1,188 research outputs found

    Nimbus-7 ERB Solar Analysis Tape (ESAT) user's guide

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    Seven years and five months of Nimbus-7 Earth Radiation Budget (ERB) solar data are available on a single ERB Solar Analysis Tape (ESAT). The period covered is November 16, 1978 through March 31, 1986. The Nimbus-7 satellite performs approximately 14 orbits per day and the ERB solar telescope observes the sun once per orbit as the satellite crosses the southern terminator. The solar data were carefully calibrated and screened. Orbital and daily mean values are given for the total solar irradiance plus other spectral intervals (10 solar channels in all). In addition, selected solar activity indicators are included on the ESAT. The ESAT User's Guide is an update of the previous ESAT User's Guide (NASA TM 86143) and includes more detailed information on the solar data calibration, screening procedures, updated solar data plots, and applications to solar variability. Details of the tape format, including source code to access ESAT, are included

    Absorption-Line Probes of Gas and Dust in Galactic Superwinds

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    We discuss moderate resolution spectra of the NaD absorption-line in a sample of 32 far-IR-bright starburst galaxies. In 18 cases, the line is produced primarily by interstellar gas, and in 12 of these it is blueshifted by over 100 km/s relative to the galaxy systemic velocity. The absorption-line profiles in these outflow sources span the range from near the galaxy systemic velocity to a maximum blueshift of 400 to 600 km/s. The outflows occur in galaxies systematically viewed more nearly face-on than the others. We therefore argue that the absorbing material consists of ambient interstellar gas accelerated along the minor axis of the galaxy by a hot starburst-driven superwind. The NaD lines are optically-thick, but indirect arguments imply total Hydrogen column densities of N_H = few X 10^{21} cm^{-2}. This implies that the superwind is expelling matter at a rate comparable to the star-formation rate. This outflowing material is very dusty: we find a strong correlation between the depth of the NaD profile and the line-of-sight reddening (E(B-V) = 0.3 to 1 over regions several-to-ten kpc in size). The estimated terminal velocities of superwinds inferred from these data and extant X-ray data are typically 400 to 800 km/s, are independent of the galaxy rotation speed, and are comparable to (substantially exceed) the escape velocities for L∗L_* (dwarf) galaxies. The resulting loss of metals can establish the mass-metallicity relation in spheroids, produce the observed metallicity in the ICM, and enrich a general IGM to 10−1^{-1} solar metallicity. If the outflowing dust grains survive their journey into the IGM, their effect on observations of cosmologically-distant objects is significant.Comment: 65 pages, including 16 figures. ApJ, in pres

    Nuclear starburst-driven evolution of the central region in NGC 6764

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    We study the CO and the radiocontinuum emission in an active galaxy to analyze the interplay between the central activity and the molecular gas. We present new high-resolution observations of the CO(1-0) and CO(2-1) emission lines, and 3.5 cm and 20 cm radio continuum emission in the central region of the LINER/starburst galaxy NGC 6764. The galaxy has an outflow morphology in radio continuum, spatially coincident with the CO and Hα\alpha emission, and centered slightly off the radio continuum peak at the LINER nucleus. The total molecular gas mass in the center is about 7x10^8 \msun, using a CO luminosity to total molecular gas conversion factor that is three times lower than the standard one. CO(1-0) emission is found near the boundaries of the radio continuum emission cone. The outflow has a projected expansion velocity of 25 km/s relative to the systemic velocity of NGC6764. About 4x 10^6 \msun of molecular gas is detected in the outflow. The approximate location (~1 kpc) of the dynamical inner Lindblad resonance has been derived from the rotation curve. The peak of the CO emission is slightly (< 200 pc) offset from the peak of the radio continuum. The molecular gas has most likely been ejected by the stellar winds from the recent starburst, but the CO line ratios show indication of an interaction with the AGN. The energy released by the nuclear starburst is sufficient to explain the observed outflow, even if the data cannot exclude the AGN from being the major energy source. Comparison of the outflow with hydrodynamical simulations suggests that the nuclear starburst is 3--7 Myr old and the bubble-like outflow is still confined and not freely expanding.Comment: Accepted for publication in A&

    Family and school social capital, school burnout and academic achievement : a multilevel longitudinal analysis among Finnish pupils

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    Research on the associations between family and school social capital, school burnout and academic achievement in adolescence is scarce and the results are inconclusive. We examined if family and school social capital at the age of 13 predicts lower school burnout and better academic achievement when graduating at the age of 16. Using data from 4467 Finnish adolescents from 117 schools and 444 classes a three-level multilevel analysis was executed. School social capital, the positive and supportive relationships between students and teachers, predicted lower school burnout and better academic achievement among students. Classmates' family social capital had also significance for students' academic achievement. Our results suggest that building school social capital is an important aspect of school health and education policies and practices.Peer reviewe

    Strong Interactions of Single Atoms and Photons near a Dielectric Boundary

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    Modern research in optical physics has achieved quantum control of strong interactions between a single atom and one photon within the setting of cavity quantum electrodynamics (cQED). However, to move beyond current proof-of-principle experiments involving one or two conventional optical cavities to more complex scalable systems that employ N >> 1 microscopic resonators requires the localization of individual atoms on distance scales < 100 nm from a resonator's surface. In this regime an atom can be strongly coupled to a single intracavity photon while at the same time experiencing significant radiative interactions with the dielectric boundaries of the resonator. Here, we report an initial step into this new regime of cQED by way of real-time detection and high-bandwidth feedback to select and monitor single Cesium atoms localized ~100 nm from the surface of a micro-toroidal optical resonator. We employ strong radiative interactions of atom and cavity field to probe atomic motion through the evanescent field of the resonator. Direct temporal and spectral measurements reveal both the significant role of Casimir-Polder attraction and the manifestly quantum nature of the atom-cavity dynamics. Our work sets the stage for trapping atoms near micro- and nano-scopic optical resonators for applications in quantum information science, including the creation of scalable quantum networks composed of many atom-cavity systems that coherently interact via coherent exchanges of single photons.Comment: 8 pages, 5 figures, Supplemental Information included as ancillary fil

    Dust grain growth in the interstellar medium of 5<z<6.5 quasars

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    We investigate whether stellar dust sources i.e. asymptotic giant branch (AGB) stars and supernovae (SNe) can account for dust detected in 5<z<6.5 quasars (QSOs). We calculate the required dust yields per AGB star and per SN using the dust masses of QSOs inferred from their millimeter emission and stellar masses approximated as the difference between the dynamical and the H_2 gas masses of these objects. We find that AGB stars are not efficient enough to form dust in the majority of the z>5 QSOs, whereas SNe may be able to account for dust in some QSOs. However, they require very high dust yields even for a top-heavy initial mass function. This suggests additional non-stellar dust formation mechanism e.g. significant dust grain growth in the interstellar medium of at least three out of nine z>5 QSOs. SNe (but not AGB stars) may deliver enough heavy elements to fuel this growth.Comment: A&A, accepted. 5 pages, 2 figures, 2 table

    Molecular Gas and the Modest Star Formation Efficiency in the ``Antennae'' Galaxies: Arp~244=NGC 4038/39

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    (abridged) We report here a factor of 5.7 higher total CO flux in Arp~244 (the ``Antennae'' galaxies) than that previously accepted in the literature (thus a total molecular gas mass of 1.5x1010^{10} Msun), based on our fully sampled CO(1-0) observations at the NRAO 12m telescope. Our observations show that the molecular gas peaks predominately in the disk-disk overlap region between the nuclei, similar to the far-infrared (FIR) and mid-infrared (MIR) emission. The bulk of the molecular gas is forming into stars with a normal star formation efficiency (SFE) L_{IR}/M(H_2) \approx 4.2 Lsun/Msun, same as that of giant molecular clouds in the Galactic disk. Additional supportive evidence is the extremely low fraction of the dense molecular gas in Arp~244, revealed by our detections of the HCN(1-0) emission. We estimate the local SFE indicated by the ratio map of the radio continuum to CO(1-0) emission. Remarkably, the local SFE stays roughly same over the bulk of the molecular gas distribution. Only some localized regions show the highest radio-to-CO ratios that we have identified as the sites of the most intense starbursts with SFE >~ 20 Lsun/Msun. These starburst regions are confined exclusively in the dusty patches seen in the HST images near the CO and FIR peaks where presumably the violent starbursts are heavily obscured. Nevertheless, recent large-scale star formation is going on throughout the system, yet the measured level is more suggestive of a moderate starburst (SFE >~ 10 Lsun/Msun) or a weak to normal star formation (SFE ~ 4 Lsun/Msun). The overall starburst from the bulk of the molecular gas is yet to be initiated as most of the gas further condenses into kpc scale in the final coalescence.Comment: 31 pages including 3 postscript & 10 gif figures, final version to appear in ApJ, 2001 Feb. 10. A single .ps.gz file can be down-loaded from: http://spider.ipac.caltech.edu/staff/gao/Papers

    Educating a syndrome? Seeking a balance between identifying a learning profile and delivering inclusive education

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    This article summarizes research related to pedagogical approaches to special education, and characteristics of teacher's attitudes and beliefs that supports effective inclusion practices. Additionally, the author summarizes factors that may both enable and disable children with DS's progress, and notes speech and language characteristics from research to date

    Journal Staff

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    We present the first measurements of the differential cross section d sigma/dp(T)(gamma) for the production of an isolated photon in association with at least two b-quark jets. The measurements consider photons with rapidities vertical bar y(gamma)vertical bar &lt; 1.0 and transverse momenta 30 &lt; p(T)(gamma) &lt; 200 GeV. The b-quark jets are required to have p(T)(jet) &gt; 15 GeVand vertical bar y(jet)vertical bar &lt; 1.5. The ratio of differential production cross sections for gamma + 2 b-jets to gamma + b-jet as a function of p(T)(gamma) is also presented. The results are based on the proton-antiproton collision data at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The measured cross sections and their ratios are compared to the next- to- leading order perturbative QCD calculations as well as predictions based on the k(T)- factorization approach and those from the sherpa and pythia Monte Carlo event generators
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