1,134 research outputs found
Atomic Data for Permitted Resonance Lines of Atoms and Ions from H to Si, and S, Ar, Ca and Fe
We list vacuum wavelengths, energy levels, statistical weights, transition
probabilities and oscillator strengths for permitted resonance spectral lines
of all ions of 18 astrophysically important elements (H through Si, S, Ar, Ca,
Fe). Using a compilation of experimental energy levels, we derived accurate
wavelengths for 5599 lines of 1828 ground-term multiplets which have gf-values
calculated in the Opacity Project. We recalculated the Opacity Project
multiplet gf-values to oscillator strengths and transition probabilities of
individual lines. For completeness, we added 372 resonance lines of NeI, ArI,
FeI and FeII ions which are not covered by the Opacity Project.
Intercombination and forbidden lines are not included in the present
compilation.Comment: 6 pages of text, latex, 1 figure, 4 tables; tables in ASCII format
available at ftp://asta.pa.uky.edu/dima/lines/ or at
http://www.pa.uky.edu/~verner/atom.html Accepted by Atomic Data Nucl. Data
Table
Revisited abundance diagnostics in quasars: Fe II/Mg II ratios
Both the Fe II UV emission in the 2000- 3000 A region [Fe II (UV)] and
resonance emission line complex of Mg II at 2800 A are prominent features in
quasar spectra. The observed Fe II UV/ Mg II emission ratios have been proposed
as means to measure the buildup of the Fe abundance relative to that of the
alpha-elements C, N, O, Ne and Mg as a function of redshift. The current
observed ratios show large scatter and no obvious dependence on redshift. Thus,
it remains unresolved whether a dependence on redshift exists and whether the
observed Fe II UV/ Mg II ratios represent a real nucleosynthesis diagnostic. We
have used our new 830-level model atom for Fe+ in photoionization calculations,
reproducing the physical conditions in the broad line regions of quasars. This
modeling reveals that interpretations of high values of Fe II UV/ Mg II are
sensitive not only to Fe and Mg abundance, but also to other factors such as
microturbulence, density, and properties of the radiation field. We find that
the Fe II UV/ Mg II ratio combined with Fe II (UV)/ Fe II (Optical) emission
ratio, where Fe II (Optical) denotes Fe II emission in 4000 - 6000 A can be
used as a reliable nucleosynthesis diagnostic for the Fe/Mg abundance ratios
for the physical conditions relevant to the broad-line regions (BLRs) of
quasars. This has extreme importance for quasar observations with the Hubble
Space Telescope and also with the future James Webb Space Telescope.Comment: kverner.gzip, 9 pages, f1-5.eps; aastex.cls; aastexug.sty, ApJL in
pres
Elucidating the Correlation of the Quasar \ion{Fe}{2}/\ion{Mg}{2} Ratio with Redshift
Interpretation of the \ion{Fe}{2}(UV)/\ion{Mg}{2} emission ratios from
quasars has a major cosmological motivation. Both Fe and Mg are produced by
short-lived massive stars. In addition, Fe is produced by accreting white dwarf
supernovae somewhat after star formation begins. Therefore, we expect that the
Fe/Mg ratio will gradually decrease with redshift. We have used data from the
Sloan Digital Sky Survey to explore the dependence of the
\ion{Fe}{2}(UV)/\ion{Mg}{2} ratio on redshift and on luminosity in the redshift
range of , and we have used predictions from our 830-level model
for the \ion{Fe}{2} atom in photoionization calculations to interpret our
findings.
We have split the quasars into several groups based upon the value of their
\ion{Fe}{2}(UV)/\ion{Mg}{2} emission ratios, and then checked to see how the
fraction of quasars in each group varies with the increase of redshift. We next
examined the luminosity dependence of the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio,
and we found that beyond a threshold of \ion{Fe}{2}(UV)/\ion{Mg}{2} =~ 5, and
, the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio increases with
luminosity, as predicted by our model.
We interpret our observed variation of the \ion{Fe}{2}(UV)/\ion{Mg}{2} ratio
with redshift as a result of the correlation of redshift with luminosity in a
magnitude limited quasar sample.Comment: ApJL accepte
Social impacts of climate change in Bolivia : a municipal level analysis of the effects of recent climate change on life expectancy, consumption, poverty and inequality
This paper analyzes the direct evidence of climate change in Bolivia during the past 60 years, and estimates how these changes have affected life expectancy and consumption levels for each of the 311 municipalities in Bolivia. Contrary to the predictions of most general circulation models, the evidence shows a consistent cooling trend of about 0.2°C per decade over all highland areas, slight and scattered evidence of warming in the lowlands, and no systematic changes in precipitation. The estimations indicate that the 1°C cooling experienced in the already cold highlands over the past five decades likely has reduced consumption possibilities by about 2-3 percent in these areas. Since the much richer population in the lowlands have benefitted slightly from recent climate change, the simulations suggest that recent climate change has contributed to an increase in inequality and poverty in Bolivia. Poor and indigenous peoples in the highlands are among the most severely affected populations. No statistically significant effect on life expectancy was found.Climate Change Mitigation and Green House Gases,Science of Climate Change,Climate Change Economics,Global Environment Facility,Population Policies
Social Impacts of Climate Change in Mexico: A municipality level analysis of the effects of recent and future climate change on human development and inequality
This paper uses municipality level data to estimate the general relationships between climate, income and child mortality in Mexico. Climate was found to play only a very minor role in explaining the large differences in income levels and child mortality rates observed in Mexico. This implies that Mexico is considerably less vulnerable to expected future climate change than other countries in Latin America.Climate change, social impacts, Mexico
Social impacts of climate change in Peru : a district level analysis of the effects of recent and future climate change on human development and inequality
This paper uses district level data to estimate the general relationship between climate, income and life expectancy in Peru. The analysis finds that both incomes and life expectancy show hump-shaped relationships, with optimal average annual temperatures around 18-20ºC. These estimated relationships were used to simulate the likely effects of both past (1958-2008) and future (2008-2058) climate change. At the aggregate level, future climate change in Peru is estimated to cause a small reduction in average life expectancy of about 0.2 years. This average, however, hides much larger losses in the already hot areas as well as substantial gains in currently cold areas. Similarly, the average impact on incomes is a modest reduction of 2.3 percent, but with some districts experiencing losses of up to 20 percent and others gains of up to 13 percent. Future climate change is estimated to cause an increase in poverty (all other things equal), but to have no significant effect on the distribution of incomes.Science of Climate Change,Climate Change Mitigation and Green House Gases,Climate Change Economics,Population Policies,Global Environment Facility
Management and display of four-dimensional environmental data sets using McIDAS
Over the past four years, great strides have been made in the areas of data management and display of 4-D meteorological data sets. A survey was conducted of available and planned 4-D meteorological data sources. The data types were evaluated for their impact on the data management and display system. The requirements were analyzed for data base management generated by the 4-D data display system. The suitability of the existing data base management procedures and file structure were evaluated in light of the new requirements. Where needed, new data base management tools and file procedures were designed and implemented. The quality of the basic 4-D data sets was assured. The interpolation and extrapolation techniques of the 4-D data were investigated. The 4-D data from various sources were combined to make a uniform and consistent data set for display purposes. Data display software was designed to create abstract line graphic 3-D displays. Realistic shaded 3-D displays were created. Animation routines for these displays were developed in order to produce a dynamic 4-D presentation. A prototype dynamic color stereo workstation was implemented. A computer functional design specification was produced based on interactive studies and user feedback
Fe II Diagnostic Tools for Quasars
The enrichment of Fe, relative to alpha-elements such as O and Mg, represents
a potential means to determine the age of quasars and probe the galaxy
formation epoch.
To explore how \ion{Fe}{2} emission in quasars is linked to physical
conditions and abundance, we have constructed a 830-level \ion{Fe}{2} model
atom and investigated through photoionization calculations how \ion{Fe}{2}
emission strengths depend on non-abundance factors. We have split \ion{Fe}{2}
emission into three major wavelength bands, \ion{Fe}{2} (UV),
\ion{Fe}{2}(Opt1), and \ion{Fe}{2}(Opt2), and explore how the
\ion{Fe}{2}(UV)/\ion{Mg}{2}, \ion{Fe}{2}(UV)/\ion{Fe}{2}(Opt1) and
\ion{Fe}{2}(UV)/\ion{Fe}{2}(Opt2) emission ratios depend upon hydrogen density
and ionizing flux in broad-line regions (BLR's) of quasars. Our calculations
show that: 1) similar \ion{Fe}{2}(UV)/\ion{Mg}{2} ratios can exist over a wide
range of physical conditions; 2) the \ion{Fe}{2}(UV)/\ion{Fe}{2}(Opt1) and
\ion{Fe}{2}(UV)/\ion{Fe}{2}(Opt2) ratios serve to constrain ionizing luminosity
and hydrogen density; and 3) flux measurements of \ion{Fe}{2} bands and
knowledge of ionizing flux provide tools to derive distances to BLR's in
quasars. To derive all BLR physical parameters with uncertainties, comparisons
of our model with observations of a large quasar sample at low redshift ()
is desirable.
The STIS and NICMOS spectrographs aboard the Hubble Space Telescope (HST)
offer the best means to provide such observations.Comment: ApJ accepte
The Use of Punched Cards in Molecular Structure Determinations. IV. Approximations to the Temperature Factor
[No abstract
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