KICP Seminars & Colloquia, Winter 2010

KICP Seminars & Colloquia

COLLOQUIA
FRIDAY NOON SEMINARS
OPEN GROUP SEMINARS

Seminar schedule for Winter 2010

January 6, 2010 Wednesday colloquium	Sam Waldman MIT	Attometer Astrophysics: Gravitational wave astronomy with LIGO [Abstract]
January 8, 2010 Friday noon seminar	George Becker Kavli Institute for Cosmology, Cambridge	Observational Signatures of Hydrogen and Helium Reionization [Abstract]
January 13, 2010 Astronomy Colloquium	Fred Ciesla The University of Chicago (Geophysical Sciences)	The Early Stages of Planet Formation: Astrophysics Meets Cosmochemistry [Abstract]
January 15, 2010 Friday noon seminar	Jaiyul Yoo Harvard University	New Perspective on Galaxy Clustering as a Cosmological Probe: General Relativistic Effects
January 20, 2010 Astronomy Colloquium	Mark Krumholz University of California - Lick Observatory	Understanding the Star Formation Rate [Abstract]
January 22, 2010 Friday noon seminar	Dan Hooper University Chicago/FNAL	The hunt for dark matter continues
January 26, 2010 Open Group seminar	Neal Dalal CITA, University of Toronto	The Handwaver's Guide to Dark Matter Halos [Abstract]
January 27, 2010 Wednesday colloquium	Nadia Zakamska Institute for Advanced Study	The structure and evolution of obscured quasars [Abstract]
January 29, 2010 Friday noon seminar	Smadar Naoz Northwestern uniersity	The first generations of galaxies and 21cm fluctuations [Abstract]
February 1, 2010 Open Group seminar	Aurelien Benoit-Levy Institut d'Astrophyique de Paris	Observational Constraints on a Matter-antimatter Symmetric Dirac-Milne Universe
February 3, 2010 Astronomy Colloquium	Enrico Ramirez-Ruiz University of California (Lick Observatory)	Waves, Winds and Jets from Coalescing Compact Binaries [Abstract]
February 5, 2010 Friday noon seminar	Vasiliki Pavlidou Caltech	Deconvolving the GeV Sky: Deriving the Physics of Starforming Galaxies, Active Galaxies, and Dark Matter [Abstract]
February 10, 2010 Wednesday colloquium	Maryam Modjaz UC Berkeley	Understanding the Diverse Explosions of Massive Stars: Supernovae, Gamma-Ray Bursts, and their Host Galaxies [Abstract]
February 12, 2010 Friday noon seminar	Dan Marrone The University of Chicago	Peering at the horizon: A close look at Sagittarius A* and other black holes [Abstract]
February 17, 2010 Wednesday colloquium	Mary Putman Columbia University	Feeding Gaseous Baryons to Galaxies [Abstract]
February 19, 2010 Friday noon seminar	Daniel N Kasen UC Santa Cruz	Characterizing the Transient Sky [Abstract]
February 24, 2010 Astronomy Colloquium	William Cochran McDonald Observatory, The University of Texas at Austin	First Science Results from Kepler [Abstract]
February 26, 2010 Friday noon seminar	Joseph W Fowler Princeton University	Cosmology from the CMB at arcminute scales: first results from the Atacama Cosmology Telescope [Abstract]
March 3, 2010 Wednesday colloquium	Brenda L Dingus Los Alamos National Lab	Surveying the TeV Sky with Milagro and HAWC [Abstract]
March 5, 2010 Friday noon seminar	Anupreeta More The University of Chicago	Statistics of SL2S Arcs from the CFHTLS [Abstract]
March 10, 2010 Astronomy Colloquium	Gregory Laughlin University of California Santa Cruz	Insights from the Galactic Planetary Census [Abstract]
March 12, 2010 Friday noon seminar	Asad Aboobaker University of Minnesota	The E and B Experiment [Abstract]
March 17, 2010 Astronomy Colloquium	Andrew Gould Ohio State University	Microlensing Planets: A Controlled Scientific Experiment Drawn From Absolute Chaos [Abstract]

COLLOQUIA

January 6, 2010 | 3:30 PM | RI 480 | Wednesday colloquium
Attometer Astrophysics: Gravitational wave astronomy with LIGO
Sam Waldman, MIT

The direct detection of gravitaitonal waves will provide a revolutionary new probe of the most energetic processes in the universe. The 4 km long LIGO interferometers have demonstrated the sub-attometer displacement sensitivity (< 10^{-18} m/ Hz^{1/2}) required to place upper limits on the neutron star/neutron star merger out beyond the Virgo galaxy cluster. Such mergers are thought to be the progenitors of short gamma-ray bursts and provide an ideal "golden event" signal for direct GW detection. An aggressive R&D program, Advanced LIGO, is underway to increase the interferometer stored power 30-fold (to 750 kW), develop new low noise readouts, and increase the detector sensitivity by an order of magnitude. In the next 5 years, Advanced LIGO will observe neutron star mergers and other gravitational wave events regularly, beginning a new era of gravitational astronomy.
January 13, 2010 | 3:30 PM | RI 480 | Astronomy Colloquium
The Early Stages of Planet Formation: Astrophysics Meets Cosmochemistry
Fred Ciesla, The University of Chicago (Geophysical Sciences)

Protoplanetary disks are dynamic objects through which mass and angular momentum are transported as part of the final stages of pre-main sequence evolution for a star. Chondritic meteorites record a dynamic history for our own solar system as they contain a variety of objects that formed in distinct physical and chemical environments, yet are intimately mixed on fine-scales. To date it remains to be determined whether models of protoplanetary disks can explain the variety of primitive materials found in our own solar system and how they came to be accreted into common meteorite parent bodies. Further, it remains unclear what stages of disk evolution identified by astrophysical models are recorded within meteorites. I will discuss these issues and argue that the earliest stages of solar nebula evolution recorded by meteorites coincide with no later than the first few hundred thousand years of our sun's formation.
January 20, 2010 | 3:30 PM | RI 480 | Astronomy Colloquium
Understanding the Star Formation Rate
Mark Krumholz, University of California - Lick Observatory

Stars are the engines of the Universe: nuclear reactions within them are the only significant source of non-gravitational power in the cosmos and the source of all heavy elements. However, the process by which stars form remains poorly understood, and one mystery in particular stands out: why is star formation so slow? In many galaxies the bulk of the interstellar medium does not participate in star formation, and in all galaxies even those clouds that are active form stars at a rate of only ~1% of their mass per dynamical time. Any successful theory of cosmic evolution must be able to explain these facts, and be able to predict how the star formation process changes with galactic environment and over cosmological time. In this talk I discuss progress toward a physical theory of star formation capable of meeting these requirements.
January 27, 2010 | 3:30 PM | RI 480 | Wednesday colloquium
The structure and evolution of obscured quasars
Nadia Zakamska, Institute for Advanced Study

Quasars are among the most powerful objects in the Universe and are now thought to play an important role in galaxy evolution. Despite their extreme luminosity, the majority of all quasars have eluded detection through conventional methods until recently. In these objects, the active regions are embedded in clouds of gas and dust, making them faint at optical, ultraviolet and X-ray frequencies, quite unlike 'normal' quasars that are bright at these wavelengths. I will present a detailed study of such obscured quasars, describe the evolution of these objects and their host galaxies and review the current status of quasar demographics studies from multi-wavelength surveys.
February 3, 2010 | 3:30 PM | RI 480 | Astronomy Colloquium
Waves, Winds and Jets from Coalescing Compact Binaries
Enrico Ramirez-Ruiz, University of California (Lick Observatory)

Merging compact binaries are the one source of gravitational radiation so far identified. Because short-period systems that will merge in less than a Hubble time have already been observed as binary pulsars, they are important both as gravitational wave sources for observatories such as LIGO, but also as progenitors for short gamma-ray bursts. Recent progress in our understanding of these systems is outlined, emphasizing the breadth of the subject and the links with fundamental physics. An effort is made to distinguish between ideas that are already well established and those that still lie on the speculative frontiers. There are, fortunately, several feasible types of observation that could soon clarify the issues.
February 10, 2010 | 3:30 PM | RI 480 | Wednesday colloquium
Understanding the Diverse Explosions of Massive Stars: Supernovae, Gamma-Ray Bursts, and their Host Galaxies
Maryam Modjaz, UC Berkeley

Long-duration gamma-ray bursts (GRBs) and Type Ib/c Supernovae (SN Ib/c) are two of nature's most magnificent explosions. Both can be seen over cosmological distances, and both are products of collapsing massive stars. While GRBs launch relativistic jets, SN Ib/c are core-collapse explosions whose massive progenitors have been stripped of their hydrogen and helium envelopes. Yet for over a decade, one of the key outstanding questions in astronomy is what conditions lead to each kind of explosion in massive stars. Determining the fate of massive stars is essential for using GRBs as star formation indicators over distances up to 13 billion light-years, and for mapping the chemical enrichment history of the universe.
I will present a number of comprehensive observational studies that probe the progenitor environments, their metallicities and the explosion conditions of SN with and without GRBs. Specifically, my benchmark study on the measured metallicities of SN with and without GRBs indicates that low metallicity (less than ~1/3 solar) might be the key factor for producing SN-GRBs, providing constraints on the theoretical predictions of GRB formation. Furthermore, I will discuss SN 2008D, which was discovered serendipitously in January 2008 with the NASA Swift satellite via its X-ray emission and has generated great interest amongst both observers and theorists. I will discuss the significance of this SN, whether it harbored a jet, and its implications for the SN-GRB connection. I will conclude with an outlook on how the most promising venues of research - using both existing facilities such as Magellan and innovative SN surveys, and also upcoming large-scale surveys such as LSST - will shed light on the diverse deaths of massive stars.
February 17, 2010 | 3:30 PM | RI 480 | Wednesday colloquium
Feeding Gaseous Baryons to Galaxies
Mary Putman, Columbia University

Galaxies like the Milky Way form stars throughout their lifetimes at rates that indicate a continuous fuel source is needed. I will discuss the evidence for this continual fueling with a focus on gas surrounding the Milky Way. In particular, the roles of existing cold halo clouds and the extended diffuse hot halo medium are discussed in the context of local and cosmological simulations of galaxy formation.
February 24, 2010 | 3:30 PM | RI 480 | Astronomy Colloquium
First Science Results from Kepler
William Cochran, McDonald Observatory, The University of Texas at Austin

The Kepler spacecraft, launched in March 2009, is designed to detect potentially habitable Earths around other stars by detecting the transits of these planets across the disks of their parent stars. This requires performing differential photometry to a precision of 20ppm on a sample of 170,000 stars for a period of 3.5 years. We will discuss the on-orbit performance of the Kepler photometer, and then present the first scientific results from Kepler. Five new transiting planets around solar-type stars have been discovered so far, along with several other interesting objects.
March 3, 2010 | 3:30 PM | RI 480 | Wednesday colloquium
Surveying the TeV Sky with Milagro and HAWC
Brenda L Dingus, Los Alamos National Lab

The deepest, wide field of view survey of the TeV sky has been performed with the Milagro observatory, probing the origin of Galactic cosmic rays through discovery of new Galactic gamma-ray sources, diffuse Galactic gamma-ray emission, and unexpected localized regions of hadronic cosmic rays. Milagro was located near Los Alamos, NM and was operated from 2000-2008. A next-generation version of this wide field of view, high duty cycle, water Cherenkov observatory is called HAWC. HAWC will be located near Puebla, Mexico at an elevation of 13,500' and will have 15 times the sensitivity of Milagro. I will discuss results from Miilagro and the expected contributions of HAWC.
March 10, 2010 | 3:30 PM | RI 480 | Astronomy Colloquium
Insights from the Galactic Planetary Census
Gregory Laughlin, University of California Santa Cruz

The past year has seen enormous advances in our understanding of extrasolar planets. In this talk, I'll focus on some of the most exciting recent highlights. These include (i) the discovery and characterization of remarkable new transiting planets, (ii) a complete upending of the conventional wisdom regarding the statistics of the galactic planetary census, and (iii) a new method for actually looking inside certain transiting planets.
March 17, 2010 | 3:30 PM | RI 480 | Astronomy Colloquium
Microlensing Planets: A Controlled Scientific Experiment Drawn From Absolute Chaos
Andrew Gould, Ohio State University

Microlensing planet searches have discovered a total of 17 planets, including the first Jupiter-Saturn like system and the only 4 "cold Neptunes" yet detected. The discovery process is almost unbelievably chaotic, with the so-called "high-magnification events" being the most chaotic. I show, nevertheless, that the high-magnification subsample constitutes a "controlled experiment",
which enables rigorous statistical analysis, yielding important new clues to planetary architecture. I also discuss the future potential of microlensing to explore domains of planet parameter space not probed by any other method.

FRIDAY NOON SEMINARS

January 8, 2010 | 12:00 PM | LASR Conference Room | Friday noon seminar
Observational Signatures of Hydrogen and Helium Reionization
George Becker, Kavli Institute for Cosmology, Cambridge

The reionization of hydrogen and helium are intimately linked to the formation of the first galaxies and quasars, yet setting direct observational constraints on either process has proven to be highly challenging. Over the past few years, a variety of observations have started to shed lights on both. I will review progress made in the field, and discuss my group's recent work on metal enrichment by the first galaxies and the thermal history of the intergalactic medium. These studies are providing unique insights into the first three billion years of evolution in the IGM, and will complement upcoming observations in developing a consensus picture of hydrogen and helium reionization.
January 15, 2010 | 12:00 PM | LASR Conference Room | Friday noon seminar
New Perspective on Galaxy Clustering as a Cosmological Probe: General Relativistic Effects
Jaiyul Yoo, Harvard University
January 22, 2010 | 12:00 PM | LASR Conference Room | Friday noon seminar
The hunt for dark matter continues
Dan Hooper, University Chicago/FNAL
January 29, 2010 | 12:00 PM | LASR Conference Room | Friday noon seminar
The first generations of galaxies and 21cm fluctuations
Smadar Naoz, Northwestern uniersity

The formation of the first generation of galaxies in the Universe has been studied for many years. We studied this epoch taking into account important physical ingredients. We show that these ingredients play a major role in the evolution of over-densities both in the linear and non-linear regime and on the formation and properties of the first luminous objects in the Universe. We give a detailed set of predictions for these objects, and in particular show that the first observable star was most likely to form only 30 million years after the big bang (at redshift 65), with the first observable Gamma ray burst exploding only a few million years later. Observations of the 21cm radiation from these epochs will help unfold the cosmic evolution of the first generation of galaxies. These observations are strongly affected by the UV radiation from stars at this era which couples the properties of the 21cm signal and the distribution of the first galaxies. Using an accurate analysis of this coupling process, including the ionized gas bubble around each galaxy, we predict a clear signature of this process. We show that such observable signatures can be used to detect and study the population of galaxies that formed as early as 200 Myr after the big bang.
February 5, 2010 | 12:00 PM | LASR Conference Room | Friday noon seminar
Deconvolving the GeV Sky: Deriving the Physics of Starforming Galaxies, Active Galaxies, and Dark Matter
Vasiliki Pavlidou, Caltech

The recently launched Fermi Gamma-ray Space Telescope promises a decade of excitement and discovery in the GeV waveband. Fermi represents a dramatic improvement in instrumental capabilities for point source observations in GeV gamma rays compared to its predecessors, and is expected to revolutionize our understanding of known gamma-ray sources such as star-forming galaxies and active galactic nuclei. However, Fermi also opens up for the very first time the window of observations between 20-200 GeV, and carries a significant potential for the discovery of a yet-unknown exotic signal, such as a signature of dark matter annihilation. I will discuss promising novel techniques for disentangling the different components of the gamma-ray sky, which will allow us to maximize the science return of the mission; to uncover and identify any potential dark matter signal that may be hiding among the diffuse GeV photons; and to use gamma-ray observations to directly address problems in particle physics and astrophysics that may be otherwise inaccessible.
February 12, 2010 | 12:00 PM | LASR Conference Room | Friday noon seminar
Peering at the horizon: A close look at Sagittarius A* and other black holes
Dan Marrone, The University of Chicago

The compact radio/IR/X-ray source Sagittarius A* marks the location of the Milky Way's central supermassive black hole. Investigations at all available wavelengths have shown it to be extremely under-luminous for its mass, radiating just 10^-9 of its Eddington luminosity. Several theoretical models of Sgr A*, which differ in their structure and physics, are able to match the spectrum and luminosity, and the discrepancies have not been resolved through observations of the source spectrum and variability alone. Here I present a program to understand Sgr A* through observations at (mostly) submillimeter wavelengths, a special place in the spectrum where a combination of instrument capabilities and source physics allow us to study the emission just outside the event horizon. Using purpose-built instruments and diverse observational techniques, including polarimetric monitoring and micro-arcsecond resolution imaging, we are disentangling the layers of source structure and should ultimately measure the black hole spin. In the era of ALMA the techniques we are using to study Sgr A* can be applied to more distant objects, culminating in a survey of black hole spins.
February 19, 2010 | 12:00 PM | LASR Conference Room | Friday noon seminar
Characterizing the Transient Sky
Daniel N Kasen, UC Santa Cruz

In the coming years, several astronomical surveys will night scan the sky with regular cadence, revealing an enormous number of supernovae and other optical transients, many never seen before. The study of these stellar disruptions is not only a vibrant topic in itself, but also impacts fundamental questions in cosmology, nucleosynthesis, compact objects, and the sources of gravitational waves. Insight from theory and modeling is required to physically interpret this data and to explain the new phenomena discovered. Here I discuss recent advances in large scale simulations which predict the signatures of a diverse range of explosive transients. I focus first on the thermonuclear, or Type Ia, supernovae. Using multi-dimensional light curve models, I show how variations in Type Ia brightness are driven by deviations from spherical symmetry, and illuminate the physical origin of the empirical correlations used to standardize these supernovae as measures of cosmic expansion. I then present predictions for two very different sorts of transients: the disruption of extremely massive stars via the electron-positron pair instability (believed to characterize the death of the first generation of stars) and the faint optical emission from the merger of neutron stars (considered a promising source for gravitational wave observatories).
February 26, 2010 | 12:00 PM | LASR Conference Room | Friday noon seminar
Cosmology from the CMB at arcminute scales: first results from the Atacama Cosmology Telescope
Joseph W Fowler, Princeton University

The many measurements of the cosmic microwave background (CMB) over the last two decades have provided a new view of the universe and a standard model of cosmology. The data support the basic picture of inflation and the hot Big Bang, and they allow us to estimate multiple cosmological parameters with nearly percent-level precision. There remains much to learn from terrestrial observations of the arcminute-scale CMB anisotropies. They can tell us about the emergence of structure in the large-scale distribution of matter and the properties of the dark energy. Their power spectrum is sensitive to parameters of the quantum field governing the epoch of inflation. With the new Atacama Cosmology Telescope, we are starting to map the CMB at arcminute resolution to address these questions. These small-scale temperature anisotropies--along with the polarization of the CMB at a wide range of angular scales--offer fertile ground for many fruitful observations in the decade to come.
March 5, 2010 | 12:00 PM | LASR Conference Room | Friday noon seminar
Statistics of SL2S Arcs from the CFHTLS
Anupreeta More, The University of Chicago

Formation of gravitational arcs in groups/clusters is sensitive to the parameters of the cosmological model. The observed statistics of arcs can hence be used to test the standard cosmological model. A meaningful comparison of the arc statistics has so far been hampered due to incompleteness and a variety of selection effects.
Strong Lensing Legacy Survey (SL2S) is a large survey of strong lens systems in the CFHTLS-Wide (170 sq. deg) and CFHTLS-Deep (4 sq. deg.). With the help of a systematic arc detection algorithm, Arcfinder, the SL2S arc sample is being compiled. We quantify the completeness of the SL2S arcs sample by simulating mock gravitational arcs. We present preliminary results of the statistical properties of the SL2S arcs sample and its completeness which could be compared with predictions of standard model.
March 12, 2010 | 12:00 PM | LASR Conference Room | Friday noon seminar
The E and B Experiment
Asad Aboobaker, University of Minnesota

The E and B EXperiment (EBEX) is a long-duration balloon-borne mission to study the polarization of the Cosmic Microwave Background. In particular, the instrument is designed to measure or set a stringent upper limit on B-mode CMB polarization arising from inflationary gravitational waves. In this talk, I will review the science behind EBEX, describe the design of the experiment, and report on its current status following our recent North American test flight.

OPEN GROUP SEMINARS

January 26, 2010

February 1, 2010

January 26, 2010 | 12:00 PM | LASR Conference Room | Open Group seminar
The Handwaver's Guide to Dark Matter Halos
Neal Dalal, CITA, University of Toronto

Dark matter halos play an important role in many areas of astrophysics and cosmology, and the properties of halos influence a wide variety of observables. Our understanding of halos is based almost entirely on N-body simulations, with relatively poor theoretical understanding of what determines halo properties. In my talk, I will try to give a simple way to understand many properties of halos, including their density profiles, their abundance, and their clustering. Using an extremely simple model, it is possible to match the results of N-body simulations across a wide range of cosmologies, even better than commonly used empirical fitting formulae. Using this approach, we can also predict how halos and their resident galaxies behave in cosmologies that depart from the standard LCDM model, which I will illustrate with some examples.
February 1, 2010 | 10:30 AM | LASR Conference Room | Open Group seminar
Observational Constraints on a Matter-antimatter Symmetric Dirac-Milne Universe
Aurelien Benoit-Levy, Institut d'Astrophyique de Paris

Inflation-based �CDM concordance model, which is considered today as the Standard Model of Cosmology is a great success as far as observations are concerned. Indeed, this model is in good agreement with a vast variety of cosmological tests, probing different aspects of Cosmology. However, successful as it is, this model requires the introduction in the theory of three ingredients, namely Dark Matter, Dark Energy and Inflation, which are of vital importance to the �CDM model, but whose nature is still uncertain. Faced to this uncomfortable situation, we investigate an alternative cosmological model that would not require Dark Matter nor Dark Energy nor Inflation. In this model, we consider a matter-antimatter symmetric universe, with the further assumption that antimatter has a negative active gravitational mass. After describing some basic properties of this alternative cosmology, I will concentrate on the study of cosmological tests such as primordial nucleosynthesis, type Ia supernovae and present some basic results concerning the CMB in the context of the Dirac-Milne universe.