Paramagnetic Alignment of Small Grains: A Novel Method for Measuring Interstellar Magnetic Fields

Hoang, Thiem; Lazarían, A.; Martín, P. G.

doi:10.1088/0004-637x/790/1/6

Cited by 40 publications

(54 citation statements)

References 85 publications

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“…The favorable estimates for the alignment of very small grains, discussed below, therefore make the idea of paramagnetic alignment attractive in this case. Hoang et al (2014) showed that the enhanced alignment of small grains, required to explain the UV observations, could be achieved through alignment by paramagnetic relaxation under the assumption of an increased magnetic field strength. They derive an upper limit for the required interstellar magnetic field of B ∼ 10 μG for the typical ISM regions in which λ max = 0.55 μm.…”

Section: Paramagnetic Alignment Of Small Grainsmentioning

confidence: 99%

“…Nevertheless, for sufficiently small grains, RAT alignment is less efficient than paramagnetic alignment such that the DG mechanism may be necessary to account for grain alignment (Lazarian & Draine 2000;Hoang et al 2013Hoang et al , 2014.…”

Section: Alignment By Paramagnetic Relaxationmentioning

confidence: 99%

“…As the small-grain paramagnetic alignment is predicted to depend on the magnetic field strength, it may, in conjunction with observational parameters such as p max , λ max , and p UV , provide another observational method for constraining the field strength (Hoang et al 2014). This method would be complementary to other techniques for constraining the interstellar magnetic field, such as the Zeeman effect (e.g., Crutcher et al 2009), the Davis-Chandrasekhar-Fermi method (e.g., Houde et al 2009), and atomic alignment (e.g., Yan & Lazarian 2015).…”

Section: Paramagnetic Alignment Of Small Grainsmentioning

confidence: 99%

“…Small sheets of graphene (equivalent to large PAHs) have recently been predicted to display significant Pauli paramagnetism (Ominato & Koshino 2012), which may yield sufficient Barnett magnetization to allow RAT alignment. Paramagnetic alignment (and resonance paramagnetic alignment) may also become efficient for the very small grain carriers of the 2175-Å bump (Hoang et al 2014; Section 2.1.3). Observational tests of such alignment must be analyzed in the context of the mechanism in which PAH molecules can show polarized emission near a strong UV source owing to their orientation-dependent absorption cross section , Sironi & Draine 2009).…”

Section: The Effects Of Mineralogymentioning

confidence: 99%

See 3 more Smart Citations

Interstellar Dust Grain Alignment

Andersson

Lazarían

Vaillancourt

2015

Annu. Rev. Astron. Astrophys.

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458

420

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Interstellar polarization at optical-to-infrared wavelengths is known to arise from asymmetric dust grains aligned with the magnetic field. This effect provides a potentially powerful probe of magnetic field structure and strength if the details of the grain alignment can be reliably understood. Theory and observations have recently converged on a quantitative, predictive description of interstellar grain alignment based on radiative processes. The development of a general, analytical model for this radiative alignment torque (RAT) theory has allowed specific, testable predictions for realistic interstellar conditions. We outline the theoretical and observational arguments in favor of RAT alignment, as well as reasons the "classical" paramagnetic alignment mechanism is unlikely to work, except possibly for the very smallest grains. With further detailed characterization of the RAT mechanism, grain alignment and polarimetry promises to not only better constrain the interstellar magnetic field but also provide new information on the dust characteristics. 501

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Section: Paramagnetic Alignment Of Small Grainsmentioning

confidence: 99%

Section: Alignment By Paramagnetic Relaxationmentioning

confidence: 99%

Section: Paramagnetic Alignment Of Small Grainsmentioning

confidence: 99%

Section: The Effects Of Mineralogymentioning

confidence: 99%

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Interstellar Dust Grain Alignment

Andersson

Lazarían

Vaillancourt

2015

Annu. Rev. Astron. Astrophys.

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458

420

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“…Therefore, it is possible that the anomalous behaviour we report is telling us something about the chemical evolutionary state of the galaxy, or areas of the galaxy, in which the explosions occur. We must also take grain growth by accretion and coagulation (Voshchninnikov & Hirashita 2014) and alignment mechanisms (radiation and paramagnetic) on small dust grains (see for instance Hoang et al 2014) into account.…”

Section: Alternative Explanationsmentioning

confidence: 99%

Properties of extragalactic dust inferred from linear polarimetry of Type Ia Supernovae

Patat

Taubenberger

Cox

et al. 2015

A&A

136

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Aims. The aim of this paper is twofold: 1) to investigate the properties of extragalactic dust and compare them to what is seen in the Galaxy; 2) to address in an independent way the problem of the anomalous extinction curves reported for reddened Type Ia Supernovae (SN) in connection to the environments in which they explode. Methods. The properties of the dust are derived from the wavelength dependence of the continuum polarization observed in four reddened Type Ia SN: 1986G, 2006X, 2008fp, and 2014J. The method is based on the observed fact that Type Ia SN have a negligible intrinsic continuum polarization. This and their large luminosity makes them ideal tools to probe the dust properties in extragalactic environments.Results. All four objects are characterized by exceptionally low total-to-selective absorption ratios (R V ) and display an anomalous interstellar polarization law, characterized by very blue polarization peaks. In all cases the polarization position angle is well aligned with the local spiral structure. While SN 1986G is compatible with the most extreme cases of interstellar polarization known in the Galaxy, SN 2006X, 2008fp, and 2014J show unprecedented behaviours. The observed deviations do not appear to be connected to selection effects related to the relatively large amounts of reddening characterizing the objects in the sample. Conclusions. The dust responsible for the polarization of these four SN is most likely of interstellar nature. The polarization properties can be interpreted in terms of a significantly enhanced abundance of small grains. The anomalous behaviour is apparently associated with the properties of the galactic environment in which the SN explode, rather than with the progenitor system from which they originate. For the extreme case of SN 2014J, we cannot exclude the contribution of light scattered by local material; however, the observed polarization properties require an ad hoc geometrical dust distribution.

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Ultraviolet spectropolarimetry with polstar: interstellar medium science

Andersson

Clayton

Doney

et al. 2022

Astrophys Space Sci

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Continuum polarization over the UV-to-microwave range is due to dichroic extinction (or emission) by asymmetric, aligned dust grains. Scattering can also be an important source of polarization, especially at short wavelengths. Because of both grain alignment and scattering physics, the wavelength dependence of the polarization, generally, traces the size of the aligned grains. Similarly because of the differing wavelength dependencies of dichroic extinction and scattering polarization, the two can generally be reliably separated. Ultraviolet (UV) polarimetry therefore provides a unique probe of the smallest dust grains (diameter$< 0.09~\upmu \text{m}$ < 0.09 μm ), their mineralogy and interaction with the environment. However, the current observational status of interstellar UV polarization is very poor with less than 30 lines of sight probed. With the modern, quantitative and well-tested, theory of interstellar grain alignment now available, we have the opportunity to advance the understanding of the interstellar medium (ISM) by executing a systematic study of the UV polarization in the ISM of the Milky Way and near-by galaxies. The Polstar mission will provide the sensitivity and observing time needed to carry out such a program (probing hundreds of stars in the Milky Way and dozens of stars in the LMC/SMC), addressing questions of dust composition as a function of size and location, radiation- and magnetic-field characteristics as well as unveiling the carrier of the 2175 Å extinction feature. In addition, using high-resolution UV line spectroscopy Polstar will search for and probe the alignment of, and polarization from, aligned atoms and ions - so called “Ground State Alignment”, a potentially powerful new probe of magnetic fields in the diffuse ISM.

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Paramagnetic Alignment of Small Grains: A Novel Method for Measuring Interstellar Magnetic Fields

Cited by 40 publications

References 85 publications

Interstellar Dust Grain Alignment

Interstellar Dust Grain Alignment

Properties of extragalactic dust inferred from linear polarimetry of Type Ia Supernovae

Ultraviolet spectropolarimetry with polstar: interstellar medium science

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