# Testing planet formation from the ultraviolet to the millimeter

**Authors:** Nick Choksi, Eugene Chiang  
**arXiv:** [2110.00029](https://arxiv.org/abs/2110.00029)  
**Date:** 2021-09-30  
**Summary page:** https://www.summarizepaper.com/en/paper/2110.00029v1/

## Key points

- Authors investigate the role of planets in opening gaps in protoplanetary discs
- Gaps are believed to be formed by planets during their formation process
- Authors compute present-day mass accretion rates ($\dot{M}_{\rm p}$) of seven hypothesized gap-embedded planets and two confirmed planets in PDS 70
- $\dot{M}_{\rm p}$ is determined by combining disc gas surface densities ($\Sigma_{\rm gas}$) obtained from C$^{18}$O observations with planet masses ($M_{\rm p}$) derived from simulations fitted to observed gaps
- In eight out of nine cases, $\dot{M}_{\rm p}$ is consistent with the time-averaged value given by current planet mass and system age ($M_{\rm p}/t_{\rm age}$)
- Gap-opening planets may be undergoing final stages of mass doubling and will likely reach final masses of approximately $10-10^2 \, M_\oplus$ for non-PDS 70 planets and $1-10 \, M_{\rm J}$ for PDS 70 planets
- Predictions about $\Sigma_{\rm gas}$ are made for fifteen gaps without C$^{18}$O data based on assuming respective planets are accreting at their time-averaged $\dot{M}_{\rm p}$
- Bondi accretion rates for PDS 70b and c are orders of magnitude higher than implied by measured U-band and H$\alpha$ fluxes
- This suggests that most of the accretion shock luminosity emerges in unobserved wavebands or that the planets are surrounded by dusty circumplanetary envelopes which highly extinct light
- Thermal emission from these envelopes or from circumplanetary discs on Hill sphere scales could explain observed mm-wave excesses
- Study provides insights into planet formation and how gap-opening planets shape protoplanetary discs from ultraviolet to millimeter wavelengths
- Findings contribute to understanding of planetary systems and their evolution.

## Summary

In their study titled "Testing planet formation from the ultraviolet to the millimeter," authors Nick Choksi and Eugene Chiang investigate the role of planets in opening gaps in protoplanetary discs. These gaps are believed to be formed by planets during their formation process. The authors compute the present-day mass accretion rates ($\dot{M}_{\rm p}$) of seven hypothesized gap-embedded planets, as well as two confirmed planets in PDS 70. To determine $\dot{M}_{\rm p}$, the authors combine disc gas surface densities ($\Sigma_{\rm gas}$) obtained from C$^{18}$O observations with planet masses ($M_{\rm p}$) derived from simulations that are fitted to observed gaps. Assuming that accretion follows a Bondi-like mechanism, they find that in eight out of nine cases, $\dot{M}_{\rm p}$ is consistent with the time-averaged value given by the current planet mass and system age ($M_{\rm p}/t_{\rm age}$). The authors note that since system ages are comparable to circumstellar disc lifetimes, these gap-opening planets may be undergoing their final stages of mass doubling and will likely reach final masses of approximately $10-10^2 \, M_\oplus$ for non-PDS 70 planets and $1-10 \, M_{\rm J}$ for PDS 70 planets. For an additional fifteen gaps without C$^{18}$O data, the authors make predictions about $\Sigma_{\rm gas}$ by assuming that their respective planets are accreting at their time-averaged $\dot{M}_{\rm p}$. Interestingly, when examining Bondi accretion rates for PDS 70b and c, the authors find them to be orders of magnitude higher than what is implied by measured U-band and H$\alpha$ fluxes. This suggests that most of the accretion shock luminosity emerges in unobserved wavebands or that the planets are surrounded by dusty circumplanetary envelopes which highly extinct light. The authors propose that thermal emission from these envelopes or from circumplanetary discs on Hill sphere scales could explain the observed mm-wave excesses. Overall, this study provides insights into the process of planet formation and highlights how gap-opening planets shape protoplanetary discs from ultraviolet to millimeter wavelengths. The findings contribute to our understanding of planetary systems and their evolution.