KICP Seminars & Colloquia
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KICP Seminars & Colloquia, Spring 2015
Seminar schedule for Spring 2015April 1, 2015
Astronomy Colloquium | Kendrick Smith
Perimeter Institute | Primordial non-Gaussianity in the CMB and Large-Scale Structure [Abstract] | April 3, 2015
Friday noon seminar | Laura Newburgh
Dunlap Institute, University of Toronto | Measuring Dark Energy with CHIME [Abstract] | April 8, 2015
Wednesday colloquium | John M Kovac
Harvard University | Measurements of B-mode Polarization at Degree Angular Scales with the BICEP / Keck Experiments [Abstract] | April 15, 2015
Astronomy Colloquium | Daniel Green
University of Toronto | Probing the Nature of Inflation [Abstract] | April 17, 2015
Friday noon seminar | Silvia Galli
The University of Chicago | Cosmological results from Planck 2015 [Abstract] | April 21, 2015
Astronomy Special Seminar | Richard de Grijs
Kavli Institute for Astronomy and Astrophysics, Peking University, China | Not-so-simple stellar populations in nearby, resolved massive star clusters [Abstract] | April 22, 2015
Wednesday colloquium | Maura McLaughlin
West Virginia University | A Galactic Scale Gravitational Wave Observatory [Abstract | PDF] | April 24, 2015
Friday noon seminar | Eugene Churazov
Max Planck Institute for Astrophysics | Gamma-rays from type Ia supernova SN2014J [Abstract] | April 28, 2015
Open Group seminar | Andrew Long
Arizona State University | Particle Production from Cosmic Strings [Abstract] | April 29, 2015
Astronomy Colloquium | Andrew MacFadyen
New York University | Binary Black Hole Accretion [Abstract] | May 1, 2015
Friday noon seminar | Rachel A Rosen
Columbia University | Partially Massless Charges and Monopoles [Abstract] | May 4, 2015
Open Group seminar | Michele Vallisneri
Jet Propulsion Laboratory | Searching for gravitational waves with pulsar-timing arrays [Abstract] | May 6, 2015
Wednesday colloquium | Keith Bechtol
WIPAC / University of Wisconsin-Madison | News on the search for Milky Way satellite galaxies [Abstract | PDF] | May 8, 2015
Friday noon seminar | Cora Dvorkin
Harvard University | Probing New Physics Beyond the Standard Model with Cosmology [Abstract] | May 13, 2015
Astronomy Colloquium | Piero Madau
University of California Observatories | The Dark and Light Side of Galaxy Formation [Abstract] | May 15, 2015
Friday noon seminar | Alyson Brooks
Rutgers University | Re-Examining Astrophysical Constraints on the Dark Matter Model [Abstract] | May 20, 2015
Wednesday colloquium | Lisa Randall
Harvard | Double Disk Dark Matter [Abstract] | May 22, 2015
Friday noon seminar | Sean McWilliams
West Virginia University | Probing the environments of supermassive black-hole binaries with pulsar timing arrays [Abstract] | May 27, 2015
Open Group seminar | Carlos S Frenk
Durham University | Looking for the identity of the dark matter in and around the Milky Way [Abstract] | May 27, 2015
Astronomy Colloquium | Edo Berger
Harvard University | Short-Duration Gamma-Ray Bursts and the Electromagnetic Counterparts of Gravitational Wave Sources [Abstract] | May 29, 2015
Friday noon seminar | Simone Ferraro
Princeton University | Cosmic Flows: cosmology and astrophysics from galaxy velocities [Abstract] | June 5, 2015
Special seminar | Edward Stone
Caltech | The Voyager Odyssey [Abstract] | June 5, 2015
Astronomy Special Seminar | Edward Stone
Caltech | The Voyager Odyssey [Abstract] | June 10, 2015
Astronomy Colloquium | Josh Winn
MIT | The shortest-period planets [Abstract] |
COLLOQUIA - April 1, 2015 | 3:00 PM | BSLC 115 | Astronomy Colloquium
Primordial non-Gaussianity in the CMB and Large-Scale Structure
Kendrick Smith, Perimeter Institute
I'll give a pedagogical review of inflation and explain how its physics can be constrained by searching for "primordial non-Gaussianity", i.e. differences between the statistics of the initial curvature field in our universe and the statistics of an ideal Gaussian field. Then I'll talk about observational CMB constraints, including some new results from Planck. Finally I'll discuss future prospects for improving Planck constraints with large-scale surveys such as Euclid and LSST. - April 8, 2015 | 3:00 PM | BSLC 115 | Wednesday colloquium
Measurements of B-mode Polarization at Degree Angular Scales with the BICEP / Keck Experiments
John M Kovac, Harvard University
The theory of cosmic inflation postulates that the initial conditions of our observable universe arose from quantum fluctuations during a very early burst of exponential expansion. The BICEP / Keck Array experiments are a series of cosmic microwave background (CMB) polarimeters specifically designed to search for gravitational waves predicted by inflation by looking for the faint B-mode patterns they would imprint on degree-scale CMB polarization. Observing from the South Pole between 2010 and 2012, the BICEP2 telescope made maps of unprecedented sensitivity at degree angular scales over 2% of the sky, In March 2014 the BICEP2 team reported a high signal-to-noise detection of B-mode polarization at 150 GHz, at a level well above typical predictions of galactic foreground models for that region of sky, and consistent with a large contribution from inflationary gravitational waves. However, later last year high-frequency results reported by the Planck satellite indicated levels of polarized emission from galactic dust potentially high enough to account for the entire BICEP2 signal. In a recently published joint analysis that combines data from BICEP2, the Keck Array, and the Planck satellite, we find that there is not currently significant evidence for a gravitational wave signal, and we set the tightest constraints yet on its possible level. I will describe our current results and the continuing hunt for inflationary gravitational waves with the BICEP / Keck Array experimental program. - April 15, 2015 | 3:00 PM | BSLC 115 | Astronomy Colloquium
Probing the Nature of Inflation
Daniel Green, University of Toronto
The idea that the early universe included an era of accelerated expansion (Inflation) was proposed to explain very qualitative features of the first cosmological observations. Since then, our observations have improved dramatically and have lead to high precision agreement with the predictions of the first models of inflation, slow-roll inflation. At the same time, there has been significant growth in the number of mechanisms for inflation, many of which are qualitatively distinct from slow-roll.
Nevertheless, most of these ideas are also consistent with current data. In this talk, I will first review inflation and its current observational status. I will then discuss the important theoretical targets for the future and the prospects for achieving them. - April 22, 2015 | 3:00 PM | BSLC 115 | Wednesday colloquium
A Galactic Scale Gravitational Wave Observatory
Maura McLaughlin, West Virginia University
PDF
Pulsars are rapidly rotating neutron stars with phenomenal rotational stability that can be used as celestial clocks in a variety of fundamental physics experiments. One of these experiments involves using an array of precisely timed millisecond pulsars to detect perturbations due to gravitational waves. The gravitational waves detectable through pulsar timing will most likely result from an ensemble of supermassive black hole binaries. I will describe the efforts of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), a collaboration which monitors an array of over 40 millisecond pulsars with the Green Bank Telescope and Arecibo Observatory. The most recent limits on various types of gravitational wave sources will be presented, and I will show how these limits are already constraining models for galaxy formation and evolution and the tension of cosmic strings. I will then describe the dramatic gains in sensitivity that are expected from discoveries of millisecond pulsars, more sensitive instrumentation, improved detection algorithms, and international collaboration and show that detection is possible before the end of the decade. - April 29, 2015 | 3:00 PM | BSLC 115 | Astronomy Colloquium
Binary Black Hole Accretion
Andrew MacFadyen, New York University
Binary black hole mergers in the presence of gaseous accretion flows are prime candidates for simultaneous observations of both gravitational waves and electromagnetic signals. I will present the results of 2D hydrodynamical simulations of circumbinary disk accretion using the moving-mesh code DISCO. These simulations demonstrate that gas accretion is not impeded by binarity. Gas is efficiently stripped from the inner edge of the circumbinary disk and enters the cavity along accretion streams, which feed persistent “mini-disks” surrounding each black hole. I will discuss characteristic periodicity in the measured accretion rate onto each BH, with implications for the quasar PG 1302-102 which shows evidence for periodic variability, as well as the dependence of the accretion flow on the binary mass ratio. I will also discuss characteristic modifications to the spectrum which arise from shock heated gas inside the circumbinary cavity. Finally, I will discuss simulations which include binary inspiral and merger due to gravitational wave emission in order to track the changes in accretion and electromagnetic radiation as the orbit shrinks. - May 6, 2015 | 3:00 PM | BSLC 115 | Wednesday colloquium
News on the search for Milky Way satellite galaxies
Keith Bechtol, WIPAC / University of Wisconsin-Madison
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The population of Milky Way satellite galaxies includes the least luminous, least chemically evolved, and most dark matter dominated galaxies in the known universe. These extreme objects have reshaped how we define a "galaxy" and provide a unique testing ground for both galaxy formation models and the cold dark matter paradigm. The current census of satellite galaxies surrounding the Milky Way is almost certainly incomplete. Ongoing and near-future wide-field optical imaging surveys are anticipated to find hundreds of ultra-faint Milky Way companions at lower luminosities, greater distances, and in less explored regions of the sky. A dozen new stellar systems have already been reported in 2015, and at least one these, Reticulum II, has now been dynamically and chemically confirmed as a galaxy. I will place these recent results in context and discuss how the emergent population of Milky Way satellites might enhance the sensitivity of indirect dark matter searches. - May 13, 2015 | 3:00 PM | BSLC 115 | Astronomy Colloquium
The Dark and Light Side of Galaxy Formation
Piero Madau, University of California Observatories
In recent years, precision measurements across cosmic time have led to a widely accepted cosmological paradigm for galaxy assembly and evolution, the cold dark matter (ΛCDM) model. Within this theory, galaxies form "bottom-up," with low-mass objects ("halos") collapsing earlier and merging to form larger and larger systems over time. Ordinary matter follows the dynamics dictated by the dominant dark matter until radiative, hydrodynamic, and star-formation processes take over. Although ΛCDM has had great success in explaining the observed large-scale distribution of mass in the universe, the nature of the dark matter particle is best tested on small scales, where its physical characteristics manifest themselves by modifying the structure of galaxy halos and their lumpiness. It is on these scale that detailed comparisons between observations and theory have revealed several discrepancies and challenged our understanding of the mapping between dark matter halos and their baryonic components. In this talk I will review some of the triumphs and tribulations of the theory. While the latter may indicate the need for more complex physics in the dark sector itself, emerging evidence suggests that a poor understanding of the baryonic processes involved in galaxy formation may be at the origin of these controversies. - May 20, 2015 | 3:00 PM | BSLC 109 | Wednesday colloquium
Double Disk Dark Matter
Lisa Randall, Harvard
Lisa Randall
Frank B. Baird, Jr., Professor of Science, Harvard University
Photo credit: Tsar Fodorsky. I will describe Partially Interacting Dark Matter and a possible consequence, Double Disk Dark Matter in which a dark matter disk is embedded in the baryonic disk. I will discuss possible implications and observational consequences and constraints, including implications for the satellites of the Andromeda Galaxy. - May 27, 2015 | 3:00 PM | BSLC 115 | Astronomy Colloquium
Short-Duration Gamma-Ray Bursts and the Electromagnetic Counterparts of Gravitational Wave Sources
Edo Berger, Harvard University
Gamma-ray bursts are the most luminous and energetic explosions known in the universe. They appear in two varieties: long- and short- duration. The long GRBs result from the core-collapse of massive stars, but until recently the origin of the short GRBs was shrouded in mystery. In this talk I will present several lines of evidence that point to the merger of compact objects binaries (NS-NS and/or NS-BH) as the progenitor systems of short GRBs. Within this framework, the observational data allow us to determine the merger rate of these systems as input to Advanced LIGO, to infer the electromagnetic properties of gravitational wave sources, and to study r-process nucleosynthesis. - June 10, 2015 | 3:00 PM | BSLC 115 | Astronomy Colloquium
The shortest-period planets
Josh Winn, MIT
Short-period planets were a gift from nature that enabled the rapid acceleration of exoplanetary science. They are more readily studied than long-period planets, and their existence and orbital properties pose interesting questions. I will present the results of a search for the shortest-period transiting planets, using data from the Kepler spacecraft. The results show that 0.5% of Sun-like stars have orbiting "lava worlds": terrestrial planets with periods ranging from 4 hours to one day. The search also revealed a new class of objects that seem to be small rocky planets disintegrating in the blazing heat from their parent stars. Finally, I will describe an upcoming NASA mission, the Transiting Exoplanet Survey Satellite (TESS), which will identify thousands of short-period planets around the nearest and brightest stars in the sky.
FRIDAY NOON SEMINARS - April 3, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Measuring Dark Energy with CHIME
Laura Newburgh, Dunlap Institute, University of Toronto
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a new radio transit interferometer currently being built at the Dominion Radio Astrophysical Observatory (DRAO) in Penticton, BC, Canada. We will use the 21cm emission line of neutral hydrogen to map baryon acoustic oscillations between 400-800MHz across 3/4 of the sky. These measurements will yield sensitive constraints on the dark energy equation of state between redshifts 0.8 -- 2.5, a fascinating but poorly probed era corresponding to when dark energy began to impact the expansion history of the Universe. I will describe the CHIME instrument, the analysis challenges, the calibration requirements, and current status. - April 17, 2015 | 12:00 PM | LASR Conference Room | Friday noon seminar
Cosmological results from Planck 2015
Silvia Galli, The University of Chicago
Planck is an ESA satellite aimed at the observation of the Cosmic Microwave Background. In 2013, the Planck collaboration has released the first results on cosmology based on temperature only data from ~15 months of observations. This year, we released the second round of cosmological results based on full mission data (~30+ months) both in temperature and, for the first time, in polarization. In this talk, I will review a few of the main cosmological results of this year release, showing the main changes with respect to the 2013 release. I will highlight the power of polarization data and show a few cases where polarization allows us to set spectacular constraints on possible extentions of the LCDM model. - April 24, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Gamma-rays from type Ia supernova SN2014J
Eugene Churazov, Max Planck Institute for Astrophysics
SN2014J is the closest type Ia supernova in the era of space observatories and the first
one from which gamma-ray lines have been detected with high significance. The flux of
Co-56 lines at 847 and 1238 keV, observed with INTEGRAL, shows that about 0.6 Msun
of radioactive Ni-56 has been synthesized during explosion. The line broadening
suggests the characteristic expansion velocity of ~10000 km/s. Annihilation of positrons
produced during decay of Co-56 makes significant contribution to the continuum below
511 keV. The total mass of the ejecta is consistent with 1.4 Msun progenitor, although
the constraints are not very tight. Overall the gamma-ray data are broadly consistent
with the expectations for canonical 1D models, such as delayed detonation or
deflagration models for a near-Chandrasekhar mass White Dwarf. Pure detonation
models or strongly sub-Chandrasekhar models are excluded by the gamma-ray data. - May 1, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Partially Massless Charges and Monopoles
Rachel A Rosen, Columbia University
In this talk I'll discuss an exotic theory of gravity known as "partially massless" gravity. The linear partially massless theory displays many features analogous to those of electromagnetism, including an electric/magnetic duality. However, the structure of gauge charges is much richer than in E&M. I'll present the analogues of electric point charges and Dirac monopoles and discuss possible applications. - May 8, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Probing New Physics Beyond the Standard Model with Cosmology
Cora Dvorkin, Harvard University
Cosmological observations have provided us with answers to age-old questions, involving the age, geometry, and composition of the universe. However, there are profound questions that still remain unanswered.
In this talk, I will describe ongoing efforts to shed light on some of these questions.
The origin of the small anisotropies that later grew into the stars and galaxies that we see today is still unknown.
In the first part of this talk, I will explain how we can use measurements of the CMB and the large-scale structure of the universe to reconstruct the detailed physics of very early epochs, when the universe was only a tiny fraction of a second old.
In the last part of the talk, I will discuss how we can use observations of the CMB and the large-scale structure of the universe to improve our understanding of another open question in fundamental physics. Cosmological observations and galaxy dynamics seem to imply that 84% of all matter in the universe is composed of dark matter, which is not accounted for by the Standard Model of particles. The particle nature of dark matter is one of the most intriguing puzzles of our time. I will identify cosmological processes in which the particle interactions of dark matter are of relevance and show how we can use current and future cosmological data to probe these interactions both at large and small scales. - May 15, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Re-Examining Astrophysical Constraints on the Dark Matter Model
Alyson Brooks, Rutgers University
The cosmological model based on cold dark matter (CDM) and dark energy has been hugely successful in describing the observed evolution and large scale structure of our Universe. However, at small scales (in the smallest galaxies and at the centers of larger galaxies), a number of observations seem to conflict with the predictions CDM cosmology, leading to recent interest in Warm DarkMatter (WDM) and Self-Interacting Dark Matter (SIDM) models. These small scales, though, are also regions dominated by the influence of baryons. I will present results from high resolution cosmological galaxy simulations that include both baryons and dark matter to show that baryonic physics can significantly alter the dark matter structure and substructure of galaxies, revolutionizing our expectations for galaxy structure and influencing our interpretation of the Dark Matter model. - May 22, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Probing the environments of supermassive black-hole binaries with pulsar timing arrays
Sean McWilliams, West Virginia University
While pulsar timing arrays (PTAs) like NANOGrav have not yet detected gravitational waves, they are still giving us useful information about supermassive black-hole binaries in our Universe. In particular, the continuing non-detection of gravitational waves at current sensitivity levels already suggests that dynamical effects other than gravitational-wave emission are either much more or else much less efficient than we previously thought. I will present detailed calculations of the influence of these other effects on the gravitational-wave signal that we hope to detect with PTAs. I will also present results using the actual 9-year data set from NANOGrav that show how models that include effects other than gravitational-wave emission are already favored over models that only include gravitational-wave emission. Finally, I will present results using realistic simulated PTA data that show what conclusions we will be able to draw regarding the environments and the dynamics of supermassive black-hole binaries at ~milliparsec separations over the next several years. - May 29, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Cosmic Flows: cosmology and astrophysics from galaxy velocities
Simone Ferraro, Princeton University
Velocity fields are a powerful probe of structure formation and the energy content of our Universe. Additionally, the motion of ionized gas on intermediate scales can be used to measure the clustering of baryons and shed light on galaxy formation and feedback mechanisms. I will discuss techniques that can be used to both constrain cosmology and measure baryon properties. I will also present some preliminary results.
SPECIAL SEMINARS - June 5, 2015 | 1:30 PM | KPTC 106 | Special seminar
The Voyager Odyssey
Edward Stone, Caltech
Launched in 1977 to explore Jupiter, Saturn, Uranus, and Neptune, the two Voyager spacecraft continued their journeys beyond the planets as they searched for the edge of heliosphere, the boundary between the solar wind the local interstellar medium. After a thirty-five year journey taking it eighteen billion kilometers from the sun, Voyager 1 became the first human-made object to enter interstellar space. In the next several years Voyager 2 will likely join Voyager 1 in exploring the local interstellar medium and its interaction with the heliosphere.
OPEN GROUP SEMINARS - April 28, 2015 | 1:30 PM | LASR Conference Room | Open Group seminar
Particle Production from Cosmic Strings
Andrew Long, Arizona State University
How can we determine if the universe is permeated by a network of cosmic strings, and what would it teach us about physics beyond the Standard Model? If the symmetry breaking scale is high (say GUT scale), then the strings are sufficiently massive that they should have been detected through lensing of the cosmic microwave background. Lighter strings cannot be exposed by gravitational probes, but instead we may seek evidence of the string network through its particle emission. Direct evidence may come in the form of a diffuse cosmic ray flux or spectral distortion of the CMB, while indirect constraints are provided by nucleosynthesis. I will discuss non-superconducting cosmic strings in a generic "hidden sector" extension of the Standard Model, which has often been studied in the context of dark matter, collider phenomenology, and electroweak baryogenesis. The Standard Model fields couple to the cosmic string, allowing for particle emission. I will discuss recent improvements and extensions of the analytic, perturbative particle production calculation, and I will survey various cosmological and astrophysical signatures in order to assess the extent to which light cosmic strings can be tested. - May 4, 2015 | 12:00 PM | ACC Conference Room | Open Group seminar
Searching for gravitational waves with pulsar-timing arrays
Michele Vallisneri, Jet Propulsion Laboratory
TBA - May 27, 2015 | 12:00 PM | LASR Conference Room | Open Group seminar
Looking for the identity of the dark matter in and around the Milky Way
Carlos S Frenk, Durham University
The identity of the dark matter remains one of the outstanding unsolved problems in Physics. The overwhelming majority of practitioners agree that it must be an elementary particle of some kind, but there are now claimed detections of two completely different kinds of particle candidates: cold and warm dark matter. These make very similar predictions for the large-scale structure of the universe, but very different predictions for its small-scale structure. I will present results from recent cosmological simulations of our cosmic neighbourhood for models in which the dark matter is of either kind and discuss them in the light of three famous puzzles: the ''core-cusp'', ''missing satellites'' and ''too-big-to-fail''
problems. I will address the question of whether astronomical observations can distinguish between the two kinds of dark matter.
ASTRONOMY SPECIAL SEMINARS - April 21, 2015 | 12:00 PM | LASR | Special Seminar
Not-so-simple stellar populations in nearby, resolved massive star clusters
Richard de Grijs, Kavli Institute for Astronomy and Astrophysics, Peking University, China
Until about a decade ago, star clusters were considered "simple" stellar populations: all stars in a cluster were thought to have similar ages and the same metallicity. Only the individual stellar masses were thought to vary, in essence conforming to a "universal" initial mass function. Over the past decade, this situation has changed dramatically. Yet, at the same time, star clusters are among the brightest stellar population components and, as such, they are visible out to much greater distances than individual stars, even the brightest, so that understanding the intricacies of star cluster composition and their evolution is imperative for understanding stellar populations and the evolution of galaxies as a whole. I will discuss my group's recent progress in this context, with particular emphasis on the properties and importance of binary systems, the effects of rapid stellar rotation, and the presence of multiple populations in Local Group star clusters across the full age range. Our most recent results imply a reverse paradigm shift, back to the old simple stellar population picture for at least some intermediate-age (~2 Gyr-old) star clusters, which opens up exciting avenues for future research. - June 5, 2015 | 1:30 PM | KPTC 106 | Special Seminar
The Voyager Odyssey
Edward Stone, Caltech
Launched in 1977 to explore Jupiter, Saturn, Uranus, and Neptune, the two Voyager spacecraft continued their journeys beyond the planets as they searched for the edge of heliosphere, the boundary between the solar wind the local interstellar medium. After a thirty-five year journey taking it eighteen billion kilometers from the sun, Voyager 1 became the first human-made object to enter interstellar space. In the next several years Voyager 2 will likely join Voyager 1 in exploring the local interstellar medium and its interaction with the heliosphere.
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Overview