Results of the summarizing process for the arXiv paper: 2207.05923v1

, , , , We report the discovery of a circumplanetary disk (CPD) candidate embedded in the circumstellar disk of the T Tauri star AS 209 at a radial distance of about 200 au. The CPD was isolated via $^{13}$CO $J=2-1$ emission, marking the first instance of CPD detection through gaseous emission and allowing for the tracing of its overall mass. It appears as a spatially unresolved point source in $^{13}$CO, with an estimated diameter of less than 14 au. The CPD is situated within an annular gap previously identified using $^{12}$CO and near-infrared scattered light observations and is associated with localized velocity perturbations in $^{12}$CO, indicating a common origin with an embedded giant planet. Further analysis reveals that the CPD gas temperature is above 35 K, higher than the surrounding circumstellar disk temperature at that radial location. This suggests the presence of localized heating sources within the CPD. The estimated gas mass of the CPD is approximately 0.095 Jupiter masses or around 30 Earth masses based on a standard $^{13}$CO abundance. Additionally, no millimeter continuum emission was detected at the location of the CPD, indicating a dust mass of less than 0.027 Earth masses or approximately 2.2 lunar masses, resulting in a low dust-to-gas mass ratio. The formation mechanism of the CPD-hosting giant planet is discussed within the framework of gravitational instability and pebble accretion processes. The long core accretion timescale suggests that the planet may have entered a runaway accretion phase within the last million years due to slower radial drift or particle trapping enhancing pebble accretion efficiency. Future observational directions include additional ALMA observations to detect chemical asymmetries induced by planetary/CPD heating and infrared observations using telescopes like James Webb Space Telescope to probe thermal emissions from the planet and constrain its mass further. Monitoring for accretion signatures such as Hα line emission could provide valuable insights into the evolutionary stage and current position of the planet. In conclusion, this discovery sheds light on the complex interplay between giant planets, circumplanetary disks, and their host stars, offering new avenues for studying planetary formation processes on wide orbits in young stellar systems like AS 209.

• Discovery of a circumplanetary disk (CPD) candidate in the circumstellar disk of T Tauri star AS 209 at 200 au
• CPD isolated via $^{13}$CO $J=2-1$ emission, first detection through gaseous emission
• CPD appears as spatially unresolved point source, estimated diameter less than 14 au
• CPD situated within annular gap previously identified using $^{12}$CO and near-infrared scattered light observations, associated with localized velocity perturbations in $^{12}$CO
• CPD gas temperature above 35 K, higher than surrounding circumstellar disk temperature at that radial location
• Estimated gas mass of CPD approximately 0.095 Jupiter masses or around 30 Earth masses based on standard $^{13}$CO abundance
• No millimeter continuum emission detected at CPD location, indicating low dust mass of less than 0.027 Earth masses or approximately 2.2 lunar masses
• Formation mechanism discussed in context of gravitational instability and pebble accretion processes, suggesting planet may have entered runaway accretion phase within last million years
• Future observational directions include additional ALMA observations to detect chemical asymmetries induced by planetary/CPD heating and infrared observations using telescopes like James Webb Space Telescope to probe thermal emissions from planet and constrain its mass further

Introduction

The formation of planets is a complex and ongoing process that has been the subject of extensive research in recent years. In particular, the detection and study of circumplanetary disks (CPDs) – disks of gas and dust surrounding young giant planets – have provided valuable insights into this process. In a recent paper published in The Astrophysical Journal Letters, researchers report the discovery of a CPD candidate around the T Tauri star AS 209, providing new information about planetary formation on wide orbits.

The Discovery

Using data from the Atacama Large Millimeter/submillimeter Array (ALMA), the team detected gaseous emission from $^{13}$CO $J=2-1$ at a radial distance of approximately 200 au from AS 209. This marks the first instance of CPD detection through gaseous emission, allowing for further analysis and characterization. The CPD appears as an unresolved point source with an estimated diameter of less than 14 au.

The location of the CPD was identified within an annular gap previously observed using $^{12}$CO and near-infrared scattered light observations. This suggests a common origin with an embedded giant planet, which is further supported by localized velocity perturbations seen in $^{12}$CO emissions.

Characteristics of the CPD

Further analysis revealed that the temperature within the CPD is above 35 K, higher than that of its surrounding circumstellar disk at that radial distance. This indicates localized heating sources within the CPD, possibly due to interactions with its host planet or other mechanisms.

Based on standard abundances for $^{13}$CO, it is estimated that the gas mass within the CPD is approximately 0.095 Jupiter masses or around 30 Earth masses. However, no millimeter continuum emission was detected at this location, suggesting a dust mass of less than 0.027 Earth masses or approximately 2.2 lunar masses. This results in a low dust-to-gas mass ratio, which is consistent with previous studies of CPDs.

Implications for Planetary Formation

The discovery of this CPD candidate provides valuable insights into the formation mechanisms of giant planets on wide orbits like AS 209. The long core accretion timescale suggests that the planet may have entered a runaway accretion phase within the last million years due to slower radial drift or enhanced pebble accretion efficiency through particle trapping.

Future observations using ALMA could potentially detect chemical asymmetries induced by planetary/CPD heating, providing further information about the composition and dynamics of these disks. Infrared observations using telescopes like the James Webb Space Telescope could also probe thermal emissions from the planet and constrain its mass even further.

Conclusion

In conclusion, this discovery sheds light on the complex interplay between giant planets, circumplanetary disks, and their host stars. It offers new avenues for studying planetary formation processes on wide orbits in young stellar systems like AS 209. Continued research and observations will provide further insights into the formation and evolution of these intriguing objects.