KICP Seminars & Colloquia, Winter 2013

Seminar schedule for Winter 2013
January 9, 2013
Wednesday colloquium
Marc Kamionkowski
Johns Hopkins University
Covering the Bases   [Abstract]
January 16, 2013
Astronomy Colloquium
Juan Estrada
Fermilab
Imaging instruments for the cosmic frontier   [Abstract]
January 18, 2013
Friday noon seminar
Luigi Tibaldo
KIPAC - SLAC National Accelerator Laboratory
The Fermi LAT view of Cygnus: a laboratory to understand cosmic-ray acceleration and transport   [Abstract]
January 23, 2013
Wednesday colloquium
Ryan Keisler
The University of Chicago
New CMB Results from the South Pole Telescope   [Abstract]
January 25, 2013
Friday noon seminar
Troy Porter
Stanford University
Cosmic rays in the Milky Way and other galaxies   [Abstract]
January 30, 2013
Astronomy Colloquium
Feryal Ozel
University of Arizona
Neutron Star Radii and Masses   [Abstract]
February 1, 2013
Friday noon seminar
Emmanouil Papastergis
Cornell University
''Near-field'' cosmology with the ALFALFA survey   [Abstract]
February 6, 2013
Astronomy Colloquium
Alexei Kritsuk
University of California, San Diego
Towards ab initio simulations of star formation in turbulent molecular clouds   [Abstract]
February 8, 2013
Friday noon seminar
Guilhem Lavaux
University of Waterloo
Tracking Universe dynamics at large and small scales: cosmic voids and kSZ effects   [Abstract]
February 13, 2013
Wednesday colloquium
Mark Halpern
University of British Columbia
CMB Results from WMAP and ACT   [Abstract]
February 15, 2013
Friday noon seminar
Morag I Scrimgeour
University of Western Australia
Large-scale homogeneity vs. small-scale inhomogeneities: testing ΛCDM with large-scale structure   [Abstract]
February 20, 2013
Astronomy Colloquium
Elizabeth Hays
NASA
Gamma-ray detections of cosmic-ray acceleration by supernova remnants   [Abstract]
February 22, 2013
Friday noon seminar
Keith Vanderlinde
U of Toronto
CHIME: 21cm and the Expanding Universe   [Abstract]
February 27, 2013
Wednesday colloquium
Jennifer Siegal-Gaskins
Caltech
Shedding light on dark matter and astrophysical sources with gamma-ray anisotropy   [Abstract]
March 1, 2013
Friday noon seminar
Ann Zabludoff
University of Arizona / Steward Observatory
Deficit Spending and the Cluster Baryon Budget   [Abstract]
March 4, 2013
Special seminar
Bradford Benson
The University of Chicago
Thermal Detectors: Recent Applications, Lessons Learned, and Future Directions   [Abstract]
March 4, 2013
Astronomy Special Seminar
Bradford Benson
University of Chicago
Thermal Detectors: Recent Applications, Lessons Learned, and Future Directions   [Abstract]
March 6, 2013
Wednesday colloquium
Brian W O'Shea
Michigan State University
The secret lives of galaxy clusters   [Abstract]
March 8, 2013
Friday noon seminar
Mark C. Neyrinck
Johns Hopkins University
Gaussianization: How to Deal with Wrinkles in the Universe   [Abstract]
March 11, 2013
Astronomy Special Seminar
Akito Kusaka
Princeton University
A path toward the detection of CMB B-mode polarization from primordial gravitational waves   [Abstract]
March 11, 2013
Special seminar
Akito Kusaka
Princeton University
A path toward the detection of CMB B-mode polarization from primordial gravitational waves   [Abstract]
March 12, 2013
Special seminar
Erik Shirokoff
Caltech
Probing the dark ages at mm-wavelengths with SuperSpec, an MKID-based spectrometer-on-a-chip   [Abstract]
March 12, 2013
Astronomy Special Seminar
Erik Shirokoff
Caltech
Probing the dark ages at mm-wavelengths with SuperSpec, an MKID-based spectrometer-on-a-chip   [Abstract]
March 13, 2013
Special seminar
Clarence Chang
Argonne National Lab/The University of Chicago
Superconducting technology and New Windows into Cosmic Relics   [Abstract]
March 13, 2013
Astronomy Special Seminar
Clarence Chang
University of Chicago/Argonne
Superconducting Technology and Measuring the Cosmic Neutrino Background   [Abstract]
March 13, 2013
Astronomy Colloquium
Debra Fischer
Yale University
The Road to 100 Earths   [Abstract]
March 14, 2013
Astronomy Special Seminar
Roger O'Brient
Caltech
Monolithic Microwave Integrated Circuits for Experimental Astrophysics   [Abstract]
March 15, 2013
Special seminar
Megan Eckart
NASA/GSFC
Low-Temperature Detector Development to Further X-ray Astrophysics   [Abstract]
March 15, 2013
Astronomy Special Seminar
Megan Eckart
NASA GSFC
Low-temperature Detector Development to Further our Understanding of the X-ray Universe   [Abstract]
March 22, 2013
Friday noon seminar
Latham Boyle
Perimeter Institute
Gravitational Wave Telescopes, Time-Delay Interferometers and Choreographic Crystals   [Abstract]
 
WEDNESDAY COLLOQUIA

  • January 9, 2013 | 3:30 PM | BSLC 115
    Covering the Bases
    Marc Kamionkowski, Johns Hopkins University

    One of the principal aims of cosmology today is to seek subtle correlations in primordial perturbations, beyond the standard two-point correlation that has been mapped precisely already, that may hint at new physics beyond that in the simplest single-field slow-roll models. I will describe in this talk a new class of such correlations and how they may be sought with galaxy surveys and in the CMB. I will then turn my attention to a new formalism, total-angular-momentum (TAM) waves, that my collaborators and I have recently developed. In most of the literature, cosmological perturbations are decomposed into Fourier modes, or plane waves. However, for calculations that aim to produce predictions for angular correlations on a spherical sky, a decomposition into TAM waves provides a far more direct and intuitive route from theory to observations. I will describe the formalism and illustrate with applications to cosmic shear, three-point correlation functions, and redshift-space distortions.
  • January 23, 2013 | 3:30 PM | BSLC 115
    New CMB Results from the South Pole Telescope
    Ryan Keisler, The University of Chicago

    The South Pole Telescope (SPT) recently completed a 2500 square degree survey of the sky in the 3mm, 2mm and 1.4 mm bands with an unprecedented combination of resolution, area, and sensitivity. The data from this survey has enabled a number of studies, including the most precise measurement of the sub-degree primordial CMB anisotropy to date. This talk will review this measurement and the resulting cosmological constraints. The new SPT data, in conjunction with data from the WMAP satellite and low-redshift measurements, leads to strong constraints on the number of neutrino-like particle species present in the early universe, the sum of the neutrino masses, and the shape of the power spectrum of primordial density fluctuations. I will also give a brief update on the status of SPTpol, the new polarization-sensitive receiver on the SPT.
  • February 13, 2013 | 3:30 PM | BSLC 115
    CMB Results from WMAP and ACT
    Mark Halpern, University of British Columbia

    Acoustic processes in the plasma which pervades the early Universe govern the shape of the anisotropy of the cosmic background which has been measured by WMAP and other probes, notably ACT and the South Pole Telescope. I'll describe what we have learned, and what we have not learned from precise measurements of the temperature and polarization anisotropy of the CMB. Once the Universe became transparent, these acoustic signals stopped propagating. The density variations associated with them have remained fixed in co-moving (expanding) coordinates. I'll finish by talking about CHIME, the Canadian Hydrogen Intensity Mapping Experiment, CHIME, a collaboration to build a novel radio telescope designed to measure these same acoustic features at the much later epoch when cosmic acceleration from dark energy is important.
  • February 27, 2013 | 3:30 PM | BSLC 115
    Shedding light on dark matter and astrophysical sources with gamma-ray anisotropy
    Jennifer Siegal-Gaskins, Caltech

    Gamma rays probe the most energetic processes in the universe and are a promising tool to search for signatures of new physics. One current mystery in high-energy astrophysics is the origin of the diffuse gamma-ray background. The contribution of undetected sources is expected to induce small-scale anisotropies in this emission, and these may provide a means of identifying and constraining the properties of its contributors. I will review the results of the first anisotropy analysis of the diffuse gamma-ray background measured by the Fermi Large Area Telescope, and highlight the new constraints this measurement has placed on high-energy source populations, focusing on implications for blazar population models and for a signal from the annihilation or decay of dark matter particles. I will also present new multi-wavelength techniques for unraveling contributors to diffuse emission.
  • March 6, 2013 | 3:30 PM | BSLC 115
    The secret lives of galaxy clusters
    Brian W O'Shea, Michigan State University

    Galaxy clusters have the potential to be highly accurate probes of cosmological parameters. However, they are also very interesting astrophysical objects in their own right! The properties that make clusters irritating to those who wish to use them for cosmology - deviations from sphericity and hydrostatic equilibrium, shocks, mergers, and a variety of baryonic processes - provide a tremendous amount of information about these massive beasts. I will present recent efforts to understand the effects that correctly modeling the properties of gas in cosmological simulations have on the observable properties of clusters, focusing on shocks and the non-thermal components of the intracluster medium, including cosmic rays and magnetic fields.

 
FRIDAY NOON SEMINARS

  • January 18, 2013 | 12:00 PM | LASR Conference Room
    The Fermi LAT view of Cygnus: a laboratory to understand cosmic-ray acceleration and transport
    Luigi Tibaldo, KIPAC - SLAC National Accelerator Laboratory

    Gamma-ray emission detected by Fermi LAT (left) fills bubbles of hot gas created by the most massive stars in Cygnus X (right).

    Credit: NASA/DOE/Fermi LAT Collaboration/I. A. Grenier and L. Tibaldo
    The origin of cosmic rays (CRs) is a century-long puzzle. It is strongly advocated that Galactic CRs are accelerated by supernova remnant shockwaves. The CR isotopic composition and the fact that about 80% of the supernovae are produced by a massive-star core collapse establish a strong link between CR origin and massive-star forming regions. I will present the analysis of Fermi LAT observations of the Cygnus complex, which harbors the conspicuous massive-star forming region of Cygnus X at 1.4 kpc from the solar system. Gamma-ray observations can be used to trace CRs in the interstellar space interacting with the ambient gas and low-energy radiation fields. A 50-pc wide cocoon of freshly-accelerated CRs is detected in the region bounded by the ionization fronts from the young stellar clusters. On the other hand, the CR population averaged over the whole Cygnus complex on a scale of about 400 pc is similar to that found in the interstellar space near the Sun. I will discuss these results which confirm the long-standing hypothesis that massive-star forming regions host CR factories, which provide a test case to study the early phases of CR life in such a turbulent environment and which also shed a new light on the detections of TeV gamma-ray emission toward massive-star clusters.
  • January 25, 2013 | 12:00 PM | LASR Conference Room
    Cosmic rays in the Milky Way and other galaxies
    Troy Porter, Stanford University

    Cosmic rays fill up the entire volume of galaxies, providing an important source of heating and ionisation of the interstellar medium, and may play a significant role in the regulation of star formation and evolution of galaxies. Diffuse emissions from radio to high-energy gamma rays (> 100 MeV) arising from various interactions between cosmic rays and the interstellar gas, radiation, and magnetic fields are currently the best way to trace the intensities and spectra of cosmic rays in the Milky Way and other galaxies. In this talk, I will give an overview of the observations of the cosmic-ray induced emissions from our own and other galaxies, in particular, results from the Fermi-LAT. I will also talk about what can be deduced about the cosmic-ray origin and propagation from these data.
  • February 1, 2013 | 12:00 PM | LASR Conference Room
    ''Near-field'' cosmology with the ALFALFA survey
    Emmanouil Papastergis, Cornell University

    ALFALFA is a wide-area, blind 21cm survey of galaxies in the local universe (z<0.06), performed with the Arecibo radiotelescope. The latest public data release contains about 40% of the final 7000 sq.deg. survey sky coverage, and already contains the largest HI-selected galaxy sample to date. The combination of survey area and 21cm sensitivity of ALFALFA makes it ideal for addressing key questions in "near-filed" cosmology, such as the characteristics of the lowest mass galaxies and the properties of dark matter on sub-kpc scales. I will be presenting some recent results of the ALFALFA survey, relating to the properties of the lowest-mass field dwarf galaxies, the hunt for "missing satellites" and the clustering properties of HI-selected galaxies. The main focus of the talk will be on the recent statistical measurements of the abundance of galaxies as a function of their baryonic mass ("baryonic mass function of galaxies") and as a function of their rotational velocity ("velocity function of galaxies"). The former distribution can be used to infer the baryonic content (stars + neutral atomic gas) of dark matter halos, providing important constraints for hydrodynamic simulations of galaxy formation. The latter distribution can be used to test the halo mass function predicted by ΛCDM. In particular, a combined analysis of the abundance of low-mass galaxies and their internal gas kinematics may constitute an important new challenge of the standard cosmological model on galactic scales, corresponding to the field analog of the "too big to fail" ΛCDM challenge.
  • February 8, 2013 | 12:00 PM | LASR Conference Room
    Tracking Universe dynamics at large and small scales: cosmic voids and kSZ effects
    Guilhem Lavaux, University of Waterloo

    Non-linear phenomena has been insufficiently used to gather information on astrophysics and cosmology. I will present two examples of such phenomena that are particularly interesting to probe dynamics of the Universe on ultra large scale (expansion of the Universe) and large scale (bulk flows): cosmic voids and kinematic Sunyaev-Zel'dovich effect. First, we will see that cosmic voids are potentially interesting, theoretically and observationally, to probe the expansion and the energy content of the Universe. Second, I will show that kSZ can be more effectively detected by concentrating the effort on the plasma halo around galaxies, again highly non-linear, to probe large scale flows and locating missing baryons.
  • February 15, 2013 | 12:00 PM | LASR Conference Room
    Large-scale homogeneity vs. small-scale inhomogeneities: testing ΛCDM with large-scale structure
    Morag I Scrimgeour, University of Western Australia

    The most fundamental assumption of the standard cosmological model (ΛCDM) is that the Universe is homogeneous on large scales. This is not true on small scales, and some studies suggest that galaxies follow a fractal distribution up to very large scales (~200 h-1 Mpc or more), whereas ΛCDM predicts homogeneity at ~100 h-1 Mpc. We have tested this using the WiggleZ Dark Energy Survey, a UV-selected spectroscopic survey of ~200,000 luminous blue galaxies up to z=1, with the Anglo-Australian Telescope. The large volume and depth of WiggleZ allows us to probe the transition of the galaxy distribution to homogeneity on large scales, and see if this is consistent with a ΛCDM prediction. Conversely, the properties of small-scale inhomogeneities are an important probe of cosmology. The growth of primordial density perturbations to the large-scale structures present in the Universe today depends on the interplay between cosmic expansion and gravitational interaction. We use N-body simulations to investigate ways galaxy peculiar velocities, arising from these density inhomogeneities, can be used as an independent probe of cosmology.
  • February 22, 2013 | 12:00 PM | LASR Conference Room
    CHIME: 21cm and the Expanding Universe
    Keith Vanderlinde, U of Toronto

    The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is an ambitious new project designed to map the distribution of matter in the Universe, over half the sky and a broad swath of cosmic history. The newly-developed technique of Hydrogen Intensity (HI) mapping uses redshifted 21cm emission from neutral hydrogen as a 3D tracer of Large Scale Structure (LSS) in the Universe. Imprinted in the LSS is a remnant of the acoustic waves which propagated through the primordial plasma. This feature, the Baryon Acoustic Oscillation (BAO), manifests as a preferential separation scale between matter, and by charting the evolution of this scale over cosmic time, we can deduce the expansion history of the Universe. Leveraging recent developments from from the cell phone industry (cheap, low noise amplifiers) and the huge growth in digital processing power, CHIME will be a highly efficient "digital" radio telescope, a many-antenna physically-fixed structure where beams are formed and pointed through digital processing rather than with physically steered dishes or cable delays. CHIME is composed of five 20m x 100m parabolic reflectors which focus radiation in one direction (east-west), while interferometry is used to resolve beams in the other (north-south), and earth rotation is used to sweep them across the sky. I will discuss the motivation, design, and progress on both the full CHIME instrument and the 1/10th-scale Pathfinder which is currently under construction.
  • March 1, 2013 | 12:00 PM | LASR Conference Room
    Deficit Spending and the Cluster Baryon Budget
    Ann Zabludoff, University of Arizona / Steward Observatory

    The deep gravitational potential wells of clusters of galaxies should capture fair samples of the total baryon fraction of the Universe, unless other physical processes drive baryons out of clusters. Thus precision measurements of the baryon fraction, particularly as a function of cluster halo mass, can reveal the history of baryon flux into and out of clusters. How those baryons are then apportioned between stars and intracluster gas --- the star formation efficiency --- informs models of cluster assembly and massive galaxy evolution, as well as efforts to use the cluster gas fraction to constrain the mass density and dark energy equation of state parameters. Even the partitioning of the stellar baryons alone, in and out of galaxies, tests models of cluster galaxy evolution, as intracluster stars are the final, unambiguous signature of stars stripped from cluster galaxies. We have discovered that intracluster stars are a significant part of the stellar baryons in clusters and poorer groups of galaxies. I will present new work characterizing the properties of this previously unexplored component, as well as the consequences for the cluster baryon budget and its relationship to the Universal WMAP value.
  • March 8, 2013 | 12:00 PM | LASR Conference Room
    Gaussianization: How to Deal with Wrinkles in the Universe
    Mark C. Neyrinck, Johns Hopkins University

    Structures (''wrinkles'') in the Universe like filaments and haloes are essential components of the arrangement of matter on large scales. They form in analogy to the origami-folding of a sheet of dark-matter. While these structures are fascinating, and conveniently allow observers like us to exist, they also make it harder to extract cosmological information on nonlinear scales. In particular, sharp peaks greatly diminish the power of statistics in cosmology. I will discuss how largely to fix them with Gaussianization.
  • March 22, 2013 | 12:00 PM | LASR Conference Room
    Gravitational Wave Telescopes, Time-Delay Interferometers and Choreographic Crystals
    Latham Boyle, Perimeter Institute

    I will present three interesting problems with neat solutions. All three come from thinking about gravitational wave detection; but the latter two are actually of broader interest. The first problem is how to arrange a handful of gravitational wave detectors to obtain the best gravitational wave telescope. In the second problem, we imagine a collection of "nodes" (e.g. satellites) exchanging laser signals, and want to know how to construct interferometric observables that are insensitive to the phase fluctuations of the lasers. Finally, the third problem begins with the question: what is the most symmetrical arrangement of 4 satellites orbits? This simple question is the doorway to the interesting subject of choreographic crystals, which I will introduce.

 
SPECIAL SEMINARS

  • March 4, 2013 | 1:30 PM | LASR Conference Room
    Thermal Detectors: Recent Applications, Lessons Learned, and Future Directions
    Bradford Benson, The University of Chicago

    Thermal detectors play a key role in astronomy, perhaps most notably at far-infrared to mm-wavelengths where continued advances have, on-average, caused focal plane sensitivities to approximately double each year over the last 50 years. These technological advances have driven new scientific results on star formation, the cosmic infrared background (CIB), and cosmic microwave background (CMB), with new measurements poised to make significant advances in our understanding of galaxy formation, cosmic reionization, neutrinos, dark energy, and inflation. I will review the development of thermal detectors over the last 20 years; from hand-made absorber-coupled bolometers using neutron transmuted doped (NTD) germanium semiconductors; to superconducting transition edge sensor (TES) bolometer arrays made entirely using thin-film deposition and optical lithography; to superconducting antenna-coupled arrays integrated with micro-strip and filter technology. Finally, I will discuss the design of new detectors for planned and potential next-generation CMB experiments, and low-resolution optical and mm-wavelength spectrometers.
  • March 11, 2013 | 1:30 PM | LASR Conference Room
    A path toward the detection of CMB B-mode polarization from primordial gravitational waves
    Akito Kusaka, Princeton University

    Cosmic microwave background (CMB) polarization is the ultimate probe of primordial gravity waves in the early universe, via the B-mode (or parity odd) signal on degree angular scales. A detection of such a signal would provide strong evidence of the inflation scenario and constitute the first observational connection between quantum physics and gravity. In this talk, I describe three experiments with very different instrumental architecture: QUIET, ABS, and MuSE, a novel B-mode experiment using highly multimoded detectors. In particular, I will discuss how the proposed multimoded architecture can attain competitive sensitivity and polarization systematics control, and complements the development of single-mode bolometers. The diverse approach in the instrument development is critically important in order to detect the subtle B-mode signal with the instrumental systematics and the galactic foregrounds well understood.
  • March 12, 2013 | 1:30 PM | LASR Conference Room
    Probing the dark ages at mm-wavelengths with SuperSpec, an MKID-based spectrometer-on-a-chip
    Erik Shirokoff, Caltech

    Recent advances in detector technology have enabled precision studies of the Cosmic Microwave Background and many sub-mm sources; however, resolving the majority of the galaxies at z>6 responsible for reionization remains a challenge. One promising means of studying this population is through spectroscopic surveys of 158 um [CII] emission redshifted to mm wavelengths, either through pointed observations of individual galaxies or in tomographic maps of unresolved sources. These observations will require sensitive multi-object spectrometers such as SuperSpec. SuperSpec is a novel, ultra-compact spectrometer-on-a-chip for millimeter and submillimeter wavelength astronomy. Its very small size, wide spectral bandwidth, and highly multiplexed detector readout will enable construction of powerful multibeam spectrometers for high-redshift observations. SuperSpec employs a filter bank consisting of planar, lithographed superconducting transmission line resonators. Each mm-wave resonator is coupled to a lumped element, titanium-nitride Microwave Kinetic Inductance Detector (MKID). I will discuss the design and optimization of the mm-wave circuit and MKIDs as well as measurements of laboratory prototypes. I'll also describe the ongoing development of several experiments which employ this technology, including a two-pixel demonstration camera currently under construction and a proposed multi-object spectrometer for the CCAT telescope, X-Spec.
  • March 13, 2013 | 10:45 AM | LASR Conference Room
    Superconducting technology and New Windows into Cosmic Relics
    Clarence Chang, Argonne National Lab/The University of Chicago

    Advances in superconducting Transition Edge Sensors (TES) are enabling new measurements relevant for understanding the Cosmic Neutrino Background (CvB). I will discuss how TES technology is enabling indirect measures of the CvB through ground-breaking measurements of the Cosmic Microwave Background (CMB) radiation with the South Pole Telescope (SPT), a 10-m mm-wave observatory at the geographic South Pole. In 2011, the SPT completed a 2500 sq deg survey using a TES bolometer focal plane. The unprecedented combination of sensitivity, area, and resolution of this survey enables an exciting program of cosmological measurement. Among the spectrum of new cosmological results are interesting insights into the existence and properties of the CvB. TES detectors are also the core technology for the SPTpol instrument, a CMB polarimeter recently deployed on the SPT in 2012. I will provide an update on the performance of SPTpol and discuss its potential for probing the CvB via measurement of the elusive CMB ''B-modes.'' I will also outline plans for SPT's third generation TES-based focal plane, SPT-3G. Measurements by SPT-3G will explore the CvB at a level that is potentially relevant for understanding the neutrino mass hierarchy. Finally, I will discuss a new implementation of TES detectors as part of the PTOLEMY (Princeton Tritium Observatory for Light, Early-universe, Massive-neutrino Yield) experiment. PTOLEMY will detect CvB neutrinos through capture on Tritium providing a direct measure of the CvB.
  • March 15, 2013 | 12:00 PM | LASR Conference Room
    Low-Temperature Detector Development to Further X-ray Astrophysics
    Megan Eckart, NASA/GSFC

    High-resolution imaging spectroscopy in the soft x-ray waveband (0.1-10 keV) is an essential tool for probing the physics of the x-ray universe. Unique line diagnostics available in this waveband allow transformative scientific observations of a wide array of sources. For example, measurements of turbulence in the intra-cluster medium of galaxy clusters can be used to calibrate hydrodynamic simulations used in cosmology; and measurements of outflow processes from supermassive black holes may identify the key mechanism that regulates the co-evolution of host galaxies and their central black holes. I will introduce the microcalorimeter, a low-temperature detector capable of x-ray photon counting with high spectral resolution, and I will talk about the scientific potential of upcoming space-based experiments using arrays of such detectors, including the Soft X-ray Spectrometer, a pioneering microcalorimeter instrument that will launch aboard the Japanese-led Astro-H mission in 2015. I will discuss our recent advances using transition-edge-sensor microcalorimeters, including new insights into the operational physics of these superconducting-based devices; breakthroughs enabled by using novel device architectures; and the first demonstrations of kilopixel detector arrays. Finally, I will identify areas in detector, readout, and instrument development that are important for next-generation instrumentation for space- and laboratory-based experiments.

 
ASTRONOMY COLLOQUIA

  • January 16, 2013 | 3:30 PM | BSLC 115
    Imaging instruments for the cosmic frontier
    Juan Estrada, Fermilab

    This talk reviews the current technology used for wide field optical imaging in astronomy, with emphasis in the recently commissioned Dark Energy Camera. This technology has enabled new experiments in the cosmic frontier that are starting to produce results now. Finally, during this talk, I discuss how this field is transforming to allow future astronomical instruments with unprecedented scientific potential.
  • January 30, 2013 | 3:30 PM | BSLC 115
    Neutron Star Radii and Masses
    Feryal Ozel, University of Arizona

    Neutron stars offer the unique possibility of probing the equation of state of cold, ultradense matter. Understanding the properties of the neutron star interior is also important for predicting the observational appearance of short gamma-ray bursts, the end stages of neutron star coalescence, and the outcomes of supernova explosions. I will present the recent measurements of neutron star radii and masses. I will show how the combination of the tightly constrained radii and the discovery of a 2 solar mass pulsar allows for the first astrophysical inference of the pressure of cold matter above nuclear saturation density. I will discuss the implications of this measurement for nuclear theory and astrophysics.
  • February 6, 2013 | 3:30 PM | BSLC 115
    Towards ab initio simulations of star formation in turbulent molecular clouds
    Alexei Kritsuk, University of California, San Diego

    Understanding how molecular clouds form in the interstellar medium and how they evolve to produce dense cores that eventually give birth to stars is an important unsolved problem in star formation. From a theoretical perspective, star formation is a challenging multi-scale problem that involves complex nonlinear interactions of gravity, turbulence, magnetic fields, radiation and feedback processes. I shall describe a self-consistent computational framework for modeling molecular cloud formation in the multiphase ISM as a first step to generate realistic initial conditions for star formation. Our approach is based on self-organization in the turbulent ISM and, with only a few control parameters, numerical experiments successfully reproduce the observed probability distributions of the molecular gas density, thermal pressure, magnetic field strength, as well as the core mass function. I shall briefly discuss the origin of Larson's scaling relations that naturally emerge in the model.
  • February 20, 2013 | 3:30 PM | BSLC 115
    Gamma-ray detections of cosmic-ray acceleration by supernova remnants
    Elizabeth Hays, NASA

    Supernova remnants have been considered prime suspects as accelerators of cosmic rays within our Galaxy for a long time. Gamma-ray observations have offered the promise of turning that suspicion into certainty for almost as long, but only recently high-energy gamma-ray telescopes, both the Fermi Large Area Telescope and AGILE, have provided data that can be used to look for direct evidence of protons in these sources. I will present the new results from Fermi that reveal the proton signature in two supernova remnants and put this in context with the growing catalog of GeV remnants detected by LAT and the remaining questions to be answered about Galactic cosmic rays.
  • March 13, 2013 | 3:30 PM | BSLC 115
    The Road to 100 Earths
    Debra Fischer, Yale University

    The search for planets orbiting nearby stars has been one of the greatest success stories of the past decade, with hundreds of discoveries being made using Doppler, transit, microlensing, and direct imaging techniques. More than 2300 candidates have been detected with NASA's Kepler mission. Exoplanet detections have launched a subfield of astronomy that includes host star characterizations, measurements of planet radii and density, studies of atmospheres, interior structure, formation theory, and orbital evolution. The search for exoplanets is motivated by the question of whether life exists elsewhere. This drives our interest in the detection of planets that are similar to our own world: rocky planets with the potential for liquid surface water and plate tectonics; worlds that might harbor life that we can recognize. Importantly, we will need to discover not just a few, but hundreds of these worlds to eventually gain a statistical understanding of whether life is rare, common, or ubiquitous and ground-based telescopes offer an ideal platform for carrying out decade-long surveys. It is critical for follow-up studies (imaging, atmospheric studies) that these planets orbit nearby stars rather than stars at distances of the typical Kepler field star. In this talk, I will discuss how we plan to take what we've learned and push on to the next frontier: a search 100 Earths.

 
ASTRONOMY SPECIAL SEMINARS

  • March 4, 2013 | 1:30 PM | LASR Conference Room
    Thermal Detectors: Recent Applications, Lessons Learned, and Future Directions
    Bradford Benson, University of Chicago

    Thermal detectors play a key role in astronomy, perhaps most notably at far-infrared to mm-wavelengths where continued advances have, on-average, caused focal plane sensitivities to approximately double each year over the last 50 years. These technological advances have driven new scientific results on star formation, the cosmic infrared background (CIB), and cosmic microwave background (CMB), with new measurements poised to make significant advances in our understanding of galaxy formation, cosmic reionization, neutrinos, dark energy, and inflation. I will review the development of thermal detectors over the last 20 years; from hand-made absorber-coupled bolometers using neutron transmuted doped (NTD) germanium semiconductors; to superconducting transition edge sensor (TES) bolometer arrays made entirely using thin-film deposition and optical lithography; to superconducting antenna-coupled arrays integrated with micro-strip and filter technology. Finally, I will discuss the design of new detectors for planned and potential next-generation CMB experiments, and low-resolution optical and mm-wavelength spectrometers.
  • March 11, 2013 | 1:30 PM | LASR Conference Room
    A path toward the detection of CMB B-mode polarization from primordial gravitational waves
    Akito Kusaka, Princeton University

    Cosmic microwave background (CMB) polarization is the ultimate probe of primordial gravity waves in the early universe, via the B-mode (or parity odd) signal on degree angular scales. A detection of such a signal would provide strong evidence of the inflation scenario and constitute the first observational connection between quantum physics and gravity. In this talk, I describe three experiments with very different instrumental architecture: QUIET, ABS, and MuSE, a novel B-mode experiment using highly multimoded detectors. In particular, I will discuss how the proposed multimoded architecture can attain competitive sensitivity and polarization systematics control, and complements the development of single-mode bolometers. The diverse approach in the instrument development is critically important in order to detect the subtle B-mode signal with the instrumental systematics and the galactic foregrounds well understood.
  • March 12, 2013 | 1:30 PM | LASR
    Probing the dark ages at mm-wavelengths with SuperSpec, an MKID-based spectrometer-on-a-chip
    Erik Shirokoff, Caltech

    Recent advances in detector technology have enabled precision studies of the Cosmic Microwave Background and many sub-mm sources; however, resolving the majority of the galaxies at z>6 responsible for reionization remains a challenge. One promising means of studying this population is through spectroscopic surveys of 158 um [CII] emission redshifted to mm wavelengths, either through pointed observations of individual galaxies or in tomographic maps of unresolved sources. These observations will require sensitive multi-object spectrometers such as SuperSpec. SuperSpec is a novel, ultra-compact spectrometer-on-a-chip for millimeter and submillimeter wavelength astronomy. Its very small size, wide spectral bandwidth, and highly multiplexed detector readout will enable construction of powerful multibeam spectrometers for high-redshift observations. SuperSpec employs a filter bank consisting of planar, lithographed superconducting transmission line resonators. Each mm-wave resonator is coupled to a lumped element, titanium-nitride Microwave Kinetic Inductance Detector (MKID). I will discuss the design and optimization of the mm-wave circuit and MKIDs as well as measurements of laboratory prototypes. I'll also describe the ongoing development of several experiments which employ this technology, including a two-pixel demonstration camera currently under construction and a proposed multi-object spectrometer for the CCAT telescope, X-Spec.
  • March 13, 2013 | 10:45 AM | LASR Conference Room
    Superconducting Technology and Measuring the Cosmic Neutrino Background
    Clarence Chang, University of Chicago/Argonne

    Advances in superconducting Transition Edge Sensors (TES) are enabling new measurements relevant for understanding the Cosmic Neutrino Background (CvB). I will discuss how TES technology is enabling indirect measures of the CvB through ground-breaking measurements of the Cosmic Microwave Background (CMB) radiation with the South Pole Telescope (SPT), a 10-m mm-wave observatory at the geographic South Pole. In 2011, the SPT completed a 2500 sq deg survey using a TES bolometer focal plane. The unprecedented combination of sensitivity, area, and resolution of this survey enables an exciting program of cosmological measurement. Among the spectrum of new cosmological results are interesting insights into the existence and properties of the CvB. TES detectors are also the core technology for the SPTpol instrument, a CMB polarimeter recently deployed on the SPT in 2012. I will provide an update on the performance of SPTpol and discuss its potential for probing the CvB via measurement of the elusive CMB ''B-modes.'' I will also outline plans for SPT's third generation TES-based focal plane, SPT-3G. Measurements by SPT-3G will explore the CvB at a level that is potentially relevant for understanding the neutrino mass hierarchy. Finally, I will discuss a new implementation of TES detectors as part of the PTOLEMY (Princeton Tritium Observatory for Light, Early-universe, Massive-neutrino Yield) experiment. PTOLEMY will detect CvB neutrinos through capture on Tritium providing a direct measure of the CvB.
  • March 14, 2013 | 2:00 PM | LASR
    Monolithic Microwave Integrated Circuits for Experimental Astrophysics
    Roger O'Brient, Caltech

    The rapid progress in millimeter and submillimeter astronomy over the past decade has been driven by our ability to deploy large imaging arrays of background noise limited detectors. I will discuss how the degree-scale Keck Array has ridden this detector-driven boost in sensitivity to become the most sensitive CMB-polarimeter in operation, uniquely positioning it to place unprecedented constraints on inflation. Over the next year, additional small aperture cameras in SPIDER and BICEP-3 will come online with similar sensitivity and the ability to spectrally discriminate foregrounds from the CMB. I will further discuss how larger aperture experiments such as SPT and Polarbear will scale up their detector count through multichroic pixels. This technology will let them measure weak CMB lensing in a way that complements the Keck Array/BICEP-3 while additionally constraining the Dark Energy equation of state and the mass hierarchy of the neutrinos. I will conclude with a description of how these multichroic pixels could be naturally extended to allow us to probe the epoch of reionization through tomographic mapping of CII emissions from that era.
  • March 15, 2013 | 12:00 PM | LASR Conference Room
    Low-temperature Detector Development to Further our Understanding of the X-ray Universe
    Megan Eckart, NASA GSFC

    High-resolution imaging spectroscopy in the soft x-ray waveband (0.1-10 keV) is an essential tool for probing the physics of the x-ray universe. Unique line diagnostics available in this waveband allow transformative scientific observations of a wide array of sources. For example, measurements of turbulence in the intra-cluster medium of galaxy clusters can be used to calibrate hydrodynamic simulations used in cosmology; and measurements of outflow processes from supermassive black holes may identify the key mechanism that regulates the co-evolution of host galaxies and their central black holes. I will introduce the microcalorimeter, a low-temperature detector capable of x-ray photon counting with high spectral resolution, and I will talk about the scientific potential of upcoming space-based experiments using arrays of such detectors, including the Soft X-ray Spectrometer, a pioneering microcalorimeter instrument that will launch aboard the Japanese-led Astro-H mission in 2015. I will discuss our recent advances using transition-edge-sensor microcalorimeters, including new insights into the operational physics of these superconducting-based devices; breakthroughs enabled by using novel device architectures; and the first demonstrations of kilopixel detector arrays. Finally, I will identify areas in detector, readout, and instrument development that are important for next-generation instrumentation for space- and laboratory-based experiments.