High-mass Starless Clumps in the Inner Galactic Plane: The Sample and Dust Properties

Yuan, Jinghua; Wu, Yuefang; Ellingsen, S. P.; Evans, Neal J.; Henkel, C.; Wang, Ke; Liu, Hongli; Liu, Tie; Li, Jin-Zeng; Zavagno, A.

doi:10.3847/1538-4365/aa7204

Cited by 41 publications

(62 citation statements)

References 78 publications

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“…The unweighted average kinetic temperatures T kin are 52 ± 6, 73 ± 4, 81 ± 6, and 110 ± 8 K in 70w, IRw, IRb, and H II regions, respectively (see Tab. 3). From this it is clear that the averaged gas kinetic temperature increases with the evolutionary stage, which confirms the trends measured with CO, NH 3 , CH 3 CN, CH 3 CCH, CH 3 OH, and dust emission in our sample and in other massive star-forming clumps (Giannetti et al 2014Guzmán et al 2015;Molinari et al 2016;He et al 2016;Yu & Xu 2016;König et al 2017;Yuan et al 2017;Elia et al 2017). This indicates that the gas temperature probed by para-H 2 CO is related to the evolution of the clumps.…”

Section: Gas Temperature and Clump Evolutionsupporting

confidence: 89%

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ATLASGAL-selected massive clumps in the inner Galaxy

Tang

Henkel

Wyrowski

et al. 2018

A&A

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Context. Formaldehyde (H 2 CO) is a reliable tracer to accurately measure the physical parameters of dense gas in star-forming regions. Aims. We aim to determine directly the kinetic temperature and spatial density with formaldehyde for the ∼100 brightest ATLASGALselected clumps (the TOP100 sample) at 870 µm representing various evolutionary stages of high-mass star formation. Methods. Ten transitions (J = 3-2 and 4-3) of ortho-and para-H 2 CO near 211, 218, 225, and 291 GHz were observed with the Atacama Pathfinder EXperiment (APEX) 12 m telescope. Results. Using non-LTE models with RADEX, we derived the gas kinetic temperature and spatial density with the measured para-H 2 CO 3 21 -2 20 /3 03 -2 02 , 4 22 -3 21 /4 04 -3 03 , and 4 04 -3 03 /3 03 -2 02 ratios. The gas kinetic temperatures derived from the para-H 2 CO 3 21 -2 20 /3 03 -2 02 and 4 22 -3 21 /4 04 -3 03 line ratios are high, ranging from 43 to >300 K with an unweighted average of 91 ± 4 K. Deduced T kin values from the J = 3-2 and 4-3 transitions are similar. Spatial densities of the gas derived from the para-H 2 CO 4 04 -3 03 /3 03 -2 02 line ratios yield 0.6-8.3 × 10 6 cm −3 with an unweighted average of 1.5 (±0.1) × 10 6 cm −3 . A comparison of kinetic temperatures derived from para-H 2 CO, NH 3 , and dust emission indicates that para-H 2 CO traces a distinctly higher temperature than the NH 3 (2,2)/(1,1) transitions and the dust, tracing heated gas more directly associated with the star formation process. The H 2 CO line widths are found to be correlated with bolometric luminosity and increase with the evolutionary stage of the clumps, which suggests that higher luminosities tend to be associated with a more turbulent molecular medium. It seems that the spatial densities measured with H 2 CO do not vary significantly with the evolutionary stage of the clumps. However, averaged gas kinetic temperatures derived from H 2 CO increase with time through the evolution of the clumps. The high temperature of the gas traced by H 2 CO may be mainly caused by radiation from embedded young massive stars and the interaction of outflows with the ambient medium. For L bol /M clump 10 L ⊙ /M ⊙ , we find a rough correlation between gas kinetic temperature and this ratio, which is indicative of the evolutionary stage of the individual clumps. The strong relationship between H 2 CO line luminosities and clump masses is apparently linear during the late evolutionary stages of the clumps, indicating that L H 2 CO does reliably trace the mass of warm dense molecular gas. In our massive clumps H 2 CO line luminosities are approximately linearly correlated with bolometric luminosities over about four orders of magnitude in L bol , which suggests that the mass of dense molecular gas traced by the H 2 CO line luminosity is well correlated with star formation.

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Section: Gas Temperature and Clump Evolutionsupporting

confidence: 89%

“…We assumed a cloud size of ∼1 pc (e.g. Dunham et al 2010Dunham et al , 2011Rosolowsky et al 2010;Urquhart et al 2014;He et al 2015;Wienen et al 2015;König et al 2017;Yuan et al 2017), a velocity gradient dv/dr = 1 km s…”

Section: Non-thermal Velocity Dispersion-temperature Relationmentioning

confidence: 99%

ATLASGAL-selected massive clumps in the inner Galaxy

Tang

Henkel

Wyrowski

et al. 2018

A&A

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“…Clump "c8" is particularly interesting because it is not visible at Herschel/PACS 70 µm and 160 µm bands as well as Spitzer/MIPS 24 µm band, indicating that it is very cold and maybe starless. The physical parameters (e.g., mass, density, size) of "c8" are similar to other Galactic massive starless clumps discovered in large surveys (e.g., Guzmán et al 2015;Traficante et al 2015;Contreras et al 2017;Yuan et al 2017). As noted earlier (Section 4.2.1), the magnetic field surrounding "c8" is pinched, hinting at gas inflow along the filament.…”

Section: Gravitational Stability Of Dense Clumpssupporting

confidence: 69%

A Holistic Perspective on the Dynamics of G035.39-00.33: The Interplay between Gas and Magnetic Fields

Liu

Juvela

et al. 2018

ApJ

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Magnetic field is one of the key agents that play a crucial role in shaping molecular clouds and regulating star formation, yet the complete information on the magnetic field is not well constrained due to the limitations in observations. We study the magnetic field in the massive infrared dark cloud G035.39-00.33 from dust continuum polarization observations at 850 µm with SCUBA-2/POL-2 at JCMT for the first time. The magnetic field tends to be perpendicular to the densest part of the main filament (F M ), whereas it has a less defined relative orientation in the rest of the structure, where it tends to be parallel to some diffuse regions. A mean plane-of-the-sky magnetic field strength of ∼50 µG for F M is obtained using Davis-Chandrasekhar-Fermi method. Based on 13 CO (1-0) line observations, we suggest a formation scenario of F M due to large-scale (∼10 pc) cloud-cloud collision. Using additional NH 3 line data, we estimate that F M will be gravitationally unstable if it is only supported by thermal pressure and turbulence. The northern part of F M , however, can be stabilized by a modest additional support from the local magnetic field. The middle and southern parts of F M are likely unstable even if the magnetic field support is taken into account. We claim that the clumps in F M may be supported by turbulence and magnetic fields against gravitational collapse. Finally, we identified for the first time a massive (∼200 M ), collapsing starless clump candidate, "c8", in G035.39-00.33. The magnetic field surrounding "c8" is likely pinched, hinting at an accretion flow along the filament.

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“…The corresponding surface density of the median N H 2 derived by Y17 is a magnitude lower than the minimum surface density of 1 g cm −2 for massive star formation derived by Krumholz & McKee (2008). The reason is the beam dilution effect (Yuan et al 2017). Hi-GAL and ATLASGAL combined images with a resolution of about 36 cannot resolve the inner cores.…”

Section: Kda Solutionsmentioning

confidence: 74%

H II regions and high-mass starless clump candidates

Zhang

Zavagno

Yuan

et al. 2020

A&A

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Context. The role of ionization feedback on high-mass (> 8 M ) star formation is still highly debated. Questions remain concerning the presence of nearby H ii regions changes the properties of early high-mass star formation and whether H ii regions promote or inhibit the formation of high-mass stars. Aims. To characterize the role of H ii regions on the formation of high-mass stars, we study the properties of a sample of candidates high-mass starless clumps (HMSCs), of which about 90% have masses larger than 100 M . These high-mass objects probably represent the earliest stages of high-mass star formation; we search if (and how) their properties are modified by the presence of an H ii region. Methods. We took advantage of the recently published catalog of HMSC candidates. By cross matching the HMSCs and H ii regions, we classified HMSCs into three categories: 1) The HMSCs associated with H ii regions both in the position in the projected plane of the sky and in velocity; 2) HMSCs associated in the plane of the sky, but not in velocity; and 3) HMSCs far away from any H ii regions in the projected sky plane. We carried out comparisons between associated and nonassociated HMSCs based on statistical analyses of multiwavelength data from infrared to radio. Results. We show that there are systematic differences of the properties of HMSCs in different environments. Statistical analyses suggest that HMSCs associated with H ii regions are warmer, more luminous, more centrally-peaked and turbulent. We also clearly show, for the first time, that the ratio of bolometric luminosity to envelope mass of HMSCs (L/M) could not be a reliable evolutionary probe for early massive star formation due to the external heating effects of the H ii regions. Conclusions. We show HMSCs associated with H ii regions present statistically significant differences from HMSCs far away from H ii regions, especially for dust temperature and L/M. More centrally peaked and turbulent properties of HMSCs associated with H ii regions may promote the formation of high-mass stars by limiting fragmentation. High-resolution interferometric surveys toward HMSCs are crucial to reveal how H ii regions impact the star formation process inside HMSCs.

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High-mass Starless Clumps in the Inner Galactic Plane: The Sample and Dust Properties

Cited by 41 publications

References 78 publications

ATLASGAL-selected massive clumps in the inner Galaxy

ATLASGAL-selected massive clumps in the inner Galaxy

A Holistic Perspective on the Dynamics of G035.39-00.33: The Interplay between Gas and Magnetic Fields

H II regions and high-mass starless clump candidates

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High-mass Starless Clumps in the Inner Galactic Plane: The Sample and Dust Properties

Cited by 41 publications

References 78 publications

ATLASGAL-selected massive clumps in the inner Galaxy

ATLASGAL-selected massive clumps in the inner Galaxy

A Holistic Perspective on the Dynamics of G035.39-00.33: The Interplay between Gas and Magnetic Fields

H II regions and high-mass starless clump candidates

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Product

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H II regions and high-mass starless clump candidates