The influence of shocks on star formation in the OMC1 Ridge

Observations are presented of the OMC1 Ridge (a narrow band of molecular gas containing high-mass embedded sources), in the transitions CN N = 2 - 1, 13CO J = 2 - 1 and 13S J = 5 - 4. Variations in velocities and line widths indicate that three distinct regions are present in the area mapped, and that at least one of these is rotating. The resulting shocks when these fragments collided will have compressed the gas to a density nH2~107-8cm-3, sufficient to trigger collapse and to explain the presence of high-mass stars at the edges of the cloud fragments, rather than in their cores. These observational results support theoretical predictions of the importance of collisions in star formation

Another construction of edge-regular graphs with regular cliques

We exhibit a new construction of edge-regular graphs with regular cliques that are not strongly regular. The infinite family of graphs resulting from this construction includes an edge-regular graph with parameters $(24,8,2)$. We also show that edge-regular graphs with $1$-regular cliques that are not strongly regular must have at least $24$ vertices.Comment: 7 page

Detecting a rotation in the epsilon Eridani debris disc

The evidence for a rotation of the epsilon Eridani debris disc is examined. Data at 850 micron wavelength were previously obtained using the Submillimetre Common User Bolometer Array (SCUBA) over periods in 1997-1998 and 2000-2002. By chi-square fitting after shift and rotation operations, images from these two epochs were compared to recover proper motion and orbital motion of the disc. The same procedures were then performed on simulated images to estimate the accuracy of the results. Minima in the chi-square plots indicate a motion of the disc of approximately 0.6'' per year in the direction of the star's proper motion. This underestimates the true value of 1'' per year, implying that some of the structure in the disc region is not associated with epsilon Eridani, originating instead from background galaxies. From the chi-square fitting for orbital motion, a counterclockwise rotation rate of ~2.75 degrees per year is deduced. Comparisons with simulated data in which the disc is not rotating show that noise and background galaxies result in approximately Gaussian fluctuations with a standard deviation +/-1.5 degrees per year. Thus counterclockwise rotation of disc features is supported at approximately a 2-sigma level, after a 4-year time difference. This rate is faster than the Keplerian rate of 0.65 degrees per year for features at ~65 AU from the star, suggesting their motion is tracking a planet inside the dust ring. Future observations with SCUBA-2 can rule out no rotation of the epsilon Eridani dust clumps with ~4-sigma confidence. Assuming a rate of about 2.75 degrees per year, the rotation of the features after a 10-year period could be shown to be >1 degree per year at the 3-sigma level.Comment: 8 pages, 6 figure

Development of four-dimensional atmospheric models (worldwide)

Development of four dimensional atmospheric models from global data for predicting atmospheric attenuation encountered by earth resources observation sensor

The feasibility of sea surface temperature determination using satellite infrared data

Sea surface temperature determination feasibility using satellite infrared dat

Velocity map imaging of the dynamics of the CH3 + HCl -> CH4 + Cl reaction using a dual molecular beam method

International audienceThe reactions CH3 + HCl → CH4 + Cl(²P_3/2) and CD₃ + HCl → CD₃H + Cl(²P_3/2) have been studied by photo-initiation (by CH₃I or CD₃I photolysis at 266 nm) in a dual molecular beam apparatus. Product Cl(²P</sub>3/2</sub>) atoms were detected using resonance enhanced multi-photon ionisation and velocity map imaging, revealing product translational energy and angular scattering distributions in the centre-of-mass frame. Image analysis is complicated by the bimodal speed distribution of CH₃ (and CD₃) radicals formed in coincidence with I(²P_3/2) and I(²P_1/2) atoms from CH₃I (CD₃I) photodissociation, giving overlapping Newton diagrams with displaced centre of mass velocities. The relative reactivities to form Cl atoms are greater for the slower CH₃ speed group than the faster group by factors of ~1.5 for the reaction of CH₃ and ~2.5 for the reaction of CD₃, consistent with the greater propensity of the faster methyl radicals to undergo electronically adiabatic reactions to form Cl(²P_1/2). The average fraction of the available energy becoming product translational energy is = 0.48 ± 0.05 and 0.50 ± 0.03 for reaction of the faster and slower sets of CH₃ radicals, respectively. The Cl atoms are deduced to be preferentially forward scattered with respect to the HCl reagents, but the angular distributions from the dual beam imaging experiments require correction for under-detection of forward scattered Cl products

Marine resources and ocean surveys

Application of ERTS-1 remotely sensed multispectral imagery to marine resources and oceanic observations and surveys - Conferenc