MN Institute for Astrophysics Colloquium

semester, 2018


Friday, January 5th 2018
Speaker: No colloquium this week.

Friday, January 12th 2018
Speaker: No colloquium this week.

Friday, January 19th 2018
Speaker: No colloquium this week.

Friday, January 26th 2018
Speaker: No colloquium this week.

Friday, February 2nd 2018
Speaker: No colloquium this week.

Monday, February 5th 2018
Speaker: Jeff Pedelty, NASA
Subject: Jeff will share his diverse experiences while working for NASA and its industrial partners.

Jeff earned a B.S. in physics from the Iowa State University in 1981 and a Ph.D. in astrophysics from the University of Minnesota in 1988. His thesis combined observational radio astronomy with Professor Rudnick and computational fluid dynamics with Professor Woodward. Since leaving Minnesota he has worked for NASA’s Goddard Space Flight Center in Greenbelt, MD. He supported the Nobel-winning Cosmic Background Explorer (COBE), the Earth science missions Landsat 7, 8, and 9, and the Joint Polar Satellite System (JPSS-1) weather satellite. He also worked in the areas of high performance computing, signal and image processing, astrobiology, and remote sensing science. For the past 10 years he has worked for the Landsat Project onsite at Ball Aerospace in Boulder, CO and at Orbital ATK in Gilbert, AZ.


Friday, February 9th 2018
Speaker: Terry Jones, University of Minnesota
Subject: Interstellar Polarization

This talk will start with a bit of retrospective on my career in astronomy, after which I will focus on the topic of interstellar polarization. I will concentrate on work done here at the University of Minnesota, up to current work using MMTPol on the MMT and HAWC+ on SOFIA. The primary science goal of this work is to study the magnetic field geometry in all phases of the interstellar medium, and determine what limitations there are to that effort. Lastly, I will describe some future trends.


Friday, February 16th 2018
Speaker: Evan Skillman, MIfA
Subject: The Resolved Stellar Populations JWST Early Release Science Program

Our JWST ERS program will obtain deep multi-band NIRCam and NIRISS imaging of three resolved stellar systems within 1 Mpc. We will use this broad science program to optimize observational setups and to develop data reduction techniques that will be common to JWST studies of resolved stellar populations. We will combine our expertise in HST resolved star studies with these observations to design, test, and release point spread function (PSF) fitting software specific to JWST. PSF photometry is at the heart of resolved stellar populations studies, but is not part of the standard JWST reduction pipeline. Our program will establish JWST-optimized methodologies in six scientific areas: star formation histories, measurement of the sub-Solar mass stellar IMF, extinction maps, evolved stars, proper motions, and globular clusters, all of which will be common pursuits for JWST in the local Universe. Our observations will be of high archival value (e.g., for calibrating stellar evolution models, measuring properties of variable stars, and searching for metal-poor stars) and will provide blueprints for the community to efficiently reduce and analyze JWST observations of resolved stellar populations.


Friday, February 23rd 2018
Speaker: Attila Kovacs (SAO)
Subject: Far-infrared frontiers

The far-infrared (FIR) and (sub)millimeter bands provide us with unique views of structure formation in the Universe and the Galaxy alike. At these wavelengths we have the most adept probes of active star-formation that sample almost all of the reionized Universe (z~1--10) with essentially no bias. The Sunyayev Zel'dovich effect traces the assembly of galaxy clusters regardless of cosmological distance. Locally, in the Galaxy, FIR polarimetry probes the magnetic environments and dust properties around optically obscured young stars and cores, while FIR spectroscopy can spy on the ices in planetary disks. I will also highlight some of the ground-braking recent and upcoming instrumentation and technologies I work on to can deliver this scientific treasure trove.


Friday, March 2nd 2018
Speaker: Dr. Mateusz Ruszkowski, U. Michigan
Subject: The role of cosmic rays in stellar and supermassive black hole feedback

I will discuss the role of cosmic rays in stellar and supermassive black hole feedback. I will argue that cosmic rays are likely to play a very important role across a large range of distance scales -- from the scales of individual galaxies to the scales comparable to those of cool cores of galaxy clusters.

Regarding the galactic scale feedback, I will focus on supernova and cosmic ray driven winds. Galactic outflows play an important role in galaxy evolution and, despite their importance, detailed understanding of the physical mechanisms responsible for the driving of these winds is lacking. Although cosmic rays comprise only a tiny fraction of interstellar particles by number, they carry energy comparable to that in the thermal gas. I will describe a suite of global 3D MHD numerical simulations that focus on the dynamical role of cosmic rays injected by supernovae, and specifically on the impact of cosmic ray transport along the magnetic fields. Our results show that this microphysical effect can have a significant impact on the wind launching depending on the details of the plasma physics.

Regarding the feedback on galaxy cluster scales, I will discuss results from our simulations of black hole jets in cool cores of galaxy clusters including the effects of cosmic rays. I will argue that cosmic ray heating of the intracluster medium (ICM) may be a very important heating mechanism both in the tenuous and cold phases of the ICM while not violating observational constraints.

While largely an unexplored territory in the context of galactic winds and AGN feedback, cosmic ray feedback is an important process facilitating launching and efficient driving of galactic-scale winds in starburst galaxies and heating of the ICM and remains the subject of intense research.

Faculty Host: Thomas W. Jones

Friday, March 9th 2018
Speaker: David Sand, U. Arizona
Subject: Unveiling the Physics and Progenitors of Cosmic Explosions with a One Day Cadence Supernova Search

Supernovae (SNe) are a linchpin for understanding the chemical evolution and star formation history of the Universe. Despite progress, some of the most basic questions about SNe persist, and we seek to answer the question: What are the explosion mechanisms and progenitor star systems of SNe? In the early hours to days after explosion, SNe provide clues to how they explode, and what their
progenitor star systems were. Observing these ephemeral signatures requires a fast search cadence and immediate spectroscopic response, a dual feat which has been difficult to achieve. Motivated by the need to discover, and study, SNe within the first day of explosion, we have begun a one-day cadence SN search of nearby galaxies (D<40 Mpc; also known as the DLT40 Survey) with a PROMPT 0.4-m telescope directly tied to the robotic FLOYDS spectrographs, a pair of instruments that I helped to develop. Here I will highlight our team's initial discoveries, with an eye towards what will be achievable with future time domain
surveys -- perhaps including nearly automated follow-up of LSST transients and Advanced LIGO gravitational wave events with the suite of Steward Observatory's small telescopes.

Faculty Host: M. Claudia Scarlata

Friday, March 16th 2018
Speaker: No colloquium this week - Spring Break

Friday, March 23rd 2018
Speaker: Dr. Jordan Stone, U. Arizona
Subject: Thermal Infrared Probes of Exoplanetary Systems with LBTI

Understanding the gas-giant planet formation process is confused by the fact that it appears multiple formation routes produce objects a few times the mass of Jupiter, where the low-mass tail of the stellar mass function and the high-mass tail of the planet mass function overlap. Distinguishing the formation route for particular objects is challenging but important to create the clean samples necessary to constrain both the planet formation process and the tail-end of the star/brown dwarf-formation process. In particular, constraining the disk-based planet formation mechanism for gas-giants is important because their dynamical dominance affects the formation of terrestrial and ice-giant planets. System architecture and atmospheric composition both provide formation indicators for gas-giants because disk-based formation results in non-hierarchical orbits and atmospheric metal enrichment, as seen in Jupiter and Saturn. I will discuss two programs which I lead with LBTI to probe the outer architecture of planetary systems and to characterize the atmospheres of gas-giant exoplanets. I will also provide an update on the LBTI HOSTS survey for exozodiacal dust around nearby stars. HOSTS is nearing completion and will provide essential information for the design of future space missions that aim to image habitable zone terrestrial planets in reflected light.

Faculty Host: Charles E. Woodward

Friday, March 30th 2018
Speaker: Lou Stolger, Space Telescope
Subject: The Rates of Supernovae, Far and Near

For nearly two decades, the Hubble Space Telescope has been heavily used to locate supernovae in high redshift environments, with the primary goal of improving constraints on the nature of dark energy. Along the way we have made surprising observations on the nature of supernovae themselves, and clues to their elusive progenitor mechanisms, some of which are difficult to reconcile with observations at much lower redshift. From complete volumetric supernova rate histories that now extend to z > 2 we find type Ia supernova delay-time distributions are consistent with a power law index of -1, but with the fraction of prompt (t_d < 500 Myr) is less than expected from various ground-based surveys. Core collapse supernova rates trace the cosmic star formation rate history, but require stellar progenitors more massive than has been seen in deep studies of nearby events (M > 20 M_sol). I’ll detail some interesting discoveries from our recent campaigns on clusters of galaxies, and also discuss what we expect to find with the James Webb Space Telescope, launching in 2018, and with WFIRST in the 2020s.


Friday, April 6th 2018
There will be no colloquium this week.

Friday, April 13th 2018
Speaker: No speaker this week.
Faculty Host: M. Claudia Scarlata

Friday, April 20th 2018
Speaker: No colloquium - See info for the Kaufmanis Public Lecture on the 18th

Friday, April 27th 2018
Speaker: Dr. Christian Veillet, Large Binocula Telescope Observatory (LBTO)
Subject: The Large Binocular Telescope Observatory

With its two 8.4m mirrors on a common mount that can be combined to form an interferometer with a baseline of 23m, complemented with adaptive secondary mirrors, the Large Binocular Telescope provides unprecedented ground-based resolution at near- and mid-infrared wavelengths. With a suite of state of the art instruments nearing completion, the observatory is moving to full operation while adding new capabilities such as ground-layer AO and new AO-fed instrumentation. We will explore the various fields in which LBT has already contributed and stress the importance of the years to come for bringing to fruition the investment made by the LBT partners (UMN is one of theme!) and place LBT as the forerunner of the next generation telescopes scheduled to see first light in the mid-2020s.

Faculty Host: Charles E. Woodward

Friday, May 4th 2018
Speaker: Dr. Silvia Protopapa, U. Maryland
Subject: Probing the Formation and Evolution of the Solar System Through Compositional Analysis

Over the past decade, the synergy of ground- and space-based observations, modeling efforts, and laboratory studies has highlighted vital information on the composition of solar system bodies. I will discuss some of the latest results from New Horizons at Pluto and contrast them with emerging trends seen in other trans-Neptunian objects and comets – the primitive remnants of the planetesimal disk from which the outer planets formed. I will demonstrate how characterizing the composition of these objects, which requires performing laboratory measurements and applying advanced modeling techniques to interpret state-of-the-art ground- and space-based observational data, improves our understanding of the primordial solar nebula and the accretion processes that led to the formation of the planets. I will also outline future work and perspectives in light of recent results.

Faculty Host: Charles E. Woodward

Friday, May 11th 2018
There will be no colloquium this week

Friday, September 14th 2018
Speaker: Paul Woodward, University of Minnesota
Subject: 3-D Stellar Hydrodynamics of Convective Boundary Mixing and its Consequences for Stellar Evolution

Together with collaborator Falk Herwig, at the University of Victoria, in Canada, my research team has been investigating inherently 3-D processes in stellar interiors and their effects upon stellar evolution. This work has been underway in earnest since 2013. We are focusing on brief events in stars that take place over durations of days or hours, but which involve large releases of energy due to the burning of fuels pulled into convection zones from unburned layers above. I will describe the contexts of these brief events, results of our simulations of them, and explain key aspects of how we are able to simulate them at an affordable cost. Some of our very recent work on core convection in rotating massive main sequence stars will be presented, and prospects for future work on the merger of nuclear burning shells in massive stars will be discussed.


Friday, September 21st 2018
Party for Terry Thibeault, no colloquium.

Friday, September 28th 2018
No Colloquium. Physics Colloquium speaker is a planetary physicist.

Friday, October 5th 2018
There will be no colloquium this week

Friday, October 12th 2018
Speaker: Lucy Ziurys, University of Arizona
Subject: A Molecular View of the Late Stages of Stellar Evolution: Millimeter Observations of Supergiants and Planetary Nebulae

Molecular rotational lines, observed primarily at millimeter wavelengths, are unique probes of the environments around dying stars. They not only provide insight into the physics and chemistry of the stellar winds, but also can probe interior nucleosynthesis through isotopic composition. Using the millimeter/sub-mm telescopes of the Arizona Radio Observatory, we have been conducting extensive observations of molecular lines in the envelopes of supergiant/hypergiant stars, as well as in planetary nebulae. Our past work on supergiant VY Canis Majoris revealed a complex velocity structure with multiple, highly-collimated outflows, linked to known dust features. The molecular data confirm the occurrence of multiple, recent mass loss events. Our more recent study of NML Cygnus suggests a very similar mass loss scenario in the winds of this supergiant. In addition, the envelopes of both stars exhibit a unique chemistry with refractory oxides. Our very recent studies of planetary nebulae (PNe) show that these highly ionized objects are also rich in molecular material. Observations of over 20 different nebulae at various evolutionary stages reveal the presence of many polyatomic species such as HCN, HNC, CN, H2CO, CCH, and c-C3H2. Moreover, the abundances do not decrease with the age of the nebulae, and are in fact quite high in very old objects such as the Helix. These results suggest that PNe ejecta are at least partly molecular in content. Some of these nebulae also have enriched C, N, O isotopes. For example, K4-47 has 12C/13C = 2.0, 16O/17O = 21.4 and 14N/15N = 13.3, suggesting some explosive event at the end of the Asymptotic Giant Branch (AGB) phase. In addition, K4-47 appears to be contain many unidentified molecular lines – the target of laboratory spectroscopy studies that we also conduct to aid in our astrophysical interpretation.


Friday, October 19th 2018
Speaker: Adam Frank, University of Rochester
Subject: Blowing Away Exoplanets: The Photo-evaporation of Planetary Atmospheres

Mass loss from exoplanets driven by stellar photo-ionizing fluxes may be a fundamental process setting the final state of planetary atmospheres and, therefore, habitability. In this talk I present new results from 3-D AMR multi-physics simulations exploring the processes and consequences of atmospheric photo-evporation including its observation signatures.


Friday, October 26th 2018
Speaker: Bin Chen,Center for Solar Terrestrial Research, New Jersey Institute of Technology
Subject: Solar Flare Observations with the Karl G. Jansky Very Large Array

Known as one of the most capable radio telescopes for studying various astronomical objects in the universe, the Karl G. Jansky Very Large Array (JVLA) is also commissioned to observe the Sun in a wide range of radio wavelengths from <1 GHz to 18 GHz. Thanks to the Sun’s proximity, the JVLA can be configured as a powerful data machine when observing the Sun, capable of generating over one billion (1,000,000,000) radio images per hour of observing at an ultra-high time cadence (10 milliseconds), spectral resolution (~1%), and spatial resolution (~21”/f GHz). JVLA’s powerful dynamic spectroscopic imaging capability, combined with its high sensitivity, offer unique means for studying various radio emission from the Sun, particularly radio bursts emitted by energetic electrons accelerated in solar flares. We have recorded dozens of flare events with various sizes since 2011. The study of a subset of these flare events has yielded new insights on the magnetic energy release, particle acceleration and transport processes, which are not only important in solar flare physics, but also relevant in space physics and astrophysics contexts that involve magnetized plasma. I will discuss recent results based on these JVLA flare observations.


Friday, November 2nd 2018
Speaker: Vanessa Bailey, NASA Jet Propulsion Laboratory (JPL)
The WFIRST Coronagraph Instrument

The Coronagraph Instrument (CGI) for NASA's Wide Field Infrared Survey Telescope (WFIRST) will constitute a dramatic step forward for high-contrast imaging, integral field spectroscopy, and polarimetry of exoplanets and circumstellar disks, aiming to improve upon the sensitivity of current direct imaging facilities by 2-3 orders of magnitude. Furthermore, CGI will serve as a pathfinder for future exo-Earth imaging and characterization missions by demonstrating wavefront control, coronagraphy, and spectral retrieval in a new contrast regime. I will discuss the status of the instrument design, some of its key new technologies, and its potential science yield.


Friday, November 9th 2018
Speaker: Gautham Narayan, Space Telescope Science Institute
Subject: From Tens to Tens of Thousands: Supernovae Science in the Big-Data Era

’ll discuss SN2018oh and SN2018agk -- two of the spectroscopically confirmed SNIa with exceptional early-time observations discovered by the Kepler Extragalactic Survey (KEGS) with K2 during the forward-facing campaign 17. I’ll detail the constraints we infer from comparing the data of these two objects to physical models of type Ia explosions, and discuss the implications for different SNIa progenitor scenarios. But two does not a sample make, and Kepler SN are relatively rare events. To find more of them, we must move to wide-field ground-based surveys. I’ll discuss work to use cutting edge data science and machine learning techniques to identify such events within the tens of thousands being discovered in real-time. Finally, I’ll outline how we’re preparing the community to jump scale from the current-generation of surveys to LSST.


Friday, November 16th 2018
Speaker: Brian O'Shea, Michigan State University
Subject: Connecting the first stars in the universe to the Milky Way

Galaxies are complicated beasts - many physical processes operate simultaneously, and over a huge range of scales in space and time. As a result, creating accurate models of the formation and evolution of galaxies over the lifetime of the universe presents tremendous challenges. In this talk I will discuss these challenges and their solutions, and will explain how large-scale computational models can be used to gain insights into the very first galaxies that formed in the universe (over 13 billion years ago!), and how we can use both these computational models and observations of the Milky Way and its neighbors to infer how galaxies have grown and evolved in the intervening time.


Friday, November 30th 2018
Speaker: No Colloquium

Friday, December 7th 2018
Speaker: Tracy Clarke, Naval Research Lab
Subject: Low Frequency Astrophysics: From FRBs to Surveys

Low frequency interferometry is re-emerging as powerhouse for astrophysical studies. Hot-topic areas include the search for extrasolar planets, detecting fingerprints of the first stars, localizing and identifying the hosts of fast radio bursts (FRBs), and tracing shocks, turbulence and feedback in clusters of galaxies. In this talk I will discuss the revitalization of low frequency interferometry, including a discussion of current interferometers and capabilities. I will specifically highlight a new commensal low frequency system we developed on the NRAO VLA that provides data 24/7 from this powerful interferometer. I will discuss several individual programs where low frequencies play a leading role in the research and end with a look to the future of low radio frequency with ngLOBO (a complementary system to the ngVLA) and the SKA. Authors: T. E. Clarke (Naval Research Laboratory)


Friday, December 14th 2018
Speaker: Rafaella Margutti, Northwestern University
Subject: Discovery frontiers in the new era of Time Domain Multi-Messenger Astrophysics

New and improved observational facilities are sampling the night sky with unprecedented temporal cadence and sensitivity across the electromagnetic spectrum. This exercise led to the discovery of new types of astronomical transients and revolutionized our understanding of phenomena that we thought we already knew. In this talk I will review some very recent developments in the field that resulted from the capability to acquire a true panchromatic view of the most extreme stellar deaths in nature.

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