On the physics of dust grains in hot gas

Draine, B. T.; Salpeter, E. E.

doi:10.1086/157165

Cited by 741 publications

(739 citation statements)

References 3 publications

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“…4). In the mostlyionized medium, we also need to account for Coulomb interactions, but these primarily manifest as a modest correction to the drag term (Draine & Salpeter 1979) so their effect should be straightforward to understand and implement numerically. Radiation pressure and dust collisional dynamics may also modify the conclusions here, especially in the most-dense regions where this is relevant for star formation, and we will explore this further in future work.…”

Section: Resultsmentioning

confidence: 99%

“…Dust is represented as a population of tracer particles integrated on-the-fly through the fluid (representing grains of fixed size), with the equation of motion (EOM; Draine & Salpeter 1979): . Time-averaged distribution of dust-to-gas ratios δ ≡ (n dust /ngas)/( n dust / ngas ) (= 1 at mean densities; see Table 1) in the simulations (with "normal" Lorentz forces).…”

Section: Methodsmentioning

confidence: 99%

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The dynamics of charged dust in magnetized molecular clouds

Lee

Hopkins

Squire

2017

Monthly Notices of the Royal Astronomical Society

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We study the dynamics of large, charged dust grains in turbulent giant molecular clouds (GMCs). Massive dust grains behave as aerodynamic particles in primarily neutral dense gas, and thus are able to produce dramatic small-scale fluctuations in the dust-to-gas ratio. Hopkins & Lee (2016) directly simulated the dynamics of neutral dust grains in super-sonic MHD turbulence, typical of GMCs, and showed that the dust-to-gas fluctuations can exceed factor ∼ 1000 on small scales, with important implications for star formation, stellar abundances, and dust behavior and growth. However, even in primarily neutral gas in GMCs, dust grains are negatively charged and Lorentz forces are non-negligible. Therefore, we extend our previous study by including the effects of Lorentz forces on charged grains (in addition to drag). For small charged grains (sizes 0.1 µm), Lorentz forces suppress dust-to-gas ratio fluctuations, while for large grains (sizes 1 µm), Lorentz forces have essentially no effect, trends that are well explained with a simple theory of dust magnetization. In some special intermediate cases, Lorentz forces can enhance dust-gas segregation. Regardless, for the physically expected scaling of dust charge with grain size, we find the most important effects depend on grain size (via the drag equation) with Lorentz forces/charge as a second-order correction. We show that the dynamics we consider are determined by three dimensionless numbers in the limit of weak background magnetic fields: the turbulent Mach number, a dust drag parameter (proportional to grain size) and a dust Lorentz parameter (proportional to grain charge); these allow us to generalize our simulations to a wide range of conditions.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

The dynamics of charged dust in magnetized molecular clouds

Lee

Hopkins

Squire

2017

Monthly Notices of the Royal Astronomical Society

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“…Ferland, Fabian & Johnstone 1994;Ferland et al 2009). Dust grains are sputtered rapidly (< 1 Myr) in the X-ray atmosphere (Draine & Salpeter 1979;Dwek & Arendt 1992) so cooling X-ray gas is likely dust-free. However, the N and SE molecular filaments are clearly coincident with dust lanes in the HST observations (Fig.…”

Section: Forming Molecular Gas In Extended Filamentsmentioning

confidence: 99%

ALMA observations of cold molecular gas filaments trailing rising radio bubbles in PKS 0745−191

Russell

McNamara

Fabian

et al. 2016

Mon. Not. R. Astron. Soc.

105

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We present ALMA observations of the CO(1-0) and CO(3-2) line emission tracing filaments of cold molecular gas in the central galaxy of the cluster PKS 0745-191. The total molecular gas mass of 4.6±0.3×10 9 M , assuming a Galactic X CO factor, is divided roughly equally between three filaments each extending radially 3 − 5 kpc from the galaxy centre. The emission peak is located in the SE filament ∼ 1 arcsec (2 kpc) from the nucleus. The velocities of the molecular clouds in the filaments are low, lying within ±100 km s −1 of the galaxy's systemic velocity. Their FWHMs are less than 150 km s −1 , which is significantly below the stellar velocity dispersion. Although the molecular mass of each filament is comparable to a rich spiral galaxy, such low velocities show that the filaments are transient and the clouds would disperse on < 10 7 yr timescales unless supported, likely by the indirect effect of magnetic fields. The velocity structure is inconsistent with a merger origin or gravitational free-fall of cooling gas in this massive central galaxy. If the molecular clouds originated in gas cooling even a few kpc from their current locations their velocities would exceed those observed. Instead, the projection of the N and SE filaments underneath X-ray cavities suggests they formed in the updraft behind bubbles buoyantly rising through the cluster atmosphere. Direct uplift of the dense gas by the radio bubbles appears to require an implausibly high coupling efficiency. The filaments are coincident with low temperature X-ray gas, bright optical line emission and dust lanes indicating that the molecular gas could have formed from lifted warmer gas that cooled in situ.

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“…Unfortunately, no measurements have been made on olivine ((Mg,Fe)Si04), which is believed to be one of the main forms of refractory dust in the interstellar medium. Prescriptions for ex-trapolating the sputtering yields towards lower energies have been given by Barlow (1978), Draine & Salpeter (1979a) and Tielens et al (1994), who considered only H+ and He + as impacting particles. These extrapolations broadly agree in predicting a rapid drop in the sputtering yields below 100 eV and indicate that the yield for He + impact on S1O2 attains 2 10~4 at an energy of about 30 eV (see Fig.…”

Section: Sputtering Yields Of the Refractory Grainsmentioning

confidence: 99%

Non thermal sputtering of grains and production of SiO in interstellar shocks

Forêts¹,

Flower

1997

Symp. - Int. Astron. Union

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Abstract. We present recent results for the yields of Si and O, produced in the sputtering of S1O2 by ions of different masses, and show the importance of sputtering by heavy particles at low streaming velocities. These data are incorporated in a C-shock model to study the erosion of interstellar grains and the release of silicon through non-thermal sputtering within the shock. Once in the gas phase, the atomic silicon reacts with O2 and is rapidly transformed into SiO. The column densities of SiO thus calculated are compared with the observations of molecular outflows with a satisfactory agreement. In the postshock gas, SiO disappears from the gas phase through the reaction SiO(OH,H)Si02 and S1O2 remains, unseen, in the cold dense gas. This could explain the extremely low upper limits of SiO deduced from observations of dark clouds.

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On the physics of dust grains in hot gas

Cited by 741 publications

References 3 publications

The dynamics of charged dust in magnetized molecular clouds

The dynamics of charged dust in magnetized molecular clouds

ALMA observations of cold molecular gas filaments trailing rising radio bubbles in PKS 0745−191

Non thermal sputtering of grains and production of SiO in interstellar shocks

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