I am working with Prof. Dominik Riechers and Dr. Shane Bussmann at Cornell University to study the interstellar medium of lensed, dusty, star-forming galaxies at high redshifts. My research is based on my interests in following areas:
- the study of the cold, dense molecular gas in the ISM of these galaxies
- understanding the instrinsic properties of the high z population
- galaxy formation and evolution through cosmic time
- techniques in radio/submillimeter astronomy
- statistical inferences and analyses on large samples of the high z population
RXJ1131-1231 (Leung et al. 2017)... To be updated
SMM J0939+8315 (Leung et al. 2016)
In our recent paper, we use telltale emission from carbon monoxide (CO) molecules to trace the properties of the molecular gas within a gravitationally lensed, dusty, star-forming galaxy (SMMJ0939+8315) which also harbors a voracious galactic black hole at a (comoving) distance of ~18 billion light-years away, and the observed emission was emitted at an epoch only ~3 billion years after the Big Bang ( Leung & Riechers 2016). Investigation of the interstellar medium properties of SMMJ0939+8315 is particularly exciting and important as it presents an unique opportunity to peer into the early universe when the most intense bursts of star formation are taking place.
The alignment of two intervening galaxies and their surrounding dark matter acts as cosmic lenses magnifying the light emitted by SMMJ0939+8315. Our analysis reveals that the observed brightness of SMMJ0939+8315 is magnified by a factor of more than 10 times, making it one of the most apparently luminous dusty sources detected at vast distances away from us.
Our observations reveal a massive molecular gas reservoir residing in SMMJ0939+8315, which is being converted into young stars at a colossal rate (~500x times faster than the Milky Way). Our findings also suggest that a substantial amount of (the CO-emitting) gas has already been converted into stars and used for feeding the active galactic nucleus (AGN). Hence, we may be witnessing an immediate stage in the evolution of a massive galaxy between a starbursting phase and an unobscured AGN-dominated phase, in which the galactic black hole in this galaxy is growing rapidly. This is a crucial step forward in the understanding of how galaxies evolve in their early phases, as well as providing constraints on cosmological structure formation.
I worked on HERA (the Hydrogen Epoch of Reionization Array) / PAPER (Precision Array to Probe the Epoch of Reionization) with Prof. Aaron Parsons, a professor at UC Berkeley from June 2013 - June 2014 before going to Cornell University for my PhD. My work mainly consists of modification on the design, construction and data analysis on the building prototypes (instrumentation). The goal is to build 568 dipole antennas / radio telescopes in South Africa in hope of detecting the 21cm at z ~ 13 - 6.
HERA will answer some of the questions current scientists have: the properties of the high redshift galaxies, how they affected the evolution of the Universe, and whether the standard cosmological model describe the Universe during the dark ages. A video is uploaded by Aaron Parsons explaining the Epoch of Reionization and how it relates to the Universe as a whole: click here for video.
I split half the time working on the constuction of the prototype and the remianing on characterizing the instrument responses and time domain reflections for the feed using electrical analyzers.