2,602 research outputs found
Gains from the upgrade of the cold neutron triple-axis spectrometer FLEXX at the BER-II reactor
The upgrade of the cold neutron triple-axis spectrometer FLEXX is described.
We discuss the characterisation of the gains from the new primary spectrometer,
including a larger guide and double focussing monochromator, and present
measurements of the energy and momentum resolution and of the neutron flux of
the instrument. We found an order of magnitude gain in intensity (at the cost
of coarser momentum resolution), and that the incoherent elastic energy widths
are measurably narrower than before the upgrade. The much improved count rate
should allow the use of smaller single crystals samples and thus enable the
upgraded FLEXX spectrometer to continue making leading edge measurements.Comment: 8 pages, 7 figures, 5 table
Measuring Extinction Curves of Lensing Galaxies
We critique the method of constructing extinction curves of lensing galaxies
using multiply imaged QSOs. If one of the two QSO images is lightly reddened or
if the dust along both sightlines has the same properties then the method works
well and produces an extinction curve for the lensing galaxy. These cases are
likely rare and hard to confirm. However, if the dust along each sightline has
different properties then the resulting curve is no longer a measurement of
extinction. Instead, it is a measurement of the difference between two
extinction curves. This "lens difference curve'' does contain information about
the dust properties, but extracting a meaningful extinction curve is not
possible without additional, currently unknown information. As a quantitative
example, we show that the combination of two Cardelli, Clayton, & Mathis (CCM)
type extinction curves having different values of R(V) will produce a CCM
extinction curve with a value of R(V) which is dependent on the individual R(V)
values and the ratio of V band extinctions. The resulting lens difference curve
is not an average of the dust along the two sightlines. We find that lens
difference curves with any value of R(V), even negative values, can be produced
by a combination of two reddened sightlines with different CCM extinction
curves with R(V) values consistent with Milky Way dust (2.1 < R(V) < 5.6). This
may explain extreme values of R(V) inferred by this method in previous studies.
But lens difference curves with more normal values of R(V) are just as likely
to be composed of two dust extinction curves with R(V) values different than
that of the lens difference curve. While it is not possible to determine the
individual extinction curves making up a lens difference curve, there is
information about a galaxy's dust contained in the lens difference curves.Comment: 15 pages, 4 figues, ApJ in pres
The size-star formation relation of massive galaxies at 1.5<z<2.5
We study the relation between size and star formation activity in a complete
sample of 225 massive (M > 5 x 10^10 Msun) galaxies at 1.5<z<2.5, selected from
the FIREWORKS UV-IR catalog of the CDFS. Based on stellar population synthesis
model fits to the observed restframe UV-NIR SEDs, and independent MIPS 24
micron observations, 65% of galaxies are actively forming stars, while 35% are
quiescent. Using sizes derived from 2D surface brightness profile fits to high
resolution (FWHM_{PSF}~0.45 arcsec) groundbased ISAAC data, we confirm and
improve the significance of the relation between star formation activity and
compactness found in previous studies, using a large, complete mass-limited
sample. At z~2, massive quiescent galaxies are significantly smaller than
massive star forming galaxies, and a median factor of 0.34+/-0.02 smaller than
galaxies of similar mass in the local universe. 13% of the quiescent galaxies
are unresolved in the ISAAC data, corresponding to sizes <1 kpc, more than 5
times smaller than galaxies of similar mass locally. The quiescent galaxies
span a Kormendy relation which, compared to the relation for local early types,
is shifted to smaller sizes and brighter surface brightnesses and is
incompatible with passive evolution. The progenitors of the quiescent galaxies,
were likely dominated by highly concentrated, intense nuclear star bursts at
z~3-4, in contrast to star forming galaxies at z~2 which are extended and
dominated by distributed star formation.Comment: 6 pages, 4 figures, accepted for publication in Ap
On a special case of Hadwiger's conjecture
Hadwiger's Conjecture seems difficult to attack, even in the very special case of graphs G of independence number α (G) = 2. We present some results in this special case
Distant red galaxies in the Hubble Ultra Deep Field
We take advantage of the Hubble Ultra Deep Field (UDF) data to study the
restframe optical and ultra violet (UV) morphologies of the novel population of
Distant Red Galaxies (DRGs). Six galaxies with J-Ks > 2.3 are found to Ks=21.5,
five of which have photometric redshifts z_phot > 2, corresponding to a surface
density of 0.9/arcmin^2. The surface brightness distributions of the z_phot > 2
galaxies are better represented by exponential disks than R^{1/4}-laws. Two of
the z_phot > 2 galaxies are extended, while three have compact morphologies.
The restframe optical morphology of the z_phot > 2 galaxies is quite different
from the restframe UV morphology: all the galaxies have red central components
which dominate in the NICMOS H_{160}-band images, and distinct off-center blue
features which show up in (and often dominate) the ACS images. The mean
measured effective radius of the z_phot > 2 galaxies is =1.9+/-1.4 kpc,
similar (within the errors) to the mean size of LBGs at similar redshifts. All
the DRGs are resolved in the ACS images, while four are resolved in the NICMOS
images. Two of the z_phot > 2 galaxies are bright X-ray sources and hence host
AGN. The diverse restframe optical and UV morphological properties of DRGs
derived here suggest that they have complex stellar populations, consisting of
both evolved populations that dominate the mass and the restframe optical
light, and younger populations, which show up as patches of star formation in
the restframe UV light; in many ways resembling the properties of normal local
galaxies. This interpretation is supported by fits to the broadband SEDs, which
for all five z_phot > 2 are best represented by models with extended star
formation histories and substantial amounts of dust.Comment: Accepted for publication in APJ
Geodynamic implications for zonal and meridional isotopic patterns across the northern Lau and North Fiji Basins
We present new Sr-Nd-Pb-Hf-He isotopic data for sixty-five volcanic samples from the northern Lau and North Fiji Basin. This includes forty-seven lavas obtained from forty dredge sites spanning an east-west transect across the Lau and North Fiji basins, ten ocean island basalt (OIB)-type lavas collected from seven Fijian islands, and eight OIB lavas sampled on Rotuma. For the first time we are able to map clear north-south and east-west geochemical gradients in 87Sr/86Sr across the northern Lau and North Fiji Basins: lavas with the most geochemically enriched radiogenic isotopic signatures are located in the northeast Lau Basin, while signatures of geochemical enrichment are diminished to the south and west away from the Samoan hotspot. Based on these geochemical patterns and plate reconstructions of the region, these observations are best explained by the addition of Samoa, Rurutu, and Rarotonga hotspot material over the past 4 Ma. We suggest that underplated Samoan material has been advected into the Lau Basin over the past âŒ4 Ma. As the slab migrated west (and toward the Samoan plume) via rollback over time, younger and hotter (and therefore less viscous) underplated Samoan plume material was entrained. Thus, entrainment efficiency of underplated plume material was enhanced, and Samoan plume signatures in the Lau Basin became stronger as the trench approached the Samoan hotspot. The addition of subducted volcanoes to the Cook-Austral Volcanic Lineament material, first from the Rarotonga hotspot, then followed by the Rurutu hotspot, contributes to the extreme geochemical signatures observed in the northeast Lau Basin
The Establishment of the Maine State Ferry Service
https://digitalmaine.com/port_authority_docs/1000/thumbnail.jp
Multiplication and Composition in Weighted Modulation Spaces
We study the existence of the product of two weighted modulation spaces. For
this purpose we discuss two different strategies. The more simple one allows
transparent proofs in various situations. However, our second method allows a
closer look onto associated norm inequalities under restrictions in the Fourier
image. This will give us the opportunity to treat the boundedness of
composition operators.Comment: 49 page
Abstract composition laws and their modulation spaces
On classes of functions defined on R^2n we introduce abstract composition
laws modelled after the pseudodifferential product of symbols. We attach to
these composition laws modulation mappings and spaces with useful algebraic and
topological properties.Comment: 19 page
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