35 research outputs found
Photoemission Beyond the Sudden Approximation
The many-body theory of photoemission in solids is reviewed with emphasis on
methods based on response theory. The classification of diagrams into loss and
no-loss diagrams is discussed and related to Keldysh path-ordering
book-keeping. Some new results on energy losses in valence-electron
photoemission from free-electron-like metal surfaces are presented. A way to
group diagrams is presented in which spectral intensities acquire a
Golden-Rule-like form which guarantees positiveness. This way of regrouping
should be useful also in other problems involving spectral intensities, such as
the problem of improving the one-electron spectral function away from the
quasiparticle peak.Comment: 18 pages, 11 figure
PHANGS-JWST First Results: A Global and Moderately Resolved View of Mid-Infrared and CO Line Emission from Galaxies at the Start of the JWST Era
We explore the relationship between mid-infrared (mid-IR) and CO rotational
line emission from massive star-forming galaxies, which is one of the tightest
scalings in the local universe. We assemble a large set of unresolved and
moderately ( kpc) spatially resolved measurements of CO (1-0) and CO
(2-1) intensity, , and mid-IR intensity, , at 8, 12,
22, and 24m. The vs. relationship is reasonably
described by a power law with slopes and normalization K km s at MJy sr. Both the slopes
and intercepts vary systematically with choice of line and band. The comparison
between the relations measured for CO~(1-0) and CO (2-1) allow us to infer that
, in good agreement with other work. The
m and m bands, with strong PAH features, show steeper CO vs.
mid-IR slopes than the m and m, consistent with PAH emission
arising not just from CO-bright gas but also from atomic or CO-dark gas. The
CO-to-mid-IR ratio correlates with global galaxy stellar mass () and
anti-correlates with SFR/. At kpc resolution, the first four
PHANGS-JWST targets show CO to mid-IR relationships that are quantitatively
similar to our larger literature sample, including showing the steep
CO-to-mid-IR slopes for the JWST PAH-tracing bands, although we caution that
these initial data have a small sample size and span a limited range of
intensities.Comment: 29 pages, 13 figures, key quantitative results in Table 3, Accepted
as part of a PHANGS-JWST Focus Issue to appear in Ap
PHANGS-ALMA data processing and pipeline
Instrumentatio
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Radionuclide resuspension across ecosystems and environmental disturbances
Exposure assessment from radionuclides and other soil-bound contaminants often requires quantifying the amount of contaminant resuspended in the air. Rates and controlling factors of radionuclide resuspension and wind erosion of soil are clearly related but have largely been studied separately. Here, we review both and then integrate wind erosion measurements with the radiological resuspension paradigm to provide better estimates of resuspension factors across a broad range of ecosystems and environmental conditions. Radionuclide resuspension by wind was initially investigated during the era of aboveground nuclear weapons testing. Predictive dose models were developed from empirically-derived ratios of air and soil concentrations, otherwise called the resuspension factor. Resuspension factors were shown to generally predict radionuclide concentrations in air, but they were site-specific and largely derived from the arid and semi-arid environments surrounding nuclear weapons testing locations. In contrast, wind erosion studies from the agricultural and environmental sciences have produced more mechanistic models and a relatively robust data set of wind erosion rates and model parameters across a range of ecosystems. We sequentially show the mathematics linking measured sediment flux from wind erosion rate measurements to resuspension factors using the concept of transport capacity and its relationship to the deposition velocity. We also describe the conceptual framework describing how resuspension factors change through time and the mathematical models describing this decrease. We then show how vertical mass flux measurements across ecosystems were categorized and used to calculate ecosystem-based resuspension factors. These calculations allow generalized estimation of radionuclide resuspension factors across ecosystem types as a function of disturbance and as input for dose calculations.24 month embargo; available online 25 March 2021This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Demandes de congés de MM. d'Egmont-Pignatelli, Chastenet de Puységur et Colonna Cesari de Rocca
Chastenet de Puységur Jean-Auguste de, Colonna de Cesari-Rocca Pierre-Paul, comte, Egmont Pignatelli Casimir, comte d'. Demandes de congés de MM. d'Egmont-Pignatelli, Chastenet de Puységur et Colonna Cesari de Rocca. In: Archives Parlementaires de 1787 à 1860 - Première série (1787-1799) Tome XVI - Du 31 mai au 8 juillet 1790. Paris : Librairie Administrative P. Dupont, 1883. p. 250
Modeling dust emission in the Magellanic Clouds with Spitzer and Herschel
International audienceContext. Dust modeling is crucial to infer dust properties and budget for galaxy studies. However, there are systematic disparities between dust grain models that result in corresponding systematic differences in the inferred dust properties of galaxies. Quantifying these systematics requires a consistent fitting analysis.Aims. We compare the output dust parameters and assess the differences between two dust grain models, the DustEM model and THEMIS. In this study, we use a single fitting method applied to all the models to extract a coherent and unique statistical analysis.Methods. We fit the models to the dust emission seen by Spitzer and Herschel in the Small and Large Magellanic Clouds (SMC and LMC). The observations cover the infrared (IR) spectrum from a few microns to the sub-millimeter range. For each fitted pixel, we calculate the full n-D likelihood based on a previously described method. The free parameters are both environmental (U, the interstellar radiation field strength; αISRF, power-law coefficient for a multi-U environment; Ω∗, the starlight strength) and intrinsic to the model (Yi: abundances of the grain species i; αsCM20, coefficient in the small carbon grain size distribution).Results. Fractional residuals of five different sets of parameters show that fitting THEMIS brings a more accurate reproduction of the observations than the DustEM model. However, independent variations of the dust species show strong model-dependencies. We find that the abundance of silicates can only be constrained to an upper-limit and that the silicate/carbon ratio is different than that seen in our Galaxy. In the LMC, our fits result in dust masses slightly lower than those found in the literature, by a factor lower than 2. In the SMC, we find dust masses in agreement with previous studies
Demandes de congés de MM. d'Egmont-Pignatelli, Chastenet de Puységur et Colonna Cesari de Rocca
Chastenet de Puységur Jean-Auguste du, Colonna de Cesari-Rocca Comte Pierre-Paul, Egmont Pignatelli Casimir, comte d'. Demandes de congés de MM. d'Egmont-Pignatelli, Chastenet de Puységur et Colonna Cesari de Rocca. In: Archives Parlementaires de 1787 à 1860 - Première série (1787-1799) Tome XVI - Du 31 mai au 8 juillet 1790. Paris : Librairie Administrative P. Dupont, 1883. p. 250