Planet formation: The case for large efforts on the computational side

Modern astronomy has finally been able to observe protoplanetary disks in reasonable resolution and detail, unveiling the processes happening during planet formation. These observed processes are understood under the framework of disk-planet interaction, a process studied analytically and modeled numerically for over 40 years. Long a theoreticians' game, the wealth of observational data has been allowing for increasingly stringent tests of the theoretical models. Modeling efforts are crucial to support the interpretation of direct imaging analyses, not just for potential detections but also to put meaningful upper limits on mass accretion rates and other physical quantities in current and future large-scale surveys. This white paper addresses the questions of what efforts on the computational side are required in the next decade to advance our theoretical understanding, explain the observational data, and guide new observations. We identified the nature of accretion, ab initio planet formation, early evolution, and circumplanetary disks as major fields of interest in computational planet formation. We recommend that modelers relax the approximations of alpha-viscosity and isothermal equations of state, on the grounds that these models use flawed assumptions, even if they give good visual qualitative agreement with observations. We similarly recommend that population synthesis move away from 1D hydrodynamics. The computational resources to reach these goals should be developed during the next decade, through improvements in algorithms and the hardware for hybrid CPU/GPU clusters. Coupled with high angular resolution and great line sensitivity in ground based interferometers, ELTs and JWST, these advances in computational efforts should allow for large strides in the field in the next decade.Comment: White paper submitted to the Astro2020 decadal surve

Molecules with ALMA at Planet-forming Scales (MAPS). XII. Inferring the C/O and S/H ratios in protoplanetary disks with sulfur molecules

Funding: I.C. was supported by NASA through the NASA Hubble Fellowship grant HST-HF2-51405.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. C.W. acknowledges financial support from the University of Leeds, STFC, and UKRI (grant Nos. ST/R000549/1, ST/T000287/1, MR/T040726/1). J.D.I. acknowledges support from the Science and Technology Facilities Council of the United Kingdom (STFC) under ST/T000287/1.Sulfur-bearing molecules play an important role in prebiotic chemistry and planet habitability. They are also proposed probes of chemical ages, elemental C/O ratio, and grain chemistry processing. Commonly detected in diverse astrophysical objects, including the solar system, their distribution and chemistry remain, however, largely unknown in planet-forming disks. We present CS (2 - 1) observations at ~0"3 resolution performed within the ALMA MAPS Large Program toward the five disks around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480. CS is detected in all five disks, displaying a variety of radial intensity profiles and spatial distributions across the sample, including intriguing apparent azimuthal asymmetries. Transitions of C2S and SO were also serendipitously covered, but only upper limits are found. For MWC 480, we present complementary ALMA observations at ~ 0"5 of CS, 13CS, C34S, H2CS, OCS, and SO2. We find a column density ratio N(H2CS)/N(CS) ~ 2/3, suggesting that a substantial part of the sulfur reservoir in disks is in organic form (i.e., CxHySz). Using astrochemical disk modeling tuned to MWC 480, we demonstrate that N(CS)/N(SO) is a promising probe for the elemental C/O ratio. The comparison with the observations provides a supersolar C/O. We also find a depleted gas-phase S/H ratio, suggesting either that part of the sulfur reservoir is locked in solid phase or that it remains in an unidentified gas-phase reservoir. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.Publisher PDFPeer reviewe

Planet formation: The case for large efforts on the computational side

Modern astronomy has finally been able to observe protoplanetary disks in reasonable resolution and detail, unveiling the processes happening during planet formation. These observed processes are understood under the framework of disk-planet interaction, a process studied analytically and modeled numerically for over 40 years. Long a theoreticians' game, the wealth of observational data has been allowing for increasingly stringent tests of the theoretical models. Modeling efforts are crucial to support the interpretation of direct imaging analyses, not just for potential detections but also to put meaningful upper limits on mass accretion rates and other physical quantities in current and future large-scale surveys. This white paper addresses the questions of what efforts on the computational side are required in the next decade to advance our theoretical understanding, explain the observational data, and guide new observations. We identified the nature of accretion, ab initio planet formation, early evolution, and circumplanetary disks as major fields of interest in computational planet formation. We recommend that modelers relax the approximations of alpha-viscosity and isothermal equations of state, on the grounds that these models use flawed assumptions, even if they give good visual qualitative agreement with observations. We similarly recommend that population synthesis move away from 1D hydrodynamics. The computational resources to reach these goals should be developed during the next decade, through improvements in algorithms and the hardware for hybrid CPU/GPU clusters. Coupled with high angular resolution and great line sensitivity in ground based interferometers, ELTs and JWST, these advances in computational efforts should allow for large strides in the field in the next decade

Survey of Cold Water Lines in Protoplanetary Disks: Indications of Systematic Volatile Depletion

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Detecting a Young 2 Jupiter Mass Planet Embedded in the Disk of HD 163296

To directly confront planet formation mechanisms, a sample of objects in the earliest stages of their lives, i.e, when they are still embedded in their natal protoplanetary disks, need to be observed and studied. Here we propose to demonstrate a synergistic approach between the Atacama Large Millimeter/submillimeter Array (ALMA) and the James Webb Space Telescope (JWST). ALMA observations can reveal the location of an embedded planet by its influence on the dynamical structure of the protoplanetary disk, while the strength of these perturbations allow for a tight constraint on the mass of the planet. Here we propose to image for the first time an embedded planet in the disk around HD 163296 using the MIRI instrument onboard JWST. The 2 MJup planet has been detected in several, independent studies and lies 2" north of the host star. JWST/MIRI in coronagraphic mode at 11.4 $\mu$m is the only available option to detect such embedded objects for decades to come, as no other instrument has the mid-infrared high-contrast capabilities necessary to overcome the obstacle of disk absorption prevalent at shorter, NIR wavelengths. Given its mass and separation, the planet around HD163296 offers the highest chances of detection and would pave the path for a new and highly efficient exoplanet detection method. Detecting emission from the planet and its surrounding is going to reshape our understanding of planet formation, allowing for direct comparison between formation scenarios

Detecting a Young 2 Jupiter Mass Planet Embedded in the Disk of HD 163296

To directly confront planet formation mechanisms, a sample of objects in the earliest stages of their lives, i.e, when they are still embedded in their natal protoplanetary disks, need to be observed and studied. Here we propose to demonstrate a synergistic approach between the Atacama Large Millimeter/submillimeter Array (ALMA) and the James Webb Space Telescope (JWST). ALMA observations can reveal the location of an embedded planet by its influence on the dynamical structure of the protoplanetary disk, while the strength of these perturbations allow for a tight constraint on the mass of the planet. Here we propose to image for the first time an embedded planet in the disk around HD 163296 using the MIRI instrument onboard JWST. The 2 MJup planet has been detected in several, independent studies and lies 2" north of the host star. JWST/MIRI in coronagraphic mode at 11.4 $\mu$m is the only available option to detect such embedded objects for decades to come, as no other instrument has the mid-infrared high-contrast capabilities necessary to overcome the obstacle of disk absorption prevalent at shorter, NIR wavelengths. Given its mass and separation, the planet around HD163296 offers the highest chances of detection and would pave the path for a new and highly efficient exoplanet detection method. Detecting emission from the planet and its surrounding is going to reshape our understanding of planet formation, allowing for direct comparison between formation scenarios