About Me

My name is Thomas Lai(賴劭愉). I am a postdoctoral scholar at Caltech/IPAC, collaborating with Dr. Lee Armus. My current research interests include undertanding the starburst-AGN connection and how they impact the ambient interstellar medium through fueling and feedback processes, constraining the mid-infrared extinction profile, studying dust properties under different environments, and building models for spectral decomposition.

I received my PhD at the University of Toledo, working with Prof. JD Smith and Prof. Adolf Witt on the behavior of dust grains in interstellar space, with the thesis entitled: "Exploring Small Dust Grains Across Different Galaxy Environments." I received my bachelor degree in Space Science & Engineering from National Central University, Taiwan. Later on, I was more intrigued by the distant Universe and decided to switch field from space science to astronomy. Prior to my graduate study, I worked as a research assistant with Ciska Kemper at ASIAA, where I found my interest in studying the interstellar medium.

Contact Details

Thomas Lai
MC 314-6 (Keith Spalding Building)
1200 E California Blvd, Pasadena, CA 91125

shaoyu AT ipac.caltech.edu


All About Dust

I am interested in understanding the properties of the dust grains in interstellar space. How do those grains form? How do they get destroyed? How can they survive in the harsh interstellar environment? We know that interstellar dust grains in galaxies absorb energy from starlight and reradiate at optical and infrared (IR) wavelengths. Almost half of all the non-primordial radiation in the Universe has gone through such re-emitting process. Thus dust plays an integral role in galaxy evolution and star formation, regulating the flow of radiative energy across the galaxies.

In particular, my research has been focusing on the behaviors of the small dust grains by studying spectra from polycyclic aromatic hydrocarbons (PAHs), extended red emission (ERE), and diffuse interstellar bands (DIBs). One key question yet to be answered about these small interstellar grains is: how do these small and fragile particles survive in such harsh UV radiation fields near sites of star-formation. To address this issue, I performed a detailed investigation of a sample of 437 extragalactic objects with complete spectral coverage from 2.5—38 μm drawn from an exhaustive cross-archival match between the AKARI IRC point source catalog and the Infrared Database of Extragalactic Observables from Spitzer (IDEOS) catalog. My main focus is on the 3.3 µm PAH emission since among all the other PAH bands, it serves as the best tracer of the smallest grains.

I also worked on the DIBs and ERE. Both of these two phenomena share a common mystery: even though they have been observed for decades and extensive research had been conducted, the carriers of these two interstellar phenomena are still unidentified. In the past, DIBs and ERE were being studied separately. But in my study, I discovered they have quite a lot of properties in common, making us to wonder whether they shared similar origin.

Research Interests

  • Behaviors of small dust grains in interstellar space
  • The survival of grains in environments with penetrating UV radiation fields
  • Modeling dust features in the mid-infared (MIR) spectra
  • Preparing science for the upcoming JWST mission
  • Constraining MIR extinction curve


In my leisure time I enjoy hiking and photographing. Here are some photos that I took at places that I have been to in the past.


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