Day 557

Wednesday.

1311.7346
The origin of galactic cosmic rays
Blasi

Review.  New ways to investigate particle acceleration inside sources, ranging from radio, optical, to X-rays and gamma rays, to confront with data.  Focus on SN remnants as the most plausible sources of Galactic CRs, and review the main aspects of the modern theory of diffusive particle acceleration at SN remnant shocks, with special attention for the dynamical reaction of accelerated particles on the shock and the phenomenon of B-field amplification at the shock.  CR escape from the sources is discussed as a necessary step to determine the spectrum of CRs at the Earth.  Also discuss the phenomenon of CR acceleration at shocks propagating in partially ionized media and the implications of this phenomenon in terms of width of the Balmer line emission.

1311.7371
Starbugs: all-singing, all-dancing fibre positioning robots
GIlbert et al

Starbugs are miniature piezoelectric 'walking' robots with the ability to simultaneously position many optical fibers across a telescope's focal plane.  Their simple design incorporates two piezoceramic tubes to form a pair of concentric 'legs' capable of taking individual steps of a few microns, yet with the capacity to move a payload several millimeters per second.  The Australian Astronomical Observatory has developed this technology to enable fast and accurate field reconfigurations without the inherent limitations of more traditional positioning techniques, such as the 'pick and place' robotic arm.  Report on recent successes in demonstrating Starbug technology, driven principally by R&D efforts for the planned MANIFEST ("MANy INstrument FibrE SysTem) facility for the Gian Magellan Telescope.  Significant performance gains have resulted from improvements to the Starbug system, includling i) the use of a vacuum to attach Starbugs to the underside of a transparent field plate, ii) optimization of the control electronics, iii) a simplified mechanical design with high sensitivity piezo actuators, and iv) the construction of a dedicated laboratory 'test rig'.  A method of reliably rotating Starbugs in steps of several arc minutes has also been devised, which integrates with the preexisting x-y movement directions and offers greater flexibility while positioning.  Present measured performance data from a prototype system of 10 Starbugs under full (closed-loop control), at field plate angles of 0-90 degrees.

1311.7471
Kelvin-Helmholtz instabilities in multi-sized dust layers
Hasegawa, Tsuribe

* KH instability can occur when there is velocity shear in a single continuous fluid, or where there is a velocity difference across the interface between two fluids. 

Effect of the dust size distribution on KH instabilities in the protoplanetary disk with dust sedimentation.  Taking into account the dust size distribution, the growth rate of the KH instability is calculated using the linear stability analysis with the dust density distribution consistent with sedimentation.  Dust abundance required for gravitational instabilities before the KH instability is derived from the linear stability analysis, and it is found that the required dust abundance significantly coincides with that estimated from the Richardson number.  It is also found that when the dust size distribution is taken into account, the critical Richardson number for the onset of the KHI tends to increase with dust abundance.  This rest is different from that in the case without the dust size distribution.

1311.7670
Probing the z>6 universe with the first Hubble Frontier fields cluster Abell 2744
Atek, .. Kneib, … Egami, … Natarajan, et al

HFF program combines HST with cluster lensing to probe distant universe.  Present results for A2744.  Combine newly acquired NIR data with ancillary optical images to search for gravitationally lensed high-z (>6) galaxies.  Report the detection of 17 I814 dropout candidates and one Y105 dropout in a survey area of 1.43 arcmin^2 in the source plane.  The predictions of lens model allow identify five multiply-imaged systems lying at 6<z<8.  Thanks to constraints from the mass distribution in the cluster, able to estimate the effective survey volume corrected for completeness and magnification effects.  This was in turn used to estimate the rest-frame UV LF at z~6-8.  LF results are generally in agreement with the most recent blank field estimates, confirming the feasibility of surveys through lensing clusters.  Although based on a shallower observations than what will be achieved in the final dataset including the full ACS observations, the LF presented here extends down to 0.2 L* at z~7 thanks to the highly-magnified survey areas.  This early study forecasts the power of using massive galaxy clusters as cosmic telescopes and its complementary to blank fields.

1312.0003
Alcock-Paczynski cosmological test
Lopez-Corredoira

Evaluate AP test (evaluation of the ratio of observed angular size to radial/redshift size.  Depends only on the geometry of the Universe.  The z distortions produced by the peculiar velocities of the gravitational infall also have an influence, which should be separated from the cosmological effect.  Derive the anisotropic correlation function of sources in three surveys within SDSS: galaxies from SDSS-III/BOSS-DR10, and QSOs from SDSS-II and SDSS-III/BOSS-DR10.  From these, able to disentangle the dynamic and geometric distortions and thus deriving the ratio of observed angular size of radial/redshift size at different redshifts.  Also add some other values available in the literature.  Then use the data to evaluate which cosmological model fits them.  Used 6 different models: concordance LCDM, Einstein-de Sitter, open Friedman Cosmology without DE, flat Quasi-Steady State Cosmology, a Static Univers with a linear Hubble law, and a Static Uinverse with tired light redshift.  Only two of the six models fit the data: concordance LCDM and static universe with tired light redshift; whereas the rest of them are excluded within >95% CL.  If LCDM is the correct one, the best fit with a free Omega_m is produced for Omega_m=0.24pm0.1.