RAPID CIRCUMSTELLAR DISK EVOLUTION AND AN ACCELERATING STAR FORMATION RATE IN THE INFRARED DARK CLOUD M17 SWex

Povich, Matthew S.; Townsley, Leisa K.; Robitaille, T. P.; Broos, P. S.; Orbin, W.; King, Robert R.; Naylor, T.; Whitney, B. A.

doi:10.3847/0004-637x/825/2/125

Cited by 47 publications

(79 citation statements)

References 103 publications

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“…In general, deeply embedded YSOs (red stars as stage 0/I sources; Povich et al 2016) are found to be associated with hubs and filaments while evolved YSOs (blue stars as stage II/III and blue crosses as X-ray sources; Povich et al 2016) appear more distributed in the regions. Dense cores identified in the continuum studies (brown open circles; Ohashi et al 2016) are preferentially located in hubs, and just a few in filaments.…”

Section: Observationsmentioning

confidence: 98%

Filamentary Accretion Flows in the Infrared Dark Cloud G14.225–0.506 Revealed by ALMA

Chen

Zhang

Wright

et al. 2019

ApJ

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Filaments are ubiquitous structures in molecular clouds and play an important role in the mass assembly of stars. We present results of dynamical stability analyses for filaments in the infrared dark cloud G14.225−0.506, where a delayed onset of massive star formation was reported in the two hubs at the convergence of multiple filaments of parsec length. Full-synthesis imaging is performed with the Atacama Large Millimeter/submillimeter Array (ALMA) to map the N 2 H + (1 − 0) emission in two hub-filament systems with a spatial resolution of ∼ 0.034 pc. Kinematics are derived from sophisticated spectral fitting algorithm that accounts for line blending, large optical depth, and multiple velocity components. We identify five velocity coherent filaments and derive their velocity gradients with principal component analysis. The mass accretion rates along the filaments are up to 10 −4 M yr −1 and are significant enough to affect the hub dynamics within one free-fall time (∼ 10 5 yr). The N 2 H + filaments are in equilibrium with virial parameter α vir ∼ 1.2. We compare α vir measured in the N 2 H + filaments, NH 3 filaments, 870 µm dense clumps, and 3 mm dense cores. The decreasing trend in α vir with decreasing spatial scales persists, suggesting an increasingly important role of gravity at small scales. Meanwhile, α vir also decreases with decreasing non-thermal motions. In combination with the absence of high-mass protostars and massive cores, our results are consistent with the global hierarchical collapse scenario.

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Section: Observationsmentioning

confidence: 98%

Filamentary Accretion Flows in the Infrared Dark Cloud G14.225–0.506 Revealed by ALMA

Chen

Zhang

Wright

et al. 2019

ApJ

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“…The HII region (M17-HII region) surrounding the cluster has opened a large gap at its edge which lets stellar radiation and winds escape exciting a diffuse X-Ray emitting region observed with the Chandra Observatory (Townsley et al 2003). In addition to the relatively mature HII region around the cluster, other notable star-forming regions have been discovered in the vicinity of M17 such as the immediate environment of M17 (Ando et al 2002), or the M17 Infrared Dark Cloud (M17-IRDC, also known as M7-SWex) that contains the IRDC G14.225-0.506 (Povich & Whitney 2010;Povich et al 2016;Ohashi et al 2016). M17 forms a larger molecular cloud complex together with M16 cloud as suggested by Nguyen-Luong et al (2016).…”

Section: Overview Of the M17 Regionmentioning

confidence: 99%

“…Interestingly, a second compression at the interface of the M17-HII region when the OB star clusters compress the edge of the cloud also occured which can be seen in CO (J = 3 − 2) (Rainey et al 1987) and also in high density tracer such as HCN (J = 4 − 3) (White et al 1982). From the Spitzer observations, Povich & Whitney (2010) and Povich et al (2016) discovered that the mass function of young stellar objects (YSOs) around the M17-HII region seems consistent with the Salpeter IMF, whereas that in the M17-IRDC is significantly steeper than the Salpeter IMF. In other words, the high-mass stellar population in M17-IRDC is deficient.…”

Section: Overview Of the M17 Regionmentioning

confidence: 99%

“…and M17-IRDC The mass functions of YSOs in the M17-HII and M17-IRDC regions were derived by Povich & Whitney (2010) and Povich et al (2016) using Spitzer data. They found that the high-mass stellar population is deficient in M17-IRDC, claiming a possibility that the massive star formation is delayed in the M17-IRDC region assuming that the final stellar IMF approaches to the Salpeter IMF.…”

Section: Conditions For Massive Star Formation In M17 Hiimentioning

confidence: 99%

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Large-scale Molecular Gas Distribution in the M17 Cloud Complex: Dense Gas Conditions of Massive Star Formation?

Nguyen-Luong

Nakamura

Sugitani

et al. 2020

ApJ

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The non-uniform distribution of gas and protostars in molecular clouds is caused by combinations of various physical processes that are difficult to separate. We explore this non-uniform distribution in the M17 molecular cloud complex that hosts massive star formation activity using the 12 CO (J = 1−0) and 13 CO (J = 1 − 0) emission lines obtained with the Nobeyama 45m telescope. Differences in clump properties such as mass, size, and gravitational boundedness reflect the different evolutionary stages of the M17-HII and M17-IRDC clouds. Clumps in the M17-HII cloud are denser, more compact, and more gravitationally bound than those in M17-IRDC. While M17-HII hosts a large fraction of very dense gas (27%) that has column density larger than the threshold of ∼ 1 g cm −2 theoretically predicted for massive star formation, this very dense gas is deficient in M17-IRDC (0.46%). Our HCO + (J = 1 − 0) and HCN (J = 1 − 0) observations with the TRAO 14m telescope, trace all gas with column density higher than 3 × 10 22 cm −2 , confirm the deficiency of high density ( 10 5 cm −3 ) gas in M17-IRDC.Although M17-IRDC is massive enough to potentially form massive stars, its deficiency of very dense gas and gravitationally bound clumps can explain the current lack of massive star formation.

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“…formation rate ≥ 0.004 M ⊙ yr −1 (see Povich et al 2016, and references therein). Chibueze et al (2016) identified hundreds of H 2 O maser sources in the M17 region spanning a local standard of rest velocity (v LSR ) range of 14.0-22.0 km s −1 .…”

Section: Selected Regionsmentioning

confidence: 99%

Influence of Wolf–Rayet Stars on Surrounding Star-forming Molecular Clouds

Baug¹,

Grijs

Dewangan

et al. 2019

ApJ

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We investigate the influence of Wolf-Rayet (W-R) stars on their surrounding star-forming molecular clouds. We study five regions containing W-R stars in the inner Galactic plane (l ∼[14 • -52 • ]), using multi-wavelength data from near-infrared to radio wavelengths. Analysis of 13 CO line data reveals that these W-R stars have developed gas-deficient cavities in addition to molecular shells with expansion velocities of a few km s −1 . The pressure owing to stellar winds primarily drives these expanding shells and sweeps up the surrounding matter to distances of a few pc. The column densities of shells are enhanced by a minimum of 14% for one region to a maximum of 88% for another region with respect to the column densities within their central cavities. No active star formationincluding molecular condensations, protostars, or ionized gas -is found inside the cavities, whereas such features are observed around the molecular shells. Although the expansion of ionized gas is considered an effective mechanism to trigger star formation, the dynamical ages of the H ii regions in our sample are generally not sufficiently long to do so efficiently. Overall, our results hint at the possible importance of negative W-R wind-driven feedback on the gas-deficient cavities, where star formation is quenched as a consequence. In addition, the presence of active star formation around the molecular shells indicates that W-R stars may also assist in accumulating molecular gas, and that they could initiate star formation around those shells.

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RAPID CIRCUMSTELLAR DISK EVOLUTION AND AN ACCELERATING STAR FORMATION RATE IN THE INFRARED DARK CLOUD M17 SWex

Cited by 47 publications

References 103 publications

Filamentary Accretion Flows in the Infrared Dark Cloud G14.225–0.506 Revealed by ALMA

Filamentary Accretion Flows in the Infrared Dark Cloud G14.225–0.506 Revealed by ALMA

Large-scale Molecular Gas Distribution in the M17 Cloud Complex: Dense Gas Conditions of Massive Star Formation?

Influence of Wolf–Rayet Stars on Surrounding Star-forming Molecular Clouds

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