Day 1203

Thursday.

1612.06891
Theoretical challenges in galaxy formation
Naab, Ostriker

In this review, focus on one major challenge for galaxy formation theory: to understand the underlying physical processes that regulate the structure of the interstellar medium, star formation and the driving of galactic outflows.  This requires accurate physical models and numerical sims, which can precisely describe the multi-phase structure of the interstellar medium on the currently unresolved few hundred parsecs scales of large scale cosmo sims.  Such models ultimately require the full accounting for the dominant cooling and heating processes, the radiation and winds from massive stars and accreting BHs, an accurate treatment of SNe explosions as well as the non-thermal components of the ISM like B fields and cosmic rays.

Day 1202

Wednesday.

1612.06535
Weak gravitational lensing
Bartelmann, Maturi

According to the theory of GR, masses deflect light in a way similar to convex glass lenses.  This gravitational lensing effect is astigmatic, giving rise to image distortions.  These distortions allow to quantify cosmic structures statistically on a broad range of scales, and to map the spatial distribution of dark and visible matter.  Summarise the theory of WL and review applications to galaxies, galaxy clusters and large-scale structures in the Universe.

Day 1201

Monday.  Tuesday.

1612.05637
CMB lens sample covariance and consistency relations
Motloch, Hu, Benoit-Lévy

GL information from the 2 and higher point statistics of the CMB temperature and polarization fields are intrinsically correlated because they are lensed by the same realization of structure between last scattering and observation.  Using an analytic model for lens sample covariance, show that there is one mode, separately measurable in the lensed CMB PS and lensing reconstruction, that carries most of this correlation.  Once these measurements become lens sample variance dominated, this mode should provide a useful consistency check between the observable that is largely free of sampling and cosmo parameter errors.  Violations of consistency could indicate systematic errors in the data and lens reconstruction or new physics at last scattering, any of which could bias cosmo inferences and delensing for gravitational waves.  A second mode provides a weaker consistency check for a spatially flat universe.  The analysis isolates the additional information supplied by lensing in a model independent manner but is also useful for understanding and forecasting CMB cosmo parameter errors in the extended LCDM parameter space of DE, curvature and massive neutrinos.  Introduce and test a simple but accurate forecasting technique for this purpose that neither double counts lensing information nor neglects lensing in the observables.


1612.05647
The VIMOS public extragalactic redshift survey (VIPERS).  Gravity test from the combination of redshift-space distortions and galaxy-galaxy lensing at $0.5<z<1.2$
de la Torre, Jullo, Giocoli, et al

Carry out a joint analysis of z-space distortions and gg lensing, with the aim of measuring the growth rate of structure; this is a key quantity for understanding the nature of gravity on cosmo scales and late-time cosmic acceleration.  Make use of the final VIPERS z survey dataset, which maps a portion of the Universe at a z of z~0.8, and the lensing data from the CFHTLenS survey over the same area of the sky.  Build a consistent theoretical model that combines non-linear galaxy biasing and z-space distortion models, and confront it with observations.  The two probes are combined in a Bayesian maximum likelihood analysis to determine the growth rate of structure at 2 redshifts z-0.6 and 0.86.  Obtain measurement of f sigma8(0.6)=0.48±0.12 and f sigma8(0.886)=0.48±0.10.  The additional gg lensing constraint alleviates galaxy bias and sigma8 degeneracies, providing direct measurements of [f,sigma8](0.6) = [0.93±0.22, 0.52±0.06] and [f,sigma8](0.86) = [0.99±0.19, 0.48±0.04].  These measurements are statistically consistent with a Universe where the gravitational interactions can be described by GR, although they are not yet accurate enough to rule out some commonly considered alternatives.  Finally, as a complementary test, measure the gravitational slip parameter, E_G, for the first time at z>0.6.  Find values of E_G(0.6)=0.16±0.09 and E_G(0.86)=0.09±).07, when E_G is averaged over scales above 3 h^-1 Mpc.  Find that the E_G measurements exhibit slightly lower values than expected for standard relativistic gravity in a LCDM background, although the results are consistent with 1-2 sigma.

Day 1200

Friday.

1612.04825
Galaxy-galaxy lensing in EAGLE: comparison with data from 180 square degrees of the KiDS and GAMA surveys
Velliscig, Cacciato, Hoekstra, et al

Present predictions for the gg lensing profile from the EAGLE hydro cosmo sim at z=0.18, in the spatial range 0.02 < R/(Mpc/h) < 2, and for 5 log qui-spaced stellar mass bins in the range 10.3<log10(Mstar/Msun)<11.8.  Compare these excess surface density profiles to the observed signal from BG galaxies imaged by KiDS and spectroscopically confirmed FG galaxies from GAMA.  Exploiting the GAMA galaxy group catalogue, the profiles of central and satellite galaxies are computed separately for groups with at least 5 members to minimize contamination.  EAGLE predictions are in broad agreement with the observed profiles for both central and satellite galaxies, although the signal is underestimated at R~0.5-2 Mpc/h for the highest stellar mass bins.  When central and satellite galaxies are considered simultaneously, agreement is found only when the selection function of lens galaxies is taken into account in detail.  Specifically, in the case of GAMA galaxies, it is crucial to account for the variation of the fraction of satellite galaxies in bins of stellar mass induced by the flux-limited nature of the survey.  Report the inferred stellar-to-halo mass relation and find good agreement with recent published results.  Note how the precision of the gg lensing profiles in the sims holds the potential to constrain fine-grained aspects of the galaxy-dark matter connection.

Day 1199

Thursday.

1612.04664
Flat-sky Pseudo-Cls analysis for Weak gravitational lensing
Asgari, Taylor, Joachimi, Kitching

Investigate the use of estimators of WL power spectra based on a flat-sky implementation of the Pseudo-Cl (PCl) technique, where the masked shear field is transformed without regard for masked regions of sky.  This masking mixes power, and E-covergence and B-modes.  To study the accuracy of forward-modeling and full-sky power spectrum recovery, consider both large-area survey geometries, and small-scale masking due to stars and a checkerboard model for field-of-view gaps.  The power spectrum for the large-area survey geometry is sparsely-sampled and highly oscillatory, which makes modelling problematic.  Instead, derive an overall calibration for large-are mask bias using simulated fields.  The effects of small-area star masks can be accurately corrected for, while the checkerboard mask has oscillatory and spiky behavior which leads to percent biases.  Apodisation of the masked fields leads to increased biases and a loss of information.  Find that construction of an unbiased forward-modded of the raw PCls is possible, and recover the full-sky convergence power to within a few percent accuracy for both Gaussian and lognormal-distributed shear fields.  Propagating this through to cosmo parameters using a Fisher-Matrix formalism, find possible to make unbiased estimates of parameters for surveys up to 1200 deg2 with 30 galaxies per arcmin2, beyond which the percent biases become larger than the statistical accuracy.  This implies a flat-sky PCl analysis is accurate for current surveys but a Euclid-like survey will require higher accuracy.

Day 1198

Wednesday.  Thursday.

1612.04041
Cosmology with weak-lensing peak counts
Lin

WL causes distortions of galaxy images and probes massive structures on large scales, allowing to understand the late-time evolution of the Universe.  One way to extract the cosmo info from WL is to use peak statistics.  Peaks are tracers of massive haloes and therefore probe the mass function.  They retain non-Gaussian information and have already been shown as a promising tool to constrain cosmology.  In this work, develop a new model to predict WL peak counts.  The model generates fast sims based on halo sampling and selects peaks from the derived lensing maps.  This approach has 3 main advantages.  First, the model is very fast: only several seconds are required to perform a realization.  Second, including realistic conditions is straightforward.  Third, the model provides the full distribution information because of its stochasticity.  Show that the model agrees well with N-body sims.  Then, study the impacts of the cosmo-dependent covariance on constraints and explore different parameter inference methods.  A special focus is put on approximate Bayesian computation (ABC), an accept-reject sampler without the need to estimate the likelihood.  Show that ABC is able to yield robust constraints with much reduced time costs.  Several filtering techniques are studied to improve the extraction of multi scale information.  Finally, the new model is applied to the CFHTLenS, KiDS DR1/2, and DES SV data sets.  The preliminary results agree with the Planck constraints assuming LCDM.  Overall, this thesis forges an innovative tool for future WL surveys.  The manuscript provides a brief review on WL peak counts.


1612.04247
Impact of baryons and super-cluster environments on weak lensing measurements
Peters, Brown, Kay, Barnes

Use a combination of full hydrodynamic and DM only sims to investigate the effect that super-cluster environments and baryonic physics have on the matter power spectrum.  This is done by re-simulating a sample of super-cluster sub-volumes, identified in a large cosmologically representative DM only sim, along with a random control sample.  On large scales, find that the matter PS measured from the super-cluster sample has at least 2x as much power as that measured from the random sample, while on small scales the super-cluster sample has less power than the random sample.  The investigation of the effect of baryons physics on the matter PS is found to be in agreement with previous studies.  However, find that the effect of environment on the matter power spectrum is dominant over the effect of baryons.  In addition, investigate the effect of targeting a cosmologically non-representative, super-cluster region of the sky in the WL shear PS.  Do this by generating shear and convergence maps using a LoS integration technique, which intercepts the random and supercluster sub-volumes.  Find the convergence power spectrum measured from the super-cluster sample has a larger amplitude than that measured from the random sample at all scales, and by more than a factor of 2 for ell<1e3.  Frame the results within the context of the Super-CLusterAssisted Shear Survey (Super-CLASS), which aims to measure the cosmic shear signal in the radio band by targeting a region of the sky that contains 5 Abell clusters.  Assuming the Super-CLASS survey will have a source density of 1.5 galaxies/arcmin2, forecast a detection significance of 2.7±1.5, which indicates that the Super-CLASS project will likely make a cosmic shear detection with radio data alone.


1612.04360
Large-scale assembly bias of dark matter haloes
Lazeyras, Musso, Schmidt

Present precise measurements of the assembly bias of DM haloes, i.e. the dependent of halo bias on other properties than the mass, using curved "separate universe" N-body sims which effectively incorporate an infinite-wavelength matter overdnesity into the BG density.  This method measure the LIMD bias parameters b_n in the large-scale limit.  Focus on the dependence of the first two Eulerian biases b1 and b2 on 4 halo properties: the concentration, spin, mass accretion rate, and ellipticity.  Quantitatively compare the results with previous works in which assembly bias was measured on fairly small scales.  Despite this difference, the findings are in good agreement with previous results.  Also look at the joint dependence of bias on 2 halo properties in addition to the mass.  Finally, using the excursion set peaks model, attempt to shed new insights on how assembly bias arises in this analytical model. 

Day 1197

Friday.  Monday.  Tuesday.

1612.03034
First test of Verlinde's theory of emergent gravity using weak gravitational lensing measurements
Brouwer, et al

Verlinde (2016) proposed that the observed excess gravity in galaxies and clusters is the consequence of Emergent Gravity (EG).  In this theory the standard gravitational laws are modified on galactic and larger scales due to the displacement of dark energy by baryonic matter.  EG gives an estimate of the excess gravity (described as an apparent DM density) in terms of the baryonic mass distribution and the Hubble parameter.  In this work, present the first test of EG using WL, within the regime of validity of the current model.  Although there is no direct description of lensing and cosmology in EG yet, can make a reasonable estimate of the expected lensing signal of low redshift galaxies by assuming a BG LCDM cosmology.  Measure the (apparent) average surface mass density profiles of 33,613 isolated central galaxies, and compare them to those predicted by EG based on the galaxies' baryonic masses.  To this end, employ the ~180 sq.deg. overlap of KiDS with the spectroscopic GAMA survey.  Find that the prediction from EG, despite requiring no free parameters, is in good agreement with the observed gglensing profiles in 4 different stellar mass bins.  Although this performance is remarkable, this study is only a first step.  Further advancements on both the theoretical framework and observational tests of EG are needed before it can be considered a fully developed and solidly tested theory.


1612.03121
Integrated cosmological probes: extended analysis
Nicola, Refregier, Amara

Recent progress in cosmology has relied on combining different cosmo probes.  In earlier work, implemented an integrated approach to cosmology where the probes are combined into a common framework at the map level.  This has the advantage of taking full account of the correlations between the different probes, to provide a stringent test of systematics and the validity of the cosmo model.  Extend this analysis to include not only CMB temperature, galaxy clustering, WL from SDSS but also CMB lensing, WL from DES SV, Type Ia SNe and H0 measurements.  This yields 12 auto and cross power spectra as well as BG probes.  Furthermore, extend the treatment of systematic uncertainties.  For LCDM, find results that are consistent with earlier work.  Given the enlarged data set and systematics treatment, this confirms the robustness of the analysis and results.  Furthermore, find that the best-fit cosmo model gives a good fit to the data considered with no signs of tensions within the analysis.  Also find the constraints to be consistent with this found by WMAP9, SPT and ACT and the KiDS WL survey.  Comparing with the Planck Collaboration results, see a broad agreement, but there are indications of a tension from the marginalized constraints in most pairs of cosmological parameters.  Since the analysis includes CMB temperature Planck data at 10<ell<610, the tension appears to arise between the Planck high-ell and the other measurements.  Furthermore, find the constraints on the probe calibration parameters to be in agreement with expectations, showing that the datasets are mutually consistent.  In particular, this yields a confirmation of the amplitude calibration of the WL measurements from SDSS, DES SV and Planck CMB lensing from the integrated analysis.

Day 1196

Thursday.

1612.02173
A cooperative approach among methods for photometric redshifts estimation: an application to KiDS data
Cavuoti, et al

Using a KiDS subset of ~25,000 galaxies with measured spec-z's, derive photo-z's using i) 3 different empirical methods based on supervised machine learning, ii) the BPZ model and iii) classical SED template fitting procedure (Le Phare).  Confirm that, in the regions of photometric parameter space properly sampled by the spectroscopic templates, machine learning methods provide better redshift estimates, with a lower scatter and a smaller fraction of outliers.  SED fitting techniques, however, provide useful information on the galaxy spectral type which can be effectively used to constrain systematic errors and to better characterize potential catastrophic outliers.  Such classification is then used to specialize the training of regression machine learning models, by demonstrating that a hybrid approach, involving SED fitting and machine learning in a single collaborative framework, can be effectively used to improve the accuracy of photo-z estimates. 


1612.02264
Cosmological constraints with weak lensing peak counts and second-order statistics in a large-field survey
Peel, et al

Peak statistics in weak lensing maps access the non-Gaussian information contained in the LS distribution of matter in the Universe.  They are therefore a promising complement to 2pt and higher-order statistics to constrain the cosmological models.  To prepare for the high-precision data of next-generation surveys, assess the constraining power of peak counts in a simulated Euclid-like survey on the cosmo parameters Omega_m, sigma_8, and w_0.  In particular, study how the Camelus model -- a fast stochastic algorithm for predicting peaks -- can be applied to such large surveys.  Measure the peak count abundance in a mock shear catalogue of ~5k sq. deg. using a multi scale mass map filtering technique.  Then constrain the parameters of the mock survey using Camelus combined with approximate Bayesian computation (ABC).  Find that peak statistic yield a tight but significantly biased constraint in the sigma_8-Omega_m plane, indicating the need to better understand and control the model's systematics.  Calibrate the model to remove the bias and compare results to those from the 2PCF measured on the same field.  In this case, find the derived parameter Sigma_8=sigma_8(Omega_m/0.27)^alpha = 0.76±0.03 with alpha=0.65 for peaks, while for 2PCF the values is SIgma_8=0.76±0.02 with alpha=0.70.  Therefore see comparable constraining power between the 2 probes, and the offset of their sigma_8-Omega_m degeneracy directions suggests that a combined analysis would yield tighter constraints than either measure alone.  As expected, w_0 cannot be well constrained without a tomographic analysis, but its degeneracy directions with the other two varied parameters are still clear for both peaks and 2PCF.

Day 1195

Wednesday.

1612.01533
Estimating the weak-lensing rotation signal in radio cosmic shear surveys
Thomas, Whittaker, Camera, Brown

The WL distortion tensor contains two other effects in addition to the two components of shear: the convergence and rotation.  The rotation mode is not measurable using the standard cosmic shear estimators based on galaxy shapes, as there is no information on the original shapes of the images before they were lensed.  Due to this, no estimator has been proposed for the rotation mode in cosmo WL surveys, and the rotation mode has never been constrained.  Here, derive an estimator for his quantity, which is based on the use of radio polarization measurements of the intrinsic position angles of galaxies.  The rotation mode can be sourced by a physics beyond LCDM, and also offers the chance to perform consistency checks of LCDM and of WL surveys themselves.  Present simulations of this estimator and show that, for the pedagogical example of cosmic string spectra, this estimator could detect a signal that is consistent with the constraints from Planck.  Examine the connection between the rotation mode and the shear B-modes and thus how this estimator could help control systematics in future radio WL surveys.

Day 1194

Friday.  Monday.  Tuesday.

1612.00752
Non-linear shrinkage estimation of large-scale structure covariance
Joachimi

In many astrophysical settings covariance matrices of large datasets have to be determined empirically from a finite number of mock realizations.  The resulting noise degrades inference and precludes it completely if there are fewer realizations than data points.  This work applies a recently proposed non-linear shrinkage estimator of covariance to a realistic example from large-scale structure cosmology.  After optimizing its performance for the usage in likelihood expressions, the shrinkage estimator yields subdominant bias and variance comparable to that of the standard estimator with a factor ~50 less realizations.  This is achieved without any prior information on the properties of the data or the structure of the covariance matrix, at negligible computational cost.


1512.00770
Unequal-time correlates for cosmology
Kitching, Heavens

Measurements of the power spectrum from large-scale structure surveys have to date assumed an equal-time approximation, where the full cross-correlation power spectrum of the matter density field evaluated at different times (or distances) has been approximated either by the power spectrum at fixed time, or in an improved fashion, by a geometric mean P(k; r1, r2) = [P(k;r1)P(k;r2)]^1/2.  In this paper, investigate the expected impact of the geometric mean ansatz, and present an application in assessing the impact on weak gravitational lensing cosmological parameter inference, using an perturbative unequal-time correlation.  As one might expect, find that the impact of this assumption is greatest at large separations in redshift Delta z > 0.3 where the change in the amplitude of the matter power spectrum can be as much as 10 percent for k>5h/Mpc.  However, of more concern is that the corrections for small separations, where the clustering is not close to zero, may not be negligibly small.  In particular, find that for a Euclid- or LSST-like weak lensing experiment the assumption of dual-time correlators may result in biased predictions of the cosmic shear power spectrum, and that the impact is strongly dependent on the amplitude of the intrinsic alignment signal.  To compute uneuqal-time correlations to sufficient accuracy will require advances in either perturbation theory to high k-modes, or extensive use of simulations.


1612.00839
The 2-degree field lensing survey: photometric redshifts from a large new training sample to r<19.5
Wolf, et al

Present a new training set for estimating empirical photometric redshifts of galaxies, which was created as part of the 2dFLenS project.  This training set is located in a 700 sq deg area of the KiDS South field and is randomly selected and nearly complete at r<19.5.  Investigate the photometric z performance obtained with ugriz photometry from VST-ATLAS and W1/W2 from WISE, based on several empirical and template methods.  The best redshift errors are obtained with kernel-density estimation, as are the lowest biases, which are consistent with zero within statistical noise.  The 68th percentiles of the redshift scatter for magnitude-limited samples at r<(15.5, 17.5, 19.5) are (0.014, 0.017, 0.028).  In this magnitude range, there are no known ambiguities in the color-redshift map, consistent with a small rate of redshift outliers.  In the fainter regime, the KDE method produces p(z) estimates per galaxy that represent unbiased and accurate redshift frequency expectations.  The p(z) sum over any subsample is consistent with the true redshift frequency plus Poisson noise.  Further improvements in redshift precision at r<20 would mostly be expected from filter sets with narrower passbands to increase the sensitivity of course to small changes in redshift.


1612.00847
Data-driven, interpretable photometric redshifts trained on heterogeneous and unrepresentative data
Leistedt, Hogg

Present a new method for inferring photo-z in deep galaxy and quasar surveys, based on a data driven model of latent SEDs and a physical model of photometric fluxes as a function of redshift.  This conceptually novel approach combines the advantages of both machine-learning and template-fitting methods by building template SEDs directly from the training data.  This is made computationally tractable with gaussian Processes operating in flux-z space, encoding the physics of redshift and the projection of galaxy SEDs onto photometric band passes.  This method alleviates the need of acquiring representative training data or constructing detailed galaxy SED models; it requires only that the photometric band passes and calibrations be known or have parameterized unknowns.  The training data can consist of a combination of spectroscopic and deep many-band photometric data, which do not need to entirely spatially overlap with the target survey of interest or even involve the same photometric bands.  Showase the method on the i-magnitude-selected, spectroscopically-confirmed galaxies in the COSMOS field.  The model is trained on the deepest bands (from SUBARU and HST) and photo-zs are derived using the shallower SDSS optical bands only.  Demonstrate that accurate z point estimates and probability distributions are obtained despite the training and target sets having very different z distributions, noise properties, and even photometric bands.  The model can also be used to predict missing photometric fluxes, or to simulated populations of galaxies with realistic fluxes and z, for example.  This method opens a new era in which photo-z for large photometric surveys are derived using a flexible yet physical model of the data trained on all available surveys (spectroscopic and photometric).


1612.00852
On the validity of the Born approximation for beyond-Gaussian weak lensing observables
Petri, Haiman, May

Accurate forward modeling of WL observables from cosmo parameters is necessary for upcoming galaxy surveys.  Because WL probes structures in the non-linear regime, analytical forward modeling is very challenging, if not impossible.  Numerical sims of WL features rely on ray-tracing through the outputs of N-body sims, which requires knowledge of the gravitational potential and accurate solvers for light ray trajectories.  A less accurate procedure, based on the Born approximation, only requires knowledge of the density field, and can be implemented more efficiently and at a lower computational cost.  In this work, use sims to show that deviations of the Born-approximated convergence power spectrum, skewness and kurtosis from their fully ray-traced counterparts are consistent with the smallest non-trivial post-Born corrections (so-called geodesic and lens-lens terms).  Find, however, that the perturbative approach for the geodesic correction breaks down at higher orders.  Also find that cosmo parameter biases induced by the Born approximation are negligible even for an LSST-like analyses.  Using the LensTools software suite, show that the Born approximation saves a factor of 4 in computing time with respect to the full ray-tracing in reconstructing the convergence.

Day 1193

Thursday.

1611.10326
Weak lensing magnification in the Dark Energy Survey Science Verification Data
Garcia-Fernandez, et al

In this paper the effect of WL magnification on galaxy number counts is studied by cross-correlating the positions of 2 galaxy samples, separated by redshift, using data from the DES SV data set.  The analysis is carried out for 2 photometrically-selected galaxy samples, with mean photometric redshifts in the 0.2<z<0.4 and 0.7<z<1.0 ranges, in the riz bands.  A signal is detected with a 3.5 sigma significance level in each of the bands tested, and is compatible with the magnification predicted by the LCDM model.  After an extensive analysis, it cannot be attributed to any known systematic effect.  The detection of the magnification signal is robust to estimated uncertainties in the outlier rate of the photometric redshifts, but this will be an important issue for use of photometric redshifts in magnification measurements from larger samples.  In addition to the detection of the magnification signal, a method to select the sample with the maximum signal-to-noise is proposed and validated with data.

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.