The Impact of Silicate Grain Coagulation on Millimeter Emission from Massive Protostellar Disks
Hot accretion disks around massive protostars provide a unique opportunity to study ice-free silicate grains that cannot be investigated in protoplanetary disks. We conduct a self-consistent investigation into grain-size evolution and its impact on (sub)millimeter-wave emission from massive protoste...
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IOP Publishing
2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/adf49c |
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| author | Ryota Yamamuro Kei E. I. Tanaka Satoshi Okuzumi |
| author_facet | Ryota Yamamuro Kei E. I. Tanaka Satoshi Okuzumi |
| author_sort | Ryota Yamamuro |
| collection | DOAJ |
| description | Hot accretion disks around massive protostars provide a unique opportunity to study ice-free silicate grains that cannot be investigated in protoplanetary disks. We conduct a self-consistent investigation into grain-size evolution and its impact on (sub)millimeter-wave emission from massive protostellar disks. Our radiative transfer modeling accounts for dust self-scattering and includes vertical temperature gradients in the disk structure. The results show that once silicate grains grow to sizes exceeding the observing wavelength, enhanced scattering dims the disk emission by 20%–30% relative to the blackbody emission expected at the disk surface temperature. By comparing our model with Atacama Large Millimeter/submillimeter Array 1.14 mm observations of the disk around the massive protostar GGD27-MM1, we constrain the threshold velocity for collisional fragmentation of silicate grains to approximately 15 m s ^−1 . This fragmentation velocity is lower than the typical maximum collisional velocities in protoplanetary disks around low-mass stars, suggesting that collisional coagulation alone is insufficient for silicate dust to form rocky planetesimals in such environments. Furthermore, our analysis identifies two potential scenarios to better reproduce the bright inner-disk emission of GGD27-MM1. One possibility is that the grain growth is limited to 160 μ m by another growth barrier (e.g., collisional bouncing), reducing scattering dimming. Alternatively, the stellar luminosity may be as much as five times higher than current estimates, compensating for the reduced brightness. Future multiwavelength observations, particularly at shorter submillimeter wavelengths, will be crucial to distinguish between these scenarios and further constrain silicate grain coagulation processes in massive protostellar disks. |
| format | Article |
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| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-99cd30d2d83b4d1aba350e79933f6d382025-08-25T05:51:27ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0199015910.3847/1538-4357/adf49cThe Impact of Silicate Grain Coagulation on Millimeter Emission from Massive Protostellar DisksRyota Yamamuro0https://orcid.org/0000-0001-7530-1359Kei E. I. Tanaka1https://orcid.org/0000-0002-6907-0926Satoshi Okuzumi2https://orcid.org/0000-0002-1886-0880Department of Earth and Planetary Sciences, Institute of Science Tokyo , Meguro, Tokyo, 152-8551, JapanDepartment of Earth and Planetary Sciences, Institute of Science Tokyo , Meguro, Tokyo, 152-8551, JapanDepartment of Earth and Planetary Sciences, Institute of Science Tokyo , Meguro, Tokyo, 152-8551, JapanHot accretion disks around massive protostars provide a unique opportunity to study ice-free silicate grains that cannot be investigated in protoplanetary disks. We conduct a self-consistent investigation into grain-size evolution and its impact on (sub)millimeter-wave emission from massive protostellar disks. Our radiative transfer modeling accounts for dust self-scattering and includes vertical temperature gradients in the disk structure. The results show that once silicate grains grow to sizes exceeding the observing wavelength, enhanced scattering dims the disk emission by 20%–30% relative to the blackbody emission expected at the disk surface temperature. By comparing our model with Atacama Large Millimeter/submillimeter Array 1.14 mm observations of the disk around the massive protostar GGD27-MM1, we constrain the threshold velocity for collisional fragmentation of silicate grains to approximately 15 m s ^−1 . This fragmentation velocity is lower than the typical maximum collisional velocities in protoplanetary disks around low-mass stars, suggesting that collisional coagulation alone is insufficient for silicate dust to form rocky planetesimals in such environments. Furthermore, our analysis identifies two potential scenarios to better reproduce the bright inner-disk emission of GGD27-MM1. One possibility is that the grain growth is limited to 160 μ m by another growth barrier (e.g., collisional bouncing), reducing scattering dimming. Alternatively, the stellar luminosity may be as much as five times higher than current estimates, compensating for the reduced brightness. Future multiwavelength observations, particularly at shorter submillimeter wavelengths, will be crucial to distinguish between these scenarios and further constrain silicate grain coagulation processes in massive protostellar disks.https://doi.org/10.3847/1538-4357/adf49cProtoplanetary disksProtostarsMassive starsStellar accretion disksStar formationPlanetesimals |
| spellingShingle | Ryota Yamamuro Kei E. I. Tanaka Satoshi Okuzumi The Impact of Silicate Grain Coagulation on Millimeter Emission from Massive Protostellar Disks The Astrophysical Journal Protoplanetary disks Protostars Massive stars Stellar accretion disks Star formation Planetesimals |
| title | The Impact of Silicate Grain Coagulation on Millimeter Emission from Massive Protostellar Disks |
| title_full | The Impact of Silicate Grain Coagulation on Millimeter Emission from Massive Protostellar Disks |
| title_fullStr | The Impact of Silicate Grain Coagulation on Millimeter Emission from Massive Protostellar Disks |
| title_full_unstemmed | The Impact of Silicate Grain Coagulation on Millimeter Emission from Massive Protostellar Disks |
| title_short | The Impact of Silicate Grain Coagulation on Millimeter Emission from Massive Protostellar Disks |
| title_sort | impact of silicate grain coagulation on millimeter emission from massive protostellar disks |
| topic | Protoplanetary disks Protostars Massive stars Stellar accretion disks Star formation Planetesimals |
| url | https://doi.org/10.3847/1538-4357/adf49c |
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