Physical properties of outflows: Comparing CO and H2O based parameters in Class 0 sources

Context. The observed physical properties of outflows from low-mass sources put constraints on possible ejection mechanisms. Historically, these quantities have been derived from CO using ground-based observations. It is thus important to investigate whether parameters such as momentum rate (thrust) and mechanical luminosity (power) are the same when different molecular tracers are used. Aims. We aim at determining the outflow momentum, dynamical time-scale, thrust, energy and power using CO and H2O as tracers of outflow activity. Methods. Within the framework of the WISH key program, three molecular outflows from Class 0 sources have been mapped using the HIFI instrument aboard Herschel. We use these observations together with previously published H2 data to infer the physical properties of the outflows. We compare the physical properties derived here with previous estimates based on CO observations. Results. Inspection of the spatial distribution of H2O and H2 confirms that these molecules are co-spatial. The most prominent emission peaks in H2 coincide with strong H2O emission peaks and the estimated widths of the flows when using the two tracers are comparable. Conclusions. For the momentum rate and the mechanical luminosity, inferred values are independent of which tracer that is used, i.e., the values agree to within a factor of 4 and 3 respectively.Comment: Accepted for publication in A&A, 5 pages, 2 figure

New Method to Calculate Electrical Forces Acting on a Sphere in an Electrorheological Fluid

We describe a method to calculate the electrical force acting on a sphere in a suspension of dielectric spheres in a host with a different dielectric constant, under the assumption that a spatially uniform electric field is applied. The method uses a spectral representation for the total electrostatic energy of the composite. The force is expressed as a certain gradient of this energy, which can be expressed in a closed analytic form rather than evaluated as a numerical derivative. The method is applicable even when both the spheres and the host have frequency-dependent dielectric functions and nonzero conductivities, provided the system is in the quasistatic regime. In principle, it includes all multipolar contributions to the force, and it can be used to calculate multi-body as well as pairwise forces. We also present several numerical examples, including host fluids with finite conductivities. The force between spheres approaches the dipole-dipole limit, as expected, at large separations, but departs drastically from that limit when the spheres are nearly in contact. The force may also change sign as a function of frequency when the host is a slightly conducting fluid.Comment: 29 pages, 8 figures, Accepted for Publication in Physical Review

Molecular Lines in Bok Globules and Around Herbig Ae/be Stars

This paper is intended as part of a more extensive molecular line survey in star forming regions along the evolutionary track of a collapsing cloud toward a young stellar object. We have studied a sample of seven small dark clouds (Bok globules) and eight Herbig Ae/Be stars in the J=1->0 transition of HCO$^{+}$, H$^{13}$CO$^{+}$, HCN and H$^{13}$CN. The choice of these molecules is determined by the simple chemistry and the predicted high abundance of the reactants leading to their formation. The isotopically substituted species (isotopomers), H$^{13}$CO$^{+}$ and H$^{13}$CN, were observed in order to determine, whenever possible, the optical thickness of the main species. The most abundant isotopomers were found in almost all the sources (detection rate 70-90\%). Those sources which exhibited the strongest signals were also searched for the $^{13}$C isotopomers. H$^{13}$CO$^{+}$ was found in one dark cloud and around three Herbig Ae/Be stars, while H$^{13}$CN around only one star. The column densities for each species and the physical conditions of the objects were derived whenever the observational data allowed it.Comment: 16 pages plus 6 figures available in hardcopy from [email protected] LaTEX ver. 2.09, BAP 11-1993-036-DD

A High Speed Network for Remote Observing from Caltech with the Keck Telescope

We are setting up a high speed (DS3) ATM network running from the dome of the 10-meter Keck Telescope on the summit of Mauna Kea in Hawaii to the Caltech campus in Pasadena, California. This network will be used to support remote observing, remote diagnostics of problems, remote software development, and other related tasks. We discuss the motivation for this effort, the network architecture, and the current status of this project

Remote observing with the Keck Telescope from California using NASA's ACTS satellite

As a technical demonstration project for the NASA Advanced Communications Technology Satellite (ACTS), we have implemented remote observing on the 10-meter Keck II telescope on Mauna Kea in Hawaii from the California Institute of Technology campus in Pasadena. The data connection consists of ATM networks in Hawaii and California, running at OC-1 speeds (51 Mbit/sec) through optical fiber, and high data rate (HDR) satellite antennae at JPL in Pasadena and at the Tripler Army Medical Center in Honolulu. The ACTS network provides sufficient bandwidth to enable true remote observing, with a software environment identical to that used for on-site observing. In this paper, we demonstrate that while the satellite link introduces a number of difficulties and decreases overall reliability of the system, remote observing is not only feasible, but provides several important advantages over standard observing paradigms. Benefits include involving more members of observing teams while decreasing expenses, enhancing real-time data analysis of observations by persons not subject to altitude-related conditions, and providing facilities, expertise, and personnel not normally available at the observing site. Although the current bandwidth of the public Internet is insufficient for true remote observing, we nevertheless anticipate a growing role for remote observing techniques, particularly as high-speed terrestrial networking paradigms, such as ATM, become more commonly available

Semi-classical twists for sl(3) and sl(4) boundary r-matrices of Cremmer-Gervais type

We obtain explicit formulas for the semi-classical twists deforming the coalgebraic structure of U(sl(3)) and U(sl(4)). In rank 2 and 3 the corresponding universal R-matrices quantize the boundary r-matrices of Cremmer-Gervais type defining Lie Frobenius structures on the maximal parabolic subalgebras in sl(n)

Engineering Electromagnetic Properties of Periodic Nanostructures Using Electrostatic Resonances

Electromagnetic properties of periodic two-dimensional sub-wavelength structures consisting of closely-packed inclusions of materials with negative dielectric permittivity $\epsilon$ in a dielectric host with positive $\epsilon_h$ can be engineered using the concept of multiple electrostatic resonances. Fully electromagnetic solutions of Maxwell's equations reveal multiple wave propagation bands, with the wavelengths much longer than the nanostructure period. It is shown that some of these bands are described using the quasi-static theory of the effective dielectric permittivity $\epsilon_{qs}$, and are independent of the nanostructure period. Those bands exhibit multiple cutoffs and resonances which are found to be related to each other through a duality condition. An additional propagation band characterized by a negative magnetic permeability develops when a magnetic moment is induced in a given nano-particle by its neighbors. Imaging with sub-wavelength resolution in that band is demonstrated

Statistical-mechanical theory of the overall magnetic properties of mesocrystals

The mesocrystal showing both electrorheological and magnetorheological effects is called electro-magnetorheological (EMR) solids. Prediction of the overall magnetic properties of the EMR solids is a challenging task due to the coexistence of the uniaxially anisotropic behavior and structural transition as well as long-range interaction between the suspended particles. To consider the uniaxial anisotropy effect, we present an anisotropic Kirkwood-Fr\"{o}hlich equation for calculating the effective permeabilities by adopting an explicit characteristic spheroid rather than a characteristic sphere used in the derivation of the usual Kirkwood-Fr\"{o}hlich equation. Further, by applying an Ewald-Kornfeld formulation we are able to investigate the effective permeability by including the structural transition and long-range interaction explicitly. Our theory can reduce to the usual Kirkwood-Fr\"{o}hlich equation and Onsager equation naturally. To this end, the numerical simulation shows the validity of monitoring the structure of EMR solids by detecting their effective permeabilities.Comment: 14 pages, 1 figur

First-Principles Approach to Electrorotation Assay

We have presented a theoretical study of electrorotation assay based on the spectral representation theory. We consider unshelled and shelled spheroidal particles as an extension to spherical ones. From the theoretical analysis, we find that the coating can change the characteristic frequency at which the maximum rotational angular velocity occurs. The shift in the characteristic frequency is attributed to a change in the dielectric properties of the bead-coating complex with respect to those of the uncoated particles. By adjusting the dielectric properties and the thickness of the coating, it is possible to obtain good agreement between our theoretical predictions and the assay data.Comment: 17 pages, 4 eps figures; minor revisions, accepted for publications by J. Phys.: Condens. Matte

Obscuration in the Host Galaxies of Soft X-ray Selected Seyferts

We define a new sample of 96 low-redshift (z<0.1), soft X-ray selected Seyferts from the catalog of the Einstein Slew Survey (Elvis etal. 1992, Plummer et al. 1994). We probe the geometry and column depth of obscuring material in the host-galaxy disks using galaxian axial ratios determined mainly from the Digitized Sky Survey. The distribution of host-galaxy axial ratios clearly shows a bias against edge-on spirals, confirming the existence of a geometrically thick layer of obscuring material in the host-galaxy planes. Soft X-ray selection recovers some of the edge-on objects missed in UV and visible surveys but still results in 30% incompleteness for Type 1's. We speculate that thick rings of obscuring material like the ones we infer for these Seyferts might be commonly present in early type spirals, sitting at the Inner Lindblad Resonances of the nonaxisymmetric potentials of the host galaxies.Comment: 14 pages including 2 tables and 3 eps figures, aas2pp4.sty, to appear in Ap