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Organized by: Prof. Lu Lu

Events During the Week of February 7th through February 14th, 2016

Monday, February 8th, 2016

No events scheduled

Tuesday, February 9th, 2016

No events scheduled

Wednesday, February 10th, 2016

No events scheduled

Thursday, February 11th, 2016

The Atacama B-mode Search: Cosmology at 17,000 Feet
Time: 2:30 pm - 3:00 pm
Place: 5280 Chamberlin Hall
Speaker: Sara Simon, Princeton
Abstract: The Atacama B-mode Search (ABS) was a crossed-Dragone telescope located at an elevation of 5200 m in the Atacama Desert in Chile that observed the cosmic microwave background (CMB) from February 2012 until October 2014. ABS was a pathfinder experiment that searched for the primordial B-mode polarization signal at large angular scales from multipole moments of l~40 to l~500, where it is expected to peak. The ABS focal plane consisted of 240 pixels sensitive to 145 GHz, each containing two transition-edge sensor bolometers coupled to orthogonal polarizations. Cold optics and an ambient temperature, rapidly-rotating half-wave plate made the ABS instrument unique. I will discuss the ABS instrument and its contributions to the field of CMB cosmology.
Host: Kam Arnold
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The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG)
Time: 3:00 pm - 3:30 pm
Place: 5280 Chamberlin Hall
Speaker: Brad Dober, University of Pennsylvania
Abstract: After decades of study, the physical processes regulating star formation remain poorly understood. In particular, the role played by magnetic fields in both the formation of molecular cloud structure and the regulation of core collapse is unclear. In many simulations, magnetic fields dramatically affect both the star formation efficiency and lifetime of molecular clouds. However, observationally the strength and morphology of magnetic fields in molecular clouds remain poorly constrained. Submillimeter polarimetry provides an important observational window on magnetic fields in star forming regions. By mapping polarized emission from dust grains aligned with respect to their local magnetic field, the field orientation (projected on the sky) can be traced. The Next-Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a 2.5 meter submillimeter polarimeter designed to map magnetic fields. BLAST-TNG utilizes three polarization-sensitive arrays of over 4000 microwave kinetic inductance detectors, centered at 250, 350, and 500 microns. BLAST-TNG will provide an unprecedented number of magnetic field vectors, and will enable a rigorous statistical analysis of the role that magnetic fields play in star formation. I will present the overall design and progress towards deployment of both the detector arrays and readout hardware in anticipation for a December 2016 BLAST-TNG Antarctic flight.
Host: Kam Arnold
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Friday, February 12th, 2016

High- and intermediate-velocity clouds as a tracer of cosmic rays in the Galactic halo
Time: 1:00 pm - 2:00 pm
Place: 4274 Chamberlin Hall
Speaker: Luigi Tibaldo, MPIK, Heidelberg
Abstract: I will present the first observational estimate of the large-scale distribution of cosmic-ray (CR) nuclei in the halo of the Milky Way, achieved through gamma-ray observations of high- and intermediate velocity clouds by the Fermi Large Area Telescope. CRs up to at least PeV energies are usually described in the framework of an elementary scenario that involves acceleration by supernova remnants or superbubbles in the Milky Way disk, and then diffusive propagation throughout the Galaxy and its halo. The details of the propagation process are so far mainly constrained indirectly by the composition of CRs in the solar system, and then extrapolated to the whole Galaxy. The densities of CR nuclei in remote locations, on the other hand, can be traced via the gamma rays they produce in inelastic collisions with clouds of interstellar gas. Recently, we performed a search for gamma-ray emission from several high- and intermediate-velocity clouds located in the halo of the Milky Way up to ~ 7 kpc from the disk. The gamma-ray emission rate per hydrogen atom was found to decrease with distance from the disk, which provides direct evidence that CRs at the relevant energies originate therein. Furthermore, I will discuss how the results call for a critical reexamination of propagation models against other direct and indirect observations of CRs.
Host: Justin Vandenbroucke
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