Spinning dust emission from ultrasmall silicates: emissivity and polarization spectrum

Abstract

Anomalous microwave emission (AME) is an important Galactic foreground of Cosmic Microwave Background (CMB) radiation. It is believed that the AME arises from rotational emission by spinning polycyclic aromatic hydrocarbons (PAHs) in the interstellar medium (ISM). In this paper, we assume that a population of ultrasmall silicate grains may exist in the ISM, and quantify rotational emissivity from these tiny particles and its polarization spectrum. We found that spinning silicate nanoparticles can produce strong rotational emission when those small grains follow a log-normal size distribution. The polarization fraction of spinning dust emission from tiny silicates increases with decreasing the dipole moment per atom ($\beta$) and can reach $P\sim 20\%$ for $\beta \sim 0.1$D at grain temperature of 60 K. We identify a parameter space $(\beta ,Y_{Si})$ for silicate nanoparticles in which its rotational emission can adequately reproduce both the observed AME and the polarization of the AME, without violating the observational constraints by the ultraviolet extinction and polarization of starlight. Our results reveal that rotational emission from spinning silicate may be an important source of the AME.

11 pages, 9 figures, submitted to ApJ

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• Modeling the Anomalous Microwave Emission with Spinning Nanoparticles: No PAHs Required
• Quantum Suppression of Alignment in Ultrasmall Grains: Microwave Emission from Spinning Dust will be Negligibly Polarized
• Polycyclic Aromatic Hydrocarbons, the Anomalous Microwave Emission, and Their Connection to the Cold Neutral Medium
• Interstellar Silicon Depletion and the Ultraviolet Extinction
• Dust Rotational Dynamics in C-shocks: Rotational Disruption of Nanoparticles by Stochastic Mechanical Torques and Spinning Dust Emission
• Investigation of the Origin of the Anomalous Microwave Emission in Lambda Orionis
• COMAP Early Science: VI. A First Look at the COMAP Galactic Plane Survey
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• Spinning dust emission from circumstellar disks and its role in excess microwave emission
• Interstellar Extinction and Elemental Abundances: Individual Sight Lines
• Resolved spectral variations of the centimetre-wavelength continuum from the rho Oph W photo-dissociation-region
• Rotational disruption of dust grains by mechanical torques for high-velocity gas-grain collisions
• Confirmation of Enhanced Long Wavelength Dust Emission in OMC 2/3
• Spinning nano-carbon grains: Viable origin for anomalous microwave emission
• Modeling rotational disruption of grains and microwave emission from spinning dust in AGB envelopes
• Resolved observations at 31 GHz of spinning dust emissivity variations in $\rho$ Oph
• BeyondPlanck XVI. Limits on Large-Scale Polarized Anomalous Microwave Emission from Planck LFI and WMAP
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• Where's the Dust?: The Deepening Anomaly of Microwave Emission in NGC 4725 B
• Thermal emission from the amorphous dust: An alternative possibility of the origin of the anomalous microwave emission
• Effect of alignment on polarized infrared emission from polycyclic aromatic hydrocarbons
• Tracing PAH Emission in $\lambda$-Orionis Using COBE/DIRBE Data
• Modeling Long-Wavelength Amorphous Dust Emission Based on the Physically Motivated Soft-Potential Model