APRIL 7 - 11, 2008

MONDAY, APRIL 7

1:30 pm: High Energy Astrophysics Division Lunch Talk. "Mapping Science," Dr. Martin Rosvall, University of Washington. Phillips Auditorium.

Abstract: To comprehend the multipartite organization of large-scale biological and social systems, we introduce an information theoretic approach that reveals community structure in weighted and directed networks. We use the probability flow of random walks on a network as a proxy for information flows in the real system and decompose the network into modules by compressing a description of the probability flow. The result is a map that both simplifies and highlights the regularities in the structure and their relationships. We illustrate the method by making a map of scientific communication as captured in the citation patterns of more than 6,000 journals.

3:00 pm: Joint CfA/MIT Supernova Remnants and Neutron Stars Seminar. "The Persistence of Memory and the End of Amnesia: What the X-ray Observations of Young Supernova Remnants Tell Us About Type Ia Supernovae," Carles Badenes, Princeton University. Phillips Auditorium.

Abstract: The excellent X-ray observations of young Type Ia supernova remnants (SNRs) obtained with Chandra, XMM-Newton and Suzaku reveal a wealth of information about the explosions that originated them and their mysterious progenitors. I will discuss several examples, focusing on the SNRs Tycho and 0509-67.5. This last object, located in the LMC, is specially interesting given the recent results on the spectroscopy of its light echo. For the first time, we have been able to compare the spectra of a SNR and its parent SN, and we find an excellent agreement - both suggest a highly energetic, bright, Ni-rich event similar to SN 1991T. Given the mounting evidence that dim and bright Type Ia SNe might come from different kinds of progenitors, these SNR studies open new possibilities to investigate the local environments where the progenitor populations arise.

WEDNESDAY, APRIL 9

12:30 pm: High Energy Astrophysics Division Lunch Talk. "INTEGRAL Monitoring of GRS 1915+105," Dr. Diana Hannikainen, Metsahovi Observatory, Finland. Phillips Auditorium.

Abstract: Since March 2003, we have been monitoring the black hole X-ray binary GRS 1915+105 with INTEGRAL. GRS 1915+105 has been "on" since its discovery in 1992 and apparent superluminal ejections have been observed on several occasions. This LMXRB hosts a 14-solar mass black hole and is notorious for exhibiting a plethora of variability patterns. The aim of our monitoring program is to catch GRS 1915+105 in as many different variability X-ray/gamma-ray states. I shall present some results from our monitoring, concentrating on those observations for which we had radio coverage.

4:00 pm: Initiative in Innovative Computing (IIC) Seminar. "Hunting for Needles in Massive Astronomical Data Streams," Ryan Scranton, Google Sky Team. Preceded by refreshments at 3:45 pm. Room 330, 60 Oxford Street, Cambridge. Event parking is available at the 52 Oxford Street Garage [map]. Please inform the parking attendant you are attending the IIC seminar. (The IIC seminar series schedule is updated often with additional information and seminars.)

Abstract: Over the last decade astronomy has become a progressively more data intensive science with large area surveys such as the Sloan Digital Sky Survey providing data sets in excess of 200 million sources and covering many thousands of square degrees. This data rate will continue to increase as we move into the next decade with surveys such as PanSTARRS and LSST mapping the sky every three nights. The many science opportunities these surveys enable, from characterizing the nature of dark energy to searching for potentially hazardous asteroids, come with an associated challenge. How do we find unusual sources within massive Terabyte data streams where small errors in the classification of sources can swamp any intrinsic signature. In this talk I will discuss a number of techniques for hunting for needles within the haystack of astronomical data. From searching for supernovae within spectral surveys to searching for moving sources to looking for the one in a million event I will describe how we can make these challenges computationally efficient, what remains to be done and how this is a very fertile area for the collaboration between computer science, statistics and astrophysics.

4:30 pm: Joint CfA/Harvard University Atomic Physics Colloquium. "Computing with Quantum Knots: Non-Abelian Anyons and Topological Quantum Computation," Prof. Sankar Das Sarma, University of Maryland. Preceded by tea at 4:00 pm. Room 356, Jefferson Laboratory, Harvard University.

THURSDAY, APRIL 10

4:00 pm: Colloquium. Clay Fellowship Lecture: "Galaxies in Nearby Clusters: Cored Giants, Nucleated Dwarfs and Everything in Between," Dr. Andres Jordan, CfA. (Anyone wishing to meet with the speaker should contact the host, Prof. Charles Alcock, ext. 5-7100). Preceded by tea at 3:30 pm. Phillips Auditorium.

Abstract: Nearly a century after the nature of galaxies as "island universes" was established, their formation and evolution remain important problems in modern astrophysics. Observations of elliptical galaxies in the Virgo and Fornax clusters show that on nuclear scales, galaxies exhibit a gradual progression from a light "deficit" (cores) to a light "excess" (stellar nuclei), while on larger scales the brightness profiles of galaxies are accurately described by Sersic models. The central regions of elliptical galaxies hold a constant fraction of their mass in a central massive object: a super-massive black hole, a nuclear star cluster, or a combination thereof. Elliptical galaxies, whether giants or dwarfs, are found to share a continuum of properties across the entire range of galaxy mass. Despite the tumultuous times galaxies experience as they form and evolve, their end products show clear trends that all galaxy formation and evolution models must be able to explain.

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