Tuesday, all saints day here (holiday). I still want to get more work done. KiDS politics on the reduction pipeline could get a bit messy---Thomas doesn't want to "compete" with Astrowise, because he knows it's already better. I have a lot of projects in hand, but I want to be involved with the WL systematic testing with Rachel, on the GREAT08/10 continuation.
1110.6436
The prediction method of similar cycles
Du, Wang
Propose concept of "degree of similarity" (eta) to describe parameters (e.g., maximum amplitude Rmax) of a solar cycle relative to a referenced one, and the prediction method of similar cycles further developed. Two parameters (solar minimum Rmin and rising rate beta-a), a synthesis degree of similarity (eta-s) is defined as the weighted-average of the eta values around Rmin and beta-a with the weights given by the coefficients of determination of Rmax with Rmin and beta-a, respectively. The monthly values of the whole referenced cycle can be predicted by averaging the corresponding values in the most similar cycles with the weights given by the eta-s values. Cycles 14 and 10 are found to be the two most similar cycles of Cycle 24. As an application, Cycle 24 is predicted to peak around Jan 2013 with a size of about Rmax=83 and end around 2019.
* What is the science in defining "similar cycles"?
1110.6538
Environment dependence of DM haloes in symmetron modified gravity
Winther, Mota, Li
Symmetron is one of three known mechanisms for screening a fifth-force, and thereby recovering GR in dense environments. Effectiveness of screening depends on both the mass of the object and the environment it lies in. Using high-resolution N-body simulations find a significant difference, which depends on the halos mass and environment, between lensing and dynamical masses of DM halos similar to f(R) modified gravity. Symmetron can yield stronger signatures due to a freedom in the strength of the coupling to matter.
1110.6439
Collisions of inhomogeneous pre-planetesimals
Gereshauser, Speith, Kley
Carry out collisions of centimeter-sized dust aggregates of intermediate porosity, vary inhomogeneous distribution at fixed typical clump size; collision outcome categorized according to the four-population model [?]. Show inhomogeneous pre-planetesimals are more prone to destruction than homogeneous aggregates. Even slight inhomogeneities can lower the threshold for catastrophic disruption. For a fixed collision velocity, sizes of fragments decrease with increasing inhomogeneity. Pre-planetesimals with an active collisional history tend to be weaker. Possible obstacle to collisional growth, and needs to be taken into account in future studies of the coagulation scenario.
* maybe the temperature of the coagulates matters?
1110.6440
Extended excursion set approach to structure formation in Chameleon Models
Li, Efstathiou
* yuck.
Extend excursion set theory to incorporate environmental effects on structure formation; apply method to a chameleon model and calculate observables at various redshifts. The method can be generalized to study other observables and other models of environmentall dependent interactions [what does this mean?]. Analytic methods described here can be useful in delineating which models deserve more detailed study with N-body simulations.
1110.6441
The rest frame UV to optical colors and SEDs of z~4-7 galaxies
Gonzalez, Bouwens, Labbe, Illingworth, Oesch, Franx, Magee
Derive SEDs of star-forming galaxies from the rest-frame UV to the optical over a wide luminosity range (M_1500~-21 to -18) from z~7 to 4. Sample contains: ~400 z~4 galaxies to 36 z~7 galaxies. Medan stacking enables the first comprehensive study of very faint high-z galaxies at multiple redshifts. At z~4 the faint median-stacked SEDs reach to ~0.06 L* (z=4) and are combined with recently published results at high luminosity L>L* that extend to M_1500 ~ 23. Use the observed SEDs and template fits to derive rest frame UV-to-optical colors (U-V) at all redshifts and luminosities. Find: this color does not vary significantly with redshift at a fixed luminosity [well if you pick star-forming galaxies and no red ones, then yea]. The color does show a weak trend with luminosity, becoming redder at higher luminosities, most likely to dust. At z>~5 find blue colors [3.6]-[4.5] ~ -0.3 mag that are most likely due to rest-frame optical emission lines contributing to the flux in the IRAC filter bandpasses. The scatter across derived SEDs remains substantial, but results are most consistent with a lack of any evolution in the SEDs with redshift at a given luminosity. Similarity of the SEDs suggests a self-similar model of evolution over a timespan from 0.7 Gyr to 1.5 Gyr that encompasses very substantial growth in the stellar mass density in the universe (from 4e6 to 2e7 Msun/Mpc^3).
1110.6442
The HST cluster supernova survey: VI. the volumetric Type Ia SNe rate
Barbary et al, for the Supernova Cosmology Project
Present measurement of SN Ia rate out to z~1.6 from the HST CSS survey. Observations span 189 orbits with ACS; discovered 29 SNe, of which ~20 are SNe Ia. 12 are located in the foregrounds and backgrounds of the clusters targeted in the survey. Using these new data, derive the volumetric SN Ia rate in four broad redshift bins, finding results consistent with previous measurements at z>1 and strengthening the case for a SN Ia rate that is equal to or greater than ~0.6e-4/yr/Mpc^3 at z~1, and flattening out at higher redshift. Provide SN candidates and efficiency calculations in a form that makes it easy to rebin and combine these results with other measurements for increased statistics. Compare the assumptions about host-galaxy dust extinction used in different high-z rate rate measurements, find different assumptions induce significant systematic differences between measurements.
1110.6445
A practical guide to the massive black hole cosmic history
Sesana
Review current understanding of massive black hole formation and evolution. Overview relevance of MBHs in the hierarchical structure formation paradigm; discuss the main viable channels for seed BH formation at high z and for their subsequent mass growth and spin evolution. The picture, where MBHs grow through merger triggered accretion episodes, acquiring mass while shining as quasars, is overall robust, but too simplistic to explain the diversity in MBH phenomenology. Briefly discuss which future observations will help to shed light on the MBH cosmic history in the near future, paying particular attention to the upcoming gravitational wave window.
1110.6446
Star formation and environment in clusters up to z~2.2
Raichoor, Andreon
* Butcher-Oemler effect: a scientific hypothesis suggesting that the cores of galaxy clusters at intermediate redshift (z~0.3) contain a larger fraction of blue galaxies than do the cores of low redshift clusters (Butcher and Oemler 1978). Studies show BO effect widespread in rich clusters at z>0.2, and is due to vigorous episodes of star formation in a subset of cluster members. Appears to be confined to rich clusters, similar to Virgo. (>95% of blue field galaxies brighter than bJ=22.5 are at redshifts less than z=0.5, verifying models predicting no luminosity evolution of the field galaxy population since z=1.
Study star formation in clusters in a zphot~2.2 cluster. use deep ugrizJHK to estimate photoz's. Find no evindence of BO effect between z~2.2 and z~0 for galaxies more massive than 1.34e11 Msun. [how can you do that with one cluster?] Results show that present-day star formation-density relation is already in place at z~2.2.
1110.6479
Heavy sterile neutrinos, entropy and relativistic energy production, and the relic neutrino background
Fuller, Kishimoto, Kusenko
Explore implications of the existence of heavy neutral fermions (i.e., sterile neutrinos) for the thermal history of the early universe. Consider sterile neutrinos with rest masses in the 100-500MeV range, with couplings to ordinary active neutrinos large enough to guarantee thermal and chemical equilibrium at epochs in the early universe with temperatures T>1 GeV, but in a range to give decay lifetimes from seconds to minute. Such neutrinos would decouple early, with relic densities comparable to those of photons, but decay out of equilibrium, with consequent prodigious entropy generation prior to, or during, BBN. Most of the ranges of sterile neutrino rest mass and lifetime considered are at odds with CMB limits on the relativistic particle contribution to energy density; but some sterile neutrino parameters can lead to an acceptable N_eff. These parameter ranges are accompanied by considerable dilution of the ordinary background relic neutrinos, possibly an adverse effect on BBN, but sometimes fall in a range which can explain measured neutrino masses in some particle physics models. A robust signature of these sterile neutrinos would be a measured N_eff not equal to 3 coupled with no cosmological signal for neutrino rest mass when the detection thresholds for these probes are below lab-established neutrino mass values.
* I didn't quite get all the signatures of the sterile neutrinos. It seems like they exist under several strict conditions in order to match observations.
1110.6484
Evidence for shocks as the origin of gamma-ray flares in blazars
Aller, Hughes, Aller, Marscher, Jorstad, Hovatta, Aller
Finding supports the idea that oblique shocks in the jet are a viable explanation for activity from the radio to the gamma-ray band in at least some gamma-ray flares.
1110.6491
A conservation-based method for simulating the inspiral of binary black holes
Meiron, Laor
New approach: impose conservation of total energy and angular momentum in scattering experiments, find dissipation forces that are exerted on the BH by the stars, and thus obtain decaying path of the binary from the classical dynamical friction regime down to subparsec scales. Studied both equal mass and 10:1 mass ratio binaries under various initial conditions, show that while an equal mass binary stalls at a nearly circular orbit, a runaway growth of eccentricity occurs in the unequal mass case. This effect reduces the timescale for BH coalescence through gravitational radiation to well below the Hubble time, even in spherical and gasless systems formed by dry mergers.
1110.6536
The effect of different observational data on the constraints of cosmological parameters
Gong, Gao, Zhu
BAO and WMAP7 alone does not constrain w well, but together with SN Ia help break denegeracies among the model parameters, and constrain w_a.
1110.6857
The fundamental surface of quad lenses
Woldesenbet, Williams
In quadruply imaged lens system, the angular distribution of images around the lens center is completely described by three relative angles. Show empirically that in the 3d space of these angels, spanning 180x180x90 degrees, quads from simple 2-fold symmetric lenses of arbitrary radial density profile and arbitrary radially dependent ellipticity or external shear define a realy invariant 3d surface. Give fitting formula for the surface using SIS+elliptical lensing potential. Various circularly symmetric mass distributions with shear up to 0.4 deviate from it by typically rms~0.1 deg, while elliptical mass distributions with ellipticity of up to 0.4 deviate by rms 1.5 deg. The existence of a near invariant surface [is this relevant? is there going to be lens with two-fold symmetry?] gives a new insight into the lensing theory and provides a framework for studying quads without any recourse to mass modeling. As an illustration, show that about 3/4 of the observed galaxy-lens quads do not belong to this surface within observational error, and so require additional external shear or substructure to be modeled adequately.
* so it can tell if the lens for quad images has 2-fold symmetry.
1110.6872
Sgr A* flares: tidal disruption of astroids and planets?
Likely, if the central parsec of the MW has asteroid population per parent star not too dissimilar from that around stars in the Solar neighborhood. (Sgr A* produces tiny flares that last only hours but occur daily.)
1110.6889
A new model for the Fermi-LAT Extragalactic gamma-ray background
Cavadini, Salvaterra, Haardt
Blasars account for 45% of the total Fermi-LAT EGB. At low <10GeV and high >50GeV, the blazar contribution falls short to account for the observed BG light. At E<10GeV, the extragalactic gamma-ray background can be fully explained by considering the additional contribution of star-forming galaxies, where at very high energies, where the absorption due to extragalactic background light dominates, the observed background calls for an additional unknown component.
1110.6735
Effect of the cosmological constant on the bending of light and the cosmological lens equation
Arakida, Kasai
First re-examine the motion of photon in the Schwartschild spacetime, and explicitly describe the trajectory of photon and deflection angle alpha up to the second order in G. Then extend to the contribution of the cosmological constant Lambda in the Schwarzschild-deSitter or Kottler spacetime. Contrary to previous arguments, (a) the cosmological constant does appear in the orbital equation of light, (b) bending angle of light alpha does not change its form even if Lambda != 0 since the contribution of Lambda is thoroughly absorbed into the definition of the impact parameter, and (c) the effect of Lambda is completely involved in the angular diameter distance D_A.
* want to read this and try to figure it out. 3 pages, no figure.
1110.6174
The nature of assembly bias - II. Observational properties
Lacerna, Padilla, Stasyszyn
Assembly-type bias: where old galaxies have a higher clustering amplitude at scales r>1Mpc than young galaxies of equal magnitude. Definition of age: luminosity-weighted stellar age, increases the difference from 25% to a factor of 2 at r~2.5 Mpc. In contrast, when using the definition based on the Dn4000 index, the clustering amplitude at large scales show a weaker signal-to-noise for the assembly bias detection. In semi-analytic galaxies, the difference in clustering using the stellar age is similar at distances beyond 3Mpc, but overpredict the assembly bias found in SDSS at smaller scales. .... measure crowding around objects that traces the assembly bias effect from neighbour galaxies in cylinders in contrast to a smooth density field.
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