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Research
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 2017-18 committee members are Margaret Meixner (on Sabbatical), Jason Tumlinson (Co-chair), Alaina Henry, Brett Salmon, Ethan Vishniac (JHU Co-chair), Kevin Schlaufman (JHU), and David Nataf (JHU).

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

Date Speaker/Title
Feb. 07 Jennifer Johnson (Ohio State University)
Title: Better Stellar Ages Through Chemistry
Abstract: Reliable stellar ages hold the key to numerous questions of galaxy and stellar system formation. However, they have been frustratingly hard to measure for field stars. While Gaia will improve the situation markedly for nearby turnoff stars, determination of ages for giants will not benefit to the same degree. In this talk, I will discuss the calibration of chemical ages, based on [C/N], which tags the mass of the star, and [alpha/Fe], which tags the time since star formation began. I will use these ages to discuss outstanding problems in the Galaxy, including the amount of radial mixing through the disk, the prevalence of stellar mergers, and the inside-out formation of the Galaxy.
Host: Molly Peeples
Feb. 14 Suzanne Staggs (Princeton University)
Title: Probing the Universe with High-Resolution Cosmic Microwave Background Maps
Abstract: Famously, the rich angular power spectrum of the intensity of the cosmic microwave background (CMB) reveals the state of the universe a mere 10^{13} s after the big bang. In its fine-angular scale details, the CMB also encodes details of the CMB’s interactions with the rest of the universe in the subsequent 4^{17} s. The CMB is slightly polarized by Thomson scattering when there is any local quadrupolar anisotropy in the distribution of the scattering electron population. A primordial gravitational wave (PGW) background would imprint odd-parity polarizations patterns in the CMB polarization at very large angular scales, known as B-modes. Detection of PGWs would have an enormous impact on our understanding of the universe in its earliest instants (as early as 10^{-32} s): inflation is the only proposed primordial source for the as-yet undetected B-modes. At small angular scales, the CMB temperature and polarization maps provide fresh cosmological information, in part because of their sensitivity to the history of the growth rate of structures by gravitational collapse in the expanding universe. The Atacama Cosmology Telescope (ACT) is a special-purpose 6m telescope situated at 17,000 ft in the dry Atacama Desert of northern Chile, at a latitude of 23 degrees South. ACT’s millimeter-wave detectors measure both polarization and intensity at very fine angular scales (arcminutes). I will describe the ACT instrument and its data in the context of other ongoing and proposed CMB measurements, their scientific impact, and the potential discovery space.
Host: Tobias Marriage
Feb. 21 Vicky Kalogera (Northwestern University)
Title: The Dawn of Gravitational-Wave Astrophysics
Abstract: In the past two years the gravitational-wave detections enabled by the LIGO detectors have launched a new field in observational astronomy allowing us to study compact object mergers involving pairs of black holes and neutron stars. I will discuss what current results reveal about compact object astrophysics, from binary black hole formation and core-collapse of massive stars to short gamma-ray bursts and nuclear matter physics. I will also highlight what we can expect in the near future as detectors sensitivity improves and multi-messenger astronomy further advances.
Host: Andy Fruchter
Feb. 28 Gregory Laughlin (Yale University)
Title: Do Planets Form In Situ?
Abstract: In this talk, I will review the lines of evidence both in favor and against in situ formation. Particular focus will be attached to the formation mechanisms of the Kepler multi-transiting systems, as well as to the origin of hot Jupiters. I will also tie recent insights regarding the formation of our own solar system into the larger picture.
Host: Kevin Schlaufman
March 07 Alexandra Pope (University of Massachusetts)
Title: Rise of Dust: Decoding Hidden Star Formation and Black Hole Growth over Cosmic Time
Abstract: The prominent peak in the history of star formation and black hole accretion at cosmic noon suggests strong evolution in the mechanisms that grow stars and black holes in galaxies over time. Infrared observations can uniquely quantify the energy balance between star formation and active galactic nuclei (AGN) activity, and constrain the composition and conditions of the gas and dust available to form new stars. In order to understand the enhanced activity at cosmic noon, we measure the interstellar medium (ISM) conditions in high redshift galaxies by combining diagnostics from mid-IR spectroscopy, far-IR/(sub)mm continuum and CO molecular lines. While ground-based facilities such as ALMA and the Large Millimeter Telescope (LMT) probe the cold ISM, JWST will be crucial for measuring the warm ISM and small dust grains. Looking to the future, a cold infrared telescope like the Origins Space Telescope is needed to decode galaxy growth over all cosmic time.
Host: Jen Lotz
March 14 Andy Howell (Las Cumbres Observatory)
Title: Kilonovae, Pair Instability Supernovae, and the Progenitors of Type Ia Supernovae: Surprises from Las Cumbres Observatory
Abstract: We were one of six groups to first detect and characterize the kilonova associated with the gravitational wave signal GW170817. Using our global network of telescopes at Las Cumbres Observatory we were then able to observe the supernova approximately every 8 hours over the first few days.  I will discuss this and recent results from the Global Supernova Project. One of these includes the supernova iPTF14hls, a hard to understand supernova that has been luminous for years. It has a lightcurve with at least five peaks and spectra that evolve about 8 times slower than other supernovae.  It may be the first example of the theorized class of supernovae associated with stars in the 100 solar mass range: pulsational pair instability supernovae.
Host: Armin Rest
March 21 Kathrin Altwegg (Universität Bern )
Title: Rosetta at Comet 67P: Deciphering the Origin of the Solar System, the Earth and Life
Abstract: After more than 12 years the Rosetta spacecraft crash-landed on comet Churyumov-Gerasimenko on September 30, 2016. It has traveled billions of kilometers, just to study a small (4 km diameter) , black boulder named 67P/Churyumov-Gerasimenko. The results of this mission now seem to fully justify the time and money spent in the last decades on this endeavor. In the talk I will look back on the craziest mission ever flown by the European Space Agency and point out its technical challenges and scientific highlights. I will show how the results of this mission change our understanding about the formation of the solar system, the Earth and finally life itself.
Host: Ben Sargent
March 28 Jay Strader (Michigan State University)
Title: Black Holes in Globular Clusters
Abstract: TBS
Host: Laura Watkins
April 04 Victoria Meadows (University of Washington)
Title: The Habitability of M Dwarf Planets
Abstract: TBS
Host: Jason Tumlinson
April 11 Steve Kawaler (Iowa State University)
Title: Connecting Highly Evolved Stars with Their Younger Selves through Space-based Asteroseismology
Abstract: By awakening us to the amazing abundance of other planetary systems, the Kepler mission was a landmark in advancing our understanding of the Universe. The mission (and its follow-on, K2) produced extremely accurate brightness measurements of nearly 200,000 stars, with continuous light curves spanning months to years. Beyond planet hunting, Kepler was also an "asteroseismology machine," revealing the subtle seismic vibrations of the stars. Through  asteroseismology, the data has exposed the internal structure of hundreds of main sequence stars, thousands of red giants, and dozens of white dwarfs - providing an exquisite record of the behavior of stars from birth to old age. In this talk I’ll discuss the contributions that asteroseismology has been able to make in tracing the evolution of stellar interiors, and plans for asteroseismology with new missions such as TESS and PLATO.
Host: David Soderblom
April 18 Melissa Ness (MPIA)
Title: Mapping the Milky Way's Assembly with Data Driven Spectroscopy
Abstract: TBS
Host: David Nataf
April 25 No Colloquium
May 02 Nitya Kallivayalil (University of Virginia)
Title: Milky Way Cosmology: Towards Full 6-D Dynamical Mapping of the Nearby Universe
Abstract: TBS
Host: Annalisa Calamida and Tony Sohn
May 09 Suvrath Mahavedan (Pennsylvania State University)
Title: High Precision Near-infrared and Optical Radial Velocities: Challenges, Progress, & Promise
Abstract: TBS
Host: Kevin Schlaufman
May 16 Alan Dressler (Carnegie Institution for Science)
Title: Late Bloomers: What ELSE Influences Star Formation Histories of Galaxies?
Abstract: TBS
Host: Marc Rafelski
May 23 Sheperd Doeleman (Harvard University)
Title: The Event Horizon Telescope: Imaging and Resolving a Black Hole
Abstract: TBS
Host: TBS