Modeling the Anomalous Microwave Emission with Spinning Nanoparticles: No PAHs Required

Hensley, Brandon; Draine, B. T.

doi:10.3847/1538-4357/aa5c37

Cited by 79 publications

(103 citation statements)

References 67 publications

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“…The leading explanation for AME is rotational emission from ultra-small (a 1 nm) dust grains (i.e., "spinning dust"), which was first postulated by Erickson (1957). In this model, rapidly rotating very small grains with non-zero electric dipole moments produce the ob-served microwave emission (Draine & Lazarian 1998;Planck Collaboration et al 2011;Hensley & Draine 2017). Magnetic dipole radiation from thermal fluctuations in the magnetization of interstellar dust grains (Draine & Lazarian 1999;Draine & Hensley 2013), may also be contributing to observed AME, particularly at higher frequencies ( 50 GHz).…”

Section: Introductionmentioning

confidence: 99%

A New Detection of Extragalactic Anomalous Microwave Emission in a Compact, Optically Faint Region of NGC 4725

Murphy

Linden

Dong

et al. 2018

ApJ

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We discuss the nature of a discrete, compact radio source (NGC 4725 B) located ≈1.9 kpc from the nucleus in the nearby star-forming galaxy NGC 4725, which we believe to be a new detection of extragalactic Anomalous Microwave Emission (AME). Based on detections at 3, 15, 22, 33, and 44 GHz, NGC 4725 B is a µJy radio source peaking at ≈33 GHz. While the source is not identified in BV RI photometry, we detect counterparts in the mid-infrared Spitzer/IRAC bands (3.6, 4.5, 5.8, 8.0 µm) that appear to be associated with dust emission in the central region of NGC 4725. Consequently, we conclude that NGC 4725 B is a new detection of AME, and very similar to a recent detection of AME in an outer-disk star-forming region in NGC 6946. We find that models of electric dipole emission from rapidly rotating ultra-small grains are able to reproduce the radio spectrum for reasonable interstellar medium conditions. Given the lack of an optical counterpart and the shape of the radio spectrum, NGC 4725 B appears consistent with a nascent star-forming region in which young ( 3 Myr) massive stars are still highly enshrouded by their natal cocoons of gas and dust with insufficient supernovae occurring to produce a measurable amount of synchrotron emission.

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Section: Introductionmentioning

confidence: 99%

A New Detection of Extragalactic Anomalous Microwave Emission in a Compact, Optically Faint Region of NGC 4725

Murphy

Linden

Dong

et al. 2018

ApJ

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“…Hoang et al (2016) and Hensley & Draine (2017a) argued that the so-called "anomalous microwave emission" (AME), an important Galactic foreground of the cosmic microwave background radiation in the ∼ 10-100 GHz region, could arise from spinning nano-sized silicate grains. However, silicate nanoparticles will undergo single-photon heating in the ISM and emit at the 9.7 µm Si-O feature.…”

Section: Introductionmentioning

confidence: 99%

Interstellar Silicon Depletion and the Ultraviolet Extinction

Mishra

2017

ApJ

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Spinning small silicate grains were recently invoked to account for the Galactic foreground anomalous microwave emission. These grains, if present, will absorb starlight in the far ultraviolet (UV). There is also renewed interest in attributing the enigmatic 2175Å interstellar extinction bump to small silicates. To probe the role of silicon in the UV extinction, we explore the relations between the amount of silicon required to be locked up in silicates [Si/H] dust and the 2175Å bump or the far-UV extinction rise, based on an analysis of the extinction curves along 46 Galactic sightlines for which the gas-phase silicon abundance [Si/H]

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“…It has been demonstrated that this is not always the case, and that AME correlates better with the total far-infrared radiance than with the Planck 353 GHz optical depth (Hensley et al 2016). This result was taken as evidence that polycyclic aromatic hydrocarbons (PAHs) are not necessarily the dominant source of spinning grain emission, and that instead nanosilicates (with a minor contribution from iron nanoparticles) could be responsible for the bulk of AME (Hensley & Draine 2017). Specifically for the Crab, we do not find a correlation between the dust mass column density (see Fig.6, bottom left panel) and the location of the mm excess emission (see Fig.8, right column).…”

Section: Appendix D: Alternative Explanations For the MM Excess Emissmentioning

confidence: 99%

The dust content of the Crab Nebula

Looze

Barlow

Bandiera

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We have modelled the near-infrared to radio images of the Crab Nebula with a Bayesian SED model to simultaneously fit its synchrotron, interstellar and supernova dust emission. We infer an interstellar dust extinction map with an average A V = 1.08 ± 0.38 mag, consistent with a small contribution ( 22%) to the Crab's overall infrared emission. The Crab's supernova dust mass is estimated to be between 0.032 and 0.049 M (for amorphous carbon grains) with an average dust temperature T dust =41±3 K, corresponding to a dust condensation efficiency of 8-12%. This revised dust mass is up to an order of magnitude lower than some previous estimates, which can be attributed to our different interstellar dust corrections, lower SPIRE flux densities, and higher dust temperatures than were used in previous studies. The dust within the Crab is predominantly found in dense filaments south of the pulsar, with an average V band dust extinction of A V = 0.20 − 0.39 mag, consistent with recent optical dust extinction studies. The modelled synchrotron power-law spectrum is consistent with a radio spectral index α radio =0.297±0.009 and an infrared spectral index α IR =0.429±0.021. We have identified a millimetre excess emission in the Crab's central regions, and argue that it most likely results from two distinct populations of synchrotron emitting particles. We conclude that the Crab's efficient dust condensation (8-12%) provides further evidence for a scenario where supernovae can provide substantial contributions to the interstellar dust budgets in galaxies.

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Modeling the Anomalous Microwave Emission with Spinning Nanoparticles: No PAHs Required

Cited by 79 publications

References 67 publications

A New Detection of Extragalactic Anomalous Microwave Emission in a Compact, Optically Faint Region of NGC 4725

A New Detection of Extragalactic Anomalous Microwave Emission in a Compact, Optically Faint Region of NGC 4725

Interstellar Silicon Depletion and the Ultraviolet Extinction

The dust content of the Crab Nebula

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