is consistent with the H-band starlight mean polarization angle which in turn is close to the Galactic magnetic field, suggesting the influence of Galactic field on the evolution of the W42 molecular cloud. Herschel sub-millimeter data analysis reveals three clumps located along the waist axis of the bipolar nebula, with the peak column densities of ∼3-5 × 10 22 cm −2 corresponding to visual extinctions of A V ∼32-53.5 mag. The Herschel temperature map traces a temperature gradient in W42, revealing regions of 20 K, 25 K, and 30-36 K. Herschel maps reveal embedded filaments (length ∼1-3 pc) which appear to be radially pointed to the denser clump associated with the O5-O6 star, forming a hub-filament system. 512 candidate young stellar objects (YSOs) are identified in the complex, ∼40% of which are present in clusters distributed mainly within the molecular cloud including the Herschel filaments. Our datasets suggest that the YSO clusters including the massive stars are located at the junction of the filaments, similar to those seen in Rosette Molecular Cloud.

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Section: 1mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Physical Environment of the Massive Star-Forming Region W42

Dewangan

Luna

Ojha

et al. 2015

ApJ

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“…The clump G25.38 is located at a near kinematic distance of 5.60 kpc (Anderson & Bania 2009;Ai et al 2013;Urquhart et al 2013). In Figs.…”

Section: C7 G2538mentioning

confidence: 99%

Probing the initial conditions of high-mass star formation

Zhang

Csengeri

Wyrowski

et al. 2019

A&A

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Context. Fragmentation and feedback are two important processes during the early phases of star formation. Aims. Massive clumps tend to fragment into clusters of cores and condensations, some of which form high-mass stars. In this work, we study the structure of massive clumps at different scales, analyze the fragmentation process, and investigate the possibility that star formation is triggered by nearby H ii regions. Methods. We present a high angular resolution study of a sample of massive proto-cluster clumps G18.17, G18.21, G23.97N, G23.98, G23.44, G23.97S, G25.38, and G25.71. Combining infrared data at 4.5, 8.0, 24, and 70 μm, we use a few arcsecond resolution, radiometer and millimeter inteferometric data taken at 1.3 cm, 3.5 mm, 1.3 mm, and 870 μm to study their fragmentation and evolution. Our sample is unique in the sense that all the clumps have neighboring H ii regions. Taking advantage of that, we tested triggered star formation using a novel method where we study the alignment of the center of mass traced by dust emission at multiple scales. Results. The eight massive clumps, identified based on single-dish observations, have masses ranging from 228 to 2279 M⊙ within an effective radius of Reff ~ 0.5 pc. We detect compact structures towards six out of the eight clumps. The brightest compact structures within infrared bright clumps are typically associated with embedded compact radio continuum sources. The smaller scale structures of Reff ~ 0.02 pc observed within each clump are mostly gravitationally bound and massive enough to form at least a B3-B0 type star. Many condensations have masses larger than 8 M⊙ at a small scale of Reff ~ 0.02 pc. We find that the two infrared quiet clumps with the lowest mass and lowest surface density with <300 M⊙ do not host any compact sources, calling into question their ability to form high-mass stars. Although the clumps are mostly infrared quiet, the dynamical movements are active at clump scale (~1 pc). Conclusions. We studied the spatial distribution of the gas conditions detected at different scales. For some sources we find hints of external triggering, whereas for others we find no significant pattern that indicates triggering is dynamically unimportant. This probably indicates that the different clumps go through different evolutionary paths. In this respect, studies with larger samples are highly desired.

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“…The clump G23.97S is located at a near kinematic distance of 4.70 kpc (Wienen et al 2012;Reid et al 2009). In The clump G25.38 is located at a near kinematic distance of 5.60 kpc (Anderson & Bania 2009;Ai et al 2013;Urquhart et al 2013). In Figure D.6(a)(c), there is a very vague infrared point source within the 1.3 mm primary beam of the PdBI.…”

Section: Appendix D: Other Figures and Tablesmentioning

confidence: 99%

Probing the initial conditions of high-mass star formation. III. Fragmentation and triggered star formation

Zhang,

Csengeri,

Wyrowski

et al. 2019

Preprint

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Context. Fragmentation and feedback are two important processes during the early phases of star formation. Aims. Massive clumps tend to fragment into clusters of cores and condensations, some of which form high-mass stars. In this work, we study the structure of massive clumps at different scales, analyze the fragmentation process, and investigate the possibility that star formation is triggered by nearby H II regions. Methods. We present a high angular resolution study of a sample of massive proto-cluster clumps G18.17, G18.21, G23. 97N, G23.98, G23.44, G23.97S, G25.38, and G25.71. Combining infrared data at 4.5, 8.0, 24, and 70 µm, we use few-arcsecond resolution radioand millimeter interferometric data taken at 1.3 cm, 3.5 mm, 1.3 mm, and 870 µm to study their fragmentation and evolution. Our sample is unique in the sense that all the clumps have neighboring H II regions. Taking advantage of that, we test triggered star formation using a novel method where we study the alignment of the centres of mass traced by dust emission at multiple scales.Results. The eight massive clumps, identified based on single dish observations, have masses ranging from 228 to 2279 M within an effective radius of R eff ∼ 0.5 pc. We detect compact structures towards six out of the eight clumps. The brightest compact structures within infrared bright clumps are typically associated with embedded compact radio continuum sources. The smaller scale structures of R eff ∼ 0.02 pc observed within each clump are mostly gravitationally bound and massive enough to form at least a B3-B0 type star. Many condensations have masses larger than 8 M at small scale of R eff ∼ 0.02 pc. We find that the two lowest mass and lowest surface density infrared quiet clumps with < 300 M do not host any compact sources, calling into question their ability to form high-mass stars. Although the clumps are mostly infrared quiet, the dynamical movements are active at clump scale (∼ 1 pc). Conclusions. We studied the spatial distribution of the gas conditions detected at different scales. For some sources we find hints of external triggering, whereas for others we find no significant pattern that indicates triggering is dynamically unimportant. This probably indicates that the different clumps go through different evolutionary paths. In this respect, studies with larger samples are highly desired.

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Properties of the UCHII region G25.4NW and its associated molecular cloud

Cited by 9 publications

References 18 publications

The Physical Environment of the Massive Star-Forming Region W42

The Physical Environment of the Massive Star-Forming Region W42

Probing the initial conditions of high-mass star formation

Probing the initial conditions of high-mass star formation. III. Fragmentation and triggered star formation

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