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Staff Research
2018 Fall Series

All talks are held on Wednesdays in the STScI John N. Bahcall Auditorium at 3:00 p.m. preceded by tea at 2:45 p.m.

Please direct questions or comments to the colloquium committee. The 2018-19 committee members are Jason Tumlinson (Chair), Alaina Henry, Lea Hagen, Ethan Vishniac (JHU Co-chair), Kevin Schlaufman (JHU), and Kate Rowlands (JHU).

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

Date Speaker/Title
Sept. 05 Jennifer C. Yee (Harvard-Smithsonian Center for Astrophysics)
Title: Microlensing Perspectives on Cool Planet Populations
Abstract: Microlensing is uniquely capable of studying planets across a wide range of masses at a few AU from their host stars. At the lower masses, these planets are difficult to impossible to find with other techniques. I will discuss recent results in microlensing suggesting a turnover in the planet mass ratio function around 10^-4, i.e. that planets with mass ratios similar to Neptune are the most abundant at separations probed by microlensing. I will also discuss microlensing constraints on the free-floating planet population. Finally, I will discuss how current and future microlensing surveys, including WFIRST, will advance our understanding of cool planet populations.
Host: TBD
Sept. 12 Misty Bentz (Georgia State University)
Title: Black Hole Masses in Active Galaxies
Abstract: One of the unexpected results from 25 years of observations with the Hubble Space Telescope is the discovery that supermassive black holes inhabit the centers of all massive galaxies, and these black holes appear to have a symbiotic relationship with their host galaxies. In order to further our understanding of this unexpected relationship, the masses of the black holes must be determined. However, black hole mass measurements are difficult to achieve because they require direct observations of the black hole's gravitational influence on luminous tracers. A few different techniques have been developed over the last 25 years to meet this goal. One technique, known as reverberation mapping, is exclusively applicable to active black holes but may be used for even the most distant quasars in our universe, providing a way to study black holes across history. On the other hand, the most widely used technique in the local universe requires exquisite spatial resolution and is based on observations of the bulk motions of stars deep in the nucleus of a (usually inactive) galaxy. I will introduce these techniques and describe our ongoing program to identify a small sample of galaxies where multiple black hole mass techniques can be applied to each galaxy. This effort includes our recently-approved JWST ERS program, as well as programs carried out on multiple moderate- and large-aperture ground-based telescopes. The results of this work will allow us to directly test these independent mass measurement techniques against each other, investigating whether all black hole masses are on the same scale and thus having implications for our understanding of the evolution of galaxies across the ~13 billion year history of the universe.
Host: TBD
Sept. 19 No Colloquium
Sept. 26 No Colloquium
Oct. 03 No Colloquium
Oct. 10 No Colloquium
Oct. 17 TBS (TBS)
Title: TBS
Abstract: TBS
Host: TBD
Oct. 24 Laurent Pueyo (Space Telescope Science Institute)
Title: Exoplanet Imaging: From Precision Optics to Precision Measurements
Abstract: I will first present recent observational results pertaining to the formation history of giant planets. This work was mostly carried out using the Gemini Planet Imager instrument: I will highlight our group’s successful effort to deliver a uniform and self-consistent family portrait of the atmospheric compositions and orbital properties of nearby young Jupiter analogs. I will discuss what these results teach us about Jovian planet formation, and how they can be completed by ongoing HST and future JWST observations. I will then delve into future experiments aimed at identifying biomarkers in the atmosphere of temperate earth analogs. I will present our group’s recent results on optimizing earth finding coronagraphs with large segmented apertures in space. Finally, I will discuss current challenges in space based high-contrast instrumentation, along with my vision for both science and technology roadmaps towards a Large UV/Optical/IR (LUVIOR) Surveyor.
Host: N/A
Oct. 31 Sergey Koposov (Carnegie Mellon University)
Title: Galactic Archeology in the Gaia Era
Abstract: Galactic archaeology is the field that studies tiny remnants and traces of processes that lead to the formation of our Galaxy. In the past decade, this field was pushed forward by large imaging surveys, allowing us to detect large populations of faint dwarf galaxies around the Milky Way, discover new stellar streams and probe the Milky Way stellar halo in unprecedented detail. This year, however, this field was revolutionized by the arrival of Gaia astrometric dataset that for the first time offers a 3-D map of our Galaxy, as well as provides precise proper motions for more than a billion stars. In my talk, I will discuss some of the recent results and discoveries of various sub-structures in the Milky Way halo done before the arrival of the Gaia data as well as highlight some of the interesting fresh results obtained with the help of Gaia.
Host: TBD
Nov. 07 Susan Kassin (Space Telescope Science Institute)
Title: How Do Galaxies Evolve into the Forms They Have Today?
Abstract: This talk will summarize my recent observations of disk and spheroidal galaxies, which challenge and enrich our pictures of how they form. I will show how the internal kinematics of star-forming galaxies, measured from Keck spectroscopy and Hubble images, evolve across a range of redshifts (0 to 2.5) and galaxy stellar masses. These observations demonstrate that Milky Way mass galaxy disks followed a tempestuous path to settling ino their currently well-ordered states. Star-forming galaxies at high redshifts are only just assembling. They are kinematically disordered and gradually settle over billions of years into ordered rotationally supported systems on the Hubble Sequence. Low mass galaxies today are kinematically disordered. They struggle to form disks if their masses are below 10^9.5 solar masses, a characteristic mass for disk formation. From measurements of the star-formation histories of spheroidal galaxies, we find that the timescales of spheroidal assembly and quenching evolve with time and galaxy mass. Their evolution is faster at higher redshift and higher mass. Finally, I will show how JWST spatially-resolved spectroscopy is poised to reveal the dynamical state of galaxies soon after reionization.
Host: N/A
Nov. 14 Kate Rubin (San Diego State University)
Title: On the Morphologies of Cool Circumgalactic Gas Flows: Insights from Absorption- and Emission-Line Tracers
Abstract: Quasar absorption line experiments with HST have revealed the mass of diffuse gas in the halos of ~L* galaxies to be at least comparable to the baryonic mass of the galaxies’ disks. However, these studies provide limited information on the spatial distribution of this circumgalactic material, such that its relationship to the gas accretion and galactic winds that are thought to regulate star formation in the host galaxies remains poorly understood. I will discuss alternative approaches using spatially-resolved spectroscopy from the SDSS-IV/MaNGA survey and the Keck Cosmic Web Imager to demonstrate, e.g., that bipolar outflows occur with higher frequency closer to the nuclei of nearby star-forming galaxies; a surprisingly high incidence (but small cross section) of cool gas accretion onto these same systems; and that the incidence of both outflows and inflows increases with star formation rate. Such three-dimensional study will ultimately reveal the role of this massive, diffuse baryonic reservoir in feeding galaxy growth.
Host: Marc Rafelski and Kate Rowland
Nov. 21 No Colloquium
Nov. 28 Karen Masters (Haverford College)
Title: Galaxy Evolution from Nearby Resolved Galaxies
Abstract: The morphology of a galaxy provides information on the orbits of stars within it. As such, important clues to the formation history of galaxies is revealed by their morphologies, and this information is complimentary, but not identical to, their star formation history and chemical composition as revealed by photometry and spectra. The Galaxy Zoo project ( has provided quantitative visual morphologies for over a million galaxies (including the entire Sloan Digital Sky Surveys, or SDSS Main Galaxy Sample), and has been part of a reinvigoration of interest in the morphologies of galaxies and what they reveal about the evolution of galaxies. Mapping Nearby Galaxies at Apache Point Observatory (MaNGA, part of SDSS-IV), is well over halfway through its 6 year plan to obtain spatially resolved spectral maps for 10,000 nearby galaxies (all of which have Galaxy Zoo morphologies). MaNGA is now by far the largest sample of resolved spectroscopy in the world, with over 6000 galaxies observed. The next data release from MaNGA will happen in December 2018. In this talk I will review these projects, and show results from them which demonstrate why a resolved view of the internal morphology in galaxies is interesting and how it provides a unique constraint of our understanding of galaxy evolution.
Host: TBD
Dec. 05 Roland Bacon (University of Lyon)
Title: The MUSE 3D View of the High Redshift Universe
Abstract: Thanks to its unique capabilities, the MUSE integral field spectrograph at ESO VLT has given us new insight of the Universe at high redshift. In this talk I will review some breakthrough in the observation of the Hubble Ultra Deep field with MUSE including the discovery of a new population of faint galaxies without HST counterpart in the UDF and the ubiquitous presence of extended Lyman-alpha haloes around galaxies.
Host: TBD
Dec. 12 Andrew Wetzel (University of California-Davis)
Title: Simulating the Milky Way and Its Satellites
Abstract: I will present the Latte suite of cosmological zoom-in baryonic simulations that model the formation of Milky Way-like galaxies at parsec-scale resolution, using the FIRE (Feedback in Realistic Environments) model for star formation and feedback. First I will discuss the formation of the Milky Way, including the origin of its thin+thick stellar disk morphology and new insights into the elemental abundances of its stellar populations. I also will present predictions for the oldest and most metal-poor stars in/around the Milky Way. The Latte simulations also self-consistently resolve the formation of satellite dwarf galaxies around each Milky Way-like host. While these low-mass galaxies have presented significant challenges to the cold dark matter model, I will show progress in addressing the "missing satellites" and "too-big-to-fail" problems. I also will present predictions for the orbital and star-formation histories of these satellites, and discuss a new long-term HST Treasury program to measure proper motions and star-formation histories for all known satellites of the Milky Way. Finally, I will discuss the synthetic Milky Way surveys that we have created from the Latte simulations, which are publicly available to provide theoretical modeling insight for the era of Gaia.
Host: TBD