Astronomy Colloquia at Caltech for 2018-19

Colloquia are held every Wednesday during the academic year at 4pm in the Cahill Hameetman auditorium.
Wine and cheese will be served in the Cahill Foyer from 5-5:30pm.

Month
Date
Speaker

Talk Title
OCTOBER
3

Speaker: David Charbonneau
Institute: Harvard
Host: D. Mawet

The Terrestrial Planets of Other Stars

For the next decade, the only opportunity to study the atmospheres of terrestrial exoplanets will be scrutinize these worlds when they transit nearby small stars. There are 417 mid-to-late M-dwarfs within 15 parsecs, yet we know surprisingly little about them, let alone their attendant planets. I will discuss recent findings from the MEarth Project and TESS Mission, which seek to discover the most spectroscopically accessible terrestrial exoplanets. Our recent discovery of a several rocky worlds transiting the nearby small star LHS1140 provides an unprecedented opportunity to detect the molecules present in the atmosphere of a terrestrial exoplanet. In our planetary quest, MEarth observations have sharpened our understanding of the evolution of these low-mass stars, and hence the stellar environment in which these planets may wither or thrive.

10

Speaker: Caroline Morley
Institute: UT Austin
Host: Eve Lee

From Exotic to Familiar: Observing Exoplanet Atmospheres in the Coming Decade

Observations of exoplanets to date have used the Hubble and Spitzer Space Telescopes to reveal exotic exoplanet atmospheres, including significant effort to characterize planets with radii between Earth's and Neptune's -for which we have no counterparts in the solar system-that are accessible to current telescopes. Observations of their transmission spectra reveal a diversity of worlds, some shrouded in clouds and others with molecular features. I will discuss the types of clouds and hazes that can obscure transmission spectra, and show the effect that these thick hazes have on the thermal emission of small exoplanets. I will discuss some of my plans for new observations during the first cycle of JWST to measure the thermal emission of these planets. The new frontier of exoplanet atmosphere studies is characterizing the atmospheres of planets more familiar to Earthlings: cold gas giants and temperate Earths. I will discuss my current work to reveal the atmosphere of a cold free-floating giant planet, and my plans for detecting a host of interesting molecules in its atmosphere with JWST. We will soon be able to access Earth-sized, temperate worlds for the most favorable 3 systems orbiting the small stars. I will discuss the recent discoveries of Earth-sized planets around bright M dwarfs and how we might use JWST to detect their atmospheres. Lastly, I will discuss prospects with current and upcoming ground-based telescopes to detect exoplanet atmospheres, including some steps to take preceding the launch of JWST.

17

Speaker:  J. Xavier Prochaska
Institute: UC Santa Cruz
Host: Chris Martin

The Wolfe Disk: ALMA Discoveries of Distant, HI-selected Galaxies

I will review our series of successful programs to dissect the interstellar medium of distant, star-forming galaxies with the Atacama Large Millimeter Array (ALMA).  In particular, I will discuss surveys of the set of HI-selected galaxies known as the damped Lya systems (DLAs).  We resolve, in part, a decades old struggle to identify the galactic counterparts of these DLAs and thereby place them firmly in the modern picture of galaxy formation.  I will also highlight high spectral and spatial resolution observations of the Wolfe Disk,a z~4 galaxy with a Milky Way-like rotation curve.

24
Speaker: Brad Cenko
Institute: NASA
Host: M. Kasliwal

Recent Observational Puzzles from Tidal Disruption Flares: Towards Viable Probes in the LSST Era

I will present an overview of efforts across the electromagnetic spectrum to identify and study tidal disruption flares (TDFs), when a star wanders too close to a super-massive black hole and is torn apart by tidal forces. In particular I will focus on three unexpected surprises that challenge the most basic picture of these events: 1) large inferred radii for the optical/UV-emitting material, indicating either circularization of the bound debris at large distances and/or significant reprocessing of the radiation from the inner accretion disk; 2) the ubiquity of outflows, detected at radio, X-ray, and UV wavelengths, ranging from speeds of 100 km/s to near the speed of light; and, 3) the peculiar atomic abundances observed in the UV and optical spectra of these objects. Understanding the nature of the broadband emission will be critical if we wish to ultimately utilize these events as probes of black hole mass in distant quiescent galaxies in the LSST era. Finally I will provide an introduction to upcoming and proposed wide-field surveys that will help us address these issues in the coming years.

31
Speaker: Jason Rhodes
Institute: JPL
Host: D. Mawet

NASA's Next Astrophysics Flagship: The Wide Field Infrared Survey Telescope (WFIRST)

The top recommendation for a large space mission in the US 2010 Decadal Survey was the Wide Field Infrared Survey Telescope (WFIRST).  Similarities in hardware requirements between proposed dark energy, exoplanet microlensing, and near infrared surveyor missions allowed for a single mission that would accomplish all three goals.  The gift of an existing 2.4 meter telescope to NASA by another US government agency allowed for the addition of a coronagraph that will take images and spectra of nearby exoplanets; this instrument will be a technological stepping stone to imaging other Earths in the 2030s.  I will give an overview of WFIRST's proposed instrumentation, science goals, and implementation plan. I will delve into the details of a number of scientific and technical efforts in Pasadena that are paving the way for this ambitious and exciting mission.


NOVEMBER
7
Speaker: Decker French
Institute:  Carnegie Observatories
Host: A. Faisst

Bold Nuclei in Old Galaxies

Galaxies evolving through the post-starburst (or E+A) phase are in the midst of drastic changes in their stellar populations, morphologies, and gas content. They are likely experiencing periods of AGN-driven feedback, alongside a high rate of tidal disruption events (TDEs), and are thus good laboratories to explore how these nuclear processes depend on and affect the rest of the galaxy. While post-starburst galaxies have stopped forming new stars, we have discovered that many have significant reservoirs of molecular gas remaining, which are depleted only after the starburst had already ended. Young post-starburst galaxies have molecular gas reservoirs similar to normal star-forming galaxies, which decline to the levels of early type galaxies within 1-2 Gyr. This rate of gas depletion is too rapid to be explained by the low star formation rates in these galaxies, so AGN feedback may be responsible. Recent ALMA observations show these galaxies have low dense gas fractions, and the mechanisms which deplete the gas after the starburst may be the same as those which suppress the collapse of gas into denser states. We have also found that post-starburst galaxies host a disproportionate number of TDEs, in which a star is accreted onto the black hole. I will present recent work on what the cause of the TDE rate enhancement during this phase may be and how this host galaxy preference can be used as a tool for identifying new TDEs.

14
Speaker: Tamas Budavari
Institute: John Hopkins Univ
Host: M. Graham

Computational Optics for Astronomy Surveys

We will discuss recent efforts to extract more information from time-domain imaging surveys. Our approach is to model the latent image behind the turbulent atmosphere which blurs all observations to varying degrees - making the stars twinkle. If we can infer the image of the sky behind the atmosphere, all observational studies will simultaneously benefit. Advanced statistical modeling and computational methodology promise reliable solutions. In simulations using the software stack of the Large Synoptic Survey Telescope, we study the subtle prism effect of the atmosphere which shifts sources around depending on their spectral energy distribution and the angle of the telescope's pointing. Expected improvements include not only subband color estimates within the broadband filters, but also better determination of sky coordinates and shape measurements, which ultimately yield better maps of the Universe.

28

Speaker: Ken Shen
Institute: Berkeley
Host: J. Fuller

A Revolution in Our Understanding of Type Ia Supernovae

Despite the wide-ranging role Type Ia supernovae (SNe Ia) play throughout astrophysics, we lack a firm theoretical understanding of how they arise.  For decades, the "single-degenerate" scenario, in which an accreting white dwarf reaches the Chandrasekhar mass, held sway.  However, spurred by recent observational and theoretical advances, researchers have begun exploring alternative progenitor channels.  In this talk, I will show why some of us were drawn to the "dynamically driven double-degenerate double-detonation" (D6) scenario, and how it makes unique predictions for surviving hypervelocity companions that were confirmed by the Gaia satellite earlier this year.  These stars, perhaps the fastest unbound stars in the Milky Way, represent the first ever detections of SN Ia survivors and have brought the D6 scenario to the forefront of the field as the only known SN Ia progenitor scenario to succeed in nature.

DECEMBER
5
Speaker: Jessie Christiansen
Institute: Caltech
Host: D. Mawet

Ten Thousand Pieces of Blue Sky: Building towards the complete picture of exoplanet demographics

The NASA Kepler mission has provided its final planet candidate catalogue, the K2 mission has contributed another four years’ worth of data, and the NASA TESS mission has just started producing planet candidates of its own. The demographics of the exoplanet systems probed by these transiting exoplanet missions are complemented by the demographics probed by other techniques, including radial velocity, microlensing, and direct imaging. I will walk through the progress of the Kepler occurrence rate calculations, including some of the outstanding issues that are being tackled. I will demonstrate how K2 and TESS are able to push the stellar parameter space in which we can explore occurrence rates beyond that examined by Kepler, and progress to that end. Finally, I will highlight some of the pieces of the larger demographics puzzle - occurrence rate results from the other techniques that probe different stellar and exoplanet regimes - and how we can start joining those pieces together.

12

Speaker: Smadar Naoz
Institute: UCLA
Host:  Jim Fuller

Mergers and Disruptions in Extreme Gravitational Potentials

Nuclear star clusters around supermassive black holes are likely the most collisional stellar systems in the Universe and are also embedded in extremely deep gravitational potential. Consequently, unique stellar dynamical processes and interactions are expected to take place. For example, collisions and mergers between stars and compact objects are likely to happen in this environment. I will explore these collisions and mergers and their product and will connect between them and some of the observed puzzles in galactic nuclei and in particular our own Galactic Center. Specifically, I will offer possible connections between those merger products and (1) the perplexing population of young stars that are isotropically distributed (S-stars) in a region that is hostile to star formation, (2)  the new class of cold stars in this same region that are two orders of magnitude larger than typical stars (e.g., the "gas-like cloud" G2), (3) stellar black hole-black hole binary mergers and LIGO observations, and (4) supermassive black-hole merger with a stellar-mass compact objects and future LISA observations. Recent developments in our understanding of the underlining physics of three- to few- body dynamics offer the opportunity to address puzzles at these extreme places in our Universe.

JANUARY 9

Speaker:
Institute:
Host:

No Colloquium - AAS week

16

Speaker: Jenny Greene
Institute:  Princeton
Host: P. Hopkins

Dwarf Galaxies and Their Black Holes

Because they are dark-matter dominated, dwarf galaxies provide some of
the most stringent tests of our cold dark matter model. We continue to
debate whether the number densities and distributions of low-mass
galaxies match theoretical expectations. I will describe how the advent 
of deep and wide-area surveys like the Hyper-Suprime Camera (HSC) Survey 
(and eventually LSST) are changing our ability to find and characterize 
low-mass, low surface-brightness populations. First, I will present a 
new calibration of surface-brightness fluctuations to the blue, which will 
provide a powerful new tool to determine satellite luminosity functions 
around nearby galaxies. Second, I will talk about our ongoing search for 
low-surface brightness galaxies is all environments with the HSC survey. 
Finally, if time permits, I will discuss the massive black hole populations 
in low-mass galaxies.

23

Speaker: Alex Szalay
Institute: John Hopkins
Host: G. Djorgovski

The Era of Surveys and the Fifth Paradigm of Science

Starting with the Sloan Digital Sky Survey and the Hubble Deep Field, astronomy has entered the Era of Surveys. Today we have covered a substantial fraction of the sky in multiple wavelengths. Much of this data is now available on-line, as an easy-to-use virtual telescope. The data sets are interoperable and it is easy to cross-correlate between surveys. Astronomers became proficient in databases, and today they use these not as tools but rather like musical instruments. Over the centuries science has gone through several paradigms, starting with the "empirical", followed by "theoretical" and "computational" approaches to science. Today, the large surveys have led us to the so-called Fourth Paradigm of Science, where discoveries are "data-driven". Astronomers were early adopters, as we can only observe the sky, but cannot undertake experiments which change the behavior of celestial objects. This data-intensive approach to astronomy has resulted in disruptive changes, both technological and sociological. This talk will discuss the journey over the last 20 years, and where these changes have led us, and what may lie ahead. The Large Synoptic Survey Telescope, LSST, will open up the time domain and will produce the largest dataset astronomers will encounter. Such data sets will bring new challenges, as systematic errors will increasingly dominate over statistical noise. We already see how machine learning is turning new detections into discoveries. But the most interesting changes are still ahead: just as in self-driving cars, algorithms are making the decisions, and soon we will see AI tools setting adaptive choices about survey strategies, like target selection. This may be the beginning of the Fifth Paradigm of Science, where computers decide objectively which experiments will yield the biggest gain in our knowledge. Finally, I will also discuss structural and organizational changes that should happen, to make sure that legacy data sets, which have cost hundreds of millions to acquire, can be safely preserved and analyzed throughout their useful lifetime. This will require a fresh look at long term data curation - how to be FAIR (Findable, Accessible, Interoperable, Reusable) and how to be open, free and sustainable, all at the same time.

30

Speaker: Yanqin Wu
Institute: Univ of Toronto
Host: Eve Lee

A uniform population of planets

A large number of close-in super-Earths have now been discovered.
How they form, and how they relate to other classes of planets, remain 
unsolved. In this talk, I will discuss recent progress regarding their 
masses, their composition, and their companion planets, leading to the 
conclusion that super-Earths make up  a surprisingly uniform population.
This uniformity is unpredicted, and brings new insights to the theory of 
planet formation. As an aside, the census also indicates that planetary 
systems like our  own, with low-mass terrestrials inside and cold giants 
outside, are likely rare in the Milky Way.

FEBRUARY
6

Speaker: Suvi Gezari
Institute: Univ of Maryland
Host: M. Graham

A Systematic Exploration of Extragalactic Nuclear Transients with the Zwicky Transient Facility

The Zwicky Transient Facility (ZTF) is performing a multi-band optical time domain survey of the entire Northern Sky that is enabling a comprehensive study of transients associated with supermassive black holes in the nuclei of galaxies.  I will present exciting results from our systematic selection, classification, and multiwavelength characterization of nuclear transients in the first year of the ZTF alert stream, including the discovery of tidal disruption events (TDEs), changing-look active galactic nuclei (CLAGN), and candidate recoiling supermassive black holes (rSMBHs).  Our nearly complete classification of bright (r < 19 mag) nuclear transients in the ZTF survey with the Palomar 60in SEDM low-resolution spectrograph will provide an excellent training set for optimizing photometric selection of TDEs in the LSST era.  Indeed, I will conclude with strong recommendations for the LSST Wide-Fast Deep Survey cadence based on our ZTF discoveries so far.

13

Speaker: Sandro Tacchella
Institute: Harvard
Host: A. Faisst

Building quiescent galaxies

Today's galaxy population shows a large structural diversity that depends on stellar mass, star-formation activity, and environment. Even quiescent galaxies that have little star formation display a large range of morphological properties, indicating several different formation mechanisms at work. The peak of cosmic star formation rate density at redshifts of 1 to 3 is thought to be the epoch of the major buildup of these massive spheroids. By combining ground-based SINFONI integral-field unit observations with Hubble Space Telescope imaging data, I will show how these early galaxies grow on spatially resolved scales, and how they transition to the quiescent population. In particular, I will discuss the connection (or lack thereof) between quenching and morphological transformation. Furthermore, I will highlight how such galaxies grow in a self-regulated equilibrium and thereby building up their central bulge component. I will show the importance of understanding the variability of the star formation rate on different timescales to constrain numerical simulation. Finally, I will end by an outlook of the key questions that we can achieve with the next generation of telescope such as the James Webb Space Telescope and the 30m-class telescopes.

20

Speaker: Eliot Quataert
Institute: UC Berkeley
Host: M. Kasliwal

What Happens When a Massive Star Fails (Sort of) to Explode?

There are observational and theoretical reasons to suspect that up to 10s of percent of massive stars that undergo core-collapse at the end of their lives fail to explode in a canonical energetic supernova explosion.    In this talk I will describe what transpires in such nominally failed supernovae and how they may manifest themselves observationally in time-domain surveys.

27

Speaker: Felix Aharonian
Institute: MPIK, Germany
Host: Gregg Hallinan


Title: Cosmic Ray PeVatrons in the Milky Way


For decades,  supernova remnants have been considered as the principal contributors to the galactic cosmic rays up to the so-called knee around 1 PeV (10^15 eV).   However, the recent observations and t
heoretical studies raised doubts inside the CR community regarding the ability of SNRs to operate as PeVatrons.  Supernova remnants remain major cosmic ray factories in the Milky Way, but presumably with a reduced role at highest energies.  On the other hand,  multi-TeV gamma-ray observations provide evidence that the clusters of young massive stars do host
proton PeVatrons.  In the context of the origin of highest energy galactic cosmic rays, the role of the supermassive black hole in the galactic center could be significant as well.

 


MARCH
6

Speaker: Ariel Goobar
Institute: Stockholm University
Host: M. Kasliwal

Title: Gravitationally Lensed Supernovae

 

Although discussed in the literature for many decades, gravitational lensing of supernovae has only recently become observationally feasible. Massive galaxy clusters used as nature’s own telescopes provide the amplifying power that allows us to find fainter and more distant supernovae, beyond reach of unaided man-made facilities.

We have also started to find multiply imaged strongly lensed supernovae, potentially a useful technique to provide accurate measurements of the expansion rate of the universe. Strongly lensed supernovae probe smaller angular scales than most other strongly lensed systems known to date, while still detectable without the need for high spatial-resolution imaging. Wide-field time domain surveys like ZTF and LSST, as well as the next generation of space instruments, make the prospects very exciting. 

13

Speaker: Maxwell Moe
Institute:Univ of Arizona, Tucson
Host: J. Fuller

Title: The Formation of Close Binary Stars and Planets

Abstract: The formation and orbital migration of close binaries and hot Jupiters remain a mystery.  The majority of very close binaries have outer tertiary companions, suggesting Kozai-Lidov oscillations coupled with tidal friction play an important role in their dynamical evolution.  However, close pre-main-sequence binaries are ubiquitous, indicating most close binaries migrated within a few Myr while there was still dissipative gas in the primordial disk.  I will overview a new population synthesis model that incorporates more realistic initial conditions and a novel tidal mechanism to explain the formation of close binaries and hot Jupiters during the pre-main-sequence phase. Although planets may favor metal-rich hosts, recent observations demonstrate the close binary fraction dramatically increases toward lower metallicities. I will discuss five different observational techniques that corroborate this metallicity trend, and will outline a fragmentation model that reproduces the observations.  I will conclude by highlighting how close binaries suppress the formation of close (S-type) planets. Close binaries therefore substantially bias planet occurrence rates and the inferred trends with respect to host mass and metallicity.

20

Speaker: Matthew Povich
Institute: Cal Poly Pomona
Host: Eve Lee

Title:    The Balance of Power in Galactic Massive Star-Forming Regions

The star formation rate (SFR) is a fundamental parameter in theoretical models of galaxy evolution and governs the observed properties of galaxies. The most widely-used empirical measurements of the SFR in both the Milky Way and external galaxies rely on indirect observational tracers sensitive to only the most massive 1% of stars. Hence state-of-the-art astrophysical methods for diagnosing galactic star-formation activity are analogous to using only the tax returns and investment portfolios of the richest 1% of earners to diagnose U.S. economic activity.

I will present recent work to model the 3.6 micron through 10 mm spectral energy distributions (SEDs) for a sample of 28 young Galactic massive star-forming regions. We performed large-aperture photometry on archival imaging data obtained using an armada of space-based observatories: Spitzer, MSX, IRAS, Herschel, and Planck and fit the resulting SEDs with multicomponent dust, blackbody, and power-law continuum models. Because the massive stellar content in the majority of these regions has been spectroscopically cataloged, we balance the "energy budgets" in each region by comparing the luminosity input by stars to that emerging in the SEDs. We find that ∼34% of Lyman continuum photons emitted by massive stars are absorbed by dust before contributing to the ionization of H II regions, while ∼68% of the stellar bolometric luminosity is absorbed and reprocessed by dust in the H II regions and surrounding photodissociation regions. We calibrate infrared and radio diagnostics of obscured SFRs to the known ionizing stellar populations. Widely-employed extragalactic SFR calibrations based on 24 micron luminosity agree with our calibrations to within 30%, while analogous extragalactic calibrations based on 70 micron luminosity must be corrected for the smaller physical size of individual Galactic regions.

I will also discuss plans to map the SFR distribution in our home Galaxy by applying our new SFR calibrations to 2600 Galactic star-forming regions cataloged by Zooniverse citizen scientists for the Milky Way Project (www.milkywayproject.org).

27

Speaker:
Institute:
Host:

No Colloquium - Spring Break

APRIL
3

Speaker: Boris Gaensicke
Institute: Univ of Warwick
Host: Tom Prince

Kingsley

Title: Evolved planetary systems around white dwarfs
 
Many of the known planets - in the solar system Mars and beyond - will survive the post main-sequence evolution of their host stars into white dwarfs. Later interactions  scatter asteroids, moons, and possibly entire planets deep into the gravitational potential of the white dwarf, where they are disrupted, and eventually accreted.  I will review the rich observational evidence for evolved planetary systems at white dwarfs, and discuss how the study of these systems can inform us on the conditions and the efficiency of planet formation, and on the architectures of outer planetary systems inaccessible to direct detection.

10

Speaker: Jocelyn Bell Burnell
Institute: Oxford University
Host: Mansi Kasliwal

Greenstein

Title:  The Discovery of Pulsars - A Graduate Student's Story

In this lecture, I will describe how the accidental discovery of pulsars happened and reflect on the factors that contributed to it.


17

Speaker: Dale Frail
Institute: NRAO Socorro
Host: George Djorgovski

Biard

Title:  Sky Surveys and the Dawn of Synoptic Radio Astronomy

Radio astronomy has traditionally lagged behind the abilities of infrared, optical and X-ray for surveying the sky. Recent technological advances are changing this, and we are posed for a new generation of radio surveys. I will begin by talking about the evolving capabilities of radio telescopes and the technical challenges that must be overcome to carrying out large surveys. I will illustrate these challenges by describing the recent GMRT radio continuum survey (TGSS ADR) in which 90% of the sky was surveyed at a frequency of 150 MHz. Some of the science resulting from this survey will be discussed, including image-based searches for pulsars that target Fermi unassociated gamma-ray sources, the galactic plane, and the gamma-ray excess toward the galactic center. I will end the talk with a discussion of some on-going sky surveys which are designed to address the customary topics in cosmology and extragalactic source populations, but also include new applications including exploration of the time-domain and the magnetic universe.

24

Speaker: Adam Burrows
Institute: Princeton
Host: M. Kasliwal

Title:  Three-Dimensional Supernova Explosion Simulations

Using our state-of-the-art code Fornax we have simulated the collapse and  explosion of the cores of many massive-star models in three spatial dimensions. This is the most comprehensive set of realistic 3D core-collapse supernova simulations yet performed and has provided very important insights into the mechanism and character of this 50-year-old astrophysical puzzle.  Most of our 3D models explode naturally and understandably, given detailed initial model progenitors inherited from others. I will present results from this suite of runs and the novel conclusions derived from our new capacity to simulate many 3D, as opposed to 2D and 1D, full physics models every year.  The results collectively
suggest that the qualitative resolution of this recalcitrant, multi-decade, enigma may be within sight.

MAY
1

Speaker: Phil Hopkins
Institute: Caltech
Host: Mansi Kasliwal

Title:  Cosmic "Dust" (Galaxies, Stars, and Actual Dust)!

In this talk, I'll begin by giving a broad overview of the recent work by the students and postdocs in our group on star and galaxy formation. The most fundamental unsolved problems in these fields all revolve around "feedback" from stars and black holes, which new generations of theoretical models and simulations are now able to incorporate with increasing predictive power. I'll briefly mention some highlights showing the progress on a number of outstanding mysteries about the nature of dark matter on small scales, and the origins of "universal" properties of stars and galaxies. In the second half of the talk, I'll describe a couple projects in detail exploring a newly-discovered class of instabilities which exist in any system containing dust and gas. These instabilities come in an infinite variety of "flavors" and can have remarkably diverse outcomes. I'll discuss how this may fundamentally change our understanding of dust growth and evolution in the ISM, wind-launching in cool stars and AGN, HII regions, and (of course) planet formation.


8

Speaker:  Laura Sales
Institute: UC Riverside
Host: Andreas Faisst

Title:  Dwarf Galaxies and Their Dark Matter Content

Dwarf galaxies are the most numerous type of galaxies in the Universe and largely fascinating objects in their own right. Believed to be the most dark matter dominated objects within the LCDM model, dwarf galaxies pose the most significant challenges to our cosmological scenario. Feedback, star formation, reionization and environment are all believed responsible, to a large extent, for the variations in their observed properties. I will present some of our results using hydrodynamical simulations to study dwarf galaxies in different environments. Using the Illustris simulations we explore high densities regions such as the Virgo cluster and make predictions for the tidal interactions in dwarfs, their dark matter and globular cluster content and the formation of ultra-diffuse dwarfs (UDGs). We transition to isolated dwarfs using the FIRE simulations to make predictions on their interactions with faint satellite companions, being a channel to constraint the Large Magellanic Cloud and their population of associated ultra-faint dwarfs based on the latest GAIA DR2 results. 


15

Speaker: Melissa Ness
Institute: Columbia University
Host: Jim Fuller

Title:  In (Data-Driven) Pursuit of Galactic Archaeology

We are entering an era where the current difficulties in building an understanding of the formation and evolution of our Galaxy can be overcome. Using new data-driven approaches to spectroscopy, we have derived ages and precision chemical abundances for millions of stars across the Galaxy. With new methodologies to derive information from spectra, across a multitude of surveys, combined with the distance and stellar motion measurements being delivered by the Gaia mission, we are constructing the ultimate synthesis of Galactic information. I will showcase the information that we have derived from stars across the Galaxy, how we have derived this information, and what this is telling us about the Milky Way's formation. In particular I will highlight recent work that strongly constrains the formation of the Milky Way disk and demonstrates the (dire) prospects for chemical tagging of the Milky Way.


22

Speaker: Ignas Snellen
Institute: Leiden Observatory
Host: Dimitri Mawet

Title:  Exoplanets and the Search for Extraterrestrial Life

In this talk I will review the state-of-the-art work on exoplanet characterization, mainly focusing on ground-based techniques. I will discuss what we do now, can do in the near future with upcoming instruments, and later with the Extremely Large Telescopes. Detailed knowledge of the chemical composition and climate
of Earth-like planets such as Proxima b and the seven TRAPPIST sisters are within reach.

29

Speaker: Andrew MacFadyen
Institute: New York University
Host: Jim Fuller

Title:  Simulations of Electromagnetic Counterparts to Gravitational Wave Sources


I will present recent numerical simulations of the dynamics and observational signatures of gas flows from gravitational wave sources.   
I will show that cosmological short GRBs share the same outflow structure with binary neutron star merger GW170817 in the afterglow stage: an ultra-relativistic structured jet, and that the exceptional properties of the GW170817 afterglow can be explained by the difference in observation angle alone. I will then show that the light curves of the GW170817 afterglow, if viewed on-axis, are consistent with those of cosmological short GRBs. As time allows, I will also discuss recent results from simulations of binary black hole accretion.



JUN
5

Speaker: Sean Andrews
Institute: CfA Harvard
Host: Eve Lee

Title:  Observing Planet Formation

Planetary systems form in the disks of gas and dust that orbit young stars. In the past few years, very high angular resolution observations of disks in nearby star-forming regions have started to uncover some key signatures of the planet formation epoch. This talk will focus on what we are learning about the distribution of disk material on spatial scales of only a few astronomical units, largely based on state-of-the-art measurements with the Atacama Large Millimeter/submillimeter Array (ALMA), and the corresponding implications for the assembly and early evolution of planetary systems.
 


12

Speaker: France Cordova
Institute: NSF
Host: George Djorgovski

Neugebauer Lecture

Title:  Thinking Big

In this talk I will first reflect on the legacy of Gerry Neugebauer.  I will then talk about where NSF is now with its strategic framework, called "NSF's 10 Big Ideas."  Finally, I will talk about the nature, value, and benefits of public service from a personal viewpoint.

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