Congratulations to Janosz Dewberry, who has been awarded the 2024-25 Vincent and Beatrice Tremaine Postdoctoral Fellowship in recognition of his outstanding work in developing computational tools for the advancement of astrophysical research.

The Vincent and Beatrice Tremaine Postdoctoral Fellowship was established by Scott Tremaine’s father, Vincent Tremaine, in memory of Beatrice D. Tremaine to honour her lifelong interest in mathematics, science and learning. This award highlights scholars who use applied mathematics and mathematical models to advance astrophysics.

Janosz is an expert in the pulsations of stars and planets. He wrote a sophisticated code on calculating pulsation modes in rotating bodies and produced detailed seismology models for Jupiter, Saturn, and Uranus. Among his single author papers, the 2023 paper “Dynamical tides in Jupiter and other rotationally flattened planets and stars with stable stratification” opened the door to resonances involving a wider range of internal oscillation modes than previously considered.

Dr. Dewberry is a postdoctoral fellow at the Canadian Institute for Theoretical Astrophysics (CITA). As a theoretical astrophysicist with a background in applied mathematics and fluid dynamics, he uses analytical and computational tools to tackle a wide variety of problems. His research program revolves around the dynamics of rapidly rotating astrophysical flows. He studies astrophysical systems ranging from magnetized accretion flows around black holes, to our own JupiterÌý²¹²Ô»åÌýSaturn, to rapidly spinning and tidally interactingÌý²õ³Ù²¹°ù²õ.

Neige Frankel studies the evolution of disk galaxies, using the Milky Way as a model organism at the intersection of cosmological simulations and observations of external galaxies. She is preoccupied with questions like: how did the Milky Way disk form and evolve and how do the spiral arms, central bar, and satellites affect the evolution of the Milky Way stellar disk?

Most recently, her research collaboration with Prof. Jo Bovy and Scott Tremaine led to publications on a range of topics related to the present dis-equilibrated state of our Galaxy. Our Galactic disk seems to be phase-mixing from a recent perturbation. The evidence for this perturbation is best seen in the vertical motion of the stars in the disk, in particular the phase-space plane, (i.e., vertical position – vertical velocity). The density of stars in that plane shows a clear structure that looks like a spiral, dubbed “the Gaia Snail” by the researcher community.

Neige Frankel and her collaborators have worked to quantify this feature to extract information about the perturbation of the disk, which could presumably be due to the passing of satellite(s) or other structures in or around our Galaxy. This work lead to two publications: Frankel, Bovy, Tremaine, Hogg (2023), Vertical motion in the Galactic disc: unwinding the snail, MNRAS), and Tremaine, Frankel, and Bovy (2023), The origin and fate of the Gaia phase-space snail, MNRAS.

Neige Frankel has been a postdoctoral fellow at CITA since September 2021. Prior to this, she completed her PhD work at IMPRS Heidelberg with the thesis: “Forward Modelling the Secular Evolution of the Milky Way Disk” under the supervision of Prof. Hans-Walter.

The Tremaine Fellowship is given annually in memory of Beatrice D. and Vincent J. Tremaine to honour their lifelong interest in mathematics, science, and learning. The award was initially established at CITA by Vincent Tremaine in memory of his wife Beatrice when their son, Scott Tremaine, was the first director.

Dongwoo works on tracing the history of star formation and molecular gas across the first several billion years of cosmic history. They are part of several experiments employing the technique of line-intensity mapping, tracing the implied three-dimensional large-scale distribution of galaxies through fluctuations in the total cosmic emission in specific atomic or molecular lines.

A major research highlight for Dongwoo is the publication of a series of Early Science papers based on the first 13 months of observing with the (COMAP) Pathfinder instrument. Dongwoo led Paper V, which interpreted the Early Science result as an unprecedented upper limit on CO clustering and integrated CO abundance at early cosmic times and forecasts a strong detection of the cosmological CO signal after five years of observing with the COMAP Pathfinder.

Beyond COMAP, Dongwoo works on experiments that target line-intensity mapping with the [C II] singly ionised carbon line. [C II] observations are a key project of the CCAT-prime observatory, which has a significant Canadian contribution. Dongwoo also works for the TIME collaboration as an active contributor to instrument operations and data analysis, participating in the most recent engineering run both on site and remotely.

Leveraging methods for approximate cosmological simulations developed at CITA, Dongwoo has also been investigating new statistical analyses that could be applied to the rich spectroscopic imaging datasets that all of these line-intensity mapping experiments will yield in the coming years.

Dongwoo has been a postdoctoral fellow at CITA since November 2020, with a cross-appointment at the . Prior to this, they completed their PhD work at Stanford University.

The Tremaine Fellowship is given annually in memory of Beatrice D. and Vincent J. Tremaine to honour their lifelong interest in mathematics, science, and learning. The award was initially established at CITA by Vincent Tremaine in memory of his wife Beatrice when their son, Scott Tremaine, was the first director.

Pavel’s research mainly focuses on cosmology, branch of physics that studies the evolution of the Universe on the largest scales.

As one area of his research, he has been using both numerical simulations and experimental data to investigate how to take advantage of measurements of galaxy angular momenta to improve our understanding of how the Universe works. Recently, he was a lead author on a paper that found a link between measured galaxy angular momenta and initial conditions in the nearby Universe, providing an important hint that galaxy angular momenta can serve as a cosmological probe. Potentially, this research avenue promises to help improve reconstruction of the initial conditions of the Universe, probe their non-Gaussianity and search for parity violations in a novel way.

Pavel’s contributions further include several works on the cosmic microwave background, especially regarding its gravitational lensing by the large scale structure and anomalies in the experimental data. Finally, he has also held a long term interest in anisotropies in the fluxes of the ultra-high energy cosmic rays.

Pavel has been a CITA postdoctoral fellow since the fall of 2018. Prior to coming to CITA, he earned his PhD from the University of Chicago.

The Tremaine Fellowship is given annually in memory of Beatrice D. and Vincent J. Tremaine to honor their lifelong interest in mathematics, science and learning. The award was initially established at CITA by Vincent Tremaine in memory of his wife Beatrice when their son, Scott Tremaine, was the first director.

Xinyu’s research focuses on two different aspects of theoretical astrophysics: high energy astrophysics and cosmology. He is particularly interested in the physical mechanisms behind various astrophysical phenomena.At CITA, Xinyu has been working on the astrophysics of compact objects, especially neutron stars and magnetars where strong magnetic fields, outflow and neutrinos can lead to new physics and observational signatures. Together with his collaborators, he proposed a new efficient mechanism of dissipating magnetic energy through the collision of Alfven waves. H
e also performed the simulation of neutron star post-merger disk to study the effect of neutrino fast flavour conversion triggered by the neutrino self-interaction. Such mechanism is found to boost the lanthanide abundances of the r-process nucleosynthesis. Additionally, he demonstrated that strong outflow from compact objects can accelerate the compact object, a new phenomena named as negative dynamical friction.

Apart from that, Xinyu is also interested in the cosmology with Fuzzy Dark Matter, a new dark matter model described a complex scalar field of ultralight bosons. He developed a numerical code and employed it to study the novel small-scale structure from the interference of the scalar field, including soliton cores, vortex lines and filaments. Future observations or non-detections of these small-scale structures may serve to constrain the fuzzy dark matter model.

Before coming to CITA, Xinyu received his PhD in physics from Columbia University in 2019 under the supervision of Prof. Andrei Beloborodov and worked with Prof. Yuri Levin. Both professors are former CITAzens and recipients of the Beatrice and Vincent Tremaine Fellowship.

Laura’s research focuses on understanding the evolution of galaxies and the gas surrounding them. She is particularly interested in creating mock observations that can be compared directly to real data. In this way she gains intuition into the processes that drive galaxy formation.

During her time at CITA, Laura has worked on a variety of topics exploring galaxy formation from different angles. As CITA is participating in many upcoming line intensity mapping experiments, Laura has used the suite of FIRE simulations to make predictions for galactic emission lines. By performing detailed chemical modelling of the gas in the simulated galaxies, she has made maps of the expected CO and [CII] emission.

She has also worked on modelling the contribution to the observed dispersion measure of fast radio bursts from gas in the halo of the Milky Way. By comparing results from different gas profiles, she showed that the Milky Way contribution may be lower than previously thought.

Finally, she is also interested in using quasar absorption lines to understand the reionization history of the Universe. To accomplish this, she runs radiative transfer simulations of hydrogen reionization which she compares with observations to place constraints on the temperature and ionization state of the intergalactic medium at high redshift.

Laura has worked as a postdoctoral research fellow at CITA since 2017. Originally from Ireland, she completed her Ph.D. at the University of Cambridge prior to joining CITA. She will leave CITA in the fall to take up a Marie Skłodowska-Curie fellowship at the Leibniz Institute for Astrophysics Potsdam.

The Tremaine Fellowship is given annually in memory of Beatrice D. and Vincent J. Tremaine to honor their lifelong interest in mathematics, science and learning. The award was initially established at CITA by Vincent Tremaine in memory of his wife Beatrice when their son, Scott Tremaine, was the first director.

Almog’s research focuses on violent astrophysical transients. These transients include gamma ray bursts, tidal disruption events and even planetary collisions, but the best known are supernova explosions. These explosions affect almost every subfield in astrophysics. They regulate the formation of stars in galaxies, produce heavy elements, accelerate cosmic rays and create neutron stars and black holes. Supernovae have been used to measure the history of the expansion of the universe. Some authors claim that nearby supernovae left detectable imprints on earth, affected past climate, and some even go so far as to suggest a supernova could have triggered one of the past mass extinctions. However, despite countless observations and years of theoretical research, we still don’t know exactly what kinds of stars explode as supernovae, or how the explosion mechanism works. The main difficulty here is that when supernova is detected, its progenitor star is already destroyed. The challenge is then to use the post explosion data, and tease out clues about the properties of the star before the explosion. Almog uses a combination of theoretical analysis and state of the art computer simulations to uncover the identity of supernova progenitors. Prior to coming to CITA at 2018, Almog earned his PhD from the Hebrew University in Jerusalem.

The Tremaine Fellowship is given annually in memory of Beatrice D. and Vincent J. Tremaine to honor their lifelong interest in mathematics, science and learning. The award was initially established at CITA by Vincent Tremaine in memory of his wife Beatrice when their son, Scott Tremaine, was the first director.

Thousands of extra-solar planets have been detected by the Kepler satellite. Surprisingly, these exoplanets are not like any of the planets in our Solar system, with the majority of them having sizes between Earth and Neptune and orbits within that of Mercury. Compared to such super-Earths, our Solar system planets are either too small or too far away from the host star. Does this mean our Solar system is a special case?

Wei Zhu, the recipient of this year’s Vincent and Beatrice Tremaine Fellowship, tries to answer this question by combining results from different detection techniques. In a recent study [1], he and his collaborators found that super-Earth systems may not be as common as people had thought. By combining the transit and the transit timing variation (TTV) techniques, they found that planetary systems are very hierarchical: systems with many planets or flat and ordered, whereas systems with few planets are chaotic. Based on this result, they re-evaluated the fraction of stars with super-Earths, and found that stars that do not host super-Earths, such as our Sun, are in fact the majority.

In another work [2], Wei further included the cold giant companions from the radial velocity technique. He found that stars with inner small planets (such as super-Earths) also more likely host outer giant planets (such as our Jupiter). This solar system-like architecture, with small planets inside and giant planets outside, is probably very popular among all types of planetary systems, which again confirms that our solar system is not very special.

Wei has been a CITA postdoctoral fellow since the fall of 2017. Prior to coming to CITA, he earned his PhD from The Ohio State University.

The Tremaine Fellowship is given annually in memory of Beatrice D. and Vincent J. Tremaine to honor their lifelong interest in mathematics, science and learning. The award was initially established at CITA by Vincent Tremaine in memory of his wife Beatrice when their son, Scott Tremaine, was the first director.

[1] ½Û×ÓÊÓƵ 30% of Sun-like Stars Have Kepler-like Planetary Systems: A Study of Their Intrinsic Architecture ()

[2] The Super Earth-Cold Jupiter Relations ()

One of Alexander’s main research activities is the measurement of the gravitational lensing effect in the observed cosmic microwave background (CMB). As CMB photons travel to us through nearly the entire observable Universe, their paths are slightly bent by intervening structure. Although this is a subtle effect, it can be isolated with statistical estimators to create maps of all the matter between us and the CMB last-scattering surface. These maps are sensitive to the evolution of structure across cosmic history and can probe the effects of both dark matter and dark energy. Alexander is involved in the measurement of this effect with current data from the Atacama Cosmology Telescope, and is active in the planning for successor experiments including the Simons Observatory and CMB-Stage 4. He is also involved in theoretical projects exploring the fundamental physics and the astrophysics that can be learned using upcoming CMB datasets, both on their own and together with cosmological data at other wavelengths.

Prior to coming to CITA as a postdoctoral fellow in the fall of 2014, Alexander earned his PhD from McGill University and was a postdoctoral researcher at Stony Brook University.  He has been a CITA senior research associate since the fall of 2017.

The Tremaine Fellowship is given annually in memory of Beatrice D. and Vincent J. Tremaine to honor their lifelong interest in mathematics, science and learning. The award was initially established at CITA by Vincent Tremaine in memory of his wife Beatrice when their son, Scott Tremaine, was the first director.

Joel Meyers is the 18th recipient of the Vincent and Beatrice Tremaine Fellowship awarded annually for outstanding research at the Canadian Institute for Theoretical Astrophysics. He was chosen for his theoretical work aimed at utilizing observations of the cosmic microwave background to probe fundamental physics. His research has helped to clarify the observational signatures of new light particles and has also developed novel methods for exploring the details of cosmic inflation. Also, Joel has been actively involved in developing the science case for a proposed next generation cosmic microwave background experiment known as CMB-Stage IV.

Joel has published several papers on various aspects of early universe cosmology. His papers from the past year include:

Observed maps of the cosmic microwave background are distorted by gravitational lensing of photons due the mass intervening along the line of sight. In this paper, Joel and his collaborators explore the degree to which this distortion can be measured and removed from the maps, a procedure known as delensing. They show that this procedure can be carried out to high precision with upcoming experiments which improves the ability of such experiments to measure parameters related to the contents and history of the universe. Delensing can be done at no additional experimental cost, and leads to improvements in the scientific output which would otherwise require significantly increasing the sensitivity and cost of the experiment.

In this work, Joel and his collaborators explore a novel method for constraining the physics of the early universe. Several ongoing and upcoming experiments are focused on measuring B-mode polarization of the cosmic microwave background, which would give strong evidence that a period of very rapid accelerating expansion known as cosmic inflation took place in the early universe. In the simplest models of inflation, the B-modes are expected to very nearly obey Gaussian statistics. This paper explores to what degree upcoming experiments could measure deviations from Gaussianity, a detection of which would signal a significant departure from the simplest models of inflation.

The gravitational influence of light particles present in the early universe, including the neutrinos of the Standard Model, left observable signatures in the fluctuations of the cosmic microwave background. This paper explores one such signature, the phase shift of the temperature and E-mode polarization power spectra, which is particularly robust and characteristic of the presence of light particles in the early universe. This work demonstrated how observation of the phase shift can be used to robustly detect the presence of light particles and also to probe some of their properties both with existing data and with future observations.

Joel has been a senior research associate at CITA since the fall of 2012, before which he earned his PhD at the University of Texas.

The Tremaine Fellowship is given annually in memory of Beatrice D. and Vincent J. Tremaine to honor their lifelong interest in mathematics, science and learning. The award was initially established at CITA by Vincent Tremaine in memory of his wife Beatrice when their son, Scott Tremaine, was the first director.