Panchromatic (Sub)millimeter polarization observations of HL Tau unveil aligned scattering grains

Lin, Zhe-Yu Daniel; Li, Zhi-Yun; Stephens, Ian W; Fernández-López, Manuel; Carrasco-González, Carlos; Chandler, Claire J; Pasetto, Alice; Looney, Leslie W; Yang, Haifeng; Harrison, Rachel E; Sadavoy, Sarah I; Henning, Thomas; Hughes, A Meredith; Kataoka, Akimasa; Kwon, Woojin; Muto, Takayuki; Segura-Cox, Dominique

doi:10.1093/mnras/stae040

Cited by 6 publications

(4 citation statements)

References 90 publications

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“…Here α = 0.1 is used to produce the small polarization degree of ∼2% as observed in the disk, which is optically thick in Band 7 and thus expected to have a polarization fraction significantly reduced from the maximum value. Interestingly, a similar α value has been adopted to reproduce the polarization images of HL Tau observed from ALMA Band 7 (Stephens et al 2023) to the VLA Q band (Lin et al 2024).…”

Section: Magnetically Aligned Grainsmentioning

confidence: 99%

“…In particular, the dust polarization due to dust self-scattering is affected by the asymmetry in the flux incoming from various directions, while the dust polarization due to the magnetically aligned grains is not. Recent dust polarization observations toward the well-studied HL Tau disk at a submillimeter wavelength of 870 μm have indeed shown that the rings and gaps in the disk have different polarization degrees and orientation, which can be attributed to both scattering and emission from the aligned grains (Stephens et al 2023;Lin et al 2024).…”

Section: Introductionmentioning

confidence: 99%

“…With the powerful Atacama Large Millimeter/submillimeter Array (ALMA), dust polarization has been detected toward quite a few protostellar disks in millimeter and submillimeter wavelengths over the past decade (e.g., Kataoka et al 2017;Stephens et al 2017Stephens et al , 2023Bacciotti et al 2018;Cox et al 2018;Girart et al 2018;Harris et al 2018;Hull et al 2018;Lee et al 2018Lee et al , 2021Dent et al 2019;Sadavoy et al 2019;Tang et al 2023;Lin et al 2024;Yang et al 2024). It could be due to magnetically aligned grains (Andersson et al 2015), dust selfscattering (Kataoka et al 2015;Yang et al 2016), or radiatively aligned grains (Kataoka et al 2017;Tazaki et al 2017), and more than one mechanism can be at work simultaneously, perplexing the analysis.…”

Section: Introductionmentioning

confidence: 99%

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Polarization Substructure in the Spiral-dominated HH 111 Disk: Evidence for Grain Growth

Lee,

Li,

Ching

et al. 2024

ApJL

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The HH 111 protostellar disk has recently been found to host a pair of spiral arms. Here we report the dust polarization results in the disk as well as the inner envelope around it, obtained with the Atacama Large Millimeter/submillimeter Array in continuum at λ ∼ 870 μm and ∼0.″05 resolution. In the inner envelope, polarization is detected with a polarization degree of ∼6% and an orientation almost everywhere parallel to the minor axis of the disk and thus likely to be due to the dust grains magnetically aligned mainly by toroidal fields. In the disk, the polarization orientation is roughly azimuthal on the far side and becomes parallel to the minor axis on the near side, with a polarization gap in between on the far side near the central protostar. The disk polarization degree is ∼2%. The polarized intensity is higher on the near side than the far side, showing a near–far side asymmetry. More importantly, the polarized intensity and thus polarization degree are lower in the spiral arms but higher in between the arms, showing an anticorrelation of the polarized intensity with the spiral arms. Our modeling results indicate that this anticorrelation is useful for constraining the polarization mechanism and is consistent with the dust self-scattering by the grains that have grown to a size of ∼150 μm. The interarms are sandwiched and illuminated by two brighter spiral arms and thus have higher polarized intensity. Our dust self-scattering model can also reproduce the observed polarization orientation parallel to the minor axis on the near side and the observed azimuthal polarization orientation at the two disk edges in the major axis. Further modeling work is needed to study how to reproduce the observed near–far side asymmetry in the polarized intensity and the observed azimuthal polarization orientation on the far side.

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Section: Magnetically Aligned Grainsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Polarization Substructure in the Spiral-dominated HH 111 Disk: Evidence for Grain Growth

Lee,

Li,

Ching

et al. 2024

ApJL

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“…HL Tauʼs polarization spectrum is particularly interesting: the diskʼs polarization morphology transitions from a pattern consistent with scattering at ∼870 μm to an elliptical pattern at ∼3 mm, with an intermediate pattern at ∼1.3 mm (Stephens et al 2017). Recently, Lin et al (2022) and Lin et al (2024) have demonstrated that HL Tauʼs polarization spectrum could be explained by polarization from thermal emission and the scattering of aligned grains, also demonstrating that the polarization seen at high resolution in HL Tau at 870 μm could be explained by the same mechanisms. At longer wavelengths, thermal polarization dominates because the low optical depth makes scattering inefficient.…”

Section: Introductionmentioning

confidence: 99%

Protoplanetary Disk Polarization at Multiple Wavelengths: Are Dust Populations Diverse?

Harrison,

Lin,

Looney

et al. 2024

ApJ

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Millimeter and submillimeter observations of continuum linear dust polarization provide insight into dust grain growth in protoplanetary disks, which are the progenitors of planetary systems. We present the results of the first survey of dust polarization in protoplanetary disks at 870 μm and 3 mm. We find that protoplanetary disks in the same molecular cloud at similar evolutionary stages can exhibit different correlations between observing wavelength and polarization morphology and fraction. We explore possible origins for these differences in polarization, including differences in dust populations and protostar properties. For RY Tau and MWC 480, which are consistent with scattering at both wavelengths, we present models of the scattering polarization from several dust grain size distributions. These models aim to reproduce two features of the observational results for these disks: (1) both disks have an observable degree of polarization at both wavelengths; and (2) the polarization fraction is higher at 3 mm than at 870 μm in the centers of the disks. For both disks, these features can be reproduced by a power-law distribution of spherical dust grains with a maximum radius of 200 μm and high optical depth. In MWC 480, we can also reproduce features (1) and (2) with a model containing large grains (a max = 490 μm) near the disk midplane and small grains (a max = 140 μm) above and below the midplane.

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Into the thick of it: ALMA 0.45 mm observations of HL Tau at a resolution of 2 au

Guerra-Alvarado,

Carrasco-González,

Macías

et al. 2024

A&A

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To comprehend the efficiency of dust evolution within protoplanetary disks, it is crucial to conduct studies of these disks using high-resolution observations at multiple wavelengths with the Atacama Large Millimeter/submillimeter Array (ALMA). In this work, we present high-frequency ALMA observations of the HL Tau disk using its Band 9 centered at a wavelength of 0.45 mm. These observations achieve the highest angular resolution in a protoplanetary disk to date, 12 milliarcseconds (mas), allowing the study of the dust emission at scales of 2 au. We used these data to extend the previously published multiwavelength analysis of the HL Tau disk, constraining the dust temperature, dust surface density, and maximum grain size throughout the disk. We performed this modeling for compact solid dust particles as well as for porous particles. Our new 0.45 mm data mainly trace optically thick emission, providing a tight constraint to the dust temperature profile. We derive maximum particle sizes of $ cm from the inner disk to $ au. Beyond this radius, we find particles between 300 mu m and 1 mm. The total dust mass of the disk is 2.1 J $ with compact grains, and it increases to 6.3 M$_ J $ assuming porous particles. Moreover, an intriguing asymmetry is observed at 32 au in the northeast inner part of the HL Tau disk at 0.45 mm. We propose that this asymmetry is the outcome of a combination of factors, including the optically thick nature of the emission, the orientation of the disk, and a relatively large dust scale height of the grains that is preferentially traced at 0.45 mm. To validate this, we conducted a series of radiative transfer models using the software RADMC-3D. Our models varying dust masses and scale heights successfully replicate the observed asymmetry in the HL Tau disk. If this scenario is correct, our measured dust mass within 32 au would suggest a dust scale height H/R$>0.08$ for the inner disk. Finally, the unprecedented resolution allowed us to probe the dust emission down to scales of a few au for the first time. We observed an increase in brightness temperature inside the estimated water snowline, and we speculate whether this might indicate a traffic-jam effect in the inner disk. Our results show that 0.45 mm observations of protoplanetary disks can be used to robustly constrain the radial profile of their dust temperature. Additionally, the higher optical depths at this wavelength can be used to constrain the vertical scale height of the dust. Finally, these higher frequencies allow us to reach higher spatial resolutions, which have the potential to resolve the region within the water snowline in disks.

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Panchromatic (Sub)millimeter polarization observations of HL Tau unveil aligned scattering grains

Cited by 6 publications

References 90 publications

Polarization Substructure in the Spiral-dominated HH 111 Disk: Evidence for Grain Growth

Polarization Substructure in the Spiral-dominated HH 111 Disk: Evidence for Grain Growth

Protoplanetary Disk Polarization at Multiple Wavelengths: Are Dust Populations Diverse?

Into the thick of it: ALMA 0.45 mm observations of HL Tau at a resolution of 2 au

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