# Observing Circumplanetary Disks with METIS

**Authors:** Nickolas Oberg, Inga Kamp, Stephanie Cazaux, Christian Rab, Oliver Czoske  
**arXiv:** [2212.03007](https://arxiv.org/abs/2212.03007)  
**Date:** 2022-12-06  
**Summary page:** https://www.summarizepaper.com/en/paper/2212.03007v1/

## Key points

- The formation of planets and moons is a complex process that requires observations to probe the circumplanetary environment of accreting giant planets.
- The mid-infrared ELT imager and spectrograph (METIS) on the Extremely Large Telescope (ELT) can detect warm-gas emission lines from circumplanetary disks (CPDs).
- The authors aim to demonstrate METIS's ability to detect CPDs with fundamental v=1-0 transitions of $^{12}$CO from 4.5-5 $\mu$m.
- Using radiation-thermochemical disk modeling code ProDiMo, they produce synthetic spectral channel maps, while observational simulator SimMETIS is employed to produce realistic data products with the integral field spectroscopic (IFU) mode.
- Their results show that the detectability of CPD depends strongly on the level of external irradiation and the physical extent of the disk, favoring massive (~10 M$_{\rm J}$) planets and spatially extended disks with radii approaching the planetary Hill radius.
- If CPDs are dust-depleted, $^{12}$CO line emission is enhanced as external radiation can penetrate deeper into the line emitting region.
- UV-bright star systems with pre-transitional disks are ideal candidates for searching for CO-emitting CPDs with ELT/METIS.
- METIS will be able to detect a variety of circumplanetary disks via their fundamental $^{12}$CO ro-vibrational line emission in only 60 s of total detector integration time.
- High spectral resolution observations in Mid- and NIR can provide clues about determining properties such as planet mass, gas temperature, composition, physical extent and total mass limits on CPD formation.
- This information can help us understand gas giant accretion processes and regular satellite system formations around massive planets better.
- Overall, this study highlights how METIS on ELT can contribute significantly towards our understanding of planet formation processes by detecting warm-gas emissions from circumplanetary disks around accreting giant planets through its high-resolution IFU spectroscopy capabilities at L and M bands.

## Summary

The formation of planets and moons is a complex process that requires observations to probe the circumplanetary environment of accreting giant planets. The mid-infrared ELT imager and spectrograph (METIS) on the Extremely Large Telescope (ELT) provides a unique capability to detect warm-gas emission lines from circumplanetary disks (CPDs). In this study, the authors aim to demonstrate METIS's ability to detect CPDs with fundamental v=1-0 transitions of $^{12}$CO from 4.5-5 $\mu$m. They consider the case of the well-studied HD 100546 pre-transitional disk to inform their disk modeling approach. Using radiation-thermochemical disk modeling code ProDiMo, they produce synthetic spectral channel maps, while observational simulator SimMETIS is employed to produce realistic data products with the integral field spectroscopic (IFU) mode. Their results show that the detectability of CPD depends strongly on the level of external irradiation and the physical extent of the disk, favoring massive (~10 M$_{\rm J}$) planets and spatially extended disks with radii approaching the planetary Hill radius. The majority of $^{12}$CO line emission originates from the outer disk surface, resulting in centrally peaked CO line profiles. Interestingly, they find that planetary luminosity does not contribute significantly to exciting disk gas line emission. If CPDs are dust-depleted, $^{12}$CO line emission is enhanced as external radiation can penetrate deeper into the line emitting region. The authors conclude that UV-bright star systems with pre-transitional disks are ideal candidates for searching for CO-emitting CPDs with ELT/METIS. METIS will be able to detect a variety of circumplanetary disks via their fundamental $^{12}$CO ro-vibrational line emission in only 60 s of total detector integration time. Moreover, high spectral resolution observations in Mid- and NIR can provide clues about determining properties such as planet mass, gas temperature, composition, physical extent and total mass limits on CPD formation. This information can help us understand gas giant accretion processes and regular satellite system formations around massive planets better. Overall, this study highlights how METIS on ELT can contribute significantly towards our understanding of planet formation processes by detecting warm-gas emissions from circumplanetary disks around accreting giant planets through its high-resolution IFU spectroscopy capabilities at L and M bands.