5,511 research outputs found

    The IRX-β\beta relation: Insights from simulations

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    We study the relationship between the UV continuum slope and infrared excess (IRXLIR/LFUV\equiv L_{\rm IR}/L_{\rm FUV}) predicted by performing dust radiative transfer on a suite of hydrodynamical simulations of galaxies. Our suite includes both isolated disk galaxies and mergers intended to be representative of galaxies at both z0z \sim 0 and z23z \sim 2-3. Our low-redshift isolated disks and mergers often populate a region around the the locally calibrated \citet[][M99]{M99} relation but move well above the relation during merger-induced starbursts. Our high-redshift simulated galaxies are blue and IR-luminous, which makes them lie above the M99 relation. The value of UV continuum slope strongly depends on the dust type used in the radiative transfer calculations: Milky Way-type dust leads to significantly more negative (bluer) slopes compared with Small Magellanic Cloud-type dust. The effect on β\beta due to variations in the dust composition with galaxy properties or redshift can dominate over other sources of β\beta variations and is the dominant model uncertainty. The dispersion in β\beta is anticorrelated with specific star formation rate and tends to be higher for the z23z \sim 2-3 simulations. In the actively star-forming z23z \sim 2-3 simulated galaxies, dust attenuation dominates the dispersion in β\beta, whereas in the z0z \sim 0 simulations, the contributions of SFH variations and dust are similar. For low-SSFR systems at both redshifts, SFH variations dominate the dispersion. Finally, the simulated z23z \sim 2-3 isolated disks and mergers both occupy a region in the \irxbeta\ plane consistent with observed z23z \sim 2-3 dusty star-forming galaxies (DSFGs). Thus, contrary to some claims in the literature, the blue colors of high-z DSFGs do not imply that they are short-lived starbursts.Comment: 20 pages+a 4-page appendix, Accepted for publication at Ap

    There is still no evidence that videogames “harm” minors

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    Mass shootings in recent years such as those Newtown and Aurora in 2012 have once again placed the spotlight onto the role of violent videogames in encouraging youth violence. But is there a link between the two? Christopher J. Ferguson argues that the evidence shows that videogames do not cause violence, and that any alarmist claims that they do are based on minimal data. He writes that moral panics, such as those that arise after mass shootings, encourage psychologists to make extreme claims in order to gain prestige, headlines and grant funding

    Nonprofit Georgia: Geography

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    This pamphlet summarizes statistics on the nonprofit sector in Georgia, assembled and analyzed by a Nonprofit Studies Program research team. The focus of this second report in the "Nonprofit Georgia" series is the geographic distribution of Georgia's nonprofit resources. Numerous tables and exhibits report on the distribution of public charities and foundations by geographic area, and compare this to the distribution of population and income in the state. Public support and government grants to charities are analyzed by geographic region, as is the geographic distribution of grants by Georgia foundations. Analysis is based primarily on 990 and 990-PF forms filed by Georgia public charities and foundations in 2000 and 2005. This report is a part of ongoing research on public charities and foundations in the state of Georgia, made possible through a generous grant from the Wilbur and Hilda Glenn Family Foundation. Research Report Number 07-0

    Submerged Pressure Differential Wave Energy Converter

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    As supplies of fossil fuels are becoming depleted, it is necessary to look for alternative sources of energy. The ocean is a vast, largely untapped source of renewable energy. This project attempts to design a device which can cheaply and reliably convert the energy from ocean waves into usable electrical energy. Computer simulations and oceanographic knowledge are utilized to develop a working design for an entirely submerged wave energy conversion device

    What shapes the far-infrared spectral energy distributions of galaxies?

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    To explore the connection between the global physical properties of galaxies and their far-infrared (FIR) spectral energy distributions (SEDs), we study the variation in the FIR SEDs of a set of hydrodynamically simulated galaxies that are generated by performing dust radiative transfer in post-processing. Our sample includes both isolated and merging systems at various stages of the merging process and covers infrared (IR) luminosities and dust masses that are representative of both low- and high-redshift galaxies. We study the FIR SEDs using principle component analysis (PCA) and find that 97\% of the variance in the sample can be explained by two principle components (PCs). The first PC characterizes the wavelength of the peak of the FIR SED, and the second encodes the breadth of the SED. We find that the coefficients of both PCs can be predicted well using a double power law in terms of the IR luminosity and dust mass, which suggests that these two physical properties are the primary determinants of galaxies' FIR SED shapes. Incorporating galaxy sizes does not significantly improve our ability to predict the FIR SEDs. Our results suggest that the observed redshift evolution in the effective dust temperature at fixed IR luminosity is not driven by geometry: the SEDs of z23z \sim 2-3 ultraluminous IR galaxies (ULIRGs) are cooler than those of local ULIRGs not because the high-redshift galaxies are more extended but rather because they have higher dust masses at fixed IR luminosity. Finally, based on our simulations, we introduce a two-parameter set of SED templates that depend on both IR luminosity and dust mass.Comment: Submitted to ApJ, comments welcom

    Burner rig optimization for high temperature materials and coating systems

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    Please click Additional Files below to see the full abstract. Please click Download on the upper right corner to see the presentation

    Why buy local?

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    This article critically assesses the moral arguments that speak in favour of three consumer options: buying local food, buying global (non-local) food, and buying global food while also purchasing carbon offsets to mitigate the environmental impact of food transportation. We argue that because the offsetting option allows one to provide economic benefits to the poorest food workers while also mitigating the environmental impact of food transportation it is morally superior to the alternatives

    A Primer on ABLE Accounts

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    The structure of triphenylgermanium hydroxide

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    C18H~6GeO, Mr = 320.9, triclinic, Pi, a = 15.408 (6), b = 19.974 (7), c = 23.264 (11) A, a = 107.78 (4), 13 = 1.03.54 (4), y= 101.51 (3) °, V = 6338 (5)/~3, Z = 16, Dx = 1.34 g cm -3, a(Mo Ka) = 0.71073A, /z = 19.1cm-1, F(000)=2624, T= 293 K, R = 0.055 for 6846 observed reflections. The eight independent molecules in the asymmetric unit form two independent O--H...O hydrogen-bonded tetramers with the O atoms in a flattened tetrahedral arrangement [hydrogen-bond distances in the range 2.609 (11) to 2.657 (11)A]. The Ge atoms are tetrahedrally coordinated with mean Gc O 1.791 (7) and Gc C 1.931 (8) A
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