Dust rotational disruption is ubiquitous: Changing the current paradigms of dust evolution and surface chemistry in space

The Radiative Torque Disruption (RATD) mechanism reported in Nature Astronomy is applied to study the evolution of dust in various astrophysical environments; new effects of grain suprathermal rotation on surface chemistry are suggested; and observational evidence in support of RATD are reported.

About 16 months ago, we reported our discovery of a new mechanism of dust destruction (aka. Radiative Torque Disruption--RATD) in Nature Astronomy. Following our publication, significant progress has been made in dust evolution and surface chemistry. The RATD mechanism is applied to study the evolution of dust in various astrophysical environments. New effects of grain suprathermal rotation on surface chemistry are proposed. We find observational evidence in support of RATD and rotational desorption of complex molecules using dust polarization and chemical tracers.

First of all, let’s briefly recall the new dust destruction mechanism reported in our Nature Astronomy paper. A dust grain of irregular shape irradiated by a radiation beam from intense sources such as supernovae, massive stars, can be spun-up to extremely fast rotation (i.e., suprathermal rotation) by radiative torques. Centrifugal stress induced by suprathermal rotation can exceed the maximum tensile strength of the grain material, which disrupts the original grain into smaller fragments. This mechanism is named RAdiative Torque Disruption (RATD).

Application of RATD to new astrophysical environments. Since our discovery reported in Nature Astronomy, we applied the RATD mechanism to understand observational puzzles in various environments. We have applied RATD to study dust evolution in the diffuse interstellar medium (ISM, Hoang 2019) of our galaxy, the variation of grain size distribution with redshift (Hoang 2020), disruption of dust induced by transient sources such as SNe Ia (Giang et al. 2020a) and Gamma Ray Bursts (GRBs, Hoang et al. 2020); evolution of dust and ice in protoplanetary disks (PPDs, Tung & Hoang 2020) and comets (Hoang & Tung 2020), and in Active Galactic Nuclei (AGN, Giang et al. 2020b).

Discover new effects of grain suprathermal rotation on surface astrochemistry. We have introduced new mechanisms for rotational desorption of molecules from grain surface. Grain suprathermal rotation is found to enhance thermal desorption of molecules from ice mantles. Entire mantle can be desorbed by centrifugal stress. The centrifugal stress is found to enhance segregation and hopping of adsorbed molecules on the ice mantle, increasing the reaction rates on grain surface.

Found observational evidence of rotational disruption and molecule desorption. We have searched for observational evidence for RATD and successfully found evidence of RATD from dust polarization toward bright sources, including star-forming regions (Tram et al. 2020ab), SNe (Giang et al. 2020) and GRBs (Hoang et al. 2020), and even the ISM (Lee et al. 2020).

Recruitment of new team members. Thanks to a 4-year grant from National Research Foundation (NRF) awarded to research on the effects of rotational disruption/desorption, I can hire more postdocs and support three students. New collaboration with a young research group from Vietnam is established partly based on the work published in Nature Astronomy.

Finally, 17 papers are published or accepted to the top journals of astronomy and astrophysics (ApJ & MNRAS). More results are coming.

Papers published or accepted:

1. Thiem Hoang, Le Ngoc Tram, Hyeseung Lee, Pham Ngoc Diep, Nguyen Bao Ngoc, Grain alignment and disruption by radiative torques in dense molecular clouds and implication for polarization holes, 2020, accepted to ApJ
2. Thiem HoangVariation of dust properties with cosmic time implied by radiative torque disruption, 2020, ApJ, accepted
3. A. Lazarian, Thiem Hoang Alignment and Rotational Disruption of Dust, ApJ, accepted,
4. Le Ngoc Tram, Hyeseung Lee, Thiem Hoang et al.Observational evidence for rotational desorption of Complex Molecules by radiative torques from Orion BN/KL, ApJ, in press
5. Le Ngoc Tram, Thiem Hoang et al.Understanding polarized dust emission from $\rho$ Ophiuchi A in light of grain alignment and disruption by radiative torques, ApJ, in press
6. Thiem Hoang, and Tung, Ngo Duy, Evolution of dust and water ice in cometary coma by radiative torques, 2020, 901, 59
7. Tung, Ngo Duy, Hoang, ThiemRotational Disruption of Dust and Ice by Radiative Torques in Protoplanetary Disks and Implications for Observations, 2020, ApJ, 901, 6
8. Thiem HoangRotational Disruption of Astrophysical Dust and Ice: Theory and Applications, Invited Review, Galaxies, 2020, 8, 52
9. Hirashita H, Thiem HoangEffects of rotational disruption on the evolution of grain size distribution in galaxies, 2020, MNRAS, 494, 1058
10. Thiem Hoang, Giang Nguyen Chau, Tram Le Ngoc, Gamma-ray Burst Afterglows: Time-Varying Extinction, Polarization, and Colors due to Rotational Disruption of Dust Grains, 2020, ApJ, 895, 16
11. Hyeseung Lee, Thiem Hoang, Le Ngan, and Jungyeon Cho, Physical Model of Dust Polarization by Radiative Torque Alignment and Disruption and Implications for Grain Internal Structures, 2020, ApJ, 896, 44
12. Tram Le Ngoc, Thiem Hoang, et al., Modeling rotational disruption of grains and microwave emission from spinning dust in AGB envelopes, 2020, ApJ, 893, 138
13. Giang Nguyen Chau, Thiem Hoang, Tram Le Ngoc, Time-Varying Extinction, Polarization, and Colors of Type Ia Supernovae due to Rotational Disruption of Dust Grains, 2020, ApJ, 888, 93
14. Thiem Hoang, Tram Le Ngoc, Rotational Desorption of Ice Mantles and Complex Molecules from Suprathermally Rotating Grains around YSOs, 2020, ApJ, 891, 38
15. Nguyen Bich Ngoc, Pham Ngoc Diep, H. Parsons, Kate Pattle, Thiem Hoang , et al., Observations of magnetic fields surrounding LkHα 101taken by the BISTRO survey with JCMT-POL-2, ApJ, accepted
16. Thiem Hoang, Ngo Duy Tung, Chemistry on Rotating Grain Surface: Ro-Thermal Desorption of Molecules from Ice Mantles, 2019, ApJ, 885, 125
17. Thiem HoangA dynamical constraint on interstellar dust models from radiative torque disruption, 2019, ApJ, 876, 13

Thiem Hoang

Senior Researcher/Professor, KASI