Title: Alien oceans: hot springs, phosphorus, and the search for life in the solar system

Abstract: The discovery of liquid water oceans on Saturn’s moon Enceladus in 2006 and as many as a dozen other moons in the solar system (most notably Jupiter’s moon Europa) has greatly changed our understanding of our solar system’s "habitable zone." Rather than simply searching for liquid water, planetary scientists now need a framework to assess the relative likelihood of different planetary targets to host the physical and chemical ingredients required to support detectable biology. 

In this talk, I will discuss the planetary (hydrothermal) and exogenous (meteoritic sedimentation) processes leading to nutrients and bioavailable energy on ocean moons. I show how even a relatively tectonically quiescent seafloor can lead to hydrothermal circulation. I will then focus on a specific bioessential nutrient produced by this circulation: phosphorus that was recently discovered on Enceladus. Our published results anticipated those observations to within analytical error of the satellite. I show how models integrating stellar stoichiometry and an understanding of thermodynamics and fluid dynamics can lead to testable predictions of icy moon ocean chemistry. Finally, I discuss the implications for exoplanet and future planetary science missions. 

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Zoom Link (password 114038)

Title: Quasars in Cosmic Reionization: Environment and Impact

Abstract: The epoch of reionization (EoR) is when the first galaxies form and ionize the neutral gas in the intergalactic medium (IGM). Due to the vast distance, direct observations of EoR were limited until the past decade. Data from quasars, the brightest nontransient objects, have opened windows to study structure formation at the earliest stages. 

The regions around the quasars, called quasar proximity zones, are particularly exciting because they offer insights into a wide range of interesting physics. In this talk, I will first demonstrate how to interpret the Lyα spectra corresponding to quasar proximity zones. Then, I will show how to use absorption features to recover the density and further constrain cosmological parameters and quasar properties. 

I will also present my suite of quasar proximity zone simulations and show how galaxy formation is affected in this radiation-dominated environment. I will conclude with an outlook on synergizing JWST and ground-based observations of quasar proximity zones to advance our understanding of reionization.

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Title: Hidden Engines: Uncovering the Workings of the Nearest Galaxy Center

Abstract: Centers of galaxies are some of the most extreme objects in our universe: They host starbursts and active supermassive black holes that can launch jets and winds far outside the compact galaxy nucleus. The effects of the interactions among stars, gas and black holes that occur here don’t just stay confined to these small regions; they have an outsized influence on the overall evolution of galaxies as a whole. 

At just 8.1 kpc away, the center of the Milky Way is unparalleled in its proximity, making it the best laboratory for detailed studies of the processes that govern and define galaxy nuclei. However, the galactic center also presents a big challenge for these studies: It is a relatively quiet environment. Few stars are forming in this region, and the black hole is not active. Clearly, it hasn’t always been this way: From the Fermi Bubbles to hundred-year old echoes of X-ray bursts, there are many relics of an active past in the center of our own Milky Way. 

We also know our galaxy center likely won’t stay quiet for long; it contains a sizable reservoir of molecular gas that is the fuel for future star formation and black hole accretion. In this talk, I will present the results of research following the gas and its properties from kiloparsec to sub-parsec scales to understand why the galactic center is so quiet right now and what the future holds. Finally, I will discuss ongoing work to increase the sample size of galaxy nuclei with parsec-scale gas measurements and what this means for putting the Galactic center in context with its more active neighbors