Signatures of Inflow Motion in Cores of Massive Star Formation: Potential Collapse Candidates

Wu, Yuefang; Henkel, C.; Xue, Rui; Guan, Xin; Miller, M.

doi:10.1086/522958

Cited by 65 publications

(93 citation statements)

References 21 publications

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“…The NW source is also coincident with the submillimeter (450 and 850 μm) continuum emission from the region, which may indicate that this is a younger, more embedded source than the one responsible for the SE emission (Walsh et al 2003;Williams et al 2004Williams et al , 2005. Single-dish surveys toward G16.59-0.05 detected redshifted self-absorption in N 2 H + , HCO + , H 13 CO + , and H 2 CO rotational lines, which suggests there are inflow motions Wu et al 2007; Thomas & Fuller 2008). Bolometer array observations at 1.2 mm (Beuther et al 2002a;Faúndez et al 2004) show a peak of dust emission coinciding with the two mid-IR sources and an additional fainter source about 100 toward the SE, identified as a candidate high-mass starless core (HMSC) by Sridharan et al (2005).…”

Section: The Hmsfr G1659-005mentioning

confidence: 83%

VLBI study of maser kinematics in high-mass star-forming regions

Sanna

Moscadelli

Cesaroni

et al. 2010

A&A

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Aims. To study the high-mass star-forming process, we started a large project to unveil the gas kinematics close to young stellar objects (YSOs) through the Very Long Baseline Interferometry (VLBI) of maser associations. By comparing the high spatial resolution maser data that traces the inner kinematics of the (proto)stellar cocoon with interferometric thermal data that traces the large-scale environment of the hot molecular core (HMC) harboring the (proto)stars, we can investigate the nature and identify the sources of large-scale motions. The present paper focuses on the high-mass star-forming region G16.59-0.05. Methods. Using the VLBA and the EVN arrays, we conducted phase-referenced observations of the three most powerful maser species in G16.59-0.05: H 2 O at 22.2 GHz (4 epochs), CH 3 OH at 6.7 GHz (3 epochs), and OH at 1.665 GHz (1 epoch). In addition, we performed high-resolution (≥0. 1), high-sensitivity (<0.1 mJy) VLA observations of the radio continuum emission from the starforming region at 1.3 and 3.6 cm.Results. This is the first work to report accurate measurements of the relative proper motions of the 6.7 GHz CH 3 OH masers. The different spatial and 3-D velocity distributions clearly indicate that the 22 GHz water and 6.7 GHz methanol masers trace different kinematic environments. The bipolar distribution of 6.7 GHz maser line-of-sight velocities and the regular pattern of observed proper motions suggest that these masers are tracing rotation around a central mass of about 35 M . The flattened spatial distribution of the 6.7 GHz masers, oriented NW−SE, suggests that they can originate in a disk/toroid rotating around the massive YSO that drives the 12 CO (2−1) outflow, oriented NE−SW, observed on an arcsec scale. The extended, radio continuum source observed close to the 6.7 GHz masers could be excited by a wide-angle wind emitted from the YSO associated with the methanol masers, and such a wind has proven to be energetic enough to drive the NE−SW 12 CO (2−1) outflow. The H 2 O masers are distributed across a region offset about 0. 5 to the NW of the CH 3 OH masers, in the same area as where the emission of high-density molecular tracers, typical of HMCs, was detected. We postulate that a distinct YSO, possibly in an earlier evolutionary phase than what excites the methanol masers, is responsible for the excitation of the water masers and the HMC molecular lines.

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Section: The Hmsfr G1659-005mentioning

confidence: 83%

VLBI study of maser kinematics in high-mass star-forming regions

Sanna

Moscadelli

Cesaroni

et al. 2010

A&A

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“…Several surveys have been undertaken to search for infall of molecular gas associated with massive star formation. Among these are Fuller et al (2005), Purcell et al (2006), Klassen & Wilson (2007), and Wu et al (2007). All of these used HCO + and H 13 CO + (3−2) observations along with a few other molecular probes.…”

Section: Resultsmentioning

confidence: 99%

A millimeter survey of ultra-compact HII-regions and associated molecular clouds

Churchwell

Sievers

Thum

2010

A&A

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We report observations, using the IRAM 30 m telescope, of 30 ultracompact and hypercompact HII regions in the lines of HCO + (3−2) and/or HCO + (1−0) and H30α and/or H39α. Images are presented in both HCO + (3−2) and H30α toward a subset of regions (16 in HCO + (3−2), 14 in H30α) with a resolution of 12 . In addition, H 13 CO + (3−2) observations are reported toward 13 HII regions where HCO + (3−2) displays complex profiles. It is shown that the absorption dips in the HCO + profiles are due to HCO + self-absorption, not absorption of the HII free-free emission or warm dust emission surrounding the HII region or two velocity components along the line of sight. It was found that among the sources with self-absorbed profiles, 8 are contracting and 5 are expanding. Mass fluxes are found to be typically a few times 10 −3 M yr −1 , implying time scales for massive star formation <10 5 yrs. HCO + and H 2 column densities are estimated for a subset of the sources from which masses of the dense central cloud cores were estimated. Implications of the derived column densities, masses, flow velocities, and mass fluxes are discussed.

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“…This red-shifted self-absorption is what makes the spectrum present a brighter blue peak. To quantify this asymmetry, the calculation of the normalized line velocity difference has been used by many authors (Fuller et al 2005;Szymczak et al 2007;Wu et al 2007).…”

Section: Infall Motionsmentioning

confidence: 99%

G30.79 FIR 10: a gravitationally bound infalling high-mass star-forming clump

Cortés

Parra

Cortés

et al. 2010

A&A

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Context. The process of high-mass star formation is still shrouded in controversy. Models are still tentative and current observations are just beginning to probe the densest inner regions of giant molecular clouds. Aims. The study of high-mass star formation requires the observation and analysis of high-density gas. This can be achieved by the detection of emission from higher rotational transitions of molecules in the sub-millimeter. Here, we studied the high-mass clump G30.79 FIR 10 by observing molecular emission in the 345 GHz band. The goal is to understand the gravitational state of this clump, considering turbulence and magnetic fields, and to study the kinematics of dense gas. Methods. We approached this region by mapping the spatial distribution of HCO + (J = 4 → 3), H 13 CO + (J = 4 → 3), CS(J = 7 → 6), 12 CO(J = 3 → 2), and 13 CO(J = 3 → 2) molecular emission by using the ASTE telescope and by observing the 12 C 18 O(J = 3 → 2), HCN(J = 4 → 3), and H 13 CN(J = 4 → 3) molecular transitions with the APEX telescope. Results. Infalling motions were detected and modeled toward this source. A mean infall velocity of 0.5 km s −1 with an infall mass rate of 5 × 10 −3 M yr −1 was obtained. Also, a previously estimated value for the magnetic field strength in the plane of the sky was refined to be 855 μG which we used to calculate a mass-to-magnetic flux ratio, λ = 1.9, or super-critical. The virial mass from turbulent motions was also calculated finding M vir = 563 M , which gives a ratio of M submm /M vir = 5.9. Both values strongly suggest that this clump must be in a state of gravitational collapse. Additionally, we estimated the HCO + abundance, obtaining X(HCO + ) = 2.4×10 −10 .

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Signatures of Inflow Motion in Cores of Massive Star Formation: Potential Collapse Candidates

Cited by 65 publications

References 21 publications

VLBI study of maser kinematics in high-mass star-forming regions

VLBI study of maser kinematics in high-mass star-forming regions

A millimeter survey of ultra-compact HII-regions and associated molecular clouds

G30.79 FIR 10: a gravitationally bound infalling high-mass star-forming clump

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