1,202 research outputs found
Preparing Scientists, Policy-Makers, and Managers for a Fast-Forward Future
Ecosystems in the SacramentoâSan Joaquin Delta are changing rapidly, as are ecosystems around the world. Extreme events are becoming more frequent and thresholds are likely to be crossed more often, creating greater uncertainty about future conditions. The accelerating speed of change means that ecological systems may not remain stable long enough for scientists to understand them, much less use their research findings to inform policy and management. Faced with these challenges, those involved in science, policy, and management must adapt and change and anticipate what the ecosystems may be like in the future. We highlight several ways of looking aheadâscenario analyses, horizon scanning, expert elicitation, and dynamic planningâand suggest that recent advances in distributional ecology, disturbance ecology, resilience thinking, and our increased understanding of coupled humanânatural systems may provide fresh ways of thinking about more rapid change in the future. To accelerate forward-looking science, policy, and management in the Delta, we propose that the State of California create a Delta Science Visioning Process to fully and openly assess the challenges of more rapid change to science, policy, and management and propose appropriate solutions, through legislation, if needed
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Recent results and perspectives on cosmic backgrounds from radio to far-infrared
© 2019 World Scientific Publishing Company. Cosmological and astrophysical surveys from radio to far-infrared, in both temperature and polarization, offer a unique view of the universe properties and of the formation and evolution of its structures. The last release, close to be finalized, of the Planck mission results sets the scene for cosmological models and parameters, while the comparison with other types of data sets raises the issue of possible tensions about some parameters, first of all the Hubble constant. At the same time, on the extragalactic side, Planck carried out the deepest systematic all-sky survey of SZ galaxy clusters and detected thousands of dusty galaxies and many hundreds of extragalactic radio sources, also allowing us to investigate many specific topics, including molecular hydrogen clouds in galactic halos. The exploitation of future generation of CMB missions and the next radio facilities will allow us to deeply investigate several topics in cosmology and astrophysics, from the existence of primordial gravitational waves to the energy releases in the primeval plasma, from the dawn ages and the epoch of reionization to the formation and evolution of early galaxies and clusters, while a wide set of open astrophysical problems can be studied with future IR missions
OVI Observations of Galaxy Clusters: Evidence for Modest Cooling Flows
A prediction of the galaxy cluster cooling flow model is that as gas cools
from the ambient cluster temperature, emission lines are produced in gas at
subsequently decreasing temperatures. Gas passing through 10^5.5 K emits in the
lines of OVI 1032,1035, and here we report a FUSE study of these lines in three
cooling flow clusters, Abell 426, Abell 1795, and AWM 7. No emission was
detected from AWM 7, but OVI is detected from the centers of Abell 426 and
Abell 1795, and possibly to the south of the center in Abell 1795, where X-ray
and optical emission line filaments lie. In Abell 426, these line luminosities
imply a cooling rate of 32+/-6 Msolar/yr within the central r = 6.2 kpc region,
while for Abell 1795, the central cooling rate is 26+/-7 Msolar/yr (within r =
22 kpc), and about 42+/-9 Msolar/yr including the southern pointing. Including
other studies, three of six clusters have OVI emission, and they also have star
formation as well as emission lines from 1E4 K gas. These observations are
generally consistent with the cooling flow model but at a rate closer to 30
Msolar/yr than originally suggested values of 100-1000 Msolar/yr.Comment: 17 pages, 6 figures, ApJ, in pres
Keck Spectroscopy of Candidate Proto-globular Clusters in NGC 1275
Keck spectroscopy of 5 proto-globular cluster candidates in NGC 1275 has been
combined with HST WFPC2 photometry to explore the nature and origin of these
objects and discriminate between merger and cooling flow scenarios for globular
cluster formation. The objects we have studied are not HII regions, but rather
star clusters, yet their integrated spectral properties do not resemble young
or intermediate age Magellanic Cloud clusters or Milky Way open clusters. The
clusters' Balmer absorption appears to be too strong to be consistent with any
of the standard Bruzual & Charlot evolutionary models at any metallicity. If
these models are adopted, an IMF which is skewed to high masses provides a
better fit to the data. A truncated IMF with a mass range of 2-3 Mo reproduces
the observed Balmer equivalent widths and colors at about 450 Myr. Formation in
a continuous cooling flow appears to be ruled out since the age of the clusters
is much larger than the cooling time, the spatial scale of the clusters is much
smaller than the cooling flow radius, and the deduced star formation rate in
the cooling flow favors a steep rather than a flat IMF. A merger would have to
produce clusters only in the central few kpc, presumably from gas in the
merging galaxies which was channeled rapidly to the center. Widespread shocks
in merging galaxies cannot have produced these clusters. If these objects are
confirmed to have a relatively flat, or truncated, IMF it is unclear whether or
not they will evolve into objects we would regard as bona fide globular
clusters.Comment: 30 pages (AAS two column style, including 9 tables and 7 figures) to
appear in the AJ (August issue), also available at
http://www.ucolick.org/~mkissler/Sages/sages.html (with a full resolution
Fig.1) Revised Version: previous posted version was an uncorrect ealier
iteration, parts of the text, tables and figures changed. The overall
conclusions remain unchange
On the Nature of the NGC 1275 System
Sub-arcsecond images, taken in B, R, and H-Alpha filters, and area
spectroscopy obtained with the WIYN 3.5-m telescope provide the basis for an
investigation of the unusual structures in the stellar body and ionized gas in
and around the Perseus cluster central galaxy, NGC 1275. Our H-Alpha filter is
tuned to gas at the velocity of NGC 1275, revealing complex, probably
unresolved, small-scale features in the extended ionized gas, located up to
50/h kpc from NGC 1275. The mean H-Alpha surface brightness varies little along
the outer filaments; this, together with the complex excitation state
demonstrated by spectra, imply that the filaments are likely to be tubes, or
ribbons, of gas. The morphology, location and inferred physical parameters of
the gas in the filaments are consistent with a model whereby the filaments form
through compression of the intracluster gas by relativistic plasma emitted from
the active nucleus of NGC 1275. Imaging spectroscopy with the Densepak fiber
array on WIYN suggests partial rotational support of the inner component of low
velocity ionized gas. We confirm and extend evidence for features in the
stellar body of NGC 1275, and identify outer stellar regions containing very
blue, probably very young, star clusters. We interpret these as evidence for
recent accretion of a gas-rich system, with subsequent star formation. We
suggest that two main processes, which may be causally connected, are
responsible for the rich phenomenology of the NGC 1275 system -- NGC 1275
experienced a recent merger/interaction with a group of gas-rich galaxies, and
recent outflows from its AGN have compressed the intracluster gas, and perhaps
the gas in the infalling galaxies, to produce a complex web of filaments.
(Abridged)Comment: AJ, accepted; a recommended full resolution version is available at
http://www.astro.wisc.edu/~chris/pera.p
Ultraviolet Imaging Observations of the cD Galaxy in Abell 1795: Further Evidence for Massive Star Formation in a Cooling Flow
We present images from the Ultraviolet Imaging Telescope of the Abell 1795
cluster of galaxies. We compare the cD galaxy morphology and photometry of
these data with those from existing archival and published data. The addition
of a far--UV color helps us to construct and test star formation model
scenarios for the sources of UV emission. Models of star formation with rates
in the range \sim5-20M_{\sun}yr indicate that the best fitting models
are those with continuous star formation or a recent ( Myr old) burst
superimposed on an old population. The presence of dust in the galaxy,
dramatically revealed by HST images complicates the interpretation of UV data.
However, we find that the broad--band UV/optical colors of this cD galaxy can
be reasonably matched by models using a Galactic form for the extinction law
with . We also briefly discuss other objects in the large UIT
field of view.Comment: To appear in the Astrophysical Journal. 14 AAS preprint style pages
plus 7 figure
Norghum Sorghum Culture : An Early Combine Grain Sorghum
Guide for norghum sorghum culture. Addresses seedbed preparation, seed treatment, time of planting, method of planting, rate of planting, sorghum plates for corn planters, depths of planting, harvesting, threshing, and storage
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Recent results and perspectives on cosmic backgrounds from radio to far-infrared
© 2019 World Scientific Publishing Company. Cosmological and astrophysical surveys from radio to far-infrared, in both temperature and polarization, offer a unique view of the universe properties and of the formation and evolution of its structures. The last release, close to be finalized, of the Planck mission results sets the scene for cosmological models and parameters, while the comparison with other types of data sets raises the issue of possible tensions about some parameters, first of all the Hubble constant. At the same time, on the extragalactic side, Planck carried out the deepest systematic all-sky survey of SZ galaxy clusters and detected thousands of dusty galaxies and many hundreds of extragalactic radio sources, also allowing us to investigate many specific topics, including molecular hydrogen clouds in galactic halos. The exploitation of future generation of CMB missions and the next radio facilities will allow us to deeply investigate several topics in cosmology and astrophysics, from the existence of primordial gravitational waves to the energy releases in the primeval plasma, from the dawn ages and the epoch of reionization to the formation and evolution of early galaxies and clusters, while a wide set of open astrophysical problems can be studied with future IR missions
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