Talks & Events
Special Seminars: 2008
The WiggleZ Dark Energy Survey
I will give a short mid-survey report on the WiggleZ survey running on the Anglo-Australian Telescope which aims to be the first spectroscopic survey to detect BAO at high-z. (0.5< z <1)
Low-luminosity starburst galaxies under a GRB afterglow spotlight at high redshift
The Transiting Exoplanet Survey Satellite (TESS)
The Transiting Exoplanet Survey Satellite (TESS) is a low cost, SMEX-class planet finder. In a two year all-sky survey, TESS will observe more than two million bright, nearby stars, searching for temporary drops in brightness that are caused by planetary eclipses. These eclipses (or "transits") occur when a planet's orbit carries it directly in front of its parent star. Such transits not only provide the means of identifying the planet, but also provide knowledge of the planet's diameter, mass density, surface gravity, temperature, and other key properties.
TESS is expected to catalog more than 1000 transiting exoplanet candidates--20 times as many as are presently known, including a sample of 'super Earths'. The TESS "wide-shallow" survey will be complementary to the "narrow-deep" ones of the Corot and Kepler missions: its sky coverage will exceed that of Corot by 1000 times, and that of Kepler by 400 times. Because the TESS all-sky survey will systematically examine every interesting bright star likely to harbor an exoplanet, the resulting TESS Transit Catalog will constitute a unique scientific legacy. High resolution, follow-up ground-based optical and space-based IR spectroscopy of exoplanets demands bright targets. Thus, TESS should identify those new exoplanets that are ideal for study with the world's largest ground-based telescopes, as well as with NASA's upcoming James Webb Space Telescope.
The TESS mission is a collaborative effort led by researchers at MIT, the Harvard-Smithsonian Center for Astrophysics, and the NASA Ames Research Center. Additional TESS partners include the NASA Goddard Space Flight Center, the Harvard Origins of Life Initiative, Lowell Observatory, Caltech's IPAC, the SETI Institute, Geneva Observatory in Switzerland, Tokyo Institute of Technology, SUPAERO in France, ATK Space, Espace Inc, and the privately-funded Las Cumbres Observatory Global Telescope Network. TESS has been accepted for a Phase A study by NASA, and is proposed for launch in early 2012.
The many types of outflows from AGNs: second installment
But, the origin of the absorption lines is still not understood: there are evidently many types of gas that give rise to the lines, but, in small samples of QSOs and absorbers, the origin is ambiguous. Large statistical samples have permitted the delineation of a definite outflow component of hot gas outflowing from the region very close to the AGN.
There are other indications of aggregate stellar winds from star formation that affect the gas a few kpc from the disk. And, evidence of an ionized component of halos of galaxies clustered with the QSO host (within 1 Mpc). These three are very hard to distinguish in single QSO spectra and lead to much ambiguity on the origin of the "associated QSO absorption lines". The better established Broad Absorption Lines (BALs), long thought to originate from winds close to the AGN show some signs of being related to the narrow line outflows. Very broad BALs may also finally be tied to the lower-outflow-velocity BAL features.
Statistical samples of "intervening" QSOALS (galaxies) are contaminated by these outflows, which reach 12,000 km/sec statistically and which have been claimed to be at higher velocities in special cases. The QSOALS are so numerous that a comparison of their statistics with predictions from simulations may offer the best test of models of galaxy formation.
The FEARLESS Project: Modeling Unresolved Turbulence in Cosmological Simulations
Simulations of structure formation that include the cooling, collapse,and feedback of gas have reached a level of sophistication where a more accurate treatment of numerically unresolved turbulence becomes relevant. Apart from its direct backreaction on the resolved velocity field, the kinetic energy of small-scale turbulence is an important parameter for subgrid models of unresolved non-equlibrium physics such as star formation and magnetic field amplification. The FEARLESS project (Fluid mEchanics with Adaptively Refined Large Eddy Simulations) is our attempt to combine adaptive mesh refinement (AMR), as implemented in the Enzo code, with subgrid-scale modeling of turbulence. The method and first results of a galaxy cluster simulation will be presented in the talk.
The Heart of The Red Rectangle
Collaborators: Uma. P. Vijh, Lewis M. Hobbs, Jason Aufdenberg, Julie A. Thorburn, and Donald G. York
The proto-planetary Red Rectangle nebula is powered by HD 44179, a spectroscopic binary (P = 318 d), in whicha luminous post-AGB star (T_eff ~ 8000 K) is the primary source of both luminosity (L ~ 6000 L_sun) and currentstellar mass loss. A massive, nearly edge-on circumbinary disk prevents direct observations of the central stars, but the detection of a small, compact H II region at the disk's center and the observation of exceptionally brightExtended Red Emission (ERE) in the bipolar outflow cones demand the presence of a powerful source offar-ultraviolet (FUV) radiation, which cannot be the primary star, at the center of this nebula.
The nature of this FUV source and the driving mechanism of the bipolar outflow in this nebula, often discussed as a prototype for a large class of bipolar proto-planetary and planetary nebulae, have been subject of much discussion in recent decades.I will present the results of a seven-year spectroscopic monitoring program conducted at APO, which reveal the vicinity of the secondary star as the source of bipolar jets as well as the source of the FUV radiation. A model in which an accretion disk around low-mass main-sequence secondary, fed by the post-AGB primary through Roche lobe overflow, produces both the bipolar jets and the FUV ionizing radiation appears to be consistent with all currently existing data.