681 research outputs found
Early Season Soybean Insects: Past Problems and Future Risk
The spring of 1994 saw many early season insect problems on soybeans in Iowa and, indeed, across much of the Midwest. Although early season problems on soybeans are not uncommon, certainly the scale of problems we saw in 1994 was unusual. Undoubtedly, many of these problems followed from weather, in particular the heavy rains of 1993. In this paper, we will briefly review some of the reasons behind the events we saw in 1994 and focus on the potential for future problems and their management. In particular, with the possibility of many acres coming into production out of the Conservation Reserve Program (CRP), there is a potential for specific insect problems that should be recognized
Molecular gas in NUclei of GAlaxies (NUGA) XV. Molecular gas kinematics in the inner 3kpc of NGC6951
Within the NUclei of GAlaxies project we have obtained IRAM PdBI and 30m
12CO(1-0) and 12CO(2-1) observations of the spiral galaxy NGC 6951. Previous
work shows that there is indirect evidence of gas inflow from 3 kpc down to
small radii: a large-scale stellar bar, a prominent starburst ring (r~580 pc)
and a LINER/Seyfert 2 nucleus. In this paper we study the gas kinematics as
traced by the CO line emission in detail. We quantify the influence of the
large-scale stellar bar by constructing an analytical model of the evolution of
gas particles in a barred potential. From this model gravitational torques and
mass accumulation rates are computed. We compare our model-based gravitational
torque results with previous observationally-based ones. The model also shows
that the large-scale stellar bar is indeed the dominant force for driving the
gas inward, to the starburst ring. Inside the ring itself a nuclear stellar
oval might play an important role. Detailed analysis of the CO gas kinematics
there shows that emission arises from two co-spatial, but kinematically
distinct components at several locations. The main emission component can
always be related to the overall bar-driven gas kinematics. The second
component exhibits velocities that are larger than expected for gas on stable
orbits, has a molecular gas mass of 1.8x10^6Msun, is very likely connected to
the nuclear stellar oval, and is consistent with inflowing motion towards the
very center. This may form the last link in the chain of gas inflow towards the
active galactic nucleus in NGC 6951.Comment: 17 pages, accepted by A&A (17 feb 2011
Oil-Soluble Dyes for Marking European Corn Borer (Lepidoptera: Crambidae)
The European corn borer, Ostrinia nubilalis (Hubner), is a pest of corn throughout the Corn Belt. It also is the target pest of the first commercially available transgenic corn hybrids. These transformed hybrids contain a modified gene from the bacterium Bacillus thuringiensis Berliner that expresses an insecticidal protein (Koziel et al. 1993, Bio!T echnol. 11 : 194-200). The widespread use of these hybrids has fueled the development of resistance management models and protocols
Feeding AGN: new results from the NUGA survey
The NUGA project is a high-resolution (0.5''-1'') CO survey of low luminosity
AGN including the full sequence of activity types (Seyferts, LINERs and
transition objects). NUGA aims to systematically study the different mechanisms
for gas fueling of AGNs in the Local Universe. In this paper we discuss the
latest results of this recently completed survey, which now includes newly
acquired subarcsec resolution observations for all targets of the sample. The
large variety of circumnuclear disk morphologies found in NUGA galaxies (m=1,
m=2 and stochastic instabilities) is a challenging result that urges the
refinement of current dynamical models. In this paper we report on new results
obtained in 4 study cases for NUGA: NGC4826, NGC7217, NGC4579 and NGC6951Comment: 4 pages, 2 figures. Contributed talk to appear in "The Interplay
among Black Holes, Stars and ISM in Galactic Nuclei," Proc. IAU 222 (Gramado,
Brazil), eds. Th. Storchi Bergmann, L.C. Ho, H.R. Schmit
NUGA: the IRAM survey of AGN spiral hosts
The NUclei of GAlaxies (NUGA) project is a combined effort to carry out a
high-resolution (<1'') interferometer CO survey of a sample of 12 nearby AGN
spiral hosts, using the IRAM array. We map the distribution and dynamics of
molecular gas in the inner 1 kpc of the nuclei with resolutions of 10-50 pc,
and study the mechanisms for gas fueling of the different low-luminosity AGN.
First results show evidence for the occurrence of strong m=1 gas instabilities
in Seyferts. NUGA maps allow us to address the origin/nature of m=1 modes and
their link with m=2 modes and acoustic instabilities, present in other targets.Comment: 1 gzipped tar file containing 1 Latex file + 3 eps figures.
Proceedings of ''Active Galactic Nuclei: from Central Engine to Host
Galaxy'', meeting held in Meudon, France, July 23-27, 2002, Eds.: S. Collin,
F. Combes and I. Shlosman. To be published in ASP Conference Serie
Molecular Gas in NUclei of GAlaxies (NUGA). X. The Seyfert 2 galaxy NGC 3147
We present CO(1-0) and CO(2-1) observations of the SA(rs)bc Seyfert 2 galaxy
NGC 3147, obtained with the IRAM interferometer at 1\farcs9 1\farcs6
and 1\farcs6 1\farcs4 resolutions, respectively. A central peak seen
mainly in CO(2-1) and a ring-like structure at \arcsec 2 kpc
dominate the CO maps. In CO(1-0) an outer spiral at \arcsec
4 kpc is also detected, not visible in CO(2-1) emission because it falls
outside the field-of-view of the primary beam. The kinematics of the molecular
structures are quite regular, although there is evidence for local non-circular
or streaming motions. We show that the molecular gas distribution is similar
but not exactly identical to those of star formation tracers. Using a NIR image
obtained with adaptive optics at the CFHT Telescope, we identify a weak bar in
NGC 3147, which is classified as non-barred galaxy in the optical. We then
compute the gravity torques exerted by this stellar bar on the gas. We find
that the gas inside the inner CO ring is subject to a net negative torque and
loses angular momentum. This is expected for gas at the UHR, just inside the
corotation resonance of the stellar bar. In contrast, the gas outside
corotation, in the spiral arms comprising the outer spiral structure, suffers
positive torques and is driven outwards. We conclude that some molecular gas is
presently flowing into the central region, since we find negative torques down
to the resolution limit of our images.Comment: 17 pages, 23 figures, accepted for publication in A&
Testing models for molecular gas formation in galaxies: hydrostatic pressure or gas and dust shielding?
Stars in galaxies form in giant molecular clouds that coalesce when the
atomic hydrogen is converted into molecules. There are currently two dominant
models for what property of the galactic disk determines its molecular
fraction: either hydrostatic pressure driven by the gravity of gas and stars,
or a combination of gas column density and metallicity. To assess the validity
of these models, we compare theoretical predictions to the observed atomic gas
content of low-metallicity dwarf galaxies with high stellar densities. The
extreme conditions found in these systems are optimal to distinguish the two
models, otherwise degenerate in nearby spirals. Locally, on scales <100 pc, we
find that the state of the interstellar medium is mostly sensitive to the gas
column density and metallicity rather than hydrostatic pressure. On larger
scales where the average stellar density is considerably lower, both pressure
and shielding models reproduce the observations, even at low metallicity. We
conclude that models based on gas and dust shielding more closely describe the
process of molecular formation, especially at the high resolution that can be
achieved in modern galaxy simulations or with future radio/millimeter arrays.Comment: 20 pages, 12 figures. Accepted for publication in Ap
CASCO: Cosmological and AStrophysical parameters from Cosmological simulations and Observations -- I. Constraining physical processes in local star-forming galaxies
We compare the structural properties and dark matter content of star-forming
galaxies taken from the CAMELS cosmological simulations to the observed trends
derived from the SPARC sample in the stellar mass range , to provide constraints on the value of
cosmological and astrophysical (SN- and AGN-related) parameters. We consider
the size-, internal DM fraction-, internal DM mass- and total-stellar mass
relations for all the 1065 simulations from the IllustrisTNG, SIMBA and ASTRID
suites of CAMELS, and search for the parameters that minimize the
with respect to the observations. For the IllustrisTNG suite, we find the
following constraints for the cosmological parameters: , and , which are consistent within with the results
from the nine-year WMAP observations. SN feedback-related astrophysical
parameters, which describe the departure of outflow wind energy per unit star
formation rate and wind velocity from the reference IllustrisTNG simulations,
assume the following values: and
, respectively. Therefore, simulations
with a lower value of outflow wind energy per unit star formation rate with
respect to the reference illustrisTNG simulation better reproduce the
observations. Simulations based on SIMBA and ASTRID suites predict central dark
matter masses substantially larger than those observed in real galaxies, which
can be reconciled with observations only by requiring values of
inconsistent with cosmological constraints for SIMBA, or
simulations characterized by unrealistic galaxy mass distributions for ASTRID.Comment: 24 pages, 10 figures, 9 tables. Accepted by MNRAS for publication;
Added a reference to sec. 4.
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