Day 1125

Friday.

1607.06088
A synoptic map of halo substructures from the Pan-STARRS1 3\pi\ Survey
Bernard et al

Present a panoramic map of the entire MW halo north of dec~=-30 degrees (~30,000 deg2), constructed by applying the matched-filter technique to the Pan-STARRS1 3Pi Survey dataset.  Using single-epoch photometry reaching to g~22, this is sensitive to stellar substructures with heliocentric distances between 3.5 and ~35 kpc.  Recover almost all previously-reported streams in this volume and demonstrate that several of these are significantly more extended than earlier datasets have indicated.  In addition, also report 5 new candidate stellar streams.  One of these features appears significantly broader and more luminous than the others and is likely the remnant of a dwarf galaxy.  The other four streams are consistent with a globular cluster origin, and 3 of these are rather short in projection (<10 deg), suggesting that streams like Ophiuchus may not be that rare.  Finally, a significant number of more marginal substructures are also revealed by the analysis; many of these features can also be discerned in matched-filter maps produced by other authors from SDSS data, and hence they are very likely to be genuine.  However, the extant 3Pi data is currently too shallow to determine their properties or produce convincing CMDs.  The global view of the MW provided by Pan-STARRS1 provides further evidence for the important role of both globular cluster disruption and dwarf galaxy accretion in building the MW's stellar halo.


1607.06089
Morphology dependence of stellar age in quenched galaxies at redshift ~1.2: massive compact galaxies are older than more extended ones
Williams, et al

Morphology-dependent stellar age: compact quenched galaxies are 0.5-2 Gyr older than normal-sized ones.  Evidence from 3 different age indicators: Dn4000, H delta_A, and fits to spectral synthesis models.


1607.06099
Testing galaxy quenching theories with scatter in the stellar to halo mass relation
Tinker

Use the scatter in the stellar-to-halo mass relation to constrain galaxy evolution models.  If the efficiency of converting accreted baryons into stars varies with time, haloes of the same present-day mass but different formation histories will have different z=0 galaxy stellar mass.  This is one of the sources of scatter in stellar mass at fixed halo mass, sigma_{log M*}.  For massive haloes that undergo rapid quenching of star formation at z~2, different mechanisms that trigger this quenching yield different values of sigma_log M*.  Use this framework to test various models in which quenching begins after a galaxy crosses threshold in one of the following physical quantities: redshift, halo mass, stellar mass, and stellar-to-halo mass ratio.  The model is highly idealized, with other sources of scatter likely to arise as more physics is included.  Thus, this test is whether a model can produce scatter lower than observational bounds, leaving room for other sources.  Recent measurements find sigma_log M*=0.16 dex for 1e11 Msol galaxies.  Under the assumption that the threshold is constant with time, such a low value of sigma_log M* rules out all of these models wit the exception of quenching by a stellar mass threshold.  Most physical quantities, such as metallicity, will increase scatter if they are uncorrelated with halo formation history.  Thus, to decrease the scatter of a given model, galaxy properties would correlate tightly with formation history, creating testable predictions for their clustering.  Understanding why sigma_log M* is so small may be key to understanding the physics of galaxy formation.


1607.06256
The influence of weak lensing on measurements of the Hubble constant with quad-image gravitational lenses
Jaroszynski, Skowron

Investigate the influence of matter along the LoS and in the SL vicinity on the properties of quad image configurations and on the measurements of H0.  Use simulations of light propagation in a nonuniform universe model with the distribution of matter in space based on the data from Millennium Simulation.  For a given strong lens and haloes in its environment, model the matter distribution along the LoS many times, using different combinations of precomputed deflection maps representing subsequent layers of matter on the path of rays.  Fit the simulated quad image configurations with time delays using nonsingular isothermal ellipsoids (NSIE) with external shear as lens models, treating the Hubble constant as a free parameter.  Get a large artificial catalog of lenses with derived values of the Hubble constant, Hfit.  The average and median of Hfit differ from the true value used in simulations by <0.5 km/s/Mpc which includes the influence of matter along the LoS and in the lens vicinity, and uncertainty in lens parameters, except the slope of the matter distribution, which is fixed.  The characteristic uncertainty of Hfit is ~3 km/s/Mpc.  Substituting the lens shear parameters with values estimated from the simulations reduces the uncertainty to ~2 km/s/Mpc.

Day 1124

Thursday.

1607.05733
A first demonstration of CIB delousing
Larsen, Challinor, Sherwin, Mak

Delensing ins an increasingly important technique to reverse the gravitational lensing of the CMB and thus reveal primordial signals the lensing may obscure.  Present a first demonstration of delousing on Planck temperature maps using CIB.  Reversing the lensing deflections in Planck CMB temperature maps using a linear combination of the 545 and 857 GHz maps as a lensing tracer, find that the lensing effects in the temperature power spectrum are reduced in a manner consistent with theoretical expectations.  In particular, the characteristic sharpening of the acoustic peaks of the temperature power spectrum resulting from successful delensing is detected at a significance of 16 sigma, with an amplitude of A_delens=1.12±0.07 relative to the expected value of unity.  This first demonstration on data of CIB delensing, and of delensing techniques in general, is significant because lensing removal will soon be essential for achieving high-precision constraints on inflationary B-mode polarization.

Day 1123

Wednesday.

1607.05406
Galaxy-galaxy weak lensing measurements from SDSS: I. Image processing and lensing signals
Luo, et al

As the first paper in a series on the study of the gg lensing from SDSS DR7, present the image processing pipeline that corrects the systematics primarily introduced by the PSF.  Using this pipeline, process SDSS DR7 imaging data in r band and generated a background galaxy catalog containing the shape information of each galaxy.  Based on own shape measurements of the galaxy images from SDSS DR7, extract the galaxy-galaxy (GG) lensing signals around foreground spectroscopic galaxies binned in different luminosity and stellar mass.  The overall signals are in good agreement with those obtained by Mandelbaum 05, 06 from SDSS DR4.  The results in this paper with higher signal to noise ratio is due to the larger survey area than SDSS DR4, confirm that more luminous/massive galaxies bear stronger GG lensing signal.  Also divide the foreground galaxies into red/blue and star forming/quenched subsamples and measured their GG lensing signals, respectively.  Find that, at a specific stellar mass/luminosity, the red/quenched galaxies have relatively stronger GG lensing signals than their counterparts especially at large radii.  These GG lensing signals can be used to probe the galaxy-halo mass relations and their environmental dependences in the halo occupation or conditional luminosity function framework.

Day 1122

Thursday.  Friday.  Monday.  Tuesday.

1607.04678
The correlation between halo mass and stellar mass for the most massive galaxies in the universe
Tinker, et al

Present measurements of the clustering of galaxies as function of their stellar mass in BOSS.  Compare the clustering of samples using 12 different methods for estimating stellar mass, isolating the method that has the smallest scatter at fixed halo mass.  In this test, the stellar mass estimate with the smallest errors yields the highest amplitude of clustering at fixed number density.  Find that the PCA stellar masses of Chen+2012 clearly have the tightest correlation with halo mass.  The PCA masses use the full galaxy spectrum, differentiating them from other estimates that only use optical photometric information.  Using the PCA masses, measure the LS bias as a function of Mgal for galaxies with logMgal>=11.4, correcting for incompleteness at the low-mass end of the measurements.  Using the abundance-matching ansatz to connect DM halo mass to stellar mass, construct theoretical models of b(Mgal) that match the same stellar mass function but have different amounts of scatter in stellar mass at fixed halo mass, sigma_logM.  Using this approach, find sigma_logM=0.18±0.02.  This value includes both intrinsic scatter as well as random errors in the stellar masses.  To partially remove the latter, use repeated spectra to estimate statistical errors on the stellar masses, yielding an upper limit to the intrinsic scatter of 0.16 dex.

Day 1121

Wednesday.

1607.03107
Predicting Quiescence: the dependence of specific star formation rate on galaxy size and central density at 0.5<z<2.5
Whitaker et al

Investigate the relationship between star formation and structure, using a mass-complete sample of 27k galaxies at 0.5<z<2.5 from 3D-HST.  Confirm that at fixed stellar mass, SF galaxies are larger than quiescent galaxies at all redshifts.  However, within the SF population, there is no relation between SFR and size: when dividing SF galaxies into quartiles based on their residual offsets in SFR, find that the sizes of galaxies in the highest quartile are 0.27±0.47 dex larger than galaxies in the lowest quartile, a difference that is not significant.  Also show that 50% of all SF in galaxies at fixed stellar mass takes place within a narrow range of sizes (0.26 dex).  Taken together, these results suggest that there is an abrupt cessation of SF after galaxies attain particular structural properties.  Confirming earlier results, find that the central stellar density within a fixed physical radius of 1 kpc is the key parameter connecting galaxy morphology and SFHs: galaxies with high central densities are red and have increasingly lower sSFRs, whereas galaxies with low central densities are blue and have a roughly constant (higher) sSFR at a given redshift interval.  Find remarkable little scatter in the average trends and a strong evolution in the central density (or equivalently central circular velocity) threshold correlated with quiescence.  This quenching threshold decreases by >0.5 dex from z~2 to z~0.7.  Neither a compact galaxy size nor a high n are sufficient to assess the likelihood of quiescence for the average galaxy; rather, it is the combination of these two parameters together with stellar mass that results in a unique quenching threshold in central density or velocity.


1607.03136
Variations of cosmic large-scale structure covariance matrices across parameter space
Reischke, Kiessling, Schäfer

The likelihood function for cosmo params, given by e.g. WL shear measurements, depends on contributions to the covariance induced by the nonlinear evolution of the cosmic web.  As nonlinear clustering to date has only been described by numerical N-body simulations in a reliable and sufficiently precise way, the necessary computational costs for estimating those covariances at different points in parameter space are tremendous.  In this work, describe the change of the matter covariance and of the WL covariance matrix as a function of cosmo parameters by construction a suitable basis, where the contribution to the covariance from NL structure formation using Eulerian perturbation theory at their order is modeled.  Show that the formalism is capable of dealing with large matrices and reproduces expected degeneracies and scaling with cosmo parameters in a reliable way.  Comparing the analytical results to numerical sims found that the method describes the variation of the covariance matrix found in the SUNGLASS WL sim pipeline within the errors at one-loop and tree-level for the spectrum and the trispectrum, respectively, for multipoles up to ell<=1300.  Show that it is possible to optimize the sampling of parameter space where numerical sims should be carried out by minimizing interpolation errors and propose a corresponding method to distribute points in parameter space in an economical way.


1607.03143 through 03155  (13 papers)
SDSS-III BOSS final set of papers

Day 1120

Tuesday.

1607.02507
How to quench a galaxy
Pontoon, Tremmel, Roth, Peiris, Saintonge, Volonteri, Quinn, Governato

Show how the interplay between AGN and merger history determines whether a galaxy quenches SF at high z.  First simulate, in a full cosmo context, a galaxy of total dynamical mass 1e12 Msun at z=2.  Then systematically alter the accretion history of the galaxy by minimally changing the linear overdensity in the initial conditions.  This "genetic modification" approach allows the generation of 3 sets of LCDM initial conditions leading to maximum merger ratios of 1:10, 1:5, and 2:3 respectively.  The changes leave the final halo mass, LSS and local environment unchanged, to a star-forming, temporarily-quenched and permanently-quenched galaxy.  However the differences do not primarily lie in the BH accretion rates, but in the kinetic effects of the merger: the galaxy is resilient against AGN feedback unless its gaseous disk is first disrupted.  Typical accretion rates are comparable in the 3 cases, falling below 0.1 Msun/yr, equivalent to around 2% of the Eddington rate or 1e-3 times the pre-quenching SFR, in agreement with observations.  This low level of BH accretion can be sustained even when there is insufficient dense cold gas for SF.  Conversely, SN feedback is too distributed to generate outflows in high-mass systems, and cannot maintain quenching over periods longer than the halo gas cooling time.


1607.02596
Large-scale fluctuations in the number density of galaxies in independent surveys of deep fields
Shirokov, et al

New arguments supporting the reality of LS fluctuations in the density of the visible matter in deep galaxy surveys are presented.  A statistical analysis of the radial distributions of galaxies in the COSMOS and HDF-N deep fields is presented.  Independent spectral and photometric surveys exist for each field, carried out in different wavelength ranges and using different observing methods.  Catalogs of photo-z in the optical (COSMOS-Zphot) and IR (UltraVISTA) were used for the COSMOS field in 0.1<z<3.5, as well as the zCOSMOS (10kZ) spec-z survey and the XMM-COSMOS and ALHAMBRA-F4 photo-z surveys.  The HDFN-Zphot and ALHAMBRA-F5 catalogs of photo-z were used for the HDF-N field.  The Pearson correlation coefficient for the fluctuations in the numbers of galaxies obtained for independent surveys of the same deep field reaches R=0.70±0.16.  The presence of this positive correlation supports the reality of fluctuations in the density of visible matter with sizes of up to 1k Mpc and amplitudes of up to 20% at z~2.  The absence of correlations between the fluctuations in different fields (the correlation coefficient between COSMOS and HDF-N is r=-0.20±0.31 testifies to the independence of structures visible in different directions on the celestial sphere.  This also indicates an absence of any influence from universal systematic errors (such as "spectral voids"), which could imitate the detection of correlated structures.


1607.02971
GAMA/H-ATLAS: common star-formation rate indicators and their dependence on galaxy physical parameters
Wang, et al

Compare common SFR indicators in the local Universe in the GAMA equatorial fields (around 160 sq. deg), using UV photometry from GALEX, FIR and sub-mm photometry from H-ATLAS, and Halpha spectroscopy from the GAMA survey.  With a high-quality sample of 745 galaxies (median redshift 0.08), consider 3 SFR tracers: UV luminosity corrected for dust attenuation using the UV spectral slope beta (SFRUV,corr), Halpha line luminosity corrected for dust using the Balmer decrement (BD) (SFRHalpha,corr), and the combination of UV and IR emission (SFRUV+IR).  Demonstrate the SFRUV,corr can be reconciled with the other 2 tracers after applying attenuation corrections by calibrating IRX (i.e. the IR to UV luminosity ratio) and attenuation in the Halpha (derived from BD) against beta.  However, beta on its own is very unlikely to be a reliable attenuation indicator.  Find that attenuation correction factors depend on parameters such as stellar mass, z and dust temperature (Tdust), but not on Halpha equivalent width (EW) or Sersic index.  Due to the large scatter in the IRX vs beta correlation, when compared to SFRUV+IR, the beta-corrected SFRUV,corr exhibits systematic deviations as a function of IRX,BD and Tdust.

Day 1119

Monday.

1607.02215
Dawes Review 5: Australian Aboriginal Astronomy and Navigation
Norris

The traditional cultures of Aboriginal Australians include a significant astronomical component, perpetuated through oral tradition, ceremony, and art.  This astronomical knowledge includes a deep understanding of the motion of objects in the sky, which was used for practical purposes such as constructing calendars and for navigation.  There is also evidence that traditional Aboriginal Australians made careful records and measurements of cyclical phenomena, recorded unexpected phenomena such as eclipses and meteorite impacts, and could determine the cardinal points to an accuracy of a few degrees.  Putative explanations of celestial phenomena appear throughout the oral record, suggesting traditional Aboriginal Australians sought to understand the natural world around them, in the same way as modern scientists, but within their own cultural context.  There is also a growing body of evidence for sophisticated navigational skills, including the use of astronomically based longlines.  Longlines are effectively oral maps of the landscape, and are an efficient way of transmitting oral navigational skills in cultures that do not have a written language.  The study of Aboriginal astronomy has had an impact extending beyond mere academic curiosity, facilitating cross-cultural understanding, demonstrating the intimate links between science and culture, and helping students to engage with science.


1607.02417
Unbiased contaminant removal for 3D galaxy power spectrum measurements
Klaus, Percival, Bacon, Samushia

Assess and develop techniques to remove contaminants when calculating the 3d galaxy power spectrum.  Separate the process into 3 separate stages: (i) removing the contaminant signal, (ii) estimating the uncontaminated cosmo power spectrum, (iii) debasing the resulting estimates.  For (i), show that removing the best-fit contaminant (template subtraction), and setting the contaminated components of the covariance to be infinite (mode deprojection) are mathematically equivalent.  For (ii), performing a Quadratic Maximum Likelihood (QML) estimate after mode deprojection gives an optimal unbiased solution, although it requires the manipulation of large (N^2-mode) matrices, which is unfeasible for recent 3d galaxy surveys.  Measuring a binned average of the modes for (ii) as proposed by Feldman, Kaiser & Peacock (1994, FKP) is faster and simpler, but is sub-optimal and gives rise to a biased solution.  Present a method to debits the resulting FKP measurements that does not require any large matrix calculations.  Argue that the sub-optimality of the FKP estimator compared with the QML estimator, caused by contaminants is less severe than that commonly ignored due to the survey window.

Day 1118

Friday.

1607.01782
Approximate Bayesian Computation in large scale structure: constraining the galaxy-halo connection
Hahn, et al

The standard approaches to Bayesian parameter inference in LSS assume a Gaussian functional from (chi2 form) for the likelihood.  They are also typically restricted to measurements such as the 2pcf.  Likelihood free inferences such as Approximate Bayesian Computation (ABC) make inference possible without assuming any functional form for the likelihood, thereby relaxing the assumptions and restrictions of the standard approach.  Instead it relies on a forward generative model of the data and a metric for measuring the distance between the model and data.  In this work, demonstrate that ABC is feasible for LSS parameter inference by using it to constraining parameters of the HOD model for populating DM haloes with galaxies.  Using specific implementation of ABC supplemented with Population Monte Carlo importance sampling, a generative forward model using HOD, and a distance metric based on galaxy number density, 2pcf, and galaxy group multiplicity function, constrain the HOD parameters of mock observation generated rom selected "true" HOD parameters.  The parameter constraints obtained from ABC are consistent with the "true" HOD parameters, demonstrating that ABC can be reliably used for parameter inference in LSS.  Furthermore, compare the ABC constraints to constraints obtained using a pseudo-likelihood function of Gaussian form with MCMC and find consistent HOD parameter constraints.  Ultimately the results suggest that ABC can and should be applied in parameter inference of LSS analyses.


1607.02056
Shear Nulling after PSF Gaussianization: moment-based weak lensing measurements with sub percent noise bias
Herbonnet, Buddendiek, Kuijken

Current optical imaging surveys for cosmology are covering large areas of sky.  To exploit the statistical power of these surveys for WL measurements requires shape measurement methods with sub percent systematic errors.  Introduce a new WL shear measurement algorithm, SNAPG, designed to avoid the noise biases that affect most other methods.  SNAPG operates on images that have been convolved with a kernel that renders the PSF a circular Gaussian, and uses weighted second moments of the sources.  The response of such second moments to a shear of the pre-seeing galaxy image can be predicted analytically, allowing to construct a shear nulling scheme that finds the shear parameters for which the observed galaxies are consistent with an unsheared, isotropically oriented population of sources.  The inverse of this nulling shear is then an estimate of the gravitational lensing shear.  Identify the uncertainty of the estimated center of each galaxy as the source of noise bias, and incorporate an approximate estimate of the centroid covariance into the scheme.  Test the method on extensive suits of simulated galaxies of increasing complexity, and find that it is capable of shear measurement with multiplicative bias below 0.5%.

Day 1117

Thursday.

1607.01406
Evolution of cosmic filaments and of their galaxy population from NHD cosmological simulations
Heller, et al

Despite containing about a half of the total matter in the Universe, at most wavelengths the filamentary structure of the cosmic web is difficult to observe.  In this work, use large unigrid cosmological sims to investigate how the geometrical, thermodynamical and magnetic properties of cosmo filaments vary with mass and redshift (z<=1).  Find that the average temperature, length, volume and magnetic field of filaments are tightly log-log correlated with the underlying total gravitational mass.  This reflects the role of self-gravity in shaping their properties of the simulated population of galaxy-sized haloes within filaments, and compare their properties to the results obtained from the spectroscopic GAMA survey.  Simulated and observed filaments with the same length are found to contain an equal number of galaxies, with very similar distribution of halo masses.  The total number of galaxies within each filament and the total/average stellar mass in galaxies can now be used to predict also the large-scale properties of the gas in the host filaments across tens of hundreds of Mpc in scale.  These results are the first steps towards the future use of galaxy catalogues in order to select the best targets for observations of the warm-hot IGM.


1607.01761
Looking through the same lens: shear calibration for LSST, Euclid & WFIRST with stage 4 CMB lensing
Sichuan, Krause, Eifel, Doré, Miyatake, Rhodes, Spergel

The next generation WL surveys (LSST, Euclid, WFIRST) will require exquisite control over systematic effects.  In this paper, address shear calibration and present the most realistic forecast to date for LSST/Euclid/WFIRST and CMB lensing from a stage 4 CMB experiment (CMB S4).  Use the CosmoLike code to simulate a joint analysis of all the 2pt functions of galaxy density, galaxy shear and CMB lensing convergence.  Include the full Gaussian and non-Gaussian covariances and explore the resulting joint likelihood with MCMC.  Constrain shear calibration biases while simultaneously varying cosmo parameters, galaxy biases and photo-z uncertainties.  Find that CMB lensing from CMB S4 enables the calibration of the shear biases down to 0.2%-3% in 10 tomographic bins for LSST (below the ~0.5% requirements in most tomographic bins), down to 0.4%-2.4% in 10 bins for Euclid and 0.6%-3.2% in 10 bins for WFIRST.  For a given lensing survey, the method works best at high z where shear calibration is otherwise most challenging.  This self-calibration is robust to Gaussian photo-z uncertainties and to a reasonable level of intrinsic alignment.  It is also robust to changes in the beam and the effectiveness of the component separation of the CMB experiment, and slowly dependent on its depth, making it possible with third generation CMB experiments such as AdvACT and SPT-3G, as well as the Simons Observatory.

Day 1116

Wednesday.

1606.01014
Integrated approach to cosmology: combining CMB, large-scale structure and weak lensing
Nicola, Refregier, Amara

Recent observational progress has led to the establishment of the standard LCDM model for cosmology.  This development is based on different cosmological probes that are usually combined through their likelihoods at the latest stage in the analysis.  Implement here an integrated scheme for cosmo probes, which are combined in a common framework starting at the map level.  This treatment is necessary as the probes are generally derived from overlapping maps and are thus not independent.  It also allows for a thorough test of the cosmo model and of systematics through the consistency of different physical tracers.  As a first application, combine current measurements of CMB from Planck, and galaxy clustering from SDSS.  Consider the spherical harmonic power spectra of these probes including all six auto- and cross-correlations along with the associated full gaussian covariance matrix.  This provides an integrated treatment of different analyses usually performed separately including CMB anisotropies, cosmic shear, galaxy clustering, gg lensing and the ISW effect with galaxy and shear tracers.  Derive constraints on LCDM parameters which are compatible with existing constraints and highlight tensions between data sets, which become apparent in this integrated treatment.  Discuss how this approach provides a complete and powerful integrated framework for probe combination and how it can be extended to include the tracers in the context of current and future wide field cosmo surveys.


1607.01047
H0LiCOW III. Quantifying the effect of mass along the line of sight to the gravitational lens HE 0435-1223 through weighted galaxy counts
Rusu, et al

Based on spectra and multi band wide-field observations of the gravitationally lensed quasar HE 0435-1223, determine the probability distribution function of the external convergence kappa_ext for this system.  Measure the under/overdensity of the LoS towards the lens system and compare it to the average LoS throughout the universe, determined by using the CFHTLenS as a control field.  Aiming to constrain kappa_ext as tightly as possible, determine under/overdensities using various combinations of relevant informative weighing schemes for the galaxy counts, such as projected distance to the lens, redshift, and stellar mass.  Then convert the measured under/overdensities into a kappa_ext distribution, using ray-tracing through the Millennium sims.  Explore several limiting magnitudes and apertures, and account for systematic and statistical uncertainties relevant to the quality of the observational data, which is further tested through simulations.  The most robust estimate of kappa_ext has a median value kappa_ext^med=0.004 and a standard deviation of sigma_kappa=0.025.  The measured sigma_kappa corresponds to 2.5% uncertainty on the time delay distance, and hence the Hubble constant H0 inference from this system.  The median kappa_ext^med value is robust to ~0.005 (i.e. ~0.5% on H0) regardless of the adopted aperture radius, limiting magnitude and wighting scheme, as long as the latter incorporates galaxy number counts, the projected distance to the main lens, and a prior on the external shear obtained from mass modeling.  The availability of a well-constrained kappa_ext makes the quad a valuable system for measuring cosmo params using SL time delays.


1607.01189
The SuperCOSMOS all-sky galaxy catalogue
Peacock, Humbly, Bilicki, MacGillivray, Miller, Read, Tritton

Describe the construction of an all-sky galaxy catalogue, using SueprCOSMOS scans of Schmidt photographic plates from the UKST and POSS2 surveys.  The photographic photometry is calibrated using SDSS data, with results that are linear to 2% or better.  All-sky photometric uniformity is achieved by matching plate overlaps and also by requiring homogeneity in optical-to-2MASS colors, yielding zero points that are uniform to 0.03 mag or better.  The typical AB depths achieved are B_J<21, R_F<19.5, and I_N<18.5, with little difference between hemispheres.  In practice, the I_N plates are shallower than the B_J & R_F plates, so for most purposes advocate the use of a catalogue selected in these two latter bands.  At high Galactic latitudes, this catalogues is approximately 90% complete with 5% stellar contamination, quantify how the quality degrades towards the Galactic plane.  At low latitudes, there are many spurious galaxy candidates resulting from stellar blends: these approximately match the surface density of true galaxies at |b|=30 deg.  Above this latitude, the catalogue limited in B_J & R_F contains in total about 20M galaxy candidates, of which 75% are real.  This contamination can be removed, and the sky coverage extended, by matching with additional datasets.  This SuperCOSMOS catalogue has been matched with 2MASS and with WISE, yielding quasi-allsky samples of respectively 1.5 million and 18.5 million galaxies, to median redshifts of 0.08 and 0.20.  This legacy dataset thus continues to offer a valuable resource for large-angle cosmo investigations.

Day 1115

Tuesday.

1606.00382
H0LiCOW II. Spectroscopic survey and galaxy-group identification of the strong gravitational lens system HE0435-1223
Sluse et al

Galaxies located in the environment or on the line of sight towards gravitational lenses can significantly affect lensing observables, and can lead to systematic errors on the measurement of H0 from the time-delay technique.  Present the results of a systematic spectroscopic identification of the galaxies in the field of view of the lensed quasar HE0435-1223, using Keck, Gemini and ESO-VLTs.  The new catalog triples the number of known galaxy redshifts in the vicinity of the lens, expanding to 100 the number of measured redshifts for galaxies separated by less than 3 arcmin from the lens.  Complement the catalog with literature data to gather redshifts up to 15 arcmin form the lens, and search for galaxy groups or cluster projected towards HE0435-1223.  Confirm that the lens is a member of a small group that includes at least 12 galaxies, and find 8 other group candidates near the line of sight of the lens.  The flexion shift, namely the shift of lensed images produced by high order perturbation of the lens potential, is calculated for each galaxy/group and used to identify which objects produce the largest perturbation of the lens potential.  This analysis demonstrates that i) at most 3 of the 5 brightest galaxies projected within 12 arcsec of the lens need to be explicitly used in the lens models, and ii) the groups can be treated in the lens model as an external tidal field (shear) contribution.  The statistical impact of the groups and voids on the lens model is presented in a companion paper H0LiCOW III.  The exhaustive lens modeling of HE0435-1223, used for cosmo inference, including all the environmental sources of systematic errors, is presented in another companion paper H0LiCOW IV.

Day 1114

Friday.  Monday.

1606.00008
Cosmological parameters, shear maps and power spectra from CFHTLenS using Bayesian hierarchical inference
Alsing, Heavens, Jaffe

Apply two Bayesian hierarchical inference schemes to infer shear power spectra, shear mass and cosmo parameters from the CFHTLenS WL survey -- the first application of this method to data.  In the first approach, sample the joint posterior distribution of the shear maps and power spectra by Gibbs sampling, with minimal model assumptions.  In the second approach, sample the joint posterior of the shear maps and cosmo parameters, providing a new, accurate and principled approach to cosmo parameter inference from cosmic shear data.  As a first demonstration on data, perform a 2-bin tomographic analysis to constrain cosmo parameters and investigate the possibility of photometric z bias in the CFHTLenS data.  Under the baseline LCDM model, constrain S8=sigma_8(Omega_m/0.3)^0.5 = 0.67 ±0.03 (68%), consistent with previous CFHTLenS analysis by in tension with Planck.  Adding neutrino mass as a free parameter, able to constrain Sigma m_nu<4.6 eV (95%) using CFHTLenS data alone.  Including a linear redshift dependent photo-z bias Delta z=p_2(z-p_1), find p_1 = -0.25±0.6 and p_2=-0.15 ±0.15, and tension with Planck is only alleviated under very conservative prior assumptions.  Neither the non-minimal neutrino mass or photo-z bias models are significantly preferred by the CFHTLenS(2-bin tomography) data.


1606.00017
H0LiCOW I.  H0 lenses in COSMOGRAIL's Wellspring: program overview
Sulu, Bonvin, Corbin, Fassnacht, Rush, Sluse, Treu, ..Hilbert, Marshall .. Tewes, ... Blandford, et al

SL systems with time delays between the multiple images are a powerful probe of cosmo and astrophysics.  In particular, the time-delay distance from such a system is primarily sensitive to the Hubble Constant that is key to probing DE, neutrino physics, and the spatial curvature of the Universe, as well as discovering new physics.  Present H0LiCOW, a program that aims to measure H0 with <3.5% uncertainty in precision and accuracy from 5 lens systems.  Acquired or are in the process of acquiring (1) time delays through COSMOGRAIL and VLA monitoring, (2) high-resolution HST imaging for the lens mass modeling, (3) wide-field imaging and spectroscopy to characterize the lens environment, and (4) moderate-resolution spectroscopy for obtaining the stellar velocity dispersion of the lenses and, thus, to further constrain the lens mass models.  Expect to measure, with the data set for the five lenses, H0 and better than 3.5% in most cosmological models.  Furthermore, would measure spatial curvature Omega_k to 0.004, w to 0.14, and the effective number of neutrino species to 0.2 (1sigma) when combined with current CMB experiments, which are a factor of ~15, ~2 and ~1.5 tighter than CMB aline.  The data set will further enable to study the dark matter distribution of lens galaxies, the stellar initial mass function of the lens galaxies, and the co-evolution of supermassive BHs and their host (source) galaxies. This program will provide a foundation for extracting robustly cosmo distances from the hundreds of time-delay lenses that are expected to be discovered in current and future surveys.


1606.00043
Perturbative approach to covariance matrix of the matter power spectrum
Mohammed, Seljak, Vlah

Evaluate the cov matrix of the matter PS using perturbation theory up to dominant terms at 1-loop order and compare it to numerical simulations.  Decompose the cov matrix into the disconnected (Gaussian) part, trispectrum from the modes outside the survey (beat coupling or super-sample variance), and trispectrum from the modes inside the survey, and show how the different components contribute to the overall covariance matrix.  Find the agreement with the simulations is at a 10% level up to k~1h/Mpc.  Show that all the connected components are dominated by the large-scale models (k<0.1 h/Mpc), regardless of the value of the wavelvectors k,k' of the cov matrix, suggesting that one must be careful in applying the jackknife or bootstrap methods to the cov matrix.   Perform an eigen mode decomposition of the connected part of the cov matrix, showing that at higher k it is dominated by a single eigenmode.  The full cov matrix can be approximated as the disconnected part only, with the connected part being treated as an external nuisance parameter with a known scale dependence, and a known prior on its variance for given survey volume.  Finally, provide a prescription for how to evaluate the cov matrix from small box simulations without the need to simulated large volumes.


1606.00184
Constraining $f(R)$ gravity theory using CHFTLenS Weak Lensing Peak statistics
Liu, et al

Report the observational constraints on the Hu-Sawicki f(R) theory derived from WL peak abundances, which are closely related to the MF of massive halos.  In comparison with studies using optical or X-ray clusters of galaxies, WL peak analyses have the advantages of not relying on mass-baryonic observable calibration.  From CFHTLenS, peak analysis give rise to a tight constant on the model parameter |f_R0| for n=1.  The 95% CL limit is log_10|f_R0|<-4.82 given WMAP9 priors on (Omega_m, A_s).  With Planck15 priors, the corresponding result is log_10|f_R0|<-5.16.