DETECTION OF LINEARLY POLARIZED 6.9 mm CONTINUUM EMISSION FROM THE CLASS 0 YOUNG STELLAR OBJECT NGC 1333 IRAS4A

Liu, Hauyu Baobab; Lai, Shih-Ping; Hasegawa, Yasuhiro; Hirano, Naomi; Rao, Ramprasad; Li, I-Hsiu; Fukagawa, Misato; Girart, J. M.; Carrasco-González, Carlos; Rodrı́guez, Luis F.

doi:10.3847/0004-637x/821/1/41

Cited by 27 publications

(25 citation statements)

References 55 publications

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“…We report a similar two-lobe structure for the first time in NGC 1333 IRAS4B and detect peaks of polarization intensity on each side of the north-south outflow. Liu et al (2016) have found that the polarization intensity of NGC 1333 IRAS4A observed at 6.9 mm has a more typical distribution in which the polarization intensity peaks toward the source center; these authors have attributed this variation of the polarization distribution with wavelength to optical depth effects. Our temperature brightnesses rather suggest that the 0.87 mm emission is optically thin at the envelope scales probed in this paper, for all our objects.…”

Section: Potential Causes For Depolarizationmentioning

confidence: 99%

SMA observations of polarized dust emission in solar-type Class 0 protostars: Magnetic field properties at envelope scales

Galametz

Maury

Girart

et al. 2018

A&A

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Aims. Although from a theoretical point of view magnetic fields are believed to play a significant role during the early stages of star formation, especially during the main accretion phase, the magnetic field strength and topology is poorly constrained in the youngest accreting Class 0 protostars that lead to the formation of solar-type stars. Methods. We carried out observations of the polarized dust continuum emission with the SMA interferometer at 0.87 mm to probe the structure of the magnetic field in a sample of 12 low-mass Class 0 envelopes in nearby clouds, including both single protostars and multiple systems. Our SMA observations probed the envelope emission at scales ∼600 − 5000 au with a spatial resolution ranging from 600 to 1500 au depending on the source distance. Results. We report the detection of linearly polarized dust continuum emission in all of our targets with average polarization fractions ranging from 2% to 10% in these protostellar envelopes. The polarization fraction decreases with the continuum flux density, which translates into a decrease with the H 2 column density within an individual envelope. Our analysis show that the envelope-scale magnetic field is preferentially observed either aligned or perpendicular to the outflow direction. Interestingly, our results suggest for the first time a relation between the orientation of the magnetic field and the rotational energy of envelopes, with a larger occurrence of misalignment in sources in which strong rotational motions are detected at hundreds to thousands of au scales. We also show that the best agreement between the magnetic field and outflow orientation is found in sources showing no small-scale multiplicity and no large disks at ∼100 au scales.

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Section: Potential Causes For Depolarizationmentioning

confidence: 99%

SMA observations of polarized dust emission in solar-type Class 0 protostars: Magnetic field properties at envelope scales

Galametz

Maury

Girart

et al. 2018

A&A

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“…In addition, highresolution VLA observations revealed that the well-studied low-mass Class 0 protostar NGC 1333 IRAS 4A is significantly polarized at 8 mm, again with the near side brighter than the far side in polarized intensity Liu et al 2016). The source is so bright that it is believed to be optically thick out to 7 mm (Liu et al 2016), which is consistent with the interpretation that the polarization comes from scattering, at least near the center (see also Yang et al 2016b). Although it is conceivable that in each of the sources the asymmetry could be produced by an intrinsic feature on the disk, such a dust trap, it is statistically unlikely for such a trap to occur on the near side for all three cases.…”

Section: Evolution Of Dust Settling From Polarization Of Inclined Disksmentioning

confidence: 99%

“…The initial searches for disk polarization yielded only upper limits (Hughes et al 2009(Hughes et al , 2013. These were soon followed by detections in IRAS 16293B (Rao et al 2014) using the Submillimeter Array (SMA), in HL Tau (Stephens et al 2014), L1527 (Segura- Cox et al 2015), and Cepheus A HW2 (Fernández-López et al 2016) using the Combined Array for Research in Millimeter-wave Astronomy (CARMA), and in NGC 1333 IRAS 4A at 8 mm and 1 cm Liu et al 2016) using the Karl G. Jansky Very Large Array (VLA). Most excitingly, there are a large number of approved disk polarization programs using Atacama Large Millimeter/submillimeter Array (ALMA), with some results already published (Kataoka et al 2016b) and several more in preparation (e.g., J. M. Girart, in prep).…”

Section: Introductionmentioning

confidence: 99%

Scattering-produced (sub)millimetre polarization in inclined discs: optical depth effects, near–far side asymmetry and dust settling

Yang

Looney

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Disk polarization at (sub)millimeter wavelengths is being revolutionized by ALMA observationally, but its origin remains uncertain. Dust scattering was recently recognized as a potential contributor to polarization, although its basic properties have yet to be thoroughly explored. Here, we quantify the effects of optical depth on the scattering-induced polarization in inclined disks through a combination of analytical illustration, approximate semi-analytical modeling using formal solution to the radiative transfer equation, and Monte Carlo simulations. We find that the near-side of the disk is significantly brighter in polarized intensity than the far-side, provided that the disk is optically thick and that the scattering grains have yet to settle to the midplane. This asymmetry is the consequence of a simple geometric effect: the near-side of the disk surface is viewed more edge-on than the far-side. It is a robust signature that may be used to distinguish the scattering-induced polarization from that by other mechanisms, such as aligned grains. The asymmetry is weaker for a geometrically thinner dust disk. As such, it opens an exciting new window on dust settling. We find anecdotal evidence from dust continuum imaging of edge-on disks that large grains are not yet settled in the youngest (Class 0) disks, but become more so in older disks. This trend is corroborated by the polarization data in inclined disks showing that younger disks have more pronounced near-far side asymmetry and thus less grain settling. If confirmed, the trend would have far-reaching implications for grain evolution and, ultimately, the formation of planetesimals and planets.

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“…Chapman et al 2013;Hull et al 2013;Zhang et al 2014;Cox et al 2015;Ching et al 2016;Liu et al 2016;Planck Collaboration Int. XXXIII 2016, also see H.-B.…”

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confidence: 99%

Change of Magnetic Field-Gas Alignment at the Gravity-Driven Alfvénic Transition in Molecular Clouds: Implications for Dust Polarization Observations

Chen

King

2016

ApJ

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Diffuse striations in molecular clouds are preferentially aligned with local magnetic fields whereas dense filaments tend to be perpendicular to them. When and why this transition occurs remain uncertain. To explore the physics behind this transition, we compute the histogram of relative orientation (HRO) between the density gradient and the magnetic field in 3D MHD simulations of prestellar core formation in shock-compressed regions within GMCs. We find that, in the magnetically-dominated (sub-Alfvénic) post-shock region, the gas structure is preferentially aligned with the local magnetic field. For overdense sub-regions with super-Alfvénic gas, their elongation becomes preferentially perpendicular to the local magnetic field instead. The transition occurs when self-gravitating gas gains enough kinetic energy from the gravitational acceleration to overcome the magnetic support against the cross-field contraction, which results in a power-law increase of the field strength with density. Similar results can be drawn from HROs in projected 2D maps with integrated column densities and synthetic polarized dust emission. We quantitatively analyze our simulated polarization properties, and interpret the reduced polarization fraction at high column densities as the result of increased distortion of magnetic field directions in trans-or super-Alfvénic gas. Furthermore, we introduce measures of the inclination and tangledness of the magnetic field along the line of sight as the controlling factors of the polarization fraction. Observations of the polarization fraction and angle dispersion can therefore be utilized in studying local magnetic field morphology in star-forming regions.

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DETECTION OF LINEARLY POLARIZED 6.9 mm CONTINUUM EMISSION FROM THE CLASS 0 YOUNG STELLAR OBJECT NGC 1333 IRAS4A

Cited by 27 publications

References 55 publications

SMA observations of polarized dust emission in solar-type Class 0 protostars: Magnetic field properties at envelope scales

SMA observations of polarized dust emission in solar-type Class 0 protostars: Magnetic field properties at envelope scales

Scattering-produced (sub)millimetre polarization in inclined discs: optical depth effects, near–far side asymmetry and dust settling

Change of Magnetic Field-Gas Alignment at the Gravity-Driven Alfvénic Transition in Molecular Clouds: Implications for Dust Polarization Observations

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