Year: 2026
Type: article
Abstract: Infrared spectroscopy provides a powerful diagnostic for probing the mineralogical properties of dust grains in the terrestrial planet–forming regions of protoplanetary disks. The Upper Scorpius association offers an excellent laboratory for studying disk evolution because it represents an evolved stage (5−10 Myr) compared with younger star-forming regions such as the Taurus molecular cloud (1−3 Myr). In this work, we present mid-infrared spectra of 11 disks in Upper Scorpius that were obtained with the Mid-Infrared Instrument aboard the James Webb Space Telescope. We derive emission feature indices for crystalline olivine and pyroxene centered at ∼9.2 and ∼11.1 μ m, as well as perform spectral decomposition to quantify dust crystallinity and characteristic grain size. These results are compared with those measured from Spitzer/IRS spectra of 31 disks in Taurus with similar stellar types. We find no significant difference in dust crystallinity between the two groups, suggesting that crystallization is largely established at early stages of disk evolution. Our analysis indicates that the average grain size in Upper Scorpius disks is systematically larger than that in Taurus disks, aligning with theories of dust evolution. We also observe a trend of increasing grain size towards later-type stars, as well as a correlation between crystallinity, grain size, and the flux ratio F 24 / F 8 , which serves as a measure of dust settling. These results suggest that dust processing proceeds in tandem with disk evolution.
Source: The Astrophysical Journal
Institutions: Southwest Jiaotong University, University of Arizona, Peking University, Atacama Large Millimeter Submillimeter Array, California Institute of Technology, Texas State University, University of Leeds, University of Science and Technology of China, Chinese Academy of Sciences, Ames Research Center, Search for Extraterrestrial Intelligence
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: National Aeronautics and Space Administration, California Institute of Technology, Space Telescope Science Institute, National Natural Science Foundation of China, Chinese Academy of Sciences, Natural Science Foundation of Sichuan Province, Jet Propulsion Laboratory, Fundamental Research Funds for the Central Universities
OpenAlex ID: W7164522018