Day 602

Friday.  Saturday.  Sunday.

1403.0743
Constraints on the star-formation rate of z~3 LBGs with measured metallicity in the CANDELS GOODS-South field
Castellano et al

Analyse 14 LBGs at z~2.8-3.8 where both a spectroscopic measurement of their metallicity and deep IR observations are available.  Fixing the metallicity of population synthesis models to the observed values, determine best-fit physical parameters under different assumptions on the SFH and considering also the effect of nebular emission.  For comparison, determine the UV slope of the objects, and use it to estimate their SFR_UV99.  A comparison between SFR obtained through SED-fitting (SFR_fit) and the SFR_UV99 shows that the latter are underestimated by a factor 2-10, regardless of the assumed SFH.  Other SFR indicators (radio, FIR, X-ray, recombination lines) coherently indicate SFRs a factor 2-4 larger than SFR_UV99 and in closer agreement with SFR_fit.  Such discrepancy is due to the solar metallicity implied by the usual beta-A1600 conversion factor.  Propose a refined relation, appropriate for sub-solar metallicity LBGs: A1600 = 5.32+1.99 beta.  This relation reconciles the dust-corrected UV with the SED-fitting and theo there SFR indicators.  Show that the fact that z~3 galaxies have sub-solar metallicity implies an upward revision by a factor of ~1.5-2 of the global SFRD, depending on the assumptions on the age of the stellar populations.  Find very young best-fit ages (10-500 Myrs) for all objects.  From a careful examination of the uncertainties in the fit and the amplitude of the Balmer break, conclude that there is little evidence for the presence of old stellar population in at least half of the LBGs in the sample, suggesting that these objects are probably caught during a huge SF burst, rather than being the result of a smooth evolution.

1403.0758
The 2XMMi/SDSS galaxy cluster survey. III. clusters associated with spectroscopically targeted luminous red galaxies in SDSS-DR10
Takey, Schwope, Lamer

Present a sample of 383 X-ray selected galaxy groups and clusters with spectra up to z~0.79.  X-ray cluster candidates selected as serendipitously detected sources from the 2XMMi-DR3 catalog  overlapping with SDSS-DR7.  The cluster galaxies with available spectroscopic redshifts were selected from SDSS-DR10.  Developed an algorithm for identifying the cluster candidates associated with spectro-LRGs and constraining the the cluster spectroscopic redshift.  A cross-correlation of the constructed cluster sample with published optically selected cluster catalogues yielded 264 systems with available redshifts.  The present z measurements are consistent with the published values.  The current cluster sample extends the optically confirmed cluster sample from the cluster survey by 67 objects.  It provides spectroscopic confirmation for 78 clusters among published cluster sample, which previously had only photometric redshifts.  Of the new cluster sample that comprises 67 systems, 55 objects are newly X-ray discovered clusters and 52 systems are sources newly discovered as galaxy clusters in optical and X-ray.  Based on the measured z and the fluxes given in the 2XMMi-DR3 catalogue, estimate the X-ray luminosities and masses of the cluster sample.

1403.0852
Probing modified gravity theories with ISW and CMB lensing
Munshi, Hu, Ranzi, Heavens, Coles

The imprint of ISW and lensing of the CMB X-correlation has recently been detected in the bispectrum of temperature maps.  In this paper, use the optimized skew-spectrum as well as skew-spectra associated with Minkowski Functionals (MFs) to test the possibility of using this signal to detect deviations in the theory of gravity away from GR.  Find that although both statistics can put constrains on modified gravity, the optimized skew-spectra are especially sensitive to the parameter B_0 that denotes the Compton wavelength of the scalar on at the present epoch, and both can be used to put stringent constraints on any departure from GR, or pinpoint any systematics in the data.  Investigate 3 modified gravity theories, namely: the Post-parameterized Friredmanian formalism (PPF), the Hu-Sawicki (HS) mode, and the Bertschinger-Zukin (BZ) formalism.  Employing a likelihood analysis for an experimental setup similar to ESAs Planck mission, find that assuming GR to be the correct model, expect the constraints from the first two skew-spectra, S_el^(0) and S_el^(1), to be the same: B_0<0.45 at 95% CL, and <0.67 at 99% CL in the BZ model.  The third skew-spectrm does not give any meaningful constraint.  The performance of MFs can be improved by using Wiender-type filtering, but find that the optimal skew-spectrum is much more powerful, giving B_0<0.071 at 95% CL and B_0<0.15 at 99% CL, which is a factor of 6 improvement compared to constraints derived from MF, and essentially identical to what can be achieved using the full bispectrum.

1403.0908
The premature formation of high redshift galaxies
Melia

Observations with WFC3/IR on the HST and the use of gravitational lensing techniques have facilitated discovery of galaxies as far back as z~10-12.  However, this rapid emergence of high-z galaxies, barely ~200 Myr after the transition from Pop III formation to Pop II, appears to be in conflict with the standard view of how the early Universe evolved.  This problem has much in common with the better known (and probably related) premature appearance of SMBHs at z~6.  It is difficult to understand how ~1e9 Msun BHs could have appeared so quickly after the BB without invoking non-standard accretion physics and the formation of massive seeds, neither of which is seen in the local Universe.  In earlier work, showed that the appearance of high-z quasars could instead be understood more reasonably in the context of the R_h=ct Universe, which does not suffer from the same time compression issues as LCDM does at early epochs, Build on that work by demonstrating the the evolutionary growth of primordial galaxies was consistent with the current view of how the first stars formed, but only with the timeline afforded by the R_h=ct cosmology.  Also show that the growth of high-z quasars was mutually consistent with that of the earliest galaxies, though it is not yet clear whether the former grew from 5-20 Msun seeds created in Pop II for Pop II SN explosions.

1402.7144
The source-lens clustering effect in the context of lensing tomography and its self-calibration
Yu et al

Sampling the cosmic shear field through observation is inevitably biased, since cosmic shear can only be measured where there are galaxies, and the galaxy distribution is correlated with the lensing signal.  This source-lens clustering (SLC) effect has two sources, intrinsic source clustering and cosmic magnification (magnification/size bias).  The former decreases with decreasing width of the source galaxy z distribution.  However, this reduction is limited.  Hence it remains unclear whether the residual can be controlled below the statistical error of stage IV lensing surveys.  Furthermore, SLC induced by cosmic magnification can not be reduced by lensing tomography.  Through N-body simulations, quantify the impact of SLC on lensing E/B-mode PS in the context of lensing tomography.  Consider two favorite estimators in measuring the lensing power spectrum, standard estimator and pixel-based estimator.  Find that neither of the two estimators can satisfactorily handle both sources of SLC.  For standard estimator, SLC induced by both the two sources can bias the lensing PS by O(1%)-O(10%) and the exact value depends on the galaxy bias and the flux/size of source galaxies.  SLC induced by intrinsic source clustering also increases statistical uncertainties in the measured lensing PS.  However, standard estimator suppresses intrinsic source clustering induced SLC in cross PS.  In contrast, pixel-based estimator is efficient to suppress LSC induced by cosmic magnification.  However, it fails to suppress LSC induced by intrinsic source clustering and the measured lensing power spectrum can be biased low by O(1%)-O(10%).  Conclude that SLC effect is a severe systematic error for WL cosmology, even with the aid of lensing tomography.  Present useful scaling relations to self-calibrate SLC effect.

1402.7321
Lensing models of MACS J1149.5+2223 I: cluster mass reconstruction
Rau, Vegetti, White

Measurements of the total logarithmic central slope of the mass profile in galaxy clusters constrain their evolution and assembly history and that of their BCGs.  Report the first full surface brightness distribution modeling of the inner region of the galaxy cluster MACS J1129.5+2223.  Compare these results with a position-based modeling approach for which more than twice the previously known positional constraints are applied.  First time that the detailed lensed image configuration of two non-central cluster galaxies with Einstein rings has been mapped.  Due to the extended radial coverage provided by the multiple images in this system, able to determine the slope d log kappa / d log R = -0.37 of the total projected mass distribution from 8 to 80 kpc.  This is within the cluster-to-cluster scatter estimates from previous cluster measurements.  Reconstruction of the image surface brightness distribution of the large central spiral galaxy has a root mean square residual for all image pixels of 1.14 sigma, where signal is the observational BG noise.  This corresponds to a reconstruction of the positions of bright clumps in the central galaxy with a rms of 0.063 arc seconds.
1402.7354
Salpeter normalization of the stellar initial mass function for massive galaxies at z~1
Shetty, Cappellari

The stellar IMF is a key parameter to study galaxy evolution.  Measure the IMF mass normalization for a sample of 68 field galaxies in 0.7<z<0.9 within EGS.   Derive total (stellar + DM) mass-to-light [(M/L)_dyn] using axisymmetric dynamical models.  Within the region where kinematics exists (about 1/2-light radius), the models assume: (i) that mass follows light, implying negligible difference between the stellar and total density profiles; (ii) constant velocity anisotropy (beta_z==1-sigma^2_z/sigma^2_R=0.2), (iii) that galaxies are seen at the average inclination for random orientations (i.e., i=60deg, where i=90 deg represents edge-on).  The dynamical models are based on anisotropic Jeans equations, constrained by HST/ACS imaging and the central velocity dispersion of the galaxies, extracted from good-quality spectra taken by DEEP2 survey.  The population (M/L)_pop are derived from full-sepctrum fitting of the same spectra with a grid of simple stellar population models.  Recent dynamical modeling results by the ATLAS 3D project and numerical simulations of galaxy evolution indicate that the DM fraction within the central regions of our galaxies should be small.  This suggest that the derived total (M/L)_dyn should closely approximate the stellar M/L.  Comparison of (M/L)_dyn and (M/L)_pop then imply that for galaxies with stellar mass >1e11 Msun, the average normalization of the IMF is consistent with a Salpeter slope, with a substantial scatter.  This is similar to what is found within a similar mass range for nearby galaxies.

1403.1257
The impact of mechanical AGN feedback on the formation of massive early-type galaxies
Choi, Ostriker, Naab, Oser, Moster

Employ cosmo hydro-sims to investigate the effects of AGN feedback on the formation of massive galaxies with present-day stellar masses of M*>8.9e10Msun.  Using SPH sims with a pressure-entropy formulation that allows an improved treatment of contact discontinuities and fluid mixing, run 3 sets of simulations of 20 halos with different AGN feedback models: (1) no feedback, (2) thermal feedback, and (3) mechanical and radiation feedback.  Assume that seed BHs are present at early cosmic epochs at the center of emerging DM haloes and trace their mass growth via gas accretion and mergers with other BHs.  Both feedback models successfully recover the observed M_BH-sigma relation and BH-to-M* ratio for simulated central early-type galaxies.  The baryonic conversion efficiencies are reduced by a a factor of two compared to models without any AGN feedback at all halo masses.  However, massive galaxies simulated with thermal AGN feedback show a factor of ~10-100 higher X-ray luminosities than observed.  The mechanical and radiation feedback model reproduces the observed correlation between X-ray luminosities and velocity dispersion, e.g., for galaxies with sigma=200 km/s, the X-ray luminosity is reduced from 1e42 erg/s to 1e40 erg/s.  It also efficiently suppresses late time SF, reducing the sSFR from 1e-10.5/yr to 1e-14 /yr on average and resulting in quiescent galaxies since z=2, whereas the thermal feedback model shows higher late time in-situ SFRs than observed.

1403.1259
Measuring the growth of matter fluctuations with third-order galaxy correlations
Hoffmann et al

Measurements of the linear growth factor D at different redshifts z are key to distinguish among different cosmo models.  One can estimate the derivative dD(z)/d ln(1+z) from z-space measurements of the 3D anisotropic galaxy 2-pt correlation xi(z), but the degeneracy of its transverse (or projected) component with galaxy bias, i.e., xi_perp(z) propto D^2(z) b^2(z), introduces large errors in the growth measurement.  In this paper, present a detailed comparison of two methods that have been proposed in the literature to break this degeneracy.  Both propose measuring b(z), and therefore D(z) via xi_perp, by combining 2nd- and 3rd-order statistics.  One uses the shape of the reduced 3pt correlation and the other a combination of 3rd-order 1- and 2-pt cumulants.   These methods take advantage of the fact that, for Gaussian ICs, the reduced 3rd-order matter correlations depend on b.  One can therefore measure b and D by comparing the 2nd and 3rd-order matter correlations to those of galaxies.  Use matter and halo catalogs from the NICE-GC simulations to test how well b(z) and D(z) can be recovered with these methods in 3d real space.  Also present a new approach, which enables measurement of D directly from the z evolution of 2nd and 3rd-order galaxy correlations without the need of modeling matter correlations.  For haloes with masses lower than 1e14 Msun/h, find a 1% agreement between the different estimates of D.  At higher masses, find larger differences that can probably be attributed to the breakdown of the local quadratic bias model and non-Poissonian shot-noise.

1403.1260
Cosmology: from theory to data, from data to theory
Leclercq, Pisani, Wandelt

Discuss the questions: "what is observable?", "what in the Universe is knowable?" and "what are the fundamental limits to cosmological knowledge?".  Then describe the methodology for investigation: theoretical hypothesis are used to model, predict and anticipate results; data is used to infer theory.  Illustrate with concrete examples of principled analysis approaches from the study of CMB anisotropies and surveys of LSS, culminating in a summary of the highest precision probe to date of the physical origin of cosmic structures: the Planck 2013 constraints on primordial non-Gaussianity.

1403.1261
Simulating cosmic metal enrichment by the first galaxies
Pallottini, Ferrara, et al

Study cosmic metal enrichment via AMR hydro sims in a (10 Mpc/h)^3 volume following the Pop III - Pop II transition and for different Pop III IMFs.  Analyze the joint evolution of metal enrichment on galactic and intergalactic scales at z=6 and z=4.  Galaxies account for <9% of the baryonic mass; the remaining gas resides in the diffuse phases: (a) voids, i.e. regions with extremely low density (Delta < 1), (b) the true IGM 1<Delta<10, and (c) the circumgalctic medium (CGM, 10<Delta<1e2.5), the interface between IGM and galaxies.  By z=6 a galactic mass-metallicity relation is established.  At z=4, galaxies with a stellar mass M*=1e8.5 Msun show log(O/H)+12=8.19, consistent with observations.  The total amount of heavy elements rises from Omega^SFH_Z=1.52e-6 at z=6 to 8.05e-6 at z=4.  Metals in galaxies make up t o~0.89 of such budget at z=6; this fraction increases to ~0.95 at z=4.  At z=6 (z=4) the remaining metals are distributed in CGM/IGM/voids with the following mass fractions: 0.06/0.04/0.01 (0.03/0.02/0.01).  Analogously to galaxies, at z=4 a density-metallicity (Delta-Z) relation is in place for the diffuse phases: the IGM/voids have a spatially uniform metallicity, Z~1e-3.5 Zsun; in the CGM Z steeply rises with density up to ~1e-2 Zsun.  In all diffuse phases a considerable fraction of metals is in a warm/hot (T>1e4.5K) state.  Due to these physical conditions, CIV absorption line experiments can probe only ~2% of the total carbon present in the IGM/CGM; however, metal absorption line spectra are very effective tools to study reionization.  Finally, the Pop III SFH is almost insensitive to the chosen Pop III IMF.  Pop III stars are preferentially formed in truly pristine (Z=0) gas pockets, well outside polluted regions created by previous SF episodes.

1403.1271
SCoPE: an efficient method of cosmological parameter estimation
Das, Souradeep

Present a fast and independently written MC method for cosmological parameter estimation "Slick Cosmological Parameter Estimator" (SCoPE), that employs delayed rejection to increase to acceptance rate of a chain, and pre-fetching that helps an individual chain to run on parallel CPUs.  An inter-chain covariance update is also incorporated to prevent clustering of the chains allowing faster and better mixing of the chains.  Use an adaptive method for covariance calculation to calculate and update the covariance automatically as the chains progress. Analysis shows that the acceptance probability of each step in SCoPE is >95% and the convergence of the chains are faster.  Using SCoPE, carry out some cosmological parameter estimations with different cosmological models using WMAP-9 and Planck results. One of the current research interests in cosmology is quantifying the nature of DE.  Analyze the cosmological parameters from two illustrative commonly used parameterizations of DE models.  Also assess primordial He fraction in the universe can be constrained by the present CMB data form WMAP-9 and Planck.  The results from the MCMC analysis on the one hand help to understand the workability of the SCoPE better, on the other hand it provides a completely independent estimation of cosmological parameters from WMAP-9 and Planck data.

1403.1330
Detection of planets in extremely weak central perturbation microlensing events via next-generation ground-based surveys
Chung, Lee, Koo

For confident detection of planets in extremely weak central perturbation (EWCP) events, it is necessary to have both high cadence monitoring and high photometric accuracy, better than those of current follow-up observation systems.  KMTNet (Korea Microlensing Telescope Network) satisfies these conditions.  Estimat the probability of occurrence of EWCP events with fractional deviations of <2% in high-magnification events and the efficiency of detecting planets in the EWCP events using the KMTNet.  From this study, find that the EWCP events occur with a frequency of >50% in the case of <~100 M_E planets with separations for 0.2 AU <~ d <~20 AU.  Find that for MS and sub giant source stars, 1 M_E planets in EWCP events with the deviations <~ 2% can be detected >50% in a certain range that changes with the planet mass.  However, it is difficult to detect planets in EWCP events of bright stars like giant stars, because it is easy for KMTNet to be saturated around the peak of the events with a constant exposure time.  EWCP events are caused by a close, intermediate, and wide planetary systems with low-mass planets and close and wide planetary systems with massive planets.  Therefore, expect that a much greater variety of planetary systems than those already detected, which are mostly intermediate planetary systems regardless of the planet mass, will be significantly detected in the near future.

1403.1456
A model for multi-property galaxy cluster statistics
Evrard, Arnault, Huterer, Farahi

The massive DM haloes that host groups and clusters of galaxies have observable properties that appear to be log-normally distributed about power-law mean scaling relations in halo mass.  Coupling this assumption with either quadratic or cubic approximations to the mass function in log space, derive closed-form expressions for the space density of haloes as a function of multiple observables as well as forms for the low-order moments of properties of observable -selected samples.  Using a Tinker MF in LCDM, show that the cubic analytic model reproduces results obtained from direct, numerical convolution at the 10% level or better over nearly the full range of observables covered by current observations and for redshifts extending to z=1.5.  The model provides an efficient framework for estimating effects arising from selection and covariance among observable properties in survey samples.