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Monday, October 22, 2007

12:00 PM: Solar, Stellar, and Planetary Sciences Division Seminar "CHON Ices and the Formation of Saturn ," Sally Robinson, UCO/Lick Observatory. Pratt Conference Room

Abstract: Previous core accretions simulations have found that the formation timescale of Saturn is far longer than a reasonable lifetime of the solar nebula. Saturn's formation is impaired by (1) the long orbital timescale (compared with Jupiter), leading to a slower planetesimal collision rate, and (2) the assumption that H2O is the only volatile that gets incorporated into planetesimals. We use a 1+1-d evolving solar nebula model and a 214-species chemical reaction network to calculate the solid surface density available to form Saturn. New core accretion simulations based on the results of our protostellar disk model show that Saturn can form in less than 4 Myr.

Tuesday, October 23, 2007

12:30 PM: Institute for Theory and Computation (ITC) Seminar "Millimeter and Radio Studies of Z~6 Quasars ," Dr. Ran Wang, National Radio Astronomy Observatory. Pratt Conference Room

Abstract: We present millimeter and radio studies of a sample of 33 quasars at z~6. These quasars were observed with the Max Plank Millimeter Array (MAMBO) at 250GHz, and the VLA at 1.4GHz. Ten of them were detected by MAMBO. The average FIR-to-radio SED of the whole sample is comparable to the templates of local optical quasars. However, some of the 250 GHz detections show strong FIR excesses in their spectral energy distributions. Further submillimeter observations of the two strongest 250 GHz sources suggest the FIR emission is from 50 - 60 K warm dust, with FIR luminosities >= 10^13 L_sun. Molecular CO was also detected in these sources. We investigate the luminosity correlations with this sample of z~6 quasars, and find that the derived FIR luminosities show a weak dependence on the B-band optical luminosities from the central AGN. The FIR to AGN bolometric emission ratios of most of the 250 GHz detections follow a relationship defined by a sample of local IR luminous quasars hosted in starburst ULIRGs. We discuss the FIR dust heating resources and star forming activities in the host galaxies of the z~6 quasars. We argue that in the strong MAMBO detections, the FIR dust heating is contributed significantly by massive star formation at a rate of >= 10^3 M_sun yr^-1. Thus they provide ideal candidates to study co-eval black hole and spheroidal galaxy formation in the early universe.

Wednesday, October 24, 2007

12:30 PM: High Energy Astrophysics Division Lunch Talk "Different Angles on AGN: Some Empirical Tests of the Unification Paradigm," Dr. Prajval Shastri, Indian Institute of Astrophysics, Bangalore. Pratt Conference Room

Abstract: Much of current AGN research is worked into the operating framework of the 'Unification Paradigm,' which is based on the notion that orientation plays a dominant role in the appearance of active galaxies. I will describe the results of a variety of empirical tests of unification, in both the radio-loud and radio-quiet regimes.

04:00 PM: Initiative in Innovative Computing (IIC) Seminar "Visualizing Ultra-Scale Data," Kwan-Liu Ma, Director, Institute for Ultrascale Visualization and Professor, Computer Science Department, University of California, Davis. Preceded by refreshments at 3:45 pm. Event parking is available at the 52 Oxford Street Garage [map]. Please inform the parking attendant. Room 330, 60 Oxford Street, Cambridge

Abstract: Advanced computing and imaging technologies enable scientists to study natural phenomena at unprecedented precision, resulting in an explosive growth of data. The size of the collected information about the Internet and mobile device users is expected to be even greater, a daunting challenge we must address in order to make sense and maximize utilization of all the available information. Visualization transforms large quantities of, possibly multiple-dimensional, data into graphical representations that exploit the high-bandwidth channel of the human visual system, leveraging the brain's remarkable ability to detect patterns and draw inferences. It has thus become an indispensable tool in many areas of study involving large data. I will introduce several effective solutions to the large data visualization problems found in a variety of areas from physical science, security, to software development.

Thursday, October 25, 2007

11:00 AM: Institute for Theory and Computation (ITC) Colloquium "Demographics of Big Black Holes," Prof. Doug Richstone, University of Michigan. Pratt Conference Room

12:30 PM: Optical and Infrared Astronomy Division Lunch Talk "Fundamental Properties of Cluster Galaxies and Their Redshift Evolution," Dr. Yen-Ting Lin , Princeton University. Pratt Conference Room

Abstract: Galaxy clusters represent an excellent laboratory for understanding various processes involving the galaxies, the dark matter potential, and the hot intracluster medium. Furthermore, in light of the on-going large scale cluster surveys (e.g. ACT, SPT), it is of critical importance that we understand the evolution of clusters towards z~1. I will present a detailed analysis of several fundamental properties (spatial distribution, luminosity function, mass-observable scaling relations) for various classes of cluster galaxies, including the blue and red galaxies, AGNs, and brightest cluster galaxies, based on large samples of clusters at z<0.2. In particular, the relevance of these observations to the halo occupation distribution formalism, the evolution of cluster galaxies, and the environmental dependence of the radio-loud AGN phenomenon, will be discussed. Finally, the redshift evolution of the cluster galaxy population out to z=0.9 is studied in terms of the luminous red galaxies, as well as the scaling relations.

04:00 PM: Colloquium "Hot On The Trail of Particle Dark Matter," Dr. Dan Hooper, FermiLab. (Anyone wishing to meet with the speaker should contact the host, Prof. Doug Finkbeiner, ext. 4-8393.) Preceded by tea at 3:30 pm. Phillips Auditorium

Abstract: For seventy years, evidence has steadily grown that much of the Universe's mass is non-luminous. Still today, however, we have not identified what makes up this mysteriously dark substance. Many experimental programs that hope to change this are underway, including deep underground detectors, gamma-ray telescopes, neutrino and anti-matter detectors, as well as particle colliders. Each of these efforts are searching for clues of dark matter's identity. With the new technologies needed to observe these particles rapidly developing, the hunt to discover dark matter's identity is well underway.

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