1204.4745
Dust-to-gas ratio in the extremely metal poor galaxy I ZW 18
Herrera-Camus, et al
Blue compact galaxy, one of the most metal-poor systems known in the local universe (12+log(O/H)=7.17). Use dust emission models to derive M_dust <= 1.1e4 Msun 3 sig upper limit. Total dust-to-gas ratio upper limit of 5e-5.
1204.4749
A per-baseline, delay-spectrum technique for accessing the 21cm cosmic reionization signature
Parsons, Pober, Aguirre, Carilli, Jacobs, Moore
Challenge in measuring 21cm emission from cosmic reionization: compensating for the frequency dependence of an interferometer's sampling pattern (causes smooth-spectrum FG to appear unsmooth and degrade the separation between foregrounds and the target signal). Present an approach to foreground removal that explicitly accounts for this frequency dependence. Apply delay transformation to each baseline of an interferometer to concentrate smooth-spectrum FG within the bounds of the maximum geometric delays possible. By focusing on delay-modes that correspond to image-domain regions beyond the horizon, possible to avoid the bulk of smooth-spectrum FGs. Show delay-modes that are uncorrupted by foregrounds also represent samples of the 3d power spectrum; can be used to constrain cosmic reionization. Uses spectral smoothness to differentiate FG from the targeted 21cm signature, this per-baseline analysis relies on spectrally-and spatially-smooth instrumental responses for FG removal. For sufficient levels of instrumental smoothness relative to the brightness of interfering FGs, this technique substantially reduces the level of calibration previously thought necessary to detected 21cm reionization. Result: this places fewer constraints on antenna configuration within an array--in particular, facilitates the adoption of configurations that are optimized for power-spectrum sensitivity. Potential for the PAPER array to detect 21cm reionization at an amplitude of 10 mK^2 near k~0.2 h/Mpc with 128 dipoles in 7 months of observing.
1204.4789
A New type of ambiguity in the planet and binary interpretations of central perturbations of high-magnification gravitational microlensing events
Choi, et al
High-magnification microlensing events detecting planets; present a case of central perturbation (usually distinguishable whether it is from the planet or a binary companion due to different magnification around the caustics) for which it is difficult to distinguish the planetary and binary interpretations. The peak of a lensing light curve affected by this perturbation appears to be blunt and flat. Different caustics by planet or binary companion can show similar magnification curve. (Planet: negative perturbation region behind the back end of an arrowhead-shaped central caustic; binary: a similar perturbation for a source trajectory passing through the negative perturbation region between two cusps of an astroid-shaped [?] caustic. Demonstrate degeneracy; expect this to be common.
1204.4834
Non-therrmal processes in bowshocks of runaway stars. Application to Zeta Oph
del Valle, Romero
Runaway massive stars are O- and B-type stars with high spatial velocities with respect to the interstellar medium; can produce bowshocks in the surrounding gas. Star moves supersonically through the interstellar gas. The shocked matter emits thermal radiation and a population of locally accelerated relativistic particles is expected to produce non-thermal emission over a wide range of energies. Model the non-thermal emission by relativistic particles, and thermal radiation caused by free-free interactions. Apply model to Zeta Oph. Spectral energy distributions of massive runaways are predicted for the whole EM spectrum. Non-thermal radiation might be detectable at various energy bands for relatively nearby runaway stars, especially at HE gamma rays. Inverse compton scattering with photons from the heated dust gives the most important contribution to the high-energy spectrum. This emission approaches Fermi sensitivities in the case of Zeta Oph.
1204.4846
Duty cycle and the increasing Star Formation history of z \geq 6 galaxies
Jaacks, Nagamine, Choi
Examine the history of SFH for z>=6 using cosmological hydro simulations. The averaged SFH between 6<z<15 can be characterized well by an exponentially increasing functional form (time scale 70 to 200 Myr) for stellar masses 1e6 to 1e10 Msun, or a simple power-law which exhibits a similar mass dependent time-scales. Take SFH or individual galaxies and find the duty cycle (DC_SFH), the fraction of SF time that is above HST detection. Similarly, define DC_Muv, where rest-fram UV is sufficient for HST observation. Both DC has a sharp transition from 0 to 1 between 1e6 to 1e9 Msun stellar mass. Duty cycle also manifested in the intrinsic scatter in the Ms-SFR relation and Ms-Muv relation. Fitting functions for DC for SAM usage. Simulation more compatible with observational estimates.
1204.4871
Probing the innermost dusty structure in AGN with mid-IR and near-IR interferometers
Kishimoto, Hoenig, Antonucci, Barvainis, Kotani, Millour, Tristram, Weigelt
Focus on type 1 AGN where innermost region is unobscured. Trace the structure by observing dust grains radiatively heated by the central engine. Dust sublimation radius = R_in, found to be scaling with L^1/2, as expected. In the MIR, the overall size in units of R_in seems to become more compact in higher luminosity sources; a power law, where the slope is steeper in higher luminosity objects. NIR flux not a simple inward extrapolation of the MIR power law component, but rather comes from a little distinct brightness concentration at the inner rim region of the dust distribution; structure not well constrained, but possibly has a steeper radial distribution in jet-launching objects.
1204.4917
The interaction of dark matter cusp with the baryon component in disk galaxies
Khoperskov, Shustov, Khoperskov
Examine the effect of the formation and evolution of disk galaxy on the distribution of dark halo matter. Simulate DM and DM+baryon; use N-body for stellar and DM; TVD MUSCL for gas-dynamic simulations. Includes: SF, stellar feedback, heating and cooling of the ISM; high spatial resolution. Find: (1) SF and SNe feedback resolved the problem of cusp distribution of DM. (2) interaction of DM with dynamic substructures of stellar and gaseous galactic disk (spiral waves, bar) has an impact on the shape of the DM halo: the in-plane distribution of DM is more symmetric in runs where the baryonic component is taken into account.
1204.4919
GRB progenitors and observational criteria
Zhang
Long GRBs typically belong to Type II (massive star progenitor), while short-duration to Type I (compact star progenitors); but counterexamples do exist. Need multiple observational criteria to classify GRBs. Use "amplitude", in addition to "duration" and "hardness" to quantify burst progenitors.
1204.4934
Diffuse Lyman alpha haloes around Lyman alpha emitters at z=3: do dark matter distributions determine the Lyman alpha spatial extents?
Matsuda, et al
Stack 2128 LAEs at z=3.1, examine the surface brightness profiles of Lya haloes around high-z galaxies as a function of environment. Slope of Lya radial profile flatter as the Mpc-scale LAE surface densities increase; almost independent of the central UV luminosities. Lya photons formed via shock compression by gas outflows or cooling radiation by gravitational gas inflows may partly contribute to illuminate the Lya haloes, but most can be explained by photo-inoization by ionizing photos or scattering of Lya photons produced in HII regions in and around the central galaxies. Regardless of the source of Lya photons, if Lya haloes trace the overall gaseous structure following the DM distributions, it is not surprising that the Lya spatial extents depend more strongly on the surrounding Mpc-scale environment than on the activities of the central galaxies.
(*) 1204.4981
Probing primordial non-Gaussianity with weak lensing minkowski functionals
Shirasaki, Yoshida, Hamana, Nishimichi
Study the cosmological information contained in the Minkowski Functions (MFs) of WL kappa maps. Show that the MFs provide strong constraints on f_NL. Run a set of cosmological N-body simulations and perform ray-tracing simulations of WL, generate 100 independent convergence maps of 25 degsq FoV for f_NL=-100, 0 and 100. Fisher analysis for sigma8 and w. WL MFs can constrain f_NL~80 and w~0.036. A 20000 sqdeg survey using LSST will constrain f_NL~25 and w~0.013. Show further improvement with tomographic method.
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