MAY 5 - 9, 2008
TUESDAY, MAY 6
12:30 pm: Institute for Theory and Computation (ITC) Seminar. Speaker: Dr. Rennan Barkana, Tel Aviv University. Topic: to be announced. Pratt Conference Room.
WEDNESDAY, MAY 7
11:00 am: Optical and Infrared Astronomy Division Special Seminar. "Modelling Hierarchical Galaxy Formation with GalICS," Dr. Bruno Guiderdoni, Observatory of Lyon. Pratt Conference Room.
Abstract: In the current paradigm, galaxies form within Cold Dark Matter structures through dissipative collapse of the baryonic component in the potential wells of the dark matter halo hierarchy, and eventually merge to form bigger objects. I shall discuss an implementation of this scenario though the so-called "hybrid approach", in which dark matter collapse is described by a numerical simulation of a dark matter cosmological volume, and the baryonic processes involved in galaxy formation are modelled in a semi-analytic post-proccesing of the dark matter outputs. The GalICS model (for "Galaxies in Cosmological Simulations") result from a five-year effort that started at the Paris Institute of Astrophysics (Hatton et al. 2003, MNRAS 343, 75), and continued at the Observatory of Lyon. I shall describe the basic features of the model, and show how it reproduces quite nicely some of the basic statistical properties of galaxies in the local universe, as well as their evolution back in time (e.g., Lyman Break Galaxies). The model can be used to generate mock images and catalogues that are useful for preparing observations. As an example of the GalICS approach, I will use this model to show that some ingredients are missing if we are to explain the bimodal distribution of the colours of galaxies, as they appear in the SDSS data. I will explain how new physical ingredients added in the code (i.e., a re-examination of the cooling processes) produce results which are much more in agreement with the data (see e.g., Cattaneo et al. 2008, MNRAS, in press).
1:00 pm: Ph.D Colloquium. "Oscillations During Type I X-ray Bursts: Why We See Them, and Why We Don't," Randall Cooper. Phillips Auditorium.
Abstract: Type I X-ray bursts are thermonuclear explosions that occur on the surfaces of accreting neutron stars. Bursts often exhibit oscillations during the rising and/or decaying phase of their lightcurves. The discovery of these so-called burst oscillations is fairly recent and definitely exciting, for we can use observations of burst oscillations to probe the physics of neutron stars It is thought that a rotationally modulated non-axisymmetric hot spot generates oscillations during the burst rise, whereas surface modes are responsible for oscillations during the burst decay. So why do hot spots form and survive during the rise of some bursts but not of others What drives the surface modes during the burst tails And why do both of these mechanisms seem to function only at high accretion rates In this talk, I will review our current knowledge of burst oscillations and address these questions.
4:00 pm: Initiative in Innovative Computing (IIC) Seminar. "Towards the Design of Electronic Cognitive Prostheses," Ronald Baecker, Professor of Computer Science, Bell Chair in Human-Computer Interaction, University of Toronto. 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: The goal of our research is to envision, prototype, design, construct, and evaluate powerful and flexible electronic cognitive aids. We shall present six cognitive prosthesis research projects being done in collaboration with medical researchers and clinicians at Baycrest, Sunnybrook Health Sciences Center, and the Columbia University College of Physicians and Surgeons. Our goal is to support individuals and families who are struggling with amnesia, Mild Cognitive Impairment, and Alzheimer's disease, in tasks such as managing appointments, remembering names, and recalling and reminiscing about past and current experiences.
4:30 pm: Joint CfA/Harvard University Atomic Physics Colloquium. "Photon Localization and Dicke Superradiance: A Cross-Over to Small World Networks," Eric Akkerman, Technion. Preceded by tea at 4:00 pm: Room 356, Jefferson Laboratory, Harvard University.
THURSDAY, MAY 8
11:00 am: Institute for Theory and Computation (ITC) Colloquium. Speaker: Dr. Eric Agol, University of Washington. Topic: to be announced. Pratt Conference Room.
12:30 pm: Optical and Infrared Astronomy Division Lunch Talk. "Puzzles in Galaxy Scaling Relations," Dr. Stephane Courteau, Queen's University. Pratt Conference Room.
Abstract: Spiral galaxies exhibit global correlations between their total luminosity, maximum circular velocity, and disk scale length that pose a fundamental challenge to standard models of structure formation. On local scales, galaxy scaling relations that include velocity dispersion estimates (such as the M_BH-sigma and the Vcirc-sigma relations) are also challenging to both structure formation and galaxy dynamics models. I will discuss recent derivations of global and local galaxy scaling relations and our attempts to understand them. These scaling relations can also be interpreted in terms of the relative distribution of baryonic and dark matter in spiral galaxies as I address in this presentation.
4:00 pm: Colloquium. "Probing the Assembly of Massive Galaxies via Quasar Hosts at z=4," Dr. Kim McLeod, Wellesley College. (Anyone wishing to meet with the speaker should contact the host, Dr. Aneta Siemiginowska, ext. 5-7243.) Preceded by tea at 3:30 pm. Phillips Auditorium.
Abstract: One decade has now passed since near-IR imaging reoutfitted the "naked" quasars, and since HST gave us our first detailed look at low-redshift quasar host galaxies. At the same time, the discovery of the universal correlation between the masses of galaxies and their central black holes has ushered in a new generation of models of galaxy evolution. High-redshift quasars provide excellent leverage for tests of these models. As objects that already contain supermassive black holes at early times, they are destined to evolve into today's largest ellipticals. Yet surprisingly few host-galaxy redshift. In this talk, I will explain why as I present deep, near-IR images of 34 quasars at z=4 taken at the Magellan I and Gemini North telescopes. I will describe the search for their hosts and will use the results to constrain the evolution of the black hole/bulge relation. I will also describe how observations of their environments can reveal the pieces that will merge over cosmic time to become today's behemoths.
FRIDAY, MAY 9
12:30 pm: Radio and Geoastronomy Division Lunch Talk. "Red Absorption at Helium 10830 as a Probe of CTTS Accretion," Will Fischer, University of Massachusetts, Amherst. Room M-340, 160 Concord Avenue.
Abstract: High-resolution profiles of He I 10830 are yielding an improved understanding of the innermost 0.1 AU of T Tauri systems, where gas accretes from the disk to the star and spectacular outflows are launched. The helium profiles of 21/38 CTTS observed with NIRSPEC on Keck II feature redshifted absorption of the one-micron continuum, which can be used to probe the geometry of magnetospheric accretion. I model the red absorption via scattering of the stellar and accretion shock continua, finding that about half of the red absorptions and accompanying one-micron veilings are consistent with dipole flows of moderate width and accretion shock filling factors matching the size of the magnetospheric footpoints. The remaining half of the stars have broad, deep red absorption and low veiling, which require very wide flows with magnetic footpoints covering 10 to 20% of the stellar surface but accretion shock filling factors of only 1%. I model these profiles with large magnetospheres that are dilutely filled with accreting gas, leaving the disk over a range of radii in many narrow streamlets but filling only a small fraction of the entire infall region. In some cases, accreting streamlets need to extend from several stellar radii to at least the corotation radius, and in a few stars, the absorption is so deep at high velocities that non-dipolar flow geometries need to be considered.
2:00 pm: High Energy Astrophysics Division Talk. "Hot Halo Gas in Galaxy Merger Simulations," Dr. Manodeep Sinha, Pennsylvania State University. Tea Room (P-226).
Abstract: Galaxy merger simulations have explored the behaviour of gas within a galactic disk, yet the dynamics of hot gas within the galaxy halo has been neglected. We report on the initial results of high-resolution hydrodyanamic simulations of colliding galaxies with hot halo gas. We explore a range of mass ratios and orbital configurations to constrain the shocks and the dynamics of the gas within the progenitor halos. Preliminary results indicate that a strong shock with a temperature of about 3x10^6 K is produced in the halo of the galaxies before the first passage, increasing the temperature of the gas by almost an order of magnitude. About 12% of the initial gas mass is unbound from the galaxies and ends up at distances greater than 1 Mpc from the merger remnant. We discuss the implications of these results for galaxy evolution, and their role in the formation and enrichment of the Warm-Hot Intergalactic Medium.
SAO HUMAN RESOURCES NOTES
2008 Pre-Retirement Series for CSRS and FERS Employees
The Greater Boston Federal Executive Board has announced their 2008 Pre-Retirement Series. This year, for the first time, they will offer a 1-full day program for CSRS employees and 1-full day program for FERS employees, both featuring consultant Steve Marder and both will be held at the Volpe Center in Cambridge. The cost is $50 per person and registration is on a first come - first served basis.
The following links provide details and online registration.
Directions to the Volpe Center are available here.
Training Registration Instructions
Complete the newly simplified Request & Authorization for External Training/Tuition Reimbursement form, obtain the required department/division approvals and send the completed, signed form to the SAO Benefits Office in Human Resources, MS17. Approved participants will then be registered for this training by Procurement. Please note: if you register yourself for this training online, you will be required to provide payment via credit card and you may not receive reimbursement.
The new training form is a fillable Word document. If you should have any questions about completing this form or the enrollment process, please don't hesitate to contact Linda McDonald, ext. 6-7605 (e-mail: lmcdonald@cfa), or Anne LeBlanc, ext. 5-7371 (e-mail: aleblanc@cfa).
Job Vacancies
An online listing of all current SAO job openings is available. For more information, please call Human Resources, ext. 5-7371, or view your nearest bulletin board.