APRIL 21 - 25, 2008

TUESDAY, APRIL 22

12:30 pm: Institute for Theory and Computation (ITC) Seminar. "The Redshift Evolution of Galactic Structures (Bars, Bulges & Disks) at z < 1 from COSMOS: Quantifying the Assembly of the Hubble Sequence (2008, ApJ, 675, 1141)," Dr. Kartik Sheth, California Institute of Technology/Spitzer Science Center. Pratt Conference Room.

Abstract: We have analyzed the redshift-dependent fraction of galactic bars over 0.2 < z < 0.84 in 2,157 luminous face-on spiral galaxies from the COSMOS 2-square degree field. Our sample is an order of magnitude larger than that used in any previous investigation, and is based on substantially deeper imaging data than that available from earlier wide-area studies of high-redshift galaxy morphology. We find that the fraction of barred spirals declines rapidly with redshift. Whereas in the local Universe about 65% of luminous spiral galaxies contain bars (SB+SAB), at z~0.84 this fraction drops to about 20%. Over this redshift range the fraction of strong (SB) bars drops from about 30% to under 10%. It is clear that when the Universe was half its present age, the census of galaxies on the Hubble sequence was fundamentally different from that of the present day. A major clue to understanding this phenomenon has also emerged from our analysis, which shows that the bar fraction in spiral galaxies is a strong function of stellar mass, integrated color and bulge prominence. The bar fraction in very massive, luminous spirals is about constant out to z~0.84 whereas for the low mass, blue spirals it declines significantly with redshift beyond z=0.3. There is also a slight preference for bars in bulge dominated systems at high redshifts which may be an important clue towards the co-evolution of bars, bulges and black holes. Our results thus have important ramifications for the processes responsible for galactic downsizing, suggesting that massive galaxies matured early in a dynamical sense, and not just as a result of the regulation of their star formation rate.

WEDNESDAY, APRIL 23

12:30 pm: High Energy Astrophysics Division Lunch Talk. "Dying Radio Galaxies," Dr. Matteo Murgia, Observatory of Cagliari. Pratt Conference Room.

Abstract: I will present new radio and X-ray observations of a sample of fading radio galaxies recently discovered in the Westerbork Northern Sky Survey. These sources have been selected on the basis of their extremely steep broad-band radio spectra, which is a strong indication that these objects belong to the rare class of dying radio galaxies. Very Large Array and observations confirmed that in these sources the central engine has ceased to be active for a significant fraction of their lifetime although their extended lobes have not yet completely faded away. We found that many dying sources of our sample are located at the center of an X-ray emitting cluster of galaxies, suggesting that the pressure of a dense gaseous environment prevented a quick liquidation of the fossil radio lobes through adiabatic expansion. At last, I will show the results we obtained from a Chandra observation of one of these clusters.

4:00 pm: Initiative in Innovative Computing (IIC) Seminar. "eScience, Semantic Computing and the Cloud: Towards a Smart Cyberinfrastructure for eScience," Tony Hey, Corporate Vice President of External Research, Microsoft. 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: In the future, frontier research in many fields will increasingly require the collaboration of globally distributed groups of researchers needing access to distributed computing, data resources and support for remote access to expensive, multi-national specialized facilities such as telescopes and accelerators or specialist data archives. There is also a general belief that an important road to innovation will be provided by multi-disciplinary and collaborative research - from bio-informatics and earth systems science to social science and archaeology. There will also be an explosion in the amount of research data collected in the next decade - 100's of Terabytes will be common in many fields. These future research requirements constitute the 'eScience' agenda. Powerful software services will be widely deployed on top of the academic research networks to form the necessary 'Cyberinfrastructure' to provide a collaborative research environment for the global academic community. The difficulties in combining data and information from distributed sources, the multi-disciplinary nature of research and collaboration, and the need to move to present researchers with tooling that enable them to express what they want to do rather than how to do it highlight the need for an ecosystem of Semantic Computing technologies. Such technologies will further facilitate information sharing and discovery, will enable reasoning over information, and will allow us to start thinking about knowledge and how it can be handled by computers. This talk will review the elements of this vision and explain the need for semantic-oriented computing by exploring eScience projects that have successfully applied relevant technologies. It will also suggest that a software + service model with scientific services delivered from the Cloud will become an increasingly accepted model for research.

4:30 pm: Joint CfA/Harvard University Atomic Physics Colloquium. "Rydberg Matter - Many-Body Phenomena in an Ultracold Gas of Rydberg Atoms," Prof. Matthias Weidemuller, Physics Institute, Albert-Ludwig University Freiburg, Germany. Preceded by tea at 4:00 pm. Room 356, Jefferson Laboratory, Harvard University.

THURSDAY, APRIL 24

12:30 pm: Optical and Infrared Astronomy Division Lunch Talk. "Chasing Shadows: Occultation Surveys of the Outer Solar System," Ms. Federica Bianco, CfA. Pratt Conference Room.

Abstract: The outer solar system is still largely unprobed and unknown. I will describe the occultation technique -- the only known method to explore the small and the very distant objects that populate the outer solar system. I will talk about the difficulties encountered and the achievements of this peculiar observational method, with particular attention to the TAOS and the MMT/Megacam surveys.

4:00 pm: Colloquium. "The Science of the PAMELA Space Mission," Prof. Piergiorgio Picozza, INFN and University of Rome Tor Vergata. (Anyone wishing to meet with the speaker should contact the host, Prof. Douglas Finkbeiner, ext. 4-8393.) Preceded by tea at 3:30 pm. Phillips Auditorium.

Abstract: On the 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it is collecting data since July 2006. The core of the apparatus is a magnetic spectrometer with additional specialized detectors. The instrument allows for precision studies of charged cosmic radiation to be conducted over a wide energy range (100 MeV - 100's GeV) with high statistics. The primary scientific goal is the search for dark matter annihilation signals, through measurements of antiproton and positron energy spectra, and primordial antinuclei (anti-helium). PAMELA is also testing cosmic-ray propagation models by precise measurements of light nuclei and their isotopes energy spectra. Continuous monitoring of solar modulation, detecting solar flares and studying trapped particles in radiation belts complete the extent of PAMELA. The status of the mission and preliminary results in the different fields explored by PAMELA will be presented together a review of the experimental dark matter indirect searches.

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