A Unified Model of Grain Alignment: Radiative Alignment of Interstellar Grains With Magnetic Inclusions

Hoang, Thiem; Lazarían, A.

doi:10.3847/0004-637x/831/2/159

Cited by 143 publications

(263 citation statements)

References 78 publications

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“…which yields the perfect alignment f (a) = 1 for large grains of a a align and adequately approximates the numerical results from Hoang & Lazarian (2016) as well as results from inverse modeling of starlight polarization (Hoang et al 2014;Hoang 2017). At t 1 days, dust grains are aligned by the diffuse interstellar radiation, so the maximum polarization at λ max is around 0.55 µm.…”

Section: Modeling Sne Polarizationsupporting

confidence: 81%

“…where C pol = Q pol πa 2 is the polarization cross-section with Q pol the polarization efficiency, and f (a) is the 1 Although carbonaceous grains are expected to be aligned via k-RAT mechanism (see Lazarian & Hoang 2018), their degree of alignment is not yet quantified, in contrast for silicate grains which have alignment degree quantified in Hoang & Lazarian (2016) using numerical simulations.…”

Section: Modeling Sne Polarizationmentioning

confidence: 99%

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Time-varying Extinction, Polarization, and Colors of Type Ia Supernovae due to Rotational Disruption of Dust Grains

Giang¹,

Hoang²,

Tram³

2020

ApJ

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Photometric and polarimetric observations toward type Ia supernovae (SNe Ia) frequently report an unusually low total-to-selective extinction ratio (R V < 2) and small peak wavelength of polarization (λ max < 0.4 µm). Recently, Hoang et al. proposed that the increase in the abundance of small grains relative to large grains near SNe Ia due to RAdiative Torque Disruption (RATD) can explain this puzzle. To test this scenario, we will perform detailed modeling of dust extinction and polarization of SNe Ia accounting for grain disruption by RATD and grain alignment by RAdiative Torques (RATs). For dust clouds at distance d < 4 pc from the source, we find that R V decreases rapidly from the standard value of 3.1 to ∼ 1.5 after a disruption time t disr < 40 days. We then calculate the observed SNe Ia light curve and find that the colors of SNe Ia would change with time due to time-varying extinction for dust clouds at distance d < 4 pc. We also calculate the wavelength-dependence polarization produced by grains aligned with the magnetic fields by RATs. We find that λ max decreases rapidly from ∼ 0.55 µm to ∼ 0.15 µm over an alignment time of t align < 10 days due to the enhanced alignment of small grains. By fitting the theoretical polarization curve with the Serkowski law, we find that the parameter K from the Serkowski law increases when large grains are disrupted by RATD which can explain the K vs. λ max data observed for SNe Ia. Finally, we discover an anti-correlation between K and R V which might already be supported by SNe Ia observational data. Our results demonstrate the important effect of rotational disruption of dust grains by radiative torques on the time-dependent extinction, polarization, and colors of SNe Ia.

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Section: Modeling Sne Polarizationsupporting

confidence: 81%

Section: Modeling Sne Polarizationmentioning

confidence: 99%

Time-varying Extinction, Polarization, and Colors of Type Ia Supernovae due to Rotational Disruption of Dust Grains

Giang¹,

Hoang²,

Tram³

2020

ApJ

Self Cite

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“…Within the hypothesis that grain polarization properties, including alignment, are homogeneous, the structure of the dust polarization sky reflects the structure of the magnetic field combined with that of matter. We assume that this hypothesis applies to the diffuse ISM where radiative torques provide a viable mechanism to align grains efficiently (Dolginov & Mitrofanov 1976;Andersson et al 2015;Hoang & Lazarian 2016).…”

Section: Astrophysical Frameworkmentioning

confidence: 99%

Statistical simulations of the dust foreground to cosmic microwave background polarization

Vansyngel

Boulanger

Ghosh

et al. 2017

A&A

101

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The characterization of the dust polarization foreground to the cosmic microwave background (CMB) is a necessary step toward the detection of the B-mode signal associated with primordial gravitational waves. We present a method to simulate maps of polarized dust emission on the sphere that is similar to the approach used for CMB anisotropies. This method builds on the understanding of Galactic polarization stemming from the analysis of Planck data. It relates the dust polarization sky to the structure of the Galactic magnetic field and its coupling with interstellar matter and turbulence. The Galactic magnetic field is modeled as a superposition of a mean uniform field and a Gaussian random (turbulent) component with a power-law power spectrum of exponent α M . The integration along the line of sight carried out to compute Stokes maps is approximated by a sum over a small number of emitting layers with different realizations of the random component of the magnetic field. The model parameters are constrained to fit the power spectra of dust polarization EE, BB, and T E measured using Planck data. We find that the slopes of the E and B power spectra of dust polarization are matched for α M = −2.5, an exponent close to that measured for total dust intensity but larger than the Kolmogorov exponent −11/3. The model allows us to compute multiple realizations of the Stokes Q and U maps for different realizations of the random component of the magnetic field, and to quantify the variance of dust polarization spectra for any given sky area outside of the Galactic plane. The simulations reproduce the scaling relation between the dust polarization power and the mean total dust intensity including the observed dispersion around the mean relation. We also propose a method to carry out multifrequency simulations, including the decorrelation measured recently by Planck, using a given covariance matrix of the polarization maps. These simulations are well suited to optimize component separation methods and to quantify the confidence with which the dust and CMB B-modes can be separated in present and future experiments. We also provide an astrophysical perspective on our phenomenological modeling of the dust polarization spectra.

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“…Here, we suggest that large grains of a ∼ 10−100 µm are likely reduced from the location of H 2 CO emission because of the decrease of gas density that facilitate RATD, such that self-scattering is reduced. But smaller grains can be radiatively aligned with the radiation direction (Lazarian & Hoang 2007a;Hoang & Lazarian 2016), producing an azimuthal polarization pattern (Tazaki et al 2017).…”

Section: Rotational Desorption Coms Snow-line and Dust Properties mentioning

confidence: 99%

Rotational Desorption of Ice Mantles from Suprathermally Rotating Grains around Young Stellar Objects

Hoang

Tram

2020

ApJ

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Ice mantles on dust grains play a central role in astrochemistry. Water and complex organic molecules (COMs) are thought to first form on the ice mantles and subsequently are released into the gas phase due to star formation activity. However, the critical question is whether ice mantles can survive stellar radiation when grains are being heated from T d ∼ 10 K to 100 K. In this paper, we first study the effect of suprathermal grain rotation driven by the intense radiation of young stellar objects (YSOs) on the ice mantles. We find that the entire ice mantles can be disrupted into small fragments by centrifugal stress before the water ice and COMs desorb via thermal sublimation. We then study the consequence of resulting ice fragments and find that tiny fragments of radius a 10Å exhibit transient release of COMs due to thermal spikes, whereas larger fragments can facilitate thermal sublimation at much higher rates than from the original icy grain or the same rate but with temperatures of ∼ 20 − 40 K lower. We find that rotational desorption is efficient for hot cores/corinos from the inner to outer regions where the temperature drops to T gas ∼ 40 K and n H ∼ 10 4 cm −3 . We discuss the implications of this mechanism for desorption of COMs and water ice in various environments, including outflow cavity walls, photodissociation regions, and protoplanetary disks. Finally, we show that very large aggregate grains can be disrupted into individual icy grains via rotational disruption mechanism, followed by rotational desorption of ice mantles.

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A Unified Model of Grain Alignment: Radiative Alignment of Interstellar Grains With Magnetic Inclusions

Cited by 143 publications

References 78 publications

Time-varying Extinction, Polarization, and Colors of Type Ia Supernovae due to Rotational Disruption of Dust Grains

Time-varying Extinction, Polarization, and Colors of Type Ia Supernovae due to Rotational Disruption of Dust Grains

Statistical simulations of the dust foreground to cosmic microwave background polarization

Rotational Desorption of Ice Mantles from Suprathermally Rotating Grains around Young Stellar Objects

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