My Work
A high spatial resolution view of the hot gas in the most distant galaxy cluster.
ReCESS
The Representative Cluster Evolution SZ Survey (ReCESS) is a project that studies the intracluster medium (ICM) in galaxy clusters at high redshifts (z > 1.25) using the Sunyaev-Zel'dovich (SZ) effect at arcsecond scale resolution. By examining these high-z clusters, initially selected through ACT observations, I aim to study their dynamical states, morphology, and evolutionary processes, as I explain in this talk.
Recently, we secured over 150 hours of observing time on the Green Bank Telescope (GBT) and ALMA+ACA to systematically follow up on all z > 1.25 clusters detected by ACT. These observations will allow us to study clusters during their most active growth periods and address systematics in cluster cosmology measurements at these uncharted epochs.
Maria
I developed a versatile, user-friendly simulator to optimize scanning strategies and instrument designs to efficiently reduce atmospheric noise and filtering effects. I use this tool to produce synthetic time streams and maps from hydrodynamical simulations, enabling a fair comparison between theory and reality. To generate synthetic time-ordered data, I developed a multi-purpose telescope simulator name maria, which implements a suite of telescope and instrument designs intended to mimic current and future facilities. Each mock observatory scans through the atmosphere in a configurable pattern over the celestial object. maria generates evolving and location-and-time-specific weather for each of the fiducial sites using a combination of satellite and ground-based measurements.
See this talk for more info! For a detailed description of the tool and tutorials on how to use it, please visit www.thomaswmorris.com/maria (or click on the link below).
Maria simulated atmosphere
The epoch of Reionization
I helped write an ALMA DDT proposal to observe FIR lines targeting a galaxy at z>10. The proposal was successful, and the data was published in Kaasinen,van Marrewijk+2023. For this study, I developed a novel technique to robustly quantify the likelihood of faint emission lines being real. We further applied this technique to all archival ALMA observations targeting galaxy candidates at z>10 (van Marrewijk, Kaasinen + 2025). Sadly, we didn't detect any galaxy at z>10 in the sub-mm regime. The tool is publically available and presented with easy-to-use tutorials:
My master’s
I have done my master’s in Leiden. There, you do two master theses. With the first thesis, I kept busy with what drives star formation in starburst galaxies at the cosmic noon. In this master thesis (supervised by J. Hodge and M. Rybak), I developed an advanced data analysis technique that searches for weak spectral lines in distant galaxies through a matched filter in the uv-plane. Here, I detected the first HCO+(4-3) line in a high redshift SMG. This detection was visible in the image plane with a resolution of 20 mas! My work is continued in a series of papers that will characterize how dense gases are manifested in a large sample of starburst galaxies.
With my other thesis (supervised by H. Hoekstra and S. Debackere), I looked at how small-scale clumping in the ICM affects the X-ray luminosity—halo mass relationship. To study systematics, I created a phenomenological model based on hydrodynamical simulations that create mock observations of galaxy clusters in the X-ray for varying clumping properties.
