I'm interested in strongly lensed galaxies and quasars due to their applications in studying the lens galaxies (their stellar initial mass function, mass distribution, and inner structure) and cosmological measurements (time-delay cosmography). Currently, I'm working on a standardized method for kinematic measurements of lens galaxies in the strongly lensed galaxy-quasar systems. Before this, I worked on photometric redshift estimation of strongly lensed galaxies.
The detection of luminous quasars at z > 6 suggests that supermassive black holes (SMBHs) of > 1e+8 solar mass were in place when the universe was younger than a Gyr. This rapid growth is not theoretically understood, with observational evidence favoring neither of the popular SMBH evolution models. Massive black holes (MBH) grow through accretion and mergers. Hence, probing the demographics of MBH mergers allows for discrimination between the SMBH evolution models. The gravitational wave (GW) emission from most of these mergers lies within the frequency range of the Laser Interferometer Space Antenna (LISA). The high signal-to-noise (SNR) ratio “individually-resolvable” mergers are expected to be rare, therefore not providing a statistically-powerful probe of their underlying population. Nevertheless, the superposition of lower SNR mergers emits a stochastic GW background that can be used to probe the cosmic distribution of MBHs. We developed an MCMC algorithm which can constrain the cosmic distribution of SMBHBs based on their detected stochastic signal. We showed that it is possible to put strong constraints on the cosmic distribution of MBH mergers at the highest redshift (z > 10) and the lowest mass bins (M < 1000 solar mass).