The JDISC Survey: Linking the Physics and Chemistry of Inner and Outer Protoplanetary Disk Zones

MIRI spectra of select targets from the JDISCS sample, representing broad categories of sources, namely: intermediate mass, transition disk (with a large dust cavity), solar-mass with weak water emission, solar-mass with strong water emission, and a low-mass star. Emission lines from prominent atomic and molecular gas, and solid state features, are highlighted with labels.

The JDISCS Collaboration Mid-infrared spectroscopy of protoplanetary disks provides a chemical inventory of gas within a few au, where planets are readily detected around older stars.

With the JWST Disk Infrared Spectral Chemistry Survey (JDISCS), we explore demographic trends among 31 disks observed with MIRI (MRS) and with previous ALMA millimeter continuum imaging at high angular resolution (5-10 au).

With these S/N ∼200-450 spectra, we report emission from H₂O, OH, CO, C₂H₂, HCN, CO₂, [Ne II], [Ne III], and [Ar II]. Emission from H₂O, OH and CO is nearly ubiquitous for low-mass stars, and detection rates of all molecules are higher than for similar disks observed with Spitzer-IRS.

Slab model fits to the molecular emission lines demonstrate that emission from C₂H₂, HCN, and possibly CO₂ is optically thin; thus since column densities and emitting radii are degenerate, observations are actually sensitive to the total molecular mass.

C₂H₂ and HCN emission also typically originate in a hotter region (920+70−130, 820+70−130 K, respectively) than CO₂ (600+200−160 K). The HCN to cold H₂O luminosity ratios are generally smaller in smooth disks, consistent with more efficient water delivery via icy pebbles in the absence of large dust substructures.

The molecular emission line luminosities are also correlated with mass accretion rates and infrared spectral indices, similar to trends reported from Spitzer-IRS surveys. This work demonstrates the power of combining multi-wavelength observations to explore inner disk chemistry as a function of outer disk and stellar properties, which will continue to grow as the sample of observed Class II systems expands in the coming JWST observation cycles.

Nicole Arulanantham, Colette Salyk, Klaus Pontoppidan, Andrea Banzatti, Ke Zhang, Karin Öberg, Feng Long, John Carr, Joan Najita, Ilaria Pascucci, María José Colmenares, Chengyan Xie, Jane Huang, Joel Green, Sean M. Andrews, Geoffrey A. Blake, Edwin A. Bergin, Paola Pinilla, Miguel Vioque, Emma Dahl, Eshan Raul, Sebastiaan Krijt,

MIRI spectra of select targets from the JDISCS sample, representing broad categories of sources, namely: intermediate mass, transition disk (with a large dust cavity), solar-mass with weak water emission, solar-mass with strong water emission, and a low-mass star. Emission lines from prominent atomic and molecular gas, and solid state features, are highlighted with labels.

Comments: Accepted for publication in The Astronomical Journal; 43 pages, 21 figures; slab model fits for all targets will be included in the online journal and are available at https://github.com/narulanantham/JDISCS_Cyc1_slabmodelfits
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2505.07562 [astro-ph.SR] (or arXiv:2505.07562v1 [astro-ph.SR] for this version)
https://doi.org/10.48550/arXiv.2505.07562
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Submission history
From: Nicole Arulanantham
[v1] Mon, 12 May 2025 13:45:50 UTC (3,575 KB)
https://arxiv.org/abs/2505.07562
Astrobiology