4,998 research outputs found
Age and Metallicity Estimations in Old Stellar Populations from Stromgren Photometry
We present a new technique to determine age and metallicity of old stellar
populations (globular clusters and elliptical galaxies) using an iterative
principal component analysis on narrow band (Str\"omgren) colors. Our technique
is capable of reproducing globular cluster [Fe/H] values to 0.02 dex and CMD
ages to 1.0 Gyrs. We also present preliminary results on the application of our
technique to a sample of high mass, field ellipticals and low mass, cluster
dwarf ellipticals. We confirm the results of earlier studies which find that
globular clusters increase in metallicity with age and that age and metallicity
increase with galaxy mass. However, we find that dwarf ellipticals deviate from
the elliptical sequence by having little to no correlation between age and
metallicity.Comment: 8 pages IAU LaTeX, 5 figures, contributing talk IAU #198 Near-Field
Cosmology with Dwarf Elliptical Galaxie
Age and Metallicities of Cluster Galaxies: A1185 and Coma
We present age and metallicities determinations based on narrow band continuum colors for the galaxies in the rich clusters A1185 and Coma. Using a new technique to extract luminosity-weighted age and [Fe/H] values for non-star-forming galaxies, we find that both clusters have two separate populations based on these parameters. One population is old ( 11 Gyrs) with a distinct mass-metallicity relation. The second population is slightly younger ( 9 Gyrs) with lower metallicities and lower stellar masses. We find detectable correlations between age and galaxy mass in both populations such that older galaxies are more massive and have higher mean metallicities, confirming previous work with line indices for the same type of galaxies in other clusters (Kelson et al 2006, Thomas et al 2005). Our results imply shorter durations for higher mass galaxies, in contradiction to the predictions of classic galactic wind models. Since we also find a clear mass-metallicity relation for these galaxies, then we conclude that star formation was more efficient for higher mass galaxies, a scenario described under the inverse wind models (Matteucci 1994). With respect to cluster environmental effects, we find there is a significant correlation between galaxy mean age and distance from the cluster center, such that older galaxies inhabit the core. This relationship would nominally support hierarchical scenarios of galaxy formation (younger age in lower density regions); however, environmental effects probably have larger signature in the sample and present-day galaxies are remnants from an epoch of quenching of initial star formation, which would result in the same age gradients
Promotion and tenure for community-engaged research: An examination of promotion and tenure support for community-engaged research at three universities collaborating through a Clinical and Translational Science Award
This is the pre-peer reviewed version of the following article: Marrero DG, Hardwick EJ, Staten LK, Savaiano DA, Odell JD, Comer KF, Saha C. Promotion and Tenure for Community-Engaged Research: An Examination of Promotion and Tenure Support for Community-Engaged Research at Three Universities Collaborating through a Clinical and Translational Science Award. Clin Transl Sci. 2013 Jun;6(3):204-8, which has been published in final form at http://dx.doi.org/10.1111/cts.12061.Introduction. Community engaged health research, an approach to research which includes the participation of communities, promotes the translation of research to address and improve social determinants of health. As a way to encourage community engaged research, the National Institutes of Health required applicants to the Clinical and Translational Science Award (CTSA) to include a community engagement component. Although grant-funding may support an increase in community engaged research, faculty also respond to the rewards and demands of university promotion and tenure standards. This paper measures faculty perception of how three institutions funded by a CTSA support community engaged research in the promotion and tenure process. Methods: At three institutions funded by a CTSA, tenure track and non-tenure track faculty responded to a survey regarding perceptions of how promotion and tenure committees value community engaged research. Results: Faculty view support for community engaged research with some reserve. Only 36% agree that community engaged research is valued in the promotion and tenure process. Discussion: Encouraging community engaged scholarship requires changing the culture and values behind promotion and tenure decisions. Institutions will increase community engaged research and more faculty will adopt its principles, when it is rewarded by promotion and tenure committees
Современные технические средства в работе секретаря
The article examines the technical devices used in the secretary work. Guided books and magazines
for secretarial business, makes recommendations for the proper selection and use of technical devices. Furthermore, in this article the author gives examples of the most popular and commonly used programs for personal computers. All of these techniques can significantly reduce the cost of working time and improve the
quality of performing their job duties
Physical Conditions in Low Ionization Regions of the Orion Nebula
We reexamine the spectroscopic underpinnings of recent claims that low ionization (O(I)) and (Fe(II)) lines from the Orion H(II) region are produced in a region where the iron-carrying grains have been destroyed and the electron density is surprisingly high. Our new HST and CTIO observations show that previous reported detections of(O(I)) lambda 5577 were strongly affected by telluric emission. Our line limits consistent with a moderate density (approx. 10(exp 4)/cu. cm photoionized gas. We show that a previously proposed model of the Orion H(II) region reproduces the observed (O(I)) and (Fe(II)) spectrum. These lines are fully consistent with formation in a moderate density dusty region
Late-Type Near-Contact Eclipsing Binary [HH97] FS Aur-79
The secondary photometric standard star #79 for the FS Aur field (Henden &
Honeycutt 1997) designated as [HH97] FS Aur-79 (GSC 1874 399) is a short period
(0.2508 days) eclipsing binary whose light curve is a combination of the
Lyr and BY Dra type variables. High signal-to-noise multi-color
photometry were obtained using the USNO 1-m telescope. These light curves show
asymmetry at quadrature phases (O'Connell effect), which can be modeled with
the presence of star spots. A low resolution spectrum obtained with the 3.5-m
WIYN telescope at orbital phase 0.76 is consistent with a spectral type of dK7e
and dM3e. A radial velocity curve for the primary star was constructed using
twenty-four high resolution spectra from the 9.2 m HET. Spectra show H-alpha
and H-beta in emission confirming chromospheric activity and possibly the
presence of circumstellar material. Binary star models that simultaneously fit
the U, B, V, R and RV curves are those with a primary star of mass 0.59+-0.02
Msun, temperature 4100+-25 K, mean radius of 0.67 Rsun, just filling its Roche
lobe and a secondary star of mass 0.31+-0.09 Msun, temperature 3425+-25 K, mean
radius of 0.48 Rsun, just within its Roche lobe. An inclination angle of 83+-2
degrees with a center of mass separation of 1.62 Rsun is also derived. Star
spots, expected for a rotation period of less than a day, had to be included in
the modeling to fit the O'Connell effect
Tensile Fracture of Welded Polymer Interfaces: Miscibility, Entanglements and Crazing
Large-scale molecular simulations are performed to investigate tensile
failure of polymer interfaces as a function of welding time . Changes in the
tensile stress, mode of failure and interfacial fracture energy are
correlated to changes in the interfacial entanglements as determined from
Primitive Path Analysis. Bulk polymers fail through craze formation, followed
by craze breakdown through chain scission. At small welded interfaces are
not strong enough to support craze formation and fail at small strains through
chain pullout at the interface. Once chains have formed an average of about one
entanglement across the interface, a stable craze is formed throughout the
sample. The failure stress of the craze rises with welding time and the mode of
craze breakdown changes from chain pullout to chain scission as the interface
approaches bulk strength. The interfacial fracture energy is calculated
by coupling the simulation results to a continuum fracture mechanics model. As
in experiment, increases as before saturating at the average
bulk fracture energy . As in previous simulations of shear strength,
saturation coincides with the recovery of the bulk entanglement density. Before
saturation, is proportional to the areal density of interfacial
entanglements. Immiscibiltiy limits interdiffusion and thus suppresses
entanglements at the interface. Even small degrees of immisciblity reduce
interfacial entanglements enough that failure occurs by chain pullout and
The Marshall Space Flight Center Development of Mirror Modules for the ART-XC Instrument aboard the Spectrum-Roentgen-Gamma Mission
The Marshall Space Flight Center (MSFC) is developing x-ray mirror modules for the ART-XC instrument on board the Spectrum-Roentgen Gamma Mission under a Reimbursable Agreement between NASA and the Russian Space Research Institute (IKI.) ART-XC will consist of seven co-aligned x-ray mirror modules with seven corresponding CdTe focal plane detectors. Currently, four of the modules are being fabricated by the Marshall Space Flight Center (MSFC.) Each MSFC module consist of 28 nested Ni/Co thin shells giving an effective area of 65 sq cm at 8 keV, response out to 30 keV, and an angular resolution of 45 arcsec or better HPD. Delivery of these modules to the IKI is scheduled for summer 2013. We present a status of the ART x-ray modules development at the MSFC
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