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Colloquium Series

All talks are held on Wednesdays in the STScI John N. Bahcall Auditorium at 3:30 p.m. preceded by tea at 3:15 p.m.

Please direct questions or comments to the colloquium committee. The 2016-17 committee members are Brad Whitmore (chair), Gabe Brammer, Andy Fruchter (ex officio), Olivia Jones and Nora Luetzgendorf.

STScI presents live and archived webcasting of talks and Colloquium Series.

Date Speaker/Title
Feb. 01 (CoolSci Talk Series)
Feb. 08 (No Colloquium)
Feb. 15 Amy Reines (National Optical Astronomy Observatory)
Title: The Origin of Supermassive Black Holes
Abstract: The origin of supermassive black holes remains a major outstanding issue in modern astrophysics. These monster black holes reside in the nuclei of essentially every massive galaxy and power the most luminous quasars at the edge of the observable Universe. However, directly observing the first “seed” black holes in the early Universe - that can eventually grow to upwards of a billion solar masses - is not feasible with current telescopes. Present-day dwarf galaxies, on the other hand, are within observational reach and offer another avenue to learn about black hole seeds since low-mass galaxies can host relatively pristine black holes. In this talk, I will highlight some of my recent achievements in this field that have taken us from a few rare examples to large systematically-assembled samples of dwarf galaxies hosting nuclear black holes. I will also discuss how my work has implications for directly detecting black hole activity in the first galaxies at high redshift.
Host: Nora Luetzgendorf
Feb. 22 Jessica Lu (University of California Berkeley)
Title: Finding Black Holes with Astrometric Microlensing
Abstract: TBS
Host: Andrea Bellini
Mar. 01 Renée Hlozek (University of Toronto)
Title: Constraining Ultra-light Axions with CMB data: Shining Light on the Lightest Particle Dark Matter Candidates
Abstract: CMB cosmology is currently undergoing a data-rich epoch, with measurements on small scales from experiments like the Atacama Cosmology Telescope (ACT) and its polarisation instrument, ACTPol, adding to measurements on larger scales by Planck, WMAP and most recently BICEP. I will contextualise the measurements and present constraints on cosmological models of interest to small-scale experiments; while noting that foregrounds that complicate our measurements of the primordial microwave sky. I'll present recent ACTPol results and highlight the next generation of the experiments in the Simons Observatory and the Fourth Stage CMB experiment (CMB S4): ensuring CMB cosmology has a rich future to look forward to on the ground!
I'll also concentrate on how we can use the CMB to constrain the lightest potential dark matter particles. I'll pay particular attention to constraints on models of ultra-light axions (ULAs). ULAs are a type of dark matter well motivated by particle physics, that impact our cosmological measurements by suppressing structure and affecting the CMB. I'll highlight previous work which constrained ULAs with mass in the range 10-^{32} eV→10^{-26} eV, current limits are that they can compose a fraction <0.01 of the cosmological critical density of the universe. CMB-S4 should be ~10 times more sensitive to the ULA energy-density than Planck data alone, across a wide range of ULA masses 10-32 < ma < 10-23 eV, and will probe axion decay constants of fa≈1016 GeV, at the grand unified scale. It should also improve the CMB lower bound on the ULA mass from ~10-25 eV to 10-23 eV, nearing the mass range probed by dwarf galaxy abundances and dark-matter halo density profiles. These improvements will allow for a multi-σ detection of percent-level departures from CDM over a wide range of masses.
Host: Arfon Smith
Mar. 08 Mike Brown (California Institute of Technology)
Title: Planet Nine from Outer Space
Abstract: The recent suggestion of evidence for a massive ninth planet in the outer solar system has set off a worldwide search to find this latest member of our planetary family. I will discuss the evidence for the planet and show how we are working to constrain the mass and orbital parameters of the body. I will also point out some of the unexpected features in the solar system that ninth planet explains, including obliquity of our sun. Finally, I will show the latest results from the search for Planet Nine.
Host: Marc Rafelski
Mar. 15 (CANCELED)
Mar. 22 (CANCELED)
Mar. 29 Rob Kennicutt (University of Cambridge)
Title: From Gas to Stars
Abstract: It is now clear that the conversion of interstellar gas to stars, together with the subsequent feedback from massive star formation on the ISM are fundamental agents in the formation, evolution, and shaping of galaxies. Thanks to a wealth of recent observations from the ground and space our empiriral characterization of these processes is being revolutionized, yet our understanding of the underlying physical processes which trigger and regulate large-scale star formation remains embryonic. This talk will review the many advances made over the past decade in understanding the coupling of star formation to the interstellar medium, and highlight the key challenges which remain.
Host: Margaret Meixner
Apr. 05 (No Colloquium)
Apr. 12 Armin Rest (STScI)
Title: Taking the Measure of the Universe with Stellar Explosions
Abstract: Type Ia supernovae (SNe Ia) are superb distance indicators and are used to map the expansion history of the Universe. Two decades ago, astronomers used observations of SNe Ia to find that the Universe's expansion is currently accelerating. Since this initial discovery, we have used SNe Ia to constrain the nature of "dark energy," which drives this accelerated expansion. To improve our dark energy constraints beyond our current basic understanding, we must design new and better SN surveys as well as improve our understanding of the physics of the SN explosion itself. I will show how high-cadence Kepler telescope light curves have provided us with crucial insight into the progenitor channels and physics of SN explosions. With light echoes of historic SNe, we can investigate the cause (the explosion/eruption) and the effect (the remnant) of the same astronomical event, even allowing us to look at the same event from different directions. I will also present the Foundation Supernova survey, a new high-fidelity, low-redshift (z < 0.1) survey I started in 2015 that will replace the current heterogenous low-redshift sample and reduce the (currently) largest uncertainties for SN cosmology. I will discuss the next major leap in SN cosmology, pushing to high-redshift and NIR with JWST and WFIRST. With the combination of the Foundation survey, the next generation of space-based observatories, and new physical understanding, SNe Ia will remain a premier cosmological probe, continuing the legacy started decades earlier.
Host: Dave Soderblom
Apr. 19 Eliza Kempton (Grinnell College)
Title: Revealing the Atmospheres of Extrasolar Super-Earths
Abstract: Discoveries of extrasolar planets over the last two decades have reshaped our understanding of how planetary systems form. Super-Earths – planets intermediate in size/mass between Earth and Neptune – do not exist in our Solar System, and the discovery of such planets poses a challenge to theories of planetary formation and composition based on the Solar System paradigm. Through observations of the atmospheres of these planets, we can learn about their formation history, their climate, and in some cases their propensity to support life. This talk will focus on the modeling of super-Earth atmospheres as it relates to current and future observations. I will detail the current state of characterization efforts for super-Earth atmospheres, focusing on the challenges and successes in modeling and interpreting the early observations of these objects. I will conclude with a forward-looking view of super-Earth atmospheric studies over the next 5-10 years, in the era of JWST and 30-meter class ground-based telescopes.
Host: Nikole Lewis
Apr. 26 (Spring Symposium, No Colloquium)
May 03 Jan Cami (Western University)
Title: Space Buckyballs: The Hidden Life of Cosmic Fullerenes
Abstract: In recent years, the fullerene species C$_{60}$ (and to a lesser extent C$_{70}$) has been detected in a variety of astrophysical environments -- from the circumstellar carbon-rich surroundings of evolved stars to interstellar reflection nebulae and young stellar objects. Understanding how these species form, evolve and respond to their environment yields important insights into astrochemistry and the characteristics of large aromatics in space, thought to be the main reservoir of organic material in space. In this talk, I will present an overview of what we have learned about cosmic fullerenes from astronomical observations, theoretical calculations and recent laboratory experiments, and show how fullerenes have significantly changed our under- standing of interstellar chemistry. I will discuss the conditions that appear to be conducive to the formation and/or detection of fullerenes, and highlight some of the difficulties we still face in understanding the formation of fullerenes in planetary nebulae.
Host: Gail Zasowski
May 08 Rainier Weiss (Massachusetts Institute of Technology), Bahcall Lecture
Title: Observation of the Merger of Binary Black Holes: The Beginning of Gravitational Wave Astronomy
Abstract: Rainer Weiss on behalf of the LIGO Scientific Collaboration

After some history of gravitational waves will follow with a description of the waves and the technique for detecting them. Present and discuss the observations and end with a vision for the future of gravitational wave astronomy and astrophysics.
Host: TBD
May 10 Vicky Kalogera (Northwestern University)
Title: Gravitational-Wave Discoveries and Black-hole Astrophysics
Abstract: TBS
Host: Marc Postman
May 17 Adam Leroy (The Ohio State University)
Title: Detailed Physical Conditions and Star Formation in the ISM of Nearby Galaxies
Abstract: TBS
Host: Karl Gordon
May 24 Bob Abraham (University of Toronto)
Title: Exploring the Low Surface Brightness Universe with Dragonfly
Abstract: TBS
Host: David Law
May 31 Jim Fuller (California Institute of Technology)
Title: Asteroseismic Signature of Internal Stellar Magnetic Fields
Abstract: TBS
Host: Steve Lubow