I study planet formation by observing and modeling the solid reservoir (dust and ices) in circumstellar disks. This includes protoplanetary disks around young stars, debris disks around main-sequence stars, and dust disks around white dwarf stars.
I highlight some of my research projects below.
Protoplanetary Disk Ices
Ices in protoplanetary disks play an important role in the planet formation process and the delivery of biocritical molecules to young terrestrial planets. Ices can be identified via infrared spectral features, which are probed by JWST and other upcoming telescopes. I developed a novel modeling procedure to predict the observable spectral features using detailed gas-grain chemical evolution and radiative transfer simulations.
The Orion Nebula Cluster
The Orion Nebula Cluster (ONC) is a representative rich cluster—the typical environment for star and planet formation in our Galaxy. Thus, studying protoplanetary disks in the ONC reveals how most planets form. I observe these disks in the (sub-)mm with ALMA to trace their masses and sizes. Our results have revealed a distinct lack of large disks, likely because they are externally photoevaporated by the Trapezium OB stars. I am currently leading an analysis of Band 3 data that detect not just dust but also free-free emission from ionized gas around some of the disks (the so-called “proplyds”), revealing the photoevaporation process in action.
Protoplanetary Disk Masses
The dust mass in protoplanetary disks indicates their planet forming potential. I used radiative transfer models fit to disk spectral energy distributions (SEDs) to compute disk dust masses more accurately than possible with the typical calculation (which uses a single flux measurement and assumptions for the dust temperature and optical depth). I found that the true dust masses are typically 1-5 times larger than predicted by the typical calculation.
White Dwarf Dust Disks
Disks of warm dust are found around many post-main sequence white dwarf stars. This dust arises from the tidal and collisional destruction of asteroids and comets so it reveals the makeup of leftover planet-forming material. An undergraduate student and I constrained the dust properties and architecture of the disk around the white dwarf G29-38 using radiative transfer models fit the the system's infrared spectrum. More detailed observations of white dwarf dust disks are coming from JWST.
Debris Disk Dust Composition
The composition of debris disk dust traces material released from planetesimals via collisions. A powerful method to constrain the dust composition is to measure its color and albedo using observations in both scattered light and thermal emission. I modeled the famous β Pictoris debris disk and fit images from HST, Spitzer, Herschel, and ALMA using dust composed of silicates mixed with refractory organic material. The organic material may be similar to that seen on the surfaces of solar system minor bodies.
Debris Disk Architecture
By analyzing the infrared spectra and SEDs of hundreds of systems, I found that other stars have debris belts analogous to those in the solar system. I discovered a correlation between the temperature of exo-Kuiper belts and stellar type, consistent with the hypothesis that cold dust traces the outer limits of efficient planet formation. The locations of exo-asteroid belts suggest they are set by the primordial water snow line. Silicate emission features reveal the presence of warm exo-zodiacal dust in the terrestrial regions of some systems.
