Day 544

Tuesday.

1311.0866
Cosmology with massive neutrinos I: towards a realistic modeling of the relation between matter, haloes and galaxies
Villaescusa-Navarro, … Sefusatti, Saito et al

Use N-body sims that incorporated massive neutrinos as extra set of particles, investigate the impact of neutrino masses on the spatial distribution of DM haloes and galaxies.  Compute galaxy bias using PS and 2-pt correlation function.  Find scale-dependent bias for cosmologies with massive neutrinos, but results indicate that scale-dependence in the bias is reduced if the latter is computed with respect to the CDM distribution only [in contrast to what?  with neutrinos?  there aren't that many neutrinos].  Value of bias on large scales is reasonably well reproduced by Tinker flitting formula once the linear CDM PS is used, instead of total matter PS [does 'total' mean "with neutrinos"?].  Investigate whether scale-dependent bias really comes from neutrino's effect, or from NL gravitational collapse of haloes.  Omega_nu-sigma_8 degeneracy is not perfect, implying a slight scale dependence on the large-scale bias.  Using a simple HOD model, investigate the impact of massive neutrinos on the distribution of galaxies within DM haloes.  Use SDSS DR7 to investigate if the small-scale galaxy clustering alone can be used to discriminate among different cosmological models with different neutrino masses.  Results suggest that different choices of the HOD parameters can reproduce the observational measurements relatively well, and quantify the difference between the values of the HOD parameters between massless and massive neutrino cosmologies.

1311.0905
Cosmology from cross correlation of CMB lensing and galaxy surveys
Pearson, Zahn

CMB lensing-LSS X-correlation may provide new insights into parameters describing cosmological structure growth.  Perform forecasts that combine the lensing potential auto PS from various future CMB experiments, the galaxy PS from galaxy surveys, as wells the X-PS between the two, marginalizing over a number galactic and non-galactic cosmological parameters.  Find that the CMB lensing-LSS cross correlation contains significant information on parameters such as the z distribution and bias of LSS tracers.  Also find that the X-corr information will lead to independent probes of cosmological parameters such as neutrino mass and the reionization optical depth.

1311.1104
The largest structure of the Universe, defined by Gamma-ray bursts
Horvath, Hakkila, Bagoly

GRBs are very good indicators of the dense part of the universe; 283 GRB redshifts available as of July 2012.  See a large cluster of GRBs, larger in scale than the Sloan Great Wall.

1311.1201
Detectability of free floating planets in open clusters with JWST
Pacucci et al

Stellar clusters: high star density, high geavy-element content = may induce strong perturbations of planetary orbits with large semi major axis = free-floating planets in stellar clusters.  Free-floating production rate (total number of free-floating planets per unit time, normalized by the total number of stars) is proportional to the stellar density of the cluster, proportionality constant = (23pm5)e-6 pc^3/Myr, from simulation.  Assuming surface temperature of 500K [which is >100C, not likely for a free-floating planet, but more likely for a planet orbiting a nearby star], a free-floating planet with the JWST in the NIR band have ~400 nJy, which has S/N>100, detectable with JWST with 1 hr of integration.

1311.1205
Mass and concentration estimates from weak and strong gravitational lensing: a systematic study
Giocoli, Meneghetti, Metcalf, Ettori, … et al

Study how well halo properties of galaxy clusters (mass and concentration) are recovered using lensing data.  Measure (1) WL only, best with with NFW profile, or (2) combine with SL, using info from Einstein ring.  Find: bias mainly caused by random orientation of the halo ellipsoid with respect to the line-of-sight.  Simulations account for the presence of a bright central galaxy; fit to NFW with free inner slope: this reduces both the mass and concentration biases, but introduces an additional free parameter [probably noisier too].  Discuss how the mass function and the concentration mass relation change when using WL and WL+SL estimate [is one better than the other, or not?].  Investigate how selection effects imp at the measured concentration-mass relation showing that SL clusters may have a concentration 20-30% higher than the average [selection effect….], at fixed mass, considering also the particular case of SL selected samples of relaxed clusters.

1311.1211
Galaxy and mass assembly (GAMA): the large scale structure of galaxies and comparison to mock universes
Alpaslan, et al

Volume-limited sample of 45k galaxies and 6k groups with z<=0.213, use an adapted minimal spanning tree algorithm to identify and classify LSS within the GAMA survey.  Using galaxy groups, identify 643 filaments across the 3 equatorial GAMA fields that span up to 200 Mpc/h in length, each with an average of 8 groups within them.  Analysing galaxies not belonging to groups, identify a secondary population of smaller coherent structures composed entirely of galaxies ("tendrils") that appear to link filaments together, or penetrate into voids, generally measuring around 10 Mpc/h in length and contatinin on average 6 galaxies.  Identify population of isolated void galaxies.  By running this algorithm on GAMA mock galaxy catalogues, compare the characteristics of LSS between observe and mock data; find that mock filaments reproduce observed ones extremely well.  This provides a probe of higher order distribution statistics not captured by the popularly used 2pt correlation function.

1311.1215
Counterrotating stars in simulated galaxy disks
Algorry, Navarro, … et al

Mergers do not play a substantial role, and most stars in the galaxy are formed in situ, only 9% of all stars are contributed by accretion events.  The formation scenario described here implies a significant age difference between the co-and counterrotating components, which may be used to discriminate between competing scenarios for the origin of counterrotating stars in disk galaxies.

1311.1319
Weak lensing mass map and peak statistics in CFHT/Stripe82 survey
Shan, Kneib, .. Jullo, Erben, Van Waerbeke, Courbin, … et al

WL mass map of CHFT stripe 82 survey with ~124 sq deg and study the peak statistics, including peak abundance, correlation functions and tangential-shear profile of peaks with the mass map.  Find that (1) peak abundance detected in CS82 are consistent with predictions from a LCDM cosmology model (2) correlation function of peaks with different S/N can be well fitted with power laws.  Combine with CMASS galaxies, the X-corr between CMASS galaxies and high SNR peaks can be well-fitted with a power law; (3) the tangential shear profiles of the peaks increase with S/N.  Concentrate on fitting spherical models to the tangential profiles with both singular isothermal sphere and NFW models.  For the high S/N peaks, the SIS models is rejected at 3 sigma.  Comparing the dark and matched clumps to the optically selected redMaPPer clusters, a difference in lensing signal of a factor of 2 can be found, reflecting the fact that likely about half of the dark clumps are false detection.

1311.1480
The weak lensing signal and clustering of SDSS-III CMASS galaxies I. probing matter content
Miyatake, More, Mandelbaum, Takada, Spergel, Kneib, Schneider, Brinkmann, Brownstein

CMASS galaxies (0.47<z<0.59) gg lensing signal of S/N=28; combine with projected auto-correlation function for similar subset, fit a halo model to the measurements assuming a LCDM cosmological model.  The halo model can reasonably well fit the two independent measurements simultaneously, with chi^2=39.55 for 39 degrees of freedom.  (1) the average mass for CMASS host halos is 2.3 e13 Msun/h, smaller than that of SDSS luminous red galaxies at z~0.3, (2) the smallest-scale lensing signal at R~100 kpc/h places an upper limit on stellar mass contribution from the CMASS galaxy thus disfavoring some of the previous stellar mass estimates based on the photometry and spectra, and (3) the halo concentration at the CMASS halo mass scale is about 20% lower than that predicted from collision less numerical simulations.  Also show that including an off-centering effect of halo model 'central' galaxies could relax the possible tension in the stellar mass and the halo concentration.

1311.1489
Cosmic shear without shape noise
Huff, Krause, Eifler, George, Schlegel

Use spectra of disk galaxy rotation and TF relation in order to control for the intrinsic orientations of galaxy disks [hence no shape noise.  very labor intensive].  The shape noise ceases to be an important source of statistical error.  Simulate likelihood analysis for two spectroscopic WL survey concepts and compare their constraining power to a cosmic shear survey from LSST.  7 parameter cosmology includes statistical uncertainties from shape noise, cosmic variance, halo sample variance, and higher-order moments of the density field.  Marginalize over systematic uncertainties arising from photo-z errors and shear calibration biases considering both optimistic and conservative assumptions about LSST systematic errors.  Find that even the TF-Stage III is highly competitive with the optimistic LSST scenario, while evading the most important sources of theoretical and observational systematic error inherent in traditional WL techniques.  The TF technique enables a narrow-bin cosmic shear tomography approach to tightly constrain time-dependent signatures in the DE phenomenon.