MARCH 3 - 7, 2008

MONDAY, MARCH 3

12 noon: Solar, Stellar, and Planetary Sciences Division Seminar. "Direct Imaging of Exoplanets: Prospects for Comparative Exoplanetology," Beth Biller, IfA, University of Hawaii. Phillips Auditorium (note change in location).

Abstract: Direct detection, and direct spectroscopy in particular, has the potential of ushering in the era of comparative exoplanetology -- where we will be able to 1) fully map out the architecture of typical planetary systems and 2) study the physical properties of exoplanets in depth. Direct detection is complementary to other methods of planet detection such as the radial velocity or transit techniques. In addition, by directly detecting photons from planets, we attain critical information (luminosity, colors) about planets. However, numerous technical issues limit direct detection today to the brightest, youngest, most massive planets. I discuss the current crop of methods and surveys for direct imaging of planets including the Gemini Deep Planet Survey, the Simultaneous Differential Imaging survey at the VLT and MMT, and the NICMOS planet survey with HST. While no planets were found in these surveys, they set important constraints on the distribution of outer extrasolar planets -- specifically, the fraction of stars with planets with semi-major axis from 20 to 100 AU, and mass > MJup is 20% or less. I will also discuss future prospects for direct detection, including the NICI science campaign at Gemini South, starting in fall 2007. Currently, direct detection is limited to the youngest, brightest objects -- I will discuss the technical advances necessary to directly image earthlike planets.

2:00 pm: Special Talk. "Mass, Kinematics, Metallicity, and Gas Flows in High Redshift Galaxies," Dr. Dawn Erb, CfA. Phillips Auditorium.

Abstract: A large fraction of the stellar mass in the universe today formed during the redshift interval 1.5z3, when the universe was only about 25% of its current age. However, the quantitative study of galaxies in this redshift range from large spectroscopic samples has only recently become feasible. Such spectra offer a unique opportunity to quantify the physical conditions in these distant galaxies. I will discuss the results of a large near-IR spectroscopic survey of H-alpha emission in star-forming galaxies at z~2, including kinematic properties inferred from line widths and spatially resolved emission, star formation rates, determinations of elemental abundances, and the comparison of stellar, dynamical and inferred gas masses. I will also highlight recent evidence for powerful galactic outflows and demonstrate the need for significant gas accretion in galaxies at high redshift, and discuss studies that will be possible with the next generation of instruments such as GMT and ALMA.

TUESDAY, MARCH 4

12:30 pm: Institute for Theory and Computation (ITC) Seminar. Speaker: Prof. Feng Yuan, Shanghai Observatory. Topic: To be announced. Pratt Conference Room.

WEDNESDAY, MARCH 5

4:00 pm: Initiative in Innovative Computing (IIC) Seminar. "From Clicks to Touches-Decipher the Myths and Misnomer of Multi-Touch," Dr. Chia Shen, Visiting Senior Scientist, Initiative in Innovative Computing at Harvard, and Senior Research Scientist, MERL Research Lab. 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 recent years, there has been much Human Computer Interaction (HCI) research as well as commercial hardware innovations on direct touch interactive tabletops. As a result, a new field called Tabletop Computing (Off the Desktop Computing) has emerged. In this talk, I will offer glimpses into some of the ongoing research and development endeavors around the world, including our own, that have begun to put these interactive tabletops into the realm of social and visual computing, as well as educational and pedagogical applications. I will touch upon the impact, the challenges and open research questions that have stemmed from these new efforts.

THURSDAY, MARCH 6

11:00 am: Institute for Theory and Computation (ITC) Colloquium. "Absorption in Pairs of QSOs: Absence of QSO Feedback and Winds from Galaxies," Prof. David Tytler, University of California, San Diego. Pratt Conference Room.

Abstract: The first large sample of absorption lines in the spectra of pairs of QSOs that are close in the sky contains some surprises. The absorbers in the paired QSOs have very similar redshifts, as if the absorption is from blue and not red galaxies. The absorption is not from winds flowing out of galaxies at high velocities, suggesting that the metals entered the intergalactic medium at earlier times. We see no change in the absorption from neutral hydrogen in the background QSO as a sight line passes by a foreground QSO. Either the foreground QSO UV is emitted into a narrow beam toward us, or QSOs emit for < 1 Myr at the luminosity we seen. We use large hydrodynamic numerical simulations to interpret these data, but we can not find a simulation that matches even the intergalactic hydrogen absorption in single QSOs. We may have a problem with the simulations (we need self-shielding and radiative transfer), with the astrophysics (we need a less energetic photoionizing spectrum) or with cosmology (we need a higher amplitude for the clustering of matter on small scales, sigma_8 > 0.9).

12:30 pm: Optical and Infrared Astronomy Division Lunch Talk. "My GMT: Observing the Origins of Stars, Planets, and Life with 2020 Vision," Dr. Michael Meyer, Steward Observatory. Pratt Conference Room.

Abstract: Is the initial mass function of stars and sub-stellar objects universal regardless of the initial conditions of star formation? How common are planetary systems like our own among the sun-like stars of the Milky Way? Does complex organic chemistry arise naturally on the surfaces of potentially habitable planets? Obtaining answers to these fundamental questions will require a range of observational capabilities. Fortunately in the year 2020, astronomers will enjoy access to a stunning array of facilities, including ALMA, JWST, and the Giant Magellan Telescope (GMT). We will describe the unique attributes of the GMT that make it especially well-suited to enable progress including its fine spatial resolution, great sensitivity, and large field of view. We will focus on the potential of the GMT to resolve young stellar populations in nearby galaxies as well as image terrestrial planets around the very (VERY) nearest stars. We will summarize the instrumentation necessary to make these feats possible.

4:00 pm: Colloquium. "What to Do with One Million Quasars," Dr. Gordon Richards, Drexel University. (Anyone wishing to meet with the speaker should contact the host, Dr. Martin Elvis, 5-7442.) Preceded by tea at 3:30 pm. Phillips Auditorium.

Abstract: I will discuss how, by simply making better use of existing information, it is possible to extract nearly one million quasars from extant multi-band data sets. Upcoming large-scale, synoptic surveys such as LSST will allow for more than an order of magnitude in further gains. Such large samples, pushing to faint limits over wide areas and with accurate photometric redshifts allow for powerful statistical analyses. For example, constraining 1) galaxy formation/evolution models by determining the luminosity dependence of quasar clustering, 2) merger models from the distribution of binary quasars, 3) cosmological parameters through cosmic magnification, and 4) dark energy through the Integrated Sachs-Wolfe Effect.

FRIDAY, MARCH 7

12:30 pm: Radio and Geoastronomy Division Lunch Talk. "Where Have All the Electrons Gone? Laboratory and Astronomical Detection of Molecular Anions," Dr. Sandra Bruenken, CfA. Room M-340, 160 Concord Avenue.

Abstract: The importance of negative ions (anions) in astronomy was demonstrated in 1939 by Rupert Wildt who showed that H is the major source of optical opacity in the solar atmosphere, and therefore the material which one mainly sees when looking at the sun and similar stars. It is remarkable that in the many years since, during which nearly 130 neutral molecules and 14 positive molecular ions have been found in a variety of astronomical sources, no molecular anion had been identified, owing in large part to the absence of laboratory rotational spectra. All that has now changed. Initiated by our recent laboratory identification of the large molecular anion C6H as the carrier of a series of unidentified rotational emission lines in the circumstellar shell of the late carbon star IRC+10216, and its detection in the cold molecular cloud TMC-1, high resolution spectroscopy of molecular anions and searches for them in astronomical sources is now advancing at an astonishing pace. Five additional, closely related carbon chain anions were in the last year detected in our laboratory, and three of them have in the meantime also been detected with surprisingly high abundances in space. In this talk I will briefly review the spectroscopic techniques that we use to obtain rotational spectra of (under normal conditions mostly unstable) molecules, and how this data can be used to identify these molecules in astronomical sources. I will then describe our recent results on molecular anions in detail and outline how these new findings might improve our knowledge about the interstellar and circumstellar medium.

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