Day 1105

Wednesday.  Thursday.  Friday.  Monday.


1605.09398
The effect of lensing magnification on the apparent distribution of black hole mergers
Dai, Venumadhav, Sigurdson

The recent detection of GWs indicates that stellar-mass BH binaries are likely to be a key population of sources for forthcoming observations.  With future upgrades, ground-based detectors could detect merging BH binaries out to cosmo distances.  GW bursts from high z (z>1) can be strongly magnified by GL due to intervening galaxies along the LoS.  In the absence of EM counterparts, the mergers' intrinsic mass scale and redshift are degenerate with the unknown magnification factor mu.  Hence, strongly magnified low-mass mergers from high-z appear as higher-mass mergers from lower redshifts.  Assess the impact of this degeneracy on the mass-z distribution of observable events for generic models for binary BH formation from normal stellar evolution,  Pop III star remnants, or a primordial BH population.  Find that strong magnification (mu>3) generally creates a heavy tail of apparently massive mergers in the event distribution from a given detector.  For LIGO and its future upgrades, this tail may dominate the population of intrinsically massive, but unlicensed mergers in binary BH formation models involving normal stellar evolution or primordial BHs.  Modeling the statistics of lensing magnification can help account for this magnification bias when testing astrophysical scenarios of BH binary formation and evolution.


1606.00233
Jackknife resampling technique on mocks: an alternative method for covariance matrix estimation
Escoffier, et al

Present a fast and robust alternative method to compute covariance matrix in case of cosmo studies.  The method is based on the jackknife resampling applied on simulation from catalogues.  Using a set of 600 BOSS DR11 mock catalogues as a reference, find that the JK technique gives a similar galaxy cluserig covariance matrix estimate by requiring a smaller number of mocks.  A comparison of convergence rates show that ~7 times fewer simulations are needed to get a similar accuracy on variance.  Expect this technique to be applied in any analysis where the number of available N-body simulations is low.


1606.00458
Arrival time differences between gravitational waves and electromagnetic signals due to gravitational lensing
Takahashi

Demonstrate that GR predicts arrival time differences between GW and EM signals caused by the wave effects in gravitational lensing.  The GW signals can arrive earlier the the EM signals in some cases if the GW/EM signals have passed through a lens, even if both signals were emitted simultaneously by a source.  GW wavelengths are much larger than EM wavelengths; therefore, the propagation of the GWs does not follow the laws of geometrical optics, including the Shapiro time delay, if the lens mass is less than approximately 1e5 Msun(f/Hz)^(-1), where f is the GW frequency.  The arrival time difference can reach ~0.1 s (f/Hz)^(-1); therefore, it is more prominent for lower GW frequencies.  Gravitational lensing imprints a characteristic modulation on a chirp waveform; therefore, we can deduce whether a measured arrival time lag arises from intrinsic source properties or gravitational lensing.  Determination of arrival time differences would be extremely useful in multi messenger observations and tests of GR.

Day 1104

Monday.  Tuesday.

1605.08472
Strong lensing in the inner halo of galaxy clusters
Saez, et al

Probabilities for finding gravitational arcs in galaxy clusters are calculated and compared for two DM halo profiles: NFW and non-singular isothermal sphere (NSIS).  KS test allows establishment of limits on the values of the concentration parameter for the NFW profile (c_Delta) and the core radius for the NSIS profile (rc), which are related to the lowest cluster redshift (z_cut) where strong arcs can be observed.  For NFW DM profiles, infer cluster haloes with concentrations that are consistent to those predicted by LCDM simulations.  As for NSIS DM profiles, find only upper limits for the clusters core radii and thus do not rule out a purely SIS model.  For alternative mass profiles the formulation provides constraints through z_cut on the parameters that control the concentration of mass in the inner region of the clusters haloes.  Find that z_cut is expected to lie in the 0.0-0.2 redshift, highlighting the need to include very low-z clusters in samples to study the cluster mass profiles.


1605.08784
Precise strong lensing mass profile of the CLASH galaxy cluster MACS 2129
Monna, et al

Present a detailed SL mass reconstruction of the core of the galaxy cluster MACS 2129 at z_cl=0.589, obtained by combining high-resolution HST photometry from the CLASH survey with new spectra observations from CLASH-VLT survey.  A BG bright red passive galaxy at z_sp=1.36, sextuply lensed in the cluster core, has four radial lensed images located over the 3 central cluster members.  Further 19 BG lensed galaxies are spectroscopically confirmed by the VLT survey, including 3 additional multiple systems.  A total of 27 multiple images are used in the lensing analysis.  This allows to trace with high precision the total mass profile of the cluster in its very inner region (R<100 kpc).  The final lensing mass model reproduces the multiple images systems identified in the cluster core with high accuracy of 0.4".  This translates in an high precision mass reconstruction of MACS 2129, which is constrained at level of 3%.  The cluster has Einstein radius theta_E=(15±2)", for a source at z_s=1.36 and a projected total mass of M_tot(<theta_E) = (3.4±0.1)e13 Msun within such radius.  Together with the cluster mass profile, provide here also the complete spectroscopic dataset for the cluster members and lensed images measured with VLT/VIMOS within the CLASH-VLT survey.


** 1605.09056
Cosmic shear as a probe of galaxy formation physics
Foreman, Becker, Wechsler

Evaluate the potential for current and future cosmic shear measurements from large galaxy surveys to constrain the impact of baryonic physics on the matter power spectrum.  Do so by using a model-independent parameterization that describes deviations for the patter power spectrum from the DM-only case as a set of principal components that are localized in wavenumber and redshift.  Perform forecasts for a variety of current and future datasets, and find that at least ~90% of the constraining power of these datasets is contained in no more than none principal components.  The constraining power of different surveys can be quantified using a figure of merit defined relative to currently available surveys.  With this metric, find that the final DES dataset and the Hyper Supreme Cam survey will be roughly an order of magnitude more powerful than existing dat in constraining baryonic effects.  Upcoming stage IV surveys (LSST, Euclid, and WFIRST) will improve upon this by a further factor for a few.  Show that his conclusion is robust to marginalization over several key systematics at small (sub-arcminute) scales.  If these systematics can be sufficiently controlled, cosmic shear measurements from DES and other future surveys have the potential to provide a very clean probe of galaxy formation and to strongly constrain a wide range of predictions from modern hydrodynamical simulations.


*** 1605.09130
Cosmic shear bias and calibration in cosmic shear studies
Taylor, Kitching

With the advent of large-scale weak lensing surveys there is a need to understand how realistic, scale-dependent systematics bias cosmic shear and DE measurements, and how they can be removed.  Describe how spatial variations in the amplitude and orientation of realistic image distortions convolve with the measured shear field, mixing the even-parity convergence and odd-parity modes, and bias the shear power spectrum.  Many of these biases can be removed by calibraion to external data, the survey itself, or by modeling in simulations.  The uncertainty in the calibration must be marginalized over; calculate how this propagates in to parameter estimation, degrading the DE FoM.  Find that noise-like biases affect DE measurements the most, while spikes in the bias power have the least impact, reflecting their correlation with the effect of cosmological parameters.  Argue that in order to remove systematic biases in cosmic shear surveys and maintain statistical power, effort should be put into improving the accuracy of the bias calibration rather than minimizing the size of the bias.  In general, this appears to be a weaker condition for bias removal.  Also investigate how to minimize the size of the calibration set for a fixed reduction in the FoM.  These results can be used to model the effect of biases and calibration on a cosmic shear survey accurately, assess their impact on the measurement of modified gravity and DE models, and to optimize surveys and calibration requirements.

Day 1103

Friday.

1605.08341
Observational selection biases in time-delay strong lensing and their impact on cosmography
Collett, Cunnington

Inferring cosmo parameters from time-delay SL requires a significant investment of telescope time; it is therefore tempting to focus on the systems with the brightest sources, the highest image multiplicities and the widest image separations.  Investigate if this selection bias can influence the properties of the lenses studied and the cosmo parameters that are inferred.  Using a population of lenses with ellipsoidal power law density profiles, build a sample of double and quadruple image systems.  Assuming reasonable thresholds on image separation and flux, based on current lens monitoring campaigns, find that the typical density profile slopes of montorable lenses are significantly shallower than they put ensemble.  From a sample of quadruple image lenses, find that this selection function can introduce a 3.5% bias on the inferred time-delay distances if the ensemble of deflector properties is used as a prior for a cosmographical analysis.  This bias remains at the 2.4% level when high resolution imaging of the quasar host is used to precisely infer the density profiles of individual lenses.  Also investigate if the lines-of-sight for monitorable SLs are biased.  After adding external convergence, kappa, and shear to the lens population find that the expectation value for kappa is increased by 0.004 and 0.009 for doubles and quads respectively.  Kappa is degenerate with the value of H0 inferred from time delays; fortunately the shift in kappa only induces 0.9 (0.4) percent bias on H0 for quads (doubles).  Conclude that whilst the properties of typical quasar lenses and their lines-of-sight do deviate from the global population, the total magnitude of this effect is likely a subdominant effect for current analyses, but has the potential to be a major systematic for samples of ~25 or more lenses.


1605.08428
Matter in the beam: weak lensing, substructures and the temperature of dark matter
Mahdi, Elahi, Lewis, Power

Compare WL maps of CDM clusters to those in a WDM model corresponding to a thermally produced 0.5 keV DM particle.  Analysis clearly shows that the WL magnification, convergence and shear distributions can be used to distinguish between CDM and WDM models.  WDM models increase the probability of weak magnifications, with the differences being significant to >5 sigma, while leaving no significant imprint on the shear distribution.  WDM clusters analyses in this work are more homogeneous than CDM ones, and the fractional decrease in the amount of material in haloes is proportional to the average increase in the magnification.  This difference arises from matter that would be bound in compact haloes in CDM being smoothly distributed over much larger volumes at lower densities in WDM.  Moreover, the signature does not solely lie in the probability distribution function but in the full spatial distribution of the convergence field.

Day 1102

Thursday.

1605.07620
II. Apples to apples $A^2$: cluster selection functions for next-generation surveys
Ascaso, Mei, Bartlett, Benítez

Present the cluster selection function for 3 of the largest next-generation stage-IV surveys in the optical in IR: Euclid-Optimistic, Euclid-Pessimistic and the LSST.  To simulate test surveys, use the realistic mock catalogues introduced in the first paper of this series.  Detected galaxy clusters using Bayesian Cluster Finder (BCF) in the mock catalogues.  Then model and calibrate the total cluster stellar mass observable-theoretical mass (M*_CL-M_h) relation using a power law model, including a possible redshift evolution term.  Find a moderate scatter of sigma_{M*_CL | M_h} of 0.124, 0.135 and 0.136 dex for the 3 cases, respectively, comparable to other work over more limited ranges and redshift.  Moreover, the 3 datasets are consistent with negligible evolution with redshift, in agreement with observational and simulation results in the literature.  Find that Euclid-Optimistic will be able to detect clusters with >80% completeness and purity down to 8e13 Msun up to z<1.  At higher redshifts, the same completeness and purity are obtained with the larger mass threshold of 2e14 Msun up to z=2.  The Euclid-Pessimistic selection function has a similar shape with ~10% higher mass limit.  LSST shows ~5% higher mass limit than Euclid-Optimistic up to z<0.7 and increases afterwards, reaching values of 2e14 Msun at z=1.4.  Similar selection functions with only 80% completeness threshold have been also computed.  The complementarity of these results with selection functions for surveys in other bands is discussed.


1605.07621
Lens models under the microscope: comparison of Hubble Frontier Field Cluster Magnification Maps
Price, Williams, Liesenborgs, Coe, Rodney

Using the power of gravitational lensing magnification by massive galaxy clusters, the HFF provide views of 6 patches of the high-z universe.  The combination of deep Hubble imaging and exceptional lensing strength has revealed the greatest numbers of multiply-imaged galaxies available to constrain models of cluster mass distributions.  However, even with O(100) images per cluster, the uncertainties associated with the reconstructions are not negligible.  The goal of this paper is to present a quantitative and visual impression of the diversity of model magnification predictions.  Examine 7 and 9 mass models of Abell 2744 and MCS J0416, respectively, submitted to the Mikulski Archive for Space Telescopes for public distribution in September 2015.  The dispersion between model predictions increases from 20% at common low magnifications (mu~2) to 70% at rare high magnifications (mu~40).  MACS J0416 exhibits smaller dispersions than Abell 2744 for 2<mu<10.  Show that magnification map based on different lens inversion techniques typically differ from each other by more than their quoted statistical errors.  This suggests that some models probably underestimate the true uncertainties, which are primary due to various lensing degeneracies.  Though the exact mass sheet degeneracy is broken, its approximate counterpart is not broken at least in Abell 2744.  Other, local degeneracies are also present in both clusters.  The comparison of models in this paper is complementary to the exercise of comparing reconstructions of known synthetic mass distributions.  By focusing here on a comparison of actual observed clusters, we can identify the clusters that are best constrained, and therefore provide the clearest view of the distant Universe.

Day 1101

Wednesday.

1605.07548
Constraining the halo mass function with observations
Castro, Marra, Quartin

Ask how well observations can constrain directly the HMF.  The observables considered are galaxy cluster number counts, galaxy closer PS and lensing of type Ia supernovae.  Results show that DES is capable of putting the first meaningful constraints, while both Euclid and J-PAS can give constraints on the HMF parameters which are comparable to the ones from state-of-the-art simulations.  Also find that an independent measurement of cluster masses is even more important for measuring the HMF than for constraining the cosmological parameters, and can vastly improve the determination of the halo mass function.  Measuring the HMF could thus be used to cross-check simulations and their implementation of baryon physics.  It could even, if deviations cannot be accounted for, hint at new physics.

Day 1100

Tuesday.

1605.06591
Average spatial distribution of cosmic rays behind the interplanetary shock -Global Muon DetectorNetwork observations-
Kozai, et al

Analyze the galactic cosmic ray (GCR) density and its spatial gradient in Forbush Decreases (FDs) observed with the Global Muon Detector Network (GMDN) and neutron monitors (NMs). By superposition the GCR density and density gradient observed in FDs following 45 interplanetary shocks (IP-shocks), each associated with an identified eruption of the sun, infer the average spatial distribution of GCRs behind IP-shocks.  Find two distinct modulations of GCR density in FDs, one in the magnetic sheath and the other in the coronal mass ejection (CME) behind the sheath.  The density modulation in the sheath is dominant in the western flank of the shock, while the modulation in the CME ejecta sounds ou in the eastern flank.  This east-west asymmetry is more prominent in GMDN data responding to ~60 GV GCRs than in NM data responding to ~10 GV GCRs, because the softer rigidity spectrum of the modulation n the CME ejecta than in the sheath.  The GSE-y component of the density gradient, G_y shows a negative (positive) enhancement in FDs caused by the eastern (western) eruptions, who G_z shows a negative (positive) enhancement in FDs by the northern (southern) eruptions.  This implies the GCR density minimum being located behind the central flank of IP-shock and propagating radially outward from location of the solar eruption.  Also confirmed the average G_z changing its sign above and below the heliospheric current sheet, in accord with the prediction of the drift model for the large-scale GCR transport in the heliosphere.

Day 1099

Friday.  Monday.

1605.06334
The impact of JWST broad-band filter choice on photometric redshift estimation
Bisigello, et al

The determination of galaxy redshifts in JWST's blank-field surveys will mostly rely on photometric estmiantes, based on the data provided by JWST's NIRCam at 0.6-5.0 um and Mid Infrared instrument (MIRI) at lambda>5.0 um.  In this work, analyse the impact of choosing different combinations of NIRCam and MIRI broad-band filters (F070W to F770W), as well as having ancillary data at lambda<0.6 um, on the derived photo-z of a total of 5921 real and simulated galaxies, with known input redshifts z=0-10.  Find that observations at lambda<0.6um are necessary to control the contamination of high-z samples by low-z interlopers.  Adding MIRI (F560W and F770W) photometry to the NIRCam data mitigates the absence of ancillary observations at lambda<0.6um and improves the redshift estimation, both reducing the fraction of high-z contaminants and preventing the leakage of high-z sources towards low z.  At z=7-10, accurate zphot can be obtained with the NIRCam broad bands alone when S/N>=10, but the zphot quality significantly degrades at S/N<=5.  Adding MIRI photometry with one magnitude brighter depth than the NIRCam depth allows for a redshift recovery of 83-99%, depending on SED type, and its effect is particularly noteworthy for galaxies with nebular emission.  The vast majority of NIRCam galaxies with [F150W]=29 AB mag at z=7-10 will be detected with MIRI at [F560W,F770W]<28 mag if these sources are at least mildly evolved or have spectra with emission lines boosting the mid-infrared fluxes.

Day 1098

Thursday.

1605.05333
Time delay cosmography
Treu, Marshall

Gravitational time delays, observed in strong lens systems where the variable background sources is multiply-imaged by a massive galaxy in the foreground, provide direct measurements of cosmo distance that are very complementary to other cosmographic probes.  The success of the technique depends on the availability and size of a suitable sample of lensed quasars or supernovae, precise measurements of the time delays, accurate modeling of the gravitational potential of the main deflector, and the ability to characterize the distribution of mass along the LoS to the source.  Review the progress made during the last 15 years, doing which the first competitive cosmological inferences with time delays were made, and look ahead to the potential of significantly larger lens samples in the near future.


1605.05337
Measurement of a cosmographic distance ratio with galaxy and CMB lensing
Miyatake, et al

Measure the GL shear signal around DM haloes hosting CMASS galaxies using light sources at z~1 (background galaxies) and at the surface of last scattering at z~1100 (the CMB).  The galaxy shear measurement uses data from the CFHTLenS survey, and the microwave background shear measurement uses data from the Planck satellite.  The ratio of shears from these cross-correlations provides a purely geometric distance measurement across the longest possible cosmological lever arm.  This is because the matter distribution around the haloes, including uncertainties in galaxy bias and systematic errors such as miscentering, cancels in the ratio exactly.  Measure this distance ratio in 3 different z slices of the CMASS sample, and combine them to obtain a 15% measurement of the distance ratio, r=0.344±0.052 at an effective redshift of z=0.54.  This is consistent with the predicted ratio from the Planck best-fit LCDM cosmology of r=0.410.


1605.05501
Clustering-based redshift estimation: application to VIPERS/CHFTLS
Scooter, Mellier, et al

Explore the accuracy of the clustering-based redshift estimation proposed by Menard+2013 when applied to VIPERS and CFHTLS real data.  This method enables reconstruction z distributions from measurement of the angular clustering of objects using a set of secure spectroscopic redshifts.  Use state of the art spectroscopic measurements with iAB<22.5 from VIPERS as reference population to infer the z distribution of galaxies from the CFHTLS T0007 release.  VIPERS provides a nearly representative sample to the fox limit iAB<22.5 at z>0.5 which allows to test the accuracy of the clustering-based redshift distributions.  Show that this method enables reproduction of the true mean color-z relation when both populations have the same magnitude limit.  Also show that this technique allows the inference of z distributions for a population fainter than the one of reference and give an estimate of the color-z mapping in this case.  This last point is of great interest for future large z surveys which suffer from the need of a complete faint spectroscopic sample.  


1505.05700
Cluster-lensing: a python package for galaxy clusters & miscentering
Ford, VanderPlas

Describe a new open scoured package for calculating properties of galaxy clusters, including NFW halo profiles with and without the effects of cluster miscentering.  This pure-Python package, cluster-lensing, provides well-documented and easy-to-use classes and functions for calculating cluster scaling relations, including mass-richness and mass-concentration relations from the literature, as well as the surface mass density Sigma(R) and different surface mass density DeltaSigma(R) profiles, probed by WL magnification and shear.  Galaxy cluster miscentering is especially a concern for stacked WL shear studies of galaxy clusters, where offsets between the assumed and the true underlying matter distribution can lead to a significant bias in the mass estimates if not accounted for.  This software has been developed and released in GitHub, and is licensed under the permissive MIT license.  The cluster-leninsg package is archived on Zenodo (Ford 2016).  Full documentation, source code, and installation instructions are available at http://jesford.github.io/cluster-lensing/.

Day 1097

Wednesday.

1605.04910
Doubling strong lensing as a cosmological probe
Linder

SL provides a geometric probe of cosmology in a unique manner through distance ratios involving the source and lens.  This is well known for the time delay distance derived from measured delays between light curves of the images of variable sources such as quasars.  Recently, double source plane lens systems involving two constant sources lensed by the same foreground lens have been proposed as another probe, involving a different ratio of distances measured from the image positions and fairly insensitive to the lens modeling.  Here, demonstrate that these two different sets of SL distance ratios have strong complementarity in cosmo leverage.  Unlike other probes, the double source distance ratio is actually more sensitive to the DE EoS parameters w_0 and w_a than to the matter density Omega_m, for low redshift lenses.  Adding double source distance ratio measurements can improve the DE FoM by 40% for a sample of fewer than 100 low z systems, or even better for the optimal z distribution derived.


1605.05088
An empirical model to form an evolve galaxies in dark matter haloes
Li et al

Based on SFH of galaxies in haloes of different masses, develop an empirical model to grow galaxies in DM haloes.  This model has very few ingredients, any of which can be associated to observational data and thus be efficiently assessed.  By applying this model to a very high resolution cosmo N-body sim, predict a number of galaxy properties that are a very good match to relevant observational data.  Namely, for both centrals and satellites, the galaxy stellar mass function (SMF) up to z~4 and the conditional stellar mass functions (CSMF) in the local universe are in good agreement with observations.  In addition, the 2pt correlation is well predicted in the different stellar mass ranges explored by the model.  Furthermore, after applying stellar population synthesis models to the stellar composition as a function of z, find that the luminosity functions in 0.1u, 0.1g, 0.1r, 0.1i and 0.1z bands agree quite well wit the SDSS observational results down to an absolute magnitude at about -17.0.  The SDSS conditional luminosity functions (CLF) itself is predicted well.  Finally, the cold gas is derived from the SFR to predict the HI gas mass within each mock galaxy.  Find a remarkable good match to observed HI-to-stellar mass ratios.  These features ensure that such galaxy/gas catalogs can be used to generate reliable mock redshift surveys.


1605.05286
Testing the spherical evolution of cosmic voids
Demochenko, Kai, Heymans, Peacock

Study the spherical evolution model for voids in LCDM, where the evolution of voids is governed by DE at an earlier time than that for the whole universe or in overdensities.  Show that the presence of DE suppresses the growth of peculiar velocities, causing void shell-crossing to occur at progressively later epochs as Omega_Lambda increases.  Apply the spherical model to evolve the initial conditions of N-body simulated voids and compare the resulting final void profiles.  Find that the model is successful in tracking the evolution of voids with radii greater than 30 Mpc/h, implying that void profiles could be used to constrain DE.  Find the the initial peculiar velocities of voids play a significant role in shaping their evolution.  Excluding the peculiar velocity in the evolution model delays the time of shell crossing.

Day 1096

Tuesday.

1605.04307
What does the Bullet Cluster tell us about self-interacting dark matter?
Robertson, Massey, Eke

Perform numerical sim of the merging Bullet Cluster, including the effects of elastic DM scattering.  In a similar manner to the stripping of gas by ram pressure, DM self-interactions would transfer momentum between the two galaxy cluster DM haloes, causing them to lag behind the collisionless galaxies.  The absence of an observed separation between the dark matter and stellar components in the Bullet cluster has been used to place upper limits on the cross-section for DM scattering.  Emphasize the importance of analyzing simulations in an observationally-motivated matter, finding that the way in which the positions of the various components are measured can have a larger impact on derived constraints on DM's self-interaction cross-section than reasonable changes to the initial conditions for the merger.  In particular, find that the methods used in previous studies to place some of the tightest constraints on the cross-section do not reflect what is done observationally, and overstate the Bullet Cluster's ability to constrain the particle properties of DM.  Introduce the first simulations of the Bullet Cluster including both self-interacting DM and gas.  Find that as the gas is stripped it introduces radially-dependent asymmetries into the stellar and DM distributions.  As the techniques used to determine the positions of the DM and galaxies are sensitive to different radial scales, these asymmetries can lead to erroneously measured offsets between DM and galaxies even when they are spatial coincident.


1605.04309
The PCA Lens-Finder: application to CFHTLS
Paraficz, Courbin, et al

Present the realists of a new search for galaxy-scale SL systems in CFHTLS wide.  The lens-finding technique involves a preselection of potential lens galaxies, applying simple cuts in size and magnitude.  Then perform a PCA of the galaxy images, ensuring a clean removal of the light profile.  Lensed features are searched for in the residual images using the clustering topometric algorithm DBSCAN.  Find 1098 lens candidates that are visually inspected, leading to a cleaned sample of 109 new lens candidates.  Using realistic image simulations, estimate the completeness of the sample and show that it is independent of source surface brightness, Einstein ring size (image separation) or lens redshift.  Compare the properties of the sample to previous lens searches in CFHTLS.  Including the present search, the total number of lenses found int CFHTLS amounts to 678, which corresponds to ~4 lenses per square degree down to i=24.8.  This is equivalent to ~60,000 lenses in total in a survey as wide as Euclid, but at the CFHTLS resolution and depth.


1605.04319
A look to the inside of haloes: a characterization of the halo shape as a function of overdensity in the Planck cosmology
Despali, Giocoli, et al

From simulation, discuss how halo triaxiality increases with (i) mass, (ii) redshift and (iii) overdensity.  Also examine how the orientation of the different ellipsoidal shells are aligned with each other and what is the gradient in internal shapes for haloes with different viral configurations.  Findings highlight that the internal part of the halo retains memory of the violent formation process keeping the major axis oriented toward the preferential direction of the infalling material while the outer part becomes rounder due to continuous isotropic merging events; this effect is clearly evident in high mass haloes - which formed recently - while it is more blurred in low mass haloes.  Present simple distributions that may be used as priors for various mass reconstruction algorithms, operating in different wavelengths, in order to recover a more complex and realistic DM distribution of isolated and relaxed systems.


1605.04357
The rise of the first stars: supersonic streaming, radiative feedback, and 21-cm cosmology
Barkana

Since the universe was filled with H atoms at early times, the most promising probe of the epoch of the first stars is the prominent 21-cm spectral line of H.  Current observational efforts are focus on the cosmic reionization era, but observations of the pre-reioniation cosmic down are also promising.  While observationally unexplored, theoretical studies predict a rich variety of observational signatures from cosmic dawn.  As the first stars formed, their radiation (plus that from stellar remnants) produced significant cosmic events including Lyman-alpha coupling at z~25, and early X-ray heating.  Much focus has gone to studying the angle-averaged power spectrum of 21-cm fluctuations.  Additional probes include the global (sky-averaged) 21-cm spectrum, and the LOS anisotropy of the 21-cm power spectrum.  A particularly striking signature may result from the recently recognized effect of a supersonic relative velocity between the DM and gas.  Work in this field, focused on understanding the whole era of reionization and cosmic dawn with analytical models and numerical simulations, is likely to grow in intensity and importance, as the theoretical predictions are finally expected to confront 21-cm observations  the coming years.

Day 1095

Monday.

1605.03982
Cosmic voids and void lensing in the dark energy survey science verification data
Sánchez, Clampitt, et al

Galaxies and their DM haloes populate a complicated filamentary network around large, nearly empty regions known as cosmic voids.  Cosmic voids are usually identified in spectroscopic galaxy surveys, where 3d information lounged the LS structure of the universe is available.  Although an increasing amount of photometric data is bing produced, its potential for void studies is limited since photo-z's induce LoS poisson errors of ~50 Mpc/h or more that can render many voids undetectable.  In this paper, present a new void finder designed for photometric surveys, validate it using simulations, and apply it to the high-quality photo-z redMaGiC galaxy sample of the DES SV data.  The algorithm works by projecting galaxies into 2d slices and finding voids in the smoothed 2d galaxy density field of the slice.  Fixing the LoS size of the slices to be at least twice the photo-z scatter, the number of voids found in these projected slices of simulated spectroscopic and photometric galaxy catalogs is within 20% for all transverse void sizes, and indistinguishable for the largest voids of radius ~70 Mpc/h and larger.  The positions, radii and projected galaxy profiles of photometric voids also accurately match the spectroscopic void sample.  Applying the algorithm to the DES-SV data in the redshift range 0.2<z<0.8, identify 87 voids with comoving radii spanning the range 18-120 Mpc/h, and carry out a stacked WL measurement.  With a significance of 4.4sigma, the lensing measurement confirms the voids are truly underdense in the matter field and hence not a product of Poisson noise, tracer density effects or systematics in the data.  It also demonstrates, for the first time in real data, the viability of void lensing studies in photometric surveys.

Day 1094

Friday.

1605.03574
Identifying true satellites of the Magellanic Clouds
Sales, Navarro, Kallivayalil, Frenk

The hierarchical nature of LCDM suggests that the Magellanic Clouds must have been surrounded by a number of satellites before their infall into the MW.  Many of those satellite should still be in close proximity to the Clouds, but some could have dispersed ahead/behind the Clouds along their Galactic orbit.  Either way, prior association with the Clouds results in strong restrictions on the present-day positions and velocities of candidate Magellanic satellites: they must lie close to the nearly-polar orbital plane of the Magellanic stream, and their distances and radial velocities must follow the latitude dependence expected for a tidal stream with the Clouds at pericenter.  Use a cosmo numerical sim of the disruption of massive sub halo in a MW-sized LCDM halo to test whether any of the 20 dwarfs recently-discovered in the DES, SMASH, Pan-STARRS, and ATLAS surveys are truly associated with the Clouds.  Of the 6 systems with kinematic data, only Hydra II and Hor 1 have distances and radial velocities consistent with a Magellanic origin.  Of the remaining dwarfs, six (Hor2, Eri3, Ret3, Tuc4, Tuc6, and Phx2) have positions and distances consistent with a Magellanic origin, but kinematic data are needed to substantiate that possibility.  Conclusive evidence for association would require proper motions to constrain the orbital angular momentum direction, which, for true Magellanic satellites, must coincide with that of the Clouds.  Use this result to predict radial velocities and proper motions for all new dwarfs.  The results are relatively insensitive to the assumption of first or second pericenter for the Clouds.

Day 1093

Tuesday.  Wednesday.  Thursday.

1605.03182
Effects of local environment and stellar mass on galaxy quenching out to z~3
Darvish et al

Study the effects of local environment and stellar mass on galaxy properties using a mass complete sample of quiescent and SF systems in the COSMOS field at z<~3.  Show that at z<~1, the median SFR and sSFR of all galaxies depend on environment, and but they become independent of environment at z>~1.  However, find that only for star-forming galaxies, the median SFR and sSFR are similar in different environments, regardless of redshift and stellar mass.  Find that the quiescent fraction depends on environment at z<~1, and on stellar mass out to z~3.  Show that at z<1, galaxies become quiescent faster in denser environments and that the overall environmental quenching efficiency increases with cosmic time.  Environmental and mass quenching processes depend on each other.  At z<1, denser environments more efficiently quench galaxies with higher masses (log(M/Msun)>10.7), possibly due to a higher merger rate of massive galaxies in denser environments, and that mass quenching is more efficient in denser regions.  Show that the overall mass quenching efficiency for more massive galaxies (log(M/Msun)>10.2) rises with cosmic time until z~1 and flattens out since then.  However, for less massive galaxies, the rise in mass quenching efficiency continues to the present time.  The results suggest that environmental quenching is only relevant at z<1, likely a fast process, whereas mass quenching is the dominant mechanism at z>1, with a possible stellar feedback physics.


1605.03201
Stellar classification from single-band imaging using machine learning
Kuntzer, Tewes, Courbin

Information on the spectral types of stars is of great interest in view of the exploitation of space-based imaging surveys.  In this article, investigate the classification of stars into spectral types using only the shape of their diffraction pattern in a single broadband image.  Propose a supervised machine learning approach to this endeavor, based on PCA for dimensionality reduction, followed by ANNs estimating the spectral type.  The analysis is performed with imagine simulations mimicking the HST ACS in the F606W and F814W bands, as well as the Euclid VIS imager.  First demonstrate this classification in a simple context, assuming perfect knowledge of the PSF model and the possibility of accurately generating mock training data for the machine learning.  Then analyse its performance in a fully data-driven situation, in which the training would be performed with a limited subset of bright stars from a survey, and an unknown PSF with spatial variations across the detector.  Use simulations of MS stars with flat distributions in spectral type and in S/N ratio, and classify these stars into 13 spectral subclasses, from O5 to M5.  Under these conditions, the algorithm achieves a high success rate both for Euclid and HST images, with typical errors of half a spectral class.  Although more detailed simulations would be needed to assess the performance of the algorithm on a specific survey, this shows that stellar classification from single-band images is well possible.

Day 1092

Monday.

1605.01728
Alignments between galaxies, satellite systems and haloes
Shao et al

The spatial distribution of the satellite populations of the MW and Andromeda are puzzling in that they are nearly perpendicular to the disks of their central galaxies.  To understand the origin of such configurations, study the alignment of the central galaxy, satellite system and DM halo in the largest of the EAGLE simulation.  Find that centrals and their satellite systems tend to be well aligned with their haloes, with a median misalignment angle of 33deg in both cases.  While the centrals are better aligned with the inner 10 kpc halo, the satellite systems are better aligned with the entire halo indicating that satellites preferentially trace the outer halo.  The central - satellite alignment is weak (median misalignment angle of 52 deg) and find that around 20% of systems have a misalignment angle larger than 78deg, which is the value for the MW.  The central - satellite alignment is a consequence of the tendency of both components to align with the DM halo.  As a consequence, when the central is parallel to the satellite system, it also tends to be parallel to the halo.  In contrast, if the central is perpendicular to the satellite system, as in the case of MW and Andromeda, then the central - halo alignment is much weaker.  Dispersion-Dominated (spheroidal) centrals have stronger alignment with both their halo and their satellite than rotation-dominated (disk) centrals.  Also find that the halo, the central galaxy and the satellite system tend to be aligned with the surrounding large-scale distribution of matter, with the halo being the better aligned of the three.


1605.02036
Testing the log normality of the galaxy and weak lensing convergence distributions from Dark Energy Survey maps
Clerking, et al

It is well known that the PDF of galaxy density contrast is approximately lognormal; whether the PDF of mass fluctuations derived from WL convergence (kappa_WL) is lognormal is less well established.  Derive PDFs of the galaxy and projected matter density distributions via the counts in cells (CiC) method.  Use maps of galaxies and WL convergence produced from DES SV data over 139 deg^2.  Test whether the underlying density contrast is well described by a a lognormal distribution of the galaxies, the convergence and their joint PDF.  Confirm that the galaxy density contrast distribution is well modeled by a lognormal PDF convolved with Poisson noise at angular scales from 10-40 arcmin (corresponding to physical scales of 3-10 Mpc).  Note that as kappa_WL is a weighted sum of the mass fluctuations along the LoS, its PDF is expected to be only approximately lognormal.  And that the kappa-WL distribution is well modeled by lognormal PDF convolved with Gaussian shape noise at scales between 10 and 20 arcmin, with a best-fit chi^2/DOF of 1.11 compared to 1.84 for a Gaussian model, corresponding to p-values 0.35 and 0.07 respectively, at a scale of 10 arcmin.  Above 20 arcmin a simple Gaussian model is sufficient.  The joint PDF is also reasonably fitted by a bivariate lognormal. As a consistency check, compare the variances derived from the lognormal modeling with those directly measured via CiC.  The methods are validated against maps from the MICE Grand Challenge N-body simulation.

Day 1091

Friday.


1605.01414
Wavelet reconstruction of E and B modes for CMB polarization and cosmic shear analyses
Listed, McEwen, Büttner, Peiris

Present new methods for mapping the curl-free (E-mode) and divergence-free (B-mode) components of spin 2 signals using spin directional wavelets.  The methods are equally applicable to measurements of the polarization of the CMB and the shear of galaxy shapes due to WL.  Derive pseudo and pure wavelet estimators, where E-B mixing arising due to incomplete sky coverage is suppressed in wavelet space using scale- and orientation-dependent masking and weighting schemes.  In the case of the pure estimator, ambiguous modes (which have vanishing curl and divergence simultaneously on the incomplete sky) are also cancelled.  On simulations, demonstrate the improvement (i.e., reduction in leakage) provided by the wavelet space estimators over standard harmonic space approaches.  The new methods can be directly interfaced in a coherent and computationally-efficient manner with component separation or feature extraction techniques that also exploit wavelets.


1605.01489
New lessons from the HI size-mass relation of galaxies
Wang, et al

Revisit the HI size-mass (D_HI-M_HI) relation of galaxies with a sample of >500 nearby galaxies covering over 5 orders of magnitude in HI mass and more than 10 B-band magnitudes.  The relation is remarkably tight with a scatter sigma~0.06 dex, or 14%.  The scatter does not change as a function of galaxy luminosity, HI richness or morphological type.  The relation is linked to the fact that dwarf and spiral galaxies have a homogeneous radial profile of HI surface density in the outer regions when the radius is normalized by D_HI.  The early-type disk galaxies typically have shallower HI radial profiles, indicating a different gas accretion history.  Argue that the process of atomic-to-molecular gas conversion of SF cannot explain the tightness of the D_HI-M_HI relation.  This simple relation puts strong constraints on simulation models for galaxy formation.

Day 1090

Wednesday.  Thursday.

1605.01056
Systematic tests for position-dependent additive shear bias
van Uitert, Schneider

Present new tests to identify stationary position-dependent additive shear biases in WL data sets.  These tests are important diagnostics for currently ongoing and planned cosmic shear surveys, as such biases induce coherent shear patterns that can mimic and potentially bias the cosmic shear signal.  The central idea of these tests is to determine the average ellipticity of all galaxies with shape measurements in a grid in the pixel plane.  The distribution of the absolute values of these averaged ellipticities can be compared to randomized catalogues; a difference points to systematics in the data.  In addition, introduce a method to quantify the spatial correlation of the additive bias, which suppresses the contribution from cosmic shear and therefore eases the identification of a position dependent additive shear bias in the data.  Apply these tests to the publicly available shear catalogues from CFHTLenS and KiDS and find evidence for a small but non-negligible residual additive bias at small scales.  As this residual bias is smaller than the error on the shear correlation signal at those scales, it is highly unlikely that it causes a significant bias in the published cosmic shear results of CFHTLenS.  In CFHTLenS, the amplitude of this systematic signal is consistent with zero in fields where the number of stars used to model the PSF is higher than average, suggesting that the position-dependent additive shear bias originates from under sampled PSF variations across the image.


1605.01065
Intrinsic alignments in redMaPPer clusters -- I. central galaxy alignments and angular segregation of satellites
Huang, Mandelbaum, et al

The shapes of cluster central galaxies are not randomly oriented, but rather exhibit coherent alignments with the shapes of their parent clusters as well as with large-scale structure.  In this work, undertake a comprehensive study of the alignments of central galaxies at low redshift.  Based on a sample of 8237 clusters and 94817 members in the redMaPPer cluster catalog with 0.1<z0.35, first quantify the alignment between the projected central galaxy shapes and the distribution of member satellites, to understand what central galaxy and cluster properties most strongly correlate with these alignments.  Next, investigate the angular segregation of satellites with respect to their central galaxy major axis directions, to identify the satellite properties that most strongly predict their angular segregation.  Find that central galaxies are more aligned with their member galaxy distributions in clusters that are more elongated and have higher richness, and for central galaxies with larger physical size, higher luminosity and centering probability, and redder color.  Satellites with redder color, higher luminosity, located closer to the central galaxy, and with smaller ellipticity show a stronger angular segregation toward their central galaxy major axes.  Finally, provide physical explanations for some of the identified correlations, and discuss the connection to theories of central galaxy alignments, the impact of primordial alignments with tidal fields, and the importance of anisotropic accretion.


1605.01100
Cosmology with photometric weak lensing surveys: constraints with redshift tomography of convergence peaks and moments
Petri, May, Haiman

WL is becoming a mature technique for constraining cosmo parameters, and future surveys will be able to constrain the DE EoS w.  When analyzing galaxy surveys, redshift information has proven to be a valuable addition to angular shear correlations.  Forecast parameter constraints on the triples (Omega_m, w, sigma8) for an LSST-like photometric galaxy survey, using tomography of the shear-shear power spectrum, convergence peak counts and higher convergence moments.  Find that redshift tomography with the power spectrum reduces the are of the 1 sigma confidence interval in (Omega_m, w) space by a factor of 8 with respect to the case of the single highest redshift bin.  Also find that doing non-Gaussian information from the peak counts and higher-order moments of the convergence field and its spatial derivatives further reduces the constrained area in (Omega_m, w) by a a factor of 3 and 4, respectively.  When CMB parameter priors from Planck are added to the analysis, tomography improves power spectrum constraints by a factor of 3.  Adding moments yields and improvement by an additional factor of 2, and adding both moments and peaks improves by almost a factor of 3, over power spectrum tomography alone.  Evaluate the effect of uncorrected systematic photometric redshift errors on the parameter constraints.  Find that different statistics lead to different bias directions in parameter space, suggesting the possibility of eliminating this bias via self-calibration.


1605.01306
The search for HI emission at z $\approx0.4$ in gravitationally lensed galaxies with the green back telescope
Hunt, Pisano, Edel

HI is difficult to detect at high z due to weak emission, limited sensitivity of modern instruments, and terrestrial radio frequency interference (RFI) at low frequencies.  Attempt to use GL to detect HI lie emission from 3 gravitationally lensed galaxies behind Abell 773, two at z of 0.398 and one at z=0.487, using the Green Bank Telescope.  Find a 3 sigma upper limit for a galaxy with rotation velocity of 200 km/s. [...]

Day 1089

Tuesday.

1604.07795
Consequences of CCD imperfections for cosmology determined by weak lensing surveys: from laboratory measurements to cosmological parameter bias
Okra, Petri, May, Plazas, Tamagawa

WL causes subtle changes in the apparent shapes of galaxies dues to the bending of light by the gravity of FG masses.  By measuring the shapes of large numbers of galaxies (millions own recent surveys, up to tens of billions in future surveys), can infer the parameters that determine cosmology.  Imperfections in the detectors used to record images of the sky can introduce changes in the apparent shape of galaxies, which in turn can bias the inferred cosmo parameters.  In this paper, consider the effect of two widely discussed sensor imperfections: tree-rings, due to impurity gradient which cause transverse E fields in the CCD, and pixel-size variation, due to periodic CCD fabrication errors.  These imperfections can be observed when the detectors are subject to uniform illumination (flat field images).  Develop methods to determine the spurious shear and convergence (due to the imperfections) from the flat-field images.  Calculate how the spurious shear when added to the lensing shear will bias the determination of cosmo parameters.  Apply the methods to candidate sensors of the LSST as a timely and important example, analyzing flat field images recorded with LSST prototype CCDs in the lab.  Find that tree rings and periodic pixel-size variation present in the LSST CCDs will introduce negligible bias to cosmological parameters determined from the lensing power spectrum, specifically, w, Omega_m and sigma8.


1604.08360
Constraints on LISA pathfinder's self-gravity: design requirements, estimates and testing procedures
Ferroni

LISA pathfinder satellite has been launched on 3rd December 2015 toward the Sun-Earth L1 point where the LISA Technology Package (LTP), which is the main scene payload, will be tested.  With its cutting-edge technology, the LTP will provide the ability to achieve unprecedented geodesic motion residual acceleration measurements down to the order of 3e-14 m/s^2/Hz^1/2 within the 1-30mHz frequency band.  The presence of the spacecraft itself is responsible of the local gravitational field which will interact with the two proof test-masses.  Potentially, such a force interaction might prevent to achieve the targeted free-fall level originating a significant source of noise.  Balance this gravitational force with sub nm/s^2 accuracy, guided by a protocol based on measurements of the position and the mass of all parts that constitute the satellite, via finite element calculation tool estimates.  In the following, introduce requirements, design and foreseen on-orbit testing procedures.


1605.00555
Testing LSST dither strategies for survey uniformity and large-scale structure systematics
Awan, Gawiser, et al

Analyze LSST survey depth for several geometric patterns of dithers (random, hexagonal lattice, spiral) with amplitude as large as the radius of the LSST field-of-view implemented on different timescales (per season, per night, per visit).  Results illustrate that per night and per visit dither assignments are more effective than per season.  Also find that some dither geometries (e.g. hexagonal lattice) are particularly sensitive to the timescale on which the dieters are implemented, while others like random dithers perform well on all timescales.  Then model the propagation of depth variations to artificial fluctuations in galaxy counts, which are a systematic for large-scale structure studies.  Calculate the bias in galaxy counts induced due to the observing strategy, accounting for photometric calibration uncertainties, dust extinction, and magnitude cuts; uncertainties in this bias limit the ability to account for structure induced by the survey strategy.  Find that after 10 years of the LSST survey, the best observing strategies lead to uncertainties in the bias smaller than the minimum statistical floor for a galaxy catalog as deep as r<27.5; of these, a few bring the uncertainties close to the floor for r<25.7 after only one year of survey.

Day 1088

Friday.  Monday.

1604.08594
Are some Milky Way globular clusters hosted by undiscovered galaxies?
Zaritsky, Crnojevic, Sand

For an empirically determined specific frequency of between 0.06 and 0.39 globular clusters (GCs) per 1e9 Msun of total mass, the surviving MWsubhloes with masses smaller than 1e10 Msun could host as many as 5 to 31 GCs, broadly consistent with the actual population of outer halo MW GCs, although matching the radial distribution in detail remains a challenge.  Find that about 90% of these GCs lie in lower-mass sub haloes than that of Eri II.  From what is known about the stellar mass-halo mass function, the sub halo mass function, and the mass normalized GC specific frequency, conclude that some of the MW's outer halo GCs are likely to be hosted by undetected suhalos with extremely modest stellar populations.