743 research outputs found
The Cold and Hot Gas Content of Fine-Structure E and S0 Galaxies
We investigate trends of the cold and hot gas content of early-type galaxies
with the presence of optical morphological peculiarities, as measured by the
fine-structure index (Sigma). HI mapping observations from the literature are
used to track the cold-gas content, and archival ROSAT PSPC data are used to
quantify the hot-gas content. We find that E and S0 galaxies with a high
incidence of optical peculiarities are exclusively X-ray underluminous and,
therefore, deficient in hot gas. In contrast, more relaxed galaxies with little
or no signs of optical peculiarities span a wide range of X-ray luminosities.
That is, the X-ray excess anticorrelates with Sigma. There appears to be no
similar trend of cold-gas content with either fine-structure index or X-ray
content. The fact that only apparently relaxed E and S0 galaxies are strong
X-ray emitters is consistent with the hypothesis that after strong disturbances
such as a merger hot-gas halos build up over a time scale of several gigayears.
This is consistent with the expected mass loss from stars.Comment: 12 pages, latex, 5 figures. Accepted for publication in A
The influence of landcover change on global terrestrial biogeochemistry
Discussions concerning global change typically concentrate on future climatic changes promulgated by changes in atmospheric chemistry, most notably increases in the so-called greenhouse gases such as CO2, CH4, and and N2O. Although the energy exchange characteristics of the Earth’s surface are an important component of climate models, the idea that changes in the terrestrial surface could also be a causal factor in climatic changes has not received much attention. Sensitivity studies with GCM’s suggested that regional climate can be dramatically changed by severe deforestation. Dickinson and Henderson-Sellers (1988) simulated the Amazon basin with complete forest cover, and then replaced with degraded grasslands. Th degraded grasslands reduced evapotranspiration so much that surface temperatures were predicted to increase by 3-5 degrees. Walker et al. (1995) used the deforestation statistics of Skole and Tucker (1993) and estimated that precipitation had been reduced by 1.2mm/day due to reductions in ET of 18% caused by landcover changes
Phyletic Trends in the Late Cenozoic Microtine Ophiomys gen. nov., from Idaho
255-271http://deepblue.lib.umich.edu/bitstream/2027.42/48417/2/ID264.pd
The Insectivores of the Hagerman Local Fauna, Upper Pliocene of Idaho
171-180http://deepblue.lib.umich.edu/bitstream/2027.42/48451/2/ID300.pd
Nash Local Fauna (Pleistocene: Aftonian) of Meade County, Kansas
317-326http://deepblue.lib.umich.edu/bitstream/2027.42/48506/2/ID357.pd
Star Clusters in the Tidal Tails of Interacting Galaxies: Cluster Populations Across a Variety of Tail Environments
We have searched for compact stellar structures within 17 tidal tails in 13
different interacting galaxies using F606W- and F814W- band images from the
Wide Field Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST). The
sample of tidal tails includes a diverse population of optical properties,
merging galaxy mass ratios, HI content, and ages. Combining our tail sample
with Knierman et al. (2003), we find evidence of star clusters formed in situ
with Mv < -8.5 and V-I < 2.0 in 10 of 23 tidal tails; we are able to identify
cluster candidates to Mv = -6.5 in the closest tails. Three tails offer clear
examples of "beads on a string" star formation morphology in V-I color maps.
Two tails present both tidal dwarf galaxy (TDG) candidates and cluster
candidates. Statistical diagnostics indicate that clusters in tidal tails may
be drawn from the same power-law luminosity functions (with logarithmic slopes
~ -2 - -2.5) found in quiescent spiral galaxies and the interiors of
interacting systems. We find that the tail regions with the largest number of
observable clusters are relatively young (< 250 Myr old) and bright (V < 24 mag
arcsec^(-2)), probably attributed to the strong bursts of star formation in
interacting systems soon after periapse. Otherwise, we find no statistical
difference between cluster-rich and cluster-poor tails in terms of many
observable characteristics, though this analysis suffers from complex,
unresolved gas dynamics and projection effects.Comment: Accepted for publication in the Astrophysical Journal. 27 pages, 8
figure
IBRD Operational Decision Framework
The IBRD Operational Decision Framework in this document is an expansion of an emerging general risk management framework under development by an interagency working group. It provides the level of detail necessary to develop a general Consequence Management Guidance Document for biological contamination remediation and restoration. It is the intent of this document to support both wide area and individual site remediation and restoration activities. This product was initiated as a portion of the IBRD Task 1 Systems Analysis to aid in identification of wide area remediation and restoration shortcomings and gaps. The draft interagency general risk management framework was used as the basis for the analysis. The initial Task 1 analysis document expanded the draft interagency framework to a higher level of resolution, building on both the logic structure and the accompanying text explanations. It was then employed in a qualitative manner to identify responsible agencies, data requirements, tool requirements, and current capabilities for each decision and task. This resulted in identifying shortcomings and gaps needing resolution. Several meetings of a joint LLNL/SNL working group reviewed and approved the initial content of this analysis. At the conclusion of Task 1, work continued on the expanded framework to generate this Operational Decision Framework which is consistent with the existing interagency general risk management framework. A large LLNL task group met repeatedly over a three-month period to develop the expanded framework, coordinate the framework with the biological remediation checklist, and synchronize the logic with the Consequence Management Plan table of contents. The expanded framework was briefed at a large table top exercise reviewing the interagency risk management framework. This exercise had representation from major US metropolitan areas as well as national agencies. This product received positive comments from the participants. Upon completion of the Operational Decision Framework, another joint LLNL/SNL working group conducted a day-long review. Identified modifications were made to the document, resulting in the included product
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