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Colloqiua & Seminars
Fast Radio Bursts!
Albert Stebbins, Fermilab
On a human scale most astronomical sources are large and vary slowly. They must be large enough to produce enough light be to seen at astronomical distances and the light travel time across a large source limits the timescale for observable variations. Nevertheless in recent years extremely rapidly varying radio emission has been detected and found to be a common phenomena. The most extreme case has timescales as small as one nanosecond, inferred size smaller than one meter, peak luminosity exceeding that of the Sun, and is observed at a distance of 2kpc. More numerous and further away are Fast Radio Bursts (FRBs), originating at cosmological distances, lasting a millisecond and arriving at Earth a few times a minute. These events are the brightest sources known in terms of an off-scale brightness temperature, yet the emission mechanism is undetermined. I will discuss some ideas for the origin of this emission and how these bright bursts could be used to augment gravitational wave and neutrino astronomy as well as the study of cosmological parameters and the intergalactic medium.
Observing, Mapping and Mocking our Cosmic Beginnings
J. Richard Bond, Canadian Institute for Theoretical Astrophysics, University of Toronto
I will give my take on the phenomenology (and yes theory) of inflation as revealed in Planck and other CMB) and LSS experiments, but with an eye to the glorious CMB future of AdvACT, CCAT-p, Simons Observatory, Stage 4, and the LSS of Euclid, Chime, and much more besides that we mock. Apart from displaying linear and quadratic maps of the primordial universe, a compression of what we now know, i will chat about CMB/LSS anomalies, in practice and in theory, pointing to post-inflation chaotic dynamical systems that can lead to subdominant non-Gaussian signals unlike the ones we have put such stringent constraints on with Planck 2015; and relate everything to non-equilibrium entropies, including the formation of all cosmic structure.
News from PICO and COHERENT
Juan I. Collar, University of Chicago
I will discuss the most recent results from PICO, a search for WIMP dark matter using bubble chambers, as well as future plans and some exciting lines of related research. I will then move on to cover COHERENT, an ongoing effort at ORNL's Spallation Neutron Source to detect and exploit coherent neutrino-nucleus scattering, soon to produce first results. The "glue" between these two subjects will be an elaboration on the overlap in techniques and methods used in modern neutrino and astroparticle physics. Abundant examples of this cross-talk will be provided.
The Milky Way's Dark Companions
Alex Drlica-Wagner, Fermilab
PDF | Video
Our Milky Way galaxy is surrounded by a host of small, dark-matter-dominated satellite galaxies. Over the past two years, the Dark Energy Camera (DECam) has nearly doubled the number of known Milky Way satellite galaxies compared to the previous 80 years combined. While these discoveries continue to help resolve the "missing satellites problem", they have also raised new questions about the influence of the Magellanic Clouds on the Milky Way's satellite population. In the near future, the rapidly growing population of dwarf galaxies will be sensitive to deviations from ΛCDM at small scales, while definitively testing whether the annihilation of dark matter particles could be responsible for excess gamma-ray emission from the Galactic center. I will summarize recent results, outstanding questions, and upcoming advancements in the study of the Milky Way's dark companions.
Increasing Accuracy and Increasing Tension in H0
Wendy Freedman, KICP
PDF | Video
The accuracy in direct measurement of distances to galaxies has continued to improve dramatically over the past decade. Local measurements of the Hubble constant based on Hubble Space Telescope observations of astrophysical standard candles -- Cepheids and Type Ia supernovae -- have converged on a value of about 73 km/sec/Mpc with an uncertainty of 2-3%. At the same time, estimates assuming a Lambda-CDM standard model and fitting highly precise measurements of cosmic microwave background fluctuations have yielded a value of Ho = 67 km/sec/Mpc. The two methods disagree at approximately the 3-sigma level. The reason for this discrepancy is not understood at present, and new data have only increased the tension. If real, the disagreement could be signaling missing physics in the standard model; for example, additional dark radiation. Major efforts are ongoing to improve further the accuracy in the local measurements, including developing other techniques to test the Cepheid distance scale. In the near future JWST and Gaia will provide a path to measuring Ho to 1%, comparable to the precision in CMB measurements.
New Directions in Searching for the Dark Universe
Surjeet Rajendran, UC Berkeley
PDF | Video
Observational bounds currently permit the existence of a large number of dark matter candidates, ranging from ultra-light axions with masses ~ 10^(-22) eV to MACHOs with mass as large as 10^(24) gm. It is important to develop experimental methods to constrain this vast range of parameters. In this talk, I will describe new experimental methods to probe a wide variety of dark matter candidates, ranging from ultra-light axions with masses ~ 10^(-22) eV to light WIMPs with mass in the keV - GeV range. A variety of precision measurement technologies such as optical/atomic interferometry and SQUID magnetometry can be applied to search for these particles. I will also discuss methods to search for the direction of the nuclear recoil induced by conventional WIMP scattering in detectors with solid state densities. These directional detectors may enable probes of conventional WIMP dark matter beyond the solar neutrino floor.
The First Four Months of Gravitational Wave Astronomy
Ben Farr, Enrico Fermi Institute and KICP
PDF | Video
On September 14, 2015 LIGO made the first direct detection of gravitational waves, marking the beginning of gravitational wave astronomy. The LIGO instruments continued to take data over the next four months, completing their first observing run on January 19, 2016 with 51.5 days of coincident data. I will present results from advanced LIGO's first four months of operation, and what they have taught us thus far.
The Dark Energy Survey and Gravitational Waves
Marcelle Soares-Santos, Fermilab
PDF | Video
In this talk I present recent results of the Dark Energy Survey (DES) searches for optical counterparts to Gravitational Wave (GW) events detected by the LIGO/Virgo Collaboration. Our program achieved greater sensitivity than any other optical facility last year. For the second observing campaign (Fall/2016-Spring/2017) our goals are to either make a detection or establish significant constraints on optical emission from such events. DES is the greatest optical imaging survey yet, aiming at percent-level precision measurements of cosmological parameters from a combination of probes such as type Ia supernovae, galaxy clusters, and weak gravitational lensing. These probes are limited by astrophysical systematics and new independent methods are required in order to beat systematic effects down to sub-percent levels. Standard sirens, events for which distances are determined from their gravitational wave signal, are one possible new method to meet that challenge. Our program will potentially have a great impact in our field by exploring this possibility from the observational perspective. In this talk I will also briefly discuss this exciting prospect for future observing campaigns.