PROTOPLANETS

Context and goals

The process of planet formation and disk evolution leaves an imprint on the distribution of material at different locations in a protoplanetary disk, resulting in a variety of substructure (rings/gaps, spirals, vortices, etc.) that can be observed from optical to sub-millimeter wavelengths. And now, ALMA observations at high spatial resolution can routinely provide evidence for this varied morphology (e.g., ALMA Partnership et al. 2015). In particular, the striking ALMA images of dark and bright annuli trace zones where solid particles have been depleted (dark gaps) and concentrated (bright rings). Such rings/gaps may arise from the dynamical interaction of embedded planets or companions, or from zonal flows due to magnetic processes, and/or be associated with the sublimation fronts of major volatiles. These mechanisms can all produce concentric rings of emission, of tantalizing similarity to those observed in the disks, but if planetary-mass companions are preferentially found inside the gaps of disks with ring morphology, then dynamical clearing becomes the favored mechanism for their creation. The best example of a planet-hosting disk with ring morphology is PDS 70, a young star with a massive disk and a large gap. Inside, two accreting protoplanets have been directly imaged and are studied from the optical to the sub-mm. However, most evidence of planet formation in protoplanetary disks is indirect. In some disks, deviations from Keplerian motion are observed and explained by the presence of a planetary-mass perturber. And in all disks observed at sufficient resolution, rings and gaps are practically ubiquitous in ALMA observations. Since the location of such gaps appears uncorrelated with the snowline location of common molecules, planets continue to be the most likely explanation for the presence of gaps. Even disks with spiral substructure or those in multiple systems, exhibit annular gaps. Thus, the use of direct imaging is precious to search for companions in disks with known gaps to answer the question of whether planet-mass companions are responsible for such common ring/gap substructure. Direct detection of planet in formation is precious to inform us on the planet/disk interaction, and the physics of accretion during the formation phase of giant planets that impact the final physical properties and evolution of giant planets.

Protoplanet hunt in Direct Imaging

In the context, I have initiated with Nurial Huélamo and Laura Pérez several dedicated campaigns with NaCo, SPHERE and MUSE at VLT in planet-hunt mode to search for these young protoplanets in formation, ideal to test if dynamical clearing by one or multiple planetary companion(s) is responsible for the many gaps discovered in young circumstellar disks.

The NaCo, SPHERE & Gravity DSHARP follow-up campaigns: These on-going campaigns are targetting the discovery of young giant planets recently formed in protoplanetary disks, showing a variety of substructure (rings/gaps, spirals, vortices, etc.). They offer a remarkable opportunity: (a) to resolve the disk and any massive proto-planet in each system; (b) to set constraints on the timescale of planetary formation (if detected, planets must form early-on given the young age of the stars, with the sample mean age of 1 Myr); (c) to test predictions for the process of gas accretion as set by the different cold-, warm- and hot-start models; (d) to study planet-disk interactions and verify that the potential protoplanet(s) are responsible for asymmetries observed by ALMA, through gas and dust modeling considering the planet properties and location; (e) for systems with multiple rings/gaps there is a unique opportunity to directly image multiple protoplanets in a forming planetary system; and (f) by constraining any potential protoplanet, we will be able to determine if a single planet can generate multiple gaps in a given disk.
The SPHERE & MUSE accreting planets campaigns: Characterizing the physics of accretion during the earliest stages of planet formation is a critical step toward a better understanding of the key physical processes at play in the formation and evolution of giant planets. The way gas accretes and shocks (sub- or super-critical) on the surface of young accreting planets, will drive the planet’s initial entropy or internal energy. Hence, its initial physical properties (luminosity, effective temperature, surface gravity, radius) and its subsequent time evolution depends on the way accretion proceeds (e.g. Cumming et al. 2018). These different physical states are today described by the so-called hot-start (sub-critical shock), cold-start (super- critical shock), and warm-start (intermediate cases) models. These models predict luminosities that are spread over several order of magnitudes for young, massive giant planets. Given our lack of observational constraints, further observations and characterization of accreting protoplanets in young protoplanetary disks is crucial. In this context, we have initiated deep imaging surveys with SPHERE/ZIMPOL and MUSE-NFM to to identify the posited protoplanets that create the observed substructure in young disks, while providing valuable constraints for the process of planet formation to quantify the amount of material and the growth rate of these young giant planets.

Publications

Publications fully related to the PROTOPLANETS project:

Jorquera, Sebastian, Pérez, Laura M., Chauvin, Gaël, Benisty, Myriam, Zhu, Zhaohuan, Isella, Andrea, Huang, Jane, Ricci, Luca, Andrews, Sean M., Zhang, Shangjia, Carpenter, John M., Kurtovic, Nicolás T., & Birnstiel, Tilman 2021, The Astronomical Journal A Search for Companions via Direct Imaging in the DSHARP Planet-forming Disks de Boer, J., Ginski, C., Chauvin, G., Ménard, F., Benisty, M., Dominik, C., Maaskant, K., Girard, J. H., van der Plas, G., Garufi, A., Perrot, C., Stolker, T., Avenhaus, H., Bohn, A., Delboulbé, A., Jaquet, M., Buey, T., Möller-Nilsson, O., Pragt, J., & Fusco, T. 2021, Astronomy and Astrophysics Possible single-armed spiral in the protoplanetary disk around HD 34282 Cugno, G., Quanz, S. P., Hunziker, S., Stolker, T., Schmid, H. M., Avenhaus, H., Baudoz, P., Bohn, A. J., Bonnefoy, M., Buenzli, E., Chauvin, G., Cheetham, A., Desidera, S., Dominik, C., Feautrier, P., Feldt, M., Ginski, C., Girard, J. H., Gratton, R., Hagelberg, J., Hugot, E., Janson, M., Lagrange, A. -M., Langlois, M., Magnard, Y., Maire, A. -L., Menard, F., Meyer, M., Milli, J., Mordasini, C., Pinte, C., Pragt, J., Roelfsema, R., Rigal, F., Szulágyi, J., van Boekel, R., van der Plas, G., Vigan, A., Wahhaj, Z., & Zurlo, A. 2019, Astronomy and Astrophysics A search for accreting young companions embedded in circumstellar disks. High-contrast Hα imaging with VLT/SPHERE Huélamo, N., Chauvin, G., Schmid, H. M., Quanz, S. P., Whelan, E., Lillo-Box, J., Barrado, D., Montesinos, B., Alcalá, J. M., Benisty, M., de Gregorio-Monsalvo, I., Mendigutía, I., Bouy, H., Merín, B., de Boer, J., Garufi, A., & Pantin, E. 2018, Astronomy and Astrophysics Searching for Halpha emitting sources around MWC 758. SPHERE/ZIMPOL high-contrast imaging

Collaborators

PROTOPLANETS team: Laura Pérez, Sebastian Jorquera, Mickael Bonnefoy, Myriam Benisty, Nuria Huélamo & Sebastian Haffert

DSHARP team: Sean Andrews, Xuening Bai, Til Birnstiel, Cornelis Dullemond, Viviana Guzman, Jane Huang, Luca Ricci, Zhaohuan Zhu