Title: TBA

Abstract: TBA

Title: TBA

Abstract: TBA

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.

Title: Star formation and evolution in AGN disks, with application to Little Red Dots

Abstract: Study of stellar objects embedded in AGN accretion disks has been motivated by i) the disk(s) of stars that possibly formed in-situ in the galactic center; ii) the super-solar metallicity of classical quasars independent of redshift, as well as possible AGN+star origin of Little Red Dots; iii) quasi-periodic eruptions connected to star-disk collisions; and iv) LIGO-Virgo gravitational wave sources potentially born in gas rich environments. 

In this talk, I will introduce some recent progress on radiation hydrodynamic simulations of stellar evolution in AGN disks, focusing on their formation from fragmentation of a gravitationally unstable disk and their accretion process in a stratified gas-rich background. We argue that a population of such stars is able to power the extended, optically thick and marginally gravitationally stable disk to generate a big red bump of universal Teff~5000K in the disk SED, which can be invoked to explain continuum features of Little Red Dots.

Title: What can the Occult do for You? Using overlapping galaxies to probe dust properties in galaxies

Abstract: Interstellar dust is still a dominant uncertainty in astronomy, limiting precision in, e.g., cosmological distance estimates and models of how light is re-processed within a galaxy. When a foreground galaxy serendipitously overlaps a more distant one, the latter backlights the dusty structures in the nearer foreground galaxy. Such an overlapping or occulting galaxy pair can be used to measure the distribution of dust in the closest galaxy with great accuracy. 

The STARSMOG program uses Hubble to map the distribution of dust in foreground galaxies in fine (<100 pc) detail. Integral Field Unit (IFU) observations will map the effective extinction curve, disentangling the role of fine-scale geometry and grain composition on the path of light through a galaxy. The overlapping galaxy technique promises to deliver a clear understanding of the dust in galaxies: geometry, a probability function of dimming as a function of galaxy mass and radius and its dependence on wavelength. I will present the recent results from Hubble and James Webb observations of the pair VV191 and prospects with the upcoming Roman surveys. 

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