Protostellar Outflows and Radiative Feedback From Massive Stars. Ii. Feedback, Star-Formation Efficiency, and Outflow Broadening

Kuiper, Rolf; Turner, Neal J.; Yorke, H. W.

doi:10.3847/0004-637x/832/1/40

Cited by 69 publications

(87 citation statements)

References 59 publications

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“…As for the jets/outflows, the interaction between the outflowing gas and the surrounding environment is expected to cause shocks (see e.g. Kuiper et al 2016), triggering the formation of silicon monoxide, which is indeed often observed in knots along the jet/outflow axis (see e.g. Bachiller et al 1997;Gueth et al 1998;Sollins et al 2004;Cesaroni et al 2005).…”

Section: Line Emissionmentioning

confidence: 99%

Chasing discs around O-type (proto)stars: Evidence from ALMA observations

Cesaroni

Sánchez-Monge

Beltrán

et al. 2017

A&A

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Context. Circumstellar discs around massive stars could mediate the accretion onto the star from the infalling envelope, and could minimize the effects of radiation pressure. Despite such a crucial role, only a few convincing candidates have been provided for discs around deeply embedded O-type (proto)stars. Aims. In order to establish whether disc-mediated accretion is the formation mechanism for the most massive stars, we have searched for circumstellar, rotating discs around a limited sample of six luminous (>10 5 L ) young stellar objects. These objects were selected on the basis of their IR and radio properties in order to maximize the likelihood of association with disc+jet systems. Methods. We used ALMA with ∼0 . 2 resolution to observe a large number of molecular lines typical of hot molecular cores. In this paper we limit our analysis to two disc tracers (methyl cyanide, CH 3 CN, and its isotopologue, 13 CH 3 CN), and an outflow tracer (silicon monoxide, SiO). Results. We reveal many cores, although their number depends dramatically on the target. We focus on the cores that present prominent molecular line emission. In six of these a velocity gradient is seen across the core, three of which show evidence of Keplerian-like rotation. The SiO data reveal clear but poorly collimated bipolar outflow signatures towards two objects only. This can be explained if real jets are rare (perhaps short-lived) in very massive objects and/or if stellar multiplicity significantly affects the outflow structure. For all cores with velocity gradients, the velocity field is analysed through position-velocity plots to establish whether the gas is undergoing rotation with rot ∝ R −α , as expected for Keplerian-like discs. Conclusions. Our results suggest that in three objects we are observing rotation in circumstellar discs, with three more tentative cases, and one core where no evidence for rotation is found. In all cases but one, we find that the gas mass is less than the mass of any embedded O-type star, consistent with the (putative) discs undergoing Keplerian-like rotation. With the caveat of low number statistics, we conclude that the disc detection rate could be sensitive to the evolutionary stage of the young stellar object. In young, deeply embedded sources, the evidence for discs could be weak because of confusion with the surrounding envelope, while in the most evolved sources the molecular component of the disc could have already been dispersed. Only in those objects that are at an intermediate stage of the evolution would the molecular disc be sufficiently prominent and relatively less embedded to be detectable by mm/submm observations.

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Section: Line Emissionmentioning

confidence: 99%

Chasing discs around O-type (proto)stars: Evidence from ALMA observations

Cesaroni

Sánchez-Monge

Beltrán

et al. 2017

A&A

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“…Hosokawa et al 2010), its epoch of disk formation, and accretion rate (e.g. Kuiper & Yorke 2013;Kuiper et al 2016). In the bloated phase the massive protostar has a size of 10-100 times its ZAMS radius (Hosokawa et al 2010), which lowers the surface temperature and consequently, the ionising radiation.…”

Section: Introductionmentioning

confidence: 99%

The evolution of young HII regions

Klaassen

Johnston

Urquhart

et al. 2018

A&A

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Context. High-mass stars form in much richer environments than those associated with isolated low-mass stars, and once they reach a certain mass, produce ionised (Hii) regions. The formation of these pockets of ionised gas are unique to the formation of high-mass stars (M > 8 M ), and present an excellent opportunity to study the final stages of accretion, which could include accretion through the Hii region itself. Aims. This study of the dynamics of the gas on both sides of these ionisation boundaries in very young Hii regions aims to quantify the relationship between the Hii regions and their immediate environments. Methods. We present high-resolution (∼ 0.5 ) ALMA observations of nine Hii regions selected from the Red MSX Source (RMS) survey with compact radio emission and bolometric luminosities greater than 10 4 L . We focus on the initial presentation of the data, including initial results from the radio recombination line H29α, some complementary molecules, and the 256 GHz continuum emission. Results. Of the six (out of nine) regions with H29α detections, two appear to have cometary morphologies with velocity gradients across them, and two appear more spherical with velocity gradients suggestive of infalling ionised gas. The remaining two were either observed at low resolution or had signals that were too weak to draw robust conclusions. We also present a description of the interactions between the ionised and molecular gas (as traced by CS (J=5-4)), often (but not always) finding the Hii region had cleared its immediate vicinity of molecules. Conclusions. Of our sample of nine, the observations of the two clusters expected to have the youngest Hii regions (from previous radio observations) are suggestive of having infalling motions in the H29α emission, which could be indicative of late stage accretion onto the stars despite the presence of an Hii region.

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“…The recent simulation with high resolution and moving sink particle method by Rosen et al (2016) showed that the Rayleigh-Taylor (RT) instability strongly helps to bypass the radiation pressure barrier even above the disk. Also, if MHD outflow cavities exist before radiation pressure becomes significant, then radiation leaks away via these channels, i.e., enhancing the so-called "flashlight effect" (Yorke & Bodenheimer 1999;Yorke & Sonnhalter 2002;Krumholz et al 2005;Kuiper et al 2015Kuiper et al , 2016. Thus, the radiation pressure barrier is not thought to be a catastrophic problem anymore for massive star formation.…”

Section: Introductionmentioning

confidence: 99%

“…This radiation by dust re-emission should be reduced significantly by the pre-existing MHD outflow cavity (Krumholz et al 2005;Kuiper et al 2015Kuiper et al , 2016 and/or the RT instability (Krumholz et al 2009;Rosen et al 2016). Therefore, in the implementation of our model in this paper the effect of dust re-emission is ignored and only direct stellar radiation is considered, i.e., f trap = 1.…”

Section: Feedback Processesmentioning

confidence: 99%

The Impact of Feedback During Massive Star Formation by Core Accretion

Tanaka

Tan

Zhang

2017

ApJ

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We study feedback during massive star formation using semi-analytic methods, considering the effects of disk winds, radiation pressure, photoevaporation and stellar winds, while following protostellar evolution in collapsing massive gas cores. We find that disk winds are the dominant feedback mechanism setting star formation efficiencies (SFEs) from initial cores of ∼ 0.3-0.5. However, radiation pressure is also significant to widen the outflow cavity causing reductions of SFE compared to the disk-wind only case, especially for > 100M ⊙ star formation at clump mass surface densities. Photoevaporation is of relatively minor importance due to dust attenuation of ionizing photons. Stellar winds have even smaller effects during the accretion stage. For core masses M c ≃ 10-1000 M ⊙ and Σ cl ≃ 0.1-3 g cm −2 , we find the overall SFE to beε * f = 0.31(R c /0.1 pc) −0.39 , potentially a useful sub-grid star-formation model in simulations that can resolve pre-stellar core radii,The decline of SFE with M c is gradual with no evidence for a maximum stellar-mass set by feedback processes up to stellar masses of m * ∼ 300 M ⊙ . We thus conclude that the observed truncation of the high-mass end of the IMF is shaped mostly by the pre-stellar core mass function or internal stellar processes. To form massive stars with the observed maximum masses of ∼ 150-300M ⊙ , initial core masses need to be 500-1000 M ⊙ . We also apply our feedback model to zero-metallicity primordial star formation, showing that, in the absence of dust, photoevaporation staunches accretion at ∼ 50 M ⊙ . Our model implies radiative feedback is most significant at metallicities ∼ 10 −2 Z ⊙ , since both radiation pressure and photoevaporation are effective in this regime.

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Protostellar Outflows and Radiative Feedback From Massive Stars. Ii. Feedback, Star-Formation Efficiency, and Outflow Broadening

Cited by 69 publications

References 59 publications

Chasing discs around O-type (proto)stars: Evidence from ALMA observations

Chasing discs around O-type (proto)stars: Evidence from ALMA observations

The evolution of young HII regions

The Impact of Feedback During Massive Star Formation by Core Accretion

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