12,392 research outputs found

    University of Missouri research reactor| Expanding and re-licensing a nuclear facility

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    The implementation and evaluation of a sequential, structured approach for teaching LogoWriter to classroom teachers

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    The goal of this exploratory study was to implement and evaluate a Logo inservice model which focused on effective principles of staff development and emphasized Logo problem solving using teacher-mediated intervention strategies. The model was designed to facilitate teacher use of Logo in their classrooms;Subjects for this study included 19 elementary teachers and media specialists from the Ames Community Schools. Subjects completed The Stages of Concern Questionnaire (SoCQ), the LogoWriter Basic Comprehension Test, END-OF-DAY inventories, and the Inservice Evaluation LogoWriter Workshop Instrument. Additional outcome measures included projects shared during a final inservice sharing session, and questions, worksheets, and tape recordings from a follow-up discussion session;Results measuring change in teacher stages of concern indicated all participants, except one, made significant shifts to higher stages focusing on using Logo with students. Seven participants were identified as showing potential nonuse tendencies in implementing Logo into their classrooms. Support for Logo implementation was found for structured instructional teaching balanced with opportunities for discovery-based learning;Results from teacher self report of mastery of LogoWriter knowledge and skills indicated that subjects reported mastery of 20 out of 27 objectives. In addition, results from the LogoWriter Basic Comprehension Test validated these self reports. A t-test pairs procedure on the LogoWriter test indicated that there was a significant difference between the pre- and posttest group means (p \u3c.001). Auxiliary findings included results in teacher perceptions of Logo and gender differences;Evaluation of the Logo inservice provided positive support for the Logo inservice approach providing organization and structure and opportunity for individual exploration. Subjects also responded favorably to the inservice sharing session of Logo projects and teaching strategies, and the follow-up sharing session discussing implementation, curriculum integration, classroom management, and Logo procedural concerns. The study found that a structured Logo inservice appears to be a positive step in promoting future use of Logo in the classroom

    The MASSIVE Survey - VIII. Stellar Velocity Dispersion Profiles and Environmental Dependence of Early-Type Galaxies

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    We measure the radial profiles of the stellar velocity dispersions, σ(R)\sigma(R), for 90 early-type galaxies (ETGs) in the MASSIVE survey, a volume-limited integral-field spectroscopic (IFS) galaxy survey targeting all northern-sky ETGs with absolute KK-band magnitude MK<−25.3M_K < -25.3 mag, or stellar mass M∗>4×1011M⊙M_* > 4 \times 10^{11} M_\odot, within 108 Mpc. Our wide-field 107" ×\times 107" IFS data cover radii as large as 40 kpc, for which we quantify separately the inner (2 kpc) and outer (20 kpc) logarithmic slopes γinner\gamma_{\rm inner} and γouter\gamma_{\rm outer} of σ(R)\sigma(R). While γinner\gamma_{\rm inner} is mostly negative, of the 56 galaxies with sufficient radial coverage to determine γouter\gamma_{\rm outer} we find 36% to have rising outer dispersion profiles, 30% to be flat within the uncertainties, and 34% to be falling. The fraction of galaxies with rising outer profiles increases with M∗M_* and in denser galaxy environment, with 10 of the 11 most massive galaxies in our sample having flat or rising dispersion profiles. The strongest environmental correlations are with local density and halo mass, but a weaker correlation with large-scale density also exists. The average γouter\gamma_{\rm outer} is similar for brightest group galaxies, satellites, and isolated galaxies in our sample. We find a clear positive correlation between the gradients of the outer dispersion profile and the gradients of the velocity kurtosis h4h_4. Altogether, our kinematic results suggest that the increasing fraction of rising dispersion profiles in the most massive ETGs are caused (at least in part) by variations in the total mass profiles rather than in the velocity anisotropy alone.Comment: Accepted/in press, MNRA

    The MASSIVE Survey - VII. The Relationship of Angular Momentum, Stellar Mass and Environment of Early-Type Galaxies

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    We analyse the environmental properties of 370 local early-type galaxies (ETGs) in the MASSIVE and ATLAS3D surveys, two complementary volume-limited integral-field spectroscopic (IFS) galaxy surveys spanning absolute KK-band magnitude −21.5>MK>−26.6-21.5 > M_K > -26.6, or stellar mass 8×109<M∗<2×1012M⊙8 \times 10^{9} < M_* < 2 \times 10^{12} M_\odot. We find these galaxies to reside in a diverse range of environments measured by four methods: group membership (whether a galaxy is a brightest group/cluster galaxy, satellite, or isolated), halo mass, large-scale mass density (measured over a few Mpc), and local mass density (measured within the NNth neighbour). The spatially resolved IFS stellar kinematics provide robust measurements of the spin parameter λe\lambda_e and enable us to examine the relationship among λe\lambda_e, M∗M_*, and galaxy environment. We find a strong correlation between λe\lambda_e and M∗M_*, where the average λe\lambda_e decreases from ∼0.4\sim 0.4 to below 0.1 with increasing mass, and the fraction of slow rotators fslowf_{\rm slow} increases from ∼10\sim 10% to 90%. We show for the first time that at fixed M∗M_*, there are almost no trends between galaxy spin and environment; the apparent kinematic morphology-density relation for ETGs is therefore primarily driven by M∗M_* and is accounted for by the joint correlations between M∗M_* and spin, and between M∗M_* and environment. A possible exception is that the increased fslowf_{\rm slow} at high local density is slightly more than expected based only on these joint correlations. Our results suggest that the physical processes responsible for building up the present-day stellar masses of massive galaxies are also very efficient at reducing their spin, in any environment.Comment: Accepted to MNRA

    The MASSIVE Survey XIII -- Spatially Resolved Stellar Kinematics in the Central 1 kpc of 20 Massive Elliptical Galaxies with the GMOS-North Integral-Field Spectrograph

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    We use observations from the GEMINI-N/GMOS integral-field spectrograph (IFS) to obtain spatially resolved stellar kinematics of the central ∼1\sim 1 kpc of 20 early-type galaxies (ETGs) with stellar masses greater than 1011.7M⊙10^{11.7} M_\odot in the MASSIVE survey. Together with observations from the wide-field Mitchell IFS at McDonald Observatory in our earlier work, we obtain unprecedentedly detailed kinematic maps of local massive ETGs, covering a scale of ∼0.1−30\sim 0.1-30 kpc. The high (∼120\sim 120) signal-to-noise of the GMOS spectra enable us to obtain two-dimensional maps of the line-of-sight velocity, velocity dispersion σ\sigma, as well as the skewness h3h_3 and kurtosis h4h_4 of the stellar velocity distributions. All but one galaxy in the sample have σ(R)\sigma(R) profiles that increase towards the center, whereas the slope of σ(R)\sigma(R) at one effective radius (ReR_e) can be of either sign. The h4h_4 is generally positive, with 14 of the 20 galaxies having positive h4h_4 within the GMOS aperture and 18 having positive h4h_4 within 1Re1 R_e. The positive h4h_4 and rising σ(R)\sigma(R) towards small radii are indicative of a central black hole and velocity anisotropy. We demonstrate the constraining power of the data on the mass distributions in ETGs by applying Jeans anisotropic modeling (JAM) to NGC~1453, the most regular fast rotator in the sample. Despite the limitations of JAM, we obtain a clear χ2\chi^2 minimum in black hole mass, stellar mass-to-light ratio, velocity anisotropy parameters, and the circular velocity of the dark matter halo.Comment: Accepted to Ap

    The MASSIVE Survey - X. Misalignment between Kinematic and Photometric Axes and Intrinsic Shapes of Massive Early-Type Galaxies

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    We use spatially resolved two-dimensional stellar velocity maps over a 107"×107"107"\times 107" field of view to investigate the kinematic features of 90 early-type galaxies above stellar mass 1011.5M⊙10^{11.5}M_\odot in the MASSIVE survey. We measure the misalignment angle Ψ\Psi between the kinematic and photometric axes and identify local features such as velocity twists and kinematically distinct components. We find 46% of the sample to be well aligned (Ψ<15∘\Psi < 15^{\circ}), 33% misaligned, and 21% without detectable rotation (non-rotators). Only 24% of the sample are fast rotators, the majority of which (91%) are aligned, whereas 57% of the slow rotators are misaligned with a nearly flat distribution of Ψ\Psi from 15∘15^{\circ} to 90∘90^{\circ}. 11 galaxies have Ψ≳60∘\Psi \gtrsim 60^{\circ} and thus exhibit minor-axis ("prolate") rotation in which the rotation is preferentially around the photometric major axis. Kinematic misalignments occur more frequently for lower galaxy spin or denser galaxy environments. Using the observed misalignment and ellipticity distributions, we infer the intrinsic shape distribution of our sample and find that MASSIVE slow rotators are consistent with being mildly triaxial, with mean axis ratios of b/a=0.88b/a=0.88 and c/a=0.65c/a=0.65. In terms of local kinematic features, 51% of the sample exhibit kinematic twists of larger than 20∘20^{\circ}, and 2 galaxies have kinematically distinct components. The frequency of misalignment and the broad distribution of Ψ\Psi reported here suggest that the most massive early-type galaxies are mildly triaxial, and that formation processes resulting in kinematically misaligned slow rotators such as gas-poor mergers occur frequently in this mass range.Comment: Accepted to MNRA
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