Recent progress in theory and observational study of dust grain alignment and rotational disruption in star-forming regions

Tram, Le Ngoc; Hoang, Thiem

doi:10.3389/fspas.2022.923927

Cited by 13 publications

(3 citation statements)

References 141 publications

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“…One of the methods consists in using dust polarization (see, e.g., Lazarian 2007;and Andersson et al 2015 for reviews). The basic idea of this technique relies on the fact that irregular dust grains tend to align with their shortest axis parallel to the local B-fields due to various physical effects (see, e.g., Hoang et al 2022a for details) so that their thermal emission is polarized with the polarization orientation perpendicular to the B-fields (see Tram & Hoang 2022). The measured position angle of thermal dust polarization is then perpendicular to the local B-fields in the plane of the sky.…”

Section: Introductionmentioning

confidence: 99%

SOFIA Observations of 30 Doradus. II. Magnetic Fields and Large-scale Gas Kinematics

Tram

Bonne

et al. 2023

ApJ

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The heart of the Large Magellanic Cloud, 30 Doradus, is a complex region with a clear core-halo structure. Feedback from the stellar cluster R136 has been shown to be the main source of energy creating multiple parsec-scale expanding-shells in the outer region, and carving a nebula core in the proximity of the ionization source. We present the morphology and strength of the magnetic fields (B-fields) of 30 Doradus inferred from the far-infrared polarimetric observations by SOFIA/HAWC+ at 89, 154, and 214 μm. The B-field morphology is complex, showing bending structures around R136. In addition, we use high spectral and angular resolution [C ii] observations from SOFIA/GREAT and CO(2-1) from APEX. The kinematic structure of the region correlates with the B-field morphology and shows evidence of multiple expanding-shells. Our B-field strength maps, estimated using the Davis–Chandrasekhar–Fermi method and structure-function, show variations across the cloud within a maximum of 600, 450, and 350 μG at 89, 154, and 214 μm, respectively. We estimated that the majority of the 30 Doradus clouds are subcritical and sub-Alfvénic. The probability distribution function of the gas density shows that the turbulence is mainly compressively driven, while the plasma beta parameter indicates supersonic turbulence. We show that the B-field is sufficient to hold the cloud structure integrity under feedback from R136. We suggest that supersonic compressive turbulence enables the local gravitational collapse and triggers a new generation of stars to form. The velocity gradient technique using [C ii] and CO(2-1) is likely to confirm these suggestions.

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Section: Introductionmentioning

confidence: 99%

SOFIA Observations of 30 Doradus. II. Magnetic Fields and Large-scale Gas Kinematics

Tram

Bonne

et al. 2023

ApJ

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“…We should caution that it is difficult to compare the magnetic field probed by polarized dust emission with that obtained from synchtroton emission. Indeed different magnetic field strengths were found at different wavelengths in 30 Dor (Tram et al 2022 ). The high field strengths derived here could also be affected by the uncertainties in the DCF method, including the filling factor of dense gas (as the ejecta knots are highly clumpy) and the associated velocity dispersion of the clumpy knots.…”

Section: Potential Contaminants In the Polarized Signal From The Chop...mentioning

confidence: 71%

Far-infrared polarization of the supernova remnant Cassiopeia A with SOFIA HAWC +

Rho

Ravi

Tram

et al. 2023

Monthly Notices of the Royal Astronomical Society

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We present polarization observations of the young supernova remnant (SNR) Cas A using the High-resolution Airborne Wideband Camera-Plus (HAWC +) instrument onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). The polarization map at 154 $\mu$m reveals dust grains with strong polarization fractions (5–30 per cent), supporting previous measurements made over a smaller region of the remnant at 850 $\mu$m. The 154-$\mu$m emission and the polarization signal is coincident with a region of cold dust observed in the southeastern shell and in the unshocked central ejecta. The highly polarized far-IR emission implies the grains are large (>0.14 $\mu$m) and silicate-dominated. The polarization level varies across the SNR, with an inverse correlation between the polarization degree and the intensity and smaller polarization angle dispersion for brighter SNR emission. Stronger polarization is detected between the bright structures. This may result from a higher collision rate between the gas and dust producing a lower grain alignment efficiency where the gas density is higher. We use the dust emission to provide an estimate of the magnetic field strength in Cas A using the Davis–Chandrasekhar–Fermi method. The high polarization level is direct evidence that grains are highly elongated and strongly aligned with the magnetic field of the SNR. The dust mass from the polarized region is 0.14 ± 0.04 M⊙, a lower limit of the amount of dust present within the ejecta of Cas A. This result strengthens the hypothesis that core-collapse SNe are an important contributor to the dust mass in high redshift galaxies.

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“…As described in Tram & Hoang (2022), the RAT acting on a grain is directly proportionate to the energy density of the radiation field. A more luminous protostar would therefore create a stronger RAT, leading to a higher probability of radiatively aligned grains.…”

Section: Polarization Spectramentioning

confidence: 99%

Protoplanetary Disk Polarization at Multiple Wavelengths: Are Dust Populations Diverse?

Harrison,

Lin,

Looney

et al. 2024

ApJ

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Millimeter and submillimeter observations of continuum linear dust polarization provide insight into dust grain growth in protoplanetary disks, which are the progenitors of planetary systems. We present the results of the first survey of dust polarization in protoplanetary disks at 870 μm and 3 mm. We find that protoplanetary disks in the same molecular cloud at similar evolutionary stages can exhibit different correlations between observing wavelength and polarization morphology and fraction. We explore possible origins for these differences in polarization, including differences in dust populations and protostar properties. For RY Tau and MWC 480, which are consistent with scattering at both wavelengths, we present models of the scattering polarization from several dust grain size distributions. These models aim to reproduce two features of the observational results for these disks: (1) both disks have an observable degree of polarization at both wavelengths; and (2) the polarization fraction is higher at 3 mm than at 870 μm in the centers of the disks. For both disks, these features can be reproduced by a power-law distribution of spherical dust grains with a maximum radius of 200 μm and high optical depth. In MWC 480, we can also reproduce features (1) and (2) with a model containing large grains (a max = 490 μm) near the disk midplane and small grains (a max = 140 μm) above and below the midplane.

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Recent progress in theory and observational study of dust grain alignment and rotational disruption in star-forming regions

Cited by 13 publications

References 141 publications

SOFIA Observations of 30 Doradus. II. Magnetic Fields and Large-scale Gas Kinematics

SOFIA Observations of 30 Doradus. II. Magnetic Fields and Large-scale Gas Kinematics

Far-infrared polarization of the supernova remnant Cassiopeia A with SOFIA HAWC +

Protoplanetary Disk Polarization at Multiple Wavelengths: Are Dust Populations Diverse?

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