Caltech/IPAC Lunch Seminar

Brandon Radzom (Indiana University)

COUNTESS: A Pipeline to Extract the Potential of the TESS Mission for Exoplanet Demographics

Now in its third extended mission phase, NASA's Transiting Exoplanet Survey Satellite (TESS) is well-positioned for comprehensive investigations of exoplanet demographics. Multiple sectors of coverage are now available for many targets, and numerous tools have been developed to enable deep (i.e., TESS magnitude < 13.5) transit searches over large samples of stars. Even still, exoplanet occurrence rate studies with TESS have each leveraged only a subset of these capabilities, limiting their scope. We present COUNTESS (Combining Observations to Unveil New Transiting Exoplanet Systems and Statistics), a new pipeline for light curve extraction, transit search, planet vetting, and occurrence rate calculations. COUNTESS maximizes the potential of the TESS mission for exoplanet demographics by integrating 1) reliable and lightweight light curve extraction for stars fainter than 13.5 magnitudes, 2) the capability to combine heterogeneously-sampled data from sectors spanning multiple mission phases, and 3) CPU and GPU-accelerated transit search and injection-recovery routines. Following our preliminary study, we will apply an updated version of COUNTESS to nearly 400,000 stars in the northern TESS Continuous Viewing Zone (CVZ) in search of new planets with orbital periods of up to several hundred days. Pushing to fainter limiting magnitudes significantly increases the number of CVZ stars that can be searched for transit signals, especially K and M dwarfs, enabling occurrence rate measurements for planets in the habitable zone. I also provide a brief overview of my dissertation research involving stellar obliquity measurements and numerical simulations to constrain the dynamical origins of hot Jupiters.

Alex Rodriguez (University of Michigan)

From Escape Velocities to Weak Lensing: Mapping Galaxy Cluster Potentials and Cosmic Nodes
Abstract: Galaxy clusters sit at the nodes of the cosmic web, where dark matter, galaxies, and hot gas assemble into the most massive bound structures in the Universe. Their gravitational potentials can therefore be used both to measure cluster masses and to test cosmology. I will first present a dynamical estimator based on the escape velocity profile, which traces the depth of the potential without requiring assumptions about dynamical equilibrium. Using a sample of 45 low-redshift clusters with dense spectroscopy, we find good agreement between escape velocity and weak lensing estimates, bringing escape velocity and weak lensing in-line as opposed to earlier caustic methods. The resulting agreement motivates using the escape profile as a cosmological tracer for the expansion history, for which we present preliminary Fisher Matrix forecasts and constraints from the Millennium Simulation and TNG-300. I will then describe my ongoing IPAC work extending this program to weak-lensing mass mapping and filament detection in the massive merging cluster MACS J0600.1−2008, a complex multi-wavelength system with strong-lensing, X-ray, SZ, and galaxy-density evidence for multiple projected structures. Our Subaru/HSC weak-lensing analysis uses adaptive Kaiser–Squires reconstruction, simulation tests with TNG-300, and parametric mass modeling to map projected mass beyond the strong-lensing core. Together with spectroscopy, these measurements aim to determine whether the projected structures trace a coherent cosmic-web node and to build a path forward for joint lensing–escape-velocity cluster mass inference.