Strong gravitational lensing occurs when a very massive object (such as a galaxy or galaxy cluster) lies between us and a more-distant background galaxy.  If the configuration is just right, the massive object (i.e., the lens) bends the path the light (from the background galaxy) travels, creating these multiple, distorted images of the background galaxy.  Not only do these systems look spectacular, they also offer the interesting probes into astrophysics, which I discuss below (for specifics on my research, see next section below):

Utilizing transient events, these systems can be used to constrain the Hubble constant (H0), or the expansion rate of the universe.  When one of these events (such as a supernova or quasar fluctuation) occur in the background (or source) galaxy, we observe the event multiple times because of the multiple lensed images.  Most importantly, these events are observed with a time delay.  Assuming the lens mass profile is accurately modeled (let's say ignoring systematic effects such as the mass-sheet degeneracy, which I'll talk about later), the time delays we measure/estimate should be inversely proportional to the Hubble constant!  

One of the major issues with this approach is the so-called mass-sheet degeneracy (MSD).  To demonstrate this, if we were to put a theoretical infinitely-thin and flat mass sheet perpendicular to our line of sight, while simultaneously dimming the background galaxy luminosity by a specific amount, we would observe the same exact system from a time-independent perspective.  However, the time delays would differ, which in turn would affect our Hubble constant measurements.  Ways to break this degeneracy include using standardizable transients (such as lensed Type Ia supernova), or utilizing stellar kinematic information to separate the luminous to the dark matter surface density contribution.

Dark matter is theorized to not interact with light; in other words, it is basically invisible to typical imaging/spectroscopic observations.  However, we are able to detect their gravitational effects (hence how we know it exists), which makes gravitational lensing so valuable.  We can model the matter density profile of the lens galaxy accurately by studying the lensed features of the source galaxy.  Especially at higher redshifts, strong gravitational lensing remains the best method of estimating galaxy-scale dark matter halos.  Given there are tensions between what we expect of dark matter halo profiles from simulations and local observations, strong lensing can be used to study the evolution of these dark matter halos with redshift.  

In certain cases, these systems can be used to constrain dark energy cosmology.  This is only really applicable when there are two source galaxies (at different redshifts) that are being lensed, or so-called compound lenses.  While these cases are rare, they give the unique advantage of being able to measure the ratio of time-delay distances, which is independent of the Hubble constant, and hence being able to constrain the dark energy equation of state (w), as well as the cosmological total matter density (Ωm).  

Lastly, and probably the most intuitively obvious application of strong lensing, are for high redshift observations.  Much like a typical glasses lens, the lens galaxy can magnify the background galaxy, allowing us to see things that would otherwise be too faint to observe, or with much higher clarity.  Strong lensing helped the James Webb Space Telescope (JWST) observe the furthest galaxies ever observed up to this point (z > 12).  In specific instances of cluster lensing, extremely microlensed stars (at z > 1) can even be observed and studied.

These are only some of the applications strong lensing offers to the field of astrophysics; the field and community are still coming up with new ideas and discoveries regarding strong gravitationally lensed systems!

In my undergraduate career at UC Berkeley, I first began as an research intern at the Lawrence Berkeley National Lab (LBNL) for the Dark Energy Spectroscopic Instrument (DESI) being constructed in the spring and summer of 2019.  Specifically, I worked on data validation and quality assurance software for the telescope, led under Dr. Stephen Bailey.  

I then transitioned into a strong lensing group at LBNL headed by Prof. Xiaosheng Huang, where I mainly focused strong lens searches in the DESI legacy imaging survey for the first few years.  From this, I led papers on searches for retrospective lensed supernovae and lensed quasars, respectively.  Additionally, in collaboration with the ASTRO3D Galaxy Evolution with Lenses (AGEL) group, I modeled and published a paper on the compound cluster lens DESI-090.9854-35.9683, dubbed "the Carousel Lens."  

I currently attending graduate school at UCLA, with Prof. Tommaso Treu as my advisor.  My research now revolves around the analysis of these strong lenses, from modeling and dark matter decomposition of the Strong Lensing Legacy Survey (SL2S) lenses, to the resolved kinematics examination of multiply-lensed-quasars systems.  This is all in collaboration with the Time⁠-⁠Delay Cosmography (TDCOSMO) group.  In this time, I also worked with Dr. Justin Pierel on the search for lensed supernovae within JWST data.  I am currently also involved in the Vast Exploration for Nascent, Unexplored Sources (VENUS) collaboration, working with Prof. Seiji Fujimoto to perform multi-plane cosmography with JWST observations of cluster lenses.  

For specifics on the topics discussed, check out my papers, or contact me!