Vietnam Astrophysics Research Network

Our research aims to understand the effects of magnetic fields and dust in Star Formation and Stellar Feedback (SF2) by connecting the new frontier of dust physics (rotational dynamics) with magnetic fields and dust polarization. We will exploit the wealth of dust polarization provided by numerous powerful polarimetric telescopes, including JCMT/POL2, SOFIA/HAWC+, and ALMA to study Star Formation and Stellar Feedback and to probe fundamental dust physics.

Magnetic fields and dust properties in star-forming regions via dust polarization

Magnetic fields are believed to play an important role in the star-formation process. Dust polarization is a popular technique to study magnetic fields from the diffuse medium, to molecular clouds, to protostellar cores, to protoplanetary disks. Dust polarization in particular provides valuable information on dust properties (optical, magnetic) and dust dynamics. We will aim to

(1) Characterize the magnetic field morphology and strengths from large to small scales using multi-wavelength polarimetric data.

(2) Use dust polarization data to test basic dust physics and constrain dust properties, including grain alignment and disruption.

Radiative and Mechanical Feedback from Young Stars

Intense radiation and outflows from young stars can change the physical and chemical properties of the surrounding dust and gas. Traditionally, the effects of intense radiation and mechanical outflows on dust are studied by means of grain heating, radiation pressure, and sputtering. We will address the following scientific questions by exploiting at the effects of radiative torques and mechanical torques which govern rotational dynamics of dust grains:

(1) What is the effects of stellar feedback on alignment of dust grains? Such grain alignment induces dust polarization that can allow us study magnetic fields in very dense regions around young stars where grain alignment is lost without stellar radiation.

(2) What is the effect of stellar feedback on grain disruption that changes the grain size distribution?

(3) What is the effect of grain suprathermal rotation by radiative and mechanical torques on grain surface chemistry?

(4) What is the effects of shocks induced by stellar outflows on the dust and gas?

Magnetic Fields and Radiative Feedback from Evolved Stars

Magnetic fields in the envelope of evolved stars. Magnetic fields are thought to affect the outflows. We will study magnetic fields in the envelope of evolved stars via aligned dust grains and resulting dust polarization.

Radiative feedback from AGB and super-red giant (SRG) stars. Material ejected from AGB/RSG stars allow dust to form (aka stardust) in the dust formation zone within 10 stellar radii. When being expelled into the interstellar medium, stardust would evolve under the effect of radiative and stellar feedback. Because the AGB/RSG temperature is low, causing a lack of UV photons available that can trigger mid-IR emission of PAHs. The spinning dust emission from rapidly spinning nanoparticles at frequencies below 100 GHz is believed to help to understand the formation of dust in AGB envelopes. Intense radiation from the central stars can change the properties of stardust due to rotational disruption by radiative torques. Furthermore, the polarimetric observations at optical/NIR and FIR wavelengths from AGB envelopes opens the possibility to study the grain growth in these media. In this project, we study the link between the mass-loss mechanism, grain formation and evolution in AGB/RSG envelopes.

Supernova and Black Hole Feedback

Supernova (SN) explosions and Accreting Black Holes inject huge kinetic energy and radiation into the surrounding environment, which dramatically change the dust and gas properties. We will study three questions:

(1) What is the effect of radiative torques by supernova radiation on alignment and disruption of surrounding dust, including newly formed dust and interstellar dust?

(2) What is the effect of the varying dust properties by supernova feedback on observations of SNe as standard candles of SNe cosmology?

(3) What is the effect of radiative feedback from accretion onto black holes (also, AGN) on surrounding dust and gas?

Observational Facilities

SOFIA

JCMT

air-ballon

ALMA

Questions?

Contact thiemhoang@kasi.re.kr or nle@usra.edu to get more information on the project