7,177 research outputs found
An uncatalogued optical HII region at the outskirts of the Galaxy
We present NOT optical observations of a clump (l = 127.9435 deg, b = +1.8298
deg), embedded in an extended, irregularly shaped, diffuse optical nebula. This
condensation shows an emission-line spectrum typical of classic HII regions.
Although its location on the sky coincides with a nearby extended photoionized
region recently identified by Cichowolski et al. (2003) in radio data from the
Canadian Galactic Plane Survey (CGPS), the systemic velocity of this ~ 1
arcmin-sized HII region, V_LSR = -7112 km/s, poses it far out in the
Galaxy, beyond the Perseus arm. The location of this region in the Galaxy is
supported by HI structures visible at comparable radial velocity on CGPS data.
We argue that this HII region might belong to an outer Galactic arm. The
emission line ratios of the surrounding extended nebula, whose radial velocity
is consistent with that of the small HII region, are typical of photoionized
gas in the low density limit. Smaller clumps of comparable surface brightness
are visible within the optical boundaries of the extended, faint nebula. After
comparison of the optical data with far infrared and radio observations, we
conclude that this nebula is an HII region, ~ 70 pc in size, probably
photoionized by an association of OB stars and surrounded by a ring of neutral
hydrogen.Comment: 8 pages, 9 figures (some of which degraded due to size constraints),
accepted on 2004/02/12 for publication in Astronomy and Astrophysic
Densification of powder metallurgy billets by a roll consolidation technique
Container design is used to convert partially densified powder metallurgy compacts into fully densified slabs in one processing step. Technique improves product yield, lowers costs and yields great flexibility in process scale-up. Technique is applicable to all types of fabricable metallic materials that are produced from powder metallurgy process
Particle dislodgement and entrainment by a low density airstream flowing over a surface
Dislodgement and entrainment of solid particles by low density airstream flowing over particulate surface, for aerodynamic surface erosion stud
Evaluation of the optical conductivity tensor in terms of contour integrations
For the case of finite life-time broadening the standard Kubo-formula for the
optical conductivity tensor is rederived in terms of Green's functions by using
contour integrations, whereby finite temperatures are accounted for by using
the Fermi-Dirac distribution function. For zero life-time broadening, the
present formalism is related to expressions well-known in the literature.
Numerical aspects of how to calculate the corresponding contour integrals are
also outlined.Comment: 8 pages, Latex + 2 figure (Encapsulated Postscript
Coseismic horizontal slip revealed by sheared clastic dikes in the Dead Sea Basin
Peer reviewedPostprin
Planetary environment simulation - Martian sand and dust storm simulation and evaluation, volume 2
Particle behavior in simulated Martian sand and dust stor
A pair of gigantic bipolar dust jets close to the solar system
We report the discovery of two adjacent jet candidates with a length of about
9 degrees each -- 10 times longer than the largest known jets -- detected by us
on 60 and 100 micron IRAS maps, but not observed at any other wavelength. They
are extremely collimated (length-to-width ratios 20--50), curved, knotty, and
end in prominent bubbles. Their dust temperatures are 25 K and 30 K,
respectively. Both harbour faint stars, one having a high proper motion (0.23
arcsec/yr) and being very red, suggesting a distance of about 60 pc. At this
distance, the total mass of both jet candidates is about about 1 solar mass. We
suspect that these gigantic (9 pc length respectively) jets are of fossil type
and have a common origin, due to the decay of a system of evolved stars. They
are the first examples of jets radiating in the far IR and might, because of
their closeness, be of interest for further studies of the acceleration and
collimation processes of astrophysical jets.Comment: 4 pages, 4 figures in reduced quality, accepted by Astronomy &
Astrophysics (Letter) february 10, 2004. See
http://astro.uibk.ac.at/dustjets/ for the full resolution and color version
of the image
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