Dust Scattering Albedo at Millimeter Wavelengths in the TW Hya Disk
Planetary bodies are formed by coagulation of solid dust grains in protoplanetary disks. Therefore, it is crucial to constrain the physical and chemical properties of the dust grains. In this study, we measure the dust albedo at millimeter wavelength, which depends on dust properties at the disk mid...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ad9f31 |
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| author | Tomohiro C. Yoshida Hideko Nomura Takashi Tsukagoshi Kiyoaki Doi Kenji Furuya Akimasa Kataoka |
| author_facet | Tomohiro C. Yoshida Hideko Nomura Takashi Tsukagoshi Kiyoaki Doi Kenji Furuya Akimasa Kataoka |
| author_sort | Tomohiro C. Yoshida |
| collection | DOAJ |
| description | Planetary bodies are formed by coagulation of solid dust grains in protoplanetary disks. Therefore, it is crucial to constrain the physical and chemical properties of the dust grains. In this study, we measure the dust albedo at millimeter wavelength, which depends on dust properties at the disk midplane. Since the albedo and dust temperature are generally degenerate in observed thermal dust emission, it is challenging to determine them simultaneously. We propose to break this degeneracy by using multiple optically thin molecular lines as a dust–albedo-independent thermometer. In practice, we employ pressure-broadened CO line wings that provide an exceptionally high signal-to-noise ratio as an optically thin line. We model the CO J = 2–1 and 3–2 spectra observed by the Atacama Large Millimeter/submillimeter Array at the inner region ( r < 6 au) of the TW Hya disk and successfully derive the midplane temperature. Combining multiband continuum observations, we constrain the albedo spectrum at 0.9–3 mm for the first time without assuming a dust opacity model. The albedo at these wavelengths is high, ~0.5–0.8, and broadly consistent with the L. Ricci et al., DIANA, and DSHARP dust models. Even without assuming dust composition, we estimate the maximum grain size to be ~340 μ m, the power-law index of the grain size distribution to be >−4.1, and the porosity to be <0.96. The derived dust size may suggest efficient fragmentation with a threshold velocity of ~0.08 m s ^−1 . We also note that the absolute flux uncertainty of ~10% (1 σ ) is measured and used in the analysis, which is approximately twice the usually assumed value. |
| format | Article |
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| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-4b8178e294514e3b8b1d72ad0b04d4562025-02-03T13:23:49ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198015010.3847/1538-4357/ad9f31Dust Scattering Albedo at Millimeter Wavelengths in the TW Hya DiskTomohiro C. Yoshida0https://orcid.org/0000-0001-8002-8473Hideko Nomura1https://orcid.org/0000-0002-7058-7682Takashi Tsukagoshi2https://orcid.org/0000-0002-6034-2892Kiyoaki Doi3https://orcid.org/0000-0003-1958-6673Kenji Furuya4https://orcid.org/0000-0002-2026-8157Akimasa Kataoka5https://orcid.org/0000-0003-4562-4119National Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; Department of Astronomical Science, The Graduate University for Advanced Studies , SOKENDAI, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, JapanNational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; Department of Astronomical Science, The Graduate University for Advanced Studies , SOKENDAI, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, JapanFaculty of Engineering, Ashikaga University , Ohmae 268-1, Ashikaga, Tochigi 326-8558, JapanNational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; Department of Astronomical Science, The Graduate University for Advanced Studies , SOKENDAI, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; Max-Planck Institute for Astronomy , Königstuhl 17, D-69117 Heidelberg, GermanyDepartment of Astronomy, The University of Tokyo , Bunkyo-ku, Tokyo 113-0033, Japan; RIKEN Cluster for Pioneering Research , 2-1 Hirosawa, Wako-shi, Saitama 351-0198, JapanNational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; Department of Astronomical Science, The Graduate University for Advanced Studies , SOKENDAI, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, JapanPlanetary bodies are formed by coagulation of solid dust grains in protoplanetary disks. Therefore, it is crucial to constrain the physical and chemical properties of the dust grains. In this study, we measure the dust albedo at millimeter wavelength, which depends on dust properties at the disk midplane. Since the albedo and dust temperature are generally degenerate in observed thermal dust emission, it is challenging to determine them simultaneously. We propose to break this degeneracy by using multiple optically thin molecular lines as a dust–albedo-independent thermometer. In practice, we employ pressure-broadened CO line wings that provide an exceptionally high signal-to-noise ratio as an optically thin line. We model the CO J = 2–1 and 3–2 spectra observed by the Atacama Large Millimeter/submillimeter Array at the inner region ( r < 6 au) of the TW Hya disk and successfully derive the midplane temperature. Combining multiband continuum observations, we constrain the albedo spectrum at 0.9–3 mm for the first time without assuming a dust opacity model. The albedo at these wavelengths is high, ~0.5–0.8, and broadly consistent with the L. Ricci et al., DIANA, and DSHARP dust models. Even without assuming dust composition, we estimate the maximum grain size to be ~340 μ m, the power-law index of the grain size distribution to be >−4.1, and the porosity to be <0.96. The derived dust size may suggest efficient fragmentation with a threshold velocity of ~0.08 m s ^−1 . We also note that the absolute flux uncertainty of ~10% (1 σ ) is measured and used in the analysis, which is approximately twice the usually assumed value.https://doi.org/10.3847/1538-4357/ad9f31Protoplanetary disksPlanet formationDust composition |
| spellingShingle | Tomohiro C. Yoshida Hideko Nomura Takashi Tsukagoshi Kiyoaki Doi Kenji Furuya Akimasa Kataoka Dust Scattering Albedo at Millimeter Wavelengths in the TW Hya Disk The Astrophysical Journal Protoplanetary disks Planet formation Dust composition |
| title | Dust Scattering Albedo at Millimeter Wavelengths in the TW Hya Disk |
| title_full | Dust Scattering Albedo at Millimeter Wavelengths in the TW Hya Disk |
| title_fullStr | Dust Scattering Albedo at Millimeter Wavelengths in the TW Hya Disk |
| title_full_unstemmed | Dust Scattering Albedo at Millimeter Wavelengths in the TW Hya Disk |
| title_short | Dust Scattering Albedo at Millimeter Wavelengths in the TW Hya Disk |
| title_sort | dust scattering albedo at millimeter wavelengths in the tw hya disk |
| topic | Protoplanetary disks Planet formation Dust composition |
| url | https://doi.org/10.3847/1538-4357/ad9f31 |
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