Modeling rotational disruption of grains and microwave emission from spinning dust in AGB envelopes

Abstract

Radio observations of some Asymptotic Giant Branch (AGB) star envelopes show the excess emission at frequencies below 100 GHz which cannot be explained by thermal dust emission (hereafter anomalous microwave emission-AME). Moreover, AGB envelopes are a common place where gas molecules condense to form nanoparticles (e.g., polycyclic aromatic hydrocarbons) and large grains. In this paper, we will study whether electric dipole emission from rapidly spinning nanoparticles can reproduce the AME observed toward AGB stars. To properly model the size distribution of nanoparticles in the AGB envelope, we take into account both the increase of nanoparticles due to rotational disruption of large grains spun-up by radiative torques and the decrease of smallest nanoparticles due to rotational disruption driven by stochastic gas collisions. We then perform detailed modeling of microwave emission from rapidly spinning nanoparticles from both C-rich and O-rich AGB envelopes using the grain size distribution constrained by rotational disruption. We find that spinning dust emission is dominant over thermal dust emission at frequencies below 100 GHz. We attempt to fit the observational data of AME using our spinning dust model and demonstrate that spinning dust can reproduce the observed AME in six AGB stars. Finally, we discuss that microwave emission from spinning dust in AGB envelopes could be observed with high-resolution upcoming radio telescopes such as ngVLA and ALMA Band 1. This would be a major leap for understanding AGB envelopes, formation, evolution, and internal structures of dust. Observations would help to distinguish the carrier of AME from comparing C-rich to O-rich stars, because PAHs are formed in C-rich AGB stars while silicates are formed in O-rich stars.

15 pages, 10 figures, and 2 tables

References in corpus (18)

• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• Radiative torques: Analytical Model and Basic Properties
• Radiative torque alignment: Essential Physical Processes
• A refined model for spinning dust radiation
• Oxygen Chemistry in the Circumstellar Envelope of the Carbon-Rich Star IRC+10216
• Rotational Disruption of Dust Grains by Radiative Torques in Strong Radiation Fields
• Molecular shells in IRC+10216: tracing the mass loss history
• Modeling the Anomalous Microwave Emission with Spinning Nanoparticles: No PAHs Required
• A dynamical constraint on interstellar dust models from radiative torque disruption
• High-resolution observations of gas and dust around Mira using ALMA and SPHERE/ZIMPOL
• Radiative torques of irregular grains: Describing the alignment of a grain ensemble
• Continuum emission around AGB stars at 1.2 mm
• Radio continuum monitoring of the extreme carbon star IRC+10216
• Dust Rotational Dynamics in C-shocks: Rotational Disruption of Nanoparticles by Stochastic Mechanical Torques and Spinning Dust Emission
• Discovery of a Shell of Neutral Atomic Hydrogen Surrounding the Carbon Star IRC+10216
• Relativistic Gas Drag on Dust Grains and Implications
• ALMA observations of the "fresh" carbon-rich AGB star TX Piscium. The discovery of an elliptical detached shell
• Dust rotational dynamics in non-stationary shock: rotational disruption of nanoparticles by stochastic mechanical torques and spinning dust emission

Cited by in corpus (4)

• Millimeter-wave Point Sources from the 2500-square-degree SPT-SZ Survey: Catalog and Population Statistics
• Understanding polarized dust emission from $\rho$ Ophiuchi A in light of grain alignment and disruption by radiative torques
• Modeling extinction and reddening effects by circumstellar dust in the Betelgeuse envelope in the presence of radiative torque disruption
• Grain alignment and dust evolution physics with polarisation (GRADE-POL). I. Dust polarisation modelling for isolated starless cores