Seminar archive 2014

Raw date Event date Title Speakers Host Summary Links
20140122 Jan. 22, 2014, 3:00 pm Weak Lensing Magnification and Large Scale Structure Gravitational lensing, the deflection of photons by changes in gravitational potential, modifies the observed brightness and shape of galaxies that lie behind massive objects. In an astronomical survey, the detected number count density of sources and their apparent brightnesses will be modified by the magnification effects of gravitational lensing. By measuring these effects we can... More »
20140127 Jan. 27, 2014, 2:30 pm Cosmology Results from the Pan-STARRs Supernova Survey The Pan-STARRs supernova survey has discovered one of the largest samples of Type Ia supernovae. Measurements of the distances to these supernovae allow us to probe some of the most fundamental questions about the properties of the universe like what is dark energy. When combining measurements from various astrophysical probes, we find interesting tension with... More »
20140203 Feb. 3, 2014, 2:30 pm Some New Isocurvature Directions I will discuss two unexplored parts of isocurvature parameter space. In one, the compensated isocurvature mode (a fluctuation in the cosmic baryon fraction), the usual linear theory observables are hidden, and the model unconstrained using familiar analyses. Instead, the hypothesis can be tested using the CMB trispectrum (put alternatively, using off-diagonal correlations). After developing the... More »
20140210 Feb. 10, 2014, 2:30 pm The Fermilab Holometer: A Measurement of Planck Scale Quantum Geometry We are developing an instrument to determine whether a newly predicted position uncertainty is compatible with experiment. The possibility that information in a system scales as its surface area rather than its volume – the holographic principle – motivates this prediction. The required position uncertainty, scaled by the entropy of black holes, is of a... More »
20140217 Feb. 17, 2014, 2:30 pm Detecting Small Planets orbiting Small Stars Thanks to Kepler, today we know that small stars often host Earth-size planets. Approximately half of all stars are low-mass M dwarfs, and at least half of these may have an Earth-size companion. This means it is likely that there are Earth-like planets within just a few parsecs of the Sun. Given the cool temperature,... More »
20140224 Feb. 24, 2014, 2:00 pm Large-Scale Structure Formation with Massive Neutrinos The lightest known massive particle in the Universe, the neutrino, is the focus of major terrestrial experiments. The physics of the neutrino sector is also being probed by ongoing and upcoming cosmological surveys. First postulated in 1930 by Wolfgang Pauli and discovered in 1956 by Cowan and Reines, the neutrino continues to surprise physicists. Introduced... More »
20140303 March 3, 2014, 2:00 pm The high-energy cosmic-ray sky as seen by IceCube, IceTop and AMANDA Cosmic rays with energies in the TeV-PeV range are believed to originate in astrophysical accelerators within our galaxy. During their propagation, cosmic rays are scattered by the Galactic magnetic field, a process that makes their arrival directions at Earth almost entirely isotropic. However, anisotropy with per-mille amplitude, or lower, should subsist in the cosmic-ray sky.... More »
20140310 March 10, 2014, 12:30 pm The Characterization of the Gamma-Ray Signal from the Central Milky Way: A Compelling Case for Annihilating Dark Matter In scenarios where dark matter particles can annihilate to produce standard model, the galactic center of the Milky Way is expected to provide the highest flux from dark matter in the sky. This has allowed galactic center observations to set extremely stringent limits on the parameters of the dark matter particle. Recently, we have worked... More »
20140310 March 10, 2014, 2:00 pm DarkSide-50: Performance and results from the first atmospheric argon run DarkSide-50 is the first physics detector of the DarkSide family, featuring a two-phase underground-argon Time Projection Chamber (50 kg sensitive mass) surrounded by an organic liquid scintillator veto (30 tonnes) and a muon water-Cherenkov detector (1000 tonnes). The two-phase detector is currently operating at Gran Sasso underground laboratory, fully shielded and filled with research grade... More »
20140317 March 17, 2014, 2:00 pm An argument that the dark matter is axions An argument is presented that the dark matter is axions, at least in part. It has three steps. First, axions behave differently from the other forms of cold dark matter because they form a rethermalizing Bose-Einstein condensate (BEC). Second, there is a tool to distinguish axion BEC from the other dark matter candidates on the... More »
20140331 March 31, 2014, 2:00 pm Weak Gravitational Lensing of Galaxy Clusters As the most massive bound objects in the universe, galaxy clusters are excellent probes of the underlying mass density field. The abundance of clusters as a function of mass and their spatial clustering directly constrain the overall mass density of the universe, as well as higher order properties such as the variance in the mass... More »
20140407 April 7, 2014, 12:30 pm Gravitational Wave Detectors in Europe and the US The detection of Gravitational waves is widely viewed as a “new window to the universe”. We report on the current effort of building the second generation of ground-based Gravitational-wave detectors in Europe and the US, as well as some related research. Detectors like Virgo (Italy), LIGO (US), and the smaller GEO600 (Germany) are technically complex,... More »
20140407 April 7, 2014, 2:00 pm Weighing the Giants: Accurate Weak Lensing Mass Measurements for Cosmological Cluster Surveys Surveys of galaxy clusters provide a sensitive probe of cosmology by measuring the evolution of the halo mass function. With a number of surveys at optical, millimeter, and X-ray wavelengths on-going or starting in the near futures, cluster count experiments will be one the most important cosmological probes over the next decade. However, none of... More »
20140421 April 21, 2014, 2:00 pm Big B, Little B, What Begins with B? Bandits, B Modes, and Bispectrumese One of the principal goals of early-Universe cosmology is detection of the characteristic curl, or “B mode,” signal in the cosmic microwave background (CMB) polarization. In this talk, I will discuss a new adaptive-survey strategy, inspired by the multi-armed-bandit problem in probability theory, to optimize the sensitivity of experiments to these B modes. I will... More »
20140505 May 5, 2014, 2:00 pm Latest Results from the Cluster Lensing and Supernovae Survey with Hubble (CLASH) The Cluster Lensing And Supernova survey with Hubble (CLASH) combines the gravitational lensing power of 25 massive clusters with the panchromatic imaging power of HST. It’s four primary scientific objectives are 1) map, with unprecedented accuracy, the distribution of dark matter in galaxy clusters and place constraints on the nature of the dark matter, 2)... More »
20140507 May 7, 2014, 3:00 pm Projects to search WIMPS and neutrinoless double beta decays at the Center for Underground Physics The Dark Energy Survey (DES) is an ongoing Stage III cosmology survey in optical to near-infrared wavelengths. I will briefly review the current state of the survey and demonstrate how ongoing improvements of data quality and consistency have enabled the first publication based on DES data, a lensing analysis of four massive galaxy clusters. I... More »
20140512 May 12, 2014, 2:00 pm Searching for Axions The axion is a hypothetical elementary particle whose existence would explain the baffling absence of CP violation in the strong interactions. Axions also happen to be a good dark-matter candidate. Even if dark-matter axions comprised the overwhelming majority of mass in the universe, they would be extraordinarily difficult to detect. However, several experiments are either... More »
20140602 June 2, 2014, 2:00 pm Introducing Clustering Redshifts I will present a new method to infer the redshift distribution of astronomical datasets. The technique, based on spatial correlations, can be applied to any photometric sample, discrete or continuous, and at any wavelength. I will present a number of results using datasets in the UV, optical, IR and radio wavelengths. Notes: 1304
20140609 June 9, 2014, 2:00 pm SPIDER: A Balloon-Borne Polarimeter for Cosmic Microwave Background Observation SPIDER is a balloon-borne polarimeter designed to characterize the primordial gravitational wave signal in the degree-scale B-mode polarization of the cosmic microwave background (CMB). With six independent telescopes housing a total of 2000 detectors in the 90 GHz and 150 GHz frequency bands, SPIDER is poised to be the most sensitive CMB polarimeter on the... More »
20140616 June 16, 2014, 2:00 pm A WISE search for large extraterrestrial civilizations: a complementary approach to traditional SETI If alien civilizations exist throughout the universe, many have had billions of years to develop technology, expand their population and energy supplies, and travel across their galaxies. Kardashev classified hypothetical advanced civilizations by the magnitude of their power supply, with Type II civilizations harnessing most of the energy output of their host star, and Type... More »
20140617 June 17, 2014, 2:00 pm Digital Readout for UV through Near-IR MKIDs ARCONS, the ARray Camera for Optical to Near-IR Spectrophotometry, is a photon counting integral field unit optimized to observe 400-1100 nm. It is built around a 2024 pixel array of MKIDs (Microwave Kinetic Inductance Detectors), an emerging superconducting detector technology. MKIDs are frequency domain multiplexed and are read out over two feedlines, using tones at... More »
20140623 June 23, 2014, 2:00 pm Evidence for High Energy Astrophysical Muon Neutrinos with IceCube One of the long-standing goals of high energy neutrino astronomy has been to observe muons produced by muon neutrinos which, due to their ability to point back along their direction of travel, can pave the way to locating astrophysical sources of neutrinos and cosmic rays. In this talk I will show preliminary results from a... More »
20140730 July 30, 2014, 10:30 am The Growth of Supermassive Black Holes with their Co-Evolution with Galaxies Using multi-wavelength surveys like GOODS, COSMOS, and Stripe 82X, we measure the growth of supermassive black holes at the centers of galaxies over the last 10 billion years. Most actively growing black holes are heavily obscured and thus are not seen in large area optical surveys like the Sloan Digital Sky Survey; furthermore, obscuration is... More »
20140806 Aug. 6, 2014, 2:30 pm Understanding Cosmic Acceleration with DES and Beyond The Dark Energy Survey (DES) is a large imaging sky survey designed to enable us to understand the physics underlying the accelerated expansion of the Universe. Cosmic acceleration can be explained either by invoking a new energy component to the Universe, dark energy, or by introducing a new fundamental theory of gravity. In either case... More »
20140812 Aug. 12, 2014, 11:00 am Facing the challenge: Gravitational lensing in DES The Dark Energy Survey (DES) is an ongoing Stage III cosmology survey in optical to near-infrared wavelengths. I will briefly review the current state of the survey and demonstrate how ongoing improvements of data quality and consistency have enabled the first publication based on DES data, a lensing analysis of four massive galaxy clusters. I... More »
20140908 Sept. 8, 2014, 11:00 am Time Delay Cosmology Thousands of strong gravitational lenses will be found by time domain surveys such as DES and LSST. Time delays between multiple images can be used to form a geometric time delay distance, a cosmological probe with some unique sensitivities and complementarities. In addition to the cosmology impact, I discuss the statistics challenge of accurate estimation... More »
20140915 Sept. 15, 2014, 2:00 pm New Physics and Indirect Dark Matter Detection Can we learn about New Physics with astronomical and astro-particle data? Understanding how this is possible is key to unraveling one of the most pressing mysteries at the interface of cosmology and particle physics: the fundamental nature of dark matter. I will discuss some of the recent puzzling findings in astro-particle and astronomical observations that... More »
20140922 Sept. 22, 2014, 2:00 pm Testing Neutrino Properties with Large-scale Structure The large-scale structure of our universe (the distribution of galaxies on very large-scales for instance) contains a wealth of information about the origin, evolution, and matter content of the universe. I will discuss physical effects of the cosmic neutrino background on the process of structure formation and present new signatures of massive cosmic background neutrinos... More »
20140929 Sept. 29, 2014, 2:00 pm The Ice Cube Puzzle Astrophysical neutrinos are unambiguous tracers of hadronic interactions of cosmic rays (CRs) in our Universe. With this in mind, high energy neutrino astronomy has long been anticipated to help uncover the origin of high energy CRs. The recent detection of a flux of high-energy extraterrestrial neutrinos by the IceCube Observatory is an important step in... More »
20141006 Oct. 6, 2014, 2:00 pm Implications of the Candidate Dark Matter Decay Line at 3.5 keV Two independent groups have detected an unidentified X-ray line at 3.5 keV that is consistent with the dark matter density in the field of view of the observations toward the Perseus Cluster, stacked X-ray clusters, Andromeda, and the Milky Way Galactic Center. I will discuss the sterile neutrino dark matter decay interpretation of the line,... More »
20141013 Oct. 13, 2014, 2:00 pm Lyman alpha Forest in optically thin cosmological simulations The Lyman-alpha forest is the main tracer of cosmological structure at high redshifts, 2<z<4, accessible to current (BOSS/eBOSS) and future (DESI) sky surveys. On large-scales, the Ly-a power spectrum is used as a standard ruler, measuring the Baryon acoustic oscillations (BAO) scale at high redshifts. On small-scales, the Ly-a forest allows one to constrain neutrino... More »
20141020 Oct. 20, 2014, 2:00 pm Cosmic Reionization on Computers I will review the field of numerical simulations of cosmic reionization: the process of ionizing of intergalactic medium by high redshift galaxies and quasars. I will describe the main physical processes that are important for modeling reionization, explain how these processes are incorporated in computer simulations, and will use simulations to gain insight into the... More »
20141027 Oct. 27, 2014, 2:00 pm Cosmic ray anisotropies and nearby sources Recently, the AMS-02 collaboration has presented data on cosmic ray protons, Helium, electrons and positrons as well as the boron-to-carbon ratio. We present the first consistent modeling of these data, paying particular attention to the contribution due to production and acceleration of secondary electrons and positrons in nearby supernova remnants. This process results in an... More »
20141103 Nov. 3, 2014, 2:00 pm Cosmic Reionization Cosmic reionization, and the preceding ‘dark ages’, corresponds to the epoch when light from the first galaxies reionized the neutral intergalactic medium (IGM) that pervaded the Universe following recombination. This epoch is the last frontier in the study of cosmic evolution, corresponding to the formation of the first galaxies and black holes. I will discuss... More »
20141110 Nov. 10, 2014, 2:00 pm The non-universality of halo density profiles The density profiles of dark matter halos are an essential input for models of galaxy formation, as well as for the interpretation of numerous observations such as weak and strong lensing signals. The profiles are commonly thought to follow a simple, universal shape, and only depend on two parameters, mass and concentration. Using a large... More »
20141114 Nov. 14, 2014, 10:00 am The axion search plan at the Center for Axion and Precision Physics in Korea The center for axion and precision physics research (CAPP) in Korea is recently been established by the Institute for Basic Science (IBS) of South Korea to establish a state of the art axion dark matter experiment in Korea and play a leadership role in the storage ring proton EDM experiment. With a number of new... More »
20141117 Nov. 17, 2014, 2:00 pm Probing Dark Energy with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) CHIME will use the 21cm emission line of neutral hydrogen to map large-scale structure between redshifts of 0.8 and 2.5. By measuring BAO we will place constraints on the dark energy equation of state as it begins to dominate the expansion of the Universe, particularly at redshifts poorly probed by current BAO surveys. In this... More »
20141120 Nov. 20, 2014, 1:30 pm Dark Matter Complementarity The cosmic reionization, and the preceding ‘dark ages’, corresponds to the epoch when light from the first galaxies reionized the neutral intergalactic medium (IGM) that pervaded the Universe following recombination. This epoch is the last frontier in the study of cosmic evolution, corresponding to the formation of the first galaxies and black holes. I will... More »
20141124 Nov. 24, 2014, 2:00 pm MKIDs at FNAL: From Detector R&D to Dark Energy Science We will discuss the progress done over the last couple of years on R&D for UV-VIS-IR MKIDs. This will include a description of the activities in the lab, and at telescopes. We will also present our plans for a prototype instrument at the 4m telescope at SOAR. Finally, the potential of these sensors as new... More »
20141208 Dec. 8, 2014, 2:00 pm Planck 2014 Cosmology Results The Planck 2014 cosmology likelihood will include the tightest measurements to-date of CMB polarization at intermediate angular scales. I will present parameter constraints on LCDM and extensions from these data, including on the effective number and masses of the neutrinos, as well as other parameters describing dark matter, axions, and inflation. In doing so, I... More »
20141215 Dec. 15, 2014, 2:00 pm The outskirts of Milky-Way mass galaxies - a probe of dark matter driven growth Dark matter is central to our idea of how galaxies grow and develop. Dark matter overdensities trigger the initial collapse, dark matter halos merge and grow continuously to the present day, and dark matter constitutes most of the gravitationally important mass in present-day galaxies. Yet, we know precious little about the actual dark matter merger... More »
20141216 Dec. 16, 2014, 1:00 pm Optical Spectroscopy with Starbugs, from TAIPAN to the Giant Magellan Telescope The majority of astronomical fibre-fed spectroscopic instruments rely on sequential positioning of fibres that require significant time (up to an hour in some cases) to reconfigure a field for observation, thus reducing the amount of on-sky time available for any instrument. Starbugs, a novel fibre-positioning technology developed by the Australian Astronomical Observatory, allow for simultaneous... More »