Using effective temperature and metallicity derived from SDSS spectra for image60,000 F- and G-type main-sequence stars, we develop polynomial models for estimating these parameters from the SDSS ...image and image colors. These photometric estimates have similar error properties as those determined from SDSS spectra. We apply this method to SDSS photometric data for over 2 million F/G stars and measure the unbiased metallicity distribution for a complete volume-limited sample of stars at distances between 500 pc and 8 kpc. The metallicity distribution can be exquisitely modeled using two components with a spatially varying number ratio, which correspond to disk and halo. The two components also possess the kinematics expected for disk and halo stars. The metallicity of the halo component is spatially invariant, while the median disk metallicity smoothly decreases with distance from the Galactic plane from -0.6 at 500 pc to -0.8 beyond several kiloparsecs. The absence of a correlation between metallicity and kinematics for disk stars is in a conflict with the traditional decomposition in terms of thin and thick disks. We detect coherent substructures in the kinematics-metallicity space, such as the Monoceros stream, which rotates faster than the LSR, and has a median metallicity of image, with an rms scatter of only image0.15 dex. We extrapolate our results to the performance expected from the Large Synoptic Survey Telescope (LSST) and estimate that LSST will obtain metallicity measurements accurate to 0.2 dex or better, with proper-motion measurements accurate to image0.5 mas yr super(-1), for about 200 million F/G dwarf stars within a distance limit of image100 kpc.
We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r < 20 and proper-motion measurements derived from Sloan Digital Sky Survey (SDSS) and POSS astrometry, including ...{approx}170,000 stars with radial-velocity measurements from the SDSS spectroscopic survey. Distances to stars are determined using a photometric-parallax relation, covering a distance range from {approx}100 pc to 10 kpc over a quarter of the sky at high Galactic latitudes (|b|>20{sup 0}). We find that in the region defined by 1 kpc <Z< 5 kpc and 3 kpc <R< 13 kpc, the rotational velocity for disk stars smoothly decreases, and all three components of the velocity dispersion increase, with distance from the Galactic plane. In contrast, the velocity ellipsoid for halo stars is aligned with a spherical coordinate system and appears to be spatially invariant within the probed volume. The velocity distribution of nearby (Z < 1 kpc) K/M stars is complex, and cannot be described by a standard Schwarzschild ellipsoid. For stars in a distance-limited subsample of stars (<100 pc), we detect a multi-modal velocity distribution consistent with that seen by HIPPARCOS. This strong non-Gaussianity significantly affects the measurements of the velocity-ellipsoid tilt and vertex deviation when using the Schwarzschild approximation. We develop and test a simple descriptive model for the overall kinematic behavior that captures these features over most of the probed volume, and can be used to search for substructure in kinematic and metallicity space. We use this model to predict further improvements in kinematic mapping of the Galaxy expected from Gaia and the Large Synoptic Survey Telescope.
We investigate the relationship between several previously identified Galactic halo stellar structures in the direction of Virgo using imaging and spectroscopic observations of F turnoff stars and ...blue horizontal-branch stars from SDSS and SEGUE. We show that the Sagittarius dwarf leading tidal tail does not pass through the solar neighborhood; it misses the Sun by more than 15 kpc, passing through the Galactic plane outside the solar circle. Nor is it spatially coincident with the large stellar overdensity S297+63-20.5 in the Virgo constellation. S297+63-20.5 has a distinct turnoff color and kinematics. Faint ( unk similar to 20.3) turnoff stars in S297+63-20.5 have line-of-sight, Galactic standard of rest velocities unk = 130 plus or minus 10 km s super(-1), opposite In sign to infalling Sgr tail stars. The path of the Sgr leading tidal tail is also inconsistent with the positions of some of the nearer stars with which it has been associated and whose velocities have favored models with prolate Milky Way potentials. We also show that the number densities of brighter ( unk similar to 10.8) F turnoff stars are not symmetric about the Galactic center and that this discrepancy is not primarily due to the S297+63-20.5 moving group. Either the spheroid is asymmetric about the Galactic center or there are additional substructures that conspire to be on the same side of the Galaxy as S297+63-20.5. The S297+63-20.5 overdensity in Virgo is likely associated with two other previously identified Virgo substructures: the Virgo stellar stream (VSS) and the Virgo overdensity (VOD). However, the velocity difference between the VSS and S297+63-20.5 and the difference in distance estimates between the VOD and S297+63-20.5 must be reconciled.
Wilhelm reflects on the legacy of O.L. Davis Jr as the mentor who professed the value of collective historical memory. He cites a few examples from editorials in the Journal of Curriculum and ...Supervision that illustrate Davis' passionate concern for the urgency of exercising civic memory. These include a 1995 editorial which reminds readers of the curricular focus on democratic ideas and practices in the aftermath of World War II and laments the dimming of the rhetoric and practices of democracy in today's curriculum. Wilhelm surmises that these prophetic excerpts from Davis' editorials demonstrate his profound understanding that remembrance, particularly in its collective form, is an inherently pedagogical practice.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This qualitative content analysis was conducted to determine how Mexico and Mexican people are portrayed in contemporary U.S. elementary social studies textbooks. Three textbooks from each of three ...major publishers were analyzed. Findings are presented in five sections: images and photographs, holidays, Mexican people and heroes, contested history, and portrayals of Mexican-U.S. relations. The authors identified three major themes across the textbooks including heavy emphasis on holidays and traditional folk costumes, a dearth of notable Mexican figures, and overall superficial coverage of Mexico and its people. Recommendations are provided for elementary textbook revisions that would more suitably foster cross-cultural understanding between U.S. children and their southern neighbors.
The authors, five junior scholars at the University of North Texas' College of Education, describe their collaborative efforts to develop their skills in one method of qualitative research: in-depth, ...oral history interviewing. Outcomes included understanding the importance of rapport between interviewer and interviewee, of ensuring that the interviewee's voice is heard, and of conceptual and technical preparation. (DB)
This article presents two case studies, one from Mexico and one from El Salvador, to demonstrate contrasting approaches to curriculum theorizing that promote communal agency among the traditionally ...marginalized in Latin American society. The Mexican case is a top-down education reform and decentralization process resulting in a civics curriculum at the elementary education level. The case from El Salvador is a bottom-up change process that privileges collective cultural memory from civil war survivors to promote communal agency. PUBLICATION ABSTRACT
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This ideological critique of "Espana Nuestra" reveals the presence of Spanish fascism in textual and graphic images of an elementary school social studies textbook. The analysis reveals how these ...images were arranged to foster and reinforce specific crucial elements of Spanish fascist ideology, such as national syndicalism, militant national Catholicism, and virulent anticommunism. However, few youngsters could afford the book. (103 footnotes) (MLH)
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