Synthetic observations of dust emission and polarisation of Galactic cold clumps

Juvela, M.; Padoan, Paolo; Ristorcelli, I.; Pelkonen, Veli-Matti

doi:10.1051/0004-6361/201935882

Cited by 4 publications

(2 citation statements)

References 85 publications

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“…Juvela et al (2019) carried out similar synthetic observations of Planck cold clumps. As in this work, the masses and sizes of extracted sources were found to depend not only on the distance, but also on the amount of line-of-sight confusion.…”

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confidence: 99%

The Origin of Massive Stars: The Inertial-inflow Model

Padoan

Pan²,

Juvela³

et al. 2020

ApJ

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131

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We address the problem of the origin of massive stars, namely the origin, path and timescale of the mass flows that create them. Based on extensive numerical simulations, we propose a scenario where massive stars are assembled by large-scale, converging, inertial flows that naturally occur in supersonic turbulence. We refer to this scenario of massive-star formation as the Inertial-Inflow Model. This model stems directly from the idea that the mass distribution of stars is primarily the result of turbulent fragmentation. Under this hypothesis, the statistical properties of the turbulence determine the formation timescale and mass of prestellar cores, posing definite constraints on the formation mechanism of massive stars. We quantify such constraints by the analysis of a simulation of supernova-driven turbulence in a 250-pc region of the interstellar medium, describing the formation of hundreds of massive stars over a time of approximately 30 Myr. Due to the large size of our statistical sample, we can say with full confidence that massive stars in general do not form from the collapse of massive cores, nor from competitive accretion, as both models are incompatible with the numerical results. We also compute synthetic continuum observables in Herschel and ALMA bands. We find that, depending on the distance of the observed regions, estimates of core mass based on commonlyused methods may exceed the actual core masses by up to two orders of magnitude, and that there is essentially no correlation between estimated and real core masses.

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mentioning

confidence: 99%

The Origin of Massive Stars: The Inertial-inflow Model

Padoan

Pan²,

Juvela³

et al. 2020

ApJ

Self Cite

131

124

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“…The observed prestellar CMFs are extracted from 2D intensity information, such as dust-emission or dust-extinction maps, which involves a degree of line-of-sight confusion (e.g. Juvela et al 2019). Furthermore, the observed quantities must be converted into column density, which, in the case of sub-mm observations, depends on possible temperature and dust-opacity variations, leading to a significant uncertainty in the mass determination (e.g.…”

Section: The Observed Core Mass Functionmentioning

confidence: 99%

From the CMF to the IMF: Beyond the Core-Collapse Model

Pelkonen,

Padoan,

Haugbølle

et al. 2020

Preprint

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Observations have indicated that the prestellar core mass function is similar to the IMF, except for an offset towards larger masses. This has led to the idea that there is a one-to-one relation between cores and stars, such that the whole stellar mass reservoir is contained in a gravitationally-bound prestellar core, as postulated by the core-collapse model, and assumed in recent theoretical models of the stellar IMF. We test the validity of this assumption by comparing the final mass of stars with the mass of their progenitor cores in a high-resolution star-formation simulation that generates a realistic IMF under physical conditions characteristic of observed molecular clouds. We find that the core mass function and the IMF are closely related in a statistical sense only; for any individual star there is only a weak correlation between the progenitor core mass and the final stellar mass. In particular, for high mass stars only a small fraction of the final stellar mass comes from the progenitor core, and even for low mass stars the fraction is highly variable, with a median fraction of only about 50%. We conclude that the core-collapse scenario and related models for the origin of the IMF are incomplete.

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Dust evolution across the Horsehead nebula

Schirmer

Abergel

Verstraete

et al. 2020

A&A

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Context. Micro-physical processes on interstellar dust surfaces are tightly connected to dust properties (i.e. dust composition, size, and shape) and play a key role in numerous phenomena in the interstellar medium (ISM). The large disparity in physical conditions (i.e. density and gas temperature) in the ISM triggers an evolution of dust properties. The analysis of how dust evolves with the physical conditions is a stepping stone towards a more thorough understanding of interstellar dust. Aims. We highlight dust evolution in the Horsehead nebula photon-dominated region. Methods. We used Spitzer/IRAC (3.6, 4.5, 5.8 and 8 μm) and Spitzer/MIPS (24 μm) together with Herschel/PACS (70 and 160 μm) and Herschel/SPIRE (250, 350 and 500 μm) to map the spatial distribution of dust in the Horsehead nebula over the entire emission spectral range. We modelled dust emission and scattering using the THEMIS interstellar dust model together with the 3D radiative transfer code SOC. Results. We find that the nano-grain dust-to-gas ratio in the irradiated outer part of the Horsehead is 6–10 times lower than in the diffuse ISM. The minimum size of these grains is 2–2.25 times larger than in the diffuse ISM, and the power-law exponent of their size distribution is 1.1–1.4 times lower than in the diffuse ISM. In the denser part of the Horsehead nebula, it is necessary to use evolved grains (i.e. aggregates, with or without an ice mantle). Conclusions. It is not possible to explain the observations using grains from the diffuse medium. We therefore propose the following scenario to explain our results. In the outer part of the Horsehead nebula, all the nano-grain have not yet had time to re-form completely through photo-fragmentation of aggregates and the smallest of the nano-grain that are sensitive to the radiation field are photo-destroyed. In the inner part of the Horsehead nebula, grains most likely consist of multi-compositional mantled aggregates.

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Synthetic observations of dust emission and polarisation of Galactic cold clumps

Cited by 4 publications

References 85 publications

The Origin of Massive Stars: The Inertial-inflow Model

The Origin of Massive Stars: The Inertial-inflow Model

From the CMF to the IMF: Beyond the Core-Collapse Model

Dust evolution across the Horsehead nebula

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