Dr. Ananthan Karunakaran
Postdoctoral fellow, University of Toronto

Abstract

With the advent of modern wide-field sky surveys and improved astronomical instrumentation, we have been able to probe further down the galaxy luminosity and mass function. One of the most intriguing discoveries from the last decade in this regime is a large population of extremely faint, extended galaxies called Ultra-Diffuse Galaxies (UDGs). The sheer quantity and diversity of these objects have led to many follow-up studies, both observational and in simulations, to understand how these peculiar objects form and evolve. In this talk, I will present our efforts to constrain UDG formation and evolutionary mechanisms via neutral hydrogen (HI) observations. I will also briefly discuss some of the ongoing comparisons between our sample and hydrodynamical simulations before highlighting planned paths forward with next-generation facilities.

Timbits, coffee, tea will be served in STI A before the colloquium.

Guest Speakers:
Gregg Wage (RMC/Queen’s), Chris Spencer (Queen's), with Mark Richardson as host (McDonald Institute/Queen’s)

Astronomy on Tap in Kingston is continuing in person!!

This free event is in the Living Room of The Mansion (506 Princess St, Kingston) on March 7th at 6:30 pm.

Astronomy on Tap is a series of worldwide events where professional astronomers give informal talks at a local bar on topics of a broad interest in astronomy and astrophysics. This particular event will be a bit different than in the past – we will host two fantastic astronomers & geologists: Gregg Wade and Chris Spencer who will go head-to-head in a debate over the sun vs moon in preparation for the April 8th total solar eclipse. The event will be hosted by local astro-buff, Mark Richardson. There will be time for questions and discussion, and the speakers and other local scientists will mingle with the audience between and after the talks, providing lots of opportunities to chat with some keen astronomers. There will also be a trivia session with questions related to astronomy with prizes given out to the winners!

The event is free and open to all ages. The Mansion serves alcohol and non-alcoholic drinks, and food will be available to be ordered.

Astronomy on Tap will be upstairs as you come inside.

Space is limited, so we encourage you to arrive on time! Pre-show starts at 6:30pm, with the main event starting at 7pm.

For more information or if you have any questions, please send us an email to Outreach@McDonaldInstitute.ca or contact us through our Facebook page.

Target Audience: Everyone welcome!

Hosted by: Queen's Physics Department & the McDonald Institute
Contact: AoTKingston@gmail.com

Nicolas Cowan
Dept. of Earth and Planetary Sciences,
McGill University

Abstract

Three decades of searching  have revealed that planets are abundant in the Galaxy, but most are unlike those found in the Solar System. Lava planets are among the strangest exoplanets discovered so far. Their bulk density suggests an iron core surrounded by a rocky mantle, like Earth. But they orbit so close to their star that they are tidally locked into  synchronous rotation: their permanent dayside is hot enough to melt —and vaporize— rock, while their nightside is expected to be cold and airless. Until lava planets were discovered, nobody had imagined the wild geophysics of such an asymmetric world: supersonic silicate winds, and a permanent, hemispheric magma ocean. I will review current scenarios for the formation, interior structure, and atmosphere of lava planets, and how we are pushing back the boundaries of our ignorance with numerical simulations and astronomical observations.

Aephraim M. Steinberg
Professor of Physics, Centre for Quantum Information and Quantum Control
Department of Physics, University of Toronto

cqiqc.physics.utoronto.ca

Abstract

If there are two problems you would think quantum mechanicists and quantum opticians had beaten to death, they might be quantum tunneling and the propagation of photons through a cloud of atoms.

And yet when you look more deeply – and ask "where are the atoms while they’re tunneling through the forbidden region, and how much time do they spend there?" or "how do photons get slowed down, and where is the energy spending its time?" – the answers are not so simple.

This is related to a simple reality: one of the most famous tidbits of received wisdom about quantum mechanics is that one "cannot ask" how a particle got to where it was finally observed, e.g., which path of an interferometer a photon took before it reached the screen. What, then, do present observations tell us about the state of the world in the past? I will describe two experiments looking into aspects of this “quantum retrodiction.” In the first, we measure how long Bose-condensed atoms spend inside a potential barrier (created by a far-detuned laser beam focused to 1 micron) before being transmitted; I will also talk about some predictions regarding what insidious effects actually observing a particle in the barrier could have. In the second, we measure the amount of time atoms spend in the excited state when a resonant photon is not absorbed by those atoms, but propagates clear through. We find, surprisingly, that the answer need not even be a positive number. I will connect this to better-known aspects of optical propagation.

Some References

[1] Measuring the time a tunnelling atom spends in the barrier, Ramón Ramos, David Spierings, Isabelle Racicot, & Aephraim M. Steinberg, Nature 583, 529 (2020).
[2] Observation of the decrease of Larmor tunneling times with lower incident energy, David C. Spierings, & Aephraim M. Steinberg, Phys. Rev. Lett. 127, 133001 (2021).
[3] Spin Rotations in a Bose-Einstein Condensate Driven by Counterflow and Spin-independent Interactions, David C. Spierings, Joseph H. Thywissen, & Aephraim M. Steinberg, cond-mat/2308.16069 (2023)
[3] Measuring the time atoms spend in the excited state due to a photon they do not absorb, Josiah Sinclair, Daniela Angulo, Kyle Thompson, Kent Bonsma-Fisher, Aharon Brodutch, & Aephraim M. Steinberg, PRX Quantum 3, 010314 (2022).
[4] How much time does a resonant photon spend as an atomic excitation before being transmitted?, Kyle Thompson, Kehui Li, Daniela Angulo, Vida-Michelle Nixon, Josiah Sinclair, Amal Vijayalekshmi Sivakumar, Howard M. Wiseman, & Aephraim M. Steinberg, quant-ph/2310.00432 (2023)