Event Calendar

Location: MP 15th Floor Conf Room

Title: Fast Radio Bursts and Cosmic Dark Matter

Abstract: Some fast radio bursts appear to involve an extraordinary release of energy, $10^{39}$-$10^{40}$ erg in the 1-10 GHz band, within a brief interval of milliseconds or less. Nothing close to this has been clearly detected from a neutron star, and existing models of coherent radio emission from radio pulsars or relativistic shocks fail by orders of magnitude to match such intensities. I will describe an alternative approach to fast radio bursts which connects them with a new form of cosmic dark matter. The emission rate of FRBs is connected to the internal properties of macroscopic magnetic dipoles through their collision rate, implying a mm-cm size and formation at a grand unified energy scale. A small-scale release of energy (inside a radio wavelength) leads robustly to radio emission through at least three electrodynamic channels, none of which depends on ad hoc assumptions about particle clumping. This emission is predicted to peak above 10-100 GHz, and naturally accomadates rapid repetitions on millisecond timescales. FRB sources which repeat over longer timescales are associated with supermassive black holes that grow adiabatically in galactic nuclei and accrete a small amount of this mildly dissipative dark matter; these sources are predicted to show extreme Faraday rotation and burst more frequently at higher frequencies. A point flash near a rotating black hole is strongly lensed, showing interesting ringing effects and longer delays by reflection off cool hydrogen clouds. One-time FRB emission is, by contrast, more widely spread within galaxies. EM pulses strong enough to produce FRBs also accelerate ions up to energies $10^{19}$-$10^{20}$ eV; and nearby white dwarf stars experience collisions with the hypothesized dark matter particles at an interesting rate.

Location: MP1318A

Weekly paper discussion focussing on pulsars, compact objects, and propagation effects. For a list of upcoming discussions, see: https://docs.google.com/spreadsheets/d/16TXacDDCk5FxMyw_842h5JHuq0h0RNhlWvp4li64edM/edit?usp=sharing If you would like to sign up for the presenter rota, email: simard@astro.utoronto.ca Location: CITA lounge

The schedule of speakers: https://tinyurl.com/cosmo-rota  
Location: 15th floor conference room

Location: MP1318A

The schedule of speakers: https://tinyurl.com/cita-blackboard Location: MP 1318A

Location: MP 15th Floor Conf Room

Title: Numerical Simulations of Black Hole Accretion

Abstract: Accreting black holes are observed in a large variety of systems in astronomy: active galactic nuclei, X-ray binaries, tidal disruption events, gamma-ray bursts. While analytical one-dimensional models have been enormously useful for understanding several aspects of accretion physics, some aspects such as the formation of jets and winds are beyond the scope of these models. Numerical general relativistic MHD simulations have filled the gap, and are being used to explore the multidimensional gas dynamics and radiative properties of accretion flows. The talk will review some recent progress in this field.

Host: Almog Yalinewich

Location: MP1318A

Weekly paper discussion focussing on pulsars, compact objects, and propagation effects. For a list of upcoming discussions, see: https://docs.google.com/spreadsheets/d/16TXacDDCk5FxMyw_842h5JHuq0h0RNhlWvp4li64edM/edit?usp=sharing If you would like to sign up for the presenter rota, email: simard@astro.utoronto.ca Location: CITA lounge

Open discussion of stars- and planets-related topics or more specialized discussion of dynamics-related papers on alternating weeks. See here for details. Location: MP 1318A

The schedule of speakers: https://tinyurl.com/cosmo-rota  
Location: 15th floor conference room

Title: Cold Gas at High Redshifts

Abstract: The nature of damped Lyman-alpha absorbers (DLAs), a population of high-redshift absorption-selected galaxies, has been an open question in the field of galaxy evolution for more than three decades. The critical problem in the field has been simply identifying the DLA host galaxies, due to the presence of the bright nearby QSO. This talk will describe new results from Atacama Large Millimeter/sub-millimeter Array (ALMA) studies of the host galaxies of DLAs over a wide range of redshifts, z~0.5-4.5, in carbon monoxide (CO) and ionized carbon (CII-158 micron) emission lines. These are the first CO and CII-158 micron detections in DLA host galaxies, providing a new window on physical conditions in high-z absorption-selected galaxies, and yielding a new tool to identify and study DLA host galaxies at high redshifts.

Host: Viswesh Marthi

Location: MP 1318A

Location: MP1318A

The schedule of speakers: https://tinyurl.com/cita-blackboard Location: MP 1318A