Events List for the Academic Year
Event Time:
Thursday, July 29, 2021 | 4:00 pm - 5:00 pm
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2021-07-29T16:00:00
2021-07-29T17:00:00
Heatwave: A Synoptic Breakdown Of The Extraordinary Heatwave On The Pacific Coast Of The US And Canada in June 2021
Event Information:
In late June 2021, the Pacific Northwest experienced extraordinarily high temperatures. British Columbia alone recorded over 60 record high temperatures, with the town of Lytton setting an all-time high temperature in Canada for three consecutive days, peaking at 49.6 C (121.3 F). During this talk, we will explore the meteorological conditions that led to these extreme temperatures—analyzing the upper air dynamics, mid-level thermal anomalies, and terrain effects during the event. We will also delve into the societal and environmental impacts regionally.
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Event Time:
Wednesday, July 28, 2021 | 10:00 am - 11:00 am
Event Location:
Online
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2021-07-28T10:00:00
2021-07-28T11:00:00
Chemodynamical evolution of galaxies
Event Information:
Metallicities and elemental abundances are key to testing our current understanding of galaxy formation and evolution. At the beginning of the universe only light elements such as hydrogen and helium were produced. Carbon and heavier elements were instead created inside stars and distributed into the interstellar medium by stellar winds and supernova explosions. From the spatial distribution of elements in stars and gas, it is therefore possible to constrain the star formation and chemical enrichment histories of galaxies. This approach, Galactic Archaeology, has been popularly used for our Milky Way Galaxy. It can also be applied to external galaxies thanks to recent and future observations with integral field spectrographs. A decade ago it became possible to simulate chemical and dynamical evolution of galaxies following the development of high performance computers and improved computational techniques. I will show some recent simulation predictions of mass-metallicity relations and of metallicity radial gradients, and I will discuss future prospects in the era of the James Webb Space Telescope.
2021 BC Galaxy Summer Seminars" is an online seminar series organized jointly by SFU, UBC and UVic. For the full series schedule, visit the series webpage. Subscribe to our e-mail list here to get reminders about these seminars.
Event Location:
Online
Event Time:
Monday, July 26, 2021 | 3:00 pm - 4:00 pm
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2021-07-26T15:00:00
2021-07-26T16:00:00
The Dynamics of Compact, Multi-planet Systems
Event Information:
The Kepler telescope detected thousands of exoplanets in hundreds of multi-planet systems and revolutionised planetary sciences. Many of these systems are quite compact and are typically a few billions of years old. Consequently, we are seeing only a snapshot of system architectures after hundreds of billions or even trillions of orbits. A substantial portion of their evolution has been governed by dynamical interactions, however. This can allow us to probe their histories and constrain the role of the natal environment. In this talk, I will provide an overview of our present knowledge of these planetary systems and share my work to unravel some of the complexities of their dynamics - a problem as old as astronomy itself.
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Event Time:
Thursday, July 22, 2021 | 4:00 pm - 5:00 pm
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2021-07-22T16:00:00
2021-07-22T17:00:00
Quantum Gravity in the Lab
Event Information:
It has long been assumed that gravity and quantum mechanics can only be confronted at very high energies ~ 1.2 x 10^28 eV (enough to boil 5 tons of water, and 15 orders of magnitude above the range of particle accelerators). However, recent theory indicates that gravity may cause a breakdown of quantum mechanics at much lower energies, for large masses. This has led to a new experimental field in which such a breakdown is sought in earth-based labs.
I will review the theory which has made such predictions, and their history, which begins with speculations by Feynman in 1957. I will focus on the Correlated Worldline (CWL) theory, which is the only one so far to make definite quantitative predictions. I will then discuss some of the optomechanical experiments that are trying to test the theory, and where they are right now. These experiments are pushing the boundaries of our understanding of quantum mechanics at the macroscopic scale; as such they have implications for everything from quantum computation to future gravitational wave detectors.
Event Location:
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Event Time:
Wednesday, July 21, 2021 | 3:00 pm - 4:00 pm
Event Location:
Online
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2021-07-21T15:00:00
2021-07-21T16:00:00
Quenching massive galaxies
Event Information:
How and why galaxies grow in stellar mass and cease their star formation are key open questions of galaxy formation and evolution. I present evidence for a diversity of pathways for building up the quiescent galaxy population at early cosmic times. Specifically, I will present observational constraints on star-formation histories and quenching timescales by combining Keck DEIMOS spectroscopic data with >10-band photometry. I will discuss how one can self-consistently fit both photometric and spectroscopic data together with the tool Prospector, which allows fitting for non-parametric star-formation histories and complex stellar, nebular, and dust physics. Despite the apparent diversity, we find that the most massive, compact galaxies have formed their stars the earliest and most rapidly. Furthermore, from the star-formation history constraints, I will discuss how galaxies evolve about scaling relations (such as the star-forming main sequence) with cosmic time. Finally, I will relate these findings to numerical simulations (in particular IllustrisTNG), showing that the large diversity of quenching epochs and timescales challenge numerical models and point toward a combination of internal and external quenching mechanisms.
"2021 BC Galaxy Summer Seminars" is an online seminar series organized jointly by SFU, UBC and UVic. For the full series schedule, visit the series webpage. Subscribe to our e-mail list here to get reminders about these seminars.
Event Location:
Online
Event Time:
Monday, July 19, 2021 | 3:00 pm - 4:00 pm
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2021-07-19T15:00:00
2021-07-19T16:00:00
Small But Mighty: The Tiniest White Dwarf and Other Stories
Event Information:
The advent of Gaia and of large photometric and spectroscopic surveys is changing the landscape of white dwarf studies. These incredible new data sets, together with improved models, have enabled tackling some unsolved mysteries concerning white dwarfs as a population, as well as discovering extremely peculiar objects that challenge our understanding of white dwarf formation and evolution. In my talk, I will show how the precise astrometry from Gaia has dramatically improved our capability of studying white dwarfs in young star clusters, and therefore probe the evolution of white dwarfs born from single progenitor stars. On the other hand, the Zwicky Transient Facility (ZTF) is shedding light on the evolution of white dwarfs in binary systems, substantially increasing the number of known eclipsing white dwarf binaries and finding the final products of such binaries. In fact, ZTF is discovering a large number of massive, rapidly rotating and highly magnetized white dwarfs whose extreme properties characterize them with high confidence as remnants of white-dwarf mergers. Finding a population of white dwarf merger remnants just below the Chandrasekhar mass can help constrain the number of mergers in the Galaxy and their contribution to the type Ia supernova rate, as well as help us understand the origin of strong magnetic fields in white dwarfs. I will present some early results of the search, including the discovery of ZTF J1901+1458, a moon-sized white dwarf that is extreme in almost every respect.
Event Location:
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Event Time:
Thursday, July 15, 2021 | 4:00 pm - 5:00 pm
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2021-07-15T16:00:00
2021-07-15T17:00:00
Increasing Accuracy in the Hubble Constant: Consistency with LCDM
Event Information:
An important and unresolved question in cosmology today is whether there is new physics that is missing from our current standard Lambda Cold Dark Matter (LCDM) model. Recent measurements of the Hubble constant, Ho - based on Cepheids and Type Ia supernovae (SNe) - are discrepant at the 4-5-sigma level with values of Ho inferred from measurements of fluctuations in the cosmic microwave background (CMB). The latter assumes LCDM, and the former assumes that systematics have been fully accounted for. If real, the current discrepancy could be signaling a new physical property of the universe. I will present new results based on an independent calibration of SNe Ho based on measurements of the Tip of the Red Giant Branch (TRGB). The TRGB marks the luminosity at which the core helium flash in low-mass stars occurs, and provides an excellent standard candle. Moreover, the TRGB method is less susceptible to extinction by dust, to metallicity effects, and to crowding/blending effects than Cepheid variable stars. I will address the current uncertainties in both the TRGB and Cepheid distance scales, as well as discuss the current tension in Ho and whether there is need for additional physics beyond the standard LCDM model.
Event Location:
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Event Time:
Thursday, July 15, 2021 | 1:00 pm - 3:00 pm
Event Location:
via ZOOM
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2021-07-15T13:00:00
2021-07-15T15:00:00
Departmental Doctoral Oral Examination (Thesis Title: “The effects of calibration errors and foreground filters on the CHIME power spectrum measurement. A study with simulations and real data.”)
Event Information:
Abstract:
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a drift-scan radio telescope designed to map large scale structure in the universe using the redshifted 21 cm line emitted by neutral hydrogen. By observing the 400 to 800 MHz frequency band, CHIME will measure the expansion rate of the universe in the redshift range z = 0.8 - 2.5 to constrain the nature of dark energy.
In this frequency range, astrophysical foregrounds from the Galaxy and extragalactic point sources are much brighter than the 21 cm emission. This requires aggressive foreground filtering. We therefore developed a new implementation of the Karhunen-Loeve (KL) transform that correctly tracks the signal and noise power in our data to enable us to filter bright foregrounds. As part of the development of the KL transform, we significantly improved the point source component of the foreground model.
The data volumes for CHIME are extremely large, therefore we developed an upgraded parallelized power spectrum estimation pipeline which is able to forecast the Fisher information matrix and estimate power spectra for a telescope almost as large as CHIME.
Due to the bright astrophysical foregrounds CHIME has very stringent calibration requirements. We wrote an end-to-end simulation pipeline and studied various realistic sources of calibration uncertainties with it. The calibration requirements are very stringent and we found that CHIME currently doesn't quite meet the requirements when using the Karhunen-Loeve (KL) foreground filter. We must therefore continue to develop innovative foreground filters that are more robust against systematics and we must explore further whether our requirements are too conservative or if a larger telescope will allow us to relax these requirements.
We then investigated different processing choices on power spectrum estimation with CHIME data in the frequency band 610 to 680 MHz with a selection of short baselines to ensure quick computation times. We found the even with our currently best calibration procedures our power spectrum estimates are several orders of magnitude higher than expectation. Using a delay filter as an intermediate processing step seemed to reduce the bias but we leave further development of a hybrid filter to future work.
Event Location:
via ZOOM
Event Time:
Wednesday, July 14, 2021 | 10:00 am - 11:00 am
Event Location:
Online
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2021-07-14T10:00:00
2021-07-14T11:00:00
Dwarf Galaxies and Their Black Holes
Event Information:
Because they are dark-matter dominated, dwarf galaxies provide some of the most stringent tests of our cold dark matter model. Specifically, Lambda CDM makes predictions about the number, shape, and spatial distributions of the faint friends of massive galaxies. I will present results from the Exploration of Local VolumE Satellites (ELVES) survey, that constructs the largest sample of satellites around Milky Way-like hosts. Our ability to utilize dwarfs as tests of CDM is limited by our understanding of baryonic process; I will also discuss our efforts to us the Hyper Suprime Camera Survey to understand the role of feedback and merging in dwarf evolution. If time permits, I discuss what we know about black holes in dwarf galaxies, and how their demographics sheds light on the formation of the seeds of supermassive black holes.
"2021 BC Galaxy Summer Seminars" is an online seminar series organized jointly by SFU, UBC and UVic. For the full series schedule, visit the series webpage. Subscribe to our e-mail list here to get reminders about these seminars.
Event Location:
Online
Event Time:
Wednesday, July 14, 2021 | 9:00 am - 11:00 am
Event Location:
via ZOOM
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2021-07-14T09:00:00
2021-07-14T11:00:00
Departmental Doctoral Oral Examination (Thesis Title: “Learning Physics with Interactive Simulations: Inductive Inquiry Learning Activities for an Introductory Electromagnetism Course”)
Event Information:
Abstract:
In this work, the use of interactive simulations in the context of an inductive learning pedagogical approach in the tutorials of a large enrollment introductory electromagnetism course is investigated. Interactive simulations are educational tools that allow students to uncover the rules that govern a simulated physics phenomenon through a process of scientific inquiry. These simulations can be designed with affordances and constraints that implicitly scaffold inquiry such that students can more efficiently uncover important features of the simulated phenomenon. As such, interactive simulations are a promising tool to use in the context of invention activities, where students invent a rule for a target physics domain before receiving any formal instruction on it.
We report the results of a study comparing the educational benefits of invention activities where students invent a rule either by generating their own cases from a simulation or from a set of contrasting cases designed to directly highlight important domain features when compared to one another. The simulation-based invention activities provide students with an opportunity to practice and develop valuable exploration skills but the greater agency in their exploration can also makes it harder to successfully explore all important domain features. This thesis details the design of a series of three collaborative and scaffolded practice invention activities that aim to mitigate this issue. Results show that generating cases from a simulation in these activities is less likely to lead students to invent the correct rule and generally leads to poorer immediate conceptual learning outcomes as compared to using instructor designed contrasting cases. Results also demonstrate that a student's ability to explore and identify all important features of the target rule is largely determined by how well the instructional material provided affords the investigation of those features. Finally, the above student outcomes are also compared across two final assessment invention activities where students worked individually without scaffolding; in the first students invent by generating their own cases from a simulation, while in the other they use instructor-design contrasting cases. We show that students that had previously practiced inventing with contrasting cases performed the same or better on all outcomes compared to those that practiced inventing by generating cases from a simulation.
Event Location:
via ZOOM
Event Time:
Monday, July 12, 2021 | 3:00 pm - 4:00 pm
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2021-07-12T15:00:00
2021-07-12T16:00:00
Galaxies, AGN and their environments
Event Information:
A key open question in extragalactic astronomy is understanding the processes driving the build-up and quenching of massive galaxies — specifically the role of AGN and environment therein. As an overview of my recent research activities, I will present several projects that all help inform the above question. I will address some of the issues with going from observed properties to physical properties and a possible pathway to scaling this up to the sample sizes in the billions that are on our horizon now. In this context, I will touch upon the issue of fully accounting for dust obscured star-formation and AGN activity. Lastly, I will discuss how we assess a galaxy's environment with photometric data as well as prospects for doing so much better with the upcoming PFS galaxy evolution spectroscopic survey.
Event Location:
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Event Time:
Friday, July 9, 2021 | 10:00 am - 12:00 pm
Event Location:
Virtual
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2021-07-09T10:00:00
2021-07-09T12:00:00
Impostor Syndrome Workshop
Event Information:
The Equity & Inclusion in PHAS team presents “Impostor Syndrome,” a workshop run by astrophysicist Dr. Renée Hložek.
Navigating the academic environment can be stressful. Power dynamics can impact our ability to communicate clearly with each other, and can generate feelings of impostor syndrome. In this interactive workshop, we will use techniques of improvisation and changing power dynamics to explore ways we can shape our communication environment.
The session will include a short presentation, followed by a group discussion and an interactive component with improvisation exercises. It is open to people of all academic stages who are keen to think about these topics in new ways, and to try new techniques to help make our work environment a more comfortable space.
Date: Friday, July 9th, 10:00am – 12:00pm PDT via Zoom
Please register by Wednesday, July 7th. This workshop is free!
Register: https://ubc.zoom.us/meeting/register/u5ctd-yoqzguGNMUiGhsN7Z-iNFp_rm4NpBu
Event Location:
Virtual
Event Time:
Thursday, July 8, 2021 | 4:00 pm - 5:00 pm
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2021-07-08T16:00:00
2021-07-08T17:00:00
Fractional derivatives and applications in MRI
Event Information:
Diffusion-weighted Magnetic Resonance Imaging (MRI) Depicts Regions of Sub- and Super-diffusion Encoded by the Fractional Diffusion Equation
Fractional-order time and space derivatives extend the classical diffusion equation in a manner that accounts for the non-Gaussian diffusion often observed in heterogeneous materials. MRI provides diffusion-weighted images of biological tissues, which exhibit anisotropic, hindered, and restricted diffusion. Fractional calculus models of anomalous diffusion display regions of sub- and super-diffusion separated by a line of quasi-diffusion along which the mean squared displacement is a linear function of diffusion time. This behavior can be captured by fractional derivatives and/or by introducing a diffusion coefficient with a power-law decay varying as a function of time or space. The corresponding phase diagrams, like pages in a book, result in a portfolio of representations of anomalous diffusion. The anomalous phase cube employs lines of super-diffusion (Lévy process) and sub-diffusion (subordinated Brownian motion) to stitch together the different diffusion models for corresponding regions.
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Event Time:
Wednesday, July 7, 2021 | 11:00 am - 12:00 pm
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2021-07-07T11:00:00
2021-07-07T12:00:00
Quantization of Gravity in the Black Hole Background
Event Information:
We perform covariant quantization of Einstein gravity in spherical harmonic basis in the background of a Schwarzschild black hole. We use Regge-Wheeler gauge for modes with l>=2, and propose the gauge for l<2 modes. We find that Faddeev-Popov ghosts are absent for l>=2 and for l<2 they have instantaneous propagators in Schwarzschild coordinates, like in Coulomb gauge in QCD.
We further perform a canonical quantization of gravity in this gauge and establish that the Hamiltonian at the quadratic level is unitary and ghost-free. The canonical degrees of freedom are associated with Zerilli-Moncrief and Cunningham-Price-Moncrief functions. The l<2 part of the Hamiltonian vanishes. This quantization with the unitary Hamiltonian for gravity is valid also in Minkowski space in spherical coordinates.
Event Location:
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Event Time:
Wednesday, July 7, 2021 | 10:00 am - 11:00 am
Event Location:
Online
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2021-07-07T10:00:00
2021-07-07T11:00:00
Looking for observational signatures of feedback from active galactic nuclei
Event Information:
Feedback from active galactic nuclei (AGN) is thought to be key in shaping the life-cycle of host galaxies. AGN inject a significant amount of energy into the surrounding interstellar medium and launch gaseous winds. They are therefore able to potentially suppress or inhibit future star formation in their hosts. An ideal cosmic laboratory to study how AGN regulate galaxy growth is the so-called cosmic noon (z~2), i.e. the peak of AGN accretion activity when their energy output is overall maximized. In this talk I will describe our recent efforts to systematically characterize the impact of AGN on star formation in galaxies at cosmic noon. To this aim, we are exploiting integral field spectroscopy data obtained with SINFONI and ALMA observations of the ionized and molecular gas as well as dust continuum.
"2021 BC Galaxy Summer Seminars" is an online seminar series organized jointly by SFU, UBC and UVic. For the full series schedule, visit the series webpage. Subscribe to our e-mail list here to get reminders about these seminars.
Event Location:
Online
Event Time:
Monday, July 5, 2021 | 3:00 pm - 4:00 pm
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2021-07-05T15:00:00
2021-07-05T16:00:00
Multi-wavelength Explorations of Evolved Stars and Exoplanets
Event Information:
Multi-wavelength observations, from the ultraviolet (UV) to the infrared (IR) and beyond, are powerful tools for exploring evolved stars and characterizing exoplanets. Cool evolved stars contribute significantly to the interstellar medium (ISM) enrichment, via gas and dust produced in their atmospheres. Yet, a thorough understanding of their mass loss mechanism(s) remains challenging. Exploring cool evolved stars' upper layers is thus essential to unraveling their mass loss history and its influence on the composition of the ISM and Galactic ecology. But how can we 'see through' the biggest stars in the Universe?
In this talk, I will describe investigations tying together analyses of HST high-resolution UV spectra, and VLT optical/IR interferometric observations and imaging of evolved stars, which enabled tight constraints on their mass loss, atmospheric structure and dynamics, radial extension, and evolutionary stages. I will also present groundbreaking results from application of machine learning algorithms to TESS light curves data for detecting new exoplanets, and discuss new opportunities to extend science using next-generation ground-base and space telescopes such as the JWST. Finally, I will describe three mission concepts: SI-LP, FITE, CUµLUS, exciting visionary missions that will significantly advance our knowledge, from the UV into the IR, of evolved stars' interiors and circumstellar envelopes, and of exoplanets.
Event Location:
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Event Time:
Thursday, July 1, 2021 | 4:00 pm - 5:00 pm
Event Location:
None
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2021-07-01T16:00:00
2021-07-01T17:00:00
Canada Day!
Event Information:
It's Canada Day and we're not having a Departmental Colloquium!
Event Location:
None
Event Time:
Wednesday, June 30, 2021 | 11:00 am - 12:00 pm
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2021-06-30T11:00:00
2021-06-30T12:00:00
How do we design the future of gravitational wave astrophysics?
Event Information:
We are living in an astrophysics transformation because decades ago technologists started to design and build our future. They figured out that we could convert the dynamic motion of space-time into a detectable signal and developed technology to create the Advanced Gravitational-wave detector network. In the last five years, we swiftly moved from the first-ever direct detection into catalogs of 10s of new sources. These observations enable direct measurements of General Relativity's robustness, independent cosmological tracers, and how we understand the environments stars live and die. We are starting to see a glimmer of what is on our horizon. In this presentation, I will discuss how we are designing the future of gravitational wave astrophysics to ensure the field's longevity. I will share where we are within the generations of gravitational wave detector development, including the next ambitious project, Cosmic Explorer and how you can join the Cosmic Explorer community. I will describe how I am bringing the world of metamaterials into gravitational wave instrumentation and the potential for improving our detector’s sensitivity.
Event Location:
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Event Time:
Wednesday, June 30, 2021 | 10:00 am - 11:00 am
Event Location:
Online
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2021-06-30T10:00:00
2021-06-30T11:00:00
The evolution of cold accretion flows in the CGM of massive galaxies and proto-clusters at z>2
Event Information:
Massive star-forming galaxies and proto-clusters at high redshift, z>2, are thought to be fed by narrow streams of cold, ~10^4K, gas from cosmic web filaments. However, the interaction of these cold streams with the ambient hot CGM is poorly understood. In particular, the observational signatures of this interaction and of cold streams more broadly, the thermal and morphological state of the gas that eventually reaches the central galaxy, and its effect on galaxy evolution, are all open questions. I will present the latest results from a systematic study of this interaction, using a combination of analytic models, idealized high-resolution numerical simulations, and cosmological simulations. We study the effects of hydrodynamics, radiative cooling, self-gravity, the halo potential, and magnetic fields, separately and together, in order to gain insight into stream evolution in different limits. We find that while hydrodynamic instabilities can disrupt streams in the CGM, these are stabilized by cooling, gravity, and MHD. Radiative cooling in the turbulent mixing layer between the stream and the CGM is observable in Lyman alpha, and can explain several observed Lyman alpha blobs. Self-gravity in the streams can lead to star-formation in the CGM at redshifts z>~4. MHD effects lead to magnetically dominated interface regions which appear out of thermal pressure equilibrium and impact the phase structure of the high-z CGM.
"2021 BC Galaxy Summer Seminars" is an online seminar series organized jointly by SFU, UBC and UVic. For the full series schedule, visit the series webpage. Subscribe to our e-mail list here to get reminders about these seminars.
Event Location:
Online
Event Time:
Monday, June 28, 2021 | 3:00 pm - 4:00 pm
Event Location:
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2021-06-28T15:00:00
2021-06-28T16:00:00
The first CHIME/FRB catalogue and beyond
Event Information:
The Canadian Hydrogen Intensity-Mapping Experiment (CHIME) opens a whole new window on the Universe and this new catalogue of more than 500 fast radio bursts (FRBs) provides a treasure trove of data for understaning FRBs. For the first time, we can study a population of FRBs from a single telescope. We see that they come from all over the sky and across the Universe, from very nearby galaxies to more than halfway back to the Big Bang. We also see that there may be more than one type of FRB. We are able to obtain each burst's "fingerprint", and the repeating sources have different fingerprints from the FRBs that have only been seen once.
Event Location:
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