Day 1192

Wednesday.

1611.09362
Hints against the cold and collisionless nature of dark matter from the galaxy velocity function
Schneider, et al

The observed number of dwarf galaxies as a function of rotation velocity is significantly smaller than predicted by the LCDM model.  This discrepancy cannot be simply solved by assuming wrong baryonic processes, since they would violate the observed relation between maximum circular velocity (v_max) and baryon mass of galaxies.  A speculative possibility is that the mismatch between observation and theory points towards the existence of non-cold or non-collisionless DM.  In this paper, investigate the effects of warm, mixed (i.e. warm plus cold), and self-interacting DM scenarios on the abundance of dwarf galaxies and the relation between observed HI line-width and maximum circular velocity.  Both effects have the potential to alleviate the apparent mismatch between the observed and theoretical abundance of galaxies as a function of v_max.  For the case of warm and mixed DM, show that the discrepancy disappears, even for lukewarm models that evade stringent bounds from the Lyman-a forest.  Self-Interacting DM scenarios can also provide a solution as long as they lead to extended (>~1.5 kpc) DM cores in the density profiles of dwarf galaxies.  Only models with velocity-dependent cross sections can yield such cores without violating other observational constraints at larger scales.


1611.09366
Lensing constraints on the mass profile shape and splash back radius of galaxy clusters
Umetsu, Diemer

The lensing signal around galaxy clusters can, in principle, be used to test detailed predictions of their average mass profile from numerical simulations.  However, the intrinsic shape of the profiles can be smeared out when a sample that spans a wide range of cluster masses is averaged in physical length units.  This effect especially conceals rapid changes in gradient such as the steep drop associated with the splash back radius, a sharp edge corresponding to the outermost caustic in accreting halos.  Optimize the extraction of such local features by scaling individual halo profiles to a number of spherical overdensity radii, and apply this method to 16 Xray-selected high-mass clusters targeted in the Cluster Lensing and Supernova survey with Hubble (CLASH).  By forward-modeling the weak and strong lensing data presented in Umetsu et al., show that, regardless of the scaling overdensity, the projected ensemble density profile is remarkably well described by an NFW or Einasto profile out to R~2.5 Mpc/h, beyond which the profiles flatten.  Constrain the NFW concentration to c_200_c = 3.66±0.11 at M_200c~1e15 Msun/h, consistent with and improved from previous work that used conventionally stacked lensing profiles, and in excellent agreement with theoretical expectations.  Assuming the profile form of Diemer & Kravtsov and generic priors calibrated from numerical simulations, place a lower limit on the splash back radius of the cluster halos, if it exists, to be R_sp/r_200m>0.89 (R_sp>1.83 Mpc/h) at 68% confidence.  The corresponding density features is most pronounced when the cluster profiles are scaled by r_200m, and smeared out when scaled to higher overdensities.


1611.09459
How to find gravitationally lensed type Ia supernovae
Goldstein, Nugent

SNe Ia that are multiply imaged by GL can extend the SN Ia Hubble diagram to very high redshifts (z>~2), probe potential SN Ia evolution, and deliver high-precision constraints on H0, w, and Omega_m via time delays.  However, only one have been found to date, while many are needed to achieve these goals.  To increase the multiply imaged SN Ia discovery rate, present a simple algorithm for identifying gravitationally lensed SN Ia candidates in cadenced, wide-field optical imaging surveys.  The technique is to look for Se that appear to have an elliptical galaxy as their host with an absolute magnitude implied by the host's photometric redshift that is far brighter than the absolute magnitude of a normal SNIa (the brightest type of SN found in elliptical galaxies).  Importantly, this purely photometric method does not require the ability to resolve the lensed images for discovery.  The primary sources of contamination that affect the method are AGN and SF galaxies, but these can be controlled using catalog cross-matches and color cuts.  Highly magnified core-collapse SNe will also be discovered as a byproduct of the method.  Using MC sim, forecast that LSST can discover 500 multiply imaged SNe Ia using this technique in a 10-year z-band search, more than an order of magnitude improvement over previous estimates.  Also find the the Zwicky Transient Facility should find 10 multiply imaged SNe Ia using this technique in a 3-year R-band search -- despite the fact that this survey will not resolve a single system.

Day 1191

(Black Friday).  Monday.  Tuesday.

1611.08467
The design strategy of scientific data quality control software for Euclid mission
Brescia et al

The most valuable asset of a space mission like Euclid are the data.  Due to their huge volume, the automatic quality control becomes a crucial aspect over the entire lifetime of the experiment.  Here, focus on the design strategy for the Science Ground Segment (SGS) Data Quality Common Tools (DQCT), which has the main role to provide SW solutions to gather, evaluate, and record quality information about the raw and derived data products from a primarily scientific perspective.  The SGS DQCT will provide a quantitive basis for evaluating the application of reduction and calibration reference data, as well as diagnostic tools for quality parameters, flags, trend analysis diagrams and any other metadata parameter produced by the pipeline.  In a large program like Euclid, it is prohibitively expensive to process large amount of data at the pixel level just for the purpose of quality evaluation.  Thus, all measures of quality at the pixel level are implemented in the individual pipeline stages, and passed along as metadata in the production.  In this sense most of the tasks related to science data quality are delegated to the pipeline stages, even though the responsibility for science data quality is managed at a higher level.  The DQCT subsystem of the SGS is currently under development, but its path to full realization will likely be different than that of other subsystems.  Primarily because, due to a high level of parallelism and to the wide pipeline processing redundancy, for instance the mechanism of double SDC for each processing function, the data quality tools have not only to be widely spread over all pipeline segments and data levels, but also to minimize the occurrences of potential diversity of solutions implemented for similar functions, ensuring the maximum of coherency and standardization for quality evaluation and reporting in the SGS.


1611.08606
Lensing is Low: cosmology, galaxy formation, or new physics?
Leauthaud, Saito, Hilbert, ... et al

Present high S/N GGL measurements of the BOSS CMASS sample using 250 square degrees of WL data from CFHTLenS and CS82.  Compare this signal with predictions from mock catalogs trained to match observables including the stellar mass function and the projected and 2d clustering of CMASS.  Show that the clustering of CMASS, together with standard models of the galaxy-halo connection, robustly predicts a lensing signal that is 20-40% larger than observed.  Detailed tests show that the results are robust to a variety of systematic effects.  Lowering the value of S8=sigma8 sqrt(Omega_m/0.3) compared to Planck 2015 reconciles the lensing with clustering.  However, given the scale of the measurement (r<10 Mpc/h), other effects may also be at play and need to be taken into consideration.  Explore the impact of baryon physics, assembly bias, massive neutrinos, and modifications to general relativity on DeltaSigma and show that several of these effects may be non-negligible given the precision of the measurement.  Disentangling cosmo effects form the details of the galaxy-halo connection, the effects of baryons, and massive neutrinos, is the next challenge facing joint lensing and clustering analyses. This is especially true in the context of large galaxy sample from BAO surveys with precise measurements but complex selection functions.

Day 1190

Monday.  Tuesday.  Wednesday.  Thursday.

1611.07526
The weirdest SDSS galaxies: results from an outlier detection algorithm
Baron, Poznanski

Present an outlier detection algorithm, based on an unsupervised Random Forest.  Test the algorithm on more than 2M spectra from SDSS and examine the 400 galaxies with the highest outlier score.  Find objects which have extreme emission line ratios and abnormally strong absorption lines, objects with unusual continua, including extremely reddened galaxies.  Find galaxy-galaxy gravitational lenses, double-peaked emission line galaxies, and close galaxy pairs.  Find galaxies with high ionization lines, galaxies which host See, and galaxies with unusual gas kinematics.  Only a fraction of the outliers found were reported by previous studies that used specific and tailored algorithms to find a single class of unusual objects.  The algorithm is general and detects all of these classes, and many more, regardless of what makes them peculiar.  It can be executed on imaging, time-serious, and other spectroscopic data, operates well with 1000s of features, is not sensitive to missing values, and is easily parallelisable.


1611.07578
2dFLenS and KiDS: determining source redshift distributions with cross-correlations
Johnson, Blake, Amon, Erben, et al

Develop a statistical estimator to infer the z probability distribution of a photometric sample of galaxies from its angular cross-correlation in z bins with an overlapping spectroscopic sample.  This estimator is a minimum variance weighted quadratic function of the data: a quadratic estimator.  This extends and modifies the methodology presented by McQuinn&White (2013).  The derived source z distribution is degenerate with the source galaxy bias, which must be constrained via additional assumptions.  Apply this estimator to constrain source galaxy z distributions in the KiDS imaging survey through cross-correlation with the spectroscopic 2-degree Field Lensing Survey, presenting results first as a binned step-wise distribution in the range z<0.8, and then building a continuous distribution using a Gaussian process model.  Demonstrate the robustness of the methodology using mock catalogues constructed from N-body sims, and comparisons with other techniques for inferring the z distribution.

Day 1189

Friday.

1611.05625
Hayabusa-2 missing target asteroid 162173 Ryugu (1999 JU3): searching for the Object's spin-axis orientation
Müller, et al

The JAXA Hayabusa-2 mission was approved in 2010 and launched on Dec 3 2014.  The spacecraft will arrive at the near-Earth asteroid 162173 Ryugu in 2018 where it will perform a survey, land and obtain surface material, then depart in Dec 2019 and return to Earth in Dec 2020.  Observed Ryugu with the Herschel Space Observatory in Apr 2012 at far-IR thermal wavelengths, supported by several ground-based observations to obtain optical light curves.  Re-analysed previously published Subaru-COMICS and AKARI-IRC observations and merged them with a Spitzer-IRS data set.  In addition, used a large set of Spitzer-IRAC observations obtained in the period Jan to May, 2013.  The data set includes 2 complete rotational light curves and a series of ten "point-and-shoot" observations.  The almost spherical shape of the target together with the insufficient light curve quality forced a combination of radiometric and light curve inversion techniques in different ways to find the object's key physical and thermal parameters.  Find that the solution which best matches the data sets leads to this C class asteroid having a retrograde rotation with a spin-axis orientation of (lambda=310-340 deg; beta=040±15 deg) in ecliptic coordinates, an effective diameter (of an equal-voume sphere) of 850 to 880 m, a geometric albedo of 0.044 to 0.050 and a thermal inertia in the range 150 to 300 Jm-2s-0.5K-1.  Based on estimated thermal conductivities of the top-layer surface in the range 0.1 to 0.6 WK-1m-1, calculate that the grain sizes are approximately equal to between 1 and 10 mm.  The finely constrained values for this asteroid serve as a 'design reference model', which is currently used for various planning, operational and modelling purposes by the Hayabusa2 team.

Day 1188

Thursday.

1611.05039
The structural and size evolution of star-forming galaxies over the last 11 Gyrs
Paulino-Afonso, et al

Present new results on the evolution of the rest-frame blue/UV sizes and Sersic indices of Halpha-selected SF galaxies over the last 11 Gyrs.  Investigate how the perceived evolution can be affected by a range of biases and systematics such as cosmo dimming and resolution effects.  Use GALFIT and an artificial redshifting technique, which includes the luminosity evolution of Halpha-selected galaxies, to quantify the change on the measured structural parameters with redshift.  Find typical sizes of 2 to 3 kpc and Sersic indices of n~1.2, close to pure exponential disks all the way from z=2.23 to z=0.4.  At z=0 find typical sizes of 4-5 kpc.  The results show that, when using GALFIT, Cosmo dimming has a negligible impact on the derived effective radius for galaxies with <10 kpc, but find a ~20% bias on the estimate of the median Sersic indices, rendering galaxies more disk-like.  SF galaxies have grown on average by a factor of 2-3 in the last 11 Yrs with r_e~(1+z)^-0.75.  By exploring the evolution of the stellar mass-size relation, find evidence for a stronger size evolution of the most massive SF galaxies since z~2, as they grow faster towards z~0 when compared to the lower stellar mass counterparts.  As the rest-frame blue/UV are being traced, we are likely witnessing the growth of disks where SF is ongoing in galaxies while their profiles remain close to exponential disks, n<1.5, across the same period.

Day 1187

Wednesday.

1611.04954
The limits of cosmic shear
Kitching, Alsing, Heavens, Jimenez, McEwen, Verde

Discuss the commonly-used approximates for 2pt cosmic shear statistics.  Discuss the 4 most prominent assumptions in they statistic: the flat-sky, tomographic, Limber and configuration-space approximations, that the vast majority of cosmic shear results to date have used simultaneously.  Of these approximations, find that the flat-sky approximation suppresses power by >1% on scales of l<100 and the standard Limber approximation implementation enhances power by >5% on scales l<100; in doing so, find an l-dependent factor that has been neglected in analyses to date.  To investigate the impact of these approximations, reanalyze the CFHTLenS 2D correlation function results.  When using all approximations, reproduce the results that measurements of the matter PS amplitude are in tension with measurement from the CMB Planck data: where a conditional value of sigma8=0.789±0.015 is found from CFHTLenS and sigma8=0.830±0.015 from Planck.  When the Limber and flat-sky approximations are not used, find a conditional value of sigma8=0.801±0.016 from CFHTLenS, significantly reducing the tension between Planck CMB results and lensing results from CFHTLenS.  When including the additional effect of expected photos biases, find sigma8=0839±0.017 which is consistent with Planck.  Also discuss the impact on CMB lensing.  For Euclid, LSST, and WFIRST and any current or future survey none of these approximations should be used.

Day 1186

Tuesday.

1611.03859
Rocky Planetesimal formation via fluffy aggregates of nanograins
Arakawa, Nakamoto

Several pieces of evidence suggest that silicate grains in primitive meteorites are not interstellar grains but condensates formed in the early solar system.  Moreover, the size distribution of matrix grains in chondrites implies that these condensates might be formed as nanometer-sized grains.  Therefore, propose a novel scenario for rocky planetesimal formation in which nanometer-sized silicate grains are produced by evaporation and recondensation events in early solar nebula, and rocky planetesimals are formed via aggregation of these nano grains.  Reveal that silicate nano grains can grow into rocky planetesimals via direct aggregations without catastrophic fragmentation and serious radial drift, and the results provide a suitable condition for protoplanet formation in the SS.


1611.03866
Cluster mass calibration at high redshift: HST weak lensing analysis of 13 distant galaxy clusters from the South Pole Telescope Sunyaev-Zel'dovich survey
Schrabback, Applegate, Dietrich, Hoekstra, et al

Present an HST/ACS WL analysis of 13 massive high-z (z_median=0.88) galaxy clusters discovered in SPT SZ survey.  This study is part of a larger campaign that aims to robustly calibrate mass-observable scaling relations over a wide range in redshift to enable improved cosmo constraints from the SPT cluster sample.  Introduce new strategies to ensure that systematics in the lensing analysis do not degrade constraints on cluster scale relations significantly.  First, efficiently remove cluster members from the source sample by selecting very blue galaxies in V-I colour.  The estimate of the source redshift distribution is based on CANDELS data, where source selection criteria of the cluster fields is carefully mimicked.  Apply a statistical correction for systematic photo-z errors as derived form Hubble UDF data and verified through spatial cross-correlations.  Account for the impact of lensing magnification on the source redshift distribution, finding that this is particularly relevant for shallower surveys.  Finally, account for biases in the mass modelling caused by miscentering and uncertainties in the m-c relation using sims.  In combination with temperature estimates from Chandra, constrain the normalization of the m-T scaling relation ln(E(z) M_500c/1e14 Msun) = A+1.5 ln(kT/7.2 keV) to A=1.81+0.24-0.14(stat.) ± 0.09 (sys.), consistent with self-similar z evolution when compared to lower z samples.  Additionally, the lensing data constrain the average concentration of the clusters to c_200c=5.6+3.7-1.8.


1611.04165
Reconstruction of halo power spectrum from redshift-space galaxy distribution: cylinder-grouping method and halo exclusion effect
Okumura, Takada, More, Masaki

The peculiar velocity field measured by RSD in galaxy surveys provides a unique probe of the growth of large-scale structure.  However, systematic effects arise when including satellite galaxies in the clustering analysis.  Since satellite galaxies tend to reside in massive haloes with a greater halo bias, the inclusion boosts the clustering power.  In addition, virial motions of the satellite galaxies cause a significant suppression of the clustering power due to nonlinear RSD effects.   Develop a novel method to recover the redshift-space power spectrum of haloes from the observed galaxy distribution by minimizing the contamination of satellite galaxies.  The cylinder grouping method (CGM) study effectively excludes satellite galaxies from a galaxy sample.  However, find that this technique produces apparent anisotropies in the reconstructed halo distribution over all the scales which mimic RSD.  On small scales, the apparent anisotropic clustering is caused by exclusion of haloes within the anisotropic cylinder used by the CGM.  On large scales, the misidentification of different haloes in the LSS, aligned along the LoS, into the same CGM group, causes the apparent anisotropic clustering via their cross-correlation with the CGM haloes.  Construct an empirical model for the CGM halo power spectrum, which includes correction terms derived using the CGM window function at small scales as well as the linear matter power spectrum multiplied by a simple anisotropic function at large scales.  Apply this model to a mock galaxy catalog at z=0.5, designed to resemble SDSS-III BOSS CMASS galaxies, and find that the model can predict both the monopole and quadrupole PS of the host haloes up to k<0.5 h/Mpc to within 5%.

Day 1185

Thursday.  Friday.  Monday.

1611.03554
Cross-correlation of weak lensing and gamma rays: implications for the nature of dark matter
Tröster, et al

Measure the cross-correlation between Fermi-LAT gamma-ray photons and over 1000 deg2 of WL data from CFHTLenS, RCSLenS, and KiDS.  Present the first measurement of tomographic WL cross-correlations and the first application of spectral binning to cross-correaltions between gamma rays and WL.  The measurements are performed using an angular power spectrum estimator while the covariance is estimated using an analytical prescription.  Verify the accuracy of the covariance estimate by comparing it to 2 internal covariance estimators.  Based on the non-detenction of a cross-correlation signal, derive constraints on weakly interacting massive particle (WIMP) DM.  Compute exclusion limits on the DM annihilation cross-section <sigma_ann v>, decay rate Gamma_dec, and particle mass m_DM.  Find that in the absence of a cross-correlation signal, tomography does not significantly improve the constraining power of the analysis.  Assuming a strong contribution to the gamma-ray flux due to small scale clustering of DM and accounting for known astrophysical sources of gamma rays, exclude the thermal relic cross-section for masses of m_DM<~ 20 GeV.


1611.03619
Excursion set peaks: the role of shear
Castorina, Paranjape, Hahn, Sheth

Recent analytical work on the modelling of DM abundances and clustering has demonstrated the advantages of combining the excursion set approach with peaks theory.  Extend these ideas and introduce a model of excursion set peaks that incorporates the role of initial tidal effects or shear in determining the gravitational collapse of dark haloes.  The model -- in which the critical density threshold for collapse depends on the tidal influences acting on protohaloes -- is well motivated from ellipsoidal collapse arguments and is also simple enough to be analytically tractable.  Show that the predictions of this model are in very good agreement with measurements of the halo mass function and traditional scale dependent halo bias in N-body sims across a wide range of masses and redshift.  The presence of shear in the collapse threshold means that halo bias is naturally predicted to be nonlocal, and that protohalo densities at fixed mass are naturally predicted to have Lognormal-like distributions.  Present the first direct estimate of Lagrangian nonlocal bias in N-body sims, finding broad agreement with the model predictions. Finally, the simplicity of the model (which has essentially a single free parameter) opens the door to building efficient and accurate non-universal fitting functions of halo abundances and bias for use in precision cosmology.

Day 1184

Wednesday.

1611.02657
Dissecting the evolution of dark matter sub haloes in the Bolshoi simulation
van den Bosch

Present a comprehensive analysis of the evolution of DM sub haloes in the Bolshoi sim.  Identify a complete set of 12 unique evolution channels by which sub haloes evolve in between sim outputs, and study their relative importance and demographics.  Show that instantaneous masses and maximum circular velocities of individual sub haloes are extremely noisy, despite the use of a sophisticated, phase-space-based halo finder.  Also show that sub haloes experience frequent penetrating encounters with other sub haloes (on average about one per dynamical time), and that sub haloes whose epicenter lies outside the virial radius of their host (the 'ejected' or 'backsplash' haloes) experience tidal forces that modify their orbits.  This results in an average fractional subhalo exchange rate among host haloes of roughly 0.01 per Gyr (at the present time).  In addition, show that there are 3 distinct disruption channels; one in which sub haloes drop below the mass resolution limit of the sim, one in which subhaloes merge with their host halo largely driven by dynamical friction, and one in which sub haloes abruptly disintegrate.  Estimate that roughly 80 percent of all subhalo disruption in the Bolshoi sim is numerical, rather than physical.  This over-merging is a serous road-block for the use of numerical sims to interpret small scale clustering, or for any other study that is sensitive to the detailed demographics of DM substructure.

Day 1183

Tuesday.

1611.02139
The cosmological principle is not in the sky
Park, Hyun, Noh, Hwang

The homogeneity of matter distribution at large scales is a central assumption in the standard cosmological model.  The case is testable though, thus no longer needs to be a principle, and indeed there have been claims that the distribution of galaxies is homogeneous at radius sales larger than 70 Mpc/h.  Here, perform a test for homogeneity using the SDSS LRG sample by counting galaxies within a specified volume with the radius scale varying up to 300 Mpc/h.  The analysis differs from the previous ones in that it is directly confronted with the LSS data with the definition of spatial homogeneity by comparing the fluctuations of individual number counts with allowed ranges of the random distribution with homogeneity.  The LRG sample shows much larger fluctuations of number counts than the random catalogs up to 300 Mpc/h scale, and even the average is located far outside the range allowed in the random distribution, which implies that the cosmological principle does not hold even at such large scales.  The same analysis of mock galaxies derived from the N-body simulation, however, suggests that the LRG sample is consistent with the current paradigm of cosmology.  Thus conclude that the cosmological principle is not in the observed sky and nor is demanded to be there by the standard cosmological world model.  This reveals the nature of the cosmological principle adopted in the modern cosmological paradigm, and opens new field of research in theoretical cosmology.

Day 1182

Friday.  Monday.

1611.01315
Measuring weak lensing correlations of Type Ia Supernovae
Scovacricchi, et al

Study the feasibility of detecting WL spatial correlations between SN Ia magnitudes with present (DES) and future (LSST) surveys.  Investigate the angular auto-correlation function of SN magnitudes (once the background cosmology has been subtracted) and cross-correlation with galaxy catalogues.  Examine both analytical and numerical predictions, the latter using simulated galaxy catalogues from the MICE Grand Challenge Simulation.  Predict that: unable to detect the SN auto-correlation in DES, while it should be detectable with the LSST SN deep fields (15,000 She on 70 deg2) at ~6 sigma level of confidence (assuming 0.15 magnitudes of intrinsic dispersion).  The SN- galaxy cross-correlation function will deliver much higher S/N, being detectable in both surveys with an integrated S/N of ~100 (up to 30 arcmin separations).  Predict joint constraints on the matter density parameter (Omega_m) and the clustering amplitude (sigma_8) by fitting the auto-correlation function of the mock LSST deep fields.  When assuming a Gaussian prior for Omega_m, can achieve a 25% measurement of sigma_8 from just these LSST SNe (assuming 0.15 mags of intrinsic dispersion).  These constraints will improve significantly if the intrinsic dispersion of SNe Ia can be reduced.


1611.01486
Cosmological constraints from the convergence 1-point probability distribution
Patton, Blazek, ... Huff, Melchior, et al

Examine the cosmo information available from the 1-pt PDF of the WL convergence field, utilizing fast L_PICOLA simulations and a Fisher analysis.  Find competitive constraints in the Omega_m-sigma_8 plain from the convergence PDF with 188 arcmin2 pixels compared to the cosmic shear power spectrum with an equivalent number of modes (ell<886). The convergence PDF also partially breaks the degeneracy cosmic shear exhibits in that parameter space.  A joint analysis of the convergence PDF and shear 2-pt function also reduces the impact of shape measurement systematics, to which the PDF is less susceptible, and improves the total figure of merit by a factor of 23, depending on the level of systematics.  Finally, present a correction factor necessary for calculating the unbiased Fisher information from finite differences using a limited number of cosmo sims.

Day 1181

Thursday.

1611.00366
On the level of cluster assembly bias in SDSS
Zu, Mandelbaum, Simet, Rozo, Rykoff

Recently, several studies have discovered a strong discrepancy between the large-scale clustering biases of two subsamples of galaxy clusters at the same halo mass, spilt by their average projected membership distances R_mem.  The level of this discrepancy significantly exceeds the maximum halo assembly bias signal predicted by LCDM.  In this study, explore whether some of the clustering bias differences could be caused by biases in R_mem due to projection effects from other systems along the LoS.  Throughly investigate the halo assembly bias of the photometrically-detected redMaPPer clusters in SDSS, by defining a new variant of the average membership distance estimator R_mcm-tilde that is more robust against projection effects in the cluster membership identification.    Using the angular mark correlation functions of clusters, show that the large-scale bias differences when splitting by R_mem can be largely attributed to such projection effects.  After splitting by R_mem-tilde, the anomalously large signal is reduced, giving a ratio of 1.02±0.14 between the two clustering biases as measured from WL.  Using a realistic mock cluster catalog, predict that the bias ratio between two R_mem-tilde-split subsamples should be <1.10, which is at least 60% weaker than the maximum halo assembly bias signal (1.24) when split by halo concentration.  Therefore, the results demonstrate that the level of halo assembly bias exhibited by redMaPPer clusters in SDSS is consistent with the LCDM prediction.  With a 10-fold increase in cluster numbers, deeper ongoing surveys will enable a more robust detection of halo assembly bias.  The findings also have important implications for how projection effects and their impact on cluster cosmology can be quantified in photometric cluster catalogs.


1611.00367
The galaxy end sequence
Eales, et al

A common assumption is that galaxies fall in 2 distinct regions on a plot of sSFR versus galaxy stellar mass: a star-forming galaxy main sequence (GMS) and a separate region of 'passive' or 'red and dead galaxies'.  Starting from a volume-limited sample of nearby galaxies designed to contain most of the stellar mass in this volume, and thus being a fair representation of the Universe at the end of 12 billion years of galaxy evolution, investigate the distribution of galaxies in this diagram today.  Show that galaxies follow a strongly curved extended GMS with a steep negative slope at high galaxy stellar masses.  There is a gradual change in the morphologies of the galaxies along this distribution, but there is no clear break between early-type and late-type galaxies.  Examining the other evidence that there are two distinct populations, argue that the 'red sequence' is the result of the colors of galaxies changing very little below a critical value of the sSFR, rather than implying a distinct populations of galaxies, and that Herschel observations, which show at least half of early-type galaxies contain a cool interstellar medium, also imply continuity between early-type and late-type galaxies.  This picture of a unitary population of galaxies requires more gradual evolutionary processes than the rapid quenching processes needed to explain two distinct populations.  Challenge theorists to reproduce the properties of the 'galaxy end sequence'.


1611.00752
Galaxy-galaxy lesning estimators and their covariance properties
Singh, Mandelbaum, Seljak, Solar, Vazquez, Gonzalez

Study the covariance properties of real space correlation function estimators -- primarily galaxy-shear correlations, or galaxy-galaxy lensing -- using SDSS data for both shear catalogs and lenses (specifically the BOSS LOWZ sample).  Using mock catalogs of lenses and sources, disentangle the various contributions to the covariance matrix and compare them wth a simple analytical model.  Show that not subtracting the lensing measurement around random points from the measurement around the lens sample is equivalent to performing the measurement using the density field instead of the over-density field, and that this leads to a significant error increase due to an additional term in the covariance.  Therefore, this subtraction should be performed regardless of its beneficial effects on systematics.  Comparing the error estimates from data and mocks for estimators that involve the overdensity, find that the errors are dominated by the shape noise and lens clustering, that empirically estimated covariances (jackknife and standard deviation across mocks) are consistent with theoretical estimates, and that both the connected parts of the 4-point function and the super-sample covariance can be neglected for the current levels of noise.  While the trade-off between different terms in the covariance depends on the survey configuration (area, source number density), the diagnostics that is used in this work should be useful for future works to test their empirically-determined covariances.

Day 1180

Wednesday.

1611.00008
Red nuggets grow inside-out: evidence from gravitational lensing
Oldham, et al

Present a new sample of SL systems where both the FG lenses and BG sources are early-type galaxies.  Using imaging from HST/ACS and Keck/NIRC2, model the surface brightness distributions and show that the sources form a distinct population of massive compact galaxies at 0.4<z<0.7, lying systematically below the size-mass relation of the global elliptical galaxy population at those redshifts.  These may therefore represent relics of high-z red nugget or their partly-evolved descendants.  Exploit the magnifying effect of lensing to investigate the structural properties, stellar masses and stellar populations of these objects with a view to understanding their evolution.  Model these objects parametrically and find that they generally require two Sersic components to properly describe their light profiles, with one more spheroidal component alongside a more envelope-like component, which is slightly more extended though still compact.  This is consistent with the hypothesis of the inside-out growth of these objects via minor mergers.  Also find that the sources can be characterized by red-to-blue colour gradients as a function of radius which are stronger at low z -- indicative of ongoing accretion -- but that their environments generally appear consistent with that of the general elliptical galaxy population, contrary to recent suggestions that these objects are predominantly associated with clusters.


1611.00036
The DESI Experiment Part I: science, targeting and survey design
DESI collaboration

DESI (Dark Energy Spectroscopic Instrument) is a Stage IV ground-based DE experiment that will study BAO and the growth of structure through z-space distortions with a wide-area galaxy and quasar redshift survey.  To trace the underlying DM distribution, spectroscopic target will be selected in 4 classes from imaging data.  It will measure luminous red galaxies up to z=1.0.  To probe the Universe out to even higher z, DESI will large bright [OII] emission line galaxies up to z=1.7.  Quasars will be targeted both as direct tracers of the underlying DM distribution and, at higher redshifts (2.1<z<3.5), for the Ly-alpha forest absorption features in their spectra, which will be used to trace the distribution of neutral hydrogen.  When moonlight prevents efficient observations of the fact targets of the baseline survey, DESI will conduct a magnitude-limited Bright Galaxy Survey comprising approximately 10 million galaxies with a median z~0.2.  In total, more than 30 million galaxy and quasar redshifts will be obtained to measure the BAO feature and determine the matter power spectrum, including redshift space distortions.

Day 1179

Monday.  Tuesday.

1610.09410
Testing gravity on large scales by combining weak lensing with galaxy clustering using CFHTLenS and BOSS CMASS
Alam, Miyatake, More, Ho, Mandelbaum

Measure a combination of gravitational lensing, galaxy clustering, and z-space distortions called E_G.  The quantity E_G probes both parts of metric potential and is insensitive to galaxy bias and sigma_8.  These properties make it an attractive statistic to test LCDM, GR and its alternate theories.  Combined CMASS DR11 with CFHTLenS and recent measurements of beta from RSD analysis, and find E_G(z=0.57)=0.42±0.056, a 13% measurement in agreement with the prediction of general relativity E_G(z=0.57)=0.396±0.011 using the Planck 2015 cosmo parameters.  Corrected the measurement for various observational and theoretical systematics.  The measurement is consistent with the first measurement of E_G using CMB lensing in place of galaxy lensing (Pullen+2015) at small scales, but shows 2.8 sigma tension when compared with their final results including large scales.  This analysis with future surveys will provide improved statistical error and better control over systematics to test GR and its alternate theories.


1610.09828
Testing PSF interpolation in weak lensing with real data
Lu, Zhang, et al

Reconstruction of the PSF is a critical process in WL measurement.  Develop a real-data based and galaxy-oriented pipeline to compare the performances of various PSF reconstruction schemes. Making use of a large amount of CFHTLenS data, the performances of 3 classes of interpolating schemes - polynomial, Kriging, and Shepard - are evaluated.  Find that polynomial interpolations with optimal orders and domains perform the best.  Quantify the effect of the residual PSF reconstruction error on shear recovery in terms of the multiplicative and additive biases, and their spatial correlation using the shear measurement method of Zhang+2015.  Find that the impact of PSF reconstruction uncertainty on the shear-shear correlation can be significantly reduced by cross correlating the shear estimators from different exposures.  It takes only 0.2 stars (SNR>100) per square arcmin on each exposure to reach the best performance of PSF interpolation, a requirement that is generally satisfied in the CFHTLenS data.