The Far-infrared Polarization Spectrum of <i>ρ</i> Ophiuchi A from HAWC+/SOFIA Observations

Santos, Fábio P.; Chuss, David T.; Dowell, C. D.; Houde, Martin; Looney, Leslie W.; Rodriguez, Enrique Lopez; Novak, Giles; Ward-Thompson, Derek; Berthoud, Marc; Dale, Daniel A.; Guerra, Jordan A.; Hamilton, Ryan; Hanany, Shaul; Harper, D. A.; Henning, Thomas; Jones, T. J.; Lazarían, A.; Michail, Joseph M.; Morris, Mark; Staguhn, Johannes; Stephens, Ian; Tassis, Konstantinos; Trinh, Christopher; Camp, Eric Van; Volpert, Carolyn G.; Wollack, Edward J.

doi:10.3847/1538-4357/ab3407

Cited by 39 publications

(39 citation statements)

References 96 publications

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“…To achieve a thorough understanding of the filament formation process, we should aim at making direct observations of the B-field in the ISM with column densities down to 10 21 cm −2 at high spatial resolution. HAWC+ on board SOFIA pioneers polarimetry of low column density gas around bright star-forming regions (e.g., Chuss et al 2019;Santos et al 2019). Extensive observations can be conducted by future space-borne facilities (e.g., André et al 2019;Leisawitz et al 2019).…”

Section: Discussionmentioning

confidence: 99%

The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in NGC 1333

Doi¹,

Hasegawa

Furuya

et al. 2020

ApJ

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We present new observations of the active star formation region NGC 1333 in the Perseus molecular cloud complex from the James Clerk Maxwell Telescope B-Fields In Star-forming Region Observations (BISTRO) survey with the POL-2 instrument. The BISTRO data cover the entire NGC 1333 complex (∼1.5 pc×2 pc) at 0.02 pc resolution and spatially resolve the polarized emission from individual filamentary structures for the first time. The inferred magnetic field structure is complex as a whole, with each individual filament aligned at different position angles relative to the local field orientation. We combine the BISTRO data with low-and high-resolution data derived from Planck and interferometers to study the multiscale magnetic field structure in this region. The magnetic field morphology drastically changes below a scale of ∼1 pc and remains continuous from the scales of filaments (∼0.1 pc) to that of protostellar envelopes (∼0.005 pc or ∼1000 au). Finally, we construct simple models in which we assume that the magnetic field is always perpendicular to the long axis of the filaments. We demonstrate that the observed variation of the relative orientation between the filament axes and the magnetic field angles are well reproduced by this model, taking into account the projection effects of the magnetic field and filaments relative to the plane of the sky. These projection effects may explain the apparent complexity of the magnetic field structure observed at the resolution of BISTRO data toward the filament network.

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Section: Discussionmentioning

confidence: 99%

The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in NGC 1333

Doi¹,

Hasegawa

Furuya

et al. 2020

ApJ

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“…Observations have reported an anticorrelation trend of the fractional polarization of thermal dust emission with the column density of the gas in molecular clouds (e.g., Arce et al 1998;Whittet et al 2008;Planck Collaboration et al 2015, 2020Fissel et al 2016;Santos et al 2017Santos et al , 2019Chuss et al 2019). This trend is explained by the loss of grain alignment toward dense cores (Whittet et al 2008;Hoang et al 2020) or by the turbulent structure of magnetic field within the scale of the beam size (see Jones & Whittet 2015;Planck Collaboration et al 2015).…”

Section: Introductionmentioning

confidence: 97%

“…For example, Planck Collaboration et al (2020) showed that the 40′ spatial resolution polarization degree at 850 μm, measured by the Planck satellite toward five molecular regions, including Aquila Rift, Cham-Musca, Orion, and Ophiuchus in the Gould belt cloud, decreases for T d >19 K (see their Figure 18). Additionally, far-infrared polarimetric data observed by the High-resolution Airborne Wide band Camera Plus (HAWC+) instrument (Harper et al 2018) on board the Stratosphere Observatory for Infrared Astronomy (SOFIA) toward the molecular cloud Ophiuchus A (Santos et al 2019) at 89 μm (7 8 spatial resolution) and 154 μm (13 6 spatial resolution) also reported the decrease of the polarization degree for T d >25-32 K (see Section 2 below). These observational features are challenging the popular RAT alignment theory.…”

Section: Introductionmentioning

confidence: 99%

“…Coming back to the SOFIA/HAWC+ observation toward ρ Oph-A at bands C (89 μm) and D (154 μm) as mentioned above, Santos et al (2019) mainly studied the variation of the ratio of the polarization degree (P D (%)/P C (%)) with respect to the dust temperature, which is opposed to the polarization degree studies. Furthermore, the authors showed that the RATs mechanism was able to explain the increasing (e.g., positive) part of the ratio curve and discarded the decreasing (negative) part (see their Figure 6(d)).…”

Section: Introductionmentioning

confidence: 99%

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Understanding Polarized Dust Emission from ρ Ophiuchi A in Light of Grain Alignment and Disruption by Radiative Torques

Tram

Hoang

Lee

et al. 2021

ApJ

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The alignment of dust grains with the ambient magnetic field produces polarization of starlight as well as thermal dust emission. Using the archival SOFIA/HAWC+ polarimetric data observed toward the ρ Ophiuchus (Oph) A cloud hosted by a B star at 89 and 154 μm, we find that the fractional polarization of thermal dust emission first increases with the grain temperature and then decreases once the grain temperature exceeds ;25-32 K. The latter trend differs from the prediction of the popular RAdiative Torques (RATs) alignment theory, which implies a monotonic increase of the polarization fraction with the grain temperature. We perform numerical modeling of polarized dust emission for the ρ Oph-A cloud and calculate the degree of dust polarization by simultaneously considering the dust grain alignment and rotational disruption by RATs. Our modeling results could successfully reproduce both the rising and declining trends of the observational data. Moreover, we show that the alignment of only silicate grains or a mixture of silicate-carbon grains within a composite structure can reproduce the observational trends, assuming that all dust grains follow a power-law size distribution. Although there are a number of simplifications and limitations to our modeling, our results suggest grains in the ρ Oph-A cloud have a composite structure, and the grain size distribution has a steeper slope than the standard size distribution for the interstellar medium. Combination of SOFIA/HAWC+ data with JCMT observations 450 and 850μm would be useful to test the proposed scenario based on grain alignment and disruption by RATs.

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“…This makes it possible to observe the orientation of interstellar magnetic fields through polarimetry, as was, e.g., done by Planck (Planck Collaboration et al 2018) for the Milky Way. More recently, ALMA (Cortes et al 2016), the POL-2/SCUBA2 polarimeter on the JCMT (Pattle et al 2017), and the HAWC+ polarimeter on the SOFIA telescope (Santos et al 2019;Lopez-Rodriguez et al 2020) have started opening up a new level of magnetic field surveys by producing polarization maps for star-forming molecular clouds and external galaxies. Other polarimeters are being commissioned, e.g., the TolTEC instrument on the Large Millimeter Telescope (Bryan et al 2018), or are being proposed, e.g., the B-BOP polarimeter aboard the ESA/JAXA mission SPICA (Roelfsema et al 2018;André et al 2019).…”

Section: Introductionmentioning

confidence: 99%

CosTuuM: Polarized Thermal Dust Emission by Magnetically Oriented Spheroidal Grains

Vandenbroucke

Baes

Camps

2020

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We present the new open-source C++-based Python library COSTUUM that can be used to generate infrared absorption and emission coefficients for arbitrary mixtures of spheroidal dust grains that are (partially) aligned with a magnetic field. We outline the algorithms underlying the software, demonstrate the accuracy of our results using benchmarks from literature, and use our tool to investigate some commonly used approximative recipes. We find that the linear polarization fraction for a partially aligned dust grain mixture can be accurately represented by an appropriate linear combination of perfectly aligned grains and grains that are randomly oriented, but that the commonly used picket fence alignment breaks down for short wavelengths. We also find that for a fixed dust grain size, the absorption coefficients and linear polarization fraction for a realistic mixture of grains with various shapes cannot both be accurately represented by a single representative grain with a fixed shape, but that instead an average over an appropriate shape distribution should be used. Insufficient knowledge of an appropriate shape distribution is the main obstacle in obtaining accurate optical properties. COSTUUM is available as a standalone Python library and can be used to generate optical properties to be used in radiative transfer applications.

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The Far-infrared Polarization Spectrum of ρ Ophiuchi A from HAWC+/SOFIA Observations

Cited by 39 publications

References 96 publications

The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in NGC 1333

The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in NGC 1333

Understanding Polarized Dust Emission from ρ Ophiuchi A in Light of Grain Alignment and Disruption by Radiative Torques

CosTuuM: Polarized Thermal Dust Emission by Magnetically Oriented Spheroidal Grains

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