Gas dynamics and chemistry around an embedded planet
Abstract
The chemical properties of exoplanets are inherited from their natal protoplanetary disk. In models that compute the link between disks and planets one generally assumes that the chemical state of the material is unchanged as it flows from the disk to the planet. However the gas is heated as it falls deeper into the planet's gravitational potential, potentially leading to a drastic change in its chemical makeup between the hot circumplanetary disk and the much colder protoplanetary disk. In this talk I will present recent work post-processing a hydrodynamic simulation with a chemical kinetic model to demonstrate the chemical processing of the gas as it flows from the cold (~ 40 K) protoplanetary disk to the hot (~ 200-800 K) circumplanetary disk. The large change in temperature releases all of the available volatiles into the gas phase which could change the rate at which elements like carbon and oxygen are transported to the atmosphere of giant planets. In addition the warm temperatures allow for unique chemistry to occur in the circumplanetary environment which could differentiate it from the protoplanetary disk observationally.
Full text
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Gas dynamics around a Jupiter mass planet Alex Cridland, Staff Scientist, Theoretical Astrophysics of Extra-solar Planets chair University Observatory of Munich (USM), LMU [email protected] Co-authors: - Myriam Benisty, (MPIA, ERC-protoplanets) - Elena Lega (OCA) Chemical evolution of circumplanetary material
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets So let’s start at the end… ●Circumplanetary disks (CPDs) are hot -at least during the presented phase of planet formation ●High temperatures drive the chemical state of the gas away from PPD ●Sulfur-bearing species (CS, SO, SO2) show a particular sensitivity to the CPD ●The CPD is too hot to produce canonical ice lines, ice species arriving on dust grains are sublimated and may mix into the volatile stockpile of the CPD … you may now zone out, or wait and see how we got here
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Most PF studies compare PPD to mature planets A more direct approach may be to chemically characterize young protoplanets in their natal PPD ALMA (ESO/NAOJ/NRAO)/Benisty+ (2021) Wang+ 2021 Facchini+ 2021 Everyone’s favourite, PDS 70: See for ex. Cridland+ (2023)
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Most PF studies compare PPD to mature planets But finding these embedded protoplanets present a challenge PDS 70 HD 169142 Law+ 2023 Contours: SO; SiS HD 100546 Modified from Booth+ 2024 Gas emission asymmetry may trace embedded planets
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Goals: molecular tracers of protoplanets? ●What are the physical and chemical properties of the gas encircling an embedded planet? ●Are there molecular species that tend to arise in the warm circumplanetary material around a protoplanet? ●How does the change in gas temperature affect the flow of volatiles to the planet?
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Goals: molecular tracers of protoplanets? ●Paper 1: Lega, Benisty, Cridland+ (Oct 2024) ○Gas dynamics around a Jupiter mass planet: I. Influence of protoplanetary disk properties ●Paper 2: Cridland, Lega, & Benisty (Jan 2025) ○Gas dynamics around a Jupiter mass planet: II. Chemical evolution of circumplanetary material -> 3D FargOCA simulation of embedded Jupiter
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Method: FARGOCA hydrodynamic code ●FargOCA: non-self gravitating single fluid hydrodynamic simulation of a PPD embedded with a Jupiter-mass planet ○Opened gap, with gas flow through 1st and 2nd Lagrange points and meridional flow ●Temperature of the gas computed via flux limited diffusion ●Post-processing: hold the velocity field & temperature static while computing streamlines through the simulation Paper 1: Lega, Benisty, Cridland+ (2024) Paper 2: Cridland, Lega, & Benisty (2025) -> 3D FargOCA simulation of embedded Jupiter Streamline: Trajectory of a Lagrangian particle moving through the fluid
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Setup: Jupiter-mass planet, MMSN disk ●FargOCA: non-self gravitating single fluid hydrodynamic simulation of a PPD embedded with a Jupiter-mass planet ○Opened gap, with gas flow through 1st and 2nd Lagrange points and meridional flow ●Disk density structure set to the MMSN for the Nominal model ○Doesn’t produce a CPD but P-supported env. ●LowMass model reduces disk density by 10x ○We do produce a CPD, and is featured here -> 3D FargOCA simulation of embedded Jupiter Paper 1: Lega, Benisty, Cridland+ (2024) Paper 2: Cridland, Lega, & Benisty (2025)
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Examples of streamlines Orbiting streamlines Near misses Meridional flows Lega+ incl. AC (2024) **NB: The Hill sphere is the region where the planet’s gravity exceeds its host star
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Chemical evolution in each streamline - a summary 1. CPD causes release of volatile species into the gas phase 1. Sulfur oxides are formed from sublimated H2S in CPD (and OH made available from H2O) 1. Sulfur carbides are formed / sublimated in CPD Law+ 2023 Contours: SO; SiS Booth+ 2023 HD 169142
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Estimated SO, SO2, CS, and H2CS column: 2(14), 7(14), 5(14), 2(17) cm2in the simulated CPD 2 x 1014 cm-2 Based on the thermochemical disk model (DALI, Bruderer+ 2012,2013) of PDS 70 by Cridland+ (2023) Quantitative comparison to observations/models Cridland, Lega, & Benisty (2025)
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Quantitative comparison to observations/models Estimated SO, SO2, CS, and H2CS column: 2(14), 7(14), 5(14), 2(17) cm2in the simulated CPD 2 x 1014 cm-2 SO column in the NE blob of HD 169142 is 5(13) SO2column in the NE blob of HD 169142 is <4(13) (Law+ 2023) Based on the thermochemical disk model (DALI, Bruderer+ 2012,2013) of PDS 70 by Cridland+ (2023) Cridland, Lega, & Benisty (2025)
Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Alex Cridland [email protected] Alex Cridland [email protected] Towards new frontiers: the astrochemical journey from young stellar nurseries to exoplanets Conclusions ●We have post-processed a hydrodynamic simulation of the gas flow around a Jupiter-mass, embedded protoplanet in a class-II disk with chemical kinetics ●The CPD provides high gas temperatures (200 K<T<800 K) which drives the production of interesting sulfur species like CS, SO ●These molecules have column densities that are consistent with (though over predict) observations - and SO could be used to find embedded planets via emission asymmetries ●The CPD is too hot to produce canonical ice lines, ice species arriving on dust grains are sublimated and may mix into the volatile stockpile of the CPD