Colloquia
Colloquia & Current Events 2023 - 2024
Colloquia Abstracts
SUBJECT TO CHANGE! Be sure to check back often
A&P Colloquium series
To obtain the Zoom link for any online event, please email the Astronomy and Physics Department Secretary, Shannon Rhode, at s.rhode@smu.ca. Colloquia are not recorded.
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When stellar evolution takes a break: A 10-billion-year pause in white dwarf cooling
Dr. Simon Blouin (University of Victoria)
Date: Friday 1 March 2024
Time: 3:00-4:00 pm
Location: Remote (via Zoom), streamed in AT101
White dwarfs are stellar remnants devoid of a nuclear energy source. They cool down over billions of years and eventually freeze into a solid state. It was recently discovered that some white dwarfs maintain a constant luminosity for a duration comparable to the age of the universe. This surprising finding challenges the conventional portrayal of white dwarfs as dead stars that inexorably cool down. Over the past few years, much work has gone into identifying the nature of the energy source that prevents these white dwarfs from aging. In this talk, I will show how a solid–liquid distillation mechanism involving neutron-rich impurities interrupts white dwarf cooling for billions of years and explains all the observational properties of the unusual delayed population.
Dr. Melina Avila (Argonne National Lab)
Date: Friday 8 March 2024
Time: 3:00-4:00 pm
Location: In-person, AT101
Dr. Daryl Haggard (McGill University)
Date: Friday 15 March 2024
Time: 3:00-4:00 pm
Location: In-person, AT101
Dr. Bill Harris (McMaster University)
Date: Friday 22 March 2024
Time: 3:00-4:00 pm
Location: In-person, AT101
March 29: Good Friday - no colloquium
TBC
April 5:
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Oppenheimer, Groves, and the Atomic Bomb: How the Manhattan Project Came to Be
Dr. Cameron Reed
Date: Friday 15 September 2023
Time: 3:00 - 4:00 PM (ADT)
Location: Atrium 101
The Manhattan Project was the United States Army’s program to develop and deploy fission weapons in World War II. After two and a half years of intense work and great expense, Project scientists succeeded in developing two very different designs for fission bombs, one of which used uranium and the other plutonium. One bomb of each type was dropped on Japan in August 1945 and helped to bring the war to an end. In this talk I will give an overview of the Manhattan Project, touching on its origins, organization, major personalities, facilities, accomplishments, challenges encountered, some of the physics of nuclear explosions, and why two different bomb designs were necessary. I will also describe the context of the war in the summer of 1945 and the effects of the bombs.
What have we learned about Galaxy Formation from the First Year with JWST?
Dr. Casey Papovich (Texas A&M University)
Date: Friday 22 September 2023
Time: 3:00 - 4:00 PM (ADT)
Location: via Zoom, streamed in AT101
In its first year, JWST has given us an amazing view of what galaxies looked like during the immediate period after the Big Bang. The JWST observations have led to a series of discoveries, many of which were wholly unexpected. In this talk, I will present some of this work using JWST imaging and spectroscopic from ``deep fields''. I will focus primarily on key results enable by the CEERS (the Cosmic Evolution Early Release Science) Survey as well as data from JWST deep fields. These results include the discovery and characterization of the properties of galaxies at the earliest times, with redshifts of 7 and higher, during the cosmic period known as reionization. The properties of these galaxies imply they are dominated by very young, massive stars, with extremely high ionizing flux, accompanied by rapidly stochastic, variable star-formation rates. Other JWST observations have demonstrated that early galaxies host ``hidden'' active galactic nuclei (AGN), obscured by gas and dust, which implies we are seeing a rapid phase of supermassive blackhole growth in early galaxies. Understanding the relation between the star-formation and blackhole growth in these galaxies will be a challenge for future JWST observations, and I will discuss some ways to disentangle these effects. Lastly, I will use these discoveries to speculate about what we may learn in the coming years with JWST.
Friday 29 September 2023
No colloquium, Alternative day for National Day for Truth and Reconciliation
BGO & Chroma+, A "Made at Saint Mary's" stellar lab
Dr. Ian Short (SMU)
Date: Friday 6 October 2023
Time: 3:00 - 4:00 PM (ADT)
Location: Atrium 101
I will describe the low resolution spectrograph currently mounted at the Burke-Gaffney Observatory (BGO), the observing and data reduction procedure, and will present a selection of resulting stellar spectra. I will then describe the Chroma+ stellar spectrum synthesis code and its latest improvements, and will compare observed BGO and synthetic Chroma+ spectra. The BGO spectrograph and the Chroma+ modelling code are suitable for projects at the Honours level and for advanced class projects, and are both entirely supported by local staff and faculty expertise.
Much of the content of this talk can be found in these recent papers:
- “The Burke-Gaffney Observatory, a fully roboticized remote access observatory with a low resolution spectrograph", Short, C, Ian, Lane, David.J., & Fields, Tiffany, 2023, arXiv:2307.07022 [astro-ph.IM]
- “Chroma+GAS: An Expedited Solution for the Chemical Equilibrium for Cool Stellar Atmospheres", Short, C. Ian & Bennett, Philp.D., 2021, PASP, 133, 064501, arXiv:2206.01236 [astro-ph.SR]
- “The ChromaStar+ modelling suite and the VALD line list”, 2023, Short, C. Ian, 10.48550/arXiv.2307.01279
Indigenous Knowledges and Western Astronomy: Indigenizing the Drake Equation
Dr. Hilding Neilson
Date: Friday 13 October 2023
Time: 3:00 - 4:00 PM (ADT)
Location: Atrium 101
The Drake Equation is a thought experiment whose purpose is to understand the ingredients necessary for life and advanced technological civilizations to exist on other worlds in our galaxy. However, beyond reflecting on life on Earth we have no knowledge of many of these ingredients, such as the number of planets that have life, the number of with intelligent life, the number with advanced civilizations, and the lifetimes of these civilizations. In this talk I will review the Drake Equation and the biases that scientists have traditionally had in discussing this equation and how it has led to the current searches of biological and technological signatures. I will discuss how the Drake Equation looks different if we consider it through the lens of Indigenous methods and sciences and how these methods would lead to a dramatically different view of life in our Galaxy.
Using indirect methods to map the central engine in NGC 6814
Dr. Adam Gonzalez (SMU)
Date: Friday 20 October 2023
Time: 3:00 - 4:00 PM (ADT)
Location: Atrium 101
Powered by the accretion of matter onto a central supermassive black hole (SMBH), the compactness of the so-called central engine in AGNs makes direct imaging of these systems impossible for all but a handful of targets. Indirect methodologies examining the flux variability and spectral energy distribution of AGNs in the X-ray band have allowed us to probe the region just outside of the SMBH event horizon, revealing the physical processes at work in this extreme environment. In this talk, I will highlight recent works by our group focused on the nearby AGN NGC 6814 in which we have measured the size of its X-ray emitting region using an exquisite Xray eclipsing event as well as uncovered evidence of a possible non-standard accretion scenario using a 75-day multi-wavelength monitoring campaign.
Stemless plastic scintillation detectors: a novel detector with a bright future
Dr. Alasdair Syme (Dalhousie)
Date: 27 October 2023
Time: 3:00 - 4:00 PM (ADT)
Location: Atrium 101
Ionizing radiation plays a vital role in many areas of society, including the diagnosis and treatment of disease. In order to be used safely, accurate, quantitative measurements of radiation fields are an essential prerequisite. Many tools are available for this task, but all have some limitations. In this talk, I will discuss our efforts to develop radiation detectors based on organic electronic devices and plastic scintillators that overcome most of these shortcomings.
Machine Learning applications in Nuclear and Particle Physics
Dr. Michelle Kuchera (Davidson College)
Date: Friday 3 November 2023
Time: 3:00 - 4:00 PM (ADT)
Location: Atrium 101
Machine learning has become ubiquitous in data-rich applications. Fundamental physics research provides an exciting realm for machine learning research with applications ranging from experimental data acquisition through making theoretical predictions. This talk will introduce machine learning theory, highlighting applications from my group in nuclear and particle physics research. Specifically, I will focus on experimental applications for detector systems at the Facility for Rare Isotope Beams and CERN. I will highlight innovative approaches in machine learning that show promise in these physics applications and discuss how our research can assist in machine learning research.
Friday 10 November 2023
No colloquium, Fall break
Milky Way's Stellar Streams as Cosmological Probes
Dr. Ting Li (University of Toronto)
Date: 17 November 2023
Time: 3:00 - 4:00 PM (AST)
Location: Atrium 101
Stellar streams are one of the most powerful tracers to determine the mass and profile of the Milky Way as well as constrain the properties of dark matter. In this talk, I will discuss two ongoing spectroscopic programs to study the stellar streams in our Milky Way and highlight a few latest scientific results from these two programs. The Southern Stellar Stream Spectroscopic Survey (S5), started in 2018, is the first systematic program pursuing a complete census of known streams in the Southern Hemisphere using the fiber-fed AAOmega spectrograph on the Anglo-Australian Telescope. The Milky Way Survey of the Dark Energy Spectroscopic Instrument (DESI), on the other hand, is a recently started 5-yr spectroscopic program in the Northern Hemisphere. We are entering an extremely data-rich era in the next decade, with full 6D+chemistry information on dozens of stellar streams, to shape our understanding on the chemo-dynamical evolution of the Milky Way, as well as the nature of the dark matter.
A portable ambient light-compatible spectroscopic probe for disease detection
Dr. Kevin Hewitt (Dalhousie)
Date: Friday 24 November 2023
Time: 3:00 - 4:00 PM (AST)
Location: Atrium 101
The Hewitt Bionanophotonics lab at Dalhousie explores the use of inelastic light scattering - enhanced using nanoscale surfaces in some instances - for disease detection. In this talk I will describe a patent (pending) portable ambient light-compatible spectroscopic probe to non-invasively assess global and macrovesicular steatosis in human liver specimens. Two-stage biochemical and histopathological validations highlight the potential of the examined system as a trustworthy, non-invasive modality for steatosis evaluation. Notably, the ambient light-compatible approach is a notable progression beyond prior spectroscopic methods, effectively addressing associated limitations. The correlation between fat content results derived from the investigated Raman system and traditional triglyceride quantifications reinforces the reliability of this methodology. Moreover, introducing a dual-variable prediction for identifying significant (≥10%) discrepancies in global HS and MaS demonstrates the advanced precision and subtlety the system can deliver.
Beyond immediate outcomes, this study lays the foundation for the broader application of ambient light-compatible spectroscopic probes in clinical environments, potentially revolutionizing intraoperative liver assessments. Amidst the escalating demand for liver transplantation, tools of this nature hold substantial promise in ensuring optimal graft quality, consequently benefiting liver recipients. While the results are encouraging, further research is imperative to affirm the comprehensive potential and applicability of this system, especially in real-world operating room contexts.
The art of measuring galaxy physical properties
Dr. Camilla Pacifici (Space Telescope Science Institute)
Date: Friday 1 December 2023
Time: 3:00 - 4:00 PM (AST)
Location: Atrium 101
One of the most common approaches to measure stellar masses and other physical parameters for galaxies is spectral energy distribution (SED) fitting. This consists of comparing the light from galaxies with templates for which we know the physical parameters and extract the best template match or probability distribution functions of the parameters associated with such templates. Many years ago, when we were looking predominately at local galaxies and the observations consisted of a few photometric bands, SED fitting was considered a relatively simple job. In recent years, ground-based and space telescopes have given us a whole new set of information, with both photometry and spectroscopy for a large number of galaxies at all redshifts. Such quantity and quality of data require more and more advanced tools to make the most of the observations. Here is when SED fitting becomes a complicated job or an Art! I will present the various ingredients and complexities that go into state-of-the-art SED fitting tools, what parameters we can now measure, and how we can assess the uncertainties in the modeling approach.
Careers after a degree in astro/physics:
a panel discussion with SMU Astronomy & Physics alumni
Adam Chaffey & Shruti Tripathi
Date: Friday 19 January 2024
Time: 3:00-4:00 pm
Location: In-person, AT101
Adam is a licensed Professional Physicist (P.Phys). He holds an Honours B.Sc. in Astrophysics from Saint Mary’s University, an M.Sc. in Physics from Dalhousie University, and has been awarded two patents for LED optical systems design. He is currently Director, Smart Lighting Products at Liveable Cities. Adam has been involved in the development of industry-leading technology for street and roadway lighting applications since 2008. He actively participates on the ANSI C136 Committee on Roadway and Area Lighting Equipment, and other technical committees. He is also involved in the IES Street and Area Lighting Conference (SALC), the premier outdoor lighting conference in North America, where he is currently serving as SALC Committee Vice-Chair. In 2019, Adam served as Conference Chair for the SALC in San Diego, which hosted over 1000 outdoor lighting professionals. He has hosted and delivered seminars on outdoor lighting and lighting controls technology to audiences in North America, the Caribbean, Asia, Australia, New Zealand, the United Kingdom, and Europe.
Shruti, who started her journey as an astrophysics researcher, is now working as a Data Engineer (AI/ML) with a multinational company, Kellton. She holds a Masters in Physics, and a PhD in Astrophysics, which she obtained in India before coming to Canada in 2015. She worked as a part-time Research Associate working for Binary stars simulation at Bishop's University, in Sherbrooke, Quebec. She moved to Halifax in 2017 and then joined Prof. Luigi Gallo’s research group at SMU as a full-time postdoc. She also worked in the department as a part-time faculty, teaching physics, astronomy, and environmental sciences, and concluded a short-term teaching faculty position in 2021. Throughout her career, she participated in several conferences and symposiums and was awarded prestigious fellowships. In her current work, she uses AI tools and programming to build advanced automation solutions and products to help streamline repetitive tasks and make lives simpler. She was crowned first prize in the companywide AI hackathon. Outside of work, she plays musical instruments such as the harmonium and keyboards, and she loves long drives with family and friends!
Too Big to Be?: Searching for the Most Massive Galaxies in the Distant Universe
Dr. Jacqueline Antwi-Danso (University of Toronto)
Date: Friday 26 January 2024
Time: 3:00-4:00 pm
Location: In-person, AT101
One of the unsolved problems in extragalactic astronomy is understanding the physics of how galaxies grow their stellar mass over cosmic time. Large-scale hydrodynamical simulations have been largely successful in matching the basic properties and number densities of galaxies at z < 2.5 (covering the past 11 Gyr). This has given us confidence in our understanding of the physics that regulates star formation and quenching over most of cosmic history. However, at earlier cosmic times, simulations underestimate the number densities of massive galaxies by a shocking 1-2 orders of magnitude. While this issue has largely been overlooked for the past decade, recent JWST discoveries of massive galaxies observed at even earlier times than we thought possible have brought this tension with theory back to the limelight. In this talk, I will give an overview of the systematics contributing to this discrepancy between theory and observations, as well as our best attempts at addressing it using (1) medium-band galaxy surveys; (2) novel color-color selection methods; and (3) physically motivated star-formation histories. I will also discuss my upcoming JWST Cycle 2 program and a few others geared at obtaining precise redshifts, stellar masses, and chemical abundances of massive quiescent galaxies at z > 3.
Date: Friday 2 February 2024
ICA Symposium
Accreting Massive Black Holes at the Center of Galaxies and their Impact on Small and Large ScalesDr. Labani Mallick (University of Manitoba)
Date: Friday 9 February 2024
Time: 3:00-4:00 pm
Location: In-person, AT101
Astrophysical black holes are surprisingly simple physical objects. Their gravitational field can be fully described by two parameters: mass and spin. We cannot directly observe black holes as no light escapes from the event horizon. However, we can detect the light from accreting gas, which forms a dense disk around the black hole, known as an accretion disk. The accretion of material by a massive black hole at the center of its host galaxy forms an active galactic nucleus (AGN), the innermost region of which emits X-ray radiation. An AGN is energetically efficient for regulating the growth of galaxies and is crucial for the development of the Universe we see today. One of the most important tools to probe the innermost accretion flow is the detection of X-ray reverberation echoes, where the X-ray photons reflected from the accretion disk are delayed relative to the primary X-ray source. In this talk, I will first discuss how detailed measurements of the reflected X-rays from the accretion disk can be used to probe the innermost regions of accretion flow just outside the event horizon and determine the fundamental properties of the black hole, such as its spin, across the complete mass scales from around ~105-1010 solar masses. Peering into the growth channels of black holes, I will discuss how we can distinguish accretion vs. merger-dominated black hole growth and probe the cosmological evolution of black hole spins in the last 10 billion years of cosmic history. Finally, I will show how enigmatic relativistic winds or Ultra-Fast Outflows (UFOs) launched from the AGN accretion disk can be used to probe the feedback mechanism connecting the central black holes with their host galaxies.
Galactic Archaeology with Globular ClustersDr. Stephanie Monty (University of Cambridge)
Date: Friday 16 February 2024
Time: 11:00 am-12:00 pm
Location: Remote (via Zoom), streamed in Sobey 255
Globular clusters (GCs) are among the most ancient objects in the local Universe, acting as tracers of galaxy formation across both space and time. With the recent JWST discovery of nitrogen-rich star formation in a redshift 11 galaxy, and the discovery that over 50% of the in-situ stars in the Milky Way (MW) likely formed in clusters, understanding the role of GCs in the context of galaxy evolution is becoming ever more important. The MW hosts a large (~150) and diverse population of GCs. Among these clusters, a fraction are thought to have formed in-situ, alongside the MW, while others were likely accreted alongside disrupted dwarf galaxies. Finding a chemical tag linking accreted GCs to their host galaxies is key to further unscrambling the MW halo. I will present results showing that the ratio of [Eu/Si] separates dwarf galaxy and MW stars at the same metallicities and that this difference extends to the populations of accreted and in-situ GCs. While this difference has been seen before at high-metallicities, I will show that it extends to metallicities of [Fe/H] < -2 and that the difference cannot be explained by star formation efficiency alone. I will also show that this unique signature not only extends to Local Group dwarf galaxies and their globular clusters, but also to the halo of M31 - offering the opportunity to do Galactic Archaeology beyond the MW.
February 23: Winter break - no colloquium
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