OCTOBER 15 - 19, 2007

TUESDAY, OCTOBER 16

2:30 pm: Joint Tufts/CfA/MIT Cosmology Seminar Series. "New Cosmological Constraints from X-ray Studies of Galaxy Clusters," Dr. Steve Allen, Stanford University/KIPAC. Phillips Auditorium.

WEDNESDAY, OCTOBER 17

11:00 am: Ph.D. Colloquium. "Active Galactic Nuclei and the Unresolved Cosmic X-ray Background," Ryan Hickox. Phillips Auditorium.

Abstract: The cosmic X-ray background (CXB) is known to be primarily the integrated emission from active galactic nuclei (AGN), many of which are obscured by gas and dust. It is also increasingly clear that AGN play a key role in the evolution of their host galaxies. In this talk, I will discuss several observational studies of the AGN and the CXB that address these topics. The first part consists of the absolute measurement of the unresolved CXB in the Chandra Deep Fields, and a detailed study of the extremely faint X-ray emitting star-forming galaxies which produce most of this unresolved flux. The second part presents studies of AGNs in the 9 square degree multiwavelength survey in Bootes. Using mid-infrared selection, we identify the largest sample to date of luminous, obscured AGN ("Type 2 quasars") at 0.7 < z < 3, and confirm the selection based on X-ray properties from the Chandra XBootes survey. In addition, we measure the clustering of AGN and normal galaxies at 0.25 < z < 0.8. Separating X-ray AGNs into those with red and blue host galaxies, we find significant differences in clustering, X-ray spectra, and Eddington ratios, which suggest that these two populations may represent different modes of AGN accretion. We speculate that the X-ray AGNs in red galaxies represent a radiatively inefficient transition phase between the quasar and radio-loud phases.

12:30 pm: High Energy Astrophysics Division Lunch Talk. "Clusters of Galaxies in the First Half of the Universe from the Spitzer/IRAC Shallow Survey," Dr. Peter Eisenhardt, Jet Propulsion Laboratory. Pratt Conference Room.

4:00 pm: Symposium on Innovative Computing for the Humanities. Sponsored by the Humanities Center and Initiative in Innovative Computing. Thompson Room, Barker Center, Harvard University Campus (The IIC seminar series schedule is updated often with additional information and seminars.)

Abstract: The symposium will briefly introduce a series of innovative computing applications for the humanities, including: Imaging and Scanning, from 2D to 3D; Texts: Encoding, Mining, Analyzing; Multiverses and Virtual Worlds; Google, Libraries, and Research Information in the Humanities; Geospatial Visualization; and Digital Audio. Join us for an introduction to the Digital Humanities--the first in a series of talks and workshops addressing new opportunities for research computing in the arts, humanities, and nonquantitative social sciences. Cosponsored by the Humanities Center and the Institute for Innovative Computing. During the Fall and Spring there will be a series of presentations by scholars who have employed particular technologies in their research and workshops on how to apply them.

4:30 pm: Joint CfA/Harvard University Atomic Physics Colloquium. "Polarizabilities, Atomic Clocks, and Magic Wavelengths," Prof. Marianna Safronova, University of Delware. Preceded by tea at 4:00 pm. Room 356, Jefferson Laboratory, Harvard University.

THURSDAY, OCTOBER 18

11:00 am: Science Education Seminar and Open Discussion. Weekly sessions focus on current department programs, literature reviews, and recent trends in science education and assessment. Some sessions feature outside speakers or guests. All members of the CfA community are welcome. Please contact Bruce Ward at bward@cfa, if you wish to attend any session. Phillips Auditorium.

11:00 am: Institute for Theory and Computation (ITC) Colloquium. "The Ultrastrong Fields of Anomalous X-ray Pulsars," Dr. Feryal Ozel, University of Arizona. Pratt Conference Room.

Abstract: Anomalous X-ray Pulsars (AXPs) are a class of neutron stars that are believed to harbor the strongest magnetic fields in the universe. Even though indirect evidence of their strong fields, such as their energetic bursts and their rapid spindowns, has been accumulating for almost a decade, a direct measurement of their surface field strengths has not been made to date. I will present a coherent physical model of their surfaces and magnetospheres which explains very well their spectral characteristics. I will report the first spectroscopic measurement of the surface magnetic field strengths of several AXPs, which are remarkably close to the values inferred from their spindown rates. Finally, I will discuss the prospects of detecting directly the proton cyclotron features in their X-ray spectra with current and future X-ray missions.

12:30 pm: Optical and Infrared Astronomy Division Lunch Talk. "Precision Astrometry with Adaptive Optics and the Proper Motions of Galactic Compact Objects," Mr. Brian Cameron, California Institute of Technology. Pratt Conference Room.

Abstract: It is now generally appreciated that the space velocities of compact objects (pulsars, magnetars, LMXBs and HMXBs) directly inform us as to their origins and constrain their lifetimes. Here, we report on a program to measure the proper motions of magnetars using the laser guide star adaptive optics system on the Keck II telescope. We will discuss new potential near-infrared counterparts to magnetars and the implications of the proper motion results for magnetar formation and evolution. In addition, we will explain the limits of ground-based astrometry with adaptive optics and the prospects for carrying out astrometric programs on current and future ground-based telescopes.

4:00 pm: Colloquium. "Dark Nebular Cores and the Origin of Stellar Masses," Dr. Charles Lada, CfA. Preceded by tea at 3:30 pm. Phillips Auditorium.

Abstract: Detailed knowledge of the initial distribution of stellar masses at birth (the IMF) and how this quantity varies through space and time is necessary to predict the evolution of all stellar systems from star clusters to galaxies. Yet the origin of stellar masses remains one of the most fundamental unsolved problems of astrophysics. Stars form in the dense cores of dark nebulae, but little is understood about the detailed physical properties of these cores prior to star formation and even less is understood about their origin. Yet both these issues are critically linked to understanding the origin of stellar masses and the IMF. In this colloquium I will first review the current knowledge concerning functional form and universality of the IMF as derived from observations of field stars and extremely young clusters. I will then relate this knowledge to exciting new results concerning the physical nature of dense cores on the verge of star formation. I will argue that these results suggest that the distribution of initial stellar masses derives directly from the distribution of dense core masses which itself may have its origins in a process of simple thermal fragmentation in a pressurized medium. The initial distribution of stellar birth masses produced by star formation may therefore be the result of the interplay only a few very basic and measurable physical processes.

7:30 pm: Monthly Observatory Night for the Public. "50 Years of the Space Age," Jonathan McDowell, CfA. The lecture will be followed by telescopic observing, weather permitting. No tickets or reservations are necessary; however, seating is to the capacity of the hall. Doors open at 7:00 pm. Phillips Auditorium.

Abstract: On October 4, 1957, a stunned world learned that the Soviet Union had successfully launched the world's first artificial satellite, Sputnik 1. In the decades that followed, men landed on the moon and constructed space stations in low-Earth orbit, while unmanned probes scattered to every planet in the solar system. Where have we been, and more importantly, where are we going next? Does humankind have a future in space, and what might that fut ure look like? Space expert Jonathan McDowell will answer these questions and more.

FRIDAY, OCTOBER 19

12:30 pm: Radio and Geoastronomy Division Lunch Talk. "Discovery of Molecular Loops in the Galactic Center," Prof. Yaso Fukui, Nagoya University. Room M-340, 160 Concord Avenue.

Abstract: It has been a long standing puzzle that the gas in the galactic cneter shows very violent motion and warm temperature inspite of the apparent lack of energy sources. I present in the talk that there are two outstanding molecular loops of a few 100 pc height from the nuclear disk. I shall interprete that these loops are created by the magnetic floatation due to the Parker instability, similar to the solar prominence, althgouh the size scale is 12 orders of magnitude greater in the galactic center loops. The magnetci field strength is estimated to be 150 micro gauss from the Alfven speed. These magnetic loops have profound implications in star formation of this region since the molecular gas is controlled by the flotation. The floated gas falls down to the disk at a high velcoity of 30 km/s or more, creating strong shocks and massive molecular clumps, candidates for massive cluster formation. I will present fruther discussion on the possible loop candidates in the other galaxies.

SAO HUMAN RESOURCES NOTES

Leave Donations Requested

Due to a medical emergency, Donna Coletti of the Library has been approved as a leave donor recipient in the Leave Transfer Program. Any SAO Trust Fund employee who wishes to donate annual leave to Donna should complete a Leave Donor Form and send it to MS17.

Under the Leave Transfer Program, Trust Fund employees may only donate annual leave to other Trust Fund employees and Federal employees may donate annual leave only to other Federal employees. If you should have any questions or are not able to access the form, please contact Anne LeBlanc, ext. 5-7371.

Job Vacancies

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