DRAO Seminar Series Spring 2020


Time & Date Speaker Title
14:00 Wed Jan 08 Paul Scholz
UToronto
Latest results from CHIME/FRB
14:00 Wed Jan 15 Matt Dobbs
McGill
Unlocking the Radio Sky – mapping transients and cosmic structure with CHIME and the path to CHORD
14:00 Wed Jan 29 Tyrone Woods
DAO
Supernova Archaeology: Uncovering the progenitors of Type Ia supernovae from clues in the ISM
14:00 Wed Feb 12 Simon Foreman
Perimeter/DRAO
Gravitational lensing of 21cm intensity maps
14:00 Wed Feb 26 Gregg Hallinan
Caltech
The Dynamic Radio Sky from the Owens Valley Radio Observatory
14:00 Wed Mar 4 Chikaedu Ogbodo
Macquarie University
Mapping the Galactic Magnetic Field with Hydroxyl Masers
14:00 Wed Mar 11 Jane Kaczmarek
DRAO
The Parkes Ultra Wide-bandwidth Low​ Receiver​
POSTPONED AMID COVID-19 Meiling Deng
Perimeter/DRAO
Antenna Array Design, Beam Calibration of the CHIME telescope and Mapping of the North Celestial Cap
CANCELLED/POSTPONED Katie Jameson
CSIRO
Neutral and Molecular Gas at Low Metallicity in the Small Magellanic Cloud with the ATCA, ALMA, and ASKAP
POSTPONED AMID COVID-19 Judith Irwin
Queen’s University
The CHANG-ES Project and new Results on Polarized Disks and Halos of Galaxies
14:00 Wed Apr 8 Kate Pattle
National University of Ireland Galway
Remote Talk: The JCMT BISTRO Survey: Variation of magnetic field and grain aligment properties within the Ophiuchus Molecular Cloud
14:00 Wed Apr 15 Cameron Van Eck
Dunlap Institute
Remote Talk: Galactic Faraday tomography at low frequencies
14:00 Wed Apr 22 Abedin Abedin
DAO
Remote Talk: Collision rates in the Edgeworth-Kuiper belt
14:00 Wed Apr 29 Kianoosh Tahani
KPU
Remote Talk: TBD

Latest results from CHIME/FRB

Paul Scholz (UofT)

CHIME/FRB is a search for fast radio bursts using the CHIME telescope at DRAO. As we enter into its second year of operation, several exciting results which help to elucidate the nature of FRBs have come out of CHIME/FRB. I will review the current status of the project and present the latest results, putting them in context in the FRB field.

Unlocking the Radio Sky – mapping transients and cosmic structure with CHIME and the path to CHORD

Matt Dobbs (McGill)

Technology advances have opened a new era of radio observations. We are now monitoring the sky at millisecond cadence and discovering a vast catalog of new fast radio transients while simultaneously making deep maps of structure in the universe using hydrogen intensity mapping as a tracer. While these fields are still in their infancy, early results are rolling out, fuelling discovery and motivating the design for new instruments. I will show recent advances with the CHIME telescope, and describe the path towards developing CHORD, a new generation highly redundant telescope to be sited at DRAO.

Supernova Archaeology: Uncovering the progenitors of Type Ia supernovae from clues in the ISM

Tyrone Woods (DAO)

Type Ia supernovae (SNe Ia) have proven vital to our understanding of cosmology, both as standard candles and for their role in the origin of the elements. They are now understood to arise from the thermonuclear explosion of a white dwarf, but why should a white dwarf explode? Evolutionary models can be grouped into either “accretion” or “merger” scenarios, with accretion models typically implying a hot, luminous phase prior to explosion. These objects are significant sources of ionizing radiation; therefore, the environment surrounding SN Ia progenitors should be strongly ionized, and traced by faint nebular emission. Such “relic” nebulae should extend out to 10 — 100 parsecs and linger for roughly the recombination timescale in the ISM (∼100,000 years). In this talk, I’ll show how the absence of a surrounding nebula excludes any accretion (“single-degenerate”) channel for the origin of Tycho’s supernova, as well as many other nearby remnants. Most variations on the merger (“double degenerate”) scenario remain viable. I’ll also show how a similar test can be applied to the integrated emission of old stellar populations, ruling out the textbook accretion scenario for delay times greater than 1 Gyr, before concluding with some recent results on the deeper connections between binary progenitors of some supernovae and the warm ionized interstellar medium.

Weak Lensing of 21cm Maps

Simon Foreman (Perimeter)

Gravitational lensing of the cosmic microwave background (CMB) has emerged as a powerful probe of cosmology, made possible by the development and characterization of nearly-optimal estimators for extracting lensing-induced distortions from temperature and polarization maps. One can ask whether similar tools can be applied to upcoming “intensity maps” of emission lines at various wavelengths (e.g. 21cm). Following an introduction to the essential concepts of CMB lensing, I will present recent work in this direction, focusing on the impact of nonlinear gravitational clustering on standard CMB lensing estimators when applied to intensity maps. I will show how these nonlinearities can provide a significant contaminant to lensing reconstruction, but will also describe how this contamination can largely be mitigated by modifying the lensing estimator. Finally, I will present estimates for the detectability of lensing in ongoing and proposed intensity mapping surveys, and highlight related work on reconstructing large-angle information in optical galaxy surveys using the same techniques.

The Dynamic Radio Sky from the Owens Valley Radio Observatory

Gregg Hallinan (Caltech)

I will discuss a new generation of radio arrays designed to rapidly survey the radio sky from the Owens Valley Radio Observatory (OVRO) in California. The 352-dipole Long Wavelength Array (OVRO-LWA) images the entire sky every 10 seconds to simultaneously monitor 4000 nearby stellar systems in the search for transient radio emission from exoplanets. It will also search for prompt counterparts to LIGO events and detect 1000s of air showers from high energy cosmic-rays. Simultaneously, at GHz frequencies, the 110-dish Deep Synoptic Array (DSA) will detect and localize >100 fast radio bursts (FRBs) to their host galaxies each year. I will also introduce the DSA-2000 concept, a planned future radio survey camera for the next decade.

Mapping the Galactic Magnetic Field with Hydroxyl Masers

Chikaedu Ogbodo (Macquarie)

A comprehensive understanding of cosmic evolution requires adequate understanding of magnetic fields, which are known to pervade the universe in varying scales. Observed at the Galactic scale, magnetism plays essential roles at the onset of star formation, going from a weak diffuse interstellar field to an amplified compressed field. Diffuse and weak large-scale Galactic magnetic fields have been extensively probed using several techniques. But these field strengths are weaker by order(s) of magnitude than those found in high density regions, mostly in the Galactic spiral arms, which are hosts to high-mass star forming (HMSF). The MAGMO (Mapping Galactic magnetic field with OH masers) project is designed to investigate the correlation between field orientations observed in the diffuse large-scale medium and in high-density regions. Expected outcomes inferred by the Zeeman effect (the splitting of emission lines due to the presence of magnetic fields) on OH maser emission lines will determine if the information about the Galactic field orientation is retained after the contraction from weak large-scale magnetic fields to high densities found in HMSF regions. HMSF regions are exclusively traced by 6.7 GHz methanol masers, and we have searched for the Zeeman splitting effect in ground-state Hydroxyl (OH) masers (1612/1720/1665 and 1667-MHz OH transitions) towards 702 targets from the Methanol Multibeam Survey. In my talk I will present the complete polarimetric and detection results for the rarer 1612- and 1720-MHz OH maser transitions, partial preliminary results for the 1665- and 1667-MHz OH maser transitions, and assess the degree to which information about the Galactic-scale magnetic field orientation is revealed by their in-situ magnetic field measurements. I will also present results of the association statistics between the ground-state OH transitions, their relationship with other maser species, and the environment of their host HMSF regions.

The Parkes Ultra Wide-bandwidth Low​ Receiver​

Jane Kaczmarek (DRAO)

Continuing the trend in astronomy to observe over larger and larger bandwidths, the team at CSIRO Astronomy & Space Science has recently designed, manufactured and installed the new Ultra-Wideband Low-frequency (UWL) receiver, which allows for the iconic 64m Parkes radio telescope to simultaneously observe from 0.7 – 4.2 GHz (6:1). With its outstanding sensitivity and polarimetric performance, as well as its ability to carry out high-time resolution astronomy, the UWL has already enhanced the outcomes of a wide range of scientific projects. Key science projects include sensitive tests of general relativity and the search for gravitational waves, the study of the interiors of neutron stars and mapping the structure of the Galactic magnetic field. In this talk, I will introduce the receiver, present recent science results and discuss the planned renewal of the entire receiver fleet on Parkes.

Antenna Array Design, Beam Calibration of the CHIME telescope and Mapping of the North Celestial Cap

Meiling Deng (DRAO)

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a 21cm intensity mapping experiment designed to probe the nature of Dark Energy, which drives the late-time cosmic acceleration of the universe and is one of the biggest puzzles in modern physics. In this talk I will present the work I have done as a CHIME PhD student. My work mainly consists of three parts: the design of the dual-polarized cloverleaf antenna array which matches the next-stage LNA so that its effective noise is about 25 Kelvin across both the frequency domain (400 MHz to 800 MHz) and the scanning angle domain for both polarizations; the simulation and calibration of the CHIME beam for removal of the galactic foreground contamination which is 100,000 times brighter than the 21cm signal; the mapping of the north celestial cap, as a pathfinder to mapping the whole northern hemisphere for better understanding and removal of the CHIME foreground and for galactic science.

Neutral and Molecular Gas at Low Metallicity in the Small Magellanic Cloud with the ATCA, ALMA, and ASKAP

Katie Jameson (CSIRO)

The Small Magellanic Cloud (SMC) provides the only laboratory to study the detailed physics of star formation and the interstellar medium relevant to the high redshift universe. Not only is the transition from warm to cold neutral gas a rate limiting step to the formation of molecular gas, but it appears to influence star formation efficiency globally and we still do not understand how metallicity affects this transition. We present first results from a new HI and OH absorption line study using the ATCA to measure the warm-to-cold atomic fraction and the atomic-to-molecular transition in the SMC. We find very cold (~20 K) temperatures for individual cold gas clouds and an average cold HI cloud temperature of 30 K, lower than in the Milky Way, and a cold atomic gas fraction of 25% for the SMC, which is similar to the Milky Way and the Local Group. ALMA ACA CO observations of a subset of sources have only revealed detectable CO emission near one source with cold HI indicating that many regions with cold atomic gas have little CO emission and possibly no molecular gas. I will also present preliminary results from a new large (1 deg x 0.5 deg) ALMA ACA CO map of the Southwest Bar of the SMC, which shows previously undetectable small (~ 2 pc) molecular gas clumps are found throughout the region. I will compare the CO map with the new GASKAP HI observations and give an overall update on the GASKAP survey.

The CHANG-ES Project and new Results on Polarized Disks and Halos of Galaxies

Judith Irwin (Queen’s University)

CHANG-ES (Continuum Halos in Nearby Galaxies — an EVLA Survey) has surveyed 35 edge-on galaxies using the VLA in three array configurations and two frequencies. With over 400 hours of observing time and detection of all polarization products, this survey has revealed details about the disk-halo interaction and magnetic field structures that have never before been seen in any galaxy. One hundred hours of Greenbank Telescope time have also been obtained for the zero-spacing information. A mature program, more than 20 papers have now been published with the CHANG-ES moniker. This talk will highlight the results to date, including some that are surprising and unexpected.

Remote Talk: The JCMT BISTRO Survey: Variation of magnetic field and grain aligment properties within the Ophiuchus Molecular Cloud

Kate Pattle (National University of Ireland Galway)

The role and relative importance of magnetic fields in the late stages of mass assembly within molecular clouds remains highly uncertain. In this talk I will discuss recent results from the JCMT (James Clerk Maxwell Telescope) POL-2 polarimeter and the JCMT BISTRO (B-Fields in Star-Forming Region Observations) survey, which is currently mapping star-forming regions within 2 kpc of the Solar System in submillimetre polarized light. The resolution and sensitivity of the BISTRO observations allows magnetic fields to be traced from low to high densities in star-forming gas, and provides new insights into the depths into molecular clouds to which dust grains are aligned with the magnetic field. I will particularly discuss recent observations of the nearby Ophiuchus molecular cloud, a well-resolved site of low to intermediate-mass star formation. The proximity of this molecular cloud allows for detailed investigation of the variation of magnetic field morphology and dust grain alignment with local environment within an individual star-forming region. Our results demonstrate that the magnetized behaviour of individual star-forming clumps is strongly influenced by local effects and stellar feedback.

Remote Talk: Galactic Faraday tomography at low frequencies

Cameron Van Eck (Dunlap)

The new generation of low-frequency (sub-GHz) radio telescopes, particularly LOFAR and MWA, have opened up the polarized sky in new and amazing ways. We now have the capability to explore low frequency polarization at high resolution, on large angular scales, and with large fields of view, all at the same time. In my talk I will review low-frequency Faraday tomography to date, and discuss how we can take advantage of the properties of polarization at low-frequencies to inform our analysis of the observations. In some cases, we can break the degeneracies that prevent us from modelling the magnetic field along the line of sight. There are several ongoing, planned, and possible surveys that will let us break open the low frequency polarized sky.

Remote Talk: Collision rates in the Edgeworth-Kuiper belt

Abedin Abedin (DAO)

The Edgeworth-Kuiper belt is a torus shaped agglomeration of icy bodies, beyond the orbit of Neptune, encompassing the Solar System. These bodies are leftover of the formation of Solar System, and have undergone little to no chemical alteration, compared to asteroids, and therefore are considered to be relatively pristine. Today, there are more than 3000 Kuiper belt objects (KBO) discovered of size D> 30 km, which is approximately the ground and space detection limit for these distant objects. Of the sample of 3000 KBOs, more than 800 objects have well established and reliable orbits, as a result of the “Outer Solar System Origin Survey” (OSSOS) and “Canada-France Ecliptic Plane Survey” (CFEPS) surveys. These high-precision orbits allow for dynamical classification of the OSSOS and CFEPS discoveries. We first calculate the intrinsic collision probabilities between each different dynamical class and then combine this study with the size frequency distribution (SFD) model of our sample of KBOs to calculate the collision rates. Since, our ground and space-based observations are good to D>30km, we augment our data with the NASA “New Horizons” spacecraft crater observation on the surfaces of Pluto and Charon. These crater observations can be directly mapped to impactor size, allowing us to bridge the gap between the SFD of D>30km objects down to 1km KBOs. That helps us to understand the collisional history of the Edgeworth-Kuiper belt as well as provides clues as to the dust production as a result of these collisions.

Remote Talk: TBD

Kianoosh Tahani (KPU)