MARCH 24 - 28, 2008
TUESDAY, MARCH 25
12:30 pm: Radio and Geoastronomy Division Lunch Talk. "Radio Polarization as a Tool for Exploring the Milky Way," Dr. Tom Landecker, DRAO. Room M-340, 160 Concord Avenue.
Abstract: Magnetic fields in the Galaxy are a significant reservoir of energy and they must play a central role in interstellar processes. Imaging of the polarized Galactic radio emission is an important tool in unraveling the structure and strength of the field. We have recently completed a survey of polarized emission at 1.4 GHz from the Galactic plane. Combination of data from the DRAO Synthesis Telescope, the Effelsberg 100-m Telescope and the DRAO 26-m Telescope gives full sampling of polarized emission from the largest structures down to the resolution limit, of the order of 1 arcminute. With 17 million independent data points, this is the largest survey ever made of extended polarized emission. I will describe the techniques developed for acquiring and processing this wide-field polarimetric survey and for combining single-antenna and aperture-synthesis datasets. I will discuss preliminary interpretations of many of the details seen in the images. The future of this subject lies in wideband polarimetry with many frequency channels. I will describe new data acquisition and processing techniques, and will outline plans for surveys of the whole sky, north and south, using large single-antenna radio telescopes.
1:00 pm: Visualizing Astronomy at the CfA. "Sky in Google Earth," Felice Frankel, Harvard University, IIC. The purpose of this lecture series is to engage the CfA community in how to best bring astronomical images, data, and concepts to the multitude of interested audiences, which ranges from the scientific community to the media and ultimately the general public. Phillips Auditorium.THURSDAY, MARCH 27
12:30 pm: Optical and Infrared Astronomy Division Lunch Talk. "Time Dilation in Type Ia Supernova Spectra at High Redshift," Dr. Stephane Blondin, CfA. Pratt Conference Room.
Abstract: We present multiepoch spectra of 13 high-redshift Type Ia supernovae (SNe Ia) drawn from the literature, the ESSENCE and SNLS projects, and our own separate dedicated program on the ESO Very Large Telescope. We use the Supernova Identification (SNID) code of Blondin & Tonry to determine the spectral ages in the supernova rest frame. Comparison with the observed elapsed time yields an apparent aging rate consistent with the 1/(1+z) factor (where z is the redshift) expected in a homogeneous, isotropic, expanding universe. These measurements thus confirm the expansion hypothesis, while unambiguously excluding models that predict no time dilation, such as Zwicky's "tired light" hypothesis. We also test for power-law dependencies of the aging rate on redshift. The best-fit exponent for these models is consistent with the expected 1/(1+z) factor.
4:00 pm: Colloquium. "(Some) Highlights from Spitzer Studies of Star Formation," Dr. Lori Allen, CfA. Preceded by tea at 3:30 pm. Phillips Auditorium.
Abstract: I will discuss recent results on Milky Way star forming regions, using data primarily from the Spitzer Space Telescope. These new, large samples from Spitzer Legacy, GO and GTO surveys provide constraints on theories of star formation in clusters and throughout molecular clouds, and allow us to derive global properties (like star formation rates and efficiencies) for nearby clouds and their dense cores. I will demonstrate how the Spitzer surveys help us to understand where stars form and what the timescales are for protostellar evolution, planet formation, and disk dissipation.
FRIDAY, MARCH 28
12:30 pm: Radio and Geoastronomy Division Lunch Talk. "Molecular Star-Formation Rate Indicators in Galaxies," Dr. Desika Narayanan, CfA. Room M-340, 160 Concord Avenue.
Abstract: We derive a physical model for the observed relations between star formation rate (SFR) and molecular line (CO and HCN) emission in galaxies, and show how these observed relations are reflective of the underlying star formation law. We do this by combining 3D non-LTE radiative transfer calculations with hydrodynamic simulations of isolated disk galaxies and galaxy mergers. We demonstrate that the observed SFR-molecular line relations are not necessarily representative of a more direct tracer of the SFR. Rather, they are driven by the relationship between molecular line emission and gas density, and anchored by the index of the underlying Schmidt law. Our model for SFR-molecular line relations quantitatively reproduces the slopes of the observed SFR-CO (J=1-0), CO (J=3-2) and HCN (J=1-0) relations when a Schmidt law with index of ~1.5 describes the SFR. We use these results to make imminently testable predictions for the SFR-molecular line relations of unobserved transitions.
UPCOMING ITAMP WORKSHOP
March 31 - April 2: Atomic and Molecular Physics of the Early Universe, Cambridge, Massachusetts. This workshop will bring together leading researchers in the astrophysics/cosmology and atomic/molecular physics communities for scientific interaction and exchange of ideas on the recent advances and challenges in theory, experiment and observation relating to the Early Universe. Organizers: Bernard Zygelman, (University of Nevada, Las Vegas), Phillip Stancil (University of Georgia), Alex Dalgarno Harvard University, ITAMP, Kate Kirby, ITAMP, Hossein Sadgepour, ITAMP. Additional information is available here.
SAO HUMAN RESOURCES NOTES
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.