While stellar metallicity has long been known to correlate with planetary properties, the galactic metallicity gradient alone does not account for this trend. It is therefore possible that there exists some time-dependent component to planet occurrence in the Milky Way over Gyr timescales, driven by something other than the metal enrichment of the ISM. In this talk, I will discuss recent results on the observable effect of a time-dependent planet occurrence rate upon a stellar sample chosen to resemble Kepler and K2 Sun-like stars. Using a novel planetary system population synthesis code, called psps, we imposed several prescriptions for time-variable planet occurrence upon our sample. We found that models in which the planet host fraction increased by a factor of several within the past few Gyr can reproduce the observed occurrence-galactic height trend; this timing is broadly consistent with the galactic kinematic heating timescale. Finally, I will briefly introduce my postdoc work building the Roman microlensing exoplanet occurrence pipeline, including showing the RGES PIT's first (attempt at a) detection efficiency map.
Exoplanet Demographics in Galactic Space and Time
April 10, 2026
When: April 10, 2026 2:30PM
Where:
LCO Downstairs Conference Room
Christopher Lam
Caltech / IPAC
While stellar metallicity has long been known to correlate with planetary properties, the galactic metallicity gradient alone does not account for this trend. It is therefore possible that there exists some time-dependent component to planet occurrence in the Milky Way over Gyr timescales, driven by something other than the metal enrichment of the ISM. In this talk, I will discuss recent results on the observable effect of a time-dependent planet occurrence rate upon a stellar sample chosen to resemble Kepler and K2 Sun-like stars. Using a novel planetary system population synthesis code, called psps, we imposed several prescriptions for time-variable planet occurrence upon our sample. We found that models in which the planet host fraction increased by a factor of several within the past few Gyr can reproduce the observed occurrence-galactic height trend; this timing is broadly consistent with the galactic kinematic heating timescale. Finally, I will briefly introduce my postdoc work building the Roman microlensing exoplanet occurrence pipeline, including showing the RGES PIT's first (attempt at a) detection efficiency map.
Christopher Lam
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