1309.2940
Two high-redshift DLAs towards a z~5 gamma-ray burst
Sparre et al
As the title says: GRB host at z=5.0, DLA at z=4.6. This is the highest z where Fe II fine-structure lines have been detected.
1309.2942
Galaxy mergers on a moving mesh: a comparison with smoothed-particle hydrodynamics
Hayward, Torrey, Springel, Hernquist, Vogelsberger
Explore issue of SPH (smoothed particle hydrodynamics) inaccuracies in studying galaxy mergers: compare Gadget-3 SPH of idealized (i.e., non-cosmological) isolated discs and galaxy mergers with otherwise identical calculations performed using the moving-mesh code Arepo. When BH accretion and AGN feedback are not included, the SFHs obtained from the two codes agree well. When BHs are included, the code- and resolution-dependent variations in the SFHs are more significant, but the agreement is still good, and the stellar mass formed over the course of a simulation is robust to variations in the numerical method. During a merger, the gas morphology and phase structure are initially similar prior to the starburst phase. However, once a hot gaseous halo has formed from shock heating and AGN feedback (when included) occurs, the agreement is less good. In particular, during the post-starburst phase, the SPH simulations feature more prominent hot gaseous haloes and spurious clumps, whereas with Arepo, gas clumps and filaments are less apparent and the hot halo gas can cool more efficiently. Discuss the origin of these differences and explain why the SPH technique yields trustworthy results for some applications (such as the idealized isolated disc and galaxy merger simulations presented) but not others (e.g., gas flows onto galaxies in cosmo-hydro sims).
(*) 1309.2943
Cosmological dependence of the measurements of luminosity function, projected clustering and galaxy-galaxy lensing signal
More
Assumption of cosmology to calculate distances in: luminosity functions, projected galaxy clustering, and gg lensing. Growing number of surveys that perform joint analyses of these measurements and constrain cosmological parameters. Quantify the amount by which such measurements systematically vary as the fiducial cosmology used for the measurements is changed, and show that these effects can be significant at high redshifts (z~0.5). Present a simple way that maps the measurements made using a particular fiducial cosmological model to any other cosmological model. Cosmological constraints (or halo occupation distribution constraints) that use the luminosity function, clustering measurements and gg lensing signal but ignore these systematic effects may underestimate the confidence intervals on the inferred parameters.
1309.2944
The Nucleus of Coment 10P/Tempel 2 in 2013 and consequences regarding its rotational state: early science from the Discovery Channel Telescope
Schleicher, Knight, Levine
Lightcurve measurements in early 2013 when comet was at aphelion. These data represent some of the first science obtained with this new 4.3m facility. Tempel 2 is observed to exhibit a small but ongoing spin-down in its rotation for over 2 decades; primary goals are (1) determine its current rotation period and compare it to that measured shortly after it most recent perihelion passage in 2010, and (2) to disentangle the spin-down from synodic effects due to the solar day and the Earth's orbital motion and to determine the sense of rotation, i.e., prograde or retrograde. At the midpoint of 2013 Feb 24, the observed synodic period is 8.948pm0.001 hr, exactly matching the predicted prograde rotation solution based on 2010 results, and yields a sidereal period of the identical value due to the solar and Earth synodic components just canceling out during the interval of the 2013 observations. The retrograde solution is ruled out because the associated sidereal periods in 2010 and 2013 are quite different even though it is known that extremely little outgassing, needed to produce torques, occurred in this interval. With a definitive sense of rotation, the specific amounts of spin-down to the sidereal period could be assessed. The nominal values imply that the rate of spin-down has decreased over time, consistent with the secular drop in water production since 1988. Our data also exhibited an unexpectedly small lightcurve amplitude which appears to be associated with viewing from a large, negative sub-Earth latitude, and a lightcurve shape deviating from a simple sinusoid implying a highly irregularly shaped nucleus.
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