Charting the Outer Reaches of Exoplanetary Systems: Wide-Separation Giant Planet Demographics with Direct Imaging
Eric Nielsen, Kavli Institute for Particle Astrophysics and Cosmology, Stanford University
Over the past decade, the combination of advances in adaptive optics, coronagraphy, and data processing has enabled the direct detection and characterization of giant exoplanets orbiting young, nearby stars. In addition to the wealth of information about exoplanetary atmospheres we obtain from spectroscopy of directly imaged planets, the demographics of these wide-separation planets allow us to directly test theories of planet formation, probing the outer planetary systems compared to transit and radial velocity techniques. In this talk I will present results from the Gemini Planet Imager Exoplanet Survey (GPIES), which surveyed 521 nearby stars for giant planet and brown dwarf companions orbiting beyond 5 AU, and is one of the largest, deepest direct imaging searches for exoplanets every conducted. The overall occurrence rate of substellar companions, and trends with companion mass, semi-major axis, and stellar mass are consistent with giant planets forming via core accretion, and point to different formation mechanisms for giant planets and brown dwarfs between 10 and 100 AU.
Simulating Planetesimal Formation in the Kuiper Belt and Beyond
Rixin Li, University of Arizona
A critical step in planet formation is to build super-km-sized planetesimals in protoplanetary disks. The origin and demographics of planetesimals are crucial to understanding the Solar System, circumstellar disks, and exoplanets. I will overview the current status of planetesimal formation theory. Specifically, I will present our recent simulations of planetesimal formation by the streaming instability, a mechanism to aerodynamically concentrate pebbles in protoplanetary disks. I will then discuss the connections between our numerical models and recent astronomical observations and Solar System explorations. I will explain why all planetesimals likely formed as binaries.
Protoplanetary disk rotation curves and the kinematic detection of protoplanets
Simon Casassus, Universidad de Chile
Direct detections of protoplanets still embedded in a gaseous protoplanetary disk have been remarkably elusive in their thermal-IR radiation. Yet most models for the structures observed in disks involve planet/disk interactions. The gas and dust density fields are thus appealing proxies to trace embedded bodies, but they are not sufficient to ascertain a planetary origin. New hopes for protoplanet detection come from the disk kinematics, which should also bear their dynamical imprint. The last couple of years have seen the first indirect detection of protoplanets, with the observation of small deviations from Keplerian rotation in molecular line channel maps, and their reproduction in hydrodynamical simulations. Can we use the gas kinematics directly to pin-point the location and measure the dynamical mass of giant planets? The theoretical velocity reversal along the wakes of a protoplanet should be observable as a Doppler-flip, provided that the background flow is adequately subtracted. This axially symmetric flow is a generalized rotation curve, including also the radial and vertical velocity components, which bear the imprint of accretion, winds, and of the theoretical meridional flows in the case of planet/disk interactions. I will present a technique to calculate disk rotation curves, with applications to ALMA long baseline data in HD100546 and in HD163296.
The Circumgalactic Medium at Cosmic Noon with KCWI
Nikole Nielsen, Swinburne University of Technology
The star formation history of the universe reveals that galaxies most actively build their stellar mass at cosmic noon (z=1-3), roughly 10 billion years ago, with a decrease toward present-day. The resulting metal-enriched material ejected from these galaxies due to supernovae and stellar feedback is deposited into the circumgalactic medium (CGM), which is a massive reservoir of diffuse, multiphase gas out to radii of 200 kpc. The CGM is the interface between the intergalactic medium and the galaxy, through which accreting filaments of near-pristine gas must pass to contribute new star formation material to the galaxy and outflowing gas is later recycled. Simulating these baryon cycle flows is crucial for accurately modeling galaxy evolution. While the CGM is well-studied at z<1, little attention has been paid to the reservoir when star formation is most active due to the difficulty in identifying the host galaxies. The installation of the Keck Cosmic Web Imager (KCWI), an integral field spectrograph, on Keck II has opened a new window to quickly identify galaxies via their Lyman alpha emission at this redshift. I will introduce a new survey to build a catalog of absorber-galaxy pairs at z=2-3 with KCWI. With the combination of HST images, high-resolution quasar spectra, and the cutting-edge KCWI data, this survey aims to examine CGM kinematics and metallicities and relate them to the host galaxy star formation rates and orientations to reveal the baryon cycle at cosmic noon. https://nmsu.zoom.us/j/96153330256
Transitioning to Industry from Academia,
A common career path for recent astronomy graduates with a PhD is data science, but it can be difficult to parse through the enormous amount of information on how exactly to transition to this career. I graduated from NMSU in 2019 and transitioned immediately to an industry career in data science. This talk will be a quick background on my career path, how students can get into data science, and what an industry career in data science actually looks like day-to-day.