Department of Astronomy Center for Radiophysics & Space Research

Tsz Kuk (Daisy) Leung

Professor Dominik Riechers
Tsz Kuk (Daisy) Leung

Research areas:
Galaxy evolution, ISM and star formation of high-redshift galaxies, radio & (sub-)millimeter astronomy. 

My research seeks to improve our current understanding of the environments and the physical mechanisms that trigger star-formation across cosmic time in order to attain a coherent picture on how galaxies and supermassive black holes evolve through the history of the universe.

Current studies find evidence that most galaxies undergo the transition from a “normal” star-forming phase into an AGN phase as they evolve. To examine this postulation, it is necessary to conduct detailed investigation of the environment to address the more fundamental questions, e.g., i) How much gas is available to fuel star-formation and AGN growth? ii) How do the gas excitation conditions in the interstellar medium (ISM) differ from “normal” star-forming galaxies to AGN host galaxies? iii) Does the presence of an AGN enhance or quench star-formation in its host galaxy? It is by answering these questions that we will be able to place different populations in an evolutionary context. I am thus an observationally-driven astronomer with a focus on utilizing measurements obtained with large radio and (sub-)millimeter wavelength interferometric telescopes to scrutinize the evolution of the gas and dust components in the interstellar medium of galaxies at high redshifts.


Publications:

Dominik A. Riechers, T. K. D. Leung et al., "Rise of the Titans: A Dusty, Hyper-Luminous "870 µm Riser" Galaxy at z~6",  submitted to the ApJ

N. Patra, A. Parsons , D. DeBoer, N. Thyagarajan , A. Ewall-Wice , G. Hsyu , T. K. Daisy Leung et al,. "The Hydrogen Epoch of Reionization Array Dish III: measuring chromaticity of prototype element with reflectometry", submitted to the ApJ

H. Nayyeri, A. Cooray, E. Jullo, D.A. Riechers, T.K.D. Leung et al., "Herschel and Hubble study of a lensed massive dusty starbursting galaxy at z~3", submitted to the ApJ

T. K. Daisy Leung & Dominik A. Riechers & Riccardo Pavesi, "Moleuclar gas kinematics and star formation properties of the strongly-lensed quasar host galaxy RXS J1131-1231", in press, https://arxiv.org/abs/1701.07830v1

T. K. Daisy Leung & Dominik A. Riechers, "A massive molecular gas reservoir in the z=2.221 type-2 quasar host galaxy SMM J0939+8315 lensed by the radio galaxy 3C220.3", 2016 ApJ 818:196, http://arxiv.org/abs/1601.04172

Shane Bussmann, T.K. Daisy Leung & Alex Conley, "UVMCMCFIT", 2015, doi: 10.5281/zenodo.27357

Nipanjana Patra, Zaki Ali, Carina Cheng, Dave DeBoer, Gilbert Hsyu, Tsz Kuk Leung, Aaron Parsons, "HERA dish reflectometry memo", http://reionization.org/wp-content/uploads/2015/01/HERAMemo_9_dish_reflectometry.pdf

 

I am a third year graduate student working with Professor Dominik Riechers on studying the interstellar medium (ISM) properties of distant galaxies. Despite great progress made in studies of galaxy formation and evolution over the past decade, we are only beginning to fully understand how galaxies interact and evolve, and which key mechanisms are responsible for driving the bulk of stellar mass assembly in the universe. Since the ISM is the natal environment from which stars are formed, tracing the molecular cold gas in the ISM — the immediate fuel for star formation — via e.g., carbon monoxide (CO) molecules is particularly important. By characterizing the ISM of these distant galaxies, my research aims to improve our current understanding of how galaxies and their supermassive black holes were formed in the early universe and how they have evolved since then. Most of my research is done by observing the light that was emitted billion years ago using arrays of telescopes (interferometers) that operate at radio and sub-‚Ā†millimeter wavelengths. For instance, some of my work has made use of the data collected from the Submillimeter Array, which is shown in the background of this photo.

 

Being able to think that my work has an impact on the quest of uncovering the mysteries of the universe that has always been a common goal to all human beings is the impetus to my work. Beyond my research contributions to the field, I also value my work as a teaching assistant, an important role that allows me to share my fascination towards the subject of astronomy with undergraduate students. It is my humble wish that I too can spark interests in our students at Cornell who may one day become future scientists.

 

As someone brought up in the tropics, I do not enjoy dealing with the brutal winters here in Ithaca, but as I reflect on the past two years here, I have never regretted my decision of coming to Cornell to pursue my doctoral degree, thanks to the group of supportive colleagues and my advisor who have provided me with an excellent learning environment.

Besides work, I enjoy exploring outdoor sceneries, hiking and doing landscape photography. I have been taking timelapse videos around Ithaca that I anticipate to release when I graduate.