Research

Identifying recoiling AGN candidates in optical imaging survey data.

During a galaxy merger, the supermassive black holes of the two galaxies also combine to form one larger black hole. However, odd characteristics can sometimes cause asymmetric gravitational waves to be emitted during the merger process. This causes the newly-merged black hole to be ejected from the center of the galaxy. These objects are called recoiling active galactic nuclei (AGN), and they can give us important insight into the spin and mass evolution of black holes.

The problem is that less than a dozen recoiling AGN candidates have been found by previous studies. This is due to the computationally-intensive imaging analysis and spectroscopy that is often required to identify them. To rectify this, I’ve worked with Dr. Suvi Gezari and Prof. Priyamvada Natarajan to create a new, faster method to identify recoiling AGN candidates using only information from optical imaging survey data.

Through this new method, I’ve identified five new candidates and recovered two previously-identified candidates in Pan-STARRS data. This new method will allow us to find many more recoiling AGN candidates in data from the future Vera Rubin Legacy Survey of Space and Time (LSST).

A paper on our most exciting new candidate will be submitted to The Astrophysical Journal in 2024. See my 2023 AAS iPoster and my 2022 talk on this work. [Image courtesy DESI Legacy Survey.]

Barred galaxies in the TNG50 simulation and in HSC-SSP observations.

About two-thirds of local disk galaxies contain a bar. Bars are important to the secular evolution of disk galaxies, but it’s unknown at which stage in a galaxy’s evolution they are most influential. One way to help quantify this effect is to precisely measure the fraction of galaxies at different masses that contain a bar.

Previous studies have measured bar fractions in simulations and in observations, and have concluded that simulations produce different bar fractions compared to in imaging surveys. However, these previous studies often made unfair comparisons because they used different methods to detect bars in simulations versus observations.

I’ve worked with Dr. Hua Gao and Prof. Eugene Magnier to perform a fair comparison on the detectability and characteristics of bars in the TNG50 run of the IllustrisTNG cosmological simulation versus in multiwavelength data from the Hyper-Suprime Cam Subaru Strategic Program (HSC-SSP). We found that TNG50 overproduces bars in high-mass galaxies and has a deficiency of short bars compared to HSC-SSP.

See my 2024 AAS iPoster and my 2023 talk on this work. [Image courtesy NASA/ESA.]

Evolution in the orbital period of a binary black hole star system.

GRO J1655-40 is an x-ray binary consisting of a star orbiting a black hole. In 2005, this system went into outburst, and a large amount of mass moved away from the star and into the black hole’s accretion disk. By the conservation of angular momentum, this must have caused a change in the orbital period of this system.

I worked with Prof. Charles Bailyn to obtain an upper limit on the new post-outburst orbital period of the system. I performed photometry and analyzed twenty years of multiwavelength data from the Small & Moderate Aperture Research Telescope System (SMARTS), and created a pipeline to reduce infrared data from SMARTS.

[Image courtesy NASA/CXC/M.Weiss.]