Weekly Calendar of Events

MAY 4 - MAY 8, 2015


Noon: Solar, Stellar, and Planetary Sciences Division Seminar. "Earning the A: The APF's First Year of Science," Jennifer Burt, University of California, Santa Cruz. Pratt Conference Room.

Abstract: The Automated Planet Finder (APF) is the newest telescope at the Mt. Hamilton station of UCO/Lick Observatory. The APF was custom built to detect extrasolar planets via high-resolution radial velocity observations and has demonstrated 1m/s precision on bright, quiet stars. To support long-running RV surveys, we have developed a dynamic scheduler capable of making real-time observing decisions and running the telescope without human interaction. The scheduler's target selection is driven by balancing scientific goals (what we want to observe based on scientific interest, required data quality, and desired cadences) and engineering constraints (what we can observe based on current atmospheric conditions and physical limitations of the telescope). I will discuss the telescope automation process and the first round of scientific results produced by the APF, highlighting three new planetary systems, and then outline our future observing strategy.


11:00 am: Optical and Infrared Astronomy Division Seminar. "How I Found My Place in the Universe (and helped everybody else find theirs)," Jessica Mink, CfA. Pratt Conference Room.

Abstract: Over the past 45 years, I've developed an interest in maps into a variety of software which implements a variety of mapping functions to translate between images, catalogs, and precise coordinates in space. After several less portable programs, I wrote WCSTools, a user-friendly suite of software to do all of those things, with a variety of other tools added to manipulate files. To cover the third dimension, I added the RVSAO package to IRAF to use various methods to compute radial velocities and redshifts from spectra of astronomical objects, be they asteroids, stars, or galaxies. I'll discuss the evolution of these tools and the astronomical data environment.

12:30 pm: High Energy Astrophysics Division Lunch Talk. 1) "Shaken and Stirred - but Mixed? Fluid Flow Experiments in Galaxy Clusters," Dr. Elke Roediger, CfA; 2) "Magnetic Reconnection in Relativistic Astrophysical Jets," Dr. Lorenzo Sironi; and 3) Arcus: Exploring the Formation and Evolution of Clusters, Galaxies, and Stars," Dr. Randall Smith, CfA. Phillips Auditorium.

Abstract: 1) Elliptical cluster galaxies are stripped of their gaseous atmospheres during their motion through the intra-cluster medium (ICM). Deep X-ray observations now reveal the detailed morphology and temperature structure of the galaxies' tails and wakes of stripped gas. In the fluid dynamics paradigm, the flow patterns in a galaxy's wake depend strongly on the fluid's transport coefficients, i.e, its thermal conductivity and viscosity. For an analogy, consider a high or low viscosity flow around a blunt body - both types of flow can be distinguished by a laminar or turbulent wake, respectively. With this analogy in mind, our team acquired deep Chandra observations of gas-stripped cluster ellipticals in Virgo and Fornax to use the observed flow patterns in their wakes as an empirical measurement of the effective ICM viscosity. To this end, we directly compare these observations with hydrodynamical simulations tailored specifically to these galaxies. I will show how the flow-around-a-blunt-body-analogy can be applied correctly to gas-stripped elliptical galaxies, and will discuss indications that argue against an isotropic ICM viscosity near the Spitzer value. 2) In magnetically-dominated jets of Gamma-Ray Bursts and Active Galactic Nuclei, magnetic reconnection is often invoked as a mechanism to transfer the jet magnetic energy to the emitting particles, thus powering the observed non-thermal emission. With 2D and 3D first-principles particle-in-cell simulations, we show that magnetic reconnection in relativistic astrophysical jets satisfies all the basic conditions for the emission: extended non-thermal particle distributions (with power-law slope between -4 and -1, depending on the flow magnetization), efficient dissipation and rough equipartition between particles and magnetic field in the emitting region. 3) Arcus is a proposed Small Explorer mission attached to the ISS that will enable high-resolution soft X-ray spectroscopy with unprecedented sensitivity. Arcus will measure the effects of structure formation imprinted upon the hot baryons that are predicted to lie in extended halos around galaxies, groups, and clusters. The spatial distribution and motion of this hot, volume-filling, metal-enriched gas will reveal how gravity and feedback combine to produce the present day gravitationally-bound structures in the Universe. Feedback arises from supermassive black hole and starburst driven winds, and Arcus will trace the propagation of outflowing mass, energy and momentum from the vicinity of the black hole out to large scales. Arcus' capabilities will also make broad contributions to the science of stellar accretion, stellar coronae, exoplanet transits, and galactic structure as well as a wide range of other important areas of astrophysics. Arcus utilizes well-developed technologies: grazing-incidence X-ray optics being produced for the ESA Athena mission, high-efficiency X-ray gratings used on sub-orbital rocket flights, and flight-proven CCD detectors and electronics. Operation on the ISS offers a suitable environment at enormous savings in cost and mass compared to a free-flying mission. The proposal also includes an option to allow for guest investigators to supplement the science team and for guest observations to maximize the science return of Arcus to the community.

1:00 pm: Institute for Theory and Computation (ITC) Seminar. "Time Delay Cosmology," Dr. Eric Linder, Lawrence Berkeley Laboratory. Pratt Conference Room.


11:00 am: Institute for Theory and Computation (ITC) Colloquium. "Unveiling the Dark Side of the Universe with Cluster Lensing," Prof. Priya Natarajan, Yale University. Pratt Conference Room.

4:00 pm: Colloquium. Speaker: Prof. Roberto Abraham, University of Toronto. Preceded by tea at 3:30 pm. Phillips Auditorium.


12:30 pm: Radio and Geoastronomy Division Lunch Talk. Thesis presentations by Southampton students. "Optimising Observing Strategy for Near-Earth Asteroid Characterisation," Tarik Zegmott (advisors: Jose Galache & Martin Elvis); "Improving Atmospheric Studies of Hot Jupiters from the Ground," Rob Wells (advisor: Mercedes Lopez-Morales); "Helium, Heating and Propagation Studies of Interplanetary Shocks in the Inner Heliosphere," Alex James (advisor: Kelly Korreck); "Extreme Star Formation in the Centre of Our Galaxy," Mark Graham (advisor: Cara Battersby); and "Simulating the Formation of Carbon-Rich Molecules on Graphitic Surfaces, David Marshall (advisor: Hossein Sadeghpour). Room M-340, 160 Concord Avenue.

The Calendar is prepared by the Web Services Group. Entries may be submitted via email to weekly_cal@cfa.


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