ASD Colloquium Series - Spring 2018

ASD Colloquium Series - Spring 2018

The Astrophysics Science Division colloquia occur on Tuesdays at 3:45 pm, with an opportunity to meet the speaker at 3:30 pm, in building 34, room W150 (unless otherwise noted). Schedules from past colloquium seasons are available.

Contact: Eric Switzer


Jan 9 No Colloquium - AAS
Jan 16 No Colloquium - MLK Holiday
Jan 23 Elisabetta Cavazzuti (GSFC) - "Fermi Large Area Telescope and its recent results on Active Galactic Nuclei"
Jan 30 Rachel Mandelbaum (CMU) - "Cosmology with the HSC Survey"


Feb 6 Omid Noroozian (NRAO) - "Astronomy with Superconductors: A Review of Current and Upcoming Photon Detector Technologies"
Feb 13 Susan Mullally Thompson (STScI) - "Kepler’s Final Planet Catalog"
Feb 20 Silvia Piranomonte (INAF/Rome) - "GW170817 Optical/NIR Follow-up Observations: The First Evidence of Kilonovae Existence"
Feb 27 Thomas Reiprich (Bonn) - "Cosmology with X-ray Galaxy Clusters"


Mar 6 Mark Swain (JPL)
Mar 13 Special Location: Building 3, Goett Auditorium
Garth Illingworth (UCSC/Lick) - "Galaxies at Cosmic Dawn: Exploring the First Billion Years with Hubble and Spitzer - Implications for JWST"
Mar 20 Sally Heap (GSFC)
Mar 27 Dan Huber (IfA/Hawaii) - "Asteroseismology & Exoplanets in the TESS Era"


Apr 3 Brad Peterson (STSci and Ohio State) - "Exploring the Inner Structure of Active Galactic Nuclei by Reverberation"
Apr 10 Jamie Bock (JPL)
Apr 17 Jack Singal (Richmond) - "The Radio Synchrotron Background: Recent Reckonings"
Apr 24 Marcelle Soares-Santos (Brandeis)


May 1 Katie Freese (UMich)
May 8 Dara Norman
May 15 Jeremy Kasdin (Princeton)
May 22 Jillian Bellovary (QCC/CUNY)
May 29 No Colloqium - Memorial Day


Jun 5 Special Date
Katie Breivik
Jun 12 No Colloqium - SPIE

"Fermi Large Area Telescope and its recent results on Active Galactic Nuclei"

Elisabetta Cavazzuti


Tuesday, Jan 23, 2018


The Fermi Gamma-ray Space Telescope has operated for more than 9 years and provided unprecedented information about many source classes, including Active Galactic Nuclei. I will review the most recent results and milestones concerning this apparently well-known source class. Although these broad-band, bright objects are extensively studied across the entire electromagnetic spectrum, we still do not understand their intrinsic nature, and new paradigms are being explored.

"Cosmology with the HSC Survey"

Rachel Mandelbaum


Tuesday, Jan 30, 2018


Hyper Suprime-Cam (HSC) is an imaging camera mounted at the Prime Focus of the Subaru 8.2-m telescope operated by the National Astronomical Observatory of Japan on the summit of Mauna Kea in Hawaii. A consortium of astronomers from Japan, Taiwan and Princeton University is carrying out a three-layer, 300-night, multiband survey from 2014-2019 with this instrument. In this talk, I will focus on the HSC survey Wide Layer, which will cover 1400 square degrees in five broad bands (grizy), to a 5 sigma point-source depth of r~26. We have covered 240 square degrees of the Wide Layer in all five bands, and the median seeing in the i band is 0.60 arcseconds. This powerful combination of depth and image quality makes the HSC survey unique compared to other ongoing imaging surveys. In this talk I will describe the HSC survey dataset and the completed and ongoing science analyses with the survey Wide layer, including galaxy studies, strong and weak gravitational lensing, but with an emphasis on weak lensing. I will demonstrate the level of systematics control, the potential for competitive cosmology constraints, some early results, and describe some lessons learned that will be of use for other ongoing and future lensing surveys.

"Astronomy with Superconductors: A Review of Current and Upcoming Photon Detector Technologies"

Omid Noroozian


Tuesday, Feb 6, 2018


Technological advances in photon detectors, spectrometers, and amplifiers have enabled increasingly more powerful telescopes, and have been at the heart of new scientific discoveries. New detector technologies have enabled entirely new observational possibilities that had not been previously considered in the design of science studies. In this talk I will review, across the electromagnetic spectrum (with some focus in the Submm/Far-IR), the state-of-the-art detector technologies that involve the use of one of nature’s strangest properties, namely superconductivity. Kinetic Inductance Detectors, Transition Edge Sensors, Quantum Capacitance Detectors, Traveling-Wave Parametric Amplifiers, on-chip spectrometers, and heterodyne receivers are all exciting technologies that will play a key role in future space and ground-based facilities, such as the Origins Space Telescope (OST), SPICA, Atacama Large-Aperture Submm/mm Telescope (AtLAST), CMB-S4, and upgrades to current facilities such as ALMA. Their science impact ranges from exoplanet atmospheric studies and protoplanetary disk evolution to large-scale spectroscopic surveys of high-z galaxies.

"Kepler’s Final Planet Catalog"

Susan Mullally Thompson


Tuesday, Feb 13, 2018


The Kepler mission spent four years staring at the same patch of sky, in half hour increments, in order to catch the small, periodic decreases in brightness caused by a planet transiting its host star. Kepler caused a revolution in planet discoveries by enabling the discovery of a variety of planets, including rocky planets and planets in the habitable zone of their stars. However, the true goal of Kepler was to enable a statistical census of planets, especially those planets that are similar to the Earth. Since the Kepler spacecraft stopped taking data in 2013, this effort has continued by understanding the data characteristics, improving the data processing pipeline, and doing one final search of the data for transiting exoplanets. The culmination of that effort is the DR25 planet candidate catalog. To produce this final planet candidate catalog we automated the entire search, from time series pixel data to planet candidates. By feeding the this fully automated pipeline a set of simulated signals we could directly test our pipeline and determine how much the catalog was contaminated by noise and account for how many plants were missed. In this talk I will give an overview of the Kepler mission and what it has added to our understanding of exoplanets, how the final planet catalog was designed to determine the frequency of small, long-period planets and what challenges remain in using this catalog to determine the frequency of Earth-like planets in our Galaxy.

"GW170817 Optical/NIR Follow-up Observations: The First Evidence of Kilonovae Existence"

Silvia Piranomonte


Tuesday, Feb 20, 2018


On August 17th 2017 the first electromagnetic counterpart of a gravitational wave (GW) event originated by the coalescence of a double neutron star system (GW 170817, Abbott et al. 2017) was finally observed. A world-wide extensive observing campaign was carried out to follow-up and study this source In this talk I will describe our unique spectroscopic dataset acquired with the VLT which allowed to characterize and identify the optical counterpart of GW 170817 as the first compelling example of a "kilonova", a transient source powered by radioactive decay of heavy elements resulting from the r-process nucleosynthesis of ejected neutron star matter. All the activities I will describe are expected to provide means and opportunities to all the European astronomical communities to have a leading role in the GW astronomy and Time Domain Astronomy.

"Cosmology with X-ray Galaxy Clusters"

Thomas Reiprich


Tuesday, Feb 27, 2018


The massive dark matter halos that host galaxy clusters can be well traced by X-ray satellite observatories. The intracluster gas trapped in the deep potential wells gets heated to 10s of millions of Kelvin, emitting thermal bremsstrahlung at X-ray wavelengths. The latest cosmological constraints from X-ray selected galaxy clusters will be discussed. A new test to constrain the cosmological luminosity distance anisotropy using galaxy clusters is introduced and results indicating a violation of isotropy are shown. New X-ray selected very extended nearby galaxy groups and clusters have been discovered in ROSAT All-Sky Survey images at positions where no X-ray source was found previously; the properties of the cluster candidate sample (~1,000 in total) and implications for cosmological constraints from clusters are discussed. The current status of and prospects for the eROSITA telescope to be launched aboard the SRG mission in about one year are outlined. The expectations for the ESA L-class mission Athena to discover and characterize early galaxy groups, massive and evolved enough to contain $>$10 million Kelvin gas, above redshift 2 are quantified.

"Galaxies at Cosmic Dawn: Exploring the First Billion Years with Hubble and Spitzer - Implications for JWST"

Garth Illingworth


Tuesday, Mar 13, 2018


Hubble has revolutionized the discovery and study of the earliest galaxies through its exploration of the universe in the first billion years after the Big Bang. I will discuss what we have learned about galaxies during that epoch at redshift z>6 from the remarkable HST and Spitzer imaging surveys (e.g., GOODS, HUDF/XDF, HUDF09/12 and CANDELS), as well as surveys of lensing galaxy clusters (e.g., the Hubble Frontier Fields - HFF). Lensing clusters provide extraordinary opportunities for characterizing the faintest earliest galaxies, but also present extraordinary challenges. Analysis of early galaxies found in the HFF images reveal compact star-forming regions that, remarkably, can be as small as today's globular clusters and dwarf galaxies. The results from deep surveys with Hubble, combined with the recent results from Planck, indicate that galaxies dominated the UV ionizing flux that reionized the universe. One of the greatest surprises came from the discovery of very luminous galaxies at redshifts z~11 to z~8, just 400 to 650 million years after the Big Bang. Hubble and Spitzer recently encroached on JWST territory by looking back through 97% of all time to confirm a z~11.1 galaxy. This is far beyond what we ever expected Hubble and Spitzer could do. Twenty years of astonishing progress with Hubble and Spitzer leave me looking to JWST to provide even more remarkable exploration of the realm of the first galaxies. I will discuss how the latest Hubble and Spitzer results on the sizes of star-forming regions in distant galaxies, on the star formation rate at redshift z~10, and from Planck indicating that reionization began around z~10, together have significant implications for the detectability of the "first galaxies" with JWST.

"Exploring the Inner Structure of Active Galactic Nuclei by Reverberation"

Brad Peterson

Space Telescope Science Institute and The Ohio State University

Tuesday, Apr 3, 2018


The innermost structure of active galactic nuclei (AGNs) consists of an accretion disk surrounding a supermassive black hole and, on somewhat larger scales, rapidly moving diffuse gas. The ultraviolet through near IR spectrum of AGNs is dominated by thermal continuum emission from the accretion disk and broad emission lines and absorption features from the diffuse gas. The continuum flux from the accretion disk varies with time, and the emission lines also change in brightness, or “reverberate,” in response to these variations, with a delay due to the light-travel time across the line-emitting region. Measurement of the emission-line time delay yields the size of the line-emitting region and by combining this with the emission-line Doppler width, the central black hole mass can be inferred. I will discuss results from recent “reverberation mapping” experiments, including a 179-orbit Hubble Space Telescope program, that have been designed to explore the dynamics of the emission-line gas and are yielding a wealth of new and quite surprising information about AGN structure.

"The Radio Synchrotron Background: Recent Reckonings"

Jack Singal


Tuesday, Apr 17, 2018


It has become increasingly clear that there is profound tension between measurements of the background level of diffuse radio emission on our sky on the one hand and the integrated surface brightness expected from extragalactic source counts of known populations and most reasonable models of the Galactic halo on the other. These seemingly irreconcilable results represent a mystery in astrophysics, and make studies of the radio background fundamentally unlike those at infrared, optical/UV, X-ray, and gamma-ray wavelengths where the source populations are well characterized and understood, and trace the known large scale structure of the Universe. This talk will review the measurements of the radio synchrotron monopole level, and the constraints on properties of extragalactic radio sources and on Galactic diffuse emission. We will then present the ideas for paths forward and future measurements that were arrived at a recent international workshop on the topic.

Past Colloqia Schedules

2018: Spring
2017: Fall, Spring
2016: Fall, Spring
2015: Fall, Spring
2014: Fall, Spring
2013: Fall, Spring, Summer
2012: Fall, Spring
2011: Fall, Spring
2010: Fall, Spring

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