Star Formation Histories of SAGA Satellites

Proposed quenching mechanisms including gas starvation or strangulation, tidal stripping, or ram pressure stripping operate on different timescales as a function of stellar mass. Star formation histories (SFHs) can provide constraints on how long a galaxy has been quenched or how long it takes to transition from star forming to quiescent. Additionally, there is a known dichotomy between quenched Local Group dwarf satellites and star forming isolated dwarf galaxies. This implied transition from star forming in isolation to quenched as a satellite is indicative of a strong environmental dependence on quenching, and a rapid transition from star forming to quiescent upon infall. I work with the Prospector SED fitting software to investigate the SFHs of SAGA satellites and effect of environment.

Undergraduate Research

I was a member of the LIGO/Virgo Collaboration between January 2018 and September 2020, and below are summaries of the various projects I was involved in.

Resonant Excitations in Exotic Compact Objects

National Dutch Institute for Subatomic Physics (Nikhef)

Exotic Compact Objects (ECOs) are alternatives to the black holes of classical general relativity that may have similar masses and densities with additional features beyond the standard model. For instance, if dark matter is composed of fermionic particles then they may form star-like objects supported by degeneracy pressure: dark matter stars. Boson stars are another potential ECO where a macroscopic object is composed of scalar fields. Gravitational waves (GWs) from presumed binary black hole mergers are now being detected on a regular basis with the Advanced LIGO and Advanced Virgo interferometers. ECOs have not yet been observed, but one method of distinguishing them from classical compact objects predicted by general relativity is studying GW signals as ECOs could leave an imprint upon the GW signal in a variety of ways. One such effect is the presence of resonant excitations spring inspiral. When the gravitational wave frequency during inspiral matches the internal resonant frequency of an ECO, orbital energy will be taken away resulting in a jump in orbital phase relative to point particle phasing. We found that resonances with resultant phase shifts of order unity or larger can be detectable with second-generation interferometers, using Bayesian model selection. We have since applied our analysis method to detections in the GWTC-1 catalog from the first and second observing runs of Advanced LIGO and Advanced Virgo, finding consistency with the binary black hole nature of the sources. Our results were accepted for publication in PRD and the corresponding paper can be found here.

The Advanced LIGO Timing System

Columbia Experimental Gravity Group (GECo)

Precise time stamping of gravitational wave (GW) signals is crucial for GW detection using a network of detectors. Reliable and accurate timing between interferometers is essential for many aspects of GW science, one example being the recovery of the source direction. Additionally, timing at different parts of a given detector also needs to be highly synchronized. I work on the timing diagnostic system for LIGO, which performs critical checks to ensure the system is robust, fault tolerant, and returns precise results. Prior to the start of LIGO’s third observing run (O3) in April of this year, I wrote a program that performs real time, continuous diagnostics with alerts for system failures on two of the timing subsystems. I have also visited both the LIGO Hanford Observatory and the LIGO Livingston Observatory to check timing hardware over the past few years. Throughout O3, I’ve performed checks and published internal LIGO documents on timing data for all open public alert candidates, as well as long term diagnostics for the duration of the run.

Low-Latency Algorithm for Multi-messenger Astrophysics (LLAMA) Subthreshold Searches

Columbia Experimental Gravity Group (GECo)

LLAMA is multi-messenger astrophysics framework and search pipeline that has primarily been used to search for common sources of gravitational waves and high energy neutrinos. LLAMA provides a reliable and flexible framework that can be run for both real-time searches and for offline analyses. Finding neutrino counterparts to GWs is critical for real time multi-messenger science as it can significantly improve the sky localization for further astronomical follow-ups. We are currently working on adapting the pipeline to find subthreshold coincident candidates using data from LIGO’s third observing run and IceCube. I have contributed to the subthreshold searches by generating background distributions for our study.