15,544 research outputs found
Highly extinguished emission line outflows in the young radio source PKS 1345+12
(Abridged) We present new, intermediate resolution spectra (~4A) of the
compact radio source PKS 1345+12. Our spectra clearly show extended line
emission (~20kpc) consistent with the asymmetric halo of diffuse emission
observed in optical and infra-red images. In the nucleus we observe complex
emission line profiles requiring 3 Gaussian components (narrow, intermediate
and broad). The broadest component (FWHM ~2000 km/s) is blue shifted by ~2000
km/s with respect to the galaxy halo and HI absorption. We interpret this as
material in outflow. We find evidence for high reddening and measure
E(B-V)>0.92 for the broadest component. From [S II]6716,6731 we estimate
electron densities of n_e5300 cm^{-3} and n_{e}>4200 cm^{-3}
for the regions emitting the narrow, intermediate and broad components
respectively. We calculate a total mass of line emitting gas of M_{gas}<10^6
solar masses. Not all emission line profiles can be reproduced by the same
model: [O I]6300,6363 and [S II] require separate, unique models. We argue that
PKS 1345+12 is a young radio source whose nuclear regions are enshrouded in a
dense cocoon of gas and dust. The radio jets are expanding, sweeping material
out of the nuclear regions. Emission originates from three kinematically
distinct regions though gradients (e.g. density, ionisation potential,
acceleration) must exist across the regions responsible for the emission of the
intermediate and broad components.Comment: Accepted for publication in MNRAS, 13 pages, 8 postscript figure
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Abundance and distribution of larval fishes and shrimps in the Laguna Madre, Texas : a hypersaline lagoon
To Texas Water Development BoardContract nos. IAC (88-89)1636 and (90-91)0751October 1990Tidal inlets connecting the Gulf of Mexico with estuarine waters are widely spaced and relatively narrow along the Texas coast. These inlets provide the sole route for ingress of larvae to the estuary for estuarine-dependent marine species and the egress of juveniles and sub-adults of these species back to the ocean. This study was an investigation of the abundance and distribution of ichthyoplankton of selected fishes and shrimps in an area where the opening and maintenance of a new tidal pass has been proposed in the Laguna Madre, a sub-tropical, hypersaline lagoon along the southern Texas coast. Surface and bottom ichthyoplankton samples were taken bimonthly in four zones in the Laguna Madre in areas which were directly influenced by tidal inlets from the Gulf of Mexico and areas isolated from such connections. Seasonal composition of the ichthyoplankton was similar to that reported from other Gulf of Mexico and southeastern United States estuaries with winter catches dominated by offshore spawners and summer catches dominated by inshore and estuarine spawners. The pelagic larvae of three species of estuarine spawners, bay anchovy (Anchoa mitchilli), spotted seatrout (Cynoscion nebulosus), and black drum (Pogonias cromis), were common throughout the Laguna Madre at salinities up to 50°/00. Pelagic larvae of offshore spawners were abundant only in the area near the tidal inlet and only a few individuals were found dispersed throughout the lagoon. The majority of these species are distributed throughout the Laguna Madre as juveniles but the dispersion or advection of these species to areas not closely associated with tidal inlets occurs at development stages older than the pelagic larval stage. These data suggest that opening and maintaining a tidal inlet in the upper Laguna Madre would increase the opportunity for recruitment of larvae of offshore spawners into an area currently unoccupied by these life-history stages.Marine Scienc
The impact of the warm outflow in the young (GPS) radio source & ULIRG PKS 1345+12 (4C 12.50)
(Abridged) We present new deep VLT/FORS optical spectra with intermediate
resolution and large wavelength coverage of the GPS radio source and ULIRG
PKS1345+12 (4C12.50; z=0.122), taken with the aim of investigating the impact
of the nuclear activity on the circumnuclear ISM. PKS1345+12 is a powerful
quasar and is also the best studied case of an emission line outflow in a
ULIRG. Using the density sensitive transauroral emission lines [S II]4068,4076
and [O II]7318,7319,7330,7331, we pilot a new technique to accurately model the
electron density for cases in which it is not possible to use the traditional
diagnostic [S II]6716/6731, namely sources with highly broadened complex
emission line profiles and/or high (Ne > 10^4 cm^-3) electron densities. We
measure electron densities of Ne=2.94x10^3 cm^-3, Ne=1.47x10^4 cm^-3 and
Ne=3.16x10^5 cm^-3 for the regions emitting the narrow, broad and very broad
components respectively. We calculate a total mass outflow rate of 8 M_sun
yr^-1. We estimate the total mass in the warm gas outflow is 8x10^5 M_sun. The
total kinetic power in the warm outflow is 3.4x10^42 erg s^-1. We find that
only a small fraction (0.13% of Lbol) of the available accretion power is
driving the warm outflow, significantly less than currently required by the
majority of quasar feedback models (~5-10\% of Lbol), but similar to recent
findings by Hopkins et al. (2010) for a two-stage feedback model. The models
also predict that AGN outflows will eventually remove the gas from the bulge of
the host galaxy. The visible warm outflow in PKS1345+12 is not currently
capable of doing so. However, it is entirely possible that much of the outflow
is either obscured by a dense and dusty natal cocoon and/or in cooler or hotter
phases of the ISM. This result is important not just for studies of young
(GPS/CSS) radio sources, but for AGN in general.Comment: Accepted for publication in MNRAS. 11 pages, 4 figure
Spaceborne memory organization, an associative data acquisition system, phase II Final report, Apr. - Dec. 1966
Spaceborne memory organization, associative data acquisition system design, and data compression technique
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Larval fish in the vicinity of aquaculture intakes
Texas Parks and Wildlife Department has recently proposed that all facilities pumping water from Texas estuaries be fitted with 0.5 mm screening to prevent larval fish mortality at these facilities. Data on larval fish distributions in Texas estuaries is quite limited (Holt et al. 1990). This report presents the results of a pilot study to examine the impact on larval fishes and shrimps of pumping water into mariculture facilities at three sites on the central and southern Texas Coast. The primary objective of this study was to determine the species composition, density and size structure of ichthyoplankton populations in the vicinity of the intake structures of the three mariculture facilities during their spring and fall pumping seasons. A secondary objective was to determine what organisms were actually being pumped through the system.Final report for contract IAC(90-91)111.5Prepared for Texas A&M Sea Grant, Texas General Land OfficeFebruary 1991Marine Scienc
Gas outflows in radio galaxies
We present a summary of our recent results on gas outflows in radio galaxies.
Fast outflows (up to 2000 km/s) have been detected both in ionized and neutral
gas. The latter is particularly surprising as it shows that, despite the
extremely energetic phenomena occurring near an AGN, some of the outflowing gas
remains, or becomes again, neutral. These results are giving new and important
insights on the physical conditions of the gaseous medium around an AGN.Comment: To appear in the proceedings of the IAU Symposium #217, Recycling
Intergalactic and Interstellar Matter, eds. P.-A. Duc, J. Braine, and E.
Brinks, 6 pages. The full paper with high resolution images can be downloaded
from http://www.astron.nl/~morganti/Papers/outflows.ps.g
Magnetic forming studies
Investigation of the tensile strength dependability on the characteristic time over which a pressure pulse is applied to a metal workpiece shows that the mechanical properties of these materials are functions of the rate at which the material is undergoing strain. These results and techniques are used in magnetomotive metal forming
Analysis of the project fire re-entry package flow field final technical report
Theoretical prediction of state of gas in flow field surrounding Apollo type vehicle in reentry at hypersonic speed
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