¹Yao Liu et al. (>10)
The Astrophysical Journal, 1004, 162
Open Access Link to Article [DOI: 10.3847/1538-4357/ae6a94]
¹School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, People’s Republic of China

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 μm, 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 F₂₄/F₈, which serves as a measure of dust settling. These results suggest that dust processing proceeds in tandem with disk evolution.

^1,4Pengyue Wang, ^2,4Edward Cloutis, ^3,4Ye Su, ¹Xian Shi, ¹Man-to Hui
The Astrophysical Journal Supplement Series, 284, 61
Open Access Link to Article [DOI: 10.3847/1538-4365/ae644a]
¹Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, People’s Republic of China
²Department of Geography, University of Winnipeg, Winnipeg, Canada
³State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, People’s Republic of China

To date, the parent body of mesosiderites remains uncertain. Some candidate bodies have been proposed, including 4 Vesta and 16 Psyche. In this study, we performed a comprehensive spectroscopic survey of mesosiderites and pyroxene+metal mixtures to determine the factors that control their reflectance spectra in the 0.3–2.5 μm region and to help better identify possible parent bodies. We also applied these results to several well-known parent-body targets. We found that the mesosiderite powder and pyroxene powder on a metal slab both show significant differences in their spectra compared to Psyche. Although the spectra of the 10:90 orthopyroxene+metal powder was similar to that of Psyche, this does not necessarily mean that there is only a small amount (∼10%) of pyroxene on the surface of Psyche. Taking into account the density of Psyche, we infer that there might be a large amount of low-iron pyroxene on its surface. Looking in more detail at the spectral metrics, we note that some forms of some mesosiderites match some aspects of Psyche. Since some spectral metrics and ferrosilite content of howardites, diogenites, and mesosiderites are similar, the possibility of Vesta being a mesosiderite parent body cannot be ruled out either. However, the higher metal content of mesosiderites favors them, over howardites and diogenites, being linked to Psyche.

¹Viacheslav V. Klimenko, ¹Varsha P. Kulkarni, ²Monique C. Aller
The Astrophysical Journal, 1003, 129
Open Access Link to Article [DOI: 10.3847/1538-4357/ae5659]
¹Department of Physics & Astronomy, University of South Carolina, Columbia, SC 29208, USA
²Department of Biochemistry, Chemistry, & Physics, Georgia Southern University, Statesboro, GA 30458, USA

We present results from a mini-survey of dust spectral features arising in galaxies at redshifts 0.5 < z < 1.2 in our James Webb Space Telescope (JWST) mid-infrared spectra of physically unrelated background quasars. We analyze the JWST Mid-infrared Instrument Medium-Resolution Spectrometer spectra of five quasars presented in Klimenko et al. (Paper I) to determine the best-fit silicate mineralogies. Template profile fits to the 10 μm feature suggest the possible presence of crystalline silicates in three of the galaxies. This contrasts with the predominately amorphous silicate grains in the Milky Way diffuse interstellar medium (ISM). We also measure the extinction curves using existing data from UV to mid-IR. Combining our results with past Spitzer IRS studies, we find the following: (i) the 10 μm silicate peak optical depth (τ 10 diffuse ISM over the range A V =0.1–2.0, with τ 10 /A V ) is about 3 times stronger than expected for the local =0.17 ± 0.09. (ii) The relative strength of the UV bump is similar to that in the local ISM. However, the ratio τ 10 approaching the Galactic ISM value (∼0.1) at A V /A 2175 is larger (∼0.1–1), and appears to decrease with A ∼1.5–2. (iii) There is no significant correlation of τ R V . (iv) τ 10 is strongly correlated with the gas-phase Mg II V , 10 /A V with absorption strength for the quasar sightlines. Possible interpretations include that some quasar sightlines probe dust in the circumgalactic medium (CGM), and that dust grains may have been significantly reprocessed in the ISM and CGM under conditions that may differ from those in the local ISM.