January 20, 2023

The ExoExplorer Science Series presents talks by cohort members Ell Bogat (U Maryland) & Sean McCloat (U North Dakota) on January 20, 2022, from 11 AM - 12 PM Pacific / 2 PM - 3 PM Eastern. Connection information is below.

Speaker: Ell Bogat (U Maryland)

Title: Probing the Outskirts of M Dwarf Planetary Systems with a JWST Cycle 1 Direct-Imaging Survey of Nearby Young M Stars

Abstract: The population of giant planets on wide orbits around low-mass M dwarf stars is poorly understood. However, the discovery and characterization of these planets is key to understanding the architectures and evolution of M dwarf planetary systems and places their frequent and potentially habitable inner planets in context. While current ground-based imaging struggles to probe below a Jupiter mass at large separations, the unprecedented sensitivity of JWST NIRCam coronagraphic imaging provides direct access to planets significantly less massive than Jupiter beyond 10 AU around the closest, youngest M dwarfs. In this talk, I will introduce the key aspects of exoplanet direct imaging and present the survey design, observations, and preliminary results of JWST GTO Program 1184, a NIRCam coronagraphic imaging survey of very nearby, young low-mass stars.

Speaker: Sean McCloat (U North Dakota)

Title: Modeling the Architecture and Composition of Exoplanetary Systems from Pebble Accretion

Abstract: This dissertation models the composition and architecture of planetary systems formed via pebble accretion. The modeling is achieved using a combination of the pebble coagulation model “pebble-predictor” (Drazkowska et al., 2017) and accretion efficiency recipes (Ormel & Liu 2017) to consistently develop the pebble properties and protoplanet formation rates based on disk conditions. The composition of protoplanets is modeled by relating the disk properties to changes across the water ice line and assuming the local composition determines the pebble composition. In this way, the composition of pebbles, their accretion efficiency, and therefore protoplanet composition, are consistently modeled from disk properties. Model outputs are systems of protoplanets with a consistently determined mass, bulk composition, and orbital distance at the protoplanetary disk stage when gas fully dissipates. The dissertation will further explore variations in stellar mass, ice line evolution, and seed mass distributions to explore trends in the occurrence rates of different types and bulk compositions of planets.
In this research, I assume a stage of gravitational n-body interactions follows pebble accretion. N-body simulations of this sort can be computationally expensive. Fortunately, simulations encompassing a range of starting system architectures already exist in the genesis models (Mulders et al. 2018). The results of the genesis models are recorded and publicly available in the form of interaction histories between protoplanets, or “collision trees”. This research will compare model outputs to inputs of genesis to determine what conditions, if any, can be followed through the late stages of planet formation and inspect final planetary system bulk composition and architecture.

Meeting link:
Meeting number:
2763 643 6746