Characterizing Accretion and Formation Mechanisms across the Brown Dwarf and Planetary Mass Regimes

Recent discoveries of still-forming brown dwarfs (BD) and exoplanets have placed new importance on understanding the mechanisms and environments that control the formation and evolution of substellar objects. Accretion mechanisms are well understood for stars, and substellar objects have been assumed to operate similarly; however, simulations suggest that the accretion rates of substellar objects are controlled in part by their formation mechanism. In this dissertation talk, I will discuss my work disentangling physical and systematics effects in the inferred accretion properties of substellar objects using the Comprehensive Archive of subStellar Accretion Rates (CASPAR). The CASPAR Database consists of >1000 measured accretion rates from ~800 T Tauri stars, isolated BDs, and bound planetary mass companions, making it the largest compiled sample of accretion rates for low mass stellar and substellar objects to date. I systematically rederive physical and accretion properties for all objects using (a) Gaia distances, (b) consistent ages and evolutionary model grids, and (c) a single set of line to total-accretion-luminosity scaling relations. This update decreases the scatter in the M-Ṁ relation from 2.7 dex to 2.4 dex, indicating that the remaining broad scatter is attributable to physical effects such as age and variability. I will also present results from a 2.5 year observing campaign using SOAR/TripleSpec4.1 to measure accretion rates for a statistical sample of isolated BDs and bound planetary mass companions. NIR Paβ, Paγ, and Brγ emission line luminosities and ratios allow me to compare my observations to varying accretion and formation models. As part of this survey, I detected the first NIR accretion signatures from a protoplanet, Delorme 1 (AB)b, and found that it is accreting at a rate of 3-4x10^-8 M_J/yr. Ratios of its NIR emission lines are most consistent with planetary shock accretion models, and its high accretion rate suggests formation via disk fragmentation. I will use the observations from this large, systematic, sample to derive new emission-line to total-accretion-luminosity scaling relations for the BD regime, allowing future observers to more accurately interpret the accretion signatures of substellar objects.