September 6, 2013 | 12:00 PM | LASR Conference Room | Open Group seminar The large-scale structure of the Universe as seen by Planck Aurelien Benoit-Levy, University College London
One of main results of the 2013 data release of the Planck Collaboration is the first full-sky reconstruction of the lensing potential. The lensing potential is the projection on the sky of all the matter density fluctuations from today up to the last scattering surface and therefore constitutes the most complete information on the matter distribution at high redshift. In this talk, I will explain how the lensing potential, a quantity related to the large-scale structure of the Universe, can be reconstructed from observations of the anisotropies of temperature of the Cosmic Microwave Background (CMB) using the Planck data. I will then present in details the Planck lensing map and describe its use for cosmological studies, from improved constraints on cosmological parameters to joint analysis with current and future large-scale structure surveys.
September 13, 2013 | 12:00 PM | LASR Conference Room | Open Group seminar Testing dark energy as a function of scale Ignacy Sawicki, Institute for Theoretical Physics
The difference between various models of dark energy or modifications of gravity becomes apparent at the level of growth of large-scale structure in the universe. In addition to measuring the background expansion, we are now beginning to probe this aspect. I will discuss a model-ignorant approach to interpreting these observations and show the full set of late-universe observables that we might have in principle in the absence of a theory of dark energy. I will then show how we can construct null tests using these observables which constrain classes of dark-energy models and are uniquely capable of, for example, excluding the general scalar field as a mechanism for acceleration.
September 20, 2013 | 12:00 PM | LASR Conference Room | Open Group seminar Cosmology with the Secondary Anisotropies in the Cosmic Microwave Background Nicholas Battaglia, Carnegie Mellon University
Measurements of the primary anisotropies in the CMB have been the backbone of modern precision cosmology. Recently, high resolution CMB measurements from experiments, such as the Atacama Cosmology Telescope, the South Pole Telescope, and the Planck satellite are probing scales where the secondary anisotropies dominate over the primary. I will focus on the secondary anisotropies caused by the thermal and kinetic Sunyaev Zel'dovich effects. Our ability to obtain cosmological information from these secondaries is limited by our theoretical understanding of the baryons in the large-scale structure between us and the primary CMB. I will present numerical simulations that model these baryons and attempt to constrain various cosmological parameters. Additionally, I will discuss the wealth of astrophysical large-scale structure information (in particular galaxy cluster astrophysics) that is interconnected with these secondaries.
September 19, 2013 | 4:10 PM | LASR Conference Room | Special Seminar New Opportunities with the Gemini Observatory Markus Kissler-Patig, Gemini Observatory
Gemini Observatory's director Markus Kissler-Patig will present an update of the facility and introduce some new opportunities for astronomers at Gemini. Gemini operates twin 8-m telescopes, one in Hawaii and the other in Chile. The departure of the UK from Gemini's international partnership at the end of 2012 provided the chance to re-evaluate the services offered to Gemini users and opened new opportunities in two domains. First, Gemini will welcome discussions with groups wanting to bring their own instruments for campaigns. This visiting instrument program will complement the suite of workhorse instruments offered by the Observatory, and will allow scientific breakthroughs not possible with the regular suite of instruments. Second, the Gemini Observatory will be offering cross-partnership large or long programs. From 2014 on, Gemini will be dedicating 20% of Gemini time to high-impact large or long collaborative programs selected through a yearly call. Gemini is also looking at the possibility of offering some fraction of time in a fast turn-around mode, as well as "eavesdropping" for ueue observing. We remain very interested in having astronomers visit the telescopes. In addition to these two major initiatives, several new instruments have appeared in 2013: Flamingos-2 and the Gemini Multi-conjugate adaptive optics System (GeMS) are being offered for science, and the Gemini Planet Imager (GPI) has arrived on Cerro Pachon. We encourage all astronomers to attend this presentation to learn about these new opportunities, and to provide feedback how the Gemini Observatory can optimally support your research.