Near-infrared polarimetric study of near-Earth object 252P/LINEAR: an implication of scattered light from the evolved dust particles

Kwon, Yuna G.; Ishiguro, Masateru; Kwon, Jinhyeong; Kuroda, D.; Im, Myungshin; Choi, Changsu; Tamura, Motohide; Nagayama, Takahiro; Kawai, N.; Watanabe, J.

doi:10.1051/0004-6361/201935542

Cited by 10 publications

(10 citation statements)

References 83 publications

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“…In contrast, the single wavelet of ∼2.2 µm can cover multiple monomers, enhancing mutual electromagnetic interaction (∝d −3 , where d is the distance between two neighbouring L7, page 4 of 11 dipole-like monomers; Jackson 1962), which makes observations more pertinent to how dust is organised in aggregates (i.e. bulk effects; Kolokolova & Kimura 2010;Kwon et al 2019). The apparent lack of a correlation in the red domain might thus tell us that the monomers' inherent characteristics are independent of porosity.…”

Section: Resultsmentioning

confidence: 99%

“…Numbers in the last column show references for the F Si /F cont , the carbon abundance, and the criteria for the classifications of gas-rich versus dust-rich comets. Polarimetric data are quoted from the NASA PDS database (Kiselev et al 2017) and the subsequent studies of Kwon et al (2017Kwon et al ( , 2018Kwon et al ( , 2019.…”

Section: Appendix A: Ancillary Information For the Comets Used For Analysismentioning

confidence: 99%

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An update of the correlation between polarimetric and thermal properties of cometary dust

Kwon

Kolokolova²,

Markkanen³

2021

A&A

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Context. Comets are conglomerates of ice and dust particles, the latter of which encode information on changes in the radiative and thermal environments. Dust displays distinctive scattered and thermal radiation in the visible and mid-infrared (MIR) wavelengths, respectively, based on its inherent characteristics. Aims. We aim to identify a possible correlation between the properties of scattered and thermal radiation from dust and the principal dust characteristics responsible for this relationship, and therefrom gain insights into comet evolution. Methods. We use the NASA/PDS archival polarimetric data on cometary dust in the red (0.62−0.73 μm) and K (2.00−2.39 μm) domains to leverage the relative excess of the polarisation degree of a comet to the average trend at the given phase angle (Pexcess) as a metric of the dust’s scattered light characteristics. The flux excess of silicate emissions to the continuum around 10 μm (FSi/Fcont) is adopted from previous studies as a metric of the dust’s MIR feature. Results. The two observables – Pexcess and FSi/Fcont – show a positive correlation when Pexcess is measured in the K domain (Spearman’s rank correlation coefficient ρ = 0.71−0.19+0.10). No significant correlation was identified in the red domain (ρ = 0.13−0.15+0.16). The gas-rich comets have systematically weaker FSi/Fcont than the dust-rich ones, and yet both groups retain the same overall tendency with different slope values. Conclusions. The observed positive correlation between the two metrics indicates that composition is a peripheral factor in characterising the dust’s polarimetric and silicate emission properties. The systematic difference in FSi/Fcont for gas-rich versus dust-rich comets would instead correspond to the difference in their dust size distribution. Hence, our results suggest that the current MIR spectral models of cometary dust, which search for a minimum χ2 fit by considering various dust properties simultaneously, should prioritise the dust size and porosity over the composition. With light scattering being sensitive to different size scales in two wavebands, we expect the K-domain polarimetry to be sensitive to the properties of dust aggregates, such as size and porosity, which might have been influenced by evolutionary processes. On the other hand, the red-domain polarimetry reflects the characteristics of sub-micrometre constituents in the aggregate.

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Section: Resultsmentioning

confidence: 99%

Section: Appendix A: Ancillary Information For the Comets Used For Analysismentioning

confidence: 99%

An update of the correlation between polarimetric and thermal properties of cometary dust

Kwon

Kolokolova²,

Markkanen³

2021

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…At a wavelength of ∼0.6 µm, monomers in aggregates have more or less similar dimensions with the incident wavelet (Güttler et al 2019), such that their individual characteristics define the scattering to a large extent. In contrast, the single wavelet of ∼2.2 µm can cover multiple monomers, enhancing mutual electromagnetic interaction (∝d −3 , where d is the distance between two neighbouring dipole-like monomers; Jackson 1962), which makes observations more pertinent to the way of dust organisation in aggregates, i.e., bulk effects (Kolokolova & Kimura 2010;Kwon et al 2019). The apparent lack of a correlation in the Red domain might thus tell us that the monomers' inherent characteristics would be indepen-dent of porosity.…”

Section: Resultsmentioning

confidence: 99%

“…Numbers in the last column show references for the F Si /F cont , carbon abundance, and the criteria for classifications of gas-rich versus dust-rich comets. Polarimetric data are quoted from the NASA PDS database (Kiselev et al 2017) and subsequent studies of Kwon et al (2017), Kwon et al (2018), andKwon et al (2019).…”

Section: Discussionmentioning

confidence: 99%

An Update of the Correlation between Polarimetric and Thermal Properties of Cometary Dust

Kwon,

Kolokolova,

Agarwal

et al. 2021

Preprint

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Context. Comets are conglomerates of ice and dust particles, the latter of which encode information on changes in the radiative and thermal environments to date. Dust displays distinctive scattered and thermal radiation in the visible and mid-infrared (MIR) wavelengths, respectively, based on its inherent characteristics. Aims. We aim to identify a possible correlation between the properties of scattered and thermal radiation from dust and the principal dust characteristics responsible for this relationship, and therefrom to gain insights into comet evolution. Methods. We use the NASA/PDS archival polarimetric data on cometary dust in the Red (0.62-0.73 µm) and K (2.00-2.39 µm) domains to leverage the relative excess of the polarisation degree of a comet to the average trend at the given phase angle (P excess ) as a metric of the dust's scattered light characteristics. The flux excess of silicate emissions to the continuum around 10 µm (F Si /F cont ) is adopted from previous studies as a metric of the dust's MIR feature.Results. The two observables -P excess and F Si /F cont -show a positive correlation when P excess is measured in the K domain (Spearman's rank correlation coefficient ρ = 0.71 +0.10 −0.19 ). No significant correlation was identified in the Red domain (ρ = 0.13 +0.16 −0.15 ). The gas-rich comets have systematically weaker F Si /F cont than the dust-rich ones, yet both groups retain the same overall tendency with different slope values. Conclusions. The observed positive correlation between the two metrics indicates that composition is a peripheral factor in characterising the dust's polarimetric and silicate emission properties. The systematic difference in F Si /F cont for gas-rich versus dust-rich comets would rather correspond with the difference in their dust size distribution. Hence, our results suggest that the current MIR spectral models of cometary dust, which search for a minimum χ 2 fit by considering various dust properties simultaneously, should prioritise the dust size and porosity over the composition. With light scattering being sensitive to different size scales in two wavebands, we expect the K-domain polarimetry to be sensitive to the properties of dust aggregates, such as size and porosity, which might have been influenced by evolutionary processes. On the other hand, the Red-domain polarimetry reflects the characteristics of sub-µm constituents in the aggregate.

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“…Despite the cogent evidence in the evolution of the global activity pattern of 67P and its dust particles throughout the perihelion passage, the characteristics of the dust, particularly its porosity, are still open to be discussed. A constraint on the dust porosity helps to better understand the mechanisms on the comet surface that shape surface morphology (Longobardo et al 2020;Marschall et al 2020) and macroscopic coma activity (Kwon et al 2019). However, limitations in the observing geometry of the Rosetta spacecraft that confined it to mostly terminator orbits around the comet, together with limitation in the sensitivity of the onboard dust analysers, put little constraints on the property of interest (Thomas et al 2019).…”

Section: Introductionmentioning

confidence: 99%

VLT spectropolarimetry of comet 67P: Dust environment around the end of its intense Southern summer

Kwon,

Bagnulo,

Markkanen

et al. 2021

Preprint

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Context. A cornucopia of Rosetta and ground-based observational data sheds light on the evolution of the characteristics of dust particles from comet 67P/Churyumov-Gerasimenko (hereafter 67P) with seasons, implying the different dust environments in the source regions on the surface of the comet. Aims. We aim to constrain the properties of the dust particles of 67P and therefrom diagnose the dust environment of its coma and near-surface layer at around the end of the Southern summer of the comet. Methods. We performed spectropolarimetric observations for 67P dust over 4,000-9,000 Å using the ESO/Very Large Telescope in January-March 2016 (phase angle ranging ∼26 • -5 • ). We examined the optical behaviours of the dust, which, together with Rosetta colour data, were used to search for dust evolution with cometocentric distance. Modelling was also conducted to identify the dust attributes compatible with the results. Results. The spectral dependence of the polarisation degree of 67P dust is flatter than found in other dynamical groups of comets in similar observing geometry. The depth of its negative polarisation branch appears to be a bit shallower than in long-period comets and might be getting shallower as 67P repeats its apparitions. Its dust colour shows a change in slope around 5,500 Å, (17.3 ± 1.4) and (10.9 ± 0.6) % (1,000 Å) −1 for shortward and longward of the wavelength, respectively, which are slightly redder but broadly consistent with the average of Jupiter-Family comets. Conclusions. Observations of 67P dust in this study can be attributed to dust agglomerates of ∼100 µm in size detected by Rosetta in early 2016. A porosity of 60 % shows the best match with our polarimetric results, yielding a dust density of ∼770 kg m −3 . Compilation of Rosetta and our data indicates the dust's reddening with increasing nucleus distance, which may be driven by water-ice sublimation as the dust moves out of the nucleus. We estimate the possible volume fraction of water ice in the initially ejected dust as ∼6 % (i.e. the refractory-to-ice volume ratio of ∼14).

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Near-infrared polarimetric study of near-Earth object 252P/LINEAR: an implication of scattered light from the evolved dust particles

Cited by 10 publications

References 83 publications

An update of the correlation between polarimetric and thermal properties of cometary dust

An update of the correlation between polarimetric and thermal properties of cometary dust

An Update of the Correlation between Polarimetric and Thermal Properties of Cometary Dust

VLT spectropolarimetry of comet 67P: Dust environment around the end of its intense Southern summer

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